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NASA THEMIS satellites change solar storm theory

  • 25 April 2009
  • Written by 
  • Published in Space
The THEMIS discovery changes how scientists think about charged solar particles (plasma) from the Sun interacting with the magnetic field (magnetosphere) of the Earth. They can now more accurately measure the amount of energy released, which causes magnetic storms and intensifies auroras.

In fact, Vassilis Angelopoulos (University of California, Los Angeles), the principal investigator for the THEMIS mission, stated, “The discovery overturns a long-standing belief about how and when most of the solar particles penetrate Earth's magnetic field, and could be used to predict when solar storms will be severe. Based on these results, we expect more severe storms during the upcoming solar cycle.”

The maximum solar activity within the upcoming solar cycle is predicted to occur around 2012. Scientists are now predicting very severe solar storms at this time.

THEMIS, which stands for “Time History of Events and Macroscale Interactions during Substorms,” are a set of five NASA satellites that study energy released from the Earth’s magnetosphere.

When these energy bursts within the solar wind are very intense, solar storms (“substorms”) are produced, which produce brightly visible auroras in and around the North and South Polar regions of Earth. They also disrupt our communications systems on and above Earth.

According to the NASA article Sun Often "Tears Out A Wall" In Earth's Solar Storm Shield, “It had been thought that when the sun’s magnetic field is aligned with that of the Earth, the door is shut and that few if any solar particles enter Earth’s magnetic shield. The door was thought to open up when the solar magnetic field direction points opposite to Earth’s field, leading to more solar particles inside the shield.”
However, measurements by the THEMIS satellites find that this belief by scientists is not true.

In fact, Marit Øieroset (University of California, Berkeley), along with colleagues, published a paper in May 2008 within the journal Geophysical Research Letters that counters this belief.

Find out what they discovered on page two.

Dr. Øieroset states, "Twenty times more solar particles cross the Earth’s leaky magnetic shield when the sun’s magnetic field is aligned with that of the Earth compared to when the two magnetic fields are oppositely directed.” [NASA]

The discovery by THEMIS researchers were reported on Friday, April 24, 2009, at the “General Assembly 2009” meeting of the European Geophysical Union (EGU) in Vienna, Austria.

These magnetic holes are produced in the magnetotail, the region of the magnetosphere on the side of the Earth that faces away from the Sun. The holes are produced when the magnetotail is stretched past its breaking point, which creates a huge and sudden release of energy.

This gigantic release of energy produces two spiraling vortices that turn opposite of each other.

These “plasma tornadoes” (as they are being called), or spiraling vortices, were measured by THEMIS as being about 70,000 kilometers (43,500 miles) in length and about the same width as the Earth, about 12,800 kilometers (8,000 miles).

They have speeds of over 1.6 million kilometers per hour (1 million miles per hour).

In addition, according to the Fox News article Electricity measured inside space tornadoes, “THEMIS found that space tornadoes can produce electrical currents greater than 100,000 amperes (for comparison, a 60-watt light bulb draws about half an ampere).”

Joachim Raeder (University of New Hampshire), who also has published journal articles with respect to THEMIS and solar storms, states. "If the solar field has been aligned with the Earth's for a while, we now know Earth's field is heavily loaded with solar particles and primed for a strong storm. This discovery gives us a basic predictive capability for the severity of solar storms, similar to a hurricane forecaster's realization that warmer oceans set the stage for more intense hurricanes. In fact, we expect stronger storms in the upcoming solar cycle. The sun's magnetic field changes direction every cycle, and due to its new orientation in the upcoming cycle, we expect the clouds of particles ejected from the sun will have a field which is at first aligned with Earth, then becomes opposite as the cloud passes by." [NASA]

For additional information, along with a video and pictures, check out the New Scientist article “Giant space tornadoes create Earth's auroras.”

More information about the THEMIS mission is found at THEMIS/Berkeley and THEMIS/NASA.


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