Preliminary analysis of Hα images of high-altitude coronal condensation known as “coronal spiders” is presented. The kinematics of material seen draining from the coronal spiders are also studied. An estimate of the mass of the object for a range of electron temperatures and electron densities is obtained.

Data on the May 1, 1996 prominence eruption, jointly observed by CDS, SUMER, and EIT, aboard SOHO, Yohkoh-SXT, and Kitt Peak and Meudon observatories are analyzed to obtain information on the plasma temperature, density, and velocities, as well as the magnetic field topology and strength. It is found that the ‘standard’ model of an erupting helical flux tube probably applies, although questions arise on the MHD stability of the prominence flux tube. The prominence is observed to remain relatively cool during its eruption (≤ 5 × 105 K), while the density and velocity vary considerably on scales down to the limit of resolution. It is found that the high density, high velocity plasma blobs can be contained by the relatively weak magnetic field, as is indeed observed.

The kinematics and dynamics of prominence eruptions are reviewed and different phases of the eruption are identified. The properties of the equation of motion in these phases are shown. The morphology of the prominence prior and during the eruption is described and the implications to the MHD description of the process are discussed.

A violent evolution of the September 18, 1995 eruptive prominence is studied. The fast changes of the prominence structure started immediately after a weak radio burst on 3 GHz indicating the presence of non-thermal processes. A comparison with Yohkoh soft X-ray pictures was made. A detailed analysis of observations indicates magnetic field line reconnection, mainly in the space below the rising Hα prominence. The reconnection processes are manifested by structural changes of the Hα prominence and X-ray loops and also by the character of Doppler velocities in the Hα spectrum formed close to the reconnection space.

Observational evidence of 3 and 5 min vertical oscillations of a filament on the disk are recorded. Wave activity was observed before, during and after a filament disappearance, inside and around the filament. Both an Hα brightening and, later, a blowing out of a faint soft X-ray (Yohkoh) loop system occuring in connection with a flare were noticed. The wave activity seems to be a dynamically important ingredient of this erupting prominence.

Propagating MHD waves and convective structures bring their energy and momentum from the photosphere towards the chromosphere up to the coronal heights where they are partially reflected and/or dissipated. The transition from the laminar to the turbulent state of the whole prominence enhances the dissipation rate of the external waves inside this system, adding energy to produce the heating and lifting of the plasma. Internal plasma instabilities could trigger this transition in the framework of a prominence disappearance.

SOHO (SUMER/CDS) observed an eruptive prominence on May 1,1996, associated with a CME observed by LASCO. We investigate the physical conditions of this prominence in order to quantify velocity, temperature, and density. SUMER spectra in Si IV and O IV lines are used to obtain Doppler-shift images of the prominence. The prominence shows large-scale red and blueshifted regions, revealing a large helical structure with a global twist. In addition, fine structure analysis shows multiple components in the line profile, suggesting integration of many threads along the line-of-sight with a large dispersion of velocities (±50 km s−1).

Our results in the field of observing prominences at our observatory show dual eruptive prominences on June 29, 1994 obtained by a coronograph at our observatory at Valašské Meziříčí. We tracked the evolution of these eruptive prominences in time and morphology.

Hα and H Ca II emission lines in a limb quiescent prominence (QP) undergoing destabilization are studied. The temperature, line-of-sight velocity and micro-turbulence are obtained in one of the prominence legs, just before and during the prominence activation.

It is well known that quiescent prominences (QPs) as well as active region prominences (ARPs) occasionally undergo eruptions. The process of eruption of these prominences is caused by eruption of a huge magnetic system (HMS) associated with the prominence channel and the prominence itself (Rompolt 1984). Material of these prominences is frozen-into only a part of such a magnetic system – before as well as during the eruption. When an HMS erupts it simply lifts with it the frozen-in prominence material.

Usually during the eruption a large part of the prominence material is lifted high into the corona and/or into interplanetary space. Nevertheless, on some occasions during the eruption a significant part of the original prominence material flows down to the chromosphere (Rompolt 1990).

The analysis of an eruptive prominence and disappearing quiescent filaments indicates that the prominence height on the limb increases after the filament develops a twist as seen in the Hα on the disc. The increase in prominence height, large change in the shear angle, and the appearance of filament as a U-shaped structure before the disappearance of the filament or prominence eruption can be explained by assuming that the middle portion of the filament rises above the solar surface with its edges anchored in the chromosphere. Further, the loop-like structure of the filament splits into two parts 2–3 days prior to its disappearance and the gap between the two increases with time. The increasing gap and simultaneous disappearance of both parts of the filament suggests that heating of the top of the loop-like structure begins about 2 days before its disappearance. The cause for this portion of the filament not being visible in Hα may be that it is heated to a high temperature.

