Affiliation of Author(s):航天学院
Journal:GEOPHYSICAL RESEARCH LETTERS
Key Words:VAN ALLEN PROBES COMET GRIGG-SKJELLERUP NONLINEAR-INTERACTIONS INNER MAGNETOSPHERE CRRES OBSERVATIONS CYCLOTRON WAVES NEWBORN IONS ELECTRONS PLASMAPAUSE INSTABILITY
Abstract:Hydrogen band electromagnetic ion cyclotron (EMIC) waves have received much attention recently because they are found to frequently span larger spatial areas than the other band EMIC waves. Using test particle simulations, we study the nonlinear effects of hydrogen band EMIC waves on ring current H+ ions. A dimensionless parameter R is used to characterize the competition between wave-induced and adiabatic motions. The results indicate that there are three regimes of wave-particle interactions for typical 35 keV H+ ions at L = 5: diffusive (quasi-linear) behavior when alpha(eq) <= 35 degrees (R >= 2.45), the nonlinear phase trapping when 35 degrees < alpha(eq) < 50 degrees (0.75 < R < 2.45), and both the nonlinear phase bunching and phase trapping when alpha(eq) >= 50 degrees (R <= 0.75). The phase trapping can transport H+ ions toward large pitch angle, while the phase bunching has the opposite effect. The phase-trapped H+ ions can be significantly accelerated (from 35 keV to over 500 keV) in about 4 min and thus contribute to the formation of high energy components of ring current ions. The results suggest that the effect of hydrogen band EMIC waves is not ignorable in the nonlinear acceleration and resonance scattering of ring current H+ ions.
ISSN No.:0094-8276
Translation or Not:no
Date of Publication:2017-12-16
Co-author:Zhai, Hao,Gao, Zhuxiu
Correspondence Author:王志强
Date of Publication:2017-12-16