Fig. 1
From: Origin of two-band chorus in the radiation belt of Earth
Van Allen Probe-A orbit and observations of two-band chorus waves. a The configuration of outer and inner radiation belts that are confined by Earth’s magnetic field (the colors are not from any specific data), as well as the Van Allen Probe orbit and its position at 07:23 UT on 6 December 2015. b 80-min overview of survey-mode magnetic wave spectral intensity, showing two-band chorus waves separated by a gap around half electron gyro-frequency, which is represented by a dashed red line. c 12-second high-resolution measurements of magnetic wave spectral intensity during the time indicated by a yellow arrow in Fig. 1b, showing discrete rising-tone elements in each band. d The wave normal angles calculated from the waveform data using the Means method41, showing that the chorus waves propagate mostly at wave normal angles of 0º –30º with respect to the magnetic field
