Institution: | a Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, U.K. b School of Physics and Space Research, University of Birmingham, Birmingham B15 2TT, U.K. c Astrophysics Division, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, U.K. d DASOP, Observatoire de Paris, 92195, Meudon Principal Cedex, France e Astronomical Institute of Wroclaw University, ul. Kopernika 11, PL 51-622, Wroclaw, Poland f Hiraiso Solar Terrestrial Research Center, Communications Research Laboratory, Nakaminatoshi, 311-12, Ibaraki, Japan |
Abstract: | Yohkoh has observed many long duration events permitting a statistical study of the properties of these interesting events. We have selected ten flares for analysis which have durations between 5 and 20 hours, and size ranging from C to X GOES class. Employing the Soft X-ray Telescope, the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based H data, we examine the morphology, temperature, emission measure, location of the hard X-ray source, non-thermal velocities and upflows of the plasma at different stages in the flare development. Our results are used to address the question of the energy source that maintains the hot plasma at temperatures of several million degrees for many hours. |