Search

Your search keyword '"Blake, J. B"' showing total 1,078 results
Start Over Author "Blake, J. B"
1,078 results on '"Blake, J. B"'

153. Diffusive Transport of Several Hundred keV Electrons in the Earth's Slot Region

Author

Ma, Q., primary, Li, W., additional, Thorne, R. M., additional, Bortnik, J., additional, Reeves, G. D., additional, Spence, H. E., additional, Turner, D. L., additional, Blake, J. B., additional, Fennell, J. F., additional, Claudepierre, S. G., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Hospodarsky, G. B., additional, and Baker, D. N., additional

Published
2017
Full Text
View/download PDF

159. Generation of extremely low frequency chorus in Van Allen radiation belts

Author

Xiao, Fuliang, primary, Liu, Si, additional, Tao, Xin, additional, Su, Zhenpeng, additional, Zhou, Qinghua, additional, Yang, Chang, additional, He, Zhaoguo, additional, He, Yihua, additional, Gao, Zhonglei, additional, Baker, D. N., additional, Spence, H. E., additional, Reeves, G. D., additional, Funsten, H. O., additional, and Blake, J. B., additional

Published
2017
Full Text
View/download PDF

160. The FIREBIRD Instrument for Relativistic Electrons: Enabling Technologies for a Fast High-Sensitivity, Low-Power Space Weather Radiation Payload

Author

Crew, Alexander B., Larsen, Brian A., Klumpar, David M., Mosleh, Ehson, Spence, H. E., Legere, J., Blake, J. B., Springer, Larry, Widholm, M., Mashburn, K., Gunderson, A., Handley, M., Longsworth, S., Smith, S., and O'Brien, T. P.

Abstract

Miniaturized instrument payloads on small satellite and nanosatellite platforms that are deployed in low Earth orbit are demonstrating cost effective weather monitoring platforms with increased temporal and spatial resolution compared to larger weather satellites. The NASA Earth Decadal Survey [1] states that improving the revisit time of microwave radiometers would significantly improve weather forecasting. Radiometers such as the Advanced Technology Microwave Sounder (ATMS) on Suomi National Polar-orbiting Partnership (Suomi-NPP) and the Joint Polar Satellite System-1 (JPSS-1), now NOAA-20, provide an average revisit rate of 7.6 hours; however, a constellation of six CubeSats in three orbital Low Earth Orbit (LEO) planes with microwave radiometers such as the Time-Resolved Observations of Precipitations structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission would provide a refresh rate of better than 60 minutes. In order to effectively use CubeSats in a constellation as a weather monitoring platform, calibration must be used to provide measurements consistent with state of the art measurements, such as ATMS that has a NeDT at 300K of 0.5-3.0K [2]. In this work, we use the Joint Center for Satellite Data Assimilation (JCSDA) Community Radiative Transfer Model (CRTM) to simulate brightness temperatures (https://www.jcsda.noaa.gov/projects_crtm.php), which are used to assess miniaturized microwave radiometer radiometric biases. CRTM is a fast radiative transfer model that uses Fortran functions, structure variables, and coefficient data of the modeled sensor to simulate radiances. The user inputs surface characteristics, scan angles, and atmospheric profiles from sources such as radiosondes, Numerical Weather Prediction (NWP) models, and Global Positioning System Radio Occultation (GPSRO) measurements. The output of CRTM is a simulated brightness temperature that is used to correct radiometric biases in order to meet required instrument NeDT performance. We use radiosonde, GPSRO, and NWP ERA-5 atmospheric profiles in CRTM and compare the results to ATMS brightness temperatures and find an average difference in brightness temperature of 1.95 K, which is comparable to ATMS Integrated Calibration/Validation System (https://www.star.nesdis.noaa.gov/icvs/status_NPP_ATMS.php) reports which show channel bias variations of up to 2 K. We take a similar approach to provide calibration for the Micro-sized Microwave Atmospheric Satellite-2A (MicroMAS-2A), a 3U CubeSat that was launched on January 11th, 2018. MicroMAS-2A carries a 1U 10-channel passive microwave radiometer that provides imagery near 90 and 206 GHz, temperature sounding near 118 GHz, and moisture sounding near 183 GHz. We develop an approach for comparing MicroMas-2A brightness temperatures to radiosonde, GPSRO, and NWP ERA5 atmospheric profiles. Due to the scarcity of GPSRO and radiosonde profiles near the MicroMAS-2A data segments, we determine that NWP models will be the best option for radiance validation. After the next stage of calibration of MicroMAS-2A is completed, we will compare CRTM simulated radiances from ERA profiles to the initial sensor data, with expected results of channel bias variations of < 2 K.

