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The Atacama Large Millimeter/Submillimeter Array (ALMA) is a joint North American, European, and East Asian project that opens the mm-submm wavelength part of the electromagnetic spectrum for general astrophysical exploration, providing high-resolution imaging in frequency bands currently ranging from 84 GHz to 950 GHz (300 microns to 3 mm). It is located in the Atacama desert in northern Chile at an elevation of 5000 m. Despite being a general purpose instrument, provisions have been made to enable solar observations with ALMA. Radiation emitted at ALMA wavelengths originates mostly from the chromosphere, which plays an important role in the transport of matter and energy, and the in heating the outer layers of the solar atmosphere. Despite decades of research, the solar chromosphere remains a significant challenge: both to observe, owing to the complicated formation mechanisms of currently available diagnostics ; and to understand, as a result of the complex nature of the structure and dynamics of the chromosphere. ALMA has the potential to change the scene substantially as it serves as a nearly linear thermometer at high spatial and temporal resolution, enabling us to study the complex interaction of magnetic fields and shock waves and yet-to-be-discovered dynamical processes. Moreover, ALMA will play an important role in the study of energetic emissions associated with solar flares at sub-THz frequencies.

Atmospheric Imaging Assembly (AIA) images from the Solar Dynamics Observatory (SDO) were used to follow the motions of coronal bright points (CBPs) in the period 1 January - 19 May 2011 with a cadence of 10 minutes. This resulted in a data set of 80966 CBPs with measured lifetimes and mean velocities which were used in a random walk model to calculate the diffusion coefficient, D. The results show that D has a value of ≈260 km^2/s for CBPs with lifetime below 6 hours, decreasing to ≈170 km^2/s for lifetimes above 12 hours, with a mean value of ≈230 km^2/s.

The double solar telescope at the Hvar Observatory consists of two Carl Zeiss refractors, attached as one unit on a German parallax mounting. The photosphere telescope has an objective diameter of 217 mm and the chromosphere telescope has a diameter of 130 mm. It provides a valuable instrument to study rapid changes of chromospheric and photospheric features. Using a field of view of about 11 and 7 arcmin, it aims to produce high-resolution and high- cadence imaging of active regions on the Sun. Modern Pulnix TM- 4200GE 12-bit 4 megapixel CCD cameras allow to obtain time series with a cadence up to 30 images per minute. High-cadence chromosphere ground-based observations are an important tool to identify and study solar flares, filaments and other solar phenomena that are associated with coronal mass ejections and their propagation to the Earth. Hence these observations can be also used to improve space weather forecasts. This work has been supported by the ESF project PoKRet and the Croatian Science Foundation project SOLSTEL.

For the investigation of possible variations of the solar rotation, sunspots and sunspot groups are very often used as tracers, mainly because of the long term data sets available from various observatories. Until now, for the investigation of temporal variations of the solar rotation using sunspot groups as tracers, the Kanzelhoehe data set was analysed only for the period 1947-1981. Our aim is to provide a continuation of that previous investigation. For this reason we processed Kanzelhoehe sunspot drawings for solar cycles nos. 20-23 (manual method) and Kanzelhoehe white light images for solar cycle no. 24 (automatic method), covering almost the 41 year period, 1964 - 2015. When both methods for the heliographic positions determination have been used, it is important to compare them. Here we present the results of the manual versus automatic method comparison (differential rotation coefficients for both methods, differences in the identi cation of the sunspot groups, differences in the number of identi fied sunspot groups, etc.) performed for the year 2014.

The Sun has played a highly symbolic role in visual presentations throughout history. It overcomes the darkness and illuminates the whole world. It has often been associated and identified with the deity who sees everything that happens on Earth, therefore considered to be the eye of the world or God's eye. The sun is symbolically linked to Christ, the god Ra, Apollo or Helium but also with the ultimate symbol of life (eternal life). Fascination with the Sun and sunlight through art can be perceived by exploring various artistic media and expressions. Throughout art history this has resulted in the emergence of certain stylistic art directions (such as impressionism and expressionism). The Sun has been recognized as life, such as such as cells are in science, as it is the most important source of energy for life on Earth and it is a main driver of Earth's climate system. Modern solar telescopes revealed that the whole Sun's surface consists out of solar granules, a small (about 1000 km across) cellular features that last only for 10 to 20 minutes. The whole Sun is covered by about 4 million granules except in the areas covered by sunspots that prevent the development of convection currents. The cell is structural, functional and biological unit of all organisms as the smallest unit of life that can replicate independently, which is why cells are often called the "building blocks of life". In the past 10 years, significant efforts have been made towards developing more realistic in vitro cell culture models which can be “near to in vivo” conditions. Images of 3D cell cultures under the microscope show similarity with the structure of the Sun. The techniques and methods used to present the Sun or the cells have included the telescope, the microscope and artist's brush strokes. Visual reproductions by Vincent van Gogh, Turner, Rabuzin, Seder, Kožarić, and Monet as well as those from Egyptian, Greek and Christian mythology, are presented here together witht images of the Sun, Sun’s granules and cells growth in 3D format

