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1. Vortex‐Dominated Aeolian Activity at InSight's Landing Site, Part 1: Multi‐Instrument Observations, Analysis, and Implications

Author

Alexander E. Stott, L. M. Sotomayor, Constantinos Charalambous, John A. Grant, Sebastien Rodriguez, Nicholas H. Warner, Veronique Ansan, Don Banfield, William T. Pike, Naomi Murdoch, Aymeric Spiga, Maria E. Banks, Daniel Viúdez-Moreiras, William B. Banerdt, P. H. Lognonné, Ernst Hauber, Jorge Pla-Garcia, Matthew P. Golombek, Clément Perrin, Ralph D. Lorenz, Justin N. Maki, T. Warren, Anna Mittelholz, Claire E. Newman, Antoine Lucas, Matthew E. Baker, Catherine L. Johnson, J. B. Garvin, Ingrid Daubar, Mark T. Lemmon, Sara Navarro, Catherine M. Weitz, J. B. McClean, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Department of Electrical and Electronic Engineering [London] (DEEE), Imperial College London, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Johns Hopkins University (JHU), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Space Science Institute [Boulder] (SSI), Laboratoire de Planétologie et Géosciences [UMR_C 6112] (LPG), Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), Institut de Physique du Globe de Paris (IPG Paris), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), NASA Goddard Space Flight Center (GSFC), Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-SUPAERO), Planetary Science Institute [Tucson] (PSI), Smithsonian Institution, State University of New York at Geneseo (SUNY Geneseo), State University of New York (SUNY), Brown University, German Aerospace Center (DLR), University of British Columbia (UBC), Institute of Geophysics [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), University of Oxford, Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Cornell University [New York], Aeolis Research, ANR-19-CE31-0008,MAGIS,MArs Geophysical InSight(2019), Rodriguez, Sébastien, and MArs Geophysical InSight - - MAGIS2019 - ANR-19-CE31-0008 - AAPG2019 - VALID

Subjects
Convection, Seismometer, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars, 01 natural sciences, Wind speed, Physics::Geophysics, aeolian changes at the InSight landing site on Mars, convective vortices as a primary driver of particle motion, dust lifting and saltation, multi-instrument measurements constrain the timing and atmospheric conditions of aeolian changes, passing vortices lifting dust are correlated with magnetic signatures, surface creep, surface tracks, particle transport, Geochemistry and Petrology, Planet, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), wind, 14. Life underwater, 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, InSight, 0105 earth and related environmental sciences, Mars landing, Mars Exploration Program, Geophysics, Vortex, Planetengeologie, [PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 13. Climate action, Space and Planetary Science, Aeolian processes, Astrophysics::Earth and Planetary Astrophysics, Geology, camera
Abstract

International audience; We report the aeolian changes observed in situ by NASA's InSight lander during the first 400 sols of operations: Granule creep, saltation, dust removal, and the formation of dark surface tracks. Aeolian changes are infrequent and sporadic. However, on sols, when they do occur, they consistently appear between noon to 3 p.m., and are associated with the passage of convective vortices during periods of high vortex activity. Aeolian changes are more frequent at elevated locations, such as the top surfaces of rocks and lander footpads. InSight observed these changes using, for the first time, simultaneous insitu and orbital imaging and high-frequency meteorological, seismological, and magnetic measurements. Seismometer measurements of ground acceleration constrain the timing and trajectory of convective vortex encounters, linking surface changes to source vortices. Magnetometer measurements show perturbations in magnetic field strength during the passage of convective vortices consistent with chargedparticle motion. Detachment of sand-scale particles occurs when high background winds and vortexinduced turbulence provide a peak surface friction wind speed above the classic saltation fluid threshold. However, detachment of dust-and granule-scale particles also occurred when the surface friction wind speed remained below this threshold. This may be explained by local enhancement of the surface roughness and other effects described here and further studied in Part 2 (Baker et al., 2021). The lack of saltation and bright dust-coated surfaces at the InSight landing site implies surface stability and the onset of particle motion may be suppressed by dust "cushioning." This differentiates the InSight landing site from other areas on Mars that exhibit more aeolian activity. Plain Language Summary Aeolian activity, the movement of dust and sand by the wind, is common on Earth and has been observed on other planets, including Mars. A new Mars lander, InSight, has for the first time monitored aeolian changes by combining imaging with weather, seismic and CHARALAMBOUS ET AL.

Published
2021
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2. Dynamic Response of Ionospheric Plasma Density to the Geomagnetic Storm of 22‐23 June 2015

Author

Geoff Crowley, Endawoke Yizengaw, Victoria N. Coffey, John‐Bosco Habarulema, O. F. Jonah, Andrew Gisler, Chigomezyo M. Ngwira, Elvira Astafyeva, NASA Goddard Space Flight Center (GSFC), Catholic University of America, South African National Space Agency (SANSA), Rhodes University, Grahamstown, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), NASA Marshall Space Flight Center (MSFC), and National Aeronautics & Space Administration (NASA) United States Department of DefenseAir Force Office of Scientific Research (AFOSR) NSF CEDAR Grant AGS-1651268National Research Foundation - South Africa112090NASA LWS grant NNX15AB83GNational Science Foundation (NSF)

Subjects
Geomagnetic storm, 010504 meteorology & atmospheric sciences, Total electron content, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], TEC, total electron content, traveling ionospheric disturbances, Magnetosphere, Storm, Atmospheric sciences, 01 natural sciences, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], ionospheric storms, penetration electric fields, Geophysics, 13. Climate action, Space and Planetary Science, Dynamo theory, Ionosphere, Interplanetary spaceflight, and neutral winds, Geology, high-latitude injection, 0105 earth and related environmental sciences
Abstract

International audience; On 21-22 June 2015, three consecutive interplanetary shocks slammed into the Earth's magnetosphere. Immediately after the third shock at 18:36 UT on 22 June, marked by an exceptional sudden storm commencement with an amplitude of Delta SYM-H = similar to 106 nT, a major geomagnetic storm commenced. In the present study, a multi-instrument approach comprising observations, data analysis, and modeling is used to examine the global ionospheric response. Results show that enhanced storm time processes produced major total electron content (TEC) variations at different latitudes, longitudes, and phases of the storm. A closer inspection of the TEC observations reveals strong longitudinal and hemispherical asymmetry. In addition, multiple equatorward and poleward propagating traveling ionospheric disturbances (TIDs) were detected in the TEC data. Equatorward propagating TIDs are consistent with vertical neutral winds simulated from Thermosphere-Ionosphere-Electrodynamics General Circulation Model; however, poleward TIDs were not reproduced in the model. We find that a combination of driving processes including enhanced high-latitude injection, prompt penetration electric fields, disturbance dynamo effect, neutral winds, and composition changes were acting at different stages of the storm

Published
2019
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3. Author Correction: In situ recording of Mars soundscape

