Tag Archives: Van Allen Belts

The Ever-changing and Skepticized Van Allen Belts

The Van Allen belts are two radiation belts. These are zones of electrically charged particles which are poised, encompassing the Earth far above the surface, and held there by the planet’s magnetic field. The first of the belts was discovered in early 1958 through data collected by Explorer I (the United States’ first space satellite) and the Explorer III and Pioneer satellites, under James Alfred Van Allen and his team at the University of Iowa.

Similar radiation belts have since been found surrounding other planets, but the term of Van Allen belts only refers to those two belts (and sometimes other belts that are transitorily formed) which surround the Earth. They have been dubbed the Van Allen belts after the American physicist credited with their discovery.

Each of the two belts surrounds the Earth in a sort of doughnut-shaped formation. The inner belt reaches from approximately 600 to 3,000 miles above the Earth, and the outer belt from about 9,300 to 15,500 miles above the Earth. Astronomers have determined that the belts consist of many electrically charged particles, like protons and electrons. Earth’s magnetic field traps these particles, directing them to the magnetic poles.

The particles move in spiral paths along a system of flux lines, curving from the north magnetic pole to the south magnetic pole. As the particles come nearer either pole, the converging flux lines reflect them toward the opposite pole. This effect keeps the particles of the Van Allen belts bouncing between the poles. The belts receive new particles from the solar wind, a continuous stream of charged particles emitted from our sun.

Chart Showing the Van Allen Belts in Proportion to Earth

 

Other particles can be gained by solar flares and cosmic rays. Intense solar activity can disrupt the belts, leading to magnetic storms. Such disruptions also affect radio reception, cause surges in power lines, and produce auroras.

Ever since their discovery, the Van Allen belts have concerned and inspired people’s minds. Hollywood feature film and TV producer, writer, and director Irwin Allen came out with his science fiction movie Voyage to the Bottom of the Sea in 1961, three years after the discovery of the first belt. The main plot conceived by Allen and Charles Bennett revolves around saving all life on Earth from the natural inferno that was created when a meteor shower pierced the Van Allen radiation belt, catching it ablaze.

Ice burgs begin to melt in the Arctic, entire forests are engulfed in flames, and the crews of sea-going vessels traveling on the ocean’s surface are baked alive. Eventually, scientist Admiral Harriman Nelson proposes to shoot a nuclear missile from his submarine Seaview into the burning belt at a certain projection and time, which would, in theory, overwhelm and extinguish the skyfire, essentially “amputating” the belt from the Earth.

Scene from Irwin Allen’s 1961 Film Voyage to the Bottom of the Sea. Source: 20th Century Fox.

 

Even today, decades later, people are concerned about the radiation belts. A prominent group of physicists wants the belts eliminated altogether. A plan was even suggested in which long conducting tethers that are charged with a high voltage are deployed from satellites into the belts. It would force charged particles that come into contact with the tethers to have their pitch angle altered.

Over time, theoretically, this would dissolve the inner belts. The belts pose certain difficulties and dangers (mainly caused by radiation) whenever a satellite, telescope, or human is to be launched into outer space. There is a decent scientific argument in that these belts provide anything useful, or that we could do away with them without a negative effect.

According to some, if the belts were not there, the Earth would no longer possess a magnetic field. That means that cosmic ray particles would be at liberty to collide with our atmosphere in larger quantities, resulting in a higher background level of secondary “air shower neutrons”, leading to higher doses of background radiation on the surface. If the Van Allen belts were gone, it would definitely impact human life.

Other sources:

The World Book Encyclopedia Vol. 20. World Book, Inc., 1987.

Radio.

We’ve (unknowingly) created a radiation shield around the Earth using radios

Humanity’s effects aren’t contained to the planet’s surface alone but go all the way out to space, a new paper reports.

Radio.

While we’ve left a pretty obvious trace on the face of the planet, the one we’ve left on our near-space environment is less apparent — but there is a trace, scientists found. A certain channel of communication, known as very low frequency (VLF) radio, has been found to interact with particles in space and alter their movement patterns. These interactions can even create an impromptu shield around Earth, which protects against high-energy space radiation.

The finding comes as part of a more comprehensive paper on human-caused space weather phenomena.

Radio shield

VLF channels are transmitted from ground stations at huge power levels, and it’s easy to see why — the most common use of these channels is to maintain communications with submarines, so the signal needs to be strong enough to pass through a lot of water and in some cases, soil. But because of their energy, these radio signals also extend far beyond our atmosphere. And because they’re so widely used, these stations cover the Earth in a VLF bubble.

Previous research has discovered that under the right conditions, radio signals in the VLF and nearby spectrum can interact with and affect the properties of the high-energy radiation fields around the planet. in fact, it’s so powerful that NASA’s Van Allen Probes, which study electrons and ions high above Earth’s surface, can reliably pick up on the bubble.

Which was fortunate, because it allowed the team to pick up on one curious fact: that the VLF bubble seems to extend outwards precisely to the inner edge of the Van Allen radiation belts. These belts are bodies of charged particles held at bay by Earth’s magnetic field — think of them like a purgatory for space radiation.

The team speculates that in the absence of VLF signals, the belt’s lower limit — the so-called “impenetrable barrier” would likely stretch far closer to the planet’s surface. Comparing the extent of the belts recorded with the Van Allen Probe today with the same value recorded by satellite in the 1960s, when VLF transmissions were more limited, shows that the barrier has indeed been pushed outwards.

The discovery offers a relatively cheap and simple system for terraforming planets with excess surface radiation. Plans are also underway to test whether a VLF signal source in the upper atmosphere could be used to scrub the extra charged particles which add up in the belts during periods of intense space weather — such as when the sun erupts with giant clouds of particles and energy.

The full paper “Anthropogenic Space Weather” has been published in the journal Space Science Reviews.