New theory unravels magnetic instability

spaceref.com ^ | 10 Dec 02 | Los Alamos

[RightWhale]

PRESS RELEASE

Date Released: Monday, December 09, 2002

Los Alamos National Laboratory

New theory unravels magnetic instability

Reconnection, the merging of magnetic field lines of opposite polarity near the surface of the sun, Earth and some black holes, is believed to be the root cause of many spectacular astronomical events such as solar flares and coronal mass ejections, but the reason for this is not well understood. Researchers at Los Alamos National Laboratory now have a new theory that may explain the instability and advance the understanding of these phenomena.

Theorists Giovanni Lapenta of Los Alamos National Laboratory's Plasma Theory group and Dana Knoll of the Lab's Fluid Dynamics group presented their findings at the American Geophysical Union meeting in San Francisco at the Moscone Convention Center.

The theory is based on a 19th century mathematical observation called Kelvin-Helmholtz instability. "What we are trying to determine is why magnetic field lines loop out from the surface of the sun, reconnect and then fall back," said Lapenta. "And why these systems, which look very stable, are in fact quite unstable."

According to Lapenta, reconnection rates based on resistivity are orders of magnitude too slow to explain observed coronal reconnections. One possible mechanism that provides fast reconnection rates is known as "driven" reconnection-where external forces drive field lines together in a way that is independent of resistivity. Lapenta and Knoll believe that related work focused on magnetic field line reconnection in Earth's magnetopause has shown that the Kelvin-Helmholtz instability can cause compressive actions that push field lines together and drive reconnection. "We propose that the same mechanism at work in the magnetopause could conceivably be at work in the solar corona and elsewhere," said Lapenta.

In this theory, motion on the visible surface of the sun - the photosphere - leads to twisting deformation waves that move through the chromosphere, a layer of solar atmosphere just above the photosphere, growing larger as they move and emerging with a rapid increase of speed through the sun's corona, or outer atmosphere. This rapid change in speed, or velocity shear, injected into the corona can cause magnetic loops to reconnect, according to Lapenta.

"We have conducted a series of simulations and shown that indeed reconnection can be achieved trough local compression driven by Kelvin- Helmholtz and that the reconnection rate is not sensitive to resistivity," said Lapenta.

From this beginning point, Lapenta hopes to study the processes tied to motion on the surface of the sun to better understand why these "velocity shears" occur and how they move away from the sun and lead to CMEs and other solar events, and to apply this knowledge to better understanding the magnetic fields around the earth and the disc-shaped rotating masses, or accretion discs, that form around some black holes.

[LibWhacker]

Apologies. I take that back. I was looking at the wrong formula. You could do it (from another web site):

When we consider the motion of a small object orbiting a large object (such as the Moon orbiting Earth, or Earth orbiting the Sun), there is a simple formula relating the mass M of the central object, the size a of the small object's orbit, and the period P of the orbit:

P2 =

4 p2 a3 G M

.

This is the general form of Kepler's Third Law. If you know two of the three quantities (M, a, or P), you can use this law to compute the third one. For this formula you must use a in meters, P in seconds, and M in kilograms.

But we wouldn't want to do this because if we brought Mars close enough to be useful to us (i.e., not on the opposite side of the Sun from Earth), it's not going to be a two-body problem anymore and I think you'd risk collision. :-)

[LibWhacker]

One possibility is to bring objects like asteroids into Earth orbit. RightWhale knows a lot about this. Wouldn't want them to be too big, however, or you'd start messing around with the tides.

[muleskinner]

I have a Kelvin-Helmholtz instability in what looks to be a salsa jar

[RightWhale]

we'd collide

Do not neglect the Lagrange points in your orbital calculations.

[RightWhale]

you'd start messing around with the tides

That's true, too. Any planetary engineering should be over and done with before we attempt to inhabit the new system. Plus, be very careful about upsetting the balances of earth's ecosystems while things are being moved into position. Green attitude, but be careful anyway.

[RightWhale]

What's huh? Leave Mars alone. Venus is the one we want.

[r9etb]

Does anyone here, with professional experience in the field, have any thoughts as to whether it may eventually be feasible to shove Mars into Earth's orbit, thus causing it to acquire a climate similar to Earth's.

The delta-V required would be something on the order of 5500 m/sec.

Assuming the thruster(s) had an Isp of 2000 seconds, the propellant required would be approximately equal to the mass of Mars itself (~3.5e23 kg).

