BARREL observations of a solar energetic electron and solar energetic proton event

Abstract

AbstractDuring the second Balloon Array for Radiation Belt Relativistic Electron Losses (BARREL) campaign two solar energetic proton (SEP) events were observed. Although BARREL was designed to observe X‐rays created during electron precipitation events, it is sensitive to X‐rays from other sources. The gamma lines produced when energetic protons hit the upper atmosphere are used in this paper to study SEP events. During the second SEP event starting on 7 January 2014 and lasting ∼3 days, which also had a solar energetic electron (SEE) event occurring simultaneously, BARREL had six payloads afloat spanning all magnetic local time (MLT) sectors and L values. Three payloads were in a tight array (∼2 h in MLT and ∼2 ΔL) inside the inner magnetosphere and at times conjugate in both L and MLT with the Van Allen Probes (approximately once per day). The other three payloads mapped to higher L values with one payload on open field lines for the entire event, while the other two appear to be crossing from open to closed field lines. Using the observations of the SEE and SEP events, we are able to map the open‐closed boundary. Halford et al. (2015) demonstrated how BARREL can monitor electron precipitation following an interplanetary shock created by a coronal mass ejection (ICME‐shock) arrival at Earth, while in this study we look at the SEP event precursor to the arrival of the ICME‐Shock in our cradle‐to‐grave view: from flare, to SEE and SEP events, to radiation belt electron precipitation.