Final Report

1.     Report on research work
1.1    Information on the development of the research project
    Overall scientific concept and goals:
In accordance with the initially elaborated work program, the project aimed at investigation of the fundamental properties of flows with the various spatiotemporal scales in the solar atmosphere and the instability processes related to them. All these tasks have been approached from the perspective of the formation of the background flows and their role in the mentioned dynamical processes taking into account effects of plasma partial ionization. The context was based on three research pillars announced in the initial work program and supported by the observational results: (i) heat production in the lower atmosphere originating from electric currents dissipation due to ion neutral collisions, (ii) partial ionization in flow instabilities of complex magnetic and dynamic objects (bright points, jets, spicules etc.) and (iii) estimation of the effects of background flows in instabilities of coronal magnetic structures. The investigations comprised both observational and modeling efforts.
(i) The observational data analysis included the long-term campaign of the data processing, image pattern recognition, parameter measurement and recording efforts related to SDO and solar decametre radio observational data. These efforts allowed a systematic identification of the small and large-scale flow patterns and understanding relevance of the effects of the partial ionization in those processes. The results achieved during the observational studies led to a number of published and ongoing observational papers (Bagashvil. 2017a,b, Philishvili et al. 2017a,b, Dumbadze et al. 2017a,b, Tsinamdzgvrishvili et al. 2017). All these works concern the observational study of small scale flows in flaring magnetic loops, coronal bright points, and jets (the precursors of jets discovered), as well as oscillations of active regions, statistical distribution and dynamics of the coronal holes. Additionally, the spectroscopic study of the spicule oscillations (Khutsishvili et al. 2017, Khutsishvili et al. 2014) and the chromospheric jets dynamics (Kuridze et al. 2017) was made. Other investigations (Gurgenashvili et al. 2016, Mghebrishvili et al 2015, Vashalomidze et al 2015) were related to the Rieger type periodicities of the solar activity, coronal tornado dynamics, and coronal rains. Moreover, the solar radio observations were analysed in collaboration with Institute of Radio Astrophysics, Kharkov, Ukraine (Dididze et al. 2017, Melnik et al. 2014, Plyaev et al. 2017).  
(ii) The theoretical/numerical modeling part consisted of a combination of analytical and numerical methodologies, with more pronounced accent taken on the theoretical derivations. The studies were performed by means of a combined mathematical framework related to the partial ionization and background flow effects. Especially we concerned on the novel polytropic 1D model of the solar wind (Shergelashvili et al. 2017a), nonmodal (nonequilibrium) model of the coronal jets and their precursors (Shergelashvili et al. 2017b), theory of periodic and aperiodic flows in the flaring loops (Shergelashvili et al. 2017c), mechanisms of excitation and spectrum formation of the active region oscillations (Shergelashvili et al. 2017d), properties of the Kelvin-Helmholtz instability in chromospheric jets (Kuridze et al. 2017)  and solar wind (Ismayli et al. 2017a,b), as well as numerical simulations of spicules (Kuzma et al. 2017) and twisted magnetic structures (Murawski et al. 2016). Most of the above mentioned studies include also the aspects of the plasma partial ionization. In addition, shear flow driven instabilities were studied with the 16-moment MHD (Uchava et al. 2014, Ismayli et al. 2017a,b). Besides of that, further theoretical study of dynamical and wave phenomena in astrophysical partially ionized plasmas has been performed in collaboration with the project international partners(Ballester et al. 2017).
    Was there a change in research orientation between the start and the end of the project? If so, what form did the change take, what effect did it have on the work?
The research strategy initially described in the proposal has been extended towards more extensive observational data analysis. The strategy, in that respect, is done with the motto: ‘we develop theoretical models of the phenomena that we actually observe’. With this approach we dedicated a significant part of the efforts to the observational studies of the physical phenomena of interest while revealing core fundamental processes and performing their ranking with respect to relevance. As a result, we were able to develop an appropriate framework of data for the development of the respective theoretical models in a rather straightforward manner.  