In this paper we present CCD observations between February 14–20, 1994 and analysis of the giant twisted filament evolved in the active region NOAA 7671. The dynamic eruption of the filament was accompanied by a major flare (3B/M4), CME, long duration type II, IV radio bursts, great microwave bursts, a long duration soft X-ray burst, SIDs, strong geomagnetic storms and a very energetic proton flare. We analysed and estimated the twist, length, volume, mass and energy associated with filament system between February 14 and 20, 1994. The present study shows that the magnetic energy required for the solar flare came from the filament system associated with the solar flare and associated phenomena.

Observational and theoretical aspects of filament destabilization are reviewed in light of the concept of filament eruption as catastrophic loss of equilibrium in a magnetic configuration of inverse polarity. Interrelations between eruptive prominences and other phenomena of solar activity such as flares, CMEs, and loop arcade are considered.

We analyze a prominence model containing a flux rope which is completely detached from the photosphere. The maximum magnetic energy which can be stored in the configuration does not exceed the open-energy limit proposed by Aly and Sturrock. However, a loss of ideal-MHD equilibrium can occur and create a current sheet which is likely to undergo rapid reconnection.

The possibility of multiple reflections generating standing surface wave modes carrying field-aligned current (FAC) in an arch-like prominence structure is studied. The conditions for enhancement of FAC leading to observable destabilising effects are specified.

Prominence eruption is one of the most important solar phenomenon because of the possibility of using it as proxy of geoeffective solar disturbances. In a series of investigations using Nobeyama radio observations in conjunction with Yohkoh data we have found that there is more to a prominence eruption than the simple picture portrayed by Hα observations. The extent of coronal volume associated with the eruption is much larger than the prominence. We illustrate this with several examples and discuss the implication of the results for understanding the interplanetary manifestation of coronal mass ejections.

During the September 1996 campaign of multi-wavelength observations with the SOHO (SUMER, CDS, EIT, MDI, LASCO) and Yohkoh (SXT) spacecraft, the HAO Mauna Loa Solar Observatory Chromospheric Helium Imaging Photometer and the Nobeyama radioheliograph, a filament disparition brusque (DB) associated with a Coronal Mass Ejection (CME) was observed. The timeline of this complex event, which lasted for tens of hours, shows that the CME had started before the DB of a filament, while the main “bubble” of the CME was probably launched hours after the DB from the so-called “zipper” region. All these suggest that a general reorganization of large-scale fields was taking place on the Sun, and both the DB and the CME were symptoms of this.

A coronal mass ejection (CME) event was observed on December 23, 1996 with the Ultraviolet Coronagraph Spectrometer in both ultraviolet and visible light channels at 0.5 R⊙ over the solar limb. The CME was followed during its evolution in the bright lines of Lyα (1216Å), Lyβ (1026Å), Lyγ (972Å), C III (977Å) and the OVI doublet (1032, 1037Å) and in several weaker lines. The Lyα peak intensity shows an excursion of two orders of magnitude during the CME evolution, and blue shifts up to 0.8Å (~200 km/sec). The data provide the emission measure in the Log T range 4.0–5.5 with a 0.3 sampling. Line intensities and profiles have been measured, providing important diagnostics for a detailed study of the CME’s physical and dynamical parameters.

Evolution of magnetic structures in the region around an eruptive prominence of August 28, 1992 are examined using soft X-ray images obtained by Yohkoh. The eruption was preceded by the appearance of a large-scale soft X-ray jet which was ejected from near the root of the southern end of the prominence. Changes of magnetic geometry at the southern end of the prominence appeared to trigger the eruption. In the course of prominence eruption, helically twisted soft X-ray loops were observed around the prominence. This indicates that magnetic reconnection of a sheared arcade took place underneath the erupting prominence.

DB (disparition brusque) events are associated with dynamic phenomena such as a CME, a flare, brightening of a soft X-ray arcade, and soft X-ray dimming, and probably a change of the coronal magnetic field on a large scale. The DB event observed on January 16, 1993 identified with a CME occurred on the solar disk.

A magnetohydrodynamic simulation in a 2.5D approximation is performed for the quadrupole source model for arcade flares treated years ago by Uchida (1980), and recently supported by the observations from Yohkoh. It is shown that this model can explain several key characteristic features of arcade flares found by Yohkoh, and can avoid some of the paradoxes existing in the “classical model”.