Excitation of Highly Oblique Lower Band and Upper Band Chorus by a Loss Cone Feature and Temperature Anisotropy Distribution

Abstract

Abstract Recent studies have indicated that highly oblique lower band chorus could be excited by temperature anisotropy with a low‐energy electron plateau. Here we present another excitation mechanism of highly oblique lower and upper band chorus by using the simultaneous observations and numerical modeling. During 23:00–24:00 UT on 3 July 2016, Van Allen probe A observed chorus with the wave normal angle close to the resonance cone both in the lower and upper bands around L = 5.0 and MLT = 3. Enhanced flux and pitch angle anisotropy of energetic electrons were observed in the same spatial region. Calculations of chorus growth rates show that highly oblique chorus waves can be excited by the energetic electrons with a loss cone feature and distinct temperature anisotropy, particularly more efficient in the presence of a low‐energy plateau. The temperature anisotropy for the oblique upper band is higher than that for the lower band.

Keywords

• highly oblique chorus
• wave‐particle interaction
• RBSP results
• radiation belts