1.2    Most important results and brief description of their significance (main points)
    Contribution to the advancement of the field
The developed approaches, analysis methods, and obtained results open a new dimension in studies of the nature of small and large-scale flow patterns in the solar atmosphere and consequent physical processes of the energy release and transport. We introduced the procedure of the observational and analytical patterning of flows. Both observational and theoretical efforts mentioned above are consistent and follow the structure of the project methodological background and sequence of particular tasks. Further, we give a detailed description of particular results achieved within the project and show a connection with methods and tasks in each case:
(i) Small-scale flow patterns and related processes: There is an enormous number of small-scale flows naturally related energy transport processes that appear in the solar atmosphere. This list includes the motions at the chromospheric level (evaporation), collimated flow patterns in spicules, coronal and active region jets etc. The complimentary issue here is the role of the ion-neutral collision effects in the energetic supply of this complex plasma dynamics. In particular, the hot plasma inflows detected in coronal loops during the ascending phase of solar flare might result in appearance of the bright plasma blobs in the intensity variations which sometimes show a quasi-periodic behavior. The latter were interpreted as a certain high harmonic of a standing longitudinal oscillation driven by the flow in a thermodynamically non-equilibrium background. As another possible interpretation we propose that the observed bright blobs could be a sign of a strongly twisted coronal loop that is kink unstable (Philishvili et al. 2017a). Further, we continued the analysis of the same flare and detected 17 small-scale aperiodic flows. Their characteristic velocities and loop temperatures were determined (Philishvili et al. 2017b). This study relates with the project methodology (indicated further on as M) 3.3 and tasks (T) 1 and 3. Based on the observational evidence, we have developed a unified analytical model of the periodic and aperiodic flow patterns driven by the spontaneous external pressure gradients and hot plasma inflows in the loop anchored in the partially ionized chromosphere.  We investigate here the hypothesis, whether the dissipation of electric currents in the partially ionized plasma can be the reason for sporadic hot plasma inflows in the coronal structures. The analytical examples of the observed patterns are obtained (Shergelashvili et al. 2017a). This study relates with M 3.1; T 1,3. As a continuation of this work, we started with a numerical model of the spectrum of eigenmodes for such spuriously driven loops using the ledaflow code (M 3.2; T 1, 3). Additionally, we observationally studied the coronal rain falls (Vashalomidze et al. 2015), as another example of flows in the magnetic loops (M 3.3; T 3).
    Regarding the study of coronal bright points and related jets, while focusing on triggering mechanism of jets we discovered that specific quasi-periodic variations of the mean brightening in bright points usually appear as a precursor of the jet. Therefore, we claimed that MHD wave and oscillatory processes are involved in the triggering of the coronal jets (Bagashvili et al. 2017a). Further investigation of the pattern of meridional migration and long-term dynamics of coronal bright points enabled identifying of other long period oscillations (Tsinamdzgvrishvili et al. 2017). These studies relate with M 3.3; T 1, 3. The corresponding theoretical model has been developed, that is based on the earlier theoretical works (Shergelashvili et al. 2006, 2007). The core idea is that the bright points represent hot closed magnetic loops emerged within the coronal holes, that can be driven by the flows coming from the partially ionized chromosphere and shear flows at the edge of the loop. Both these effects provide a favorable ground for the shear flow driven wave instabilities and couplings (Shergelashvili et al. 2017b). Altogether this opened an ongoing work regarding the reformulation of the developed (and tested for bright points) nonmodal and nonequilibrium framework for the case of spicules, involving both multi-fluid partially ionized plasma and also 16-moment MHD formalism (Uchava et al. 2014). These studies relate with M 3.1; T 1, 2, 3.  
