Team Discovers "Throttle" For Solar Wind

ScienceDaily is reporting that a team of scientists have discovered that Helium may act as a "throttle" for the solar wind. The team hopes that this insight will provide them a better look inside the dynamics of space weather. "Because helium nearly vanishes from the solar wind at its minimum speed, the researchers believe helium might somehow set the minimum speed. Helium is not accelerated efficiently by any process thought to be propelling the solar wind. Instead, it has to be dragged along by the hydrogen: Solar wind hydrogen atoms exert a small electric field that drags the helium out along with it, according to the team."

Comments

no one knows?

[wizardforce]

The team discovered that the abundance of helium increased as the solar wind speed increased, from near zero around the minimum speed to more than four helium atoms for every 100 hydrogen atoms at speeds greater than about 500 kilometers per second (310 miles/second).

helium is heavier than hydrogen snd it requires a higher voltage potential to leave the sun's gravity well- in the case of solar wind the concentration of helium is actually lower than in the sun its self [4% vs 25%] the hydrogen has a better chance of escaping and at higher energies helium levels increase.

Re:no one knows?

[wizardforce]

While you're probably right when you say that the cause of the slowing is that the alpha particle is four times heavier than the proton, you are very wrong to bring in voltages. The solar wind is blown out by the pressure gradient, electic potentials have nothing to do with it. And the wind itself is quasi-neutral, meaning that the number of positive and negative charges in a non-infinitesimal volume is approximately equal. Thus an electric field couldn't move this plasmas anyway. And what do you mean when you say that "in the case of solar wind the concentration of helium is actually lower than in the sun its self [4% vs 25%]"? While there probably are some differences between the solar interior and the coronal wind, the ratio of helium to hydrogen is more like 1/10 and 1/20, respectively. Coronal abundances are still under debate, though. The figure of 4% is plausible for the solar wind, but 25% is much too high for the interior.
ah but solar wind is affected by the magnetic fields and electrical fields present- also the temperature of the corona is significant but even if the primary driving force for solar wind is a pressure gradient, it still obeys equations that describe the velocity of gases and the probability of gas escape from the sun. as for the soalr abundances of helium I was referring to the total helium abundance, not just in the corona. the corona is a relatively thin envelope of gas that extends far enough out to decrease the quantity of helium that is present. the equations also predict that at higher velocities [energies] the quantity of helium increases- these equations are much similar to reaction rate cross section equations in that you calculate relative to an energy barrier- in this case the gravity well as well as the energy and mass of the particles being leaked from the corona.

Re:I don't buy it

[Anonymous Coward]

it's a plasma. without electrons, it's a positive ion.

A clarification

[voislav98]

The Science Daily article gets stuff a bit wrong. The hydrogen mentioned is not hydrogen it's protons (hydrogen without the electron), which are accelareted by the Suns magnetic field. Helium, being a neutral atom, is much less affected by the magnetic field and it moves much slower than the charged protons. Now, charged particles have a very high probability of colliding with a neutral atom (much highr than the neutral atom has), so protons will keep colliding with helium which will slow them down. The analogy is the bumper cars, except helium is a bumper 18-wheeler. So basically, the speed of fast protons will be reduced to the speed of the slow helium atoms by all these collisions. Why is this making the /. is beyond me, not the sort of sensationalist "we're all doomed" or "we're going to be OK" stuff.

Re:I don't buy it

[mbike]

This is not neutral hydrogen therefore it is highly affected by the electric field. This plasma has come from the sun which is way to hot for molecules or neutral atoms for that matter. The article does make good sense.

The relevant quote...

[FuzzyDaddy]

"At the minimum speed--the speed where the solar wind is no longer able to drag out helium--the solar wind itself can't escape either," said Dr. Keith Ogilvie.

Re:long range satellites

[Anonymous Coward]

It's a common misconception that solar wind drives a solar sail. This is really incorrect - in fact, solar wind destroys solar sails.

The momentum of photons striking a solar sail is what makes the ship go.

Re:Helium is a byproduct of wind speed, not cataly

[Zancarius]

I have to agree with this sentiment. The article seems to have been targeted at a fifth grade reading level (or below) and was quite painful to read. It isn't Science Daily's fault, however, as it appears the article was not an "adaptation" but rather a blatant reprint of the original press release. Oh, silly me, I forgot one minor detail: Adaptations are little more than a copy and paste away!

The WIND-SWE group appears to have links to some of the papers they have presented. I'm not sure of the relevancy but it might make for a worthwhile read to curious minds.