Magnetic Fields

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 Earth’s 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

Differential rotation

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.

 

Chromosphere

Lower down and cooler.

Heated by shock waves?

 

 

 

 

 

 

 

 

 

Magnetic Recombination

 

Corona

2 * 10^6 K in loops

Luminosity = 10^-6 Lsun = 4* 10^27 erg sec^-1

Heating mechanism unknown