Weekly Notes from the Yohkoh Soft X-Ray Telescope
(Week 8, 2000)
Instrument Status
See the weekly operations report for
details.

In the display above (click to enlarge), the colored lines show the
times of SXT images that currently are on-line at ISAS. The purple lines
are flare mode. The gaps will be considerably reduced when the NASA telemetry
arrives and gets reformatted.
For a summary index listing of the weekly science reports,
click
here. Generally, these notes contain current research, or ideas related
to current research in solar physics, as revealed by Yohkoh. They
are done in "real time" and so they may contain (a) jargon, (b) blunders,
or (c) trivialities. Of course they are not screened by referees! We are
always happy when somebody writes a paper stimulated by one of these nuggets,
and it happens frequently. The SXT Chief Observers (most of the authors)
do not have any proprietary rights to the data or ideas presented.
Theories, models, and cartoons
This week's science nugget is again something lightweight; we
put too much time into the analysis of the
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.
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.
Only a single example (Ed Cliver's) here:
and 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.
Try AltaVista's Translation Service at http://babelfish.altavista.
digital.com. But, beware of barbarisms!
February 11, 2000
D. McKenzie (mckenzie@isass0.solar.isas.ac.jp)
H. Hudson (hudson@isass0.solar.isas.ac.jp)