A night-side shock aurora and its three different emissions observed on
26 February 2023
Abstract
Ground-based observations of shock aurora, which is an aurora related to
geomagnetic sudden commencement (SC), have mainly been limited to the
dayside. On 26 February 2023, right after the SC onset at 19:24 UT,
ground-based all-sky cameras and a wide-angle camera detected shock
aurora at 21 MLT in the auroral zone. For this aurora, three different
emissions are detected instead of the previously known two emissions:
intensification of a pre-existing arc (19:25 UT), red diffuse aurora
(19:28 UT), and a second, green discrete arc (19:31 UT). The relative
location of these emissions differs from the dayside cases where the
first and last types are not distinguished. Geomagnetic data under this
aurora indicates a significant difference in the anti-sunward
propagation velocity between the secondary discrete arc and the related
field-aligned current.