Analysis of Conjugate Satellite and Ground EMIC Wave Observations

Abstract

Electromagnetic ion cyclotron (EMIC) waves are transverse electromagnetic waves typically generated in the equatorial magnetosphere by anisotropic proton distributions. These waves can resonantly interact with multiple particle populations in the inner magnetosphere believed to be an important loss mechanism for both ring current ions and radiation belt electrons, as well as a cold plasma heating source. The spatiotemporal extent of wave activity is one of the key parameters used to quantify the effects of EMIC waves on magnetospheric plasma populations. However, from single-point spacecraft measurements or ground based observations alone, it is challenging to get the full picture of wave occurrence distributions. Due to a number of processes, ground and in situ observations of EMIC wave activity, specifically, its global occurrence, duration, and frequency often exhibit noticeable variations [1]. In particular, EMIC waves in the H+ frequency band are not always seen on the ground conjugately to locations of space observations [2]. In addition, ground and space EMIC wave distributions have different dependencies on local time, L shell, and geomagnetic activity, adding to the challenge of comparing measurements across these platforms [3]. Here we address this challenge by examining the relationship between EMIC wave occurrence and power on the Van Allen Probes and conjugate CARISMA ground magnetometer stations in the Canadian sector. We apply an automated wave detection algorithm to magnetometer data [4]. We present an analysis of long-term simultaneous EMIC wave observations in space and on the ground, and study wave propagation characteristics in the He+ and H+ frequency bands during different geomagnetic conditions.