Open AccessCan Kelvin‐Helmholtz instabilities of jet‐like structures and plumes cause solar wind fluctuations at 1 AU?
Author(s) -
Parhi S.,
Suess S. T.,
Sulkanen M.
Publication year - 1999
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/1999ja900041
Subject(s) - physics , magnetohydrodynamics , solar wind , plume , heliosphere , jet (fluid) , instability , turbulence , thermal wind , mechanics , geophysics , atmospheric sciences , magnetic field , wind speed , wind shear , meteorology , quantum mechanics
The long high‐latitude sampling of Ulysses provides the opportunity to study fine structures. At latitudes poleward of ∼ −60° the solar wind had fluctuations in velocity gradients which were attributed to “microstreams.” The data also suggested fluctuations characterized by magnetic plus thermal pressure balance structures (‘PBS’). At higher frequencies, MHD turbulence was observed and found to be less evolved than it is in the ecliptic but essentially independent of heliographic latitude. It is argued here that microstreams, PBS, and MHD turbulence could all be the remnants of mixing due to shear instabilities associated with plumes and other filamentary structures (“jets”) in coronal holes. To show this, we simulate a plume‐like jet in the presence of an ambient magnetic field. We find that the presence of the ambient field reduces the growth rate of the instability, but the shear between a jet and its ambient still becomes unstable to the MHD Kelvin‐Helmholtz instability when the shear speed is larger than the largest local magnetosonic speed, a condition probably satisfied for plumes.