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.
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.
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
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
February 18, 2000
H. Hudson (firstname.lastname@example.org)
D. McKenzie (email@example.com)