Climatology Of High-Beta Plasma Measurements In Earth'S Inner Magnetosphere

Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high-resolution measurements of Earth's ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high-beta(beta) plasma events (defined here as beta > 1) as measured by the RBSPICE instrument in the similar to 45keV to similar to 600keV proton energy range in the inner magnetosphere (L < 5.8) has been constructed. In this paper we report this climatology of such high-beta plasma occurrences, durations, and their general characteristics. Specifically, we show that most high-beta events in the RBSPICE energy range are associated with postdusk/premidnight sector particle injections or plasma patches and can last from minutes to hours. While most of these events have a less than 2, there are a number of observations reaching greater than 4. Other observations of particular note are high-beta events during relatively minor geomagnetic storms and examples of very long duration high-beta plasmas. We show that high-beta plasmas are a relatively common occurrence in the inner magnetosphere during both quiet and active times. As such, the waves generated by these plasmas may have an underappreciated role in the inner magnetosphere, and thus the study of these plasmas and their instabilities may be more important than has been currently addressed.