So, no. It doesn't sound feasible.

[MHGinTN]

Whew! What a relief. I was starting to worry about the inertial moments we'd lose.

[RightWhale]

We might use propellant for attitude control, but the main delta vees will be accomplished through gravity. That is, unless we find a way to control gravity, we will use other masses to adjust orbits, and it won't be quick.

For example, the momentum of Venus/Mercury could be exchanged and balanced with Mars and other outward moons of Jupiter and asteroids. It might be advisable to smash asteroids into Mars, and maybe the moon as well, to introduce certain missing volatiles while we are adjusting orbits.

[Hot Tabasco]

it may eventually be feasible to shove Mars into Earth's orbit, thus causing it to acquire a climate similar to Earth's.

I don't think we can find enough people to go up there and jump up and down enough to get Mars slipped into the proper orbit.

[Sentis]

It would take years before there would be breathable air. Moving it to Earth's orbit won't fix that problem either. Having an atmosphere at all will be a good thing and make it easier to use the planet as no special space suits will be needed. Moving it to Earth's orbit has other problems we run the risk of making Mars too hot for comfortable living. Becuase Mars has more CO2 than earth locked in the Polar caps it is reasonable to assume once released (which will happen in Earth orbit) it will remain in the atmosphere of Mars rather than escape into space making Mars too hot to be Habitable. The Martian icecaps are perfect to create a nice temperate climate where it is. In fact because Mars will have smaller oceans when the water is released. Mars will have double the habitable land as Earth and all the oceans it does have will be fresh water for the first few thousand years.

[LibWhacker]

. . . the propellant required would be approximately equal to the mass of Mars itself (~3.5e23 kg).

Further proof that such a thing should never be necessary; if we that much energy at our disposal, there would certainly be no need to bring a whole planet back home with us.

[r9etb]

For example, the momentum of Venus/Mercury could be exchanged and balanced with Mars and other outward moons of Jupiter and asteroids.

Hell, if you had access to the weird science required to do this, I think it wouldn't be necessary to move planets around for habitability.

[RightWhale]

That's right. I'm just trying to stay within the bounds of common experience. Everybody knows about living on a planet. The real future if we ever get out of this gravity well is to live on or in artificial ships of all sizes and designs and all orbiting the sun in different orbits, and a few taking off for parts unknown.

[Sentis]

Heres my question. why does everyone here want to move the damn thing rather than discuss ways we can terraform it right now. Is the nuclear option so farfected, or are people so scared of Nuclear weapons they refuse to discudd the option. I have had this trouble when this topic has come up on other boards I thought the people here would be much more open to use of these weapons especially when put to such a noble cause.

[DannyTN]

I like the Venus idea.
Couldn't we build a satelite to block some of the sunlight reaching Venus, cooling it down.
We would need a way of reducing the amount of sulfur in the atmosphere, probably through the use of bacteria.
You would have a planet close to earth's size and orbit capable of sustaining an atmosphere.

[DannyTN]

I'm for it, provided that we are sure that Mar's would retain the atmosphere once we create it.

If not why don't we crash some asteroids into it. Preferably asteroids with large ice content.

That could have the same effect of heating up the existing water without the irrational fear of radioactivity. plus you would be adding mass increasing the ability of Mars to retain the atmosphere.

[r9etb]

Heres my question. why does everyone here want to move the damn thing rather than discuss ways we can terraform it right now.

Personally, I have problems with your claim that the nuke would "burn" the CO₂ to create oxygen. And even if that did happen, you have to consider how many ground-burst nukes would be required to release significant amounts of oxygen, etc: I'm guessing it would number in the high thousands. With ground-bursts comes radioactive fallout.....

[Sentis]

Venus has another Nuclear option :) (yeah I have only one thing on my mind right now. We could nuke the equator throwing huge clouds of dust into the atmosphere creating a global nuclear winter. at the same time we could pinpoint volcanos on the surface nuking them to cause them to erupt releasing huge amopunts of water vapor. This water vapor along with particulate matter left in the atmosphere by the detonations would help create storms which could theoretically decrease the amount of sulfer in the atmosphere at the same time cooling the planet. It however would take years longer to terraform than Mars.

[DannyTN]

We could also move additional asteroids into place around Mars as moons.
This would increase the amount of reflected sunlight reaching Mar's surface. Plus creating a tidal effect to aid in warming. If we overdo it we can always nuke one or more new Mars moons into oblivion.