Velocity shifts in flare spectra during plasmoid ejections Original Research Article

In some limb flares observed by Yohkoh Soft X-ray Telescope plasmoid ejections are observed. Simultaneous BCS flare spectra exhibit wavelength shifts to the red or blue sides. The shifts observed in BCS spectra cannot be explained by instrumental effects. Results of fitting show that the changes in the line profile are best described by one moving gaussian which fits most of the emission. This suggests that the line shifts are produced more likely by the main bulk of plasma seen by BCS. In our opinion the results of this analysis suggest that spectral shifts observed in Fe XXV spectra are not due to the plasmoid movement seen on SXT images, but come from the main emission kernel. Very good temporal coincidence of both effects however indicate that they are not independent. Both observed movements can be a result of magnetic field reconfiguration during the flare rise phase.