Published
2015

162. Examining Coherency Scales, Substructure, and Propagation of Whistler Mode Chorus Elements With Magnetospheric Multiscale (MMS)

Author

Turner, D. L., Lee, J. H., Claudepierre, S. G., Fennell, J. F., Blake, J. B., Jaynes, A. N., Leonard, T., Wilder, F. D., Ergun, R. E., Baker, D. N., Cohen, I. J., Mauk, B. H., Strangeway, R. J., Hartley, D. P., Kletzing, C. A., Breuillard, H., Le Contel, O., Khotyaintsev, Yuri V., Torbert, R. B., Allen, R. C., Burch, J. L., Santolik, O., Turner, D. L., Lee, J. H., Claudepierre, S. G., Fennell, J. F., Blake, J. B., Jaynes, A. N., Leonard, T., Wilder, F. D., Ergun, R. E., Baker, D. N., Cohen, I. J., Mauk, B. H., Strangeway, R. J., Hartley, D. P., Kletzing, C. A., Breuillard, H., Le Contel, O., Khotyaintsev, Yuri V., Torbert, R. B., Allen, R. C., Burch, J. L., and Santolik, O.

Abstract

Whistler mode chorus waves are a naturally occurring electromagnetic emission observed in Earth's magnetosphere. Here, for the first time, data from NASA's Magnetospheric Multiscale (MMS) mission were used to analyze chorus waves in detail, including the calculation of chorus wave normal vectors, k. A case study was examined from a period of substorm activity around the time of a conjunction between the MMS constellation and NASA's Van Allen Probes mission on 07 April 2016. Chorus wave activity was simultaneously observed by all six spacecraft over a broad range of L shells (5.5 < L < 8.5), magnetic local time (06: 00 < MLT < 09: 00), and magnetic latitude (-32 degrees < MLAT < -15 degrees), implying a large chorus active region. Eight chorus elements and their substructure were analyzed in detail with MMS. These chorus elements were all lower band and rising tone emissions, right-handed and nearly circularly polarized, and propagating away from the magnetic equator when they were observed at MMS (MLAT similar to-31 degrees). Most of the elements had "hook"-like signatures on their wave power spectra, characterized by enhanced wave power at flat or falling frequency following the peak, and all the elements exhibited complex and well-organized substructure observed consistently at all four MMS spacecraft at separations up to 70 km (60 km perpendicular and 38 km parallel to the background magnetic field). The waveforms in field-aligned coordinates also demonstrated that these waves were all phase coherent, allowing for the direct calculation of k. Error estimates on calculated k revealed that the plane wave approximation was valid for six of the eight elements and most of the subelements. The wave normal vectors were within 20-30 degrees from the direction antiparallel to the background field for all elements and changed from subelement to subelement through at least two of the eight elements. The azimuthal angle of k in the perpendicular plane was o

