Solar Physics header image

Solar Wind Dynamics

THE SUN 

Why We Study the Sun 
The Big Questions 
Magnetism - The Key 

SOLAR STRUCTURE 

The Interior 
The Photosphere 
The Chromosphere 
The Transition Region 
The Corona 
The Solar Wind 
The Heliosphere 

SOLAR FEATURES 

Photospheric Features 
Chromospheric Features 
Coronal Features 
Solar Wind Features 

THE SUN IN ACTION 

The Sunspot Cycle 
Solar Flares 
Post Flare Loops 
Coronal Mass Ejections 
Surface and Interior Flows 
Waves and Helioseismology 

RESEARCH AREAS 

Flare Mechanisms 
3D Magnetic Fields 
The Solar Dynamo 
Sunspot Cycle Predictions 
Solar Wind Dynamics 

Click on image for larger version.

Polar Plume Simulation

Polar plumes are being modelled by Steve Suess, Shyamsundar Parhi, and Martin Sulkanen. Plumes are bright rays in coronal holes, visible between one and several solar radii. They are denser and slower compared to interplume plasma and are modelled here as jets or wakes. The plasma is considered compressible and ideal (no viscous dissipation, thermal diffusion, or electrical resistance). A jet is introduced with a perscribed flow speed and an internal magnetic field. The surroundings are at rest and are also permeated by a magnetic field but with a different field strength. The simulations are described in a paper titled "Can Kelvin-Helmholtz instabilities of jet-like structures and plumes cause solar wind fluctuations at 1 AU?" by Parhi, Suess, and Sulkanen. The paper appears in the July 1, 1999 issue of the Journal of Geophysical Research, Vol. 104, No. A7, pages 14,781 to 14,787.

Click on image for animation.

Click on image for animation.

The animations presented here are performed with the computer code Zeus-3D which solves the equations of ideal magnetohydrodynamics explicitly on a Eulerian grid. Open boundary conditions are considered at all boundaries of the simulation domain. The evolution of the Kelvin-Helmholtz instability is studied when a velocity perturbation of less than 1% of the jet flow speed is imposed at the origin of the preexisting jet. In the upper animation, where magnetic shear is low, the effect of the instability is less apparent than in case of strong shear as in the lower panel. This instability helps set up a process of mixing between plumes and interplumes, accompanied with the formation of shocks and plasma entrainment. This suggests that the instability thus generated at a few solar radii can account for the smooth fast solar wind and reduced velocity shear between plumes and interplumes as observed beyond 0.3 astronomical units (about the orbit of the planet Mercury).

 


 

Author: David H. Hathaway, david.hathaway@msfc.nasa.gov, (256) 544-7610
Mail Code SD50, NASA/Marshall Space Flight Center, Huntsville, AL 35812

 

Responsible Official: John M. Davis, john.m.davis@msfc.nasa.gov, (256) 544-7600
Mail Code SD50, NASA/Marshall Space Flight Center, Huntsville, AL 35812

 

Last revised 2000 February 04 - D. H. Hathaway


Reproduced from http://science.nasa.gov