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Can Kelvin-Helmholtz Instabilities of Jet-Like Structures and Plumes Cause Solar Wind Fluctuations at 1AUDuring its south polar passage in 1994, Ulysses sampled the solar wind emerging from the south polar coronal hole. In analysing these data two types of density fluctuations lasting a few hours have been reported, one characterized by fluctuations in velocity gradients ("microstreams") and the other by magnetic plus thermal-pressure balance structures ("PBS"). Microstreams were both temporal and spatial in nature. At higher frequencies, MHD turbulence was observed and found to be less evolved than in the ecliptic, but essentially independent of heliographic latitude. It is argued here that microstreams, PBS, and MHD turbulence could all be the remnant of shears associated with plumes and other filamentary structures ("jets") which have been reported to exist in coronal holes. The shear between a jet and its ambient can become unstable to the MHD Kelvin-Helmholtz ("KH') instability at 5-10 solar radius and the propagating instability can cause fluctuations like those seen by Ulysses. This motivates us to simulate coronal jets using a 3D MHD ZEUS code. The first 2D results have just started to come and are promising. To study the KH instability the jet is perturbed at the boundary with a linear amplitude and fixed frequency. The jet seems to pass through various distinct phases, one of which Is apparently dominated by KH instabilities. These instabilities drive oblique shocks into the jet as the turbulent eddies contact the jet surface. It is known that KH instabilities and internal shock waves are partially suppressed by magnetic field tension. Hence, in simulating far along the jet the Instability is expected to produce Alfvenic fluctuations like those seen near 1 AU.
Document ID
19990103160
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Parhi, Shyamsundar
(NASA Marshall Space Flight Center Huntsville, AL United States)
Suess, Steven T.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Sulkanen, Martin E.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Subject Category
Solar Physics
Distribution Limits
Public
Copyright
Other

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