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

Abstract

During 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.

Quiet Daytime Arctic Ionospheric D Region

“…These average precipitating electron fluxes did not seem to increase very strongly with L value in their range L = 2–13 (their Figures 2, 6, 7, 9, and 10). Halford et al () observed quiet time electron precipitation fluxes which were also largely independent of L over the Antarctic polar region. They reported precipitating electron bremsstrahlung energy spectra up to several hundred keV from six BARREL high‐altitude (~30 km) balloons above the Antarctic “covering L values from the inner magnetosphere out to regions of open field lines” on 7 January 2014 during, and preceded by, a long quiet period (followed by an active period after ~16 UT).…”

The physics of space weather/solar-terrestrial physics (STP): what we know now and what the current and future challenges are

“…The recovery is associated with a multitude of physical processes associated with the loss of the energetic ring current particles: charge exchange, Coulomb collisions, wave-particle interactions and convection out the dayside magnetopause (West et al, 1972;Kozyra et al, 1997Kozyra et al, , 2006aJordanova et al, 1998;Daglis et al, 1999). A typical time for storm recovery is ∼ 10 to 24 h (Burton et al, 1975;Hamilton et al, 1988;Ebihara and Ejiri, 1998;O'Brien and McPherron, 2000;Dasso et al, 2002;Kozyra et al, 2002;Wang et al, 2003;Weygand and McPherron, 2006;Monreal MacMahon and Llop, 2008).…”

“…As one example, interplanetary shock acceleration of energetic charged particles (called "solar cosmic rays") is due to an ICME ram energy driving the fast shocks, which then transfers energy to the charged particles. Solar cosmic ray events can occur with or without magnetic storms (Halford et al, 2015(Halford et al, , 2016Foster et al, 2015). Some of the major extreme space weather topics will be addressed below.…”

Investigating energetic electron precipitation through combining ground‐based and balloon observations

“…Each wave mode has its own characteristic frequency spectrum, amplitude range, L ‐shell range, magnetic local time (MLT) range, and response to geomagnetic storm activity [e.g., Anderson et al , ; Usanova et al , ; Halford et al ., ; Li et al , ; Agapitov et al , ]. These parameters ultimately define the characteristics of the electron precipitation, in particular the energy range involved, and the flux lost from the radiation belts.…”