The WP1-related research encompasses empirical and theoretical research on the solar activity (solar eruptive activity, coronal holes and corotating interaction regions, evolution of active regions, solar rotation and solar 11-year activity cycle, long-term changes of the solar activity, etc.) and its influence on the state of the heliosphere and geospace, including the space weather forecasting.

T1.1. Eruptive processes in the solar atmosphere and variability of the solar wind

In T1.1 the role of ideal and resistive MHD processes is investigated in detail. The kink and torus instability, as well as to the physical relationship between CMEs and flares is studied, which includes the role of magnetic reconnection and the effect of self-inductivity on the evolution of the CME electric-current system. Nonlinear processes included in the formation and propagation of MHD shock waves (global-coronal and interplanetary) are being studied from empirical and theoretical point of view, including numerical simulations. The analysis of kinematics and dynamics of coronal and heliospheric propagation of CMEs is also performed. The central issue of the research is modelling in the context of space weather forecasting. Besides the CME-propagation modelling, the effects of active regions and equatorial coronal holes on the state of the background solar wind and interplanetary magnetic field is also studied, paying special attention to the evolutionary aspects of these phenomena.

T1.2. Geoeffectiveness of solar activity and space weather

The geoeffectiveness of CMEs is investigated in detail, with special emphasis on the forecasting based on the remote spaceborne white-light coronagraphic and coronal EUV observations of the dynamics of coronal eruptions. Similar studies are also performed for the corotating interaction regions (CIRs) associated with equatorial coronal holes (CHs). It is expected that the results achieved in the scope of this task will provide a better understanding of the CME-ICME connection and their space-weather effects, particularly GMSs and FDs. Furthermore, the results should provide early-warning procedures and forecasting of the GMS and FD level. Finally, the procedures developed in T1.2 will be set on the HO web page for a public usage.

T1.3. Long-term changes of solar activity and solar rotation

In Task 1.3, characteristics and evolution of the solar 11-year activity cycles is studied, including possibilities for the forecasting of the activity level of forthcoming cycles. This aspect of the research is extended also to the phenomenon of the long-term modulations of the 11-year solar-activity cycle and to the research related to the so called "space-climate" studies. Consequently this objective is closely related to the research of the Earth-climate effects (see WP2). For the analysis of the long term variations of solar activity cosmogenic C-14 and Be-10 data are used as proxies.

The research within WP2 considers investigation of the impact of the solar-modulated energetic particles flux on the Earth's atmosphere, the development of rigorous statistical examination methods based on the Monte Carlo approach, the influence of energetic particles within the global electric-current circuit on hypothesized changes in cloud microphysics and lightning phenomenon, and analysis of long-term ground-based measurements, to extend the potential analysis period to pre-satellite era. The research in the frame of WP2 is based on the analysis of numerous satellite and ground-based datasets. Results will be compared with theoretical mechanisms and models to test their relevance for the solar-terrestrial connection.

T2.1. Data compiling and development of statistical methods for the data analysis

In Task 2.1 the cosmic ray (CR) flux data archives are compiled to obtain a catalogue of all short-term events with largest deviations in CR flux (Forbush decreases, FDs and Ground Level Enhancements, GLEs). In addition, the diurnal temperatures (DTR) data are compiled as a proxy for cloud cover. Statistical examination methods based on the Monte Carlo approach are being developed and past statistical studies and their results are being reassessed. Lightning observations from ground and space borne observations related to short-term high-amplitude deviations in CR flux (FD & GLE events) and long-term variations in solar activity are being collected.

T2.2. Data analysis and interpretation

The uncertainties and errors in frequently used satellite cloud datasets are being quantified and the upper detection limit for ionization-induced changes in clouds is being determined, regarding the cloud data quality. This task includes the analysis of diurnal temperature data as a proxy for cloud cover, the synoptic weather data in order to examine the links between long-term solar activity and historical climate records, and lightning observations related to short-term high magnitude deviations in CR flux and long-term variations in solar activity. The Monte Carlo approach is adjusted/advanced to test the significance of current and past studies and long (centennial) timescale associations of climate variability to solar activity are being examined.

T2.3. Analysis of long-term ground-based climatologic measurements

This task is devoted to investigation of cloud properties theoretically optimal for the detection of an observable CR-cloud response, analysis and interpretation of aerosol data related to the CR induced ionization changes in the atmosphere, and search for possible changes in cloud microphysical properties connected to the global electric circuit mechanism. Various climate proxies (which extend more into the past) and parameters are employed to test the solar variability influence on climate and comparison of various theoretical mechanisms of solar influence on climate is preformed.

