Rice researcher part of team that used Doppler shifts to ID phenomenon; may help predict space weather
Left, image of hot (1.8-million degree Fahrenheit) active region loops. Right, flows of solar plasma (blue shifts). Credit: Left: SDO/AIA (NASA); right: Hinode/EIS (JAXA, NASA, ESA and STFC)
A Rice University astrophysicist is part of an international team that combined Doppler techniques with images and data from a space-based telescope to observe, for the first time, loops of 1,800,000-degree Fahrenheit plasma flowing up from the sun’s surface at more than 12 miles per second.
The loops, rooted in active regions near sunspots and guided by the sun’s magnetic field, arch over the sun and may be the first signs of trouble spots, where plasma undergoes “impulsive heating,” according to the researchers. They expect their findings will help scientists understand the genesis of solar flares and coronal mass ejections – solar storms – that threaten satellites orbiting Earth and power transmission grids on the ground.
Rice’s Stephen Bradshaw and colleagues in India and the United Kingdom reported their results today in the Astrophysical Journal Letters.
They wrote that Doppler measurements drawn from images taken by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard the Hinode solar satellite show the first observation of a “warm loop” in which plasma rises from the surface of the sun rather than sinks back into it.
In visible-light Doppler, objects moving away from the viewer are shifted red, while objects moving closer shift blue. That fact has long been useful to astrophysicists judging how fast other stars and even galaxies are moving in an expanding universe. But in previous observations of active regions on the sun, warm loops like the one observed by Bradshaw and his colleagues have only been seen to shift red and, therefore, the plasma was thought to be sinking.
The prevalence of red shifts led to the belief that heating is taking place high in the sun’s atmosphere and leading to the evaporation of material from near the surface into the atmosphere that then flows back down as it cools. That may be true, Bradshaw said, but it leaves some important questions unanswered: What causes the heating? Where is the evidence for plasma rising from the surface into the atmosphere?
The new observations will help to answer these questions, he said.
“The blue shifts are the signature, or ‘smoking gun,’ of plasma flowing up into the atmosphere,” said Bradshaw, Rice’s William V. Vietti Junior Chair of Space Physics and an assistant professor of physics and astronomy. “They show that the fastest up-flows are found near the surface of the sun. This information gives us clues to the location where the heating is taking place, how fast it is and how much energy is needed.”
“The sun governs the environment in which we live, and it is the so-called solar active regions that drive extreme conditions leading to the explosive flares and the huge eruptions; understanding these active regions is absolutely critical for the study of what we now call space weather,” said Richard Harrison, head of space physics and chief scientist at the Rutherford Appleton Laboratory in the United Kingdom. “The work published in this paper is a key element of that work, applying innovative analyses to the observations from the U.K.-led Hinode/EIS instrument.”
Bradshaw noted the sun is fast approaching the part of its 11-year cycle when flares and coronal mass ejections occur most frequently. “These events present the most danger to satellites, power grids and even to airliners on flight paths in polar regions,” Bradshaw said. “This period is called solar maximum, and we will become ever more reliant on this technology during every subsequent solar cycle.
“One of the aims of solar research is to develop a space-weather forecasting capability, whereby solar storms can be predicted by detecting their signatures before they occur at the sun,” he said. “This is much like monitoring depressions as precursors to tropical storms and hurricanes, but space-weather forecasters will monitor active regions. Accurate forecasts of solar storms will give us the maximum possible time to prepare for their arrival at Earth and to mitigate their effects.
“Our work will contribute to this aim by leading to a better understanding of the physics of active regions.”
Co-authors are principal investigator Durgesh Tripathi ofthe Inter-University Centre for Astronomy and Astrophysics in Ganeshkhind, India; and Helen Mason, assistant director of research, and Giulio Del Zanna, an advanced fellow in the atomic astrophysics group, both in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge.
The Hinode satellite was launched in 2006 by the of Space and Astronautical Science and the Japan Aerospace Exploration Agency, in collaboration with the National Astronomical Observatory of Japan, NASA and the and Technology Facilities Council the United Kingdom. The European Space Agency and Norwegian Space Centre also supported the research.
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Read the abstract at http://iopscience.iop.org/2041-8205/754/1/L4
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I quite like the battle my self as i’m not well up on accepted solar physics nor Vuk’s detours and have enjoyed a free education on the former since 2008 from Leif on a regular basis. But Vuk’s smacked down ideas keep going back to the corner and then coming limping back to life for another round. This is Vuk’s peer review process here and he hasn’t made it. Vuk needs to stop recycling as it’s tedious as it’s the same ol’ same ol’. One prior adherent to the Electric Universe idea received a life time ban for tedious repetition of the idea. There are forums for this such as tallbloke’s but Leif is a incredible resource for this site and keeps the Solar issues, which are fascinating to us vunerable lay people, on the straight and accepted narrow.
