Event‐specific chorus wave and electron seed population models in DREAM3D using the Van Allen Probes

Abstract

The DREAM3D diffusion model is applied to Van Allen Probes observations of the fast dropout and strong enhancement of MeV electrons during the October 2012 "double-dip" storm. We show that in order to explain the very different behavior in the two "dips," diffusion in all three dimensions (energy, pitch angle, and L * ) coupled with data-driven, event-specific inputs, and boundary conditions is required.Specifically, we find that outward radial diffusion to the solar wind-driven magnetopause, an event-specific chorus wave model, and a dynamic lower-energy seed population are critical for modeling the dynamics.In contrast, models that include only a subset of processes, use statistical wave amplitudes, or rely on inward radial diffusion of a seed population, perform poorly. The results illustrate the utility of the high resolution, comprehensive set of Van Allen Probes' measurements in studying the balance between source and loss in the radiation belt, a principal goal of the mission.

Geomagnetic activity and local time dependence of the distribution of ultra low-frequency wave power in azimuthal wavenumbers, <i>m</i>

“…This event has been studied in further detail in Reeves et al (2013), where the electron enhancement has been described as a clear illustration of a local acceleration mechanism for relativistic electron acceleration in the heart of the outer Van Allen belt. In particular, the 8-9 October storm not only shows a remarkable enhancement of radiation belt electrons but also a fast electron dropout preceding the enhancement, as discussed in Tu et al (2014). Magnetopause shadowing combined with enhanced outward radial diffusion could play an important role in the observed radiation belt dropout.…”

Quantification of Energetic Electron Precipitation Driven by Plume Whistler Mode Waves, Plasmaspheric Hiss, and Exohiss

“…Summers et al (2008) found that hundreds of keV seed electron population, which can be further accelerated to MeV electrons (Horne et al, 2005;Thorne et al, 2013), is subject to rapid precipitation loss due to scattering by plume whistler mode waves, thus reducing the effect of MeV electron acceleration. In spite of the importance of plume whistler mode waves, it is crucial to note that the effects of plume whistler mode waves have not been accurately incorporated into most global radiation belt modeling yet (e.g., Albert et al, 2009;Glauert et al, 2014;Li et al, 2016;Ma et al, 2018;Tu et al, 2014). In spite of the importance of plume whistler mode waves, it is crucial to note that the effects of plume whistler mode waves have not been accurately incorporated into most global radiation belt modeling yet (e.g., Albert et al, 2009;Glauert et al, 2014;Li et al, 2016;Ma et al, 2018;Tu et al, 2014).…”

Relativistic electron flux dropouts in the outer radiation belt associated with corotating interaction regions

“…Drift loss of electrons occurs when the magnetopause is compressed inward and intersects the drift path of electrons in the outer radiation belt [Shprits et al, 2006;Turner et al, 2012;Tu et al, 2013Tu et al, , 2014.…”

“…There are currently three types of loss mechanisms to explain the electron flux dropout in the outer radiation belt: adiabatic loss or "Dst effect" [Kim and Chan, 1997]; precipitation loss to the atmosphere via pitch angle scattering with plasma waves Abel and Thorne, 1998;O'Brien et al, 2003;Voss et al, 1998]; and drift loss to the magnetopause and outward radial diffusion [Brautigam and Albert, 2000;Miyoshi et al, 2003;Shprits et al, 2006;Ohtani et al, 2009;Matsumura et al, 2011;Turner et al, 2012;Tu et al, 2014].…”