Solar activity in the past and the problem of solar dynamo

We study a new indirect index, or proxy data, of the solar activity - the intensity of luminescence of the microzones of cave flowstones. This index is in anticorrelation with the index deposition rate of ¹⁴C and in direct correlation with the solar activity as in thermoluminescent time series of sediment cores. Luminescence time series was obtained for long time intervals with different time resolution (from 5 years per pixel to 5 pixels per year). In such time series the long minima of Maunder and Spoerer, the Medieval maximum and other well known long lasting minima and maxima as well as some new ones can be seen. The very good resolution permits to study the general statistical properties of past solar activity. Some of the results obtained refer to the problem of the mechanism of solar magnetic field generation.     

Prominence activity during the ascending phase of solar cycle 22

Longitude-latitude and time-latitude distributions of the number and area of prominences observed at Lomnický Stit coronal station in the years 1986–1990 are studied using the method of contour maps construction with different degree of smoothing. Special attention is paid to the bifurcation in the prominence distribution. Comparison with the ascending phase of solar cycle 21 is made.     

Line-of-Sight Velocity Fluctuations of a Quiescent Prominence

Series of H spectra and slit-jaw H filtergrams of a quiescent prominence taken at Pic du Midi Observatory on 7 November 1977 are studied. The observations have been digitized by means of an automated Joyce Loebl microdensitometer. The image processing of the H filtergrams reveals an internal structure of the prominence consisting of several arches. Series of high-resolution H spectra obtained with the slit position located on a selected part of one of the prominence arches have been chosen for Doppler-shift analysis. The obtained time series of the line-of-sight velocity reveal large velocity variations near the periphery of the arch and a strong dependence of the velocity (in sign and magnitude) on the position along the slit. The prominence arch shows also cyclic displacements along the line-of-sight direction implying Alfvén string-mode oscillations.     

Periodicities in the N-S asymmetry of long-lived solar filaments

The N-S asymmetry of the long-lived solar filaments published in the Meudon catalogues for the time interval 1919–1989 is studied by means of power-spectrum analysis. Statistically significant periods of 35.0 and 11.7 yr are obtained. There are no statistically significant periods shorter than 11 yr.     

Faint Hα emission in the solar corona: Morphological,situational and hydromagnetic analysis

Very faint H emission in the solar corona registered on over-exposed photographs made by a coronagraph and an H filter is studied. The over-exposed filtergrams have been processed by a Joyce Loebl automated microdensitometer and the two-dimensional scans have been analysed by the residual image method. A classification of the faint H emission objects, revealed on the isodensity maps, is proposed and the latitudinal distribution, the morphology, and the location with respect to the other active phenomena are analysed. Taking into account some possible plasma effects that could be caused by coronal magnetic field changes, a hydromagnetic interpretation of the faint H emission is proposed.