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Investigating Boundary Layer Properties at Jupiter's Dawn Magnetopause.

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Title: Investigating Boundary Layer Properties at Jupiter's Dawn Magnetopause.
Authors: Montgomery, Jake1,2 (AUTHOR) jake.montgomery@contractor.swri.org, Ebert, R. W.1,2 (AUTHOR), Allegrini, F.1,2 (AUTHOR), Fuselier, S. A.1,2 (AUTHOR), Bagenal, F.3 (AUTHOR), Bolton, S. J.2 (AUTHOR), Szalay, J.4 (AUTHOR), Wilson, R. J.3 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Aug2024, Vol. 129 Issue 8, p1-16. 16p.
Subject Terms: Solar magnetic fields, Magnetic reconnection, Plasma boundary layers, Magnetopause, Boundary layer (Aerodynamics), Solar wind
Abstract: We survey crossings of Jupiter's dawn magnetopause during the Juno prime mission to identify and characterize Jupiter's magnetopause boundary layer. Using plasma and magnetic field observations from Jovian Auroral Distributions Experiment and Juno Magnetic Field investigation, we identify 53 boundary layer events from the 62 magnetopause crossings studied here. We find that the boundary layer generally exhibits mixed properties of magnetosheath and magnetosphere electron distributions, including lower characteristic electron energies and denser ion populations than in the magnetosphere, but higher characteristic electron energies and less dense ion populations than in the magnetosheath. Boundary layer proton speeds are on average slower than both the magnetosheath and magnetosphere. Other proton parameters in the boundary layer have intermediate values between the magnetosheath and magnetosphere. Through ion composition analysis in regions adjacent to the magnetopause, we find evidence of solar wind and magnetospheric plasma in the boundary layer that suggests plasma is transported across the magnetopause in both directions. This mass and energy transport may be the result of solar wind interactions such as magnetic reconnection and Kelvin‐Helmholtz instabilities. However, many boundary layer events do not exhibit local signatures of these solar wind interactions and plasma may be transported by a non‐local process or diffusively transported. Plain Language Summary: Jupiter has the strongest planetary magnetic field in the solar system and over one metric ton per second of sulfur and oxygen is ejected via volcanic activity on the moon, Io. These two factors inflate Jupiter's magnetosphere as material from Io slowly travels outward from Jupiter to near the magnetopause, the boundary between the magnetosphere and magnetosheath. Jupiter's magnetopause boundary layer is located between its outer magnetosphere and surrounding magnetosheath. The magnetosheath is a region of primarily solar wind plasma between the bow shock and the magnetopause and is draped over the magnetosphere. We find that the dawnside boundary layer that separates the magnetosphere and the magnetosheath is comprised of plasma from both regions and travels across this region due to a variety of physical processes. Additionally, we find solar wind plasma in the magnetosphere and plasma from Io in the magnetosheath. This result implies that plasma travels across the boundary layer in both directions. Lastly, our survey shows the plasma in the dawnside boundary layer moves in the opposite direction of Jupiter's rotation, contrary to the plasma located closer to Jupiter. Key Points: The primary characteristic of Jupiter's magnetopause boundary layer is a dual distribution of magnetosphere and magnetosheath electronsIon composition in the boundary layer and adjacent regions show that plasma is transported across the magnetopause in both directionsIon flow speeds in Jupiter's dawn flank magnetopause boundary layer are hundreds of km/s tailward, opposite to corotation on the dawnside [ABSTRACT FROM AUTHOR]
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Abstract:We survey crossings of Jupiter's dawn magnetopause during the Juno prime mission to identify and characterize Jupiter's magnetopause boundary layer. Using plasma and magnetic field observations from Jovian Auroral Distributions Experiment and Juno Magnetic Field investigation, we identify 53 boundary layer events from the 62 magnetopause crossings studied here. We find that the boundary layer generally exhibits mixed properties of magnetosheath and magnetosphere electron distributions, including lower characteristic electron energies and denser ion populations than in the magnetosphere, but higher characteristic electron energies and less dense ion populations than in the magnetosheath. Boundary layer proton speeds are on average slower than both the magnetosheath and magnetosphere. Other proton parameters in the boundary layer have intermediate values between the magnetosheath and magnetosphere. Through ion composition analysis in regions adjacent to the magnetopause, we find evidence of solar wind and magnetospheric plasma in the boundary layer that suggests plasma is transported across the magnetopause in both directions. This mass and energy transport may be the result of solar wind interactions such as magnetic reconnection and Kelvin‐Helmholtz instabilities. However, many boundary layer events do not exhibit local signatures of these solar wind interactions and plasma may be transported by a non‐local process or diffusively transported. Plain Language Summary: Jupiter has the strongest planetary magnetic field in the solar system and over one metric ton per second of sulfur and oxygen is ejected via volcanic activity on the moon, Io. These two factors inflate Jupiter's magnetosphere as material from Io slowly travels outward from Jupiter to near the magnetopause, the boundary between the magnetosphere and magnetosheath. Jupiter's magnetopause boundary layer is located between its outer magnetosphere and surrounding magnetosheath. The magnetosheath is a region of primarily solar wind plasma between the bow shock and the magnetopause and is draped over the magnetosphere. We find that the dawnside boundary layer that separates the magnetosphere and the magnetosheath is comprised of plasma from both regions and travels across this region due to a variety of physical processes. Additionally, we find solar wind plasma in the magnetosphere and plasma from Io in the magnetosheath. This result implies that plasma travels across the boundary layer in both directions. Lastly, our survey shows the plasma in the dawnside boundary layer moves in the opposite direction of Jupiter's rotation, contrary to the plasma located closer to Jupiter. Key Points: The primary characteristic of Jupiter's magnetopause boundary layer is a dual distribution of magnetosphere and magnetosheath electronsIon composition in the boundary layer and adjacent regions show that plasma is transported across the magnetopause in both directionsIon flow speeds in Jupiter's dawn flank magnetopause boundary layer are hundreds of km/s tailward, opposite to corotation on the dawnside [ABSTRACT FROM AUTHOR]
ISSN:21699380
DOI:10.1029/2024JA032926