Reply To: X-ray cooling?

[jamesr]

slane wrote:
The temperatures of umbrae of the sunspots are approximate 4,500k, why do you think that the temperatures of plasmas in eyewalls of sunspots are 4,500k? The temperatures of plasmas in eyewalls of sunspots are certainly above ten million Kelvin.
The velocity of the Evershed flow of the sunspot is very large (1-9km/s).

Where do you get that temperature from??
The velocity from dopper shift of spectra lines is indeed of the order of a few km/s but this is the bulk flow of material, and nowhere near the speed te ions need to fuse.
The average energy corresponding to 10million K is 862eV ( conversion factor 1eV = 11604K). a KE of 862eV corresponds to a velocity of 200km/s. However even at that temperature only the protons at the top end of the thermal speed distribution have a chance of fusing. A proton with kinetic energy of 10keV has a velocity of 1500km/s

There no evidence I know of that the temperature at any point in or around sunspots gets this high. Indeed the spectral data gives it away a bit. At the temperatures required you cannot get spectra lines. The plasma would be fully ionised; the electrons & ions have way too much energy to recombine and give off a visible photon.

In any case the particle denisty is way too low in the photosphere to have any meaningful fusion anyway.

On a side note – do you realise how unlikely fusion with ordinary hydrogen is? the cross sections (reaction probabilities) are measured in barns (cm^-24)
at 10keV the cross sections are as follows:
for D-T = 2.7E-2 barns
for D-D= 2.8E-4 barns
p+B11 = 4.6E-17 barns
p+p = 3.6E-26 barns

at 100keV it gets a little better, esp for the pB11
for D-T = 3.43 barns
for D-D= 3.3E-2 barns
p+B11 = 3E-4 barns
p+p = 4.4E-25 barns

ie the probablility of a ordinary hydrogen (p+p) reaction is over 20 orders of magnitude lower than D-T