Expert: Philip Stahl - 12/15/2006

Question
I thought that solar flares are on an 11yr cycle- are physicist trying to predict how large / how many solar flares will happen in this cycle? Also, from the study of magneto-hydrodynamics would you learn about the workings of the sun/ stars as well?

Thanks once again!!
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The text above is a follow-up to ...

-----Question-----
How does physics and solar flares mix? In other words why do you need physics to study solar flares?

Thanks for answering my question :)
-----Answer-----
Hello,

We need physics to study and analyze solar flares because the flare itself is a complex physical event that spans a range of temperature scales, energies and also involves thermal, electro-magnetic and optical aspects. All of which directly relate to physics.

For example, Maxwell's equations for the electric and magnetic fields are directly interwoven in the study of flare plasma. The way this plasma behaves under its particular conditions of temperature and pressure also introduced a whole new area we call "magneto-hydrodynamics" - the behavior of fluids, fluid dynamics under powerful magnetic -electric influence.

The basic thrust of *plasma physics* (you can google for much more detail, but essentially plasma is a 4th state of matter) is the marriage of electro-magnetic theory, thermal and particle physics. Indeed, many of the plasma instabilities are wave-related and these have their origin in Maxwell’s theory of electro-magnetism. Thus, a logical place to start for the study of solar flare behavior - which cannot be duplicated in any earthly lab.

Suffice it to say, without the essential physics as our guide, there is very little we'd understand about solar flares. In addition, the sheer complexity of plasma physics is in large measure why we do not as yet have firm solar flare predictions. (The other aspect of course is optical, we do not yet have the optical apparatus at the required level of optical resolution to disclose the initial unstable volume in solar coronal loops, arches. The budget for the Solar Optical Telescope - which would have done this - was gutted in 1984)

We need to understand much more about the underlying plasma physics, especially in extreme conditions. More and better optically -refined instruments would be one way to do this - along with advances in our plasma analyses - especially the multiple plasma wave instabilities.  

Answer
Hello,

Actually it is *sunspots* that display a mean, 11-year cycle - not solar flares. Some of the largest solar flares have occurred outside the peak of the sunspot cycle, e.g. the Aug. 1972 major x-ray flares.

Physicists who study the sub-branch of solar physics known as "space weather" do try to predict the frequency of major flares, especially those than can affect the Earth's ionosphere (that part of the atmosphere for which electrical propagation is easiest).

This also entails trying to predict how large in area a flare will be, though this is often less crucial than the energy output that directly affects the ionosphere. In my own research, the aim was to directly predict solar flares that caused "sudden ionospheric disturbances" - or massive disruption of communications, radio -Tv broadcasts - as well as aircraft navigation systems.

Finally, yes - magneto-hydrodynamics is useful for application to other solar like stars as well. Thus, the more we understand the MHD regime in the Sun, and the detailed plasma physics - the better we can apply it to the distant stars. That includes the prediction of "stellar flares".

You can learn more about a recent example of a mammoth stellar flare at this link:

http://www.nasa.gov/mission_pages/swift/bursts/monster_flare.html