Published
2017
Full Text
View/download PDF

163. Relativistic Electron Increase During Chorus Wave Activities on the 6-8 March 2016 Geomagnetic Storm

Author

Matsui, H., Torbert, R. B., Spence, H. E., Argall, M. R., Alm, L., Farrugia, C. J., Kurth, W. S., Baker, D. N., Blake, J. B., Funsten, H. O., Reeves, G. D., Ergun, R. E., Khotyaintsev, Yuri V., Lindqvist, P. -A, Matsui, H., Torbert, R. B., Spence, H. E., Argall, M. R., Alm, L., Farrugia, C. J., Kurth, W. S., Baker, D. N., Blake, J. B., Funsten, H. O., Reeves, G. D., Ergun, R. E., Khotyaintsev, Yuri V., and Lindqvist, P. -A

Abstract

There was a geomagnetic storm on 6-8 March 2016, in which Van Allen Probes A and B separated by similar to 2.5 h measured increase of relativistic electrons with energies approximately several hundred keV to 1 MeV. Simultaneously, chorus waves were measured by both Van Allen Probes and Magnetospheric Multiscale (MMS) mission. Some of the chorus elements were rising tones, possibly due to nonlinear effects. These measurements are compared with a nonlinear theory of chorus waves incorporating the inhomogeneity ratio and the field equation. From this theory, a chorus wave profile in time and one-dimensional space is simulated. Test particle calculations are then performed in order to examine the energization rate of electrons. Some electrons are accelerated, although more electrons are decelerated. The measured time scale of the electron increase is inferred to be consistent with this nonlinear theory.

Published
2017
Full Text
View/download PDF

164. Kinetic evidence of magnetic reconnection due to Kelvin-Helmholtz waves

Author

Li, W., Andre, M., Khotyaintsev, Yu. V., Vaivads, A., Graham, D. B., Toledo-Redondo, S., Norgren, C., Henri, P., Wang, C., Tang, B. B., Lavraud, B., Vernisse, Y., Turner, D. L., Burch, J., Torbert, R., Magnes, W., Russell, C. T., Blake, J. B., Mauk, B., Giles, B., Pollock, C., Fennell, J., Jaynes, A., Avanov, L. A., Dorelli, J. C., Gershman, D. J., Paterson, W. R., Saito, Yoshifumi, Strangeway, R. J., 齋藤, 義文, Li, W., Andre, M., Khotyaintsev, Yu. V., Vaivads, A., Graham, D. B., Toledo-Redondo, S., Norgren, C., Henri, P., Wang, C., Tang, B. B., Lavraud, B., Vernisse, Y., Turner, D. L., Burch, J., Torbert, R., Magnes, W., Russell, C. T., Blake, J. B., Mauk, B., Giles, B., Pollock, C., Fennell, J., Jaynes, A., Avanov, L. A., Dorelli, J. C., Gershman, D. J., Paterson, W. R., Saito, Yoshifumi, Strangeway, R. J., and 齋藤, 義文

Abstract

著者人数: 29名, Accepted: 2016-05-18

Published
2017

166. Generation of unusually low frequency plasmaspheric hiss

Author

Chen, Lunjin, Thorne, Richard M., Bortnik, Jacob, Li, Wen, Horne, Richard B., Reeves, G. D., Kletzing, C. A., Kurth, W. S., Hospodarsky, G. B., Spence, H. E., Blake, J. B., and Fennell, J. F.

Abstract

It has been reported from Van Allen Probe observations that plasmaspheric hiss intensification in the outer plasmasphere, associated with a substorm injection on 30 September 2012, occurred with a peak frequency near 100 Hz, well below the typical plasmaspheric hiss frequency range, extending down to ∼20 Hz. We examine this event of unusually low frequency plasmaspheric hiss to understand its generation mechanism. Quantitative analysis is performed by simulating wave raypaths via the HOTRAY ray tracing code with measured plasma density and calculating raypath-integrated wave gain evaluated using the measured energetic electron distribution. We demonstrate that the growth rate due to substorm-injected electrons is positive but rather weak, leading to small wave gain (∼10 dB) during a single equatorial crossing. Propagation characteristics aided by the sharp density gradient associated with the plasmapause, however, can enable these low-frequency waves to undergo cyclic raypaths, which return to the unstable region leading to repeated amplification to yield sufficient net wave gain (>40 dB) to allow waves to grow from the thermal noise.

