Frequently, in a variety of experiments
though we miss what we expected to find,
yet something valuable turns out,
something surprising, and instructing,
though unthought of.
--Benjamin Franklin

David E. McKenzie  
Montana State University   
Solar Physics   

Research Topics

 

Flows Near Solar Flares

Since solar flares are the largest explosions in the solar system, it isn't surprising that they're often associated with high-velocity flows. Blobs of ejecta are frequently observed flying outwards from flares at speeds of several hundred kilometers per second. In 1999, however, we discovered the unexpected phenomenon of flows into the flare sites. Using the Soft X-ray Telescope on the Yohkoh solar observatory satellite, we detected features moving downward into the tops of post-eruption arcade at speeds of a few hundred kilometers per second. (See the publication by McKenzie & Hudson, 1999; and also the press release.)

A list of flares where these Supra-Arcade Downflows have been observed is here.

We now believe that these flows represent the retraction of magnetic flux tubes, shrinking to relax magnetic tension after reconnection. I'm working with Prof. Dana Longcope and graduate student Sabrina Savage to make quantitative measurements of Supra-Arcade Downflows, to determine the observational characteristics of magnetic reconnection in flares.

Spiky Arcades

Some of my current research is focused on the magnetic arcades (i.e., "rows of arches") which are often observed in the corona following the eruption of a prominence/filament. In addition to being quite beautiful, their structures and the characteristics of their evolutions tell us about the conditions of their environments, the magnetic fields that define them, and the reconnection processes which create them.

An interesting subset of the flare arcades are the "spiky" arcades, so called because of the tall, bright rays which extend upward from their tops. In this this movie (large: 5.5 MByte), you can see one of these events, in which a fan of bright rays is formed on top of the post-eruption arcade. (If you don't have the time to download the full movie, try this still image of a spiky post-eruption arcade.) Now ask yourself: How do these exceedingly long, nearly linear structures of 10-million-degree plasma come to be?

Quantifying Magnetic Reconnection

In solar physics, we are now fairly convinced that magnetic fields are rearranged, and magnetic energy is released, via a set of processes which we refer to as magnetic reconnection. However, we're lacking some specifics: How fast does reconnection occur? How much flux is included in a given reconnection event? What triggers an event? By combining observational measurements with analytical estimates and computer modeling, we (Prof. Dana Longcope, Dr. Mark Linton (of Naval Research Lab, and myself) hope to continue finding answers to some of these questions.

Current Solar Activity

A handful of links for checking on current solar activity. Each of these will open in a new browser window, since they are outside of the MSU site.



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