Suvremeno istraživanje Sunca provodi se u čitavom spektru elektromagnetskog zračenja, nizom instrumenata smještenih kako na Zemlji tako i na floti svemirskih letjelica razmještenih širom Sunčevog sustava. Promatranje Sunca na valnim duljinama koje ne prolaze kroz Zemljinu atmosferu, kao i povećanje razlučivosti opažanja sa Zemlje, daju atraktivne snimke i detaljna mjerenja najbliže nam zvijezde i uvelike doprinose sve većem razumijevanju fizikalnih procesa na Suncu i njihovog utjecaja na heliosferu. Primjenom najsuvremenijih instrumenata, metoda mjerenja te analize podataka razotkrivamo tajne Sunčeve strukture i evolucije, njegovu magnetsku aktivnost i eruptivne procese, kao i Sunčev utjecaj na međuplanetarni prostor i Zemlju.

In present work we compared the measured and predicted amplitudes of the 24th solar cycle. The modified minimum–maximum method, belonging to the precursor class of methods, was applied to the smoothed monthly sunspot number values (the “old” data set, used before the change introduced on July 1st, 2015). The maximum of the 24th solar cycle occurred in April 2014 with an amplitude of R = 82 and this observed value is very close to our mean predicted value R = 83. The maximum was significantly weaker than in several previous cycles. Additionally, a curious solar activity minimum of 2008, between the solar cycles no. 23 and no. 24 was analysed, as well as the shape of the maximum profile. The maximum of the 24th solar cycle had a double-peak, the second one being higher than the first one. The obtained results represent a strong indication that the minimum–maximum method is a reliable tool for the solar cycle prediction, using data available already 3 years before the preceding minimum of solar activity.

We present here the results of the behaviour of the solar differential rotation during solar cycles no. 20 and no. 22, derived from Kanzelhöhe sunspot drawings (Kanzelhöhe Observatory for Solar and Environmental Research, University of Graz, Austria). The positions of sunspot groups were determined using a special software Sungrabber. Sunspot groups were identified with the help of the Greenwich Photoheliographic Results (GPR) and Debrecen Photoheliographic Data (DPD) databases, covering solar cycles no. 20 and no. 22, respectively. In order to calculate the sidereal angular rotation rate and subsequently solar rotation parameters A and B we used two procedures: a) daily motion of sunspot groups and b) linear least- square fit from the function CMD(t) for each tracer, where CMD denotes the Central Meridian Distance. The sample was limited to ±58◦ in CMD in order to avoid solar limb effects. We mainly investigated velocity patterns depending on the solar cycle phase and latitude.

One of the main aims of Hvar double solar telescope is to complement Kanzelhöhe Observatory (KSO) photosphere and chromosphere full-disc images by Hvar active-region high- resolution images using a field of view of about 11 and 7 arcmin. The new acquisition system with Pullnix TM-4200GE CCD cameras was applied to obtain the images of the active regions on the Sun with the cadence time of 15 seconds for chromospheric and 1 minute for photospheric telescope during the regular observation periods. In 2012, observations were performed during more than a 100 days with more than 125, 000 images of active regions in Hα and white light recorded. All data are stored to Hvar Observatory server (oh.geof.unizg.hr) and can be accessed over the internet.

The Atacama Large Mm/sub-mm array (ALMA) will be suitable for solar observations thanks to a specifically designed surface that prevents overheating of the telescope structure, and solar filters that attenuate the incoming signals to a suitable level. Preliminary results from the commissioning of solar observations are presented.

