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.

[GovernmentShrinker]

I don't want to live anywhere that people can't frolic outside. Bundling up is okay, but wearing breathing apparatus would be awful.

[Sentis]

actually burning CO2 in an nonoxygen environment under the temperatures produced in a nuclear explosion will and does release Carbon ash and Oxygen not to mention lower temperature reactions outside the main explosion that creates a variety of other waste products which will increse albedo. Again, we aren't talking about creating an atmosphere with the explosions alone although the amounts of CO2 released from the poles in the intial explosions should be large. The creation of atmosphere is a process by which waste products from the explosion cause an albedo switch creating a dark blanket of fallout which will cover the icecaps warming them and causing them to enter the atmosphere in a greenhouse effect.

[GovernmentShrinker]

Hey, this is great! Freepers are putting their heads together to figure out how to get us a nice new hospitable planet. Now how do we go about ensuring that the whole planet will be a Constitutional republic, where the government is microscopic and minds its own limited business? Scary thing is, that might actually be harder than moving the planet and/or giving it a comfy climate.

[DannyTN]

I'm not convinced that just because we aren't doing it to meet earth's needs, that it is not that simple.

With earth there is greater precision required because we need a very precise concentrated beam that is convertable back into other forms of energy. However for Terraforming you wouldn't need that level of precision or the ability to convert the energy to other forms.

Perhaps the first step is to construct a solar power grid for earth. The availability of cheap energy on another planet would certainly make colonization a lot more feasible.

I was thinking construct the lens here and send it to Mars. Maybe the lens can double as a solar sail.

I agree that constructing a large lens is a major and expensive undertaking.

Perhaps the solution is to place a lens much closer to the sun and pipe more concentrated solar energy to Mars. You could either establish the initial lens in an orbit around the sun that is synchronized with Mars, or have a mechanism that changes the angle of the lens to keep it pointed towards Mars. That would reduce the size of the lens necessary.

[DannyTN]

Plus the construction of a closer to the Sun lens could double as a great military application.

Oops, wilted your crops. Oops, forced your people to stay inside. Oops, melted your cities.

[Brett66]

Various experts have previously thought along these lines. Here's an article from this site on using huge mirrors to heat Mars:

Technical Part in Terraforming Mars

Orbiting Mirrors

The main reason why Mars is colder than earth is that Mars gets less sunlight than earth. So it seems logical to increase the amount of light that hits Mars surface. This could be done by stationing big mirrors in space. These could be stationed at about 214000 km over the Martian surface. That way, the mirror would stay where it is: the sunlight pushes it outward, the Martian gravity pulls it inward.

But to increase the light that hits Mars by just 2%, a mirror the size of Texas is necessary. More logical to heat up only certain parts of Mars. Zubrin and Mc Kay have shown that a constant temperature rise of only 4 K on the south polar icecap would make the whole carbon dioxide reservoir evaporate to thicken the atmosphere by 50 to 100 mbars and heat up the planet by more than 20 K.

A mirror (or solar sail) with a diameter of 125km stationed at 214000 km over the south pole would heat up everything below 70' by 5 K.

This is more than enough to make the icecap melt. In 10 years, the whole icecap would be evaporated and some of the carbon dioxide that is now in the regolith below 70' , would also be liberated into the atmosphere. So we can increase the temperature globally by more than 20 K by warming up the planet regionally.

A mirror of that size seems never the less enormous. Bur don't forget that Mars has a weaker gravity, which makes launch costs much cheaper, it has 2 satellites that orbit close to Mars and have almost no gravity which could be turned into giant solar sail industries if we take rising technology into account.

Another idea is to build bases on the moon that could build smaller sails and let them sail over to Mars. These bases could also export materials to Earth and Mars, like He3, which begins to be used medically.

Cargo that are send to Mars could use solar sails as propulsion. Instead of throwing them away after being used, they could be used ib the reflectors to heat up the planet. Mars is close to the asteroid belt. If an aluminum rich asteroid was found, nuclear reactors with a capacity of 5 MWe (like the ones that will be used for manned flights soon) could rapidly build sails and send them to Mars. Such sails are of a big importance in the terraforming of Mars.