    Along with that, combined theoretical, numerical and observational studies of the Kelvin-Helmholtz instability in chromospheric jets (Kuridze et al. 2017), according to M 3.1, 3.3; T 3, has been performed. Analytical solutions of the dispersion equation indicate that this type of jets are unstable to Kelvin–Helmholtz instability with a very short (few seconds) instability growth time. Analysis of the Hα line profiles shows that the detected structures have the increased line widths as compared to the background. The methodology for simulation of spectral lines absorption features has been further elaborated in cooperation with another project and applied for the interpretation of exoplanetary transiting spectra (Khodachenko et al. 2015, 2017, Shaikhislamov et al. 2016). The numerical simulations of spicules (Kuzma et al. 2017) reveal that the initial velocity pulse steepens to a shock that propagates upward into the corona. The chromospheric cold and dense plasma follows the shock and enters the corona with the mean speed of 20–25 km/s. We found that the effect of the non-adiabatic terms on spicule evolution is nevertheless small. Besides of that, using the spectroscopic observations we studied oscillations in spicules (Khutsishvili et al. 2017, Khutsishvili et al. 2014). Numerically obtained properties of the Kelvin–Helmholtz instability confirm the analytical predictions for the instability occurrence (Murawski et al. 2016). These group of studies relates with M 3.2; 3.3; T 2, 3.
(ii) Large-scale flow patterns and related processes: The challenging question here (also one of the goals of the forthcoming Solar Orbiter mission) is how the processes close to the sun are connected with the outer profiles of the wind and CMEs. Indeed the large-scale wind flows transport the energy generated in the chromosphere and corona to the outer heliosphere. The project aim was to understand the statistical distribution of large magnetic structures on the disk and their sidereal rotation rates.  For this purpose, in-line with M 3.3 and T 3, we studied the long-term synoptic statistical distribution of the coronal holes and consequently the associated open magnetic field structures (Bagashvili et al. 2017b, Chargeishvili et al. 2017, Oghrapishvili et al. 2017). We analysed 529 type III radio bursts before, during, and after the CMEs and detected local density radial profiles. The comparison reveals the natural difference between the density profiles in a quasi-stationary solar wind and during the propagating transient CME phenomena (Dididze et al. 2017). There were also complementary works on the radio data analysis (Plyaev et al. 2017, Melnik et al. 2014). This research activity relates with M 3.3 and T 3.
    Based on the considered observational facts and with regard to M 3.1 and T 3 of the project, we developed a novel 1D polytropic model of the solar wind which admits a wide class of the analytic solutions (Shergelashvili et al. 2017c). The novel solutions show good agreement with the synoptic concept of the coronal hole and streamer structures, the results of radio observations, as well as with issues linked to the effects of plasma partial ionization.
    We also observed the long period (of the order of several hours) oscillation patterns of the active regions and analyzed their spectra (Dumbadze et al. 2017a,b). These oscillations can be interpreted as a process that carries the information about the solar internal magnetic field structure and used as a diagnostic tool for the latter. A dedicated model for the diagnostics of magnetic field in deep interior has been developed, that deals with the excitation and spectrum formation of the active region long period oscillation patterns (Shergelashvili et al. 2017d). Along with that, an alternative method for the magnetic field probing (Gurgenashvili et al. 2016), based on the variability of the Rieger type periodicity on the Sun has been proposed. In course of this study, the long period oscillations were considered as energy sources, pumping energy into the photospheric/chromospheric partially ionized plasmas. This work relates with M 3.1, 3.3 and T 1, 3.
    Additionally, within M 3.1, 3.3 and T 3, we investigated solar tornados, that reveal the strong connection with the CME formation (Mghebrishvili et al. 2015) and addressed the theory of the Kelvin–Helmholtz instability in the solar wind with the 16-moment MHD formalism (Ismaylli et al 2016, 2017).
    Breaking of new scientific/scholarly ground
(i) Detection of the precursors of coronal jets.
(ii) Development of the updated observationally consistent solar wind model.
    Most important hypotheses / research questions developed
(i) establishing of a notion system for the small/large scale flow patterns and their statistical or artificial intelligence models.
(ii) introducing of the notion of the precursor of the coronal jets
    Development of new methods
(i) the method of mapping of SDO HMI images of active regions into elliptic shape.
(ii) the method for analytic solution for the solar wind.
    Relevance for other areas of science
(i) Statistical models for the solar chromospheric and coronal heating due to the presence of neutrals in the magnetic structures and solar weather studies.