The main goal of WP3 is to achieve a better understanding of the magnetic activity of late-type stars with deep convective zones and to determine their XUV and plasma fluxes over wide range of ages. This will advance our comprehension of the magnetic past of the Sun by utilizing carefully selected solar analogues (with different ages and rotation-rates) that serve as proxies for the Sun over its main-sequence lifetime and the most powerful magnetic-field related solar/stellar eruptive processes.

T3.1. Preparations of observing capacities

The main goal of T3.1 is to prepare the HO 1-m telescope for the foreseen observations, i.e., to install the spectrograph and adjust hardware and software needed for the photometric and spectrographic use. HO 1-m Austro-Croatian telescope is used for long observing runs and to concentrate on brighter stars in order to ensure temporal cadence high enough for the observations. Spectra in the H-alpha and/or lithium spectral regions are recorded by the Shelyak eShell echelle spectrogtraph of the Gothard Astrophysical Obsarvatory, Lorand Eotvos University spectrograph attached to the HO 1-m telescope.

T3.2. Observations, data analysis and interpretation

The research activity will be focused on monitoring young pre-main sequence objects using HO 1-m telescope, in particular the T Tauri stars, representing youthful versions of the sun-like stars, with masses of a few tenths to a few times the mass of the Sun. On young stars prominences are large enough to be seen in disk-integrated H-alpha spectra. Stellar CMEs can be detected in spectra as extra blue shifted emission in the Balmer lines (H-alpha, H-beta, and H-gamma). Two types of observations are performed: photometric monitoring of selected stars in blue filters (U & B) and in the narrow band H-alpha filter, and spectrographic observations in the H-alpha and/or lithium spectral regions. Radial and rotational velocities, effective temperatures, and gravity of the observed objects are determined, and an estimate of the age and the chromospheric activity level is performed.

The research on stellar radiative processes mainly concerns empirical and theoretical aspects of the spectral and photometric variability of various types of variable stars. On the other hand, the research on radiative processes in the solar atmosphere embraces basic mechanisms of emission in the solar atmosphere, especially from the solar chromosphere, i.e., the continuum radiation (thermal and non-thermal bremsstrahlung) and the spectral line emission. The research in this field provides a better understanding of plasma instabilities and plasma emission mechanisms, comprehension of the physical state of solar and stellar atmospheres, as well as MHD and HD processes in circumstellar space.

T4.1. Spectroscopic and photometric properties of variable stars

The research related to the stellar radiative processes will be focused on various aspects of the physics of stellar atmospheres and binary stars. It is primarily based on continuous photometric monitoring of various stellar objects. The research encompasses spectroscopic and photometric properties of Be stars, Be shell stars and selected eclipsing binary stars, observations and interpretation of light variations of variable stars in galactic clusters and selected Ap stars, the light variability of pulsating red giants, and classic chemically-peculiar magnetic stars. In addition, the research will make use of the discovery and characterization of variable stars employing the LINEAR sky survey data base. The empirical aspect of T4.1 is based on both the archived and newly measured data provided mainly by Hvar Observatory 65-cm and 1-m telescopes, Ondrejov Observatory 2-m spectrographic telescope (Czech Republic), and the LINEAR sky survey data.

T4.2. Circumstellar and accretion-disc matter

The research within T4.2 considers the influence of the circumstellar matter to the radiation field of eclipsing binaries, the light variability of young stars due to their accretion disks, and numerical HD and MHD modelling of accretion and discs. The empirical aspect of T4.2 is based on both the archived and newly measured data provided mainly by Hvar Observatory 65-cm and 1-m telescopes, as well as the Ondrejov Observatory 2-m spectrographic telescope (Czech Republic).

T4.3. Investigation of the solar He I 1083 nm spectral line

The research in the scope of T4.3 concerns the formation of the He I 1083 nm spectral line in the solar atmosphere. This line provides a unique insight into both chromospheric and coronal plasma processes on the Sun. The archived full-disc solar images in the He I 1083 nm line obtained with the ChroTel instrument installed at the Vacuum Tower Telescope, German Solar Telescopes at Izana, Tenerife are used to study the evolution of coronal holes, evolution of CMEs and coronal waves, and enhanced helium absorption at the feet of coronal loops.

T4.4. Analysis of solar plasma with ALMA

The research within T4.4 is related to solar observations that will be performed with the new system of radio telescopes, ALMA (Atacama Large Millimeter/submillimeter Array). Solar measurements performed with ALMA are used to test models of the solar radiation at mm and sub-mm wavelengths relying on various radiation mechanisms applied to different models of the solar atmosphere. In addition, the coronal and chromospheric heating and centre-to-limb brightness variation of the Sun at mm and sub/mm wavelengths are also investigated.