Surprise: Solar System "Force Field" Shrinks Fast

As charged particles flow out from the sun, they eventually bump up against interstellar medium—the relatively empty areas between stars. These interactions "inflate" a protective bubble that shields Earth and the entire solar system from potentially harmful cosmic rays (solar system pictures).

Now IBEX has surprised astronomers by showing that this force field-like structure, the heliosphere, is an unexpectedly dynamic, unpredictable boundary.

For starters, it's been assumed that the heliosphere's expansion and contraction follows the sun's roughly 11-year activity cycle, during which the flow rate of charged particles, or solar wind, fluctuates.

But when scientists compared IBEX maps of the heliosphere taken just six months apart, the researchers found that it had shrunk to a much greater extent than expected. (See "Sun's Power Hits New Low, May Endanger Earth?")

This quick shrinkage could be a concern for astronauts, said McComas, of the Southwest research Institute in San Antonio, Texas. That's because, as the heliosphere shrinks, it lets in more cosmic radiation, which can compromise the body's immune system.

"To this day the science team can't agree on exactly what causes the knot or the ribbon, but by comparing different sky maps, we find the surprising result that the region is changing over relatively short time periods. Now we have to figure out why."

June 24, 2005: Opposite charges attract. Like charges repel. It's the first lesson of electromagnetism and, someday, it could save the lives of astronauts.
NASA's Vision for Space Exploration calls for a return to the Moon as preparation for even longer journeys to Mars and beyond. But there's a potential showstopper: radiation.
Space beyond low-Earth orbit is awash with intense radiation from the Sun and from deep galactic sources such as supernovas. Astronauts en route to the Moon and Mars are going to be exposed to this radiation, increasing their risk of getting cancer and other maladies. Finding a good shield is important.

The spheres would be made of a thin, strong fabric (such as Vectran, which was used for the landing balloons that cushioned the impact for the Mars Exploration Rovers) and coated with a very thin layer of a conductor such as gold. The fabric spheres could be folded up for transport and then inflated by simply loading them with an electric charge; the like charges of the electrons in the gold layer repel each other and force the sphere to expand outward.

It sounds wonderful, but there are many scientific and engineering problems yet to be solved. For example, skeptics note that an electrostatic shield on the Moon is susceptible to being short circuited by floating moondust, which is itself charged by solar ultraviolet radiation. Solar wind blowing across the shield can cause problems, too. Electrons and protons in the wind could become trapped by the maze of forces that make up the shield, leading to strong and unintended electrical currents right above the heads of the astronauts.
The research is still preliminary, Buhler stresses. Moondust, solar wind and other problems are still being investigated. It may be that a different kind of shield would work better, for instance, a superconducting magnetic field. These wild ideas have yet to sort themselves out.

Space-borne protective energy systems, like the deflector shields on the fictional starship U.S.S. Voyager, are on the drawing board of real-world scientists.

These "cold plasmas" -- analogs to the sophisticated defensive grids envisioned by Star Trek's creators -- are ambient-temperature, ionized gases related to those found deep within the sun’s core.

Such plasmas are capable of shielding satellites and other spacecraft, making them invisible to radars, or both. Nor will they fry electronics or melt metal.

On Earth, cold plasmas should permit rapid, room-temperature sterilization of food, medical equipment and contaminated civilian and military gear. Low-temperature plasmas could one day also make possible an entire new generation of miniature lasers and ultra-low-energy fluorescent light tubes.

The U.S. Air Force allocates some $10 million a year for research geared toward satellite protection. Of that amount, $2 million is dedicated to low-temperature plasma studies.

A nearer-term application is cloaking. With the proper adjustments, a plasma can be made into a kind of energy mirror, reflecting back or away incoming electromagnetic waves, such as those emitted from ground-based radars. In essence, any spacecraft outfitted with this kind of plasma field would be completely cloaked from the probing attentions of radar operators.

"The idea is to deflect or absorb the energy completely," Laroussi said. "If you absorb the energy --- completely dissipating it within the plasma --- the radar doesn’t see anything. Nothing reflects back."

"This Star Wars stuff is coming," said Igor Alexeff. "Laser and high-power microwave weapons are on the way; they’re almost here. Lasers are fierce weapons. To protect against them, you’d need a very dense plasma, almost a solid. But a good cold plasma could really help out by reflecting or absorbing energy from a microwave-powered war weapon."