(ii) Modelling of the dynamic atmospheres and winds on the other stars and interaction with their planetary systems.
(iii) Development of the libraries of the flow patterns for the supervised machine learning and other statistical modeling with the implications to space weather studies.  
1.3    Information on the execution of the project, use of available funds and (where appropriate) any changes to the original project plan relating to the following:
    Duration: The project was prolonged (cost-neutral) for two months to complete papers on the obtained results.
    Use of personnel
Dr. Shergelashvili B. M (01.08.2014 – 30.09.2017) – the main co-worker, all tasks;
Dr. Zaquarashvili T. (01.02.2017 – 30.04.2017) – contribution mainly to Task 2 and consulting support in other tasks.
    Major items of equipment purchased: -- NO
    Other significant deviations. -- NO
2.     Personnel development – Importance of the project for the research careers of those involved (incl. the project leader)

The project provided a nice opportunity for its team members (Drs. Shergelashvili B. M, Zaqarashvili T., and Khodachenko M.L.) to intensify international research collaboration links with international partners from Ilia State University, Georgia, Ruhr University Bochum and University of Siegen (both Germany) and K.U. Leuven, Belgium. During the project time Khodachenko, M.L. successfully passed the evaluation at the Austrian Academy of Sciences and got a permanent job position there.
        
3.     Effects of the project beyond the scientific field
    Brief comments on specific effects beyond the research field
    (A)    Besides of the research work for the project, its participants took part in the RTD consortia of several European FP7/H2020 projects:
    - IMPEx (http://impex-fp7.oeaw.ac.at Integrated Medium for Planetary Exploration)
- SOLSPANET (http://solspanet.eu/solspanet Solar & Space Weather Network)
    (B)    The investigations, performed within the project gave rise to several research directions, which will be continued (see III Attachments Sect 7.1). The results obtained allowed formulation of the material for more than one follow up projects at national and international levels.
4.     Other important aspects
    Project-related participation in national & international conferences
1.    Khodachenko, M.L. Invited review lecture: “Exoplanetary Magnetic Fields and Magnetospheres: Atmosphere Mass-loss and Magnetospheric Protection” on Phys. Colloquium at the Dept of Phys., Univ. of Warwick, UK, Oct. 2014
2.    Khodachenko, M.L., Exoplanets – frontiers of modern planetology, Invited lecture series on School of Modern Astrophysics (SOMA), at Moscow Inst. Of Phys. And Techn., Dolgoprudny, Russia, June-July, 2016
3.    Shergelashvili B.M., Solar and space weather results, and challenges. Invited Presentation on Summer school on Solar and Space Physics, 25th -31st May 2015, Baku, Azerbaijan.
4.    Shergelashvili B.M., Background flow related processes on the sun. Invited Presentation on Solar Physics Conference, 2nd – 9th July 2015, Baku, Azerbaijan.
5.    Shergelashvili B.M., Solar and space weather results, and challenges. Poster presentation on ESPM-15, 4th - 9th September 2017, Budapest, Hungary.
6.    Shergelashvili B.M., Model of the solar polytrophic flow patterns.  Presentation on Our mysterious Sun: magnetic coupling between solar interior and atmosphere, 25th -29th September 2017, Tbilisi, Georgia.

    Organisation of symposiums & conferences:
Drs. Zaqarashvili T.V. and Shergelashvili B.M. were in organizing committees of Our mysterious Sun: magnetic coupling between solar interior and atmosphere, 25th -29th September 2017, Tbilisi, Georgia.
    Other aspects: The project team members served as referees in Astron. & Astrophys.; Journal of Geophysical Research (JGR); Astrophys. Journ.; Solar Phys.; MNRAS, Physics of Plasmas.
In 2017 Dr. Khodachenko M.L. served as ERC Advanced Grants remote reviewer, for the European Research Council, EC.
References used in the text:
Shergelashvili B.M. et al. 2007, Phys. Review E, Vol. 76, 046404
Shergelashvili B.M. et al. 2006, ApJ Letters, 642, L73 –L76
All other references are the project papers listed in attachments.