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On the Motion of the Heliospheric Magnetic Structure Through the Solar Wind Plasma
Author(s) -
Borovsky Joseph E.
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja027377
Subject(s) - physics , solar wind , plasma , heliospheric current sheet , magnetic field , reference frame , magnetic structure , interplanetary magnetic field , computational physics , frame (networking) , nuclear physics , telecommunications , magnetization , quantum mechanics , computer science
A reference frame in the solar wind can often be found wherein the flow vector v is everywhere approximately parallel to the magnetic field vector B . This is the frame of the heliospheric magnetic structure moving relative to the plasma. Since v ⊥ is very small in this reference frame, the magnetic structure appears to have little temporal evolution. The structure moves outward away from the Sun faster than the plasma flow. Even for highly Alfvénic plasma, the structure does not move at the Alfvén speed relative to the proton plasma, rather it moves at ~0.7 v A . This may be caused by the spread in the vector directions of the local magnetic field. The degree of inhomogeneity of the plasma is hypothesized to control the motion of the magnetic structure through the plasma. If so, non‐Alfvénicity may be owed to an inability of Alfvénic perturbations to coherently propagate from Alfvénic injections at the Sun. Schemes that mathematically advect magnetic and plasma structure from upstream solar wind monitors to the Earth may be improved by calculating and including the motion of the structure relative to the solar wind velocity vector.