PDA

View Full Version : A Solution to the Solar Corona Heating Problem - Alfven Wave Observations



mikeg64
2011-Aug-10, 06:10 AM
There is continuing evidence to indicate that the heating of the solar corona is largely caused by energy carried by alfvenic waves ( oscilations of the plasma and magnetic field) and spicules (jets of plasma with temepartures of millions of degrees moving upwards from the photosphere at approx 20km/s).


“We now understand how hot mass can shoot upward from the solar interior, providing enough energy to maintain the corona at a million degrees and fire off particles into the high-speed solar wind,” says Scott McIntosh, the study’s lead author and a scientist in NCAR’s High Altitude Observatory. “This new research will help us solve essential mysteries about how energy gets out of the Sun and into the solar system.”

The article claims that alfven waves ride spicules which themselves may have originated from p-mode oscillations photosphere (sound waves at the suns surface). Over 70000 spicules may be active at a given time.

http://www2.ucar.edu/news/5007/wave-power-can-drive-suns-intense-heat

Ken G
2011-Aug-16, 02:24 AM
Interesting stuff, thanks for citing that. It was long thought that Alfven waves would reflect back down when they encounter the low density corona, but these observations seem to show the waves find a way to bore on through, and are much more vigorous than previously measured or theoretically expected. Now the question is, how are they doing it, but it's real progress.

mikeg64
2011-Aug-17, 06:58 PM
Thanks for the comment
Waves boring through the transition layer sounds somewhat vigorous.
Here is a link to numerical modelling work demonstrating leakage of magneto acoustic waves into the solar corona
http://adsabs.harvard.edu/abs/2011ApJ...727...17F

Some rather nice movies of some of these results may be found here
http://swat.group.shef.ac.uk/simulations.html (the movies require a quicktime plugin)

As KenG indicates

It was long thought that Alfven waves would reflect back down when they encounter the low density corona,
reflection of magneto-acoustic waves can be observed in some of the numerical simulations..

Solon
2011-Aug-19, 05:14 AM
I was recently trying to get a better handle on what might be occuring with the Alfven waves, and found these two pdf files that offer some possible mechanisms.
Generation of Alfven waves by high power pulse at the electron plasma frequency
http://plasma.physics.ucla.edu/papers/microwave-UH.pdf
A Study of Shear Alfvén Waves in Magnetic Stars: the Spherical Shell Model
http://www.francois-rincon.org/papers/Rincon_P561.pdf
Interesting topic, IMO.