Electron precipitation from EMIC waves: a case study from 31 May 2013

• Published in: Journal of Geophysical Research: Space Physics
• Main Authors: Clilverd, Mark A., Duthie, Roger, Hardman, Rachael, Hendry, Aaron T., Rodger, Craig J., Raita, Tero, Engebretson, Mark, Lessard, Marc R., Danskin, Donald, Milling, David K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Arctic; Antarctic; Canada; Antarc*; Antarctica
• Online Access: http://nora.nerc.ac.uk/id/eprint/510706/; https://nora.nerc.ac.uk/id/eprint/510706/1/Clilverd%20et%20al%202015%20-%20Electron%20precipitation%20from%20EMIC%20waves.pdf; https://doi.org/10.1002/2015JA021090

On 31 May 2013 several rising-tone electromagnetic ion-cyclotron (EMIC) waves with intervals of pulsations of diminishing periods (IPDP) were observed in the magnetic local time afternoon and evening sectors during the onset of a moderate/large geomagnetic storm. The waves were sequentially observed in Finland, Antarctica, and western Canada. Co-incident electron precipitation by a network of ground-based Antarctic Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK) and riometer instruments, as well as the Polar-orbiting Operational Environmental Satellite (POES) electron telescopes, was also observed. At the same time POES detected 30-80 keV proton precipitation drifting westwards at locations that were consistent with the ground-based observations, indicating substorm injection. Through detailed modelling of the combination of ground and satellite observations the characteristics of the EMIC-induced electron precipitation were identified as: latitudinal width of 2-3° or ΔL=1 Re, longitudinal width ~50° or 3 hours MLT, lower cut off energy 280 keV, typical flux 1×104 el. cm-2 sr-1 s-1 >300 keV. The lower cutoff energy of the most clearly defined EMIC rising tone in this study confirms the identification of a class of EMIC-induced precipitation events with unexpectedly low energy cutoffs of <400 keV.