SPRG Seminars
March 6, 2012:
"Relativistic Electron Precipitation and the BARREL Experiment"
Robyn Millan, Dartmouth College
BARREL is a multiple-balloon investigation designed to 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 empty the radiation belts during the main phase of some geomagnetic storms and is also observed during relatively low geomagnetic activity levels. Antarctic balloon campaigns will be conducted during the Austral summers (January-February) of 2013 and 2014. During each campaign, a total of 20 small (∼20 kg) balloon payloads will be successively launched to maintain an array of payloads extending across up to 8 hours of magnetic local time in the region that magnetically maps to the radiation belts.
Each balloon carries an X-ray spectrometer to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in the 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 comprehensive in situ measurements of both plasma waves and energetic particles are available. The combination of BARREL with the in situ measurements from RBSP, THEMIS, and other missions provides a unique opportunity to study the wave-particle interactions believed to be responsible for the precipitation, and BARREL will characterize the spatial scale of precipitation at relativistic energies.