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On Boundary Of Earth’s Magnetosphere, NASA Discovers New Magnetic Waves

April 17, 2013
Image Caption: Earth is surrounded by a giant magnetic bubble called the magnetosphere. As it travels through space, a complex system of charged particles from the sun and magnetic structures piles up in front of it. Scientists wish to better understand this area in front of the bow shock, known as the foreshock, as it can help explain how energy from the rest of space makes its way past this boundary into the magnetosphere. Credit: NASA/GSFC

redOrbit Staff & Wire Reports – Your Universe Online

Analysis of data collected by NASA´s Wind spacecraft as it traveled through the front of the Earth´s magnetosphere from 1998 through 2002 has revealed a special type of magnetic pulsations, scientists from the US space agency revealed on Tuesday.

The magnetosphere, a giant area of space created by the Earth´s magnetic fields as it travels around the sun, produces a standing bow wave or bow shock as is travels through space. In the very front of this bow wave is a complex and turbulent system known as the foreshock, NASA officials explained.

Conditions in the foreshock change in response to solar particles that stream in from the sun, moving magnetic fields and a large number of waves of different speeds through the region, they added.

In order to understand what happens at the frontal boundary of the magnetosphere — and to better understand how the radiation and energy from the sun crosses through it and moves closer to our planet — the space agency sends spacecraft like Wind into this region. During its 17 trips to the foreshock region, Wind observed the changing conditions while deciphering new information about the physics of the zone.

While reviewing data provided by the spacecraft during its visits there, the deputy project scientist for Wind at NASA´s Goddard Space Flight Center Lynn Wilson said that he and his colleagues discovered “some cool squiggles” that “turned out to be a special kind of magnetic pulsations called short large amplitude magnetic structures, which we call SLAMS for short.”

According to NASA, SLAMS are waves that have one large peak, somewhat like giant rogue waves which can develop in the deep ocean. By studying the regions surrounding these waves and how they propagate, Wind scientists could shed new light on what accelerates narrow jets of charged particles back out into space and away from our planet.

“Tracking how any phenomenon catalyzes the movement of other particles is one of the crucial needs for modeling this region. In this case, understanding just how a wave can help initiate a fast-moving beam might also help explain what causes incredibly powerful rays that travel from other solar systems across interstellar space toward Earth,” the space agency said.

“The material pervading this area of space — indeed all outer space — is known as plasma. Plasma is much like a gas, but each particle is electrically charged so movement is governed as much by the laws of electromagnetics as it is by the fundamental laws of gravity and motion we more regularly experience on Earth.”

Wilson and his associates detailed their findings in a study published online last month in the Journal of Geophysical Research. David Sibeck, co-author of the paper and a space scientists at Goddard, explained that even little space weather events can have a big impact on things, and that the front of the magnetosphere is “a crucial place to understand which small things can lead to big results.”

For approximately four decades, researchers have known that particles appear to be reflecting off the magnetosphere, leading to the creation of intense particle jets known as field aligned ion beams. Previously, they did not know exactly why that phenomenon occurred, but the Wind data helps shed new light on the process. Wilson said that the solar wind is constantly moving towards our planet´s bow shock, and then bounces off of it.

“These structures get excited upstream and they start to grow and steepen, kind of like a water wave, but instead of breaking and tumbling over, they stand up, getting bigger and faster,” he explained. Wilson said that the SLAMS try to move against the gale of solar wind that is streaming towards them, but they ultimately wind up getting pushed back, essentially creating a new boundary or bow shock at the forefront of the magnetosphere.

“Without the SLAMS, one would expect incoming particles from the solar wind to skip and slide along the outside of the bow shock, the way flowing water in a river might move around a large rock,” NASA explained. “But the SLAMS create a kind of magnetic mirror, causing the solar particles to reflect, attenuating them into one of these field-aligned ion beams, shooting out along magnetic fields back out and away from Earth.”

The Wind data does not show the cause-and-effect relationship between the two phenomena, only that both are present. However, the space agency noted that ion beams were not observed in the space between the true bow shock´s front and the SLAMS — only from the magnetic pulsations outwards into space. The beams only appeared after the SLAMS were able to form completely, suggesting that the SLAMS themselves act like a magnetic mirror, reflecting the particles outward and leading to the beams.


Source: redOrbit Staff & Wire Reports - Your Universe Online



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