ar053.shibata08
Posted: 04-Oct-93
Updated: 24-Mar-94, 05-Dec-94, 22-Aug-95
Events specified: recurrent surges in NOAA 6950 on October 7, 1991
PI and Collaborators: Shibata K., Schmieder B. , van Driel-Gesztelyi L. and who is interested in this work
Motivation: The association between H$\alpha$ surges and X-ray bright points
or jets is still contraversial (Shibata \etal 1992, PASJ 44, L173;
Schmieder \etal 1994, ApJ.).
Theoretically X-ray jet could be associated to chromospheric
ejections. Nevertheless if the reconnection point is high in the
corona it is not easy to get cool chromospheric ejections by
simple reconnection. One possibility to get cool jets is magnetic
twist mechanism as discussed by Shibata and Uchida (1986,
Solar Phys, 103, 299).
If the reconnection
occurs in the transition region , both hot and
cold plasmas are ejected according to numerical simulation
(Shibata, Nozawa, Matsumoto, Publ. Astr. Soc. Japan, 44, 265).
If the reconnection occurs in lower chromosphere, we could get
only cool jet, though we need new simulations to confirm this
point .
We would like to analyse H-alpha and SXT data of a recurrent surge
observed close to the western limb in order to find clues for the
mechanism of chromospheric ejections. The other existing surge
model, namely the pressure gradient driven model has to be ruled
out in favour of the magnetic reconnection-driven model if no
heating is observed connected to chromospheric ejections.
Data and Method to be Used:
The observations concern a recurrent surge (AR 6950 - S14 W 90)
observed on Oct 7, 1991 one event occuring between 10:20 and 10:39
UT and another between 11:51 to 12:15 UT. Yohkoh points this AR
from 10:24 UT until the end of the second event.
Coordinated observations between Yohkoh SXT and the Multichannel
Subtractive Double Pass Spectrograph (MSDP) operating in Meudon
Solar Tower have allowed to follow the X-ray signature of a
recurrent surge. This surge has a special interest because of its
position close to the limb. An altitude as high as 60 000km is
reached in 7 minutes with velocities on the disk around 150 km/s
and redshifts of 30 km/s. Its footpoint is mainly tied in a
loop-shaped plage region.
No X-ray jet was observed by the SXT (with Al1 and AlMg filters)
Rapid re-structuralization of a complex low-lying loop system is
detected. A microflare occurred at the footpoint of one of these
loops which would correspond to the base of the surge.
complementary observations:
Please close this proposal because the paper on this subject has already been published in Solar Phys.;
Schmieder, B., Shibata, K., van Driel-Gesztelyi, L., and Freeland, S. Solar Phys. 156 , 245-264 (1995) H$\alpha$ Surges and Associated Soft X-ray Loops
Update 05-Dec-94 (temporary update)
This subject has been summarized by Schmieder, Shibata, van Driel, and Freeland, and the paper has been submitted to Solar Physics. It was accepted, and will appear soon in this (or next) year.
The detailed information (abstract, volume, page, etc.) will be sent to tbb later.
Update 24-Mar-94
Following is the abstract of a paper to be presented at COSPAR, July 1994 (Symposium E2.2).
CHROMOSPHERIC EJECTIONS AND THEIR SIGNATURES IN X-RAY OBSERVED BY YOHKOH
B. Schmieder and N Mein (Observatoire de Paris, Section de Meudon, URA 326, 92195 Meudon Cedex Principal, France)
S. Freeland (Lockheed Palo Alto Research Laboratory, Palo Alto, CA 94304, USA)
K. Shibata (National Astronomical Observatory, Mitaka, Tokyo 181, Japan)
L. van Driel-Gesztelyi (Kiso Observatory, University of Tokyo, Mitake-mura, Kiso, Nagano 397-01, Japan
H.Kurokawa (Kwasan and Hida Observatories, Kyoto University, Kamitakara, Gifu 506-13, Japan)
Surge or ejection of chomospheric material is commonly observed in active regions with its base tied along the inversion line of this isolated magnetic island, called parasitic polarity (as seen in magnetograms from Huairou, MSFC, Hawai, Okayama). Using observations obtained during coordinated campaigns between the Yohkoh satellite and the Multichannel Subtractive Double Pass Instruments operating at Meudon and on the Canary Islands we are able to observe surge events (Oct 7 1991, May 1 1993) and look for their signatures in soft X-rays. In the partial frame images of Yohkoh SXT low X-ray loops overlaying the active region where the surge occurs are seen continuously restructuring. No X-ray emission is detected along the path of the surges and no X-ray jets are observed. X-ray bright points appear at the basis of the surge 5 minutes before the ejections, which have been interpreted as being due to magnetic reconnection. Cold plasma bubbles squeezed between magnetic field lines could correspond to surge material.