Report from ISAS

		         15 - 21 August 1994
			   Nariaki Nitta
			

SUMMARY 

A flare-productive region AR 7765 was observed all through the week.


OPERATIONS

Both the satellite and SXT operations went smoothly, thanks largely to
the skillful tohban Kyo Akita (Osaka Gakuin University), who reportedly
has already signed return engagements.


SOLAR ACTIVITY

One active region (AR 7765) dominated the solar X-ray flux.  It produced
6 M-class flares.  Only one of them is known to have taken place during
Yohkoh night.  Only two of them belonged to the visible orbits and
their data have been reformatted.  Hugh Hudson looked at the SXT images 
of the M3.9 flare (14 August 1994 17:35 UT) in detail and Nariaki Nitta 
synthesized HXT images of the flare in all the channels.  This region 
apparently became stabilized as it approached the western limb. 


PERSONNEL

No change in the US SXT operations team.  Bob Bentley arrived from MSSL
for a four-week stay.


SCIENCE

Hudson and Nitta continued to work with Mukul Kundu, visiting professor
at ISAS, on the relationship between X-ray jets/flares and meter-wave 
bursts.  Kundu and Nitta managed to coalign SXT/HXT images with the
Nobeyama Radio Heliograph images for two flares.  The latter data show
wobble of non-disk features with respect to the disk, reflecting the
way calibrations are done.  Fortunately, there were several active regions
distibuted over the Sun, providing common features in free-free emission.
Hudson worked with Akita to look into the 5 October 1992 behind-the-limb
flare.  The hard X-ray loop-top source is enhanced because the footpoints
are probably occulted.  This flare quite clearly shows an outward motion
of plasmoid in the impulsive phase, as is common in this type of flares.
 

ISAS WORKSTATIONS

No more report, except that some disks (magnetic and magneto-optical) of 
the flareN workstations were accidentally unmounted from time to time and 
that we did not know who to ask for re-mounting.


SEMINAR

More than a dozen people have given us the titles for the extended Yohkoh
seminar (= the first neighborhood meeting) that is planned on 24 August.