2025 Workshop: Current circuit in MIT system
Toshi Nishimura toshi16@bu.edu
GEM FG leads: Doga Oztuerk dsozturk@alaska.edu & Dong Lin ldong@ucar.edu
Shasha Zou shashaz@umich.edu
Patrick Alken <patrick.alken@colorado.edu>;
Karl Laundal Karl.Laundal@uib.no
Jesper Gjerloev W. Jesper.Gjerloev@jhuapl.edu
This session solicits contributions regarding the ionospheric current system, its interaction with the ionospheric/thermospheric state variables, and its connection with the magnetospheric currents. The session welcomes any observations, models, and their combinations, in both local and global aspects of the currents including interhemispheric asymmetries. We aim to facilitate the exchange of knowledge between the GEM and CEDAR communities across different latitude regions and geophysical conditions.
Currents in the magnetosphere couple to the ionosphere, creating a dynamic interaction that varies significantly in space and time, especially during periods of strong driving from the solar wind. Ionospheric currents provide valuable information about the magnetosphere, acting as a window into these far-away regions of geospace. They also modify the state of the ionosphere and thermosphere through precipitation and heating. Understanding of the global current circuits including their interhemispheric asymmetries is identified as a priority science goal in the 2024 Heliophysics Decadal Survey.
While a simple picture of field-aligned currents from the magnetosphere closing at high latitudes through horizontal current systems exists, the reality is much more complex. These currents also extend to mid- and low-latitude regions, necessitating a more comprehensive view of the global current system.
At low and mid-latitudes, current systems are often simplified and categorized as the solar quiet (Sq) current system, characterized by a counterclockwise vortex in the northern hemisphere and a clockwise vortex in the southern hemisphere connected by interhemispheric field-aligned current, along with an equatorial electrojet during the daytime. However, the 3D structure of this ionospheric current system is intricate and depends on various factors such as local and global ionospheric conductivities, wind dynamo forcing, and ionospheric and magnetospheric current sources. These complexities are not fully understood, particularly during periods of strong changes in forcing, making the current flow challenging yet crucial to comprehend.
Measuring the currents directly is difficult, but they are often inferred from magnetic perturbations observed at the ground or at low Earth orbit (LEO) altitudes. Rocket experiments that briefly enter the ionosphere provide a more detailed but local picture of the interplay between forcing and response. Ground-based observational networks and numerical simulations have presented global current distribution and evolution. These currents play a significant role in the energetics at mid and high latitudes through energetic precipitating particles, ion-neutral coupling, momentum exchange, and the ionospheric electrodynamo.