Postoji nekoliko različitih baza podataka koje sadrže informaciju o pozicijama sunčevih pjega i grupa sunčevih pjega i razlikuju se po formatu i preciznosti, npr. GPR (Greenwich Photoheliographic Results) i SOON/USAF/NOAA (Solar Optical Observing Network/United States Air Force/National Oceanic and atmosferic Administration). Cilj ovog rada jest provjeravanje preciznosti SOON/USAF/NOAA baze podataka i usporedba iste s GPR bazom podataka. U tu smo svrhu koristili treću bazu podataka, bazu podataka Kanzelhöhe opservatorija, kao mjerodavnu u usporedbi položaja grupa pjega.

Measured positions of sunspot groups that differ in format, precision and observing procedure are collected from various data sets: GPR (Greenwich Photoheliographic Results), SOON/USAF/NOAA (Solar Optical Observing Network/United States Air Force/National Oceanic and Atmospheric Administration), as well as from the Kodaikanal and Debrecen observatories. Kanzelhöhe and Kandilli Observatory currently provide the digitized sunspot drawings, from which the positions of selected sunspot groups are determined with a special software Sungrabber. The rotation velocities are calculated from the position data. The aim of this work is to compare and to check the precision of the mentioned data sets using the Kanzelhöhe Observatory data set as the reference basis of sunspot position measurements. The selected groups (about 40% consist of single sunspots Zürich types H and J) are from the years 1972 and 1993 belonging to similar declining phases of two solar activity cycles. The occurrence of some systematic differences of the sunspot group positions and rotation velocities suggests the need for a more detailed analysis of the data accumulation procedures.

There are several data sets containing information about the positions of sunspots and sunspot groups that differ in format and precision, e.g. GPR (Greenwich Photoheliographic Results) and SOON/USAF/NOAA (Solar Optical Observing Network/United States Air Force/National Oceanic and Atmosferic Administration). The aim of this paper is to check the precision of the SOON/USAF/NOAA data set and compare it with the GPR data set. For this purpose, we have used a third data set, the Kanzelhöhe Observatory data set, as a basis of sunspot position measurments comparison. The positions of selected sunspot groups in the digitized Solar Observatory Kanzelhöhe drawings were determined with a special software Sungrabber. The selected groups consisted mostly of single sunspots (Zürich types H and J) from the years 1972 and 1993 belonging to the similar phases of the solar activity cycles. The determined Kanzelhöhe sunspot group coordinates were compared with those from GPR for the year 1972 and SOON/USAF/NOAA for the year 1993. The rotation velocities calculated for sunspot groups observed at Kanzelhöhe were compared with the ones obtained from the two data sets mentioned above in the same observing periods. With the assumption of constant precision of Kanzelhöhe drawings, it was established that SOON/USAF/NOAA data are somewhat less precise than the GPR ones.

Solar activity proxies are needed for studies of the long term behaviour of the solar activity cycles. Cosmogenic isotopes like ^{;14};C are influenced also by geomagnetic field variations. We study the influence of such variations on the global behaviour of solar activity measured by methods of non linear dynamics.

The paper presents the first results of the observations of time evolution of the quiet solar corona brightenings obtained due to very rapid photography of the corona with full-disk EUV telescopes of the FET/TESIS instrument onboard the KORONA FOTON satellite. The measurements were performed simultaneously in the emission of the Fe IX / X 17.1 and Fe VIII 13.1 spectral lines with 10 second temporal cadence and spatial scale of 1.7 arc seconds within one hour. This test observation, carried out on 15 July 2009, was analyzed in order to determine whether this type of observation can be used to identify individual microevents in the solar corona heating that are above the tresholds of spatial and temporal resolutions of the observations of non-active regions in the solar atmosphere. For this purpose, a simple method was used involving cross-correlation of the plasma emission time evolution at different temperatures, each time from observations of identical elements. The results obtained are confronted with the expected observable manifestations of the corona heating via nanoflares. TESIS is a set of instruments for the Sun photography developed in the Lebedev Physics Institute of the Russian Academy of Sciences that was launched into orbit in January 2009.

Using a combined method, the strength and epochs for the next 24th solar cycle are predicted. This method consists of three parts: (1) the calculation of the asymmetry of the duration of the ascending and descending solar cycle parts, (2) the correlation of the relative sunspot numbers in and around solar activity minima and the following activity maxima and (3) the method of the autoregressive moving average model (ARMA) applied to the relative sunspot number data measured up to now. Our data sets comprise yearly, corrected yearly, monthly and smoothed monthly relative sunspot number values. A cross correlation analysis with different time lags in the activity minimum for the method (2) is performed. With these combined procedures we estimate a lower amplitude of the next solar maximum in comparison to the previous one.