I quite like the battle my self as i’m not well up on accepted solar physics nor Vuk’s detours and I have enjoyed a free education on the former since 2008 from Leif on a regular basis. But Vuk’s smacked down ideas keep going back to the corner and then coming limping back to life for another round. This is Vuk’s peer review process here and he hasn’t made it. Vuk needs to stop recycling as it’s tedious as it’s the same ol’ same ol’. One prior adherent to the Electric Universe idea received a life time ban for tedious repetition of his pet theory. There are forums for this such as tallbloke’s but Leif is a incredible resource for this site here and keeps the Solar issues, which are fascinating, on the straight and accepted narrow. We should have a ‘electric universe’ thread with the idea that the electric universe idea be limited to that thread but be banned from solar threads.
I’m putting my head above the parapet fully expecting to get well and truly smacked down.
Didn’t someone before Einstein was even born come up with e=mc^2 using purely Newtonian physics? I think his name was Weiss or something similar.
I just seem to recall seeing it in a mid 1920s copy of the British Pharmacopoeia.
DaveE.
What doesn’t seem reasonable to me is that the sun’s core be hydrogen. Where did the heavier elements go? It seems unavoidable that there must be a core of heavier elements, similar to what we see in the planets with high core temperatures. I’m not trying to say the sun is made of iron. Only that there must be a core of heavier elements.
ferdberple says:
July 9, 2012 at 8:50 am
What doesn’t seem reasonable to me is that the sun’s core be hydrogen. Where did the heavier elements go?
The core is hydrogen mixed with helium. Some of the helium is primordial and was generated during the Big Bang and the rest is generated by nuclear fusion of hydrogen. There is a small admixture of heavier elements [of the order of 1%], but one could hardly call that a ‘core of heavier elements’.
According to NASA the sun is 71% hydrogen and 27% helium by mass in the visible region.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961112a.html
Given the large amount of helium present by mass, it seems almost certain that the core is mostly helium. In that case the hydrogen fusion must be primarily located outside the core. In which case the solar spectrum would be a fairly poor indication of the composition of the core.
ferdberple says:
July 9, 2012 at 6:12 pm
Given the large amount of helium present by mass, it seems almost certain that the core is mostly helium. In that case the hydrogen fusion must be primarily located outside the core.
No, as long as there is enough hydrogen for the fusion it will stay where it is. In the core, the abundance of helium by number is 10% that of hydrogen, so 90% if the nuclei are still hydrogen. The fusion process also needs the high temperature that there is in the core. In the convection zone the helium abundance by number is about 8%
In which case the solar spectrum would be a fairly poor indication of the composition of the core.
It is almost impossible to detect helium in the solar visible spectrum as the temperatures are too low for helium to be excited. The exception is during very strong solar flares, when one finds about 8% He by number in the photosphere. In the chromosphere, corona, and solar wind we can readily see the helium. It is there about 5% by number [with a solar cycle variation], reflecting the fact that it is harder to lift the heavier nuclei out against gravity.
In the core, the abundance of helium by number is 10% that of hydrogen
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Water molecules make up something like 99% of the molecules in the human body by number, but only 70% by mass. Doesn’t counting the number of molecules understate the significance of mass in determining the characteristics of an object?
Given the large percentage of helium by mass, I would expect gravitational enrichment of the core to be higher than 10/8. How was this measured?
In the absence of significant convection at the core, the fusion waste products should collect at the core, inhibiting fusion in that area. Under that situation the most active fusion should be outside the core.
Thus, the notion that the convection zone is relatively shallow seems reasonable if the core is not the primary source of fusion. Rather that the most active fusion area is a sphere surrounding the core, with the convection zone above that.
ferdberple says:
July 10, 2012 at 6:56 am
Doesn’t counting the number of molecules understate the significance of mass in determining the characteristics of an object?
no, not when it comes to judging if fusion is still taking place. 90% of the particles in the core is hydrogen. If you assume that 1% is Uranium, that would cut the hydrogen content measured by mass in half, but hardly make a dent in the fusion rate which still is controlled by the remaining 89% hydrogen.
Given the large percentage of helium by mass, I would expect gravitational enrichment of the core to be higher than 10/8. How was this measured?
The observed luminosity has to match what is produced in the core. It does that best with the 10/8 ratio. Also, considering the amount of helium produced in the last 4.6 billion years leads to the same result.
In the absence of significant convection at the core, the fusion waste products should collect at the core, inhibiting fusion in that area. Under that situation the most active fusion should be outside the core.
They do collect in the core, but there is enough hydrogen left [90%] that fusion is not inhibited. Also, the speed of the thermal random motions is very high [620 km/s] so helps in mixing the material.
Thus, the notion that the convection zone is relatively shallow seems reasonable if the core is not the primary source of fusion. Rather that the most active fusion area is a sphere surrounding the core, with the convection zone above that.
much as you would like so, it just ain’t so. The fusion rate depends on the amount of hydrogen [still high, 90%] and the temperature [very steep dependence, something like temperature to the 4th power if memory serves] which is only high enough in the core.