Author

Maurice, S., Chide, B., Murdoch, N., Lorenz, R, Mimoun, D., Wiens, R., Stott, A., Jacob, X., Bertrand, T., Montmessin, Franck, Lanza, N, Alvarez-Llamas, C., Angel, S, Aung, M., Balaram, J., Beyssac, O., Cousin, A., Delory, G., Forni, O., Fouchet, T., Gasnault, O., Grip, H., Hecht, M., Hoffman, J., Laserna, J., Lasue, Jérémie, Maki, J., Mcclean, J., Meslin, P.-Y., Le Mouélic, S., Munguira, A., Newman, C., Rodríguez Manfredi, J., Moros, J., Ollila, A., Pilleri, P., Schröder, S., de La Torre Juárez, M., Tzanetos, T., Stack, K., Farley, K., Williford, K., Acosta-Maeda, T., Anderson, R., Applin, D., Arana, G., Bassas-Portus, M., Beal, R., Beck, P., Benzerara, K., Bernard, S., Bernardi, P., Bosak, T., Bousquet, B., Brown, A., Cadu, A., Caïs, P., Castro, K., Clavé, E., Clegg, S, Cloutis, E., Connell, S., Debus, A., Dehouck, E., Delapp, D., Donny, C., Dorresoundiram, A., Dromart, G., Dubois, B., Fabre, C., Fau, A., Fischer, W., Francis, R., Frydenvang, J., Gabriel, T., Gibbons, E., Gontijo, I., Johnson, J., Kalucha, H., Kelly, E., Knutsen, Elise Wright, Lacombe, Gaetan, Legett, C., Leveille, R., Lewin, E., Lopez-Reyes, G., Lorigny, E., Madariaga, J., Madsen, M., Madsen, S., Mandon, L., Mangold, N., Mann, M., Manrique, J.-A., Martinez-Frias, J., Mayhew, L., Mcconnochie, T., Mclennan, S., Melikechi, N., Meunier, F., Montagnac, G., Mousset, V., Nelson, T., Newell, R, Parot, Y., Pilorget, C., Pinet, P., Pont, G., Poulet, F., Quantin-Nataf, C., Quertier, B., Rapin, W., Reyes-Newell, A., Robinson, S., Rochas, L., Royer, C., Rull, F., Sautter, V., Sharma, S., Shridar, V., Sournac, A., Toplis, M., Torre-Fdez, I., Turenne, N., Udry, A., Veneranda, M., Venhaus, D., Vogt, D., Willis, P., Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Los Alamos National Laboratory (LANL), Institut Supérieur de l'Aéronautique et de l'Espace (ISAE-SUPAERO), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Department of Earth, Atmospheric, and Planetary Sciences [West Lafayette] (EAPS), Purdue University [West Lafayette], Institut de mécanique des fluides de Toulouse (IMFT), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Universidad de Málaga [Málaga] = University of Málaga [Málaga], Department of Chemistry and Biochemistry [Columbia, South Carolina], University of South Carolina [Columbia], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Heliospace Corporation, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Department of Aeronautics and Astronautics [Cambridge], Laboratoire de Planétologie et Géosciences [UMR_C 6112] (LPG), Université d'Angers (UA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Nantes université - UFR des Sciences et des Techniques (Nantes univ - UFR ST), Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Sciences et technologie, Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ), Escuela de Ingeniería de Bilbao, Universidad del Pais Vasco / Euskal Herriko Unibertsitatea [Espagne] (UPV/EHU), Aeolis Corporation, Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), DLR Institute of Optical Sensor Systems, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Blue Marble Space Institute of Science (BMSIS), University of Hawai‘i [Mānoa] (UHM), US Geological Survey [Flagstaff], United States Geological Survey [Reston] (USGS), University of Winnipeg, University of the Basque Country/Euskal Herriko Unibertsitatea (UPV/EHU), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Centre d'Etudes Lasers Intenses et Applications (CELIA), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Plancius Research LLC, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, Université de Lyon, GeoRessources, Institut national des sciences de l'Univers (INSU - CNRS)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), University of Copenhagen = Københavns Universitet (UCPH), McGill University = Université McGill [Montréal, Canada], Universidad de Valladolid [Valladolid] (UVa), IT University of Copenhagen (ITU), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Department of Geological Sciences [Boulder], University of Colorado [Boulder], University of Maryland [College Park], University of Maryland System, Stony Brook University [SUNY] (SBU), State University of New York (SUNY), Department of Physics and Applied Physics [Lowell], University of Massachusetts [Lowell] (UMass Lowell), University of Massachusetts System (UMASS)-University of Massachusetts System (UMASS), Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), University of Nevada [Las Vegas] (WGU Nevada), and NASA’s Mars Exploration ProgramCNES

Subjects
Multidisciplinary, Carbon dioxide, Modélisation, [SDU]Sciences of the Universe [physics], Atmospheric Turbulence, Atmospheric Sound, Microphone, Mars, Attenuation, CO2, Perseverance, Acoustic Environment
Abstract

International audience

Published
2022
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4. Multistatic Specular Meteor Radar Network in Peru: System Description and Initial Results

Author

N. Pfeffer, M. Clahsen, Brian J. Harding, Marco Milla, Philip J. Erickson, K. Kuyeng, Jorge L. Chau, Juha Vierinen, Juan Miguel Urco, Urco, J. M., 1 Leibniz Institute of Atmospheric Physics at the University of Rostock Kühlungsborn Germany, Vierinen, J., 3 The Arctic University of Norway Tromso Norway, Harding, B. J., 4 Space Sciences Laboratory University of California, Berkeley Berkeley CA USA, Clahsen, M., Pfeffer, N., Kuyeng, K. M., 5 Radio Observatorio de Jicamarca Instituto Geosfísico del Perú Lima Peru, Milla, M. A., Erickson, P. J., and 6 MIT Haystack Observatory Westford MA USA

Subjects
Low latitude mesosphere, 010504 meteorology & atmospheric sciences, Astronomy, ionosphere, QB1-991, multistatic radar observations, Environmental Science (miscellaneous), vertical velocity, 010502 geochemistry & geophysics, 01 natural sciences, Physics::Geophysics, Physics::Fluid Dynamics, Multistatic radar observations, low latitude mesosphere, MLT horizontal divergence, Peru, mesosphere, Specular reflection, Vertical velocity, MLT dynamics, network analysis, 551.5, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, thermosphere, purl.org/pe-repo/ocde/ford#1.05.01 [https], QE1-996.5, Turbulence, Gravitational wave, VDP::Technology: 500, Geology, Geophysics, Meteor radar, VDP::Teknologi: 500, Computer Science::Computer Vision and Pattern Recognition, Physics::Space Physics, General Earth and Planetary Sciences, Astrophysics::Earth and Planetary Astrophysics, Thermosphere, MLT vorticity, radar
Abstract