Applying and combining different methods, the strength and epochs for the next 24th solar cycle are predicted. The combined method consists of the three parts: (i) the calculation of the asymmetry of the ascending and descending solar cycle phases, (ii) the correlation of the relative sunspot numbers in and around solar activity minima with the following activity maxima, and (iii) the method of the auto regressive moving average model (ARMA) applied to the relative sunspot number data measured up to now. The used data sets include yearly, corrected yearly, monthly and smoothed monthly relative sunspot number values. With these combined procedures a lower amplitude of the next solar activity maximum, in comparison with the previous one, is estimated.

The aim of the present analysis is to forecast the strength of the next solar maximum of the 24th cycle. We correlate the relative sunspot numbers in the epochs of solar activity minima and maxima. Using this method, the estimated relative sunspot number (also called the Wolf number) of the next solar maximum is in the range 67 - 81, i.e., about 40 % below the peak sunspot number of 121 for cycle No. 23.

Latitudinal variations and North--South asymmetry of the He~I 1083 nm line across the solar disc are investigated, based on 69 solar scans obtained during two observational campaigns in 1993 and 1995. In both time intervals the He~I 1083 nm line was observed in absorption. The ratio of average intensity in the line and the average intensity of the nearby quasi-continuum was calculated and cautiously used as a measure of the line bsorption and represented as a function of position on the solar disc. Results indicate a distinct dependence of the He~I 1083 nm average relative line intensity on the solar latitude, its North--South asymmetry and well pronounced differences for the two campaigns belonging to different solar cycle phases. The latitudinal dependence is analysed with and without discriminating quiet Sun and active regions. The observed behaviour (the latitudinal dependence and a North--South asymmetry) is to a large extent a consequence of the presence/absence of active regions. The differences found for the two observing campaigns are not only due to decreased solar activity in 1995 as compared to 1993, but also due to different and much more pronounced telluric water-vapour contamination during the second observing interval. Finally, in the Appendix we describe all He scans used here in more detail and compare the numbers of solar features identified in other spectral regions along the scans for the two observational campaigns.

At the wavelength of 8 mm absorption features (Low brightness Temperature Regions, LTRs) and emission features (High brightness Temperature Regions, HTRs) can be traced for determination of solar rotation. From earlier studies it is known that about two thirds of LTRs are associated with H$\alpha$ filaments. The goal of the present analysis is to determine the heights of these solar structures and their rotational velocities. We used the method for the simultaneous determination of the solar synodic rotation velocity and the height of tracers. The rotation velocities were determined by the linear least-square fit of their central meridian distances as a function of time. The mean value of the low brightness temperature regions' heights is about 45 600 km. The results of solar rotation determined by tracing LTRs and HTRs are mutually compared and also compared with the results using other tracers and methods. The method for the simultaneous determination of the solar synodic rotation velocity and the height of the tracers could be applied properly only on LTRs, since a wide distribution over latitudes and central meridian distances of a large data set is necessary, which was not available for HTRs. Observational findings that HTRs rotate systematically faster than LTRs and the possibility that they can be observed at and outside the solar limb are consistent with relatively high altitudes of HTRs. It was concluded that the radiation mechanism of HTRs is thermal bremsstrahlung, probably associated with flaring active regions.

The aim of the present analysis is to forecast the strength of the next solar maximum of the 24th cycle. We correlate the relative sunspot numbers in the epochs of solar activity minima and maxima. Using this method, the estimated relative sunspot number (also called the Wolf number) of the next solar maximum is in the range 67 - 81, i.e., about 40 % below the peak sunspot number of 121 for cycle No. 23.

Whole-disc full-resolution solar images taken in the extreme ultraviolet part of the spectrum (Fe XV line at 28.4 nm) with the EIT instrument on board the SOHO spacecraft were used to visually identify coronal bright points appropriate for solar rotation determination. From the time differences in successive tracer positions amounting to six hours the solar rotation velocity was determined tracing coronal bright points in images obtained in October and November 1999. The resulting parameters and profiles of the solar rotation are presented.

