9 results on '"Barnes, Robin J."'
Search Results
2. Extended metric validation of a semi-physical Space Weather Modeling Framework conductance model on field-aligned current estimations.
- Author
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Hathaway, Erika Y., Mukhopadhyay, Agnit, Liemohn, Michael W., Keebler, Timothy, Anderson, Brian J., Vines, Sarah K., and Barnes, Robin J.
- Subjects
STANDARD deviations ,APPLIED sciences ,INTERPLANETARY magnetic fields ,MAGNETIC storms ,WEATHER forecasting - Abstract
This article discusses a study that validates the MAGNetosphere-Ionosphere-Thermosphere (MAGNIT) model against AMPERE measurements of field-aligned currents (FACs) during the "Galaxy 15" space weather event. The study compares the performance of three ionosphere electrodynamic models and finds that MAGNIT exhibits slightly improved predictions compared to other models. The article provides valuable information on auroral precipitation sources and their impact on FACs, which can be used to enhance the model. The study also analyzes various metrics and provides recommendations for optimizing the model's performance. [Extracted from the article]
- Published
- 2024
- Full Text
- View/download PDF
3. Electrodynamic Context of Magnetopause Dynamics Observed by Magnetospheric Multiscale
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Anderson, Brian J, Russell, Christopher T, Strangeway, Robert J, Plaschke, Ferdinand, Magnes, Werner, Fischer, David, Korth, Haje, Merkin, Viacheslav G, Barnes, Robin J, Waters, Colin L, Cohen, Ian J, Westlake, Joseph H, Mauk, Barry H, Leinweber, Hannes K, Gershman, Daniel J, Giles, Barbara L, Le, Guan, Torbert, Roy B, and Burch, James L
- Subjects
Space Sciences (General) - Abstract
Magnetopause observations by Magnetospheric Multiscale (MMS) and Birkeland currents observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment are used to relate magnetopause encounters to ionospheric electrodynamics. MMS magnetopause crossings on 15 August and 19 September 2015 occurred earthward of expectations due to solar wind ram pressure alone and coincided with equatorward expansion of the Birkeland currents. Magnetopause erosion, consistent with expansion of the polar cap, contributed to the magnetopause crossings. The ionospheric projections of MMS during the events and at times of the magnetopause crossings indicate that MMS observations are related to the main path of flux transport in one case but not in a second. The analysis provides a way to routinely relate in situ observations to the context of in situ convection and flux transport.
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- 2016
- Full Text
- View/download PDF
4. Iridium Communications Satellite Constellation Data for Study of Earth's Magnetic Field.
- Author
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Anderson, Brian J., Angappan, Regupathi, Barik, Ankit, Vines, Sarah K., Stanley, Sabine, Bernasconi, Pietro N., Korth, Haje, and Barnes, Robin J.
- Subjects
GEOMAGNETISM ,GEOMAGNETIC variations ,MAGNETIC fields ,BIRKELAND currents ,ATMOSPHERIC electricity ,GEOMAGNETIC field lines - Abstract
Characterization of Earth's magnetic field is key to understanding dynamics of the core. We assess whether Iridium Communications magnetometer data can be used for this purpose since. The 66 Iridium satellites are in 86° inclination, 780 km altitude, circular orbits, with 11 satellites in each of six orbit planes. In one day the constellation returns 300,000 measurements spanning the globe with <2° spacing. We used data from January 2010 through November 2015, and compared against International Geomagnetic Reference Field (IGRF-11) to inter-calibrate all data to the same model. Geomagnetically quiet 24-h intervals were selected using the total Birkeland current, auroral electrojet, and ring current indices. The z-scores for these quantities were combined and the quietest 16 intervals from each quarter selected for analysis. Residuals between the data and IGRF-11 yield consistent patterns that evolve gradually from 2010 to 2015. Residuals for each day were binned in 9° latitude by 9° longitude and the distributions about the mean in each bin are Gaussian with 1-sigma standard errors of ~3 nT. Spherical harmonic coefficients for each quiet day were computed and time series of the coefficients used to identify artifacts at the orbit precession (8 months) and seasonal (12 months) periods and their harmonics which were then removed by notch filtering. This analysis yields time series at 800 virtual geomagnetic observatories each providing a global field map using a single day of data. The results and CHAOS 7.4 generally agree, but systematic differences larger than the statistical uncertainties are present that warrant further exploration. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
5. Packaging a Successful NASA Mission to Reach a Large Audience with a Small Budget. Earth's Dynamic Space: Solar-Terrestrial Physics and NASA's Polar Mission
- Author
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Fox, Nicola J, Goldberg, Richard, Barnes, Robin J, Sigwarth, John B, Beisser, Kerri B, Moore, Thomas E, Hoffman, Robert A, Russell, Christopher T, Scudder, Jack D, and Spann, James F
- Subjects
Space Sciences (General) - Abstract
To showcase the on-going and wide-ranging scope of the Polar science discoveries, the Polar science team has created a one-stop shop for a thorough introduction to geospace physics, in the form of a DVD with supporting website. The DVD, Earth's Dynamic Space: Solar-Terrestrial Physics & NASA's Polar Mission, can be viewed as an end-to-end product or split into individual segments and tailored to lesson plans. Capitalizing on the Polar mission and its amazing science return, the Polar team created an exciting multi-use DVD intended for audiences ranging from a traditional classroom and after school clubs, to museums and science centers. The DVD tackles subjects such as the aurora, the magnetosphere and space weather, whilst highlighting the science discoveries of the Polar mission. This platform introduces the learner to key team members as well as the science principles. Dramatic visualizations are used to illustrate the complex principles that describe Earth's dynamic space. In order to produce such a wide-ranging product on a shoe-string budget, the team poured through existing NASA resources to package them into the Polar story. Team members also created visualizations using Polar data to complement the NASA stock footage. Scientists donated their time to create and review scripts to make this a real team effort, working closely with the award winning audio-visual group at JHU/Applied Physics Laboratory. The team was excited to be invited to join NASA's Sun-Earth Day 2005 E/PO program and the DVD will be distributed as part of the supporting educational packages.