Published
2014
Full Text
View/download PDF

167. Simultaneous disappearances of plasmaspheric hiss, exohiss, and chorus waves triggered by a sudden decrease in solar wind dynamic pressure

Author

Liu, Nigang, primary, Su, Zhenpeng, additional, Gao, Zhonglei, additional, Zheng, Huinan, additional, Wang, Yuming, additional, Wang, Shui, additional, Spence, H. E., additional, Reeves, G. D., additional, Baker, D. N., additional, Blake, J. B., additional, Funsten, H. O., additional, and Wygant, J. R., additional

Published
2017
Full Text
View/download PDF

169. Kinetic evidence of magnetic reconnection due to Kelvin-Helmholtz waves

Author

Li, Wenya, Andre, Mats, Khotyaintsev, Yuri V., Vaivads, Andris, Graham, Daniel B., Toledo-Redondo, S., Norgren, Cecilia, Henri, P., Wang, C., Tang, B. B., Lavraud, B., Vernisse, Y., Turner, D. L., Burch, J., Torbert, R., Magnes, W., Russell, C. T., Blake, J. B., Mauk, B., Giles, B., Pollock, C., Fennell, J., Jaynes, A., Avanov, L. A., Dorelli, J. C., Gershman, D. J., Paterson, W. R., Saito, Y., Strangeway, R. J., Li, Wenya, Andre, Mats, Khotyaintsev, Yuri V., Vaivads, Andris, Graham, Daniel B., Toledo-Redondo, S., Norgren, Cecilia, Henri, P., Wang, C., Tang, B. B., Lavraud, B., Vernisse, Y., Turner, D. L., Burch, J., Torbert, R., Magnes, W., Russell, C. T., Blake, J. B., Mauk, B., Giles, B., Pollock, C., Fennell, J., Jaynes, A., Avanov, L. A., Dorelli, J. C., Gershman, D. J., Paterson, W. R., Saito, Y., and Strangeway, R. J.

Abstract

The Kelvin-Helmholtz (KH) instability at the Earth's magnetopause is predominantly excited during northward interplanetary magnetic field (IMF). Magnetic reconnection due to KH waves has been suggested as one of the mechanisms to transfer solar wind plasma into the magnetosphere. We investigate KH waves observed at the magnetopause by the Magnetospheric Multiscale (MMS) mission; in particular, we study the trailing edges of KH waves with Alfvenic ion jets. We observe gradual mixing of magnetospheric and magnetosheath ions at the boundary layer. The magnetospheric electrons with energy up to 80keV are observed on the magnetosheath side of the jets, which indicates that they escape into the magnetosheath through reconnected magnetic field lines. At the same time, the low-energy (below 100eV) magnetosheath electrons enter the magnetosphere and are heated in the field-aligned direction at the high-density edge of the jets. Our observations provide unambiguous kinetic evidence for ongoing reconnection due to KH waves., QC 20190625

Published
2016
Full Text
View/download PDF

170. Dipolarization in the inner magnetosphere during a geomagnetic storm on 7 October 2015

Author

Matsui, H., Erickson, P. J., Foster, J. C., Torbert, R. B., Argall, M. R., Anderson, B. J., Blake, J. B., Cohen, I. J., Ergun, R. E., Farrugia, C. J., Khotyaintsev, Yu. V., Korth, H., Lindqvist, Per-Arne, Magnes, W., Marklund, Göran, Mauk, B. H., Paulson, K. W., Russell, C. T., Strangeway, R. J., Turner, D. L., Matsui, H., Erickson, P. J., Foster, J. C., Torbert, R. B., Argall, M. R., Anderson, B. J., Blake, J. B., Cohen, I. J., Ergun, R. E., Farrugia, C. J., Khotyaintsev, Yu. V., Korth, H., Lindqvist, Per-Arne, Magnes, W., Marklund, Göran, Mauk, B. H., Paulson, K. W., Russell, C. T., Strangeway, R. J., and Turner, D. L.

