'Whistler waves'

In 1962, the United States launched "Operation Fishbowl," conducting a nuclear test called "Starfish Prime" at high altitude above the Pacific Ocean. In the ensuing months, many satellites in Earth's orbit became inoperable. Luckily, there were only a few of them circling Earth at the time. But what scientists discovered afterwards was even more dramatic: The nuclear explosion had created a new radiation belt around earth which was significantly more intense than those which exist naturally. As a result, no satellite could safely pass through this zone until the 1970s.

This incident, rarely spoken of today, is still very much alive in the memory of scientists and military forces all over the world, says Frank Gaffney, the founder and president of the US Center for Security Policy.

Gaffney argues that warmongering countries keen on demonstrating their power but unable to fire long-rabge nuclear missiles might decide to detonate a nuclear bomb in the upper atmosphere above their own territory.

"To bring harm, all that you have to do is just launch a rocket straight up above the Earth," Gaffney told DW.

This would, he says, suffice to destroy the systems that provide cellular communications and GPS all around the globe - which is why Gaffney is calling for a civil defense program so that Americans can protect themselves from potential nuclear attacks, such as high-altitude nuclear explosions.

From satellite to sieve

Both high-altitude nuclear detonations and coronal mass ejections (CMEs) from the sun are capable of producing a huge amount of radiation - high-energy electrons and protons, which would penetrate any unprotected satellites. The sun is powerful enough to disrupt power grids as well as GPS and radio communications on Earth. The electronics of satellites and devices on Earth could be disabled completely.

"Even a small hole from one electron can significantly damage modern integrated circuits in microchips. A burst of millions of electrons, would very soon turn any computer board into a sieve," explains Anatoly Streltsov, faculty member of the Physical Sciences Department at Embry-Riddle Aeronautical University, who has been studying this problem since 2004 and - together with his colleagues at the U.S. Naval Research Laboratory - is looking for a means to counter excessive radiation in the magnetosphere.

Efforts to reduce production costs mean that most satellites have no significant protection from radiation and electromagnetic waves. All countries owning satellites should be prepared for this threat.

Protective waves

In 2012, NASA launched the Van Allen probes - two robotic spacecraft whose purpose is to investigate the regions in the earth's magnetosphere populated with the most energetic charged particles, so-called "killer electrons." These magnetic regions form radiation belts around the Earth, as Van Allen and the US Explorer 1 satellite discovered in 1958.

The goal of the new Van Allen Probes mission is to gain practical knowledge about the physical processes in these regions which will be used to design spacecraft capable of surviving the harsh space environment. "Another objective of this mission is to develop a strong, quantitative understanding of physical mechanisms which can be used for the remediation of killer electrons from the magnetosphere," says Streltsov.

As a way to protect satellites from radiation, scientists propose to use the so-called whistler waves: a type of electromagnetic wave in the very-low-frequency band (1-10 kHz), which if played through the speakers of a radio receiver, sounds like someone whistling. These waves can be used to remove dangerous electrons from the magnetosphere.

Particle rain or remediation

Energetic electrons trapped inside the Earth's magnetic field can be accelerated by the whistler waves, which travel along the magnetic field line from the northern to southern hemisphere within one second.

By increasing the particles' energy, they can be forced to move down into the atmosphere, instead of remaining in the magnetic field. This doesn't damage the atmosphere, because it is very dense compared to space. These electrons subsequently recombine with ions in the ionosphere and form neutral molecules. The end result is that the dangerous radiation is removed from space.

Under natural conditions, there are too few whistler waves in space to cause significant remediation. They are generated naturally by lightning, with the number of whistler waves at any given time being dependent on the weather, both in space and on Earth.

Additionally, naturally occurring whistler waves are very weak. They do not have enough power to remove particles after nuclear explosions or strong CMEs. But scientists say there are natural mechanisms by which the whistler waves can be guided and amplified in the magnetosphere. For example, analysis of the data from the Van Allen Probes found that a small increase of plasma density can cause a guiding and amplification of the whistler waves.

To create a controlled source of whistlers, American physicists are using the High Frequency Active Auroral Research Program (HAARP) array of antennas in Alaska.

"Currently, the process of particle remediation with ground transmitters is being studied quite extensively," says Streltsov. In the future, scientists are considering placing antennas which generate whistler waves atop satellites, carrying out the experiments with remediation directly in the space regions populated by energetic particles.