Storm Time Radiation Belt Electron Energization Characteristics Using The WINDMI Model

Radiation Belt Storm Probes (RBSP) data show that seed electrons generated by substorm injections appear to play a significant role in amplifying chorus waves in the magnetosphere. The wave-particle interaction then leads to rapid heating and acceleration of the electrons to 10's to 100'sof keV energies [1], [2], [3], [4]. These electrons are injected into the outer Van Allen zones [5]. In this work, we use the WINDMI model of the nightside magnetosphere to generate a proxy index that tracks electron energization in the radiation belts during storm time. The electron energy ranges analyzed are 40 KeV to 4.2 MeV. The WINDMI model has as an output, a region 1 field-aligned current proportional to the westward auroral electrojet. This field-aligned current is integrated to generate an E Index, or Electron Energization Index, incorporating a variable time delay and energy loss rate. The resulting linear differential equation is coupled to the WINDMI model, and we used this to study a set of 8 events. The E index is compared to RBSP data and GOES data.We initially analyzed a dataset of 27 magnetic storms from the year 2014 to 2017. These events occurred over diverse durations and were of different intensities. The storms were analyzed with respect to the SML index and the AL index. Out of 27, eight of these storms were picked for further analysis. These were were 17-27 March 2015, 21-29 June 2015, 6-9 August 2017, 7-11 May 2016, 23-31 October 2016, 14-21 March 2015, 5-12 October 2015 and 7-12 November 2017. 7-11 May 2016 and 14-21 March 2015 storms have been dropped because they show similar signatures to the other storms presented. Our results show that the energy gain and loss in the radiation belts can be captured in some cases via storm time substorm activity as represented by the AL and SML indices.References1) Reeves, G. D., et al. ( 2013), Electron acceleration in the heart of the Van Allen Radiation Belts, Science, 341( 6149), 991 994, doi:10.1126/science.1237743.2) Foster, J. C., et al. ( 2014), Prompt energization of relativistic and highly relativistic electrons during substorm intervals: Van Allen Probes observation, Geophys. Res. Lett., 41, 20 25, doi:10.1002/2013GL058438 .3) Baker, D. N., et al. ( 2014a), Gradual diffusion and punctuated phase space density enhancements of highly relativistic electrons: Van Allen Probes observations, Geophys. Res. Lett., 41, 1351 1358, doi:10.1002/2013GL058942 .4) Kanekal, S. G., et al. ( 2015), Relativistic electron response to the combined magnetospheric impact of a coronal mass ejection overlapping with a high speed stream: Van Allen Probes observations, J. Geophys. Res. Space Physics, 120, 7629 7641, doi:10.1002/2015JA021395 .5) Jaynes, A. N., et al. ( 2015), Source and seed populations for relativistic electrons: Their roles in radiation belt changes, J. Geophys. Res. Space Physics, 120, 7240 7254, doi:10.1002/2015JA021234 .