Comments on: MESSENGER Solves Solar Flare Mystery

By: Lawrence B. Crowell

Lawrence B. Crowell — Thu, 29 Oct 2009 03:44:53 +0000

The material in a CME is basically plasma dragged out of the photophere by the intense magnetic field heaving out of the surface as it uncoils and releases energy. I am not very well informed on these matters I have to admit, but I would suspect the temperature of the material is not significantly different from that on the solar surface. I am sure this data exists, all it requires is to measure the blackbody spectrum of the hot material.

Now maybe this material gets rapidly heated by oscillating magnetic fields, and maybe pockets or strands of the stuff reach 10^6 to 10^7K temperatures. I would think X-ray and gamma ray data could support or refute this.

I still am a bit perplexed over where these neutrons come from.

Cheers LC

By: Nexus

Nexus — Thu, 29 Oct 2009 02:39:42 +0000

"Of course the next question is whether there is sufficient density of protons and electrons to maintain this process."

Your calculations seem to suggest the effect increases with both density and temperature. CMEs are both hotter and denser than average for the corona, so it's plausible that CMEs could produce larger numbers of neutrons after they have been launched away from the Sun. Some of these neutrons decay into protons which are able to escape because they are not trapped by the magnetic field lines/

By: Jon Hanford

Jon Hanford — Thu, 29 Oct 2009 00:58:41 +0000

LBC, thanks for your cogent and informed answer to my previous post. Of course the wiki entry for the solar corona mention the likelyhood that magnetic reconnection as well as wave heating may both be responsible for the extreme coronal heating. And, of course, proton and neutron density are also major factors in this question of baryonic density. Also , fermionic densities would also have a bearing on this discussion.

By: Lawrence B. Crowell

Lawrence B. Crowell — Wed, 28 Oct 2009 17:53:11 +0000

The solar corona is kept hot by Alfven waves which oscillate charge particles, electrons and protons. This appears to be the source as I understand it for the extreme heat of the corona. Now let us assume that the temperature is 10^7K. If I use the equipartition theorem kinetic energy 1/2mv^2 = E_k = (3/2)kT, for k = 1.4e^{-23}J/K. So the energy is ~ 5e^{-16}J, per particle. This is then about 3000 eV (3KeV) . Well lets throw that into the Boltzmann distribution exp(-E/kT) and set E as ~1Mev for the energy difference between a proton and neutron. So the probability estimate is P ~ 1 – exp(-10^{-3}) ~ 10^{-3} (Taylor theorem). Not bad, and this is how the nuclear cycle is maintained in the solar interior at comparable temperatures. So energetically it is plausible that a thermal generated bath of neutrons could be produced.

Of course the next question is whether there is sufficient density of protons and electrons to maintain this process. I would have to look up stuff on plasma physics, an area I am not any expert on, to see if this could be maintained. Maybe a pulse of protons and electrons into the corona has a delayed response in the production of neutrons. This process would have to be robust enough to keep producing neutrons at a reasonable rate, since they do have a ~ 1000 sec half life.

Lawrence B. Crowell

By: Jon Hanford

Jon Hanford — Wed, 28 Oct 2009 14:11:30 +0000

Lawrence Crowell, in your earlier post concerning the source of energetic neutrons, you mention the inadequacy of the photosphere (in terms of temperature) to create /maintain neutron flux, if I understand you correctly. Might the energy required for for these processess reside in the solar corona? Temperatures there can range from 3-10 million K. (See wiki page on solar corona and theories for its' creation and extreme temps here: http://en.wikipedia.org/wiki/Corona . The above article mentions " at least some moderate-sized flares continuously produce high-energy neutrons in the solar corona ". Would not the temperatures encountered in the scorching solar corona as opposed to the much cooler photosphere possibly possibly be the energy source needed to sustain this neutron population, at least initially? Just a guess on my part

By: Manu

Manu — Wed, 28 Oct 2009 10:07:14 +0000

Nuclear splosions still there? Tsktsk… :S

By: Torbjorn Larsson OM

Torbjorn Larsson OM — Tue, 27 Oct 2009 18:21:33 +0000

where do these neutrons come from.

Products of cosmic radiation?

By: Jon Hanford

Jon Hanford — Tue, 27 Oct 2009 13:01:44 +0000

I just hoping that proton or neutron fluxes near MESSENGER don't cripple any instrumentation onboard. I know shielding and spacecraft orientation will help mitigate the problem, but getting hit by a sufficiently powerful and prolonged proton/neutron 'storm' might play havoc with some of the onboard electronics.

By: Feenixx

Feenixx — Tue, 27 Oct 2009 08:43:25 +0000

It should be "about 150 million km"…

By: doug.k2

doug.k2 — Tue, 27 Oct 2009 06:43:42 +0000

Oops! Distance from Sun to Earth "about 150,000 km"

By: Astrofiend

Astrofiend — Tue, 27 Oct 2009 04:16:30 +0000

"In the fields of observation, chance favors only the prepared spacecraft" – Louis Pasteur, University of Lille, 7th December 1854.

At least that's what I think he said.

By: Lawrence B. Crowell

Lawrence B. Crowell — Tue, 27 Oct 2009 03:04:13 +0000

err: I meant "far above what is expected …

By: Lawrence B. Crowell

Lawrence B. Crowell — Tue, 27 Oct 2009 03:03:32 +0000

CME are magnetohydrodynamical (MHD)events. Knots of magnetic field in a plasma release that energy by pulling free of the photosphere of the sun and throwing the material out in an arc. This article though raises to my mind some questions. Neutrons will move along magnetic field lines, contrary to protons and electrons which will orbit or cycle around them. So if there are neutrons in the material near the photosphere they will move along the field lines, or more really a gradient in the magnetic field.

To my mind the question is where do these neutrons come from. Protons have a mass of 938MeV and neutrons an additional MeV. That means there has to be energy to generate neutrons from protons when they absorb a high energy electron. But these are nuclear energy scaled processes. The photosphere is 5800K in temperature, which is a number of magnitude lower in energy per particle for nuclear processes.

The paper quotes:
Said Feldman. "From this fact, we inferred the continuous production of protons in the 30-to-100-MeV (million electron volt) range due to the flare."

Yet these are on an energy scale I should think is far below what is expected for the solar surface

By: Nexus

Nexus — Tue, 27 Oct 2009 01:51:09 +0000

If my memory serves me correctly, coronal mass ejections are caused by magnetic fields. It starts as a loop of magnetic field lines associated with a sunspot. The loop gradually takes on a more complicated shape that traps some of the coronal gas inside it, and there is a lot of energy bound up in that complicated shape. Eventually the field lines snap back into a more simple shape and the gas is propelled away from the Sun; the stored energy in the twisted field lines is converted into the kinetic energy of the escaping gas. Not a very lucid explanation, I know, but it's hard to describe without pictures.

By: Manu

Manu — Tue, 27 Oct 2009 00:30:47 +0000

Ahem… "nuclear explosions in the corona"
You suuuuure?