Thursday, 19 December 2013

Solar Facts I

Bands for spectroscopy/imaging
Band Wavelength (nm) Region
G 430.55 photosphere
FeI 630.2 photosphere/low chromosphere
H-alpha 656.28 Chromosphere
CaII 854.00 Chromosphere
HeII 30.4 Chromosphere
FeIX 17.1 Corona/transition region

CaII spans a range of atmospheric heights. From the far wings into the core the line samples from the low to high photosphere. The line core itself is formed in the lower chromosphere.

The beta of a plasma, symbolized by β, is the ratio of the plasma pressure (p = nkBT) to the magnetic pressure (pmag = B²/2μ0).
For plasma with β << 1 the pressure may be neglected.
For plasma with β >> 1 the Lorentz force may be neglected.

The plasma β for different plasma is shown in the table below
Plasma type Coronal Loop Active Corona Coronal Hole Solar wind Magnetosphere
B 300G (0.03T) 100G (0.01T) 10G (0.001T) 6x10-9 T 3x10-5 T
beta 0.0004 0.01 0.007 1 4x10-6
T (K) 106 2x106 106 105 104
Density (kg/m3) 1.7x10-11 1.67x10-13 1.67x10-13 1.7x10-20 1.7x10-17
Alfven Speed(km -1 6500 41 6500
Sound Speed(km -1 120 37 12
Magnetic Reynolds number 6.8x1013 1.5x1012 1.7x10-17

1 comment:

  1. HeI 584 Angstrom lower transition region emission
    OV 629 Angstrom

    AIA passbands
    LAC (lower atmospheric channel) 1700, 304, 1600 Angstrom
    CCC (cooler coronal channel) 171, 193, 211 Angstrom
    HCC (hotter coronal channel) 335, 94, 131 Angstrom