The mesosphere and lower thermosphere (MLT) region is dominated globally by dynamics at various scales: planetary waves, tides, gravity waves, and stratified turbulence. The latter two can coexist and be significant at horizontal scales less than 500 km, scales that are difficult to measure. This study presents a recently deployed multistatic specular meteor radar system, SIMONe Peru, which can be used to observe these scales. The radars are positioned at and around the Jicamarca Radio Observatory, which is located at the magnetic equator. Besides presenting preliminary results of typically reported large‐scale features, like the dominant diurnal tide at low latitudes, we show results on selected days of spatially and temporally resolved winds obtained with two methods based on: (a) estimation of mean wind and their gradients (gradient method), and (b) an inverse theory with Tikhonov regularization (regularized wind field inversion method). The gradient method allows improved MLT vertical velocities and, for the first time, low‐latitude wind field parameters such as horizontal divergence and relative vorticity. The regularized wind field inversion method allows the estimation of spatial structure within the observed area and has the potential to outperform the gradient method, in particular when more detections are available or when fine adaptive tuning of the regularization factor is done. SIMONe Peru adds important information at low latitudes to currently scarce MLT continuous observing capabilities. Results contribute to studies of the MLT dynamics at different scales inherently connected to lower atmospheric forcing and E‐region dynamo related ionospheric variability., Plain Language Summary: The mesosphere and lower thermosphere (MLT) region is dominated by neutral wind dynamics with structure scales ranging from a few thousands of kilometers down to a few kilometers. In this work, we present a new state‐of‐the‐art ground‐based radar system using multistatic meteor scattering that allows tomographic studies of MLT wind dynamics at scales not possible before. Given the location of the radar network at the magnetic equator, its focus is on wind dynamics peculiar to equatorial latitudes. Two methods for estimating the mesospheric neutral wind field are used. One takes into account wind gradients in addition to mean wind (gradient method). The other estimates a spatially resolved wind vector field and uses an additional mathematical constraint that produces smooth wind field solutions (regularized wind field inversion method). Using the gradient method, the vertical wind estimate is improved. For the first time at MLT equatorial latitudes, parameters familiar to meteorologists, such as horizontal divergence and relative vorticity are obtained. Measurements from this new system have the potential to contribute to coupling studies of the atmosphere and the ionosphere at low latitudes., Key Points: Measurements of horizontal wind gradients at low‐latitude mesosphere and lower thermosphere altitudes. These gradients of the horizontal winds show strong temporal and altitude variability that are not observed at high latitudes. Improved vertical winds are obtained using a gradient wind field method inherently free from horizontal divergence contamination., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659, NSF, Directorate for Geosciences (GEO) http://dx.doi.org/10.13039/100000085

Published
2021

6. Strategic Plan of the IVS for the Period 2016-2025

Author

Nothnagel, Axel, Behrend, Dirk, Bertarini, Alessandra, Charlot, P., Combrinck, Ludwig, Gipson, John, Himwich, Ed, Haas, Rüdiger, Ipatov, Alexander, Kawabata, Ryoji, Lovell, Jim, Ma, Chopo, Niell, Arthur, Petrachenko, Bill, Schüler, Torben, Wang, Guangli, M2A 2016, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Haematology, Oncology and Clinical Immunology, University Hospital of Düsseldorf, Saint Petersburg State Technical University, Saint Petersburg State Polytechnical University (SPSPU), Harbin Engineering University (HRBEU), MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Geodetic Survey Division, Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Université Paris Diderot - Paris 7 (UPD7), and Pomies, Marie-Paule

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; Over the next decade, the IVS is on the cusp of dramatic changes transitioning from using large, slow moving antennas observing at S/X (``legacy'' systems) to using small, fast antennas with broad-band receivers, the so-called VGOS systems. Never has there been a time when so many antennas specifically designed for geodetic VLBI are scheduled to come on line in such a short period. VGOS observing will change all aspects of VLBI, from scheduling, to correlation, to observing strategy, to analysis. Compared to current observing, a typical VGOS session will have 1-2 orders of magnitude more data. In this strategic plan we outline some of the operational concepts of VGOS observing, our goals for data accuracy and latency, and some of the challenges and issues we will face during this transition.

Published
2016

7. IVS Observation of ICRF2-Gaia Transfer Sources

Author

K. Le Bail, Geraldine Bourda, A. Collioud, Brian E. Corey, W. E. Himwich, Michael Titus, Patrick Charlot, Dan MacMillan, John Gipson, Cynthia C. Thomas, David Gordon, Dirk Behrend, Karen Baver, S. Bolotin, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), M2A 2016, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, media_common.quotation_subject, Real-time computing, X band, 01 natural sciences, quasars: general, 0103 physical sciences, Very-long-baseline interferometry, reference systems, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, media_common, Remote sensing, Physics, Astronomy and Astrophysics, Astrometry, Monitoring program, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 13. Climate action, Space and Planetary Science, Sky, techniques: interferometric, International Celestial Reference Frame, astrometry, S band, catalogs, Reference frame
Abstract

International audience; The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency’s Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ∼500,000 Quasi Stellar Objects in the optical domain an average of 70 times each during the five years of the mission. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d’Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. We describe our successful effort to implement such a program and report on the results. Most observations of the ICRF2-Gaia transfer sources now occur automatically as part of the IVS source monitoring program, while a subset of 37 sources requires special attention. Beginning in 2013, we scheduled 25 VLBI sessions devoted in whole or in part to measuring these 37 sources. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Of the sources, 87 met their observing target of 12 successful sessions per year. The position uncertainties of all of the ICRF2-Gaia transfer sources have improved since the start of this observing program. For a subset of 24 sources whose positions were very poorly known, the uncertainty has decreased, on average, by a factor of four. This observing program is successful because the two main goals were reached for most of the 195 ICRF2-Gaia transfer sources: observing at the requested target of 12 successful sessions per year and improving the position uncertainties to better than 200 μas for both R.A. and decl. However, scheduling some of the transfer sources remains a challenge because of network geometry and the weakness of the sources, and this will be one focus of future sessions used in this ongoing program.

Published
2016
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8. The Electric Field and Waves Instruments on the Radiation Belt Storm Probes Mission

Author

Vladimir Krasnoselskikh, Greg Dalton, W. Rachelson, Robert J. Strangeway, Stuart D. Bale, C. Shultz, Cynthia A Cattell, J. Fischer, D. M. Malsapina, John C. Foster, Ian R. Mann, Xinlin Li, D. Gordon, Jay M. Albert, S. Heavner, Peter Berg, R. Hochmann, Eric Donovan, A. Brenneman, J. McCauley, C. C. Chaston, Peter Harvey, Paul Turin, Michael Ludlam, F. S. Mozer, Kris Kersten, M. Bolton, Mary K. Hudson, B. Donakowski, John R. Wygant, Keith Goetz, M. Diaz-Aguado, Daniel N. Baker, Robert E. Ergun, Christopher Cully, J. B. Tao, K. Harps, John W. Bonnell, Christopher D. Smith, School of Physics and Astronomy [Minneapolis], University of Minnesota [Twin Cities] (UMN), University of Minnesota System-University of Minnesota System, Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Blackett Laboratory, Imperial College London, Department of Physics and Astronomy [Newark], University of Delaware [Newark], Institute of Geophysics and Planetary Physics [Los Angeles] (IGPP), University of California [Los Angeles] (UCLA), Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Department of Physics [Edmonton], University of Alberta, Department of Physics and Astronomy [Calgary], University of Calgary, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Haystack Observatory, and Foster, John C.