Abstract

A dipolarization event was observed by the Magnetospheric Multiscale (MMS) spacecraft at L = 3.8 and 19.8 magnetic local time starting at similar to 23:42:36 UT on 7 October 2015. The magnetic and electric fields showed initially coherent variations between the spacecraft. The sunward convection turned tailward after the dipolarization. The observation is interpreted in terms of the pressure balance or the momentum equation. This was followed by a region traversed where the fields were irregular. The scale length was of the order of the ion gyroradius, suggesting the kinetic nature of the fluctuations. Combination of the multi-instrument, multispacecraft data reveals a more detailed picture of the dipolarization event in the inner magnetosphere. Conjunction ionosphere-plasmasphere observations from DMSP, two-dimensional GPS total electron content, the Millstone Hill midlatitude incoherent scatter radar, and AMPERE measurements imply that MMS observations are located on the poleward edge of the ionospheric trough where Region 2 field-aligned currents flow., QC 20161128

Published
2016
Full Text
View/download PDF

171. Characteristic energy range of electron scattering due to plasmaspheric hiss

Author

Ma, Q., primary, Li, W., additional, Thorne, R. M., additional, Bortnik, J., additional, Reeves, G. D., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Hospodarsky, G. B., additional, Spence, H. E., additional, Baker, D. N., additional, Blake, J. B., additional, Fennell, J. F., additional, Claudepierre, S. G., additional, and Angelopoulos, V., additional

Published
2016
Full Text
View/download PDF

173. Dipolarization in the inner magnetosphere during a geomagnetic storm on 7 October 2015

Author

Matsui, H., primary, Erickson, P. J., additional, Foster, J. C., additional, Torbert, R. B., additional, Argall, M. R., additional, Anderson, B. J., additional, Blake, J. B., additional, Cohen, I. J., additional, Ergun, R. E., additional, Farrugia, C. J., additional, Khotyaintsev, Yu. V., additional, Korth, H., additional, Lindqvist, P.-A., additional, Magnes, W., additional, Marklund, G. T., additional, Mauk, B. H., additional, Paulson, K. W., additional, Russell, C. T., additional, Strangeway, R. J., additional, and Turner, D. L., additional

Published
2016
Full Text
View/download PDF

174. The relationship between the plasmapause and outer belt electrons

Author

Goldstein, J., primary, Baker, D. N., additional, Blake, J. B., additional, De Pascuale, S., additional, Funsten, H. O., additional, Jaynes, A. N., additional, Jahn, J.‐M., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Li, W., additional, Reeves, G. D., additional, and Spence, H. E., additional

Published
2016
Full Text
View/download PDF

176. Physical mechanism causing rapid changes in ultrarelativistic electron pitch angle distributions right after a shock arrival: Evaluation of an electron dropout event

Author

Zhang, X.‐J., primary, Li, W., additional, Thorne, R. M., additional, Angelopoulos, V., additional, Ma, Q., additional, Li, J., additional, Bortnik, J., additional, Nishimura, Y., additional, Chen, L., additional, Baker, D. N., additional, Reeves, G. D., additional, Spence, H. E., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Hospodarsky, G. B., additional, Blake, J. B., additional, and Fennell, J. F., additional

Published
2016
Full Text
View/download PDF

177. Current energetic particle sensors

Author

Fennell, J. F., primary, Blake, J. B., additional, Claudepierre, S., additional, Mazur, J., additional, Kanekal, S., additional, O'Brien, P., additional, Baker, D., additional, Crain, W., additional, Mabry, D., additional, and Clemmons, J., additional

Published
2016
Full Text
View/download PDF

180. Statistical properties of the radiation belt seed population

Author

Boyd, A. J., primary, Spence, H. E., additional, Huang, C.‐L., additional, Reeves, G. D., additional, Baker, D. N., additional, Turner, D. L., additional, Claudepierre, S. G., additional, Fennell, J. F., additional, Blake, J. B., additional, and Shprits, Y. Y., additional

