2011 SuperDARN Workshop       

Studying Relativistic Electron Precipitation with BARREL

Robyn Millan
Department of Physics and Astronomy, Dartmouth College, Hanover, NH, USA

abstract. BARREL (Balloon Array for RBSP Relativistic Electron Precipitation) is a multiple-balloon investigation that will study electron losses from Earth's Radiation Belts. Atmospheric losses of relativistic electrons play an important role in radiation belt dynamics; precipitation into the atmosphere can deplete the radiation belts during the main phase of some geomagnetic storms and is also observed during relatively low geomagnetic activity levels. BARREL will consist of Antarctic balloon campaigns conducted in Austral summers of 2012 and 2013. During each campaign, a total of 20 small (~20 kg) balloon payloads will be launched to an altitude of 30-35 km to maintain an array of payloads extending across up to 8 hours of magnetic local time. Each balloon will carry a NaI scintillator to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in Earth's atmosphere, and a DC magnetometer to explore the nature of observed Ultra Low Frequency temporal modulations of precipitation. We present an overview of the BARREL investigation which will provide the first balloon measurements of relativistic electron precipitation while in situ measurements of both plasma waves and energetic particle distributions are available. The combination of BARREL with in situ measurements from RBSP and THEMIS, and with ground-based measurements, provides a unique opportunity to study the wave-particle interactions believed to be responsible for the precipitation.

Sakaguchi KaoriNICT Japan