Automated Identification of Electron Microinjections in MMS/FEEPS
Measurements: Initial Results
Abstract
The MMS spacecraft routinely observe electron “microinjections” at
energies in the 10s-100s keV range across the nightside magnetosphere at
distances <20 Re. Microinjections are typically observed in
clusters where multiple dispersed injection signatures are recorded in
succession over a short time interval (e.g., ~10 in one
hour) and may be related to surface wave activity at the magnetopause.
Recent work has shown that microinjections have distinctive features in
the angular distributions, where field-aligned distributions are
observed near dusk, while trapped distributions are observed near dawn.
Due to their recent discovery, the origin and generation of
microinjections has yet to be conclusively identified and detailed
studies thus far have largely been done on a case-by-case basis. In an
effort to elucidate more general properties and characteristics of
microinjections, we describe an automated routine designed to identify
microinjection signatures in the MMS/FEEPS measurements. The algorithm
uses image processing techniques (the radon transform) and is based on a
similar method developed to identify whistler-mode chorus elements in
Van Allen Probes wave observations (Sen Gupta et al., [2017]). We
present an initial set of results from a statistical database of
microinjection events obtained from the automated algorithm to further
our understanding of this intriguing phenomenon.