A summary of the BARREL campaigns: Technique for studying electron precipitation

The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) studies the loss of energetic electrons from Earth's radiation belts. BARREL's array of slowly drifting balloon payloads was designed to capitalize on magnetic conjunctions with NASA's Van Allen Probes. Two campaigns were conducted from Antarctica in 2013 and 2014. During the first campaign in January and February of 2013, there were three moderate geomagnetic storms with SYM‐H (min) < −40 nT. Similarly, two minor geomagnetic storms occurred during the second campaign, starting in December of 2013 and continuing on into February of 2014. Throughout the two campaigns, BARREL observed electron precipitation over a wide range of energies and exhibiting temporal structure from hundreds of milliseconds to hours. Relativistic electron precipitation was observed in the dusk to midnight sector, and microburst precipitation was primarily observed near dawn. In this paper we review the two BARREL science campaigns and discuss the data products and analysis techniques as applied to relativistic electron precipitation observed on 19 January 2013.