fl009.hudson02 Posted: 26-Jan-92 Updated: 05-Aug-92, 11-Mar-93, 06-Nov-93, 12-Aug-94, 13-May-95, 24-Feb-96, 10-Nov-96 Events specified: N/A
Collaboration: H. Hudson, Canfield, Enome, Kosugi, Nakajima, Sakao, Masuda, Tsuneta, Acton, Nitta, Klimchuk
Motivation: The Yohkoh X-ray imagers offer an opportunity to locate and characterize the high-energy particle populations responsible for meter-wave radio emissions of types I-V etc. These represent particle accelerations distinct from that present in the impulsive phase.
Required Observations/Analysis Techniques: 1) Establish and implement SXT observing modes with the best possible SNR for faint, diffuse, hard-spectrum coronal sources 2) Develop techniques for analysis of HXT data for faint, diffuse sources 3) Compare Yohkoh results for selected events with radio observations. The theoretical objectives are 1) Intercompare non-thermal structures with thermal structures, as observed in SXT soft X-ray images 2) Identify mechanisms for particle acceleration and trapping in coronal structures, including shock waves, and 3) Provide quantitative input for understanding radio emission mechanisms
Update 11-Nov-96
Abstract of paper presented at the Solar Physics Division meeting, Madison, WI (June, 1996):
X-ray Images of Two Type II Bursts
H.S. Hudson
The Yohkoh soft X-ray telescope has been providing high-resolution images of the counterparts of various meter-wave phenomena. We report here on clear examples of Type II emission in flares of 13 and 20 October, 1995. These flares had highly structured meter-wave dynamic spectra (Culgoora). The X-ray images show no sign of concentric wave fronts, according to the standard interpretation of the Type II burst phenomenon. Instead we see a series of loops emerging from the flare regions. We interpret the fine structure in the X-ray images as the origin of the patterns in the dynamic radio spectra, and attempt thereby to compare the densities independently inferred from the radio and X-ray observations.
Update 24-Feb-96
Two Type II burst events occurred 13 Oct. and 20 Oct. 1995, both well-observed by Yohkoh with HXT in its "spectrum" mode with 64 energy channels at 8 sec cadence. The SXT observations show lovely loop expansions, and Lemen has placed a composite movie of the 20 Oct. event on the video disk at ISAS. These events are ideal from the point of view of understanding the soft and hard X-ray signatures of the Type II burst disturbance in the low corona as it propagates away from the flare site. The two events had very different starting frequencies even though both were in the same active region. An abstract on these observations will be submitted to the AGU 1996 Spring meeting.
Update 13-May-95
Abstrct of paper submitted:
Detection of Nonthermal Radio Emission from Coronal X-ray Jets
M.R. Kundu, J.P. Raulin, N. Nitta, H. Hudson, M. Shimojo and A. Raoult
Abstract
We report the detection of a type III burst in association with a dynamic X-ray coronal jet observed by Yohkoh/SXT. The type III burst, observed with the Nancay (France) multifrequency radioheliograph, spatially and temporally coincided with the X-ray jet. The radio locations at different frequencies (236.6 and 164 MHz) are aligned along the length of the jet. The observation of a type III burst in association with an X-ray jet implies the acceleration of electrons to several tens of Kev, along with the heating responsible for the production of X-rays. This association identifies a bundle of open field lines in the periphery of an active region. This is the first direct observation of the dense coronal channel along which the non-thermal electrons of a type III burst travel. We find that this channel begins to form before the type III emission, and that at the time of the type III burst we estimate a density XX for a temperature of 7 MK at an altitude of 20,000 km.
Update 12-Aug-94
New author list:
H. Hudson, M. Kundu, N. Nitta, M. Shimojo, N. Gopalswamy, M. Pick, J.-P. Raulin
Two or three new TBB items that overlap with this one, but are more specific, have been submitted. One of these involves a potential PhD thesis in France. Using the Shimojo list of X-ray jets, Raulin has found two matching events in which anemone-type jets occur with type III groups. The match in time and position is excellent. This result, combined with the Pick et al result published in the Kofu proceedings, convincingly establishes the association of coronal heating with streams of non-thermal electrons outside flares. The Kofu proceedings also has the Kundu et al paper on type III bursts from flaring bright points.
Update 06-Nov-93
Two interesting cases of meter-wave counterparts in SXT images have now been found. This is work in progress by M. Kundu and by M. Pick:
Type III: Kundu found clear evidence for low-level type III emission at the same position as a "squirter" jet seen in SXT FFIs. This was the event of 20-jan-93 22:29:10, and was reported by S. White at the SPD meeting at Stanford.
Type III-V(?)-reverse drift: Pick found such an event in dynamic spectra from Porto (Portugal), and then with the Nancay array. It corresponds with a large transient loop structure seen 18-aug-92 13:00:10.
These two events demonstrate the validity of the concept that SXT can see the coronal structures in which the meter-wave dynamical bursts happen. We hope this is only the beginning!
Update 11-Mar-93
Nitta and I looked at the movie to see if it was easy to spot Type III burst channels. It wasn't, but more of this should be done. I intend to do a comprehensive search by this means, since it is so easy, using the movie and a listing from pr_gev.
I have made a catalog of SAA flares, for which remote diffuse structures may be seen. While this is not a very good way to search for counterparts of Type IV bursts and Type II bursts, it is something.
Update 05-Aug-92
X-Ray Counterparts of Meter-Wave Coronal Events
Collaboration: H. Hudson, N. Nitta
Progress as of July 23:
(a) We ran a special SXT sequence table with long exposures, Be filter, at the W limb following the limb passage of hot region 7205. This special observation included an offset pointing to maximize the exposure to the corona above the region that had rotated off. At first glance, this first effort failed - there was a major event, but it was on the opposite limb!
(b) It proved to be quite easy to spot Type V events, and an SXT structure associated with one occurred on June 16, 1992, at about 2100 UT. A systematic search for III's, IV's, U's, and reverse drift events seems like it may be fruitful.