Banded electron structure formation in the inner magnetosphere

Abstract

Abstract. Banded electron structures in energy-time spectrograms have been observed in the inner magnetosphere concurrent with a sudden relaxation of geomagnetic activity. In this study, the formation of these banded structures is considered with a global, bounce-averaged model of electron transport, and it is concluded that this structure is a natural occurrence when plasma sheet electrons are captured on closed drift paths near the Earth followed by an extended period of quiet time for more than a day. These bands do not appear unless there is capture of plasma sheet electrons; convection along open drift paths making one pass around the Earth do not have time to develop this feature. The separation of high-energy bands from the injected population due to the preferential advection of the gradient-curvature drift creates spikes in the energy distribution above a keV, which overlap to form a series of bands in energy. The lowest band is the bulk of the injected population in the sub-keV energy range. Using the Kp history for an observed banded structure event, a cloud of plasma sheet electrons is captured and the formation of their distribution function is examined.

STEVE and the Picket Fence: Evidence of Feedback‐Unstable Magnetosphere‐Ionosphere Interaction

“…Such electrons are not anything unknown (e.g., Burke et al, ; Pedersen et al, ). They originate from early substorm injections and remain trapped during the substorm/storm recovery (Burke et al, ; Liemohn et al, ). Their presence with two SAID channels can be understood using the observation that the inner boundary of the substorm plasma sheet is controlled by the plasmapause (e.g., Mishin, ), while the plasmapause is controlled by the cross‐tail, , and SAID/SAPS electric fields (Goldstein et al, ).…”

Observations of structured optical emissions and particle precipitation equatorward of the traditional auroral oval

“…When E C decreases, the separatrix moves outward. As a result, substorm‐injected electrons penetrate into the previously forbidden plasmasphere and, after being trapped, gradient‐drift clockwise [ Burke et al , 1995; Liemohn et al , 1998]. Their precipitation is due mainly to interaction with whistler mode waves (plasmaspheric hiss).…”

Solar wind‐driven variations of electron plasma sheet densities and temperatures beyond geostationary orbit during storm times

“…Several modeling attempts have been made [Jordanova and Miyoshi, 2005;Miyoshi et al, 2006;Chen et al, 2006;Jordanova et al, 2014]. The electron flux at these low energies is largely determined by convective and substorm-associated electric fields and varies significantly with geomagnetic activity driven by the solar wind [Mauk and Meng, 1983;Kerns et al, 1994;Liemohn et al, 1998;Ganushkina et al, 2013aGanushkina et al, , 2013b. Inward electron transport includes also radial diffusion and excites plasma wave instabilities that give rise to local electron acceleration and electron precipitation into the atmosphere.…”