Subjects
Physics, Electric fields, 010504 meteorology & atmospheric sciences, Spacecraft, business.industry, Acoustics, Magnetosphere, Astronomy and Astrophysics, Optical field, 01 natural sciences, Magnetic field, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], symbols.namesake, Nuclear magnetic resonance, Space and Planetary Science, Electric field, Van Allen radiation belt, 0103 physical sciences, symbols, Van Allen Probes, business, 010303 astronomy & astrophysics, Burst mode (computing), 0105 earth and related environmental sciences
Abstract

The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ∼15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the “highest quality” events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013)., United States. National Aeronautics and Space Administration (Contract NAS5-01072), Johns Hopkins University. Applied Physics Laboratory (Radiation Storm Belt Probes ECT Contract 967399), Johns Hopkins University. Applied Physics Laboratory (Radiation Storm Belt Probes EFW Contract 922613)

Published
2013
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9. Introduction to the fifth Mars Polar Science special issue: Key questions, needed observations, and recommended investigations

Author

Pete Smith, William B. Durham, Leslie K. Tamppari, Richard W. Zurek, François Forget, Stephen M. Clifford, David A. Fisher, Shane Byrne, Michael H. Hecht, Kenji Yoshikawa, Timothy N. Titus, Lunar and Planetary Institute [Houston] (LPI), University of Alaska [Fairbanks] (UAF), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), University of Ottawa, Dept. of Geology, Marion Hall, Ottawa , ON, Canada, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), MIT Haystack Observatory, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), US Geological Survey [Flagstaff], United States Geological Survey [Reston] (USGS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Mars Exploration Program, Atmosphere of Mars, Mars surface, 01 natural sciences, Astrobiology, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, Space and Planetary Science, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, 0103 physical sciences, Key (cryptography), [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, 010303 astronomy & astrophysics, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience

Published
2013
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10. Recent Progress in the VLBI2010 Development

Author

Behrend, J., Boehm, J., Charlot, P., Clark, T., Corey, B., Gipson, J., Haas, R., Koyama, Y., MacMillan, D., Malkin, Z., Niell, A., Nilsson, T., Petrachenko, B., Rogers, A., Tuccari, G., Wresnik, J., Max-Planck-Institut für Radioastronomie (MPIFR), NVI, Inc., NASA Goddard Space Flight Center (GSFC), institut de geodesie et geophysique de Vienne (INSTITUT DE GEODESIE ET GEOPHYSIQUE), Institut de geodesie et geophysique, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Kashima Space Technology Center, National Institute of Information and Communications Technology [Tokyo, Japan] (NICT), Pulkovo Observatory, Geodetic Survey Division, Istituto di Radioastronomia di Noto, and Istituto Nazionale di Astrofisica (INAF)

Subjects
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], next generation VLBI2010, IVS, geodetic VLBI, Monte Carlo simulations
Abstract

chapter in book series "International Association of Geodesy Symposia" book "Observing our Changing Earth" ISBN 978-3-540-85425-8; International audience; From October 2003 to September 2005, the International VLBI Service for Geodesy and Astrometry (IVS) examined current and future requirements for geodetic VLBI, including all components from antennas to analysis. IVS Working Group 3 ‘VLBI 2010', which was tasked with this effort, concluded with recommendations for a new generation of VLBI systems. These recommendations were based on the goals of achieving 1 mm measurement accuracy on global baselines, performing continuous measurements for time series of station positions and Earth orientation parameters, and reaching a turnaround time from measurement to initial geodetic results of less than 24 hours. To realize these recommendations and goals, along with the need for low cost of construction and operation, requires a complete examination of all aspects of geodetic VLBI including equipment, processes, and observational strategies. Hence, in October 2005, the IVS VLBI2010 Committee (V2C) commenced work on defining the VLBI2010 system specifications. In this paper we give a summary of the recent progress of the VLBI2010 project.

Published
2008
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11. A study of VLB 2010 potential for source structure corrections

Author

PETRACHENKO, W. T., CHARLOT, P., COLLIOUD, A., HOBIGER, T., NIELL, A., Geodetic Survey Division, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), MIT Haystack Observatory, and Massachusetts Institute of Technology (MIT)

Subjects
[PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

International audience; In October 2003, the International VLBI Service for Geodesy and Astrometry (IVS) in- stalled Working Group 3 ‘VLBI2010' to examine current and future requirements for geodetic/astrometric VLBI including all components from antennas to analysis, and to create recommendations for a new gen- eration of VLBI systems. Some important recommendations include: the use of larger networks; the use of smaller faster slewing antennas; the use of very high data rates; and, the use of multiple (e.g. 4) widely spaced bands to resolve RF phase ambiguities. When taken together, these recommendations result in a many-fold increase in the number of observations per session. UV coverage improves to the point where precise VLBI images of the ICRF sources can be constructed on a daily basis directly from the geodetic observations, therefore enabling source structure corrections to be calculated. Simulations are currently underway to evaluate the potential of this approach.

Published
2007

12. Ionospheric local model and climatology from long-term databases of multiple incoherent scatter radars

Author

Shoichiro Fukao, Michael P. Sulzer, Christine Amory-Mazaudier, Shun-Rong Zhang, M. McCready, John M. Holt, Anthony van Eyken, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), EISCAT Scientific Association, SRI International [Menlo Park] (SRI), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Research Institute for Sustainable Humanosphere (RISH), Kyoto University [Kyoto], Arecibo Observatory, National Astronomy and Ionosphere Center (NAIC), Cornell University [New York], EISCAT Scientific Association [Sweden], and NSF Space Weather grant ATM-0207748

Subjects
Electron density, Millstone Hill, 010504 meteorology & atmospheric sciences, Meteorology, [SDE.MCG]Environmental Sciences/Global Changes, Incoherent scatter, Electron, 01 natural sciences, Latitude, law.invention, Physics::Geophysics, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], law, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Radar, 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Geophysics, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Physics::Space Physics, General Earth and Planetary Sciences, Electron temperature, Ionosphere, Geology
Abstract

International audience; Empirical ionospheric local models have been developed from long-term data sets of seven incoherent scatter radars spanning invariant latitudes from 25 to 75 in American, European and Asian longitudes at Svalbard, Tromsø, Sondrestrom, Millstone Hill, St. Santin, Arecibo and Shigaraki. These models, as important complements to global models, represent electron density, ion and electron temperatures, and ion drifts in the E and F regions, giving a comprehensive quantitative description of ionospheric properties. A case study of annual ionospheric variations in electron density and ion temperature is presented based on some of these models. Clear latitudinal, longitudinal, and altitude dependency of annual and semiannual components are found.

