COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 3244

                                                         Konkoly Observatory
                                                         Budapest
                                                         29 September 1988

                                                         HU ISSN 0374 - 0676


         THE MECHANICAL ENERGY BUDGET IN STELLAR FLARES

Flares on the Sun and on dKe-dMe stars are now widely believed to be
basically similar in their origin and development. This is in spite of the
fact that stellar flares are normally at least 10^3 and often 10^5 times more
energetic than even the largest of their solar counterparts. In general, both
phenomena are believed to arise from the rupture of a stressed magnetic
structure, commonly termed a magnetic loop, which by magnetic buoyancy
is forced upwards through the photosphere into the corona/transition region,
where reconnection of the magnetic field occurs followed by a considerable
release of energy. Initially this energy is believed to be carried by fast
particles, such as electrons or protons, which, collimated by the magnetic
field, move down towards the surface of the star where they bombard denser
material and give rise to local heating and chromospheric evaporation (e.g.
Doyle et al., 1985).
   The major objective of this international corroborative project (involving 
Armagh Observatory, the Institute for Astronomy at the University of
Catania, Goddard Space Flight Center, the Joint Institute for Laboratory
Astrophysics of the University of Colorado, the Rutherford-Appleton Laboratory, 
the Laboratoire de Physique Stellaire et Planetaire du CNRS and the
Institute of Astrophysics at Oslo) is to collect multiwavelength, i.e. optical,
ultraviolet and X-ray; and in particular to obtain spectral and temporal
resolution data of the higher Balmer lines in order to look for doppler
motions. Evidence for such mass motions has been seen in low resolution
spectroscopy (Doyle et al., 1988, Phillips et al., 1988). Such data will
enable us to form some estimate of the mechanical energy budget from doppler
shifts in spectral lines and compare with the X-ray energy. For this program,
two ESA IUE 8 hr. shifts and one GINGA (i.e. the Japanese X-ray satellite) 24
hr, shift has been allocated. In addition we have requested three European
Southern Telescopes and the Anglo-Australian Telescope to do high resolution
spectroscopy (covering the higher Balmer lines, i.e. H_gamma, H_delta etc.,
with a spectral resolution of ~1A and the time resolution of ~1 min.) and to
monitor the overall activity of the star in UBVRI and K bands. VLA time
has also being requested.
   We welcome the participation of any observer who can contribute 
either photometric or spectroscopic observations. Interested observers are
requested to contact the undersigned and to notify us of their telephone
and telex numbers and/or their electronic mail address.


                     J.G. DOYLE

                  Armagh Observatory
                    College Hill
                   Armagh BT61 9 DG
                     N. Ireland


Tel: (44) 861 522928
Fax: (44) 861 526187
Telex: 265871 (on the 1st line of telex,
please quote ref: MAG32510)
JANET electronic mail address: JGD%UK.
AC. QUB.ARM.STAR



References:

Doyle, J.G., Byrne, P.B., Dennis, B.R., Emslie, A.G., Poland, A.I., Simnett,
   G.M., 1985, Solar Phys. 98, 141. [BIBCODE 1985SoPh...98..141D ]
Doyle, J.G., Butler, C.J., Byrne, P.B., van den Oord, G.H.J., 1988, Astron.
   Astrophys. 193, 229. [BIBCODE 1988A&A...193..229D ]
Phillips, K.J.H., Bromage. G.E. Dufton, P.L., Keenan, F.P., Kingston, A.E.,
   1988, M.N.R.A.S. (in press) [BIBCODE 1988MNRAS.235..573P ]