Search Publications
Dynamics of Blinkers
Harrison, R. A.; Parnell, C. E.; Pike, C. D. +1 more
The relative Doppler and non-thermal velocities of quiet-Sun and active-region blinkers identified in O v with CDS are calculated. Relative velocities for the corresponding chromospheric plasma below are also determined using the He i line. O v blinkers and the chromosphere directly below, have a preference to be more red-shifted than the normal t…
Hard x-ray Pulsations in the Initial Phase of Flares
Karlický, M.; Fárník, F.; Švestka, Z.
When analyzing light curves of hard X-ray bursts recorded by the Hard X-Ray Spectrometer on board the MTI satellite, we have found three events (all associated with major solar flares, two of them in the same active region) which show pulsations in the very initial phase of the burst. Periods of the pulsations range from 25 to 48 s. We compare the…
Magnetic helicity transport in corona and filament eruptions
Romano, P.; Contarino, L.; Zuccarello, F.
Using a 28-hour time series of line-of-sight magnetograms taken by the Michelson Doppler Imager (MDI), we determined the magnetic flux variations and the rate of magnetic helicity transport at the footpoints of a filament in active region NOAA 8375. The filament was characterized by a positive helicity change due to shearing motions in both footpo…
Interaction of an Erupting Filament with the Ambient Magnetoplasma and Escape of Electron Beams
Vršnak, Bojan; Warmuth, Alexander; Otruba, Wolfgang +2 more
A huge filament eruption of 12 September 2000 associated with a two-ribbon spotless flare is described. During the acceleration phase the shape of the filament changed, and signatures of topological restructuring of large-scale coronal magnetic fields were inferred by tracking changes of nearby coronal holes. At the same time electron beams associ…
Variations in Oscillation Frequencies From Minimum to Maximum of Solar Activity
Jain, Kiran; Bhatnagar, A.
The temporal variation in intermediate-degree-mode frequencies is analysed using helioseismic data which cover the minimum to the maximum phase of the current solar cycle. To study the variation in detail, the measured frequency shifts of f and p modes are decomposed into two components, viz., oscillatory and non-oscillatory. The f-mode frequencie…
Coronal Oscillations above Sunspots?
Doyle, J. G.; Dzifćáková, E.; Madjarska, M. S.
Observational data clearly indicate the presence of 3-min oscillations in sunspots in spectral lines covering a vast temperature range from the low chromosphere to those lines normally associated with coronal temperatures. We show that after folding in the sunspot plume emission measure distribution, the contribution functions for lines normally f…
Giant Meterwave Radio Telescope observations of an M2.8 flare: Insights into the initiation of a flare-coronal mass ejection event
Janardhan, P.; Kundu, M. R.; White, S. M. +3 more
We present the first observations of a solar flare with the GMRT. An M2.8 flare observed at 1060 MHz with the GMRT on 17 November 2001 was associated with a prominence eruption observed at 17 GHz by the Nobeyama radioheliograph and the initiation of a fast partial halo CME observed with the LASCO C2 coronagraph. Towards the start of the eruption, …
Photospheric and chromospheric oscillations in the base of coronal holes
Kobanov, N. I.; Makarchik, D. V.; Sklyar, A. A.
In this paper we carry out an analysis of the spatial-temporal line-of-sight velocity variations measured in the chromospheric (Hα, Hβ) and photospheric (Fei 6569 Å, Fei 4864 Å, Nii 4857 Å) lines at the base of 17 coronal holes. Time series of a duration from 43 to 120 min were recorded with the CCD line-array and the CCD matrix. Rather frequently…
Detection of the Long-Term Microwave `Darkening' Before the 14 July 2000 Flare
Tokhchukova, Susanna; Bogod, Vladimir
A gradual microwave darkening during several days of the preflare phase in the active region (AR) NOAA 9077, before the powerful proton event on 14 July 2000 was detected. The associated change of the circular polarization structure in the form of narrow-band double inversion of the sign was marked. The effects were revealed in a wide range of rad…
Structure and Evolution of the Transition Region Network Observed in he ii λ304
Venkatakrishnan, P.; Ravindra, B.
The length scale and life time of the transition region network cells were studied using He ii λ304 filtergrams. The temporal structure function was calculated from spatially aligned He ii λ304 images. The estimated life time of the network cell was about 27 hr. We compared this life time with the life time of photospheric magnetic network and of …