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Solar Illumination Dependence of the Auroral Electrojet Intensity: Interplay Between the Solar Zenith Angle and Dipole Tilt
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2019 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 8, p. 6636-6653Article in journal (Refereed) Published
Abstract [en]

The present study investigates the dependence of the local auroral electrojet (AEJ) intensity on solar illumination by statistically examining northward geomagnetic disturbances in the auroral zone in terms of the solar zenith angle χ. It is found that on the dayside, both westward and eastward electrojets (WEJ and EEJ) are more intense for smaller χ, suggesting that the solar extreme ultraviolet‐induced conductance is the dominant factor for the AEJ intensity. On the nightside, in contrast, the χ dependence of the AEJ intensity, if sorted solely by the magnetic local time, apparently depends on the station longitude and hemisphere. However, if additionally sorted by the dipole tilt angle ψ, a consistent pattern emerges. That is, although χ and ψ are correlated, the solar zenith angle and dipole tilt angle have physically different effects on the AEJ intensity. The nightside AEJ, especially the WEJ, tends to be more intense for smaller |ψ|. Moreover, whereas the WEJ is statistically more intense when the ionosphere is dark, the EEJ is more intense when it is sunlit. The preference of the WEJ for the dark ionosphere prevails widely in magnetic local time from premidnight to dawn, and therefore, it cannot be attributed to the previously proposed processes of the preferred monoenergetic or broadband auroral precipitation in the dark ionosphere. Instead, it may be explained, at least morphologically, in terms of the conductance enhancement due to the diffuse auroral precipitation, which is also prevalent from premidnight to dawn and is more intense in the dark hemisphere.

Place, publisher, year, edition, pages
John Wiley & Sons, Ltd , 2019. Vol. 124, no 8, p. 6636-6653
Keywords [en]
auroral electrojets, solar illumination, ionospheric conductance, interhemispheric asymmetry, diffuse precipitation, dipole tilt
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:polar:diva-8395DOI: 10.1029/2019JA026707OAI: oai:DiVA.org:polar-8395DiVA, id: diva2:1396065
Available from: 2020-02-25 Created: 2020-02-25 Last updated: 2020-02-25Bibliographically approved

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Publisher's full texthttps://doi.org/10.1029/2019JA026707
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Journal of Geophysical Research - Space Physics
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