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  • 1
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    Initial Results from the GEM Challenge on the Spacecraft Surface Charging Environment (2019)
    In:  Other Sources
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    Publication Date: 2019-06-29
    Description: Spacecraft surface charging during geomagnetically disturbed times is one of the most important causes of satellite anomalies. Predicting the surface charging environment is one prevalent task of the geospace environment models. Therefore, the Geospace Environment Modeling (GEM) Focus Group "Inner Magnetosphere Crossenergy/Population Interactions" initiated a communitywide challenge study to assess the capability of several inner magnetosphere ring current models in determining surface charging environment for the Van Allen Probes orbits during the 17 March 2013 storm event. The integrated electron flux between 10 and 50 keV is used as the metrics. Various skill scores are applied to quantitatively measure the modeling performance against observations. Results indicate that no model consistently perform the best in all of the skill scores or for both satellites. We find that from these simulations the ring current model with observational flux boundary condition and Weimer electric potential driver generally reproduces the most realistic flux level around the spacecraft. A simple and weaker VollandStern electric field is not capable of effectively transporting the same plasma at the boundary toward the Earth. On the other hand, if the ring current model solves the electric field selfconsistently and obtains similar strength and pattern in the equatorial plane as the Weimer model, the boundary condition plays another crucial role in determining the electron flux level in the inner region. When the boundary flux spectra based on magnetohydrodynamics (MHD) model/empirical model deviate from the shape or magnitude of the observed distribution function, the simulation produces poor skill scores along Van Allen Probes orbits.
    Keywords: Space Sciences (General)
    Type: GSFC-E-DAA-TN70222 , Space Weather (ISSN 1539-4956) (e-ISSN 1542-7390); 17; 2; 299-3012
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  • 2
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    An Engergetic Electron Flux Dropout Due to Magnetopause Shadowing on 1 June 2013 (2018)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We examine the mechanisms responsible for the dropout of energetic electron flux during 31 May to 1 June 2013 using Van Allen Probe (Radiation Belt Storm Probes (RBSP)) electron flux data and simulations with the Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. During the storm main phase, L-shells at RBSP locations are greater than ~8, which are connected to open drift shells. Consequently, diminished electron fluxes were observed over a wide range of energies. The combination of drift shell splitting, magnetopause shadowing, and drift loss all results in butterfly electron pitch angle distributions (PADs) at the nightside. During storm sudden commencement, RBSP observations display electron butterfly PADs over a wide range of energies. However, it is difficult to determine whether there are butterfly PADs during the storm main phase since the maximum observable equatorial pitch angle from RBSP is not larger than ~40 during this period. To investigate the causes of the dropout, the CIMI model is used as a global 4-D kinetic inner magnetosphere model. The CIMI model reproduces the dropout with very similar timing and flux levels and PADs along the RBSP trajectory for 593 keV. Furthermore, the CIMI simulation shows butterfly PADs for 593 keV during the storm main phase. Based on comparison of observations and simulations, we suggest that the dropout during this event mainly results from magnetopause shadowing.
    Keywords: Space Sciences (General)
    Type: GSFC-E-DAA-TN58324 , Journal of Geophysical Research: Space Physics (ISSN 2169-9402) (e-ISSN 2169-9402); 123; 2; 1178-1190
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  • 3
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    The Role of Ring Current on Slot Region Penetration (2006)
    In:  Other Sources
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    Publication Date: 2019-07-19
    Description: During magnetic quiet times, the inner belt, slot region and the outer belt are well defined regions. However, during some major storms, outer belt particles penetrate inward and significantly fill the slot region. In some extreme events, the outer belt particles travel through the slot and create a new belt in the inner region that persists from months to years. In this paper, we examine the role of the ring current on this radiation belt penetration into the slot region. The storm-time intensification of the ring current produces strong magnetic depression in the inner magnetosphere. This perturbation and its fluctuation enhance the radial transport and diffusion of the outer radiation belt particles. We perform kinetic and test-particle calculations to quantitatively assess the effects of the ring current field on filling of the slot region. Simulation results during major storms will be presented and discussed.
