Premium
Hemispheric Asymmetry of the Premidnight Aurora Associated With the Dawn‐Dusk Component of the Interplanetary Magnetic Field
Author(s) -
Liou K.,
Mitchell E. J.
Publication year - 2019
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja025953
Subject(s) - interplanetary magnetic field , physics , northern hemisphere , asymmetry , polarity (international relations) , geophysics , thermosphere , southern hemisphere , ionosphere , astrophysics , atmospheric sciences , magnetic field , solar wind , astronomy , chemistry , quantum mechanics , cell , biochemistry
It has been known for decades that the nightside aurora in the Northern Hemisphere (NH) tends to be brighter when the interplanetary magnetic field (IMF) measured at Earth has a dawnward (negative y ) component compared to a duskward (positive y ) component. This asymmetric response to the polarity of IMF B y has been explained by an interhemispheric current flowing out of the NH due to a nonuniform “penetration” of IMF B y onto the magnetotail. If such a hypothesis is correct, it should predict a brighter aurora in the nightside Southern Hemisphere (SH) for positive IMF B y than negative IMF B y . Here we investigate this hypothesis using Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics/Global Ultraviolet Imager data. The present study not only reproduces the result previously found in NH but also shows an opposite change to its Northern Hemispheric counterpart in SH in response to the different IMF B y polarity. When comparing north to south, for negative IMF B y , the premidnight auroral energy flux is greater in NH than that in SH. The result becomes opposite for positive IMF B y . This result is consistent with the hypothesis of the existence of an interhemispheric field‐aligned current.