The Anatomy of a Storm

Murphy, Kyle

The Anatomy of a Storm

Monday, 5 March 2018: 11:45

Longshot and Bogey (Hotel Quinta da Marinha)

Kyle R Murphy¹, Ian Robert Mann², David G Sibeck¹, Jonathan Rae³, Clare Watt⁴, Alex J Boyd⁵, Drew L. Turner⁶, Shrikanth G Kanekal⁷, Seth G Claudepierre⁸, Daniel N Baker⁹, Harlan E. Spence¹⁰, Geoffrey D Reeves¹¹, J Bernard Blake⁸ and Joseph F. Fennell⁸, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)Univ Alberta, Edmonton, AB, Canada, (3)University College London, Mullard Space Science Laboratory, London, United Kingdom, (4)University of Reading, Reading, United Kingdom, (5)New Mexico Consortium, Los Alamos, NM, United States, (6)Aerospace Corporation, SPACE SCIENCES DEPARTMENT, Los Angeles, CA, United States, (7)Heliophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, United States, (8)Aerospace Corporation, Los Angeles, CA, United States, (9)LASP, University of Colorado at Boulder, Boulder, CO, United States, (10)Solar System Exploration Research Virtual Institute, NASA Ames Research Center, Moffett Field, CA, United States, (11)Los Alamos National Laboratory, Los Alamos, NM, United States

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Abstract:

Despite recent advances in understanding the nature of competing storm-time electron loss and acceleration processes the dynamics of the outer radiation belt remain poorly understood; the outer radiation belt can exhibit either no change, an enhancement, or depletion in radiation belt electrons. Using a new analysis of the total radiation belt electron content, calculated from the Van Allen probes phase space density (PSD), we statistically analyze the time-dependent and global response of the outer radiation belt during storms. We demonstrate that by removing adiabatic effects there is a clear and repeatable sequence of events in storm-time radiation belt electron dynamics. Namely, the relativistic (μ=1000 MeV/G) and ultra-relativistic (μ=4000 MeV/G) electron populations can be separated into two phases; an initial phase dominated by loss followed by a second phase dominated by acceleration. At lower energies, the radiation belt seed population of electrons (μ=150 MeV/G) shows no evidence of loss but rather a net enhancement during storms. Further, we investigate the dependence of electron dynamics as a function of the second adiabatic invariant, K. These results demonstrate a global coherency in the dynamics of the source, relativistic and ultra-relativistic electron populations as function of the second adiabatic invariant K. This analysis demonstrates two key aspects of storm-time radiation belt electron dynamics. First, the radiation belt responds repeatably to solar wind driving during geomagnetic storms. Second, the response of the radiation belt is energy dependent, relativistic electrons behaving differently than lower energy seed electrons. These results have important implications in radiation belt research. In particular, the repeatability in electron dynamics coupled with observations of processes leading to electron loss (EMIC waves) and acceleration (VLF or ULF waves) can be used to diagnose the relative importance of physical processes in radiation belt dynamics during storms.