Full-disc full-resolution solar images obtained by the Extreme Ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory are used to analyse solar differential rotation by tracing coronal bright points. We applied an interactive and an improved automatic method of data reduction to process data obtained during the period 1998 - 2003 with the Fe XV filter (28.4 nm). Using the interactive method, the data obtained during 8 months of observation were reduced, while the automatic method was applied to analyse the whole 57-month period of observations, since the interactive method is much more time consuming than the automatic one. In the present work we especially focus on a possible relationship between the solar rotation (57 monthly values of the solar rotation parameters determined with the automatic method) and activity (relative sunspot numbers for the same months) during the maximum phase of the solar cycle 23.

Full-field full-resolution solar images obtained by the Extreme Ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory are used to analyse proper motions, velocity distributions, lifetimes, and diffusion coefficient of coronal bright points. The results obtained by the interactive method for three tracer subtypes (point-like structures, small loops, and small active regions) of coronal bright points for the period 4 June 1998 to 22 May 1999 are presented and compared. Distributions of meridional velocities, residual azimuthal velocities and velocities of proper motions are presented for the three tracer subtypes. Lifetimes up to 54 hours are found for 98% of all observed coronal bright points. Small active regions last on the average longer than point-like structures and small loops. The correlation between the absolute velocity of proper motion and lifetime is investigated and the mean free path (in the range from 3000 km to 15000 km) and the diffusion coefficient (approximately 200 km2/s) of coronal bright points are estimated. Finally, characteristics of the random walk process associated to the motions of coronal bright points are discussed in the Appendix.

Previous observations indicate that coronal holes generally appear as low brightness temperature regions in microwaves. However, within their borders local enhancements of radiation often occur. This is confirmed by comparing a full-disc solar image obtained at 37 GHz on 27 May 1993 with full-disc solar images obtained at various wavelengths. Microwave brightness temperatures of three coronal holes are determined and interpreted.

Various observations indicate that coronal holes generally appear as low brightness temperature regions (LTRs) in the centimeter and millimeter wavelength ranges. However, within their borders local enhancements of radiation, that is, high brightness temperature regions (HTRs), often occur. The theory behind the described behavior is not fully understood and therefore we analyze full-disk solar images obtained at a wavelength of 8 mm at Metsähovi Radio Observatory and compare them with data simultaneously taken in other wavelength ranges. The observational finding that the average brightness temperature of coronal holes is not much different from the quiet-Sun level (with localized deviations toward higher and lower intensities on the order of a few percent) is compared with theoretical models of the thermal bremsstrahlung radiation originating in the solar chromosphere, transition region, and corona. Special attention is devoted to the interpretation of the localized enhancements of radiation observed inside coronal holes at millimeter wavelengths. The main conclusion is that the most important contribution to the brightness temperature comes from an increased density in the transition region and low corona ( i.e., at the heights where the temperature is below 106 K). This can explain both the LTRs and HTRs associated with coronal holes.

Measurement of positions of the tracers on synoptic solar images and conversion to heliographic coordinates is a time-consuming procedure with different sources of errors. To make measurements faster and easier, the application "Sungrabber" was developed. The data of the measured heliographic coordinates are stored in text files which are linked to the related solar images, which allows also a fast and simple comparison of the measurements from different sources. Extension of the software is possible and therefore Sungrabber can be used for different purposes (e.g. determining the solar rotation rate, proper motions of the tracers on the Sun, etc.).

Three traveling disturbances recorded in the absorption line of Helium I at 10 830 Angstrom (He I), analogous to Halpha Moreton waves, are analyzed. The morphology and kinematics of the wavefronts are described in detail. The He I wave appears as an expanding arc of increased absorption roughly corresponding to the Halpha disturbance, although not as sharply defined. He I perturbations consist of a relatively uniform diffuse component and a patchy one that appears as enhanced absorption in He I mottles. It leads the Halpha front by some 20 Mm and can be followed to considerably larger distances than in Halpha observations. Behind the front stationary areas of reduced He I absorption develop, resembling EUV coronal dimming. The observed He I as well as the Halpha disturbances show a deceleration of the order of 100-1000 m s(-2). Moreover, in the event where Halpha, HeI, and EUV wavefronts are observed, all of them follow closely related kinematical curves, indicating that they are a consequence of a common disturbance. The analysis of spatial perturbation profiles indicates that He I disturbances consist of a forerunner and a main dip, the latter being cospatial with the Halpha disturbance. The properties and behavior of the wavefronts can be comprehended as a consequence of a fast-mode MHD coronal shock whose front is weakly inclined to the solar surface. The Halpha disturbance and the main He I dip are a consequence of the pressure jump in the corona behind the shock front. The He I forerunner might be caused by thermal conduction from the oblique shock segments ahead of the shock-chromosphere intersection, or by electron beams accelerated in the quasi-perpendicular section of the shock.

