Details

Autor(en) / Beteiligte

• Sun, W. J.
• Slavin, J. A.
• Smith, A. W.
• Dewey, R. M.
• Poh, G. K.
• Jia, X.
• Raines, J. M.
• Livi, S.
• Saito, Y.
• Gershman, D. J.
• DiBraccio, G. A.
• Imber, S. M.
• Guo, J. P.
• Fu, S. Y.
• Zong, Q. G.
• Zhao, J. T.

Titel

Flux Transfer Event Showers at Mercury: Dependence on Plasma β and Magnetic Shear and Their Contribution to the Dungey Cycle

Ist Teil von

• Geophysical research letters, 2020-11, Vol.47 (21), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2020

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Mercury's flux transfer event (FTE) showers are dayside magnetopause crossings accompanied by large numbers (≥10) of magnetic flux ropes (FRs). These shower events are common, occurring during 52% (1,953/3,748) of the analyzed crossings. Shower events are observed with magnetic shear angles (θ) from 0° to 180° across the magnetopause and magnetosheath plasma β from 0.1 to 10 but are most prevalent for high θ and low plasma β. Individual FR duration correlates positively, while spacing correlates negatively, with θ and plasma β. FR flux content and core magnetic field intensity correlate negatively with plasma β, but they do not correlate with θ. During shower intervals, FRs carry 60% to 85% of the magnetic flux required to supply Mercury's Dungey cycle. The FTE showers and the large amount of magnetic flux carried by the FTE‐type FRs appear quite different from observations at Earth and other planetary magnetospheres visited thus far. Plain Language Summary Any planet with an interior dynamo will interact with the outward streaming stellar wind and likely form a magnetosphere. The magnetopause is a boundary between the shocked solar wind and planetary magnetic field, which can prevent most of the solar wind from directly entering into the magnetosphere. The multiple X‐line reconnection that frequently occurs in the magnetopause creates helical magnetic fields that are termed magnetic flux ropes (FRs) about which open and interplanetary magnetic fields drape. FTE‐type FRs generally have magnetic field lines with one end embedded in the solar wind and the other end connected to the planet through the magnetospheric cusp. The investigation of FTEs in Mercury's magnetosphere is of particular interest because they often occur in large numbers with extremely small temporal spacing, i.e., FTE showers, that are not seen elsewhere. We find that the properties of the FTE‐type flux ropes in these showers depend upon plasma β in the magnetosheath and the magnetic shear angle across the magnetopause. The magnetic flux carried by these flux ropes dominates magnetic flux transfer between Mercury's dayside and nightside magnetosphere. These new results may contribute significantly to our understanding of solar wind‐magnetosphere‐exosphere coupling at Mercury. Key Points Flux transfer event (FTE) showers (≥10 flux ropes in a magnetopause crossing) are prevalent when shear angle is large and plasma β is small FTE‐type flux rope duration, spacing, core field, and flux content during shower events are shown to depend upon shear angle and plasma β FTE‐type flux ropes in shower events carry between 60% and 85% of the magnetic flux required to supply Mercury's Dungey cycle