Solar fleet peers into coronal cavities

Sep 20, 2012 by Karen C. Fox
The faint oval hovering above the upper left limb of the sun in this picture is known as a coronal cavity. NASA’s Solar and Terrestrial Relations Observatory (STEREO) captured this image on Aug. 9, 2007. A team of scientists extensively studied this particular cavity in order to understand more about the structure and magnetic fields in the sun's atmosphere. Credit: NASA/STEREO

(Phys.org)—The sun's atmosphere dances. Giant columns of solar material – made of gas so hot that many of the electrons have been scorched off the atoms, turning it into a form of magnetized matter we call plasma – leap off the sun's surface, jumping and twisting. Sometimes these prominences of solar material, shoot off, escaping completely into space, other times they fall back down under their own weight.

The prominences are sometimes also the of a larger formation, appearing from the side almost as the filament inside a large . The bright structure around and above that light bulb is called a streamer, and the inside "empty" area is called a coronal prominence cavity.

Such structures are but one of many that the roiling magnetic fields and million-degree plasma create in the sun's atmosphere, the corona, but they are an important one as they can be the starting point of what's called a coronal mass ejection, or CME. CMEs are billion-ton clouds of material from the sun's atmosphere that erupt out into the solar system and can interfere with satellites and radio communications near Earth when they head our way.

"We don't really know what gets these CMEs going," says Terry Kucera, a solar scientist at 's Goddard Space Flight Center in Greenbelt, Md. "So we want to understand their structure before they even erupt, because then we might have a better clue about why it's erupting and perhaps even get some advance warning on when they will erupt."

Scientists want to understand what causes giant explosions in the sun's atmosphere, the corona, such as this one. The eruptions are called coronal mass ejections or CMEs and they can travel toward Earth to disrupt human technologies in space. To better understand the forces at work, a team of researchers used NASA data to study a precursor of CMEs called coronal cavities. Credit: NASA/Solar Dynamics Observatory (SDO)

Kucera and her colleagues have published a paper in the Sept. 20, 2012, issue of The Astrophysical Journal on the temperatures of the coronal . This is the third in a series of papers—the first discussed cavity geometry and the second its density—collating and analyzing as much data as possible from a cavity that appeared over the upper left horizon of the sun on Aug. 9, 2007 (below). By understanding these three aspects of the cavities, that is the shape, density and temperature, scientists can better understand the space weather that can disrupt technologies near Earth.

The sun's atmosphere dances. Giant columns of solar material – made of gas so hot that many of the electrons have been scorched off the atoms, turning it into a form of magnetized matter we call plasma – leap off the sun's surface, jumping and twisting. Sometimes these prominences of solar material, shoot off, escaping completely into space, other times they fall back down under their own weight.

The prominences are sometimes also the inner structure of a larger formation, appearing from the side almost as the inside a large light bulb. The bright structure around and above that light bulb is called a streamer, and the inside "empty" area is called a coronal prominence cavity.

Such structures are but one of many that the roiling magnetic fields and million-degree plasma create in the sun's atmosphere, the corona, but they are an important one as they can be the starting point of what's called a , or CME. CMEs are billion-ton clouds of material from the sun's atmosphere that erupt out into the solar system and can interfere with satellites and near Earth when they head our way.

"We don't really know what gets these CMEs going," says Terry Kucera, a solar scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "So we want to understand their structure before they even erupt, because then we might have a better clue about why it's erupting and perhaps even get some advance warning on when they will erupt."

Kucera and her colleagues have published a paper in the Sept. 20, 2012, issue of The on the temperatures of the coronal cavities. This is the third in a series of papers—the first discussed cavity geometry and the second its density—collating and analyzing as much data as possible from a cavity that appeared over the upper left horizon of the sun on Aug. 9, 2007 (below). By understanding these three aspects of the cavities, that is the shape, density and temperature, scientists can better understand the space weather that can disrupt technologies near Earth.

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User comments : 4

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Skepticus
1 / 5 (1) Sep 20, 2012
The sun's atmosphere dances. Giant columns of solar material – made of gas so hot that many of the electrons have been scorched off the atoms, turning it into a form of magnetized matter we call plasma


Nice poetry, lousy physics 101. Matter that has electrons stripped off (or added) are ionized (such as plasma), not magnetized. Stationary ions don't get attracted or repulsed by magnetic fields. Only when they are moving in a mag field that their path can change from original heading.

cantdrive85
1 / 5 (6) Sep 20, 2012
"The sun's atmosphere dances. Giant columns of solar material – made of gas so hot that many of the electrons have been scorched off the atoms, turning it into a form of magnetized matter we call plasma – leap off the sun's surface, jumping and twisting. Sometimes these prominences of solar material, shoot off, escaping completely into space, other times they fall back down under their own weight."

First of all, it's just plasma, and likely was never a gas, the Sun is 100% plasma and there is no instance where a gas can exist in such an environment. Secondly, the plasma doesn't "fall back under it's own weight", plasma is dictated by EM forces, the effects of gravity (implied by mentioning weight) are negligible. The electrical nature of our star also explains the solar wind.

"The prominences are sometimes also the inner structure of a larger formation, appearing from the side almost as the filament inside a large light bulb."

That's EXACTLY what it is, an electric discharge!
cantdrive85
1.3 / 5 (7) Sep 20, 2012
The sun's atmosphere dances. Giant columns of solar material – made of gas so hot that many of the electrons have been scorched off the atoms, turning it into a form of magnetized matter we call plasma


Nice poetry, lousy physics 101. Matter that has electrons stripped off (or added) are ionized (such as plasma), not magnetized. Stationary ions don't get attracted or repulsed by magnetic fields. Only when they are moving in a mag field that their path can change from original heading.



It is magnetized, you can think of each little plasma particle as being a magnet, this is the nature of electrified plasma and it is this magnetic connection from particle to particle (all of space is plasma) that explains the galactic rotation (without dork matter)we observe. We live in an 'Plasma Universe' directed by the electric force, as they say, "May the force be with you".
HannesAlfven
1.7 / 5 (6) Sep 21, 2012
I'm not completely understanding the mystery here. Can somebody help me?

There is a filament of plasma. We know that plasma filaments cannot exist without a double layer. So, something is breaking through the double layer, right?

From Alfven's Cosmic Plasma:

"[I]t is well-known from decades of plasma investigation in the laboratory that certain types of electric double layers may become unstable in the sense that they suddenly disrupt the current. The result is that the energy W-sub-L may be released in the double layer, and this causes an explosion. However, there may also be other plasma instabilities which cause a disruption of current, and hence an
explosion ...

There are good reasons to suppose that many of the explosive events observed in cosmic physics are produced by exploding double layers ... Examples are magnetic substorms, solar flares, and similar phenomena in `flare stars' ..."

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