A Systematic Look at the Temperature Gradient Contribution to the Dayside Magnetopause Current. Issue 4 (21st February 2022)

• Record Type: Journal Article
• Authors: Beedle, J. M. H.; Gershman, D. J.; Uritsky, V. M.; Phan, T. D.; Giles, B. L.
• Is Part Of: Geophysical research letters. Volume 49:Issue 4(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-21
• Subjects: magnetopause -- chapman‐ferraro current -- diamagnetic currents -- particle drifts; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL097547
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Magnetopause diamagnetic currents arise from density and temperature driven pressure gradients across the boundary layer. While theoretically recognized, the temperature contributions to the magnetopause current system have not yet been systematically studied. To bridge this gap, we used a database of Magnetospheric Multiscale magnetopause crossings to analyze diamagnetic current densities and their contributions across the dayside and flank magnetopause. Our results indicate that the ion temperature gradient component makes up to 37% of the ion diamagnetic current density along the magnetopause and typically opposes the classical Chapman‐Ferraro current direction, interfering destructively with the density gradient component, thus lowering the total diamagnetic current density. This effect is most pronounced on the flank magnetopause. The electron diamagnetic current was found to be 5–14 times weaker than the ion diamagnetic current on average. Plain Language Summary: The solar wind represents a continuous outflow of charged particles from the Sun's upper atmosphere into the solar system. Upon reaching Earth's magnetosphere, the solar wind's dynamic pressure is balanced by the magnetic pressure of Earth's magnetic field in a boundary layer known as the magnetopause. This boundary layer represents the entry point of the solar wind's energy into Earth's magnetosphere and upper atmosphere, playing a crucial role in energy transport throughout the interconnected system. Plasma density and temperature differences across the boundary layer generate an electric current that supports the magnetopause. In this paper, we clarify the physical mechanism of the magnetopause current by using high‐resolution data from NASA's Magnetospheric Multiscale mission. We found a significant ion temperature contribution to the magnetopause current not identified in previous studies. Our results also indicated that the plasma electrons' contribution to the magnetopause current was significantly smaller than the ion contribution. Key Points: The magnetopause diamagnetic current is composed of opposing density and temperature gradient generated components The temperature gradient contributes up to 37% of the ion diamagnetic current density along the magnetopause The temperature component typically opposes the classical Chapman‐Ferraro current direction