Published
2005
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13. Coordinated polar spacecraft, geosynchronous spacecraft, and ground-based observations of magnetopause processes and their coupling to the ionosphere

Author

Chao-Song Huang, T. E. Moore, Christopher T. Russell, K. Yumoto, Y. Zheng, S.-H. Chen, S. M. Petrinec, James A. Slavin, Guan Le, Howard J. Singer, John C. Samson, GSFC Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center (GSFC), Universities Space Research Association (USRA), Institute of Geophysics and Planetary Physics [Los Angeles] (IGPP), University of California [Los Angeles] (UCLA), University of California-University of California, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Space Physics Laboratory, Lockheed Martin Advanced Technology Center (ATC), Department of Physics [Edmonton], University of Alberta, NOAA Space Environment Center, National Oceanic and Atmospheric Administration (NOAA), Space Environment Research Center [Kyushu] (SERC), and Kyushu University [Fukuoka]

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Field line, Magnetosphere, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, Current sheet, Magnetosheath, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Geophysics, lcsh:QC1-999, Solar wind, lcsh:Geophysics. Cosmic physics, Polar wind, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Magnetopause, lcsh:Q, Magnetohydrodynamics, lcsh:Physics
Abstract

In this paper, we present in-situ observations of processes occurring at the magnetopause and vicinity, including surface waves, oscillatory magnetospheric field lines, and flux transfer events, and coordinated observations at geosynchronous orbit by the GOES spacecraft, and on the ground by CANOPUS and 210° Magnetic Meridian (210MM) magnetometer arrays. On 7 February 2002, during a high-speed solar wind stream, the Polar spacecraft was skimming the magnetopause in a post-noon meridian plane for ~3h. During this interval, it made two short excursions and a few partial crossings into the magnetosheath and observed quasi-periodic cold ion bursts in the region adjacent to the magnetopause current layer. The multiple magnetopause crossings, as well as the velocity of the cold ion bursts, indicate that the magnetopause was oscillating with an ~6-min period. Simultaneous observations of Pc5 waves at geosynchronous orbit by the GOES spacecraft and on the ground by the CANOPUS magnetometer array reveal that these magnetospheric pulsations were forced oscillations of magnetic field lines directly driven by the magnetopause oscillations. The magnetospheric pulsations occurred only in a limited longitudinal region in the post-noon dayside sector, and were not a global phenomenon, as one would expect for global field line resonance. Thus, the magnetopause oscillations at the source were also limited to a localized region spanning ~4h in local time. These observations suggest that it is unlikely that the Kelvin-Helmholz instability and/or fluctuations in the solar wind dynamic pressure were the direct driving mechanisms for the observed boundary oscillations. Instead, the likely mechanism for the localized boundary oscillations was pulsed reconnection at the magnetopause occurring along the X-line extending over the same 4-h region. The Pc5 band pressure fluctuations commonly seen in high-speed solar wind streams may modulate the reconnection rate as an indirect cause of the observed Pc5 pulsations. During the same interval, two flux transfer events were also observed in the magnetosphere near the oscillating magnetopause. Their ground signatures were identified in the CANOPUS data. The time delays of the FTE signatures from the Polar spacecraft to the ground stations enable us to estimate that the longitudinal extent of the reconnection X-line at the magnetopause was ~43° or ~5.2 RE. The coordinated in-situ and ground-based observations suggest that FTEs are produced by transient reconnection taking place along a single extended X-line at the magnetopause, as suggested in the models by Scholer(1988) and Southwood et al.(1988). The observations from this study suggest that the reconnection occurred in two different forms simultaneously in the same general region at the dayside magnetopause: 1) continuous reconnection with a pulsed reconnection rate, and 2) transient reconnection as flux transfer events. Key words. Magnetospheric physics (Magnetopause, cusp and boundary layers; Magnetosphere-ionosphere interactions; MHD waves and instabilities)

Published
2004

14. Midlatitude ionospheric plasma temperature climatology and empirical model based on Saint-Santin incoherent scatter radar data from 1966 to 1987

Author

Angela M. Zalucha, Shun-Rong Zhang, Christine Amory-Mazaudier, John M. Holt, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Centre d'étude des environnements terrestre et planétaires (CETP), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Atmospheric Science, Millstone Hill, 010504 meteorology & atmospheric sciences, Meteorology, Incoherent scatter, Soil Science, Aquatic Science, Space weather, Oceanography, Atmospheric sciences, 01 natural sciences, Latitude, Millstone, Atmosphere, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Geochemistry and Petrology, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), empirical model, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, St. Santin, Ecology, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], incoherent scatter radar, Paleontology, Forestry, Geophysics, 13. Climate action, Space and Planetary Science, Climatology, Middle latitudes, ionospheric climatology, ionospheric plasma temperatures, Ionosphere, Geology
Abstract

Ionospheric plasma temperature variations have recently been studied based on incoherent scatter radar (ISR) observations at a lower midlatitude site, Shigaraki, in East Asia [Otsuka et al., 1998] and Millstone Hill, a typical subauroral midlatitude site in North America [Zhang and Holt, 2004]. The French Saint Santin ISR, with a geographic latitude slightly higher but an apex latitude 14° lower than Millstone, collected bistatic and quadristatic measurements for over two solar cycles beginning in September 1965. A database of these data, containing observations between 1966 and 1987, has been used in this study in order to establish the midlatitude ionospheric climatology, in particular that of the upper atmosphere thermal status, as well as empirical models for space weather applications. This paper presents, in comparison with the Millstone Hill results, variations of ion and electron temperatures (Ti and Te) with solar activity, season, time of the day, and altitude. The F2 region Te at St. Santin is found to be lower than at Millstone between March and July, when the St. Santin electron density Ne is relatively higher. The midday Te below 300 km increases with F10.7, as at Millstone Hill. Above 300 km it tends to decrease with F10.7 at St. Santin, while it increases in summer at Millstone Hill. Ti between 250 and 350 km peaks midway between spring and summer. We have also created St. Santin ionospheric models for Ne, Te, and Ti using a bin-fit technique similar to that used for the Millstone Hill models. Comparisons with corresponding IRI predications indicate good agreement in Ti at high solar activity, and above the F2 peak, Te from the IRI tends to be higher than both the St. Santin and Millstone Hill models.

Published
2004
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15. Radar studies of mid-latitude ionospheric plasma drifts

Author

Scherliess, L., Fejer, Bela G., Holt, J., Goncharenko, L., Armory-Mazaudier, C., Buonsanto, M. J., Center for Atmospheric and Space Sciences [Logan], Utah State University (USU), MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Centre d'étude des environnements terrestre et planétaires (CETP), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
drifts, Radar, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Physics, [SDE.MCG]Environmental Sciences/Global Changes, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, latitude, ionosphere, mid, studies, plasma, Physics::Atmospheric and Oceanic Physics
Abstract

International audience; We use incoherent scatter radar measurements from Millstone Hill and Saint Santin to study the midlatitude F region electrodynamic plasma drifts during geomagnetically quiet and active periods. We present initially a local time, season, and solar flux dependent analytical model of the quiet time zonal and meridional ExB drifts over these stations. We discuss, for the first time, the Saint Santin drift patterns during solar maximum. We have used these quiet time models to extract the geomagnetic perturbation drifts which were modeled *s * function of the time history of the auroral electrojet indices. Our results illustrate the evolution of the disturbance drifts driven by the combined effects of prompt penetration *nd longer lasting perturbation electric fields. The meridion*l electrodynamic disturbance drifts have largest amplitudes in the midnight-noon sector. The zonal drifts *re predominantly westward, with largest amplitudes in the dusk-midnight sector *nd, following a decrease in the high-latitude convection, they dec*y more slowly th*n the meridional drifts. The prompt penetration *nd steady state zonal disturbance drifts derived from radar measurements *re in good agreement with results obtained from both the ion drift meter data on board the Dynamics Explorer 2 (DE 2) satellite *nd f?om the Rice Convection Model.

