Statistical analysis of ground-based chorus observations during geomagnetic storms

Chorus observations from two ground-based, Antarctic receiving stations are analyzed for a set of geomagnetic storms from 2000 to 2010. Superposed epoch analysis is performed together with statistical hypothesis testing to determine whether the observed quantities (geomagnetic indices, outer belt energetic electron fluxes, and chorus properties) are statistically significantly different as functions of storm phase, storm size, and storm type. Waves generated in the outer dayside magnetosphere and observed on the ground at South Pole Station are suppressed during main phase and are statistically unchanged from random intervals during recovery phase. Waves generated in the inner magnetosphere and observed on the ground at Palmer Station are significantly enhanced during storm main phase and for about 3 days into recovery. During main phase, there are larger enhancements in chorus occurrence, amplitude, and frequency extent as observed at Palmer during larger storms. During recovery phase, there are larger enhancements in chorus occurrence, amplitude, and frequency extent as observed at Palmer during larger storms and during storms where the average rate of electron flux increase, averaged across the outer belt, is higher.