fl135.hiei08 Posted: 05-Sep-93 Updated: 03-Apr-95, 17-Jan-96, 12-Oct-96 Events specified: see title
E. Hiei, D. G. Sime, A. J. Hundhausen, and M. Takahashi
We propose to make a quantitative and detailed analysis of the coronal observations made around the time of the mass ejection identified near 17:30UT on 30 April, 1993. Initial inspection of the white light data from this time indicates that this event has all the characteristics reported by us for the event inferred on 24 Jan. 1992. For that event, compelling evidence was assembled that the only significant soft X-ray emission associated with the mass ejection arose after the eruptive phase and as a result of subsequent reconnection. The weakness in the argument for the 24 Jan event was that the mass ejection was inferred, not actually observed in white light.
However, in the case of the 30 April 1993 event, the mass ejection and the eruption of the prominence contained within the pre-existing streamer cavity are observed clearly and unambiguously. We believe that the structure of the post-eruption reconnecting region reflects the kinematics observed in the ejection itself.
We seek to examine the soft X-ray and visible light observations leading up to and following the mass ejection in order to evaluate this interpretation.
Update 12-Oct-96
DIMMING EVENT ASSOCIATED WITH SUDDEN DISAPPEARANCE OF A FILAMENT
Eijiro HIEI, Meisei University, 2-1-1,Hodokubo,Hino Tokyo, 191 , Japan Art HUNDHAUSEN,HAO/NCAR, Boulder, Colorado Joan BURKEPILE,HAO/NCAR, Boulder, Colorado
A sudden disappearance of a filament was observed at around S48 E01 in a quiet region on 16 January 1993. Soft X-ray images, taken with the Yohkoh SXT instrument, and H-alpha images on four successive days of 13-16 January show that coronal loop structure ,seen in soft X-ray images above the dark filament, has been slowly swollen and drastically changed just before the disappearance of the filament. Two dimming regions appeared at the same place as the disappearance. Brightening of soft X-ray region then appeared at that place. The swollen phenomenon was observed before coronal mass ejection (Hundhausen 1993), and the 16 January 1993 event seems to be associated with a coronal mass ejectio n. The dimming,which would be due to depletion of the coronal material, is thought to be the signature of a mass ejection event seen on the disk.
Update 17-Jan-96
Evolution of coronal helmet streamer E.Hiei and A.J.Hundhausen
A coronal helmet streamer of 24 January 1992 is one of the most prominent event ever observed with a Soft X-ray Telescope on board the Yohkoh satellite and the helmet was interpreted by a reformation of a closed magnetic structure, by reconnection,after a prominence eruption and mass ejection (Hiei et al. 1993).
Fig.1 shows a development of a loop structure at the earlier phase of the coronal helmet streamer. A bright loop was seen at 09:20:18 UT, and the loop top seemed to appear higher and higher with time, on the average. However, the loop was not only one, but two or three loops were seen at a loop image after 10:33:05. The loop top was always brighter at the earlier phase. This suggests that the loop top was the first region of reacting of energy supply in its whole loop.
And then a foot became bright. The brightening of and the development of the loop at the later phase will be discussed in a later paper.
A height of the loop top at a projected plane perpendicular to the line of sight was measure and plotted in Fig. 2, which shows that each loop did shrink down with time, and another bright loop top appeared abruptly at a height above the previous one.
At the earlier phase, the development of three loops were identified. Each loop shrunk down quickly at first and slowly later; the downward velocity was at 3 km/s at first and 0.5-1 km/s at 2 hours later. However, a "jumping-up" velocity on the average was 2 km/s. The observation shows that the energy release does occur discontinuously and kept releasing for a little less than one hour.
The intensity of the loop top became maximum during shrinking; the brightness became maximun at 09:54:26; it took about 40 min. to reach its maximum from the first appearance. And then the brightness decreased with time. The 2nd loop became maximum brightness at 11:22, abot 50 min. late than its first appearance. The phenomenon itself is quite similar, but time scale is much slower than a flare event. The different time scale may be due to weak magnetic field and lower density in this high latitude event.
In the first loop, only one foot (right side in Fig. 1, which is southward) was seen, but in the second loop both feet(southern and northern) appeared. The appearance of foot also jumped to a wider distance than the previous one, like the appearance of the loop top. The time change of the 2nd loop showed that a velocity of widening of both feet was about 2 km/s.
The observation showed a shrinkage of the loop top and widening of both feet for each one loop structure and next loop jump to a higher and wider region than the previous ones.
It will be inferred from the observation that each energy release is discrete and the duration time of energy release for one loop is about 1 hour.
Update 03-Apr-95
This is a meeting report of the 3rd Japn-China Solar meeting held in Sept. 1994 at Ton-Koh, in China.
SUDDEN DISAPPERANCE OF A HIGH LATITUDE PROMINENCE, RELATED SOFT X-RAY BRIGHTENINGS, AND CORONAL MASS EJECTIONS
Eijiro HIEI, Hirohisa HARA, Masaaki TAKAHASH, A.J. HUNDHAUSEN, J.T. BURKEPILE, D.G. SIME
The disappearance of a high latitude prominence is caused by an instability in the large scale coronal magnetic structure, and is a manifestation of lifting up of solar magnetic field from the solar atmosphere towards interplanetary space.
We would like to analyze other similar events.