Published
2001

16. Revised Global Model of Thermosphere Winds using satellite and Ground-based observations

Author

Hedin , A.E., Biondi , M.A., Burnside , R.G., Hernández , G., Johnson , R.M., Killeen , T., Mazaudier , C., Meriwether , J.W., Salah , J. E., Sica , R. J., Smith , R.W., Spencer , N.W., Wickwar , V.B., Virdi , T. S., GSFC Planetary Atmospheres Branch, NASA Goddard Space Flight Center ( GSFC ), Department of Physics and Astronomy [Pittsburgh], University of Pittsburgh [Pittsburg] ( PITT ), Arecibo Observatory, National Astronomy and Ionosphere Center ( NAIC ), Cornell University, Graduate Program in Geophysics, University of Washington [Seattle], Space Physics Reasearch Laboratory, University of Michigan [Ann Arbor], Centre de Recherches en Physique de l'Environnement, St Maur, Air Force Geophysics Laboratory, Hanscome Air Force Base, MIT Haystack Observatory, Massachusetts Institute of Technology ( MIT ), Department of Physics and Astronomy [London, ON], University of Western Ontario ( UWO ), Geophysical Institute, University of Alaska Fairbanks ( UAF ), University Research Foundation, Center for Atmospheric and Space Sciences [Logan], Utah State University ( USU ), Physics Department, University College of Wales, NASA Goddard Space Flight Center (GSFC), University of Pittsburgh (PITT), Pennsylvania Commonwealth System of Higher Education (PCSHE)-Pennsylvania Commonwealth System of Higher Education (PCSHE), Arecibo Observatory, National Astronomy and Ionosphere Center (NAIC), Cornell University [New York], Space Physics Research Laboratory [Ann Arbor] (SPRL), University of Michigan System-University of Michigan System, Hanscom Air Force Base (AFB), Massachusetts Institute of Technology (MIT), University of Western Ontario (UWO), Geophysical Institute [Fairbanks], University of Alaska [Fairbanks] (UAF), Utah State University (USU), and University College of Wales [Aberystwyth]

Subjects
[ SDE.MCG ] Environmental Sciences/Global Changes, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDE.MCG]Environmental Sciences/Global Changes, Astrophysics::High Energy Astrophysical Phenomena, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [ SDU.STU.CL ] Sciences of the Universe [physics]/Earth Sciences/Climatology, Physics::Atmospheric and Oceanic Physics
Abstract

International audience; Thermospheric wind data obtained from the Atmosphere Explorer E and Dynamics Explorer2 satellites have been combined with wind data...

Published
1991

17. Ionospheric electrodynamics over Saint-Santin and Millstone Hill during 26-28 June 1984

Author

Salah, Joseph E., Duboin, Marie-Louise, Mazaudier, Christine, MIT Haystack Observatory, Massachusetts Institute of Technology (MIT), Centre de recherches en physique de l'environnement terrestre et planétaire (CRPE), Centre National de la Recherche Scientifique (CNRS), and Administateur, HAL Sorbonne Université

Subjects
F Region, Physics::Space Physics, Electrodynamics, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, Ionospheric Drift, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Incoherent Scatter Radar, Wind Velocity, Thermosphere
Abstract

International audience; Ion drift measurements were carried out using the incoherent scatter radars at Saint-Santin and Millstone Hill during the June 26-28, 1984 Global Thermospheric Mapping Study campaign. The electric field results from both stations for June 26 indicate a pattern characteristic of quiet geomagnetic conditions, consistent between the two stations, in contrast to the results for the geomagnetically disturbed day of June 28 which exhibit large electric fields that differ significantly at the two stations. The meridional neutral winds derived from the ion-drift component parallel to the magnetic field at the two stations under the same model assumptions agree well, and show strong southward winds at night, weaker in the daytime, and large oscillations during magnetic disturbances.

Published
1987

18. Present-day thermal and water activity environment of the Mars Sample Return collection.

Author

Zorzano MP, Martínez G, Polkko J, Tamppari LK, Newman C, Savijärvi H, Goreva Y, Viúdez-Moreiras D, Bertrand T, Smith M, Hausrath EM, Siljeström S, Benison K, Bosak T, Czaja AD, Debaille V, Herd CDK, Mayhew L, Sephton MA, Shuster D, Simon JI, Weiss B, Randazzo N, Mandon L, Brown A, Hecht MH, and Martínez-Frías J

Abstract

The Mars Sample Return mission intends to retrieve a sealed collection of rocks, regolith, and atmosphere sampled from Jezero Crater, Mars, by the NASA Perseverance rover mission. For all life-related research, it is necessary to evaluate water availability in the samples and on Mars. Within the first Martian year, Perseverance has acquired an estimated total mass of 355 g of rocks and regolith, and 38 μmoles of Martian atmospheric gas. Using in-situ observations acquired by the Perseverance rover, we show that the present-day environmental conditions at Jezero allow for the hydration of sulfates, chlorides, and perchlorates and the occasional formation of frost as well as a diurnal atmospheric-surface water exchange of 0.5-10 g water per m 2 (assuming a well-mixed atmosphere). At night, when the temperature drops below 190 K, the surface water activity can exceed 0.5, the lowest limit for cell reproduction. During the day, when the temperature is above the cell replication limit of 245 K, water activity is less than 0.02. The environmental conditions at the surface of Jezero Crater, where these samples were acquired, are incompatible with the cell replication limits currently known on Earth., (© 2024. The Author(s).)

Published
2024
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19. Complete Global Total Electron Content Map Dataset based on a Video Imputation Algorithm VISTA.

Author

Sun H, Chen Y, Zou S, Ren J, Chang Y, Wang Z, and Coster A

Abstract

Ionospheric total electron content (TEC) derived from multi-frequency Global Navigation Satellite System (GNSS) signals and the relevant products have become one of the most utilized parameters in the space weather and ionospheric research community. However, there are a couple of challenges in using the global TEC map data including large data gaps over oceans and the potential of losing meso-scale ionospheric structures when applying traditional reconstruction and smoothing algorithms. In this paper, we describe and release a global TEC map database, constructed and completed based on the Madrigal TEC database with a novel video imputation algorithm called VISTA (Video Imputation with SoftImpute, Temporal smoothing and Auxiliary data). The complete TEC maps reveal important large-scale TEC structures and preserve the observed meso-scale structures. Basic ideas and the pipeline of the video imputation algorithm are introduced briefly, followed by discussions on the computational costs and fine tuning of the adopted algorithm. Discussions on potential usages of the complete TEC database are given, together with a concrete example of applying this database., (© 2023. The Author(s).)

