SXT Status Report
                    16 July 1996 - 29 July 1996
                         (Weeks 29 - 30)

                        H. Hudson, S. Savy 


INTRODUCTION

Solar activity displayed an extremely interesting pattern during these
two weeks, but there were some operations difficulties (including an
assault on KSC by Typhoon #6 of the season). 

SOLAR ACTIVITY

Solar activity dropped precipitously just prior to the reporting
period with the disappearance of AR 7978. This old-cycle region 
developed sunspots with area more than 400 millionths, and a delta
configuration. It disappeared suddenly at the W limb, implying a
low-lying soft X-ray structure. It also reappeared suddenly on 25-July
(as AR 1981) at about the same level (but thus far without the flares).
This is a good opportunity to study an isolated major active region.
Reportedly SOHO (LASCO) detected a major CME on about 21-July, which we
will no doubt hear further about - this must have come from the active
region when it was almost diametrically on the invisible hemisphere of
the Sun!

SXT INSTRUMENT STATUS

This was not a good reporting interval for operations. The typhoon
previously mentioned caused a one-day interruption of Yohkoh operation
because the OP command file could not be uploaded (nor data downloaded)
while KSC suffered from a power outage. During this interval too
there was a link problem that stopped the near-real-time data flow
for several days, including the daily image distribution.  Finally
there was an operations mistake (a missed command) that resulted in
two more days of lost data over the weekend (28-Jul), and then an
SEU that caused an additional delay for recovery.

Everything is working fine now, though.

In a major development, we have learned that Katano_san, a familiar
figure to any visitor to ISAS who has done duty as a tohban, is 
going to move to a different assignment. A new person from NEC will
replace her. This transition will take place slowly, we hope, and 
a farewell party of some sort will probably happpen about the time
of Yohkoh's 5th birthday.

SXT CALIBRATION ACTIVITIES

Normal terminator image accumulation has continued, with emphasis on
the 5' E offpoint used for this month's coronal imaging. This is also
a candidate for obtaining wide-FOV images during next month's SOHO
campaign based on JOP045.

CAMPAIGNS

Support observations for VLA observing on 27 July were scheduled,
but had to be abandoned because of the increased activity. As mentioned,
we are going to do extensive offpoint/deep exposure imaging in 
support of JOP045 insofar as we can.

For Yohkoh operations, there is a text file accessible
with "finger campaign@isass0.solar.isas.ac.jp | more" or the Web at
"http://www.space.lockheed.com/SXT/homepage.html". See
"http://sohowww.nascom.nasa.gov/operations/targets/today" for SoHO
target planning.

VISITORS

Scientific visitors to ISAS during this period included Wang
Jingxiu from Beijing, B. Somov from Moscow, and M. Kundu from the
University of Maryland.

SCIENCE

The main science news was reported above, namely the hot active region 
that had made an X-flare on 9-July. As a GOES one-month plot shows, and the
SXT images display beautifully, this has resulted in an extremely lopsided
Sun. The activity from the region has in one rotation spread throughout
one hemisphere (the eastern hemisphere right now). A couple of questions - 
how does the "diffusion" of field in the photosphere, as in Leighton
models, work this rapidly? And, if the Sun can show an X-ray swing of
four decades in one month, how come other stellar X-ray sources do not
do this? Stay tuned to these pages for answers to these and other 
perplexing questions.

SEMINARS

July 18:
D. Alexander (U Montana/LMPARL) "Soft X-ray Loop-top Sources:
  Physics or Fiction?"
H. Hudson (SPRC/ISAS) "Litvinenko's theory of log-N/log-S"

July 25:
T. Yoshida (IOAUT): "There is no steady SXT loop with length 
less than 10^9.5 cm"
T. Yoshida (IOAUT): "Cool steady structures and hot transient 
structures in active regions"
M. Kundu (U. Maryland): "Jets in Microwaves!"

The Yoshida seminars set a new record in e-mail responses to the
seminar announcement, showing that the topic is crucially important.
Kundu announced yet another nice discovery from Nobeyama and Yohkoh
data, made possible by the new Nobeyama software introduced by 
Koshiishi.

PERSONNEL

Alexander and Lemen departed for the AGU meeting in Brisbane.
Hudson returned from Bern and Savy returned from COSPAR.

Week 29 Tohbans

SSOC: T. Yoshida, S. Morita
KSC:  M. Nishio, J. Koyama 
SXT Chief Observer: J. Lemen 

Week 30 Tohbans

SSOC: Y.Nakagawa, S.Masuda 
KSC:  S.Akiyama, J.Koyama 
SXT Chief Observer: H. Hudson