    Keywords: Space Sciences (General)
    Type: 2006 Spring AGU meeting: Coupled Dynamics of the Inner Magnetosphere; May 23, 2006 - May 26, 2006; Baltimore, MD; United States
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  • 4
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    Global Images of Trapped Ring Current Ions During Main Phase of 17 March 2015 Geomagnetic Storm as Observed by TWINS (2016)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A unique view of the trapped particles in the inner magnetosphere provided by energetic neutral atom (ENA) imaging is used to observe the dynamics of the spatial structure and the pitch angle anisotropy on a global scale during the last 6 h of the main phase of a large geomagnetic storm (minimum SYM-H 230 nT) that began on 17 March 2015. Ion flux and pressure anisotropy obtained from Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) ENA images are shown. The ion flux shows two peaks, an inner one at approximately radii 34 RE in the dusk-to-midnight sector and an outer peak at radii 89 RE prior to midnight. The inner peak is relatively stationary during the entire period with some intensification during the final steep decline in SYM-H to its minimum. The outer peak shows the significant temporal variation brightening and dimming and finally disappearing at the end of the main phase. The pressure anisotropy shows the expected perpendicular pitch angles inside of L 6 but shows parallel pitch angles at greater L values. This is interpreted as consistent with pitch angle-dependent drift as modeled in the Tsy05 magnetic field and Comprehensive Inner Magnetosphere-Ionosphere simulations. The TWINS results are compared directly with Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE)-A measurements. Using 15 min snapshots of flux and pressure anisotropy from TWINS along the path of RBSPICE-A during the 6 h focused upon in this study, the essential features displayed in the TWINS global images are supported.
    Keywords: Space Sciences (General)
    Type: GSFC-E-DAA-TN40918 , Journal of Geophysical Research: Space Physics (ISSN 2169-9380) (e-ISSN 2169-9402); 121; 7; 6509–6525
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  • 5
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    Design Overview of the DM Radio Pathfinder Experiment (2016)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We introduce the DM Radio, a dual search for axion and hidden photon dark matter using a tunable superconducting lumped-element resonator. We discuss the prototype DM Radio Pathfinder experiment, which will probe hidden photons in the 500 peV (100 kHz)-50 neV (10 MHz) mass range. We detail the design of the various components: the LC resonant detector, the resonant frequency tuning procedure, the differential SQUID readout circuit, the shielding, and the cryogenic mounting structure. We present the current status of the pathfinder experiment and illustrate it's potential science reach in the context of the larger experimental program.
    Keywords: Space Sciences (General)
    Type: GSFC-E-DAA-TN41181 , IEEE Transactions on Applied Superconductivity (ISSN 1051-8223) (e-ISSN 1558-2515); 27; 4; 1400204
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  • 6
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    The Roles of Transport and Wave-Particle Interactions on Radiation Belt Dynamics (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Particle fluxes in the radiation belts can vary dramatically during geomagnetic active periods. Transport and wave-particle interactions are believed to be the two main types of mechanisms that control the radiation belt dynamics. Major transport processes include substorm dipolarization and injection, radial diffusion, convection, adiabatic acceleration and deceleration, and magnetopause shadowing. Energetic electrons and ions are also subjected to pitch-angle and energy diffusion when interact with plasma waves in the radiation belts. Important wave modes include whistler mode chorus waves, plasmaspheric hiss, electromagnetic ion cyclotron waves, and magnetosonic waves. We investigate the relative roles of transport and wave associated processes in radiation belt variations. Energetic electron fluxes during several storms are simulated using our Radiation Belt Environment (RBE) model. The model includes important transport and wave processes such as substorm dipolarization in global MHD fields, chorus waves, and plasmaspheric hiss. We discuss the effects of these competing processes at different phases of the storms and validate the results by comparison with satellite and ground-based observations. Keywords: Radiation Belts, Space Weather, Wave-Particle Interaction, Storm and Substorm
    Keywords: Space Sciences (General)
    Type: GSFC.ABS.4320.2011 , 2011 Japan Geoscience Union Meeting/Japan Geoscience Union (JpGU); May 22, 2011 - May 27, 2011; Chiba; Japan
    Format: application/pdf
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