Stable recurrent sunspot groups from the Greenwich data set which were identified in at least two subsequent solar rotations were traced. The solar rotation was determined by the period method from the time difference of the two central meridian passages of each of the 327 identified groups. Sidereal rotation periods were calculated from the synodic ones by a seasonal-dependent procedure taking into account the details of the Earth's motion around the Sun. Growing recurrent sunspot groups rotate on the average faster than decaying recurrent sunspot groups, while sunspot groups of all types taken together rotate faster than both growing and decaying recurrent sunspot groups. A north-south rotational asymmetry and a cycle-dependence of rotational velocity of recurrent sunspot groups were analyzed. Positive rotation velocity deviations are larger, but less numerous than the negative ones. Signatures of torsional oscillations were not found analyzing the rotation velocity residual of recurrent sunspot groups as a function of the distance from the average latitude of activity.

Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse solar differential rotation by tracing coronal bright points. The results obtained with the interactive and the automatic method for the time period June 4, 1998 to May 22, 1999 are presented and compared. A possible north-south rotational asymmetry and differences in the rotation velocity curves for various subtypes of tracers are investigated

Opisan je postupak nalaženja sideričkog perioda iz mjerenja položaja objekata uzimajući u obzir utjecaj visine objekta

Characteristics of the bursts that occur almost contemporaneously at metric and millimetric wavelengths are presented. It is found that such events are rather rare. The correlated impulsive bursts observed at 237 MHz and at 37 GHz start in average almost simultaneously (time difference 0.3+(-)2.8 s). The first peaks at 37 GHz are delayed few seconds (3.1+(-)3.0 s) in respect to the 237 MHz peaks, whereas for the bursts maxima the delay is about 1s in average (1.0+(-)2.7 s). A weak correlation between peak fluxes at 37 GHz and 237 MHz is found. Spectral characteristics of these events indicate electron beams of extremely high energies. The association of the gradual bursts observed at 37 GHz and the phenomena at 237 MHz is not so clear, however in some cases a relationship was established.

A sample of 47 imp>(=) 1 flares whose H-alpha emission occured or protruded over umbrae of major sunspots (so called Z-flares) was studied to investigate characteristics of the associated dm/m radio, microwave and soft X-ray emission as the energy release site permeats into regions of strong magnetic fields. A close relation was found between the time of the microwave burst peak and the time of the "contact" (the time when the H-alpha emission protruded over or appeared in the sunspot umbra). The microwave bursts most often started several minutes before the contact and peaked at the time of the contact, or few minutes later. The H-alpha flares attained maximum close to, or few minutes after the contact and the microwave burst peak. The soft X-ray bursts were delayed more, attaining maximum 0-10 min after the contact. The onset of bursts in the dm/m wavelength range was associated with the period of growth or the peak of the microwave burst. Two categories of type III and IV bursts could be recognized: the ones starting some ten minutes before the microwave peak, and those that begin close to the microwave burst peak. It was found that type III bursts occur preferably in the events in which the microwave peak and the contact coincide. Type III bursts were not recorded in the cases when the microwave burst peaked before the contact. A possible relation between flares and noise storms was found in one third of the studied cases. The results are explained presuming that the contact reveals a permeation of the energy release process into a region of strong magnetic fields, where the process intensifies, and where from the accelerated particles have an access to magnetic field lines protruding to large coronal heights. Different manifestations of the energy release process occuring in various magnetic field topologies are considered to explain various time sequences of the events which have been observed during the studied flares.

Meridional motions of recurrent stable sunspot groups are analysed as a function of the distance from the average latitude of activity in each solar hemisphere. Results were obtained for two data subsets, consisting of recurrent sunspot groups decreasing and growing in area respectively, and are compared with the ones published in the literature. An interpretation of the results in the frame of the model of magnetic flux-transport on the Sun is discussed.

Procedures for finding the solar sidereal rotation rate, which are taking into account the height of tracers are described. The related algorithms for data reduction, including detailed corrections for the Earth's motion, are presented.