Solar Active Processes and Interplanetary Medium Properties

Scientific activities develop within the scope of international programmes, recently of International Solar Cycle Studies first of all. The bilateral and multilateral co-operation is used widely.

In 1975 Rybanský introduced a new coronal index (CI) of solar activity. The time series of daily values is prepared since 1939 and are available at AISAS (e.g. Rybanský et al. 1996, 1998a, and Storini & Sýkora 1997). A basis for the computation of CI are observations of the green corona intensities (Fe XIV, 530.3 nm) from coronal stations all over the world, the data being transformed to the Lomnický Štít photometric scale. This index was accepted by the scientific community as a basic optical index of solar activity and is frequently named "Slovak green corona index" (Donelly 1990).

Synthesized homogeneous database of the FeXIV 530.3 nm coronal emission line intensities (1-day resolution in solar longitude, 5 degrees resolution in solar latitude) covering almost five solar cycles (1/1/1943 - 12/31/1996) was created. This database is used to study time-latitude distribution of the emission corona and prominences over solar cycles (Rybanský et al. 1998b, c, d; Minarovjech et al. 1998).
     The basic characteristics of cycle 23 were predicted by means of a complex study of the time-latitudinal distribution of prominences and the emission corona.
     Coronal features are studied intensively during solar eclipses (e. g. Rušin & Rybanský 1995, 1996, 1997; Lorenc et al. 1996; Rušin et al. 1996; Rušin et al. 1997; Pintér et al. 1997, and Sýkora et al. 1996).
     Anticorrelation between the polarization and brightness of the green solar corona given by the emission line Fe XIV 530.3 nm intensity was found (Sýkora et al. 1997; Sýkora & Parisi 1998).
     Odd and even 11-year cycles which constitute 22-year cycles are significant in solar corona, too, odd cycles being more active than the even which are the starting ones within 22-yr cycles (Storini & Sýkora 1996a, 1997d, and Sýkora & Storini 1997).
     Solar corona is studied with respect to coronal magnetic field structures (Sýkora & Ambrož 1997), to LDE-type flares (Antalová 1995), to galactic cosmic ray modulation (Antalová et al. 1995a, b; Antalová 1998, and Sýkora & Ambrož 1997) to the solar wind streams (Sýkora 1997) and to other solar processes (Dorotovie et al. 1996, Dorotovie et al. 1997; Dorotovie & Rybanský 1997).
     The polarization of the 530.3 nm coronal line was considered (Badalyan & Sýkora 1997a). Badalyan & Sýkora (1997b) and Badalyan et al. (1997) have studied the dynamics of large-scale coronal structures.
     The middle-latitude zones of the solar corona were argued to be the most dynamic, active and mainly relevant for the heliospheric activity. Dzifeáková & Rušin (1997) reported the North-South asymmetry in the green corona.
     The solar soft X-ray daily flare index introduced by Antalová earlier is used for studies mentioned above (Antalová 1998). The non-flare and flare solar soft X-ray parameters were compared (Storini et al. 1998).

Analysis of dynamics of the chromosphere and photosphere from the SOHO-SUMER spectra revealed significant spatial differences between the supper-granular internetwork and boundary as well as different behaviour of temporal changes in chromospheric and transition region lines, oscillations being included (Curdt et al. 1997 and Kueera et al. 1998). The Doppler velocities up to 20 km/s were detected in the quiet solar atmosphere when the spatial resolution of 2 arc sec was reached.
     The analysis of observations by means of VTT-Tenerife and of SOHO-SUMER satellite data shows that emission line shiftings can be attributed to the apparatus effects (Kueera et al. 1998).

The analysis of the spotless flares using the YOHKOH soft X-ray data has shown that those are usually initiated by interaction of two large-scale loop systems in the corona (Šeršeo 1995).

The analysis of dynamics of solar sporadic activity in cycle 22 has confirmed the discontinuity in the CME occurrence and also revealed its replications in the occurrence of other phenomena in the Sun-interplanetary medium-Earth system (Prigancová et al. 1997 and Prigancová & Bieleková 1997).

The long-term modulation of galactic cosmic rays was investigated in the period 1957-1992 analysing the dynamic and the quasi-stationary components, separately. It has been found that the CR dynamic component is characterized by the presence of two peaks at the maximum phase of each solar activity cycle. According to the latest Sýkora's results, the time interval between the two peaks corresponds to the period of the polar heliomagnetic reversal. The role of solar magnetic field configuration in the solar activity development is emphasized (Bumba et al. 1995).
     Cross-correlation analysis between galactic CR intensities (Calgary NM) and the solar flare East-Central-West distribution on a daily basis has proven that the heliospheric structures associated with the western flares are (in comparison with central and eastern events) less effective as far as the CR modulation is concerned.

Kudela & Venkatesan (1995) revealed the fractal structure of cosmic ray intensity variations. Some characteristics of the CR diurnal variation were reported (Anant et al. 1995).
     The anisotropy and solar activity modulation was reported for solar neutrino fluxes (Massetti et al. 1995, 1998). The study of the new data set from the Homestake experiment (1970-1994) outlines the following facts in the solar neutrino flux variability: i) there exists a negative correlation with the 11-yr solar activity cycle; ii) the neutrino flux is characterized by a North-South asymmetry with a roughly 12-yr periodicity which is practically in phase with the solar activity cycle; iii) the anticorrelation of the total neutrino flux with the coronal green line brightness, as measured within the solar equatorial zone (± 15° of solar latitude) is statistically significant (correlation coefficient R = -0.41) with a confidence level better then 99%.

Most of results referred were also presented at the international meetings and conferences (e.g. Antalová et al. 1995; Antalová 1996a-e; Badalyan et al. 1997; Badalyan & Sýkora 1997a, b; Kudela et al. 1996a, b; 1997; Rybák 1995; Storini & Sýkora 1995, and Sýkora & Ambrož 1995).