"Dynamics of relativistic electrons in the Earth's radiation belts: energization and loss mechanisms"

ABSTRACT : Current models of electron energization in the Earth's magnetosphere may be broadly classified into two types. One class of models emphasize particle transport process such as enhanced radial diffusion as the domninant process and the second class invokes in-situ processes such as resonant or stochastic wave particle interactions. Wave particle interactions are also invoked as a mechanisms for relativistic electron loss. Relativistic electron flux variability is a balance between the processes of loss and energization. A major open scientific question is to quantify the relative contribution of these processes under specific driver conditions.

We present observations of relativistic electrons made by spacecraft such as SAMPEX, POLAR, GOES, HEO and LANL geosynchronous spacecraft, specifically the measurements of electron spectra and time scales of flux decay, and isotropization during electron energization events. We discuss the nature of seasonal and solar cycle dependence upon electron energization characteristics. These results provide useful constraints on the models of electron energization.

Energetic upflowing ions: The quiet time problems

The Role of Storm-time Pc5 Waves in Radial Transport of Radiation Belt Electrons

Abstract:
Earth's outer radiation belt is populated by relativistic electrons that produce a complex dynamical response to varying geomagnetic activity. One fundamental process defining global state of the belt is radial transport of electrons across their drift shells. In this study we investigate whether storm-time Pc5 waves are important as a mechanism of electron transport. Our analysis is based on satellite data analysis, analytical theory and numerical simulations. Storm-time Pc5 waves are driven by low frequency instabilities of ring current plasma (e.g. drift-mirror mode). Theoretical and observational analysis suggest that these waves propagate westward in a slow magnetosonic mode together with their energy source – ring current ions, are spatially localized in magnetic local time, and have high azimuthal wave numbers of 40-120. Subsequently these waves do not exhibit drift resonance with radiation belt electrons and have not been included in recent studies of radial transport mechanisms. Our test-particle analysis suggests that storm-time Pc5s can still be a very efficient driver of radial transport via non-resonant electron scattering by turbulent wave fields.