Inner Belt Electron Decay Timescales: A Comparison of Van Allen Probes and DREAM3D Losses Following the June 2015 Storm

NASA's Van Allen Probes observed significant, long‐lived fluxes of inner belt electrons up to ∼1 MeV after geomagnetic storms in March and June 2015. Reanalysis of Magnetic Electron Ion Spectrometer (MagEIS) data with improved background correction showed a clearer picture of the relativistic electron population that persisted through 2016 and into 2017 above the Fennell et al. (2015, https://doi.org/10.1002/2014gl062874) limit. The intensity and duration of these enhancements allow estimation of decay timescales for comparison with simulated decay rates and theoretical lifetimes. We compare decay timescales from these data and DREAM3D simulations based on them using geomagnetic activity‐dependent pitch angle diffusion coefficients derived from plasmapause‐indexed wave data (Malaspina et al., 2016, https://doi.org/10.1002/2016gl069982, 2018, https://doi.org/10.1029/2018gl078564) and phase space densities derived from MagEIS observations. Simulated decay rates match observed decay rates more closely than the theoretical lifetime due to significantly nonequilibrium pitch angle distributions in simulation and data. We conclude that nonequilibrium effects, rather than a missing diffusion or loss process, account for observed short decay rates.

[1]  J. Ripoll,et al.  Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation , 2021, Frontiers in Astronomy and Space Sciences.

[2]  G. Reeves,et al.  The Magnetic Electron Ion Spectrometer: A Review of On-Orbit Sensor Performance, Data, Operations, and Science , 2021, Space Science Reviews.

[3]  S. Morley,et al.  spacepy/spacepy: 0.2.2 , 2020 .

[4]  Y. Shprits,et al.  A Comparison of Radial Diffusion Coefficients in 1‐D and 3‐D Long‐Term Radiation Belt Simulations , 2020, Journal of Geophysical Research: Space Physics.

[5]  T. O'Brien,et al.  Empirically Estimated Electron Lifetimes in the Earth's Radiation Belts: Van Allen Probe Observations , 2020, Geophysical research letters.

[6]  T. O'Brien,et al.  Empirically Estimated Electron Lifetimes in the Earth's Radiation Belts: Comparison With Theory , 2020, Geophysical research letters.

[7]  G. Cunningham,et al.  Observations and Fokker‐Planck Simulations of the L‐Shell, Energy, and Pitch Angle Structure of Earth's Electron Radiation Belts During Quiet Times , 2019, Journal of Geophysical Research: Space Physics.

[8]  H. Spence,et al.  A Revised Look at Relativistic Electrons in the Earth's Inner Radiation Zone and Slot Region , 2019, Journal of geophysical research. Space physics.

[9]  K. M. Laundal,et al.  Snakes on a Spaceship—An Overview of Python in Heliophysics , 2018, Journal of Geophysical Research: Space Physics.

[10]  Xiangning Chu,et al.  Variation in Plasmaspheric Hiss Wave Power With Plasma Density , 2018, Geophysical Research Letters.

[11]  G. Cunningham,et al.  Neoclassical Diffusion of Radiation‐Belt Electrons Across Very Low L‐Shells , 2018 .

[12]  F. Vuyst,et al.  The analytical solution of the transient radial diffusion equation with a nonuniform loss term , 2017 .

[13]  J. Bortnik,et al.  The distribution of plasmaspheric hiss wave power with respect to plasmapause location , 2016 .

[14]  J. Bortnik,et al.  New chorus wave properties near the equator from Van Allen Probes wave observations , 2016 .

[15]  G. Reeves,et al.  Effects of whistler mode hiss waves in March 2013 , 2015 .

[16]  G. Reeves,et al.  A background correction algorithm for Van Allen Probes MagEIS electron flux measurements , 2015 .

[17]  D. Baker,et al.  Van Allen Probes show that the inner radiation zone contains no MeV electrons: ECT/MagEIS data , 2015 .

[18]  Y. Chen,et al.  On long decays of electrons in the vicinity of the slot region observed by HEO3 , 2015 .

[19]  D. Baker,et al.  Event‐specific chorus wave and electron seed population models in DREAM3D using the Van Allen Probes , 2014 .

[20]  Vladimir Truhlik,et al.  The International Reference Ionosphere 2012 – a model of international collaboration , 2014 .

[21]  David G. Sibeck,et al.  Science Objectives and Rationale for the Radiation Belt Storm Probes Mission , 2012, Space Science Reviews.

[22]  Enrico Camporeale,et al.  Modeling radiation belt electron dynamics during GEM challenge intervals with the DREAM3D diffusion model , 2013 .

[23]  H. Spence,et al.  The Magnetic Electron Ion Spectrometer (MagEIS) Instruments Aboard the Radiation Belt Storm Probes (RBSP) Spacecraft , 2013 .

[24]  D. Crawford,et al.  The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on RBSP , 2013 .

[25]  R. Selesnick.  Atmospheric scattering and decay of inner radiation belt electrons , 2012 .

[26]  P. Ozhogin,et al.  Field-aligned distribution of the plasmaspheric electron density: An empirical model derived from the IMAGE RPI measurements , 2012 .

[27]  Frank E. Harris,et al.  Mathematical Methods for Physicists: A Comprehensive Guide , 2012 .

[28]  Gaël Varoquaux,et al.  Scikit-learn: Machine Learning in Python , 2011, J. Mach. Learn. Res..

[29]  Y. Shprits,et al.  Controlling effect of the pitch angle scattering rates near the edge of the loss cone on electron lifetimes , 2006 .

[30]  Yue Chen,et al.  Phase space density distributions of energetic electrons in the outer radiation belt during two Geospace Environment Modeling Inner Magnetosphere/Storms selected storms , 2006 .

[31]  Richard B. Horne,et al.  Calculation of pitch angle and energy diffusion coefficients with the PADIE code , 2005 .

[32]  Ondrej Santolik,et al.  Singular value decomposition methods for wave propagation analysis , 2003 .

[33]  D. Drob,et al.  Nrlmsise-00 Empirical Model of the Atmosphere: Statistical Comparisons and Scientific Issues , 2002 .

[34]  R. Anderson,et al.  An ISEE/Whistler model of equatorial electron density in the magnetosphere , 1992 .

[35]  Robert C. Bolles,et al.  Random sample consensus: a paradigm for model fitting with applications to image analysis and automated cartography , 1981, CACM.

[36]  H. I. West,et al.  A study of electron spectra in the inner belt , 1976 .

[37]  C. Kennel,et al.  Pitch-angle diffusion of radiation belt electrons within the plasmasphere. , 1972 .

[38]  J. Armstrong,et al.  Time history of the inner radiation zone, October 1963 to December 1968 , 1970 .

[39]  J. Allen.  Lifetimes of Geomagnetically Trapped Electrons of Several Mev Energy , 1964, Nature.

[40]  W. N. Hess,et al.  Trapped electron time histories for L = 1.18 to L = 1.30 , 1963 .

[41]  J. Borovsky,et al.  Active Experiments in Space: Past, Present, and Future , 2020, Frontiers Research Topics.

[42]  J. Ripoll,et al.  Analytical estimates of quasi-linear diffusion coefficients and electron lifetimes in the inner radiation belt , 2012 .

[43]  Josef Koller,et al.  SpacePy - A Python-based Library of Tools for the Space Sciences , 2010, SciPy.

[44]  Jay M. Albert,et al.  Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm , 2000 .

[45]  N. Herlofson,et al.  Particle Diffusion in the Radiation Belts , 1962 .