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Van Allen radiation belt

Van Allen belt

 Automatic translationAutomatic translation Category: Earth
Updated June 01, 2013

Van Allen twin probes NASA, launched August 30, 2012, revealed a new radiation belt around the Earth. The mission found a third radiation belt hitherto unknown in these dangerous regions of space.
Van Allen probes consist of two identical satellites, appropriately separated in space to better identify events map this region, catalog the high energy particles and follow the magnetic waves that escape to belts. The magnetosphere was described in 1958 by James Van Allen during measurements by Geiger counters embedded in the first U.S. satellite, Explorer 1. It is at this time that was discovered this area of ​​space known named Van Allen belt. The Van Allen belt, affected by solar storms, is composed of two distinct parts of radiation with different characteristics. The first is closest to the earth is between 700 and 10,000 km altitude, it is constituted mainly of high-energy protons. The second, outer largest, is located between 13 000 and 65 000 km, it consists of high-energy electrons. This discovery demonstrates the dynamic and variable radiation belts of our planet, indeed the third belt has persisted for four weeks and then disappeared, perhaps destroyed by another shock wave, that solar flare of August 31 2012 by Daniel Baker REPT principal investigator at the University of Colorado. This discovery helps improve our understanding of how these areas react to solar activity.
The data collected by the first double spacecraft to analyze the Van Allen belts, were published Thursday, February 28, 2013 in the journal Science. The instrument REPT (Relativistic Electron Proton Telescope) onboard probes revealed a third structure distinct from the Van Allen belt with a second empty area of ​​the space between the two outer belts.
Scientists have observed the third belt for four weeks while a powerful shock wave had hit the magnetosphere. The observations were made by scientists from institutes LASP, Goddard Space Flight Center of NASA, Los Alamos National Laboratory and the Institute for the Study of Earth from the University of New Hampshire. Van Allen probes were designed to help us understand the sun's influence on Earth and near-Earth space by studying the radiation belts at different scales of space and time.

 

The six instruments probes provide the necessary measures to characterize and quantify the processes plasmatic that produce ions and relativistic electrons very energetic. Van Allen probes are part of the wider program (LWS) whose missions were designed to explore aspects of the connected Sun-Earth and that directly affect life and society. Instruments probes permit to measure the properties of charged particles that make up the radiation belts of the Earth, the plasma waves that interact with them, the large-scale electric fields that carry them, and the magnetic field that guides the particles.
Both probes Van Allen have about the same eccentric orbit. These orbits cover the entire area of ​​radiation belts. The greater part of the solar energy is released into space as electromagnetic radiation, mainly in the form of visible light, but the Sun also emits a flow of charged particles, called the solar wind. This solar wind interacts strongly with the magnetosphere of planets and helps clean interplanetary space by ejecting gas and dust outside the solar system. Solar flares send continuously high energy particles in space and time to time, a bubble of plasma radioactive and superheated reaches the Earth. All energetic particles emitted by the Sun towards the Earth, traveling at high speed and are returned permanently to the poles of the magnetosphere. And the solar wind never strikes the surface of the Earth directly.
This magnetic bubble puts us safe from deadly solar radiation. In the Van Allen belt, energetic particles (protons and electrons) are organized around the Earth, depending on the magnetic field strength. This magnetic field acts as a shield deflecting the solar wind electric current which then flows outside the magnetosphere. Exposure, even short-term to flows denser of the belt of Van Allen radiation is fatal to humans. Few men have been on the other side of the magnetosphere against solar radiation death, only the Apollo astronauts who went to the moon crossed the Van Allen belt. Even with a protective shield, the exposure of astronauts was limited to less than an hour.

 Van Allen radiation belt

Image: The Van Allen belt. Two giant bands of radiation called the Van Allen belts around the Earth, were discovered in 1958. In 2012, observations of probes Van Allen showed a third band may sometimes appear. The radiation belts are shown here in yellow, in green are the spaces between the Van Allen belts. Much radiation passes along the magnetosphere without reaching the Earth's surface, but a small portion seeps at the poles austral and boreal where the geomagnetic field is weakest, this correspond an annular zone named "aurora zone", it is between 65 and 75 ° magnetic latitude. Credit: NASA / Van Allen Probes / Goddard Space Flight Center.

nota: Earth's magnetosphere is the space surrounding the Earth beyond the layers of the atmosphere between 700 and 65 000 km of the surface. This boundary, the magnetopause is the membrane that isolates us from interplanetary space dominated by the solar wind.

nota: The solar wind is essentially composed of ions and electrons charged with considerable energy and expelled at a speed of ≈ 450 km/s, by thermonuclear reactions of our star.
 
           
           
 
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