Open AccessULF wave characteristics at geosynchronous orbit during the recovery phase of geomagnetic storms associated with strong electron acceleration
Author(s) -
Clausen L. B. N.,
Baker J. B. H.,
Ruohoniemi J. M.,
Singer H. J.
Publication year - 2011
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011ja016666
Subject(s) - physics , geosynchronous orbit , geomagnetic storm , geophysics , toroid , computational physics , wave power , wave propagation , longitudinal wave , earth's magnetic field , flux (metallurgy) , electron , magnetic field , power (physics) , plasma , optics , materials science , quantum mechanics , astronomy , metallurgy , satellite
We identified 17 geomagnetic storms between January 2007 and December 2008. Using particle measurements, each storm is classified as a high‐flux event or a low‐flux event. High‐flux events are those storms associated with enhanced flux of relativistic electrons at geosynchronous orbit, and low‐flux events show no such enhancement. We study the characteristics of ultralow frequency waves between 0 and 80 mHz during the recovery phase of the high‐flux storms using magnetic field data. By determining the wave propagation direction and magnetic perturbation direction, we are able to calculate how the power is distributed between toroidal, poloidal, and compressional wave modes. We find that on the nightside most wave power is compressional at all frequencies below 80 mHz. On the dayside compressional wave power dominates the lowest frequencies below 20 mHz; toroidal waves carry most energy between 20 and 50 mHz, and poloidal waves are associated with higher power levels between 50 and 80 mHz. This suggests that on the nightside electrons are predominantly transported and energized by mechanisms involving the compressional wave mode; on the dayside, electron energization is achieved by acceleration mechanisms involving toroidal waves and mechanisms dependent on poloidal and compressional waves.