Earth B = 1 gauss
Energy Density = 1/8p = 0.4 ergs cm-3
For comparison: P=nkT ~ 1019 * 1.4 * 10-16 * 300
= 4 * 105 erg cm-3
Why the Earths B field does no affect us.
In Sun T = 6000 at surface
If B2/8p = 10-3P : significant effects
B2 ~ 109
B ~ 3*104 gauss Happens in Sun corona
How does field get this high?
Rotation winds up B field lines
Equator 25d period
Latitude = 40 27d period
Flux tube twisted: gets twisted like a rope, B density increases until it buoys local gas up and makes tube above surface.
Lower down and cooler.
Heated by shock waves?
2 * 10^6 K in loops
Luminosity = 10^-6 Lsun = 4* 10^27 erg sec^-1
Heating mechanism unknown