2024 Workshop: Interhemispheric asymmetries (IHA)
Qingyu Zhu
Yun-Ju Chen
Lynn Harvey
Astrid Maute
Aaron Ridley
The state of ionosphere-thermosphere (IT) is hardly ever a mirror image of the other hemisphere even when considering differences due to season and Earth’s magnetic field. Among others, neutral wind and density, composition, ion drift, and plasma distribution, exhibit interhemispheric asymmetries (IHA) on temporal scales from hours to seasonal. Forcing from both magnetosphere-ionosphere (MI) coupling and lower atmosphere can contribute to IHA but it is still not well understood what constitutes a significant asymmetry and their cause. The effect of the strong high latitude energy deposition on the IT system can be modulated by the background atmospheric state which is strongly affected by the vertical coupling to the lower atmosphere. Meanwhile, during meteorological disturbed conditions, strong spatial and temporal variations in the wave spectrum and the background conditions lead to significant changes in the mesosphere-lower thermosphere (MLT) and IT system. In this workshop we will discuss causes and effects of IHA in the upper atmosphere. We solicit contributions examining IHA in the MLT and IT regions to improve our understanding of the generation and impacts of interhemispheric asymmetries.
In the I-T system, interhemispheric Asymmetries (IHA) take many forms. Observations have revealed that IHA manifested via particle precipitation and conductivity, auroral patterns, substorm occurrence and locations, field-aligned currents, ionospheric electric potentials, magnetic field geometries, ionospheric and thermospheric neutral and plasma characteristics, and atmospheric waves from the lower atmosphere. Understanding IHA is critical for understanding the IT system to the forcing from both above and below.
Despite the now-known importance and ubiquity of IHA, their properties have not been thoroughly examined or documented. The lack of IHA input to models has prevented simulations from testing their impact on the global I-T system. Also simulation capabilities for handling IHA are significantly limited. Furthermore, impacts of IHA have not been quantified or reproduced. This workshop focuses on quantifying interhemispheric differences observed in the IT system and understanding their causes and importance for the upper atmosphere. With the available observations and sophisticated numerical modeling capabilities we are in a better position now to study the IHA. Meanwhile, this workshop is complementary to the NASA 2020 LWS FST on “Caused and Consequences of Hemispherical Asymmetries in the M-I-T system”. This research is also timely in preparation for the upcoming Geospace Dynamic Constellation (GDC) mission. The proposed activities will be coordinated with NSF GEM focus group on “Interhemispheric Approaches to Understand M-I coupling (IHMIC)” by bringing their knowledge and holding joint campaigns