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The Critical Factor in Controlling the Auroral Intensity in the Cusp Region as Revealed by a Statistical Study on Midday Gap and Non‐Gap Events
Author(s) -
Qiu HuiXuan,
Han DeSheng,
Feng HuiTing,
Shi Run,
Zhou Su,
Zhang Y.L.
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl092414
Subject(s) - interplanetary magnetic field , cusp (singularity) , physics , solar wind , intensity (physics) , ionosphere , magnetosphere , astrophysics , atmospheric sciences , geophysics , magnetic field , optics , geometry , mathematics , quantum mechanics
Taking advantage of the high spatial‐resolution and global coverage of Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations, we investigated the critical interplanetary factors in controlling the cusp auroral emission by dividing the midday auroras into the gap (weak emission) and non‐gap (intense emission) events. Although the cusp auroral intensity is essentially determined by a parameter related to the IMF (interplanetary magnetic field) direction, IMF magnitude (|B y |), and solar wind speed (V), we found that the cusp aurora is statistically weak during the southward IMF but intense when the V and IMF |B y | are greater. Further, we confirmed that even with V > 600 km/s, the intense‐aurora event still shows a minimum occurrence near the IMF |B y | = 0. However, when the IMF |B y | is greater, the V becomes less significant for the intense‐aurora occurrence. These results demonstrate that the IMF |B y | is critical in controlling the cusp auroral intensity, most likely by producing an electric field which is given as V × B y .