To note is that the construction of such a mirror might be the only thing that needs to be build to terraform Mars. If the temperature needed to let the carbon dioxide that is captured in the regolith escape (also called Td) is under 20 K, the melting of the south polar icecap might do the job of making all the carbon dioxide of the planet escape into the atmosphere.

But if Td is higher, extra heating through greenhousing will be necessary.

[DannyTN]

Oops evaporated your water reservoirs!
Got Milk?

[Sentis]

I didnt say a lense wont work. I said it is cost prohibitive. It wont ever be done. On the other hand sending nukes out to Mars could be as simple as a presidential executive order or a under the table secret project. Even russia could do it. Not Ten years from now not a hundred years from now. Russia or America could have the rocket on its way in little over a year, both countries already have the technology. The United States may have to build a new version of the Saturn Rocket or buy its conterpart as army surplus from Russia.

[RightWhale]

Forget the nukes. They won't do anything. It might be noted that all the nukes on earth would barely suffice to excavate Iraq to a depth of 3 feet. Effect on a Mars polar cap = zero, zilch, nada.

[DannyTN]

To build a mirror that is just 50 x 50 miles wide you would need the following.

Using hexagonal shaped lens parts that are 2 yards by 2 yards wide preconfigured into apparatuses that will unfold 36 such lenses into 6 groups of 6 for further assembly in space. You would still need 2,000,000 such assemblys to cover the 309 million square yards that a 50x50 mile mirror would need. Not impossible but Sentis is right that such a mirror would be expensive.

So what about the closer to the sun lens idea. How close to the sun can we get before the lens useful life begins to deteriorate quickly? And will that reduce the lens size to a reasonable effort to build?

Also go back to the extra moon theory. If you could position asteroids in place and use them as the mirror instead of constructing a lens. You may be able to get the desired heating effects.

But it still comes back to, can Mars retain the atmosphere, or do you need to crash things into Mars to increase it's mass and see how much additional heat the crashing does?

[DannyTN]

Are you sure? Shouldn't we try that on Iraq before we rule it out?

[Sentis]

The polar icecaps on mars aren't made of dirt they are made of froxen CO2 and H2O. CO2 freezes at a temperature of -109 F the temperature the ice caps are only slightly less than that figure. This means that a few startegically placed nukes could free lots of CO2. And Again, the nukes aren't there to free all the ice they are there merely to cover it in a blanket of nice warm radioactive ash.

[DannyTN]

Same concept would apply to venus.
If it is possible to place an object in orbit around the sun in an orbit that is synchronous to Venus, then the closer you get to the sun, the smaller the shadow making device needs to be.

Perhaps we could combine them. Use the same lens to divert sunlight away from Venus and send it to Mars.

[RightWhale]

You'll just cut a couple of divots. Won't do much good.

[jpsb]

Heating up it's core would be a good idea too.

[DannyTN]

Anybody know the math on blocking sunlight??

If you could pick the optimal point between Venus and the Sun to block light, how big would a shield have to be to block all of the sunlight from Venus or just 1/4 of the sunlight?

[RightWhale]

The sunshade would need to be between 4000 and 8000 miles diameter to put Venus in 1/4 to full shade.

[DannyTN]

Is that regardless of where between the Sun and Venus the shield is located?

It seems to me that with Venus having a diameter of 12000km, that 4000-8000 miles would represent the size of the shadow that needs to be cast.

But as you move towards the Sun the smaller the object casting the shadow would need to be, up to a point, then the object would simply appear like a sunspot as it gets dwarfed by the diameter of the sun.

At some point there should be a focal point in which a much smaller device should suffice, but it may still be huge. The blocking device wouldn't have to put 1/4 of venus into total eclipse either. Partial eclipse would be fine as long as 1/4 of the total rays are blocked.

[RightWhale]

The shield will have the smallest diameter if it is right at Venus. As it is farther from Venus and closer to the sun, it will need to be larger. Where is that movie of the recent solar eclipse of earth as seen from space?

[NukeMan]

What has an Isp of 2000 sec? Don't liquid H and Liquid O2 rockets have an Isp of ~450 seconds?