ar070.kundu04 Posted: 28-Aug-94 Updated: 10-Jun-95 Events specified: N/A
M.Kundu. J.P.Raulin, S.White, N.Nitta, H.Hudson, K.Shibata and M.Shimojo
An imprtant discovery made by Yohkoh/SXT is the frequent occurrence of jet-like features, i.e.,transitory x-ray enhancements with an apparent collimated motion(Shibata et al, PASJ,44,L173,1992).It seems likely that their motion is a real flow of plasma, as indicated,for example, by association with an H-alpha surge.However, no doppler shifts have yet been detected by the Yohkoh /BCS instrument that can be directly linked to them. Many of these jets are associated with flares in XBPs,EFRs and ARs.This is a proposal to search for radio emission from these jets.There have been several morphological classes of jets mentioned in the literature (e.g. Shibata et al, KOFU Proc.1994),of which two are important from the radio emission point of view.
1)Jets ejected from XBPs 2)Jets ejected from EFRs and ARs The first one is related to XBPs , and we have already found nonthermal radio emission in the form of type III bursts from flaring XBPs ( Kundu etal,ApJ Lett.427,L59,1994).No attempt was made to specifically associate the radio emission with the XBP jets, but the study will be the same as for flaring XBPs. In the second category,there are "anemone-like"jets and "two-sided"jets. We believe that we have already identified two cases of jets, probably "anemone-like", which are associated both temporally as well as spatially with type III radio bursts over a broad frequency range , 150-450 MHz(these are Dec 6,1991 and April 21,1992 events).We have not found good examples of two-sided jets to search for radio emission from:we are presently talking to Shimojo san on this subject.When Shibata san returns from U.S. we can finalize some of the practicalities.We would like to note that we expect different varieties of type IIIs for "anemone-like" and "two-sided" jets. In the former we expect a broad frequency range of the type IIIs because the typeIII- producing electron streams will be propagating radially producing plasma waves along the way, while in the latter the electron streams will propagate more or less parallel to equi-density levels of the sun's atmosphere.This meter wave study will thus permit us to test the models of coronal jets. This Tbb proposal is meant for a general study of all Shibata jets which fall under the categories mentioned as items 1 and 2 above.
Update 10-Jun-95
This project is still on-going, entering another phase. For this update, we report the following.
Paper accepted for publication in ApJ Letters:
Detection of Nonthermal Radio Emission from Coronal X-ray Jets
M. R. Kundu, J. P. Raulin, N. Nitta, H. S. Hudson, M. Shimojo, K. Shibata, 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 Nanay (France) multifrequency radioheliograph is spatially and temporally coincident 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 the type III burst in association with the X-ray jet implies the acceleration of electrons to several tens of keV, along with the heating responsible for the production of soft X-rays. This association implies the existence of open field lines in dense coronal structures identified on the sun's disk. This is the first observation of dense coronal structures on the disk, along which type III emitting nonthermal electrons propagate. We find that this structure begins to form before the type III emission. At the time of the type III burst we estimate a density of 6-10 y 108 cm-3 for a temperature of ~ 5-6 MK at an altitude of 20000 km.
Paper submitted to A & Ap
Metric Type III Bursts Associated With Soft X-Ray Jets
J.P. Raulin, M.R. Kundu, H.S Hudson, N. Nitta, and A. Raoult
Abstract
From soft X-ray and metric radio observations with high temporal and spatial resolution, we show that electron acceleration in the form of Type III bursts occurs in association with coronal jets observed by the Yohkoh soft X-ray telescope. The excellent correspondence between the positions of the radio sources observed at different frequencies and the X-ray jets strongly suggests that electron beams propagate along the relatively dense paths formed by the jets. Assuming a constant temperature for the jets, one can estimate the electron density from the soft X-ray measurements. These computed electron densities agree well with the values derived from Type III bursts produced by the plasma emission process. The observations are consistent with the idea that strong particle acceleration accompanies magnetic reconnection in these events as well as in solar flares.