Theories, Models, and Cartoons

Science Nugget: February 18, 2000

This week's science nugget is again something lightweight; last week we put too much time into the analysis of the first X-class flare of the millennium. Today we simply comment on the question of how we interpret what we are doing: theories, models, and cartoons. The subject of these abstractions is "flares and CMEs" in this case, since they represent a lot of what Yohkoh does.

  • Theories. A real theory has some predictive power. In our domain, the dominant theoretical genre is MHD, which has certain weaknesses - among them, an inherent inability to handle non-thermal particles self-consistently, at least in the usual framework. MHD theories therefore cannot predict important parts of flare physics.
  • Models. By this we mean numerical exploration of simplified theories. Even the MHD framework is too complicated to develop very fully in an analytic sense, although smart people continue to learn more and more this way. The numerical simulations allow one to do experiments on (in principle) realistic physical situations. A glance at the program of this month's international meeting on magnetic reconnection illustrates the point. The papers whose titles are blinking, on his page, depend upon numerical techniques. Most do!
  • Cartoons. A freehand sketch is often the medium of significant exchange of ideas. One great difficulty in the more sophisticated approaches above is that they can almost never embrace the huge dynamic range of the physical parameters that we see varying. How to relate one kind of observation to another? A cartoon! Accordingly we have begun to put together a Grand Archive of Solar Cartoons, not entirely tongue-in-cheek, to show how serious we all are about this sort of thing. This archive has a randomizer, borrowed from David McCoy, so that each time you link to it you get a different cartoon. Here's one, due to Melrose and showing an unorthodox approach to understanding how coronal flux tubes might interact:

    Here we will call it quits for this week's nugget. But please visit the archive, which we hope to add to continuously, and admire the vigor with which people have been doing this over the decades.

    February 18, 2000 H. Hudson (
    D. McKenzie (