Published
2016
Full Text
View/download PDF

181. Prompt acceleration of magnetospheric electrons to ultrarelativistic energies by the 17 March 2015 interplanetary shock

Author

Kanekal, S. G., primary, Baker, D. N., additional, Fennell, J. F., additional, Jones, A., additional, Schiller, Q., additional, Richardson, I. G., additional, Li, X., additional, Turner, D. L., additional, Califf, S., additional, Claudepierre, S. G., additional, Wilson, L. B., additional, Jaynes, A., additional, Blake, J. B., additional, Reeves, G. D., additional, Spence, H. E., additional, Kletzing, C. A., additional, and Wygant, J. R., additional

Published
2016
Full Text
View/download PDF

184. Direct evidence for EMIC wave scattering of relativistic electrons in space

Author

Zhang, X.‐J., primary, Li, W., additional, Ma, Q., additional, Thorne, R. M., additional, Angelopoulos, V., additional, Bortnik, J., additional, Chen, L., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Hospodarsky, G. B., additional, Baker, D. N., additional, Reeves, G. D., additional, Spence, H. E., additional, Blake, J. B., additional, and Fennell, J. F., additional

Published
2016
Full Text
View/download PDF

185. Nonstorm time dropout of radiation belt electron fluxes on 24 September 2013

Author

Su, Zhenpeng, primary, Gao, Zhonglei, additional, Zhu, Hui, additional, Li, Wen, additional, Zheng, Huinan, additional, Wang, Yuming, additional, Wang, Shui, additional, Spence, H. E., additional, Reeves, G. D., additional, Baker, D. N., additional, Blake, J. B., additional, Funsten, H. O., additional, and Wygant, J. R., additional

Published
2016
Full Text
View/download PDF

186. Microinjections observed by MMS FEEPS in the dusk to midnight region

Author

Fennell, J. F., primary, Turner, D. L., additional, Lemon, C. L., additional, Blake, J. B., additional, Clemmons, J. H., additional, Mauk, B. H., additional, Jaynes, A. N., additional, Cohen, I. J., additional, Westlake, J. H., additional, Baker, D. N., additional, Craft, J. V., additional, Spence, H. E., additional, Reeves, G. D., additional, Torbert, R. B., additional, Burch, J. L., additional, Giles, B. L., additional, Paterson, W. R., additional, and Strangeway, R. J., additional

Published
2016
Full Text
View/download PDF

188. Radiation belt electron acceleration during the 17 March 2015 geomagnetic storm: Observations and simulations

Author

Li, W., primary, Ma, Q., additional, Thorne, R. M., additional, Bortnik, J., additional, Zhang, X.‐J., additional, Li, J., additional, Baker, D. N., additional, Reeves, G. D., additional, Spence, H. E., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Hospodarsky, G. B., additional, Blake, J. B., additional, Fennell, J. F., additional, Kanekal, S. G., additional, Angelopoulos, V., additional, Green, J. C., additional, and Goldstein, J., additional

Published
2016
Full Text
View/download PDF

189. Simulation of energy‐dependent electron diffusion processes in the Earth's outer radiation belt

Author

Ma, Q., primary, Li, W., additional, Thorne, R. M., additional, Nishimura, Y., additional, Zhang, X.‐J., additional, Reeves, G. D., additional, Kletzing, C. A., additional, Kurth, W. S., additional, Hospodarsky, G. B., additional, Henderson, M. G., additional, Spence, H. E., additional, Baker, D. N., additional, Blake, J. B., additional, Fennell, J. F., additional, and Angelopoulos, V., additional

