- Open Access
Downflows and structure above LDE arcades: Possible signatures of reconnection?
Earth, Planets and Space volume 53, pages577–580(2001)
We will introduce a set of observations made during the decay phase of long duration event (LDE) flares on the Sun. In a number of events, the soft X-ray images from Yohkoh SXT indicate a downward directed flow field in the region immediately above the flare arcade. These are tentatively identified as evidence of reconnection outflows. The prototypical event is the M5 flare of 20 January 1999, presented by McKenzie and Hudson (1999); since the time that paper was completed, sixteen more events have been found in the interval April 1998 to February 2000. As in the 20 January event, the speeds of downflow are 35–500 km s−1, lower than both the freefall speed and the typically assumed Alfvén speed. The motion is evidenced by both dark and bright (i.e., X-ray emitting) features, some of which may have a looplike morphology; no cool counterparts have been detected in Hα or EUV observations. Movies depicting some of the LDE downflows were presented at this meeting; these also appear in the journal Solar Physics (McKenzie, 2000), since they cannot be presented in these Proceedings.
Delaboudinière, J.-P., et al., EIT: Extreme-ultraviolet imaging telescope for the SOHO mission, Sol. Phys., 162, 291, 1995.
Forbes, T. G. and L. W. Acton, Reconnection and field line shrinkage in solar flares, ApJ, 459, 330, 1996.
Forbes, T. G. and J. M. Malherbe, A shock condensation mechanism for loop prominences, ApJ, 302, L67, 1986.
Hiei, E. and A. J. Hundhausen, Development of a coronal helmet streamer of 24 January 1992, in Magnetodynamic Phenomena in the Solar Atmosphere, edited by Y. Uchida, T. Kosugi, and H. Hudson, p. 125, Kluwer Academic Publishers, Dordrecht, Holland, 1996.
McKenzie, D. E., Supra-arcade downflows in long-duration solar flare events, Sol. Phys., 195, 381, 2000.
McKenzie, D. E. and H. S. Hudson, X-ray observations of motions and structure above a solar flare arcade, ApJ, 519, L93, 1999.
Schmieder, B., T. G. Forbes, J. M. Malherbe, and M. E. Machado, Evidence for gentle chromospheric evaporation during the gradual phase of large solar flares, ApJ, 317, 956, 1987.
Švestka, Z., Solar flares—the gradual phase, Sol. Phys., 121, 399, 1989.
Švestka, Z., F. Fárník, H. Hudson, and P. Hick, Large-scale active coronal phenomena in Yohkoh SXT images—IV. Solar wind streams from flaring active regions, Sol. Phys., 182, 179, 1998.
Tsuneta, S., et al, The soft X-ray telescope for the solar-A mission, Sol. Phys., 136, 37, 1991.
Yokoyama, T., et al, Clear evidence of reconnection inflow of a solar flare, ApJ, 546, L69, 2001.
About this article
Cite this article
McKenzie, D.E., Hudson, H.S. Downflows and structure above LDE arcades: Possible signatures of reconnection?. Earth Planet Sp 53, 577–580 (2001). https://doi.org/10.1186/BF03353273
- Current Sheet
- Coronal Mass Ejection
- Will Emit
- Prototypical Event
- January Event