Published
2023
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20. Mars Oxygen ISRU Experiment (MOXIE)-Preparing for human Mars exploration.

Author

Hoffman JA, Hecht MH, Rapp D, Hartvigsen JJ, SooHoo JG, Aboobaker AM, McClean JB, Liu AM, Hinterman ED, Nasr M, Hariharan S, Horn KJ, Meyen FE, Okkels H, Steen P, Elangovan S, Graves CR, Khopkar P, Madsen MB, Voecks GE, Smith PH, Skafte TL, Araghi KR, and Eisenman DJ

Abstract

MOXIE [Mars Oxygen In Situ Resource Utilization (ISRU) Experiment] is the first demonstration of ISRU on another planet, producing oxygen by solid oxide electrolysis of carbon dioxide in the martian atmosphere. A scaled-up MOXIE would contribute to sustainable human exploration of Mars by producing on-site the tens of tons of oxygen required for a rocket to transport astronauts off the surface of Mars, instead of having to launch hundreds of tons of material from Earth's surface to transport the required oxygen to Mars. MOXIE has produced oxygen seven times between landing in February 2021 and the end of 2021 and will continue to demonstrate oxygen production during night and day throughout all martian seasons. This paper reviews what MOXIE has accomplished and the implications for larger-scale oxygen-producing systems.

Published
2022
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21. Night-Time Ionospheric Localized Enhancements (NILE) Observed in North America Following Geomagnetic Disturbances.

Author

Chartier AT, Datta-Barua S, McDonald SE, Bust GS, Tate J, Goncharenko LP, Romeo G, and Schaefer RK

Abstract

The Ionospheric Data Assimilation Four-Dimensional (IDA4D) technique has been coupled to Sami3, which is another model of the ionosphere (SAMI3). In this application, ground-based and space-based GPS total electron content (TEC) data have been assimilated into SAMI3, while in-situ electron densities, autoscaled ionosonde NmF2, and reference GPS stations have been used for validation. IDA4D/SAMI3 shows that night-time ionospheric localized enhancements (NILE) are formed following geomagnetic storms in November 2003 and August 2018. The NILE phenomenon appears as a moderate, longitudinally extended enhancement of NmF2 at 30°-40°N MLAT, occurring in the late evening (20-24 LT) following much larger enhancements of the equatorial anomaly crests in the main phase of the storms. The NILE appears to be caused by upward and northward plasma transport around the dusk terminator, which is consistent with eastward polarization electric fields. Independent validation confirms the presence of the NILE, and indicates that IDA4D is effective in correcting random errors and systematic biases in SAMI3. In all cases, biases and root-mean-square errors are reduced by the data assimilation, typically by a factor of 2 or more. During the most severe part of the November 2003 storm, the uncorrected ionospheric error on a GPS 3D position at 1LSU (Louisiana) is estimated to exceed 34 m. The IDA4D/SAMI3 specification is effective in correcting this down to 10 m., (© 2021. The Authors.)

Published
2021
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22. Subpacket structure in strong VLF chorus rising tones: characteristics and consequences for relativistic electron acceleration.

Author

Foster JC, Erickson PJ, and Omura Y

Abstract

Van Allen Probes in situ observations are used to examine detailed subpacket structure observed in strong VLF (very low frequency) rising-tone chorus elements observed at the time of a rapid MeV electron energization in the inner magnetosphere. Analysis of the frequency gap between lower and upper chorus-band waves identifies f ceEQ , the electron gyrofrequency in the equatorial wave generation region. Initial subpackets in these strong chorus rising-tone elements begin at a frequency near 1/4 f ceEQ and exhibit smooth gradual frequency increase across their > 10 ms temporal duration. A second much stronger subpacket is seen at frequencies around the local value of 1/4 f ce with small wave normal angle (< 10°) and steeply rising d f /d t . Smooth frequency and phase variation across and between the initial subpackets support continuous phase trapping of resonant electrons and increased potential for MeV electron acceleration. The total energy gain for individual seed electrons with energies between 100 keV and 3 MeV ranges between 2 and 15%, in their nonlinear interaction with a single chorus element., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2021.)

Published
2021
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23. Modernizing and Expanding the NASA Space Geodesy Network to Meet Future Geodetic Requirements.

Author

Merkowitz SM, Bolotin S, Elosegui P, Esper J, Gipson J, Hilliard L, Himwich E, Hoffman ED, Lakins DD, Lamb RC, Lemoine FG, Long JL, McGarry JF, MacMillan DS, Michael BP, Noll C, Pavlis EC, Pearlman MR, Ruszczyk C, Shappirio MD, and Stowers DA

Abstract

NASA maintains and operates a global network of Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and Global Navigation Satellite System (GNSS) ground stations as part of the NASA Space Geodesy Program. The NASA Space Geodesy Network (NSGN) provides the geodetic products that support Earth observations and the related science requirements as outlined by the US National Research Council (NRC 2010, 2018). The Global Geodetic Observing System (GGOS) and the NRC have set an ambitious goal of improving the Terrestrial Reference Frame (TRF) to have an accuracy of 1 millimeter and stability of 0.1 millimeters per year, an order of magnitude beyond current capabilities. NASA and its partners within GGOS are addressing this challenge by planning and implementing modern geodetic stations co-located at existing and new sites around the world. In 2013, NASA demonstrated the performance of its next-generation systems at the prototype next-generation core site at NASA's Goddard Geophysical and Astronomical Observatory in Greenbelt, Maryland. Implementation of a new broadband VLBI station in Hawaii was completed in 2016. NASA is currently implementing new VLBI and SLR stations in Texas and is planning the replacement of its other aging domestic and international legacy stations. In this article, we describe critical gaps in the current global network and discuss how the new NSGN will expand the global geodetic coverage and ultimately improve the geodetic products. We also describe the characteristics of a modern NSGN site and the capabilities of the next-generation NASA SLR and VLBI systems. Finally, we outline the plans for efficiently operating the NSGN by centralizing and automating the operations of the new geodetic stations.

Published
2019
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24. Low Altitude Solar Magnetic Reconnection, Type III Solar Radio Bursts, and X-ray Emissions.

Author

Cairns IH, Lobzin VV, Donea A, Tingay SJ, McCauley PI, Oberoi D, Duffin RT, Reiner MJ, Hurley-Walker N, Kudryavtseva NA, Melrose DB, Harding JC, Bernardi G, Bowman JD, Cappallo RJ, Corey BE, Deshpande A, Emrich D, Goeke R, Hazelton BJ, Johnston-Hollitt M, Kaplan DL, Kasper JC, Kratzenberg E, Lonsdale CJ, Lynch MJ, McWhirter SR, Mitchell DA, Morales MF, Morgan E, Ord SM, Prabu T, Roshi A, Shankar NU, Srivani KS, Subrahmanyan R, Wayth RB, Waterson M, Webster RL, Whitney AR, Williams A, and Williams CL

Abstract

Type III solar radio bursts are the Sun's most intense and frequent nonthermal radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III bursts imaged by the Murchison Widefield Array and detected by the Learmonth radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5-10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III radio bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III bursts; thus different special conditions exist for electrons leaving reconnection regions to produce observable radio, EUV, UV, and X-ray bursts.

