Looking for a mainstream explanation for gamma gays and nuetron capture signatures.

[Michael Mozina]

Looking for a "mainstream" explanation for gamma gays and nuetron capture signatures.

One of Elizabeth's homework problems got me to thinking:

17 - Why do thermonuclear reactions occur only in the Sun’s core? _______.

(a) The core of the Sun is the only place where the density and temperature of hydrogen are high enough and where self-sustaining nuclear fusion reactions can be contained by the great weight and pressure of overlying layers.

(b) That’s the only place in the Sun where there is enough oxygen to fuse the hydrogen.

(c) It’s the only place where there is enough Helium to catalyze the fusion reactions.

(d) The core doesn’t rotate rapidly like the Sun’s outer layers. If it did, the centrifugal force would fling the reactants apart.

(e) There are no thermonuclear reactions going on anywhere in the Sun. The reactions taking place are fission reactions, verified by the lack of detection of solar neutrinos.

Now if Elizabeth is reading this thread, please note that the "correct" answer (in mainstream thinking today) is probably a). However:

http://svs.gsfc.nasa.gov/vis/a000000/a002700/a002750/

RHESSI Observes 2.2 MeV Line Emission from a Solar Flare

The solar flare at Active Region 10039 on July 23, 2002 exhibits many exceptional high-energy phenomena including the 2.223 MeV neutron capture line and the 511 keV electron-positron (antimatter) annihilation line. In the animation, the RHESSI low-energy channels (12-25 keV) are represented in red and appears predominantly in coronal loops. The high-energy flux appears as blue at the footpoints of the coronal loops. Violet is used to indicate the location and relative intensity of the 2.2MeV emission.

Why wouldn't those neutron capture lines and those gamma ray signatures we observe in the solar atmosphere be evidence for some kind of fusion process occurring in the solar atmosphere? In other words, in light of those million degree coronal loops in the solar corona, how does the mainstream decide that fusion is limited to only occurring *inside* of the sun? What would these energy signatures represent in mainstream thinking if not some sort of P-P (or other) fusion process? I'm not really looking to argue any particular point here, I'm instead trying to understand how the mainstream is certain that solar fusion is limited to the core of a star?

 

[SpaceTiger]

Why wouldn't those neutron capture lines and those gamma ray signatures we observe in the solar atmosphere be evidence for some kind of fusion process occurring in the solar atmosphere?

Fusion events can occur even in Earth's atmosphere when cosmic rays collide with atmospheric nuclei. Neutron capture is a common process in the atmospheres of stars and is thought to be one of the dominant modes of post-big bang nucleosynthesis. The homework problem you refer to probably neglected these fusion events because their contribution to the energy output of the sun is negligible.

 

[Michael Mozina]

Fusion events can occur even in Earth's atmosphere when cosmic rays collide with atmospheric nuclei. Neutron capture is a common process in the atmospheres of stars and is thought to be one of the dominant modes of post-big bang nucleosynthesis. The homework problem you refer to probably neglected these fusion events because their contribution to the energy output of the sun is negligible.

I suppose that's a logical explanation about why the question was worded to suggest that fusion only occurs in the core. Would it be safe to say that the mainstream position is open to the possibility that fusion reactions are occurring in the solar atmosphere? If so, would "cosmic ray fusion" be the official explanation for those Rhessi observations?

 

[SpaceTiger]

Would it be safe to say that the mainstream position is open to the possibility that fusion reactions are occurring in the solar atmosphere?

Sure, they'll certainly occur from time to time, but at a rate much, much smaller than that occurring in the core. The PP chain, for example, has an energy generation rate that scales as

\epsilon \propto T^4\rho

where T is the temperature and \rho is the density. The photosphere has a temperature 2000 times smaller than in the core, so even neglecting the differences in density, the energy generation rate would be suppressed by a factor greater than 10^{13}. Layers beyond this (like the corona) can have temperatures only ~10 times smaller than in the core, but densities over 20 orders of magnitude smaller.

If so, would "cosmic ray fusion" be the official explanation for those Rhessi observations?

For the answer to that, you'd have to read the paper. I doubt it's from cosmic ray reactions, though.

 

[Michael Mozina]

Sure, they'll certainly occur from time to time, but at a rate much, much smaller than that occurring in the core. The PP chain, for example, has an energy generation rate that scales as

\epsilon \propto T^4\rho

where T is the temperature and \rho is the density. The photosphere has a temperature 2000 times smaller than in the core,

By the way, thanks for taking the time to answer my questions. I appreciate it.

As you suggest, the photosphere is much cooler than the core, but plasmas that are measured in the millions of degrees have been observed in the corona.

so even neglecting the differences in density, the energy generation rate would be suppressed by a factor greater than 10^{13}. Layers beyond this (like the corona) can have temperatures only ~10 times smaller than in the core, but densities over 20 orders of magnitude smaller.

Well, certainly parts of the corona are very thin, but MHD theory allows for much greater densities of plasma to form into plasma filament channels in the presence of electrical current. If one entertains the presence of electrical current flow in the solar atmosphere, it might be possible to explain fusion in the solar atmosphere. FYI, Rhessi has observed gamma ray emissions in the Earth's atmosphere from electrical discharges on Earth.

http://www.nasa.gov/vision/universe/solarsystem/rhessi_tgf.html

It isn't hard to imagine that electrical discharges occur in the solar atmosphere, as Dr. Charles Bruce suggested. He has already demonstrated a correlation between the speed of lightning leaders in Earth's atmosphere to the speed of events that we observe in the solar atmosphere.

http://www.catastrophism.com/texts/bruce/era.htm

For the answer to that, you'd have to read the paper. I doubt it's from cosmic ray reactions, though.

I doubt it too. The Rhessi images show that these gamma ray emissions and neutron capture processes seems to occur over a "relatively" long time duration. I would expect that cosmic ray events would tend to be shorter lived events. These Rhessi events tend to concentrate in and around the coronal loops, where the temperature is much greater than the surface of the photosphere.

 

[SpaceTiger]

arxiv.org is a website where you can look up papers from authors that are mentioned in press releases like the one in your original post. Here's a paper about the event discussed in that press relase:

http://arxiv.org/abs/astro-ph/0306292"

Within is contained the "mainstream" explanation for the event in question.

Your confusion about the homework problem has been resolved?

 

[Chronos]

Suppositions b) and c) are unsupported and unfounded for reasons already mentioned. Supposition d) is unclear. The core of the sun can obviously achieve more rpm's than surface layers without flying apart.