In-Situ and Ground-based Observations of Pc1 Pearl Pulsations

Pc1 pearl pulsations have been observed by ground-based magnetometers since the mid-1930s, and have since been identified as a class of electromagnetic ion cyclotron waves. While they make up a significant fraction of total observed Pc1 wave activity, there exist few direct observations by orbiting satellites. We present here simultaneous observations of a Pc1 pearl wave by the Van Allen Probes B spacecraft as well as observation stations on the island of Svalbard (Ny Alesund, Longyearbyen, and Hornsund) with which the spacecraft was in close conjunction. The wave is seen by Van Allen Probe B at 0600 on November 11th of 2012 in the He+ gyrofrequency band. Its short duration compared to the ground station observations (0430 - 0800 UT) suggests the narrow spacial extent of the source region. We discuss merits of current competing generation mechanisms in light of this new observation. Simultaneous observations of Pc1 pearl pulsations by ground-based magnetometers in Svalbard and the Van Allen Probes B spacecraft. In-situ observations observed the wave in the He+ gyrofrequency band.