An article published in “Journal of Geophysical Research” describes a study on the Van Allen belts, two donut-shaped energetic formations surrounding the Earth. Two twin spacecraft originally called the Radiation Belt Storm Probes (RBSP) and later Van Allen probes were launched by NASA on August 30, 2012 to study the belts and are allowing us to learn a lot about them. The latest discovery concerns the variability of their shape.
The shape of the Van Allen belts has been described as a ring or a donut since they were discovered in the ’50s. However, the space probes that are studying them allowed us to understand that their shape is variable and depends on the type of electron examined. The energy levels are crucial in formations composed of charged particles and according to this new research if we consider them separately we get a very different impression.
Analyzing the electron energy levels, we no longer have the classic image of the two belts with an intermediate region. Analyzing the low energy electrons, the inner van Allen belt turns out to be the widest while analyzing the high energy ones the situation is reversed. Finally, analyzing the highest energy ones the inner belt disappears completely.
As if that wasn’t enough, the structure of the Van Allen belts can be altered by geomagnetic storms. The coronal mass ejections or the high-speed solar wind coming from the Sun interact with the Earth’s magnetic field. The consequence is a change in the amount of energetic electrons in the belts. It’s a temporary phenomenon and after some time the belts return to their normal configuration.
The mission of the Van Allen probes is also important to understand the best ways to protect the satellites in orbit and especially astronauts. Now we know better the energy levels that may be present in various areas of the magnetosphere and consequently which orbits are more dangerous and in what situations.
For these reasons, at the end of August 2015, NASA decided to extend the mission of the Van Allen space probes for two more years. The magnetosphere is essential as a shield that protects the Earth from solar activity peaks so knowing the secrets of the Van Allen belts is important for electronic devices in orbit but also for the entire power grid on Earth.
