Publication Date:
2018-01-11
Description:
During periods of storm activity and enhanced convection, the plasma density in the afternoon sector of the magnetosphere is highly dynamic due to the development of plasmaspheric drainage plume (PDP) structure. This significantly affects the local AlfvÃľn speed, and alters the propagation of ULF waves launched from the magnetopause. Therefore it can be expected that the accessibility of ULF wave power for radiation belt energization is sensitively dependent on the recent history of magnetospheric convection, and the stage of development of the PDP. This is investigated using a 3D model for ULF waves within the magnetosphere in which the plasma density distribution is evolved using an advection model for cold plasma, driven by a (VollandâĂŞStern) convection electrostatic field (resulting in PDP structure). The wave model includes magnetic-field day/night asymmetry, and extends to a paraboloid dayside magnetopause, from which ULF waves are launched at various stages during the PDP development. We find that the plume structure significantly alters the field line resonance (FLR) location, and the turning point for MHD fast waves, introducing strong asymmetry in the ULF wave distribution across the noon meridian. Moreover, the density enhancement within the PDP creates a waveguide or local cavity for MHD fast waves, such that eigenmodes formed allow the penetration of ULF wave power to much lower L within the plume than outside, providing an avenue for electron energization.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
