Table of Contents
Yohkoh SXT: Introduction
The Yohkoh Science Nuggets
Notes from the Yohkoh Soft X-Ray Telescope
These weekly science notes
are intended to give an unspecialized but scientifically fluent view of
ongoing X-ray observations of the Sun from the Soft X-Ray Telescope (SXT)
aboard the orbiting Yohkoh
satellite. A nugget is a lump, esp. of native gold or other precious metal.
These weekly science notes are nuggets, in the sense that they may have
a rough exterior, but they have a precious substance beneath the surface.
Sometimes the authors of
these nuggets -- the scientists who operate SXT -- get carried away with
technical jargon. When that happens, use the glossary
and/or the list of acronyms.
Weekly Nuggets came into being
in 1997, when it became obvious that a huge wealth of information was contained
in the Yohkoh data base, and a continuing record of the highlights was
needed. During this year it became clear that we had passed the minimum
of the 11-year sunspot cycle sometime in 1996. The rise to solar
maximum was underway!
The Nuggets in this year cover
a diverse range of topics -- including flares and solar active regions
(whose understanding is an important goal of Yohkoh), but also other phenomena
related to the solar cycle, the effect of the Sun on Earth, and the "two
steps forward, one step back" beginnings of the lurching return to a higher
level of solar activity.
In this year, close collaboration
with the ESA/NASA Solar and Heliospheric Observatory (SOHO) focussed attention
on so-called halo coronal mass ejections (CMEs) as solar eruptions headed
toward Earth. The solar activity level lagged behind expectations -- would
it catch up? Would the peak really come in Y2K, as expected? Stay
Almost five years ago scientists
predicted that the
the maximum of solar cycle 23 will occur this year.
As the year unfolds we will
doubtless see many flares and coronal mass ejections,
but we will have to wait until the end to see whether their
will be accurate.
A big event was to have been the launch of NASA's
solar flare mission, but a
shakeup delayed it until 2001.
By any definition, it's the beginning of the millennium.
Have we hit solar max yet? It's impossible to tell, until we're many
months past it.
official prediction from the Space Environment Center
at NOAA shows that we can't yet really be sure
whether it's already happened or will happen during this year.
We can only repeat our previous bit of advice -- stay tuned.
Weekly Science Notes from
the Yohkoh SXT are not appropriate for citation in scientific publications