Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density. Issue 2 (1st February 2018)

• Record Type: Journal Article
• Authors: Degeling, A. W.; Rae, I. J.; Watt, C. E. J.; Shi, Q. Q.; Rankin, R.; Zong, Q.‐G.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 2(2018)
• Page Start: 1086
• Page End: 1099
• Publication Date: 2018-02-01
• Subjects: ULF waves -- convection -- plasmaspheric drainage plume -- radiation belts -- inner magnetosphere; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA024874
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: 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 Alfvén 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 3‐D 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 (VollandStern) 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 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. Key Points: ULF wave accessibility to the inner magnetosphere depends on plasmaspheric density structure generated during periods of strong convection A 3‐D MHD model for ULF waves shows that eigenmodes are excited within plasmaspheric drainage plume density structures This provides a pathway for radiation belt energization by ULF waves at lower L shell than would otherwise be possible