Van Allen Radiation Belts

Before we dive into the Van Allen Radiation Belt, let's start with solar wind. The Sun constantly ejects plasma, mostly consisting of protons and electrons, out into space known as solar wind. Some solar wind carrying charged particles reaches Earth. The intensity of the solar wind varies depending on the temperature, velocity, and density from different regions of the Sun it is ejected from.

Although most solar wind that reaches Earth is slow speed wind, high speed solar wind and powerful bursts of plasma from the sun, known as coronal mass ejections (CMEs) can cause damage. The immense radiation in the charged particles of solar wind is dangerous to satellites and would be especially harmful if it reached Earth's surface.

Thankfully, we have Earth's magnetic field and the Van Allen Radiation Belts that protect us from solar wind and even more powerful coronal mass ejections.

The Van Allen Radiation Belt consists of energetic charged particles, mostly from solar wind, that have been captured and held by the Earth's magnetic field. It consists of two belts: the inner belt, containing most of the protons low-energy electrons, and the outer belt, with more of the high-energy electrons. There is an "empty" region between the two belts devoid of energetic charged particles due to the plasmasphere. The belts are often described as a circular particle accelerator because of the way the magnetic field stores these charged particles in the belts as waves in surrounding areas energize the particles to such high speeds.

Increased solar activity, such as a coronal mass ejection or solar storm, causes the Van Allen Radiation Belts to bend and swell, or even form a third belt, as the Van Allen Probes launched in August 2012 recorded. While the belts do contain radiation, the density of particles varies along each belt, from areas with more clusters to other areas that are more dilute. Astronauts passing through these belts at high speeds won't feel the particles and won't be too adversely affected by the radiation; these particles mostly affect, and are only detected by sensitive instruments.

The inner edge of the outer radiation belt is the main protection layer between us and solar activity. The plasmasphere, a region of the magnetosphere with cool plasma undergoing particle motion, extends to the inner barrier of the outer radiation belt, scattering any high energy particles from the outer belt or farther out in space and preventing them from reaching Earth. This defined edge of the outer radiation belt deflects most of the energetic and harmful particles from affecting life on Earth, though satellites may still be in harm's way. In the case of strong solar activity, the plasmasphere is pushed inward along with the Van Allen radiation belts. 


We can even hear the particles moving inside the Van Allen Radiation Belts and near Earth, creating sounds that depend on the medium they are traveling through. These sounds, ranging from whistler waves to chorus waves, can be captured and modified to be heard by the human ear.

While so much has been discovered about the Van Allen Radiation Belts, more information about how the particles enter the belts, how they behave and interact with other particles and forms of radiation, and what processes accelerate the particles are still yet to be understood.

References:

Comments

  1. waterJanuary 6, 2022 at 11:50 AM

    Great article about Van Allen Probes. I'd like to see the first picture being enlarged as the fonts are small in the picture. It will be even better to add a description under each graph to show the relationship between the text and the illustration.

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