On the Benefits and Challenges of Multi-Point Analysis of Energetic Particle Injections in the Inner Magnetosphere
Tuesday, 16 December 2014
Energetic particle injections (EPIs) are the sudden enhancement of ~10s to ~100s of keV electrons and or ions in the near-Earth plasma sheet and inner magnetosphere. EPIs are known to be associated with substorm activity and reconnection in the magnetotail, though there are still many outstanding questions and competing theories concerning their exact nature (formation and evolution). Here, we focus on multipoint observations of EPIs at L < 10. We present several cases of individual or multiple EPI events observed by spacecraft from the THEMIS, Van Allen Probes, GOES, POES/MetOp, and LANL-GEO constellations. These cases have been chosen to showcase both the benefits of understanding EPIs as well as the challenges in interpreting multi-point observations of EPI events. EPIs are considered potentially important contributors to the seed populations of ring current particles and electrons in the outer radiation belt. Furthermore, due to the temperature anisotropy inherent in drifting bunches of enhanced fluxes of energetic ions and electrons, EPIs also potentially play an important role in electromagnetic ion cyclotron (EMIC) and whistler-mode chorus wave growth and activity. Thus, it is beneficial to the inner magnetospheric community to study EPIs and better define their role in dynamics of the ring current and outer radiation belt particle populations. However, interpreting multi-point observations of EPIs includes a variety of challenges, which we also outline and discuss here using example cases for supporting evidence. These challenges include: determining the location and width of the injection boundary in MLT and how this may change as a function of L-shell; timing analysis of EPIs observed by multiple spacecraft and drift echoes observed by the same spacecraft considering global field mapping of pitch-angle dependent drift shells; and considerations of energy- and/or pitch angle-dependent boundaries (e.g., Alfven layers, the plasmapause, and bifurcated drift shells).