Yohkoh SXT Movies

New (1996 February 25): SXT movies of an active region coronal mass ejection

Hugh Hudson of the University of Hawaii has kindly given us the Yohkoh Soft X-ray Telescope (SXT) images which we translated into flattened QuickTime (972 Kbyte) and MPEG (654 Kbyte) versions.

Hugh's description of the events in the movie: 

We see several things in this movie. First, it's been reoriented so that
solar East is at the top, so that up looks like up. The Sun rotates,
bringing an active region onto the visible hemisphere. It is very active,
showing many things including an extremely large jet - probably unrelated
to the major event later - at about 18:39 UT.

The main event consists of the buildup of brightness above the ultimate
flare site, culminating in the frame at 20:34 UT. Then in subsequent frames,
this part of the corona disappears. If you look closely you can see a twisted
network of loops moving outwards. We associate this tentatively with a
huge flux rope, as expected from the interplanetary observations of
related events. The disappearance causes the pronounced dimming of the
corona above the flare site. The flare itself is a long-duration event
with full development of post-flare X-ray loops and a fearsome-looking
nest of spikes pointing outwards in the aftermath of the eruption.

Dave Webb (AFGL) first noted the "dimming signature" in this event.

Yohkoh and SXT

The earth-orbiting Yohkoh ("Sunbeam") satellite of the Institute of Space and Astronautical Science (ISAS), Japan, is able to observe the Sun in wavelengths inaccessible from the surface of the earth. Every day, the Yohkoh Science Team releases, through the Hiraiso Solar Terrestrial Research Center of the Communications Research Laboratory (Japan), a single, full field-of-view, soft X-ray image of the Sun obtained by the Soft X-Ray Telescope (cf. Tsuneta et al. 1991, Solar Physics, 136, 37) in the "dagwood" (Al-Mg-Mn) filter, which is most sensitive to plasmas at temperatures ~ 2,000,000 K. (These images, downloaded from Hiraiso, are available from the SDAC in FITS format via anonymous ftp.) The Soft X-ray Telescope (SXT) was prepared by the Lockheed Palo Alto Research Laboratory, the National Astronomical Observatory of Japan, and the University of Tokyo with the support of NASA and ISAS. The Project Manager for Yohkoh is Prof. Yoshiaki Ogawara of ISAS, and the Project Scientist is Prof. Yutaka Uchida of the Department of Astronomy, University of Tokyo.

The Movies

Using the Interactive Data Language (IDL) from Research Systems, Inc., we first write PICT format files of each image. Then, using Adobe Premiere 4.0 on an Apple PowerMacintosh 8100/80, we create a QuickTime movie from the PICTs. In this process, the original images, mostly 512 x 512 pixels (a few at 256 x 256), are reduced to 256 x 256 to prevent the movie file from being even more enormous than it already is. (The 1994 January - May movie is reduced to 128 x 128 pixels so that those without the large bandwidth necessary to download the other movies can still see what the Sun looks like in soft X-rays over a period of months.)

The 1993/1994 movie is composed at 10 frames per second, a time compression factor of nearly 870,000. We use the Apple Video CODEC (image compression scheme), and a quality of "high" to compress the QuickTime movies. The other movies were originally produced with the shareware program "MovieMaker," and run at different frame rates.

The movie files are accessible in "flat" format, so that they can be read by QuickTime for Windows or XAnim on X windows systems, as well as on Macintoshes with QuickTime.

All the movies are silent.

Rights use notice for the Yohkoh SXT movies.

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Last revised 9 January, 1995 - J.B. Gurman