Published
2018
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25. Observations of the step-like accelerating processes of cold ions in the reconnection layer at the dayside magnetopause.

Author

Zhang Q, Lockwood M, Foster JC, Zong Q, Dunlop MW, Zhang S, Moen J, and Zhang B

Abstract

Cold ions of plasmaspheric origin have been observed to abundantly appear in the magnetospheric side of the Earth's magnetopause. These cold ions could affect the magnetic reconnection processes at the magnetopause by changing the Alfvén velocity and the reconnection rate, while they could also be heated in the reconnection layer during the ongoing reconnections. We report in situ observations from a partially crossing of a reconnection layer near the subsolar magnetopause. During this crossing, step-like accelerating processes of the cold ions were clearly observed, suggesting that the inflow cold ions may be separately accelerated by the rotation discontinuity and slow shock inside the reconnection layer., (Copyright © 2018 Science China Press. Published by Elsevier B.V. All rights reserved.)

Published
2018
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26. Testing General Relativity with Accretion-Flow Imaging of Sgr A^{*}.

Author

Johannsen T, Wang C, Broderick AE, Doeleman SS, Fish VL, Loeb A, and Psaltis D

Abstract

The Event Horizon Telescope is a global, very long baseline interferometer capable of probing potential deviations from the Kerr metric, which is believed to provide the unique description of astrophysical black holes. Here, we report an updated constraint on the quadrupolar deviation of Sagittarius A^{*} within the context of a radiatively inefficient accretion flow model in a quasi-Kerr background. We also simulate near-future constraints obtainable by the forthcoming eight-station array and show that in this model already a one-day observation can measure the spin magnitude to within 0.005, the inclination to within 0.09°, the position angle to within 0.04°, and the quadrupolar deviation to within 0.005 at 3σ confidence. Thus, we are entering an era of high-precision strong gravity measurements.

Published
2016
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27. Highly relativistic radiation belt electron acceleration, transport, and loss: Large solar storm events of March and June 2015.

Author

Baker DN, Jaynes AN, Kanekal SG, Foster JC, Erickson PJ, Fennell JF, Blake JB, Zhao H, Li X, Elkington SR, Henderson MG, Reeves GD, Spence HE, Kletzing CA, and Wygant JR

Abstract

Two of the largest geomagnetic storms of the last decade were witnessed in 2015. On 17 March 2015, a coronal mass ejection-driven event occurred with a Dst (storm time ring current index) value reaching -223 nT. On 22 June 2015 another strong storm ( Dst reaching -204 nT) was recorded. These two storms each produced almost total loss of radiation belt high-energy ( E  ≳ 1 MeV) electron fluxes. Following the dropouts of radiation belt fluxes there were complex and rather remarkable recoveries of the electrons extending up to nearly 10 MeV in kinetic energy. The energized outer zone electrons showed a rich variety of pitch angle features including strong "butterfly" distributions with deep minima in flux at α  = 90°. However, despite strong driving of outer zone earthward radial diffusion in these storms, the previously reported "impenetrable barrier" at L  ≈ 2.8 was pushed inward, but not significantly breached, and no E  ≳ 2.0 MeV electrons were seen to pass through the radiation belt slot region to reach the inner Van Allen zone. Overall, these intense storms show a wealth of novel features of acceleration, transport, and loss that are demonstrated in the present detailed analysis.

Published
2016
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28. Testing General Relativity with the Shadow Size of Sgr A(*).

Author

Johannsen T, Broderick AE, Plewa PM, Chatzopoulos S, Doeleman SS, Eisenhauer F, Fish VL, Genzel R, Gerhard O, and Johnson MD

Abstract

In general relativity, the angular radius of the shadow of a black hole is primarily determined by its mass-to-distance ratio and depends only weakly on its spin and inclination. If general relativity is violated, however, the shadow size may also depend strongly on parametric deviations from the Kerr metric. Based on a reconstructed image of Sagittarius A^{*} (Sgr A^{*}) from a simulated one-day observing run of a seven-station Event Horizon Telescope (EHT) array, we employ a Markov chain Monte Carlo algorithm to demonstrate that such an observation can measure the angular radius of the shadow of Sgr A^{*} with an uncertainty of ∼1.5  μas (6%). We show that existing mass and distance measurements can be improved significantly when combined with upcoming EHT measurements of the shadow size and that tight constraints on potential deviations from the Kerr metric can be obtained.

Published
2016
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29. Jet-launching structure resolved near the supermassive black hole in M87.

Author

Doeleman SS, Fish VL, Schenck DE, Beaudoin C, Blundell R, Bower GC, Broderick AE, Chamberlin R, Freund R, Friberg P, Gurwell MA, Ho PT, Honma M, Inoue M, Krichbaum TP, Lamb J, Loeb A, Lonsdale C, Marrone DP, Moran JM, Oyama T, Plambeck R, Primiani RA, Rogers AE, Smythe DL, SooHoo J, Strittmatter P, Tilanus RP, Titus M, Weintroub J, Wright M, Young KH, and Ziurys LM

Abstract

Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations, at a wavelength of 1.3 millimeters, of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 ± 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.

Published
2012
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30. Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre.

Author

Doeleman SS, Weintroub J, Rogers AE, Plambeck R, Freund R, Tilanus RP, Friberg P, Ziurys LM, Moran JM, Corey B, Young KH, Smythe DL, Titus M, Marrone DP, Cappallo RJ, Bock DC, Bower GC, Chamberlin R, Davis GR, Krichbaum TP, Lamb J, Maness H, Niell AE, Roy A, Strittmatter P, Werthimer D, Whitney AR, and Woody D

Abstract

The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation. Sagittarius A* (Sgr A*), the compact source of radio, infrared and X-ray emission at the centre of the Milky Way, is the closest example of this phenomenon, with an estimated black hole mass that is 4,000,000 times that of the Sun. A long-standing astronomical goal is to resolve structures in the innermost accretion flow surrounding Sgr A*, where strong gravitational fields will distort the appearance of radiation emitted near the black hole. Radio observations at wavelengths of 3.5 mm and 7 mm have detected intrinsic structure in Sgr A*, but the spatial resolution of observations at these wavelengths is limited by interstellar scattering. Here we report observations at a wavelength of 1.3 mm that set a size of 37(+16)(-10) microarcseconds on the intrinsic diameter of Sgr A*. This is less than the expected apparent size of the event horizon of the presumed black hole, suggesting that the bulk of Sgr A* emission may not be centred on the black hole, but arises in the surrounding accretion flow.

Published
2008
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