First results from the BARREL 2013 campaign; Observations of precipitation on drift echo timescales

Throughout the BARREL 2013 campaign and during previous balloon missions, electron precipitation has been observed to occur on many different time scales, from millisecond microbursts to minute-long ULF time scales to tens of minutes. These longer period oscillations have not been previously examined in detail because satellite data were unavailable to identify the nature of the longer period oscillations. In this study we will present BARREL observations of precipitation along with observations of drift echoes in electron data from the MagEIS instrument on the Van Allen Probes. One example occurred on January 26, 2013 where precipitation showed an approximate 20 -minute modulation and drift echoes were observed at similar timescales in the approximately 230-350 keV electrons by MagEIS. The precipitation also shows temporal structure at faster timescales including approximately 90-second ULF modulation and millisecond microbursts. This suggest that the drift echoes may determine when there are particles available to be precipitated by some other mechanism such as scattering by VLF waves.