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Holes in earths magnetic shield
The Earth behaves like a huge magnet and the magnetic field that surrounds the Earth like cocoon that protects it from harmful particles coming from the sun as solar wind- a stream of charged particles spewing from the Sun at 1.6 million km/h- especially during solar storms. The magnetic cocoon diverts the solar wind particles away over the Earth’s equatorial and temperate regions. But if the particles are energetic enough, as is the case during severe solar storms, then they can penetrate deeper into Earth’s atmosphere. But that happens only around the poles where the magnetic lines of force converge, giving rise to spectacular displays of auroras seen in polar latitudes.
But it has now been discovered that occasionally holes appear in Earth’s magnetic shield. Recent observations made by THEMIS (Time History of Events and Macroscale Interactions during Substorms), a fleet of five small NASA satellites, have revealed the largest hole yet seen in the magnetic field that protects Earth from most of the Sun’s violet blasts. Observations from THEMIS show the Earth’s magnetic field occasionally develops two holes, allowing solar wind to penetrate the Earth’s upper atmosphere. The holes are defying many of scientists’ previous ideas on how the interaction between Earth’s magnetosphere and solar wind occurs: From the location of the holes the whole interaction appears to works in a manner that is completely the opposite of what scientists had thought.
It has been known that the Sun’s magnetic field shifts its orientation frequently, sometimes becoming aligned with the Earth, sometime becoming anti-aligned. It was earlier believed that more solar particles entered Earth’s magnetosphere when the Sun’s field was oriented opposite to the Earth’s, but the opposite turned out to be the case here. Data from THEMIS showed that twenty times more solar wind passed into the Earth’s protective shield when the magnetic fields were aligned.
Using computer simulation scientists have been able to find out how the holes develop. They have discovered that two holes frequently develop in Earth’s magnetic field, one at high latitude over the Northern hemisphere, and one at high latitude over the Southern hemisphere. The holes form over the day-side of Earth, on the side of the magnetic shield facing the Sun.
This discovery not only has implications for scientists’ understanding of the interaction between the Sun and Earth’s magnetosphere, but for predicting the effects to Earth during the next peak in the solar cycle.
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