ALBERT

Notes: Abstract The paper reports the results of the analysis of the data on polar faculae for three solar cycles (1960–1986) at the Kislovodsk Station of the Pulkovo Observatory and on polar bright points in Ca ii K line for two solar cycles (1940–1957) at the Kodaikanal Station of the Indian Institute of Astrophysics. We have noticed that the monthly numbers of polar faculae and polar bright points in Ca ii K line and monthly sunspot areas in each hemisphere of the following solar cycle have a correlation with each other. A new cycle of polar faculae and polar bright points in the Ca ii K line begins after the polar magnetic field reversal. We find that the smaller the period between the ending of the polar field reversal and the beginning of a new sunspot cycle is, the more intense is the cycle itself. The intensity of the forthcoming solar cycle (cycle 22) and the periods of strong fluctuations in activity expected in this cycle are also discussed.

Notes: Abstract The coherence and phase spectra between velocity oscillations in different pairs of lines have been studied. The oscillation in the high level lines are found to lag behind those in the low level lines in general. There is high coherence between oscillations at the different levels. The phase differences between the velocities have insignificant values in the resonance range. This is taken to mean that they are standing waves. In the high-frequency range the phase difference observed is appropriate for the propagation of sound waves. The coherence and phase spectra of (i) the continuum brightness with the line wing and core brightness of Fe i 6358.695, and (ii) the continuum, line wing and core brightness of Fe i 6358.695 with the velocity fluctuations in the same line, have been studied. The core brightness leads the continuum by 57° in the resonance range. The intensity oscillations in the line core lead the velocity oscillations by 93°.5. This is taken as an additional evidence for the existence of standing waves.

Notes: Abstract Poleward migration of the magnetic neutral line on the Sun has been calculated for the periods 1945–1950 and 1955–1981 using synoptic charts based on Hα observations. Epochs of sign reversal of the solar magnetic field at latitudes 50° to 90° have been determined for these periods. During the cycles 19 and 20 a threefold sign reversal took place in the northern hemisphere. During all the above cycles both the solar poles were of one polarity for a period ranging from 0.5 to 1 year. The poleward drift velocity of the magnetic neutral line varies from 6 to 29 m s−1 and seems to depend on the strength of the cycle.

Notes: Abstract We have made number counts of the bright points that populate the interior of the Ca II network in the solar chromosphere for four solar cycles. We find that the number of these fine structures during the solar maximum exceeds that during the minimum phase on an average by 30%. The contribution due to this excess number would need to be taken into account while explaining the variation in the Ca II K emission profiles of the integrated sunlight from the solar minimum to the maximum.

Notes: Abstract We have analyzed a large number of Caii H line profiles at the sites of the bright points in the interior of the network using a 35-min-long time sequence of spectra obtained at the Vacuum Tower Telescope (VTT) of the Sacramento Peak Observatory on a quiet regon of the solar disc and studied the dynamical processes associated with these structures. Our analysis shows that the profiles can be grouped into three classes in terms of their evolutionary behaviour. It is surmized that the differences in their behaviour are directly linked with the inner network photospheric magnetic points to which they have been observed to bear a spatial correspondence. The light curves of these bright points give the impression that the ‘main pulse’, which is the upward propagating disturbance carrying energy, throws the medium within the bright point into a resonant mode of oscillation that is seen as the follower pulses. The main pulse as well as the follower pulses have identical periods of intensity oscillations, with a mean value around 190 ± 20 s. We show that the energy transported by these main pulses at the sites of the bright points over the entire visible solar surface can account for a substantial fraction of the radiative loss from the quiet chromosphere, according to current models.

Notes: Abstract Emission lines of the Balmer series, D3 and H and K are reported present on a coronal spectrogram obtained at the March 7, 1970 eclipse. Arguments are presented to show that these could not have originated from scattering in the Earth's atmosphere and hence possibly have a coronal origin.

