Local time asymmetry of Saturn's magnetosheath flows. Issue 12 (17th June 2017)

• Record Type: Journal Article
• Authors: Burkholder, B.; Delamere, P. A.; Ma, X.; Thomsen, M. F.; Wilson, R. J.; Bagenal, F.
• Is Part Of: Geophysical research letters. Volume 44:Issue 12(2017)
• Page Start: 5877
• Page End: 5883
• Publication Date: 2017-06-17
• Subjects: Saturn magnetosheath -- Kelvin‐Helmholtz instability -- tangential drag -- magnetic reconnection -- Cassini CAPS -- viscous‐like interaction; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL073031
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Using gross averages of the azimuthal component of flow in Saturn's magnetosheath, we find that flows in the prenoon sector reach a maximum value of roughly half that of the postnoon side. Corotational magnetodisc plasma creates a much larger flow shear with solar wind plasma prenoon than postnoon. Maxwell stress tensor analysis shows that momentum can be transferred out of the magnetosphere along tangential field lines if a normal component to the boundary is present, i.e., field lines which pierce the magnetopause. A Kelvin‐Helmholtz unstable flow gives rise to precisely this situation, as intermittent reconnection allows the magnetic field to thread the boundary. We interpret the Kelvin‐Helmholtz instability acting along the magnetopause as a tangetial drag, facilitating two‐way transport of momentum through the boundary. We use reduced magnetosheath flows in the dawn sector as evidence of the importance of this interaction in Saturn's magnetosphere. Key Points: The magnitude of Saturn's magnetosheath plasma flow velocity in the azimuthal direction is asymmetric in local time The magnetopause boundary is Kelvin‐Helmholtz unstable Implications for understanding a viscous‐like interaction