Published
2016
Full Text
View/download PDF

191. Ring current electron dynamics during geomagnetic storms based on the Van Allen Probes measurements

Author

Zhao, H., primary, Li, X., additional, Baker, D. N., additional, Claudepierre, S. G., additional, Fennell, J. F., additional, Blake, J. B., additional, Larsen, B. A., additional, Skoug, R. M., additional, Funsten, H. O., additional, Friedel, R. H. W., additional, Reeves, G. D., additional, Spence, H. E., additional, Mitchell, D. G., additional, and Lanzerotti, L. J., additional

Published
2016
Full Text
View/download PDF

192. Solar modulation of the deep space galactic cosmic ray lineal energy spectrum measured by CRaTER, 2009–2014

Author

Zeitlin, C., primary, Case, A. W., additional, Schwadron, N. A., additional, Spence, H. E., additional, Mazur, J. E., additional, Joyce, C. J., additional, Looper, M. D., additional, Jordan, A., additional, Rios, R. R., additional, Townsend, L. W., additional, Kasper, J. C., additional, Blake, J. B., additional, Smith, S., additional, Wilson, J., additional, and Iwata, Y., additional

Published
2016
Full Text
View/download PDF

195. Characterization and Evolution of Radiation Belt Electron Energy Spectra Based on the Van Allen Probes Measurements

Author

Zhao, H., Johnston, W. R., Baker, D. N., Li, X., Ni, B., Jaynes, A. N., Kanekal, S. G., Blake, J. B., Claudepierre, S. G., Reeves, G. D., and Boyd, A. J.

Abstract

Based on the measurements of ~100‐keV to 10‐MeV electrons from the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron and Proton Telescope (REPT) on the Van Allen Probes, the radiation belt electron energy spectra characterization and evolution have been investigated systematically. The results show that the majority of radiation belt electron energy spectra can be represented by one of three types of distributions: exponential, power law, and bump‐on‐tail (BOT). The exponential spectra are generally dominant in the outer radiation belt outside the plasmasphere, power law spectra usually appear at high L‐shells during injections of lower‐energy electrons, and BOT spectra commonly dominate inside the plasmasphere at L>2.5 during relatively quiet times. The main features of three types of energy spectra have also been revealed. Specifically, for the BOT energy spectrum, the energy of local flux maximum usually ranges from approximately hundreds of keV to several MeV and the energy of local flux minimum varies from ~100 keV to ~MeV, both increasing as L‐shell decreases, confirming the plasmaspheric hiss wave scattering to be the main mechanism forming the BOT energy spectra. Statistical results using 4‐year observations from the Van Allen Probes on the relation between energy spectra and plasmapause location also show that the plasmasphere plays a critical role in shaping radiation belt electron energy spectrum: the peak location of BOT energy spectra is ~1 L‐shell inside the minimum plasmapause, where BOT energy spectra mostly form in ~1–2 days as a result of hiss wave scattering. Most radiation belt electron energy spectra can be represented by one of three distributions: exponential, power law, and bump‐on‐tailExponential spectra dominate outside the plasmasphere; power law spectra often appear at high L during injections of lower‐energy electronsBump‐on‐tail spectra dominate inside the plasmasphere at L<2.5 and are caused by hiss wave scattering

Published
2019
Full Text
View/download PDF

196. Delayed Arrival of Energetic Solar Particles at MMS on 16 July 2017

Author

Blake, J. B., Fennell, J. F., Turner, D. L., Cohen, I. J., and Mauk, B. H.

Abstract

A shock in the solar wind was observed shortly after 05:00 by heliospheric spacecraft stationed at L1. Behind the shock, protons and electrons in the tens to hundreds of keV energy range were found to be enhanced several‐fold. The shock reached the Earth precisely at 06:00 and was detected by particle sensors aboard GOES and ARTEMIS, and by ground‐based magnetometers. In addition, the arrival of the shock was seen promptly by the magnetometer investigation aboard MMS, which at the time was located 16 REdown the geomagnetic tail. However, the arrival of the energetic particles at MMS was delayed for ~23 min, and first arrived moving earthward up the geomagnetic tail. Timing considerations between the solar wind speed and the energetic particles indicated that the solar particles first gained access to field lines connected to MMS around 115 REdownstream. Once the shock and its entrained solar particles passed the access region, the solar particles were no longer seen. A shock arrived at the Earth at 06:00 on 16 July 2017 behind which was a region of increased solar energetic particles as observed by several near‐Earth spacecraftTwenty‐three minutes later, MMS observed Earth‐directed particles in the magnetotail with the same composition, spectra, and time profilesThe sum of the observations indicate that there must have been a reconnection point located around 100 RE downstream of the Earth giving access to the magnetotail