Notes: Abstract Closely spaced microphotometer tracings parallel to the dispersion of one excellent frame of a K-line time sequence have been utilized for a study of the nature of the K2v , K2R intensities in the case of the solar chromosphere. The frequency of occurrence of the categories of intensity ratio $${\rm I}_{{\text{K}}_{{\text{2}}V} } /{\rm I}_{{\text{K}}_{{\text{2}}R} }$$ are as follows: $${\rm I}_{{\text{K}}_{{\text{2}}V} } 〉 {\rm I}_{{\text{K}}_{{\text{2}}R} } = 45.3$$ per cent; $${\rm I}_{{\text{K}}_{{\text{2}}V} } = {\rm I}_{{\text{K}}_{{\text{2}}R} } = 4.7$$ per cent; $${\rm I}_{{\text{K}}_{{\text{2}}V} } 〈 {\rm I}_{{\text{K}}_{{\text{2}}R} } = 25$$ per cent; $${\rm I}_{{\text{K}}_{{\text{2}}R} } = 0 = 22.3$$ per cent; $${\rm I}_{{\text{K}}_{{\text{2}}V} } = 0 = 0.7$$ per cent. Two types of absorbing components are postulated to explain the pattern of observed K2v , k2R intensity ratios. One component with minor Doppler displacements acting on the normal K232 profile, where K2V 〉K2R , produces the cases K2v ≫ K2R , K2v = K2R , K2v 〈K2R . The other component arises from ‘dark condensations’ which are of size 3500 kms as seen in K2R . They have principally large down flowing velocities in the range 5–8 km/sec and are seen on K3 spectroheliograms with sizes of about 5000 kms, within the coarse network of emission. These ‘dark condensations’ give rise to the situation K2R = 0. K2-line widths are measured for all tracings where K2v , K2R are measurable simultaneously. The distribution curve of these widths is extremely sharp. The K2 emission source is identified with the bright fine mottles visible on the surface. Evidence for this interpretation comes from the study of auto-correlation functions of K2 intensity variations and the spacing between the bright fine mottles from both spectrograms and spectroheliograms. The life time of the fine mottling is 200 sec. The supergranular boundaries which constitute the coarse network come in two intensity classes. A low intensity network has the fine mottles as its principal contributor to the K emission. When the network is bright, the enhancement is caused by increased K emission due to the accumulation of magnetic fields at the supergranule boundary. The K2 widths of the low intensity supergranular boundary agree with the value found for the bright mottles. Those for the brighter network are lower than this value, similar to the K2 widths as seen in the active regions. It is concluded that bright fine mottling is responsible for the relation, found by Wilson and Bappu, between K emission line widths and absolute magnitudes of the stars. The paper discusses the solar cycle equivalents that stellar chromospheres can demonstrate and indicates a possible line of approach for successful detection of cyclic activity in stellar chromospheres.

Notes: Abstract Properties of a latitude zonal component of the large-scale solar magnetic field are analyzed on the basis of Hα charts for 1905–1982. Poleward migration of prominences is used to determine the time of reversal of the polar magnetic field for 1870–1905. It is shown that in each hemisphere the polar, middle latitude and equatorial zones of the predominant polarity of large-scale magnetic field can be detected by calculating the average latitude of prominence samples referred to one boundary of the large-scale magnetic field. The cases of a single and three-fold polar magnetic field reversal are investigated. It is shown that prominence samples referred to one boundary of the large-scale magnetic field do not have any regular equatorward drift. They manifest a poleward migration with a variable velocity up to 30 m s-1 depending on the phase of the cycle. The direction of migration is the same for both low-latitude and high-latitude zones. Two different time intervals of poleward migration are found. One lasts from the beginning of the cycle to the time of polar magnetic field reversal and the other lasts from the time of reversal to the time of minimum activity. The velocity of poleward migration of prominences during the first period is from 5 m s-1 to 30 m s-1 and the second period is devoid of regular latitude drift.