- Published
- 2004
6. Temporal and Spatial Development of Global Birkeland Currents.
- Author
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Anderson, Brian J., Olson, Cameron N., Korth, Haje, Barnes, Robin J., Waters, Colin L., and Vines, Sarah K.
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MAGNETOSPHERE ,MAGNETIC fields ,ELECTRIC currents ,GEOMAGNETISM ,INTERPLANETARY magnetic fields ,IONOSPHERE - Abstract
The development of large‐scale Birkeland currents is examined using the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), which measures global Birkeland currents continuously on 10‐min time scales. The integrated current was used to identify onsets of at least 1 MA preceded by periods of quiescence lasting at least 3 hr. The Region 1 currents do not fully form without Region 2. Rather, they develop together, first on the dayside, then on the nightside, and lastly, they fill in and intensify at all local times to form the nominal statistical pattern. The onsets are closely correlated with enhancements of magnetospheric forcing as indicated by the solar wind electric field and the orientation of the interplanetary magnetic field. Nightside onsets correspond to intensifications of the auroral electrojet as reflected in the AE index; they are delayed by ~40 min relative to the increase of the dayside current and are 2.8 times more rapid than the dayside current increase. After nightside onset, Birkeland currents expand toward dawn and dusk and merge with the dayside currents while also intensifying at all local times. The dayside current pattern depends on the sign of the interplanetary magnetic field BY. The nightside current distributions are the same for positive and negative BY and display a Harang discontinuity independent of the sign of BY. The predominant development and intensification of Birkeland currents occur after nightside onset at all local times with roughly 75% of the total current, both Regions 1 and 2, appearing after nightside onset. Plain Language Summary: This study uses data from the 66 Iridium Communications satellites to track the development of electric currents that drive aurora. These currents can turn on in less than about an hour. However, the currents can only be measured from satellites orbiting the Earth above the atmosphere, and in those orbits, satellites take about 100 min to orbit the Earth. With the Iridium constellation, we remeasure these currents every 10 min and are able to track where they start and how they grow. This happens in two steps: Currents appear first in the day where they remain. About 30 min later, new currents start near midnight and then spread toward dawn and dusk and increase until they completely encircle the poles in an oval pattern. The total current finally reaches millions of Amperes. The two‐step process implies that explosive dynamics in the magnetic tail of the Earth play a key role in creating and generating the auroral currents. This study shows that the effects they have on the temporal sequence of activity onset need to be included to predict the effects of the solar wind and solar storms on the Earth's ionosphere and upper atmosphere. Key Points: Analysis of Birkeland current growth following extended intervals of low current reveals the development sequence of the global systemCurrents begin on the dayside with both Regions 1 and 2 and do not appear on the nightside until a sudden onset about 30 min laterAt onset, nightside Regions 1 and 2 appear together, intensify, and expand to the dayside forming the complete system after about an hour [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
7. Testing the expanding-contracting polar cap paradigm.
- Author
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Sotirelis, Thomas, Keller, Mary Ruth, Liou, Kan, Smith, Daniel, Barnes, Robin J., Talaat, Elsayed, and Baker, Joseph B. H.
- Abstract
The expanding-contracting polar cap (ECPC) paradigm is tested. Under the ECPC paradigm ionospheric convection in the polar cap is driven by the combined effects of magnetic field dayside merging and nightside reconnection, as opposed to being mapped down from higher altitudes. The ECPC paradigm is tested by separately examining the cross polar cap potential when the polar cap is expanding versus contracting. The open magnetic flux is estimated from Super Dual Auroral Radar Network (SuperDARN) observations of the convection reversal boundary (CRB) made simultaneously at different local times. Sotirelis et al. (2005) established the CRB as a proxy for the open-closed boundary. The correlation of the ionospheric convection potential, determined from SuperDARN, with solar wind/interplanetary magnetic field (IMF) driving is indeed found to depend on whether the polar cap is expanding or contracting. Specifically, when the polar cap is expanding, ionospheric convection potential correlates best (0.86) with the most recent 10 min of solar wind/IMF driving (versus 0.57 for contracting). When contracting, convection potential correlates best (0.87) with 90 min averages of solar wind/IMF driving (versus 0.51 for expanding). This result is consistent with the expectations of the ECPC paradigm. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
8. Comparison of predictive estimates of high-latitude electrodynamics with observations of global-scale Birkeland currents.
- Author
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Anderson, Brian J., Korth, Haje, Welling, Daniel T., Merkin, Viacheslav G., Wiltberger, Michael J., Raeder, Joachim, Barnes, Robin J., Waters, Colin L., Pulkkinen, Antti A., and Rastaetter, Lutz
- Published
- 2017
- Full Text
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9. Dawn and dusk sector comparisons of small-scale irregularities, convection, and particle precipitation in the high-latitude ionosphere.
- Author
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Greenwald, Raymond A., Shepherd, Simon G., Sotirelis, Thomas S., Ruohoniemi, J. Michael, and Barnes, Robin J.
- Published
- 2002
- Full Text
- View/download PDF
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