Published
2019
Full Text
View/download PDF

197. Plasmaspheric hiss waves generate a reversed energy spectrum of radiation belt electrons

Author

Zhao, H., Ni, B., Li, X., Baker, D. N., Johnston, W. R., Zhang, W., Xiang, Z., Gu, X., Jaynes, A. N., Kanekal, S. G., Blake, J. B., Claudepierre, S. G., Temerin, M. A., Funsten, H. O., Reeves, G. D., and Boyd, A. J.

Abstract

Highly energetic electrons are trapped in the magnetic field of Earth’s radiation belts. The physical mechanisms driving the dynamics of the Van Allen belts can be understood from the electron’s energy spectrum, which is believed to be steeply falling with increasing energy. This view has been prevalent for the past 60 years since the energy spectra were first measured. Here, we report the observation of a reversed energy spectrum with abundant high-energy and fewer low-energy electrons spanning from hundreds of keV to around two MeV in electron energy in data collected with NASA’s Van Allen Probes. We find that this spectrum dominates inside the plasmasphere—a dense cold plasma region co-rotating with the Earth. Using two-dimensional Fokker–Planck diffusion simulations with a time-dependent, data-driven model of hiss waves in the plasmasphere, we demonstrate that the formation of the reversed spectrum is explained by the scattering of hiss waves. The results have important implications for understanding the distributions of charged particles and wave–particle interactions in magnetized plasmas throughout the solar system and beyond.

Published
2019
Full Text
View/download PDF

198. Observation of relativistic electron microbursts in conjunction with intense radiation belt whistler-mode waves

Author

Kersten, K., Cattell, C. A., Breneman, A., Goetz, K., Kellogg, P. J., Wilson, L. B., Wygant, J. R., Blake, J. B., Looper, M. D., and Roth, I.

Subjects
Physics - Space Physics, Physics::Space Physics, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Space Physics (physics.space-ph), Physics::Atmospheric and Oceanic Physics
Abstract

We present multi-satellite observations indicating a strong correlation between large amplitude radiation belt whistler-mode waves and relativistic electron precipitation. On separate occasions during the Wind petal orbits and STEREO phasing orbits, Wind and STEREO recorded intense whistler-mode waves in the outer nightside equatorial radiation belt with peak-to-peak amplitudes exceeding 300 mV/m. During these intervals of intense wave activity, SAMPEX recorded relativistic electron microbursts in near magnetic conjunction with Wind and STEREO. The microburst precipitation exhibits a bursty temporal structure similar to that of the observed large amplitude wave packets, suggesting a connection between the two phenomena. Simulation studies corroborate this idea, showing that nonlinear wave--particle interactions may result in rapid energization and scattering on timescales comparable to those of the impulsive relativistic electron precipitation., This paper has been withdrawn by the authors

Published
2011

200. Ultra-low-frequency wave-driven diffusion of radiation belt relativistic electrons

Author

Su, Zhenpeng, primary, Zhu, Hui, additional, Xiao, Fuliang, additional, Zong, Q.-G., additional, Zhou, X.-Z., additional, Zheng, Huinan, additional, Wang, Yuming, additional, Wang, Shui, additional, Hao, Y.-X., additional, Gao, Zhonglei, additional, He, Zhaoguo, additional, Baker, D. N., additional, Spence, H. E., additional, Reeves, G. D., additional, Blake, J. B., additional, and Wygant, J. R., additional

Published
2015
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results