Energy transport in the solar atmosphere: background flows

The fundamental goal of solar and space physics research is to explore and to understand the activity of the Sun and the complex effects of that activity on the interplanetary environment and the planets of the solar system. Space-based observations, and advanced multi-dimensional models seem to have captured the essentials of solar activity and its influence on the solar system. However, many uncertainties and unknowns still remain. The problem of chromospheric/coronal heating still is far from the solution. Along with that the forecasting of solar flares/CMEs also appears an essential task for developing of space weather predictions. The complete understanding of those processes needs to increase the observationalheoretical efforts, and in particular the intellectual inquiry into fundamental processes of magnetized plasmas. The present project is particularly aimed to study the effects of background flow in the energy transport and release processes in the solar chromosphere and corona. The main research directions (project tasks) of the project are: 1) Instability of the flow of neutral atoms across the magnetic field (Farley-Buneman instability) in the solar lower atmosphere taking into account the gravity, 2) shear flow instabilities and phase mixing in solar spicules taking into account partially ionized plasma effects and 3) role of background flow in the instability of coronal magnetic structures. The novelty of the proposed research consists in consideration of the influence of background flows on the energy transport and release processes taking into account the partial ionization of plasma in the solar atmosphere. Recent observations of various flows and jets indicate their enhanced role in the shaping of plasma parameters and energy balance in the whole solar atmosphere. Self consistent consideration of background flows in MHD modeling may play an important role for understanding of the energy transport and dissipation processes. The expected results of this project will increase our knowledge about the mechanisms of chromospheric/coronal heating and enable further step in development of Solar Weather, i.e. forecasting the solar flares/CMEs, which becomes complementary to the Space Weather. This stimulates our work on the generalization of the existing theoretical approaches for description of processes in the partially ionized solar plasmas and makes the proposed research very timely for the modern solar physics. Theoretical studies proposed in the project will be combined with the observational data analysis and interpretation.

In accordance with the initially elaborated work program, the project aimed at investigation of fundamental properties of flows with the various spatiotemporal scales in the solar atmosphere and the instability processes related to them. The investigations comprised the aspects of the effects related to the partial ionization of plasmas and MHD wave amplification and dissipation based heat sources or wave instabilities. As additional physical framework, for the case of strongly magnetized plasmas, we worked in the 16-moment MHD. All these tasks have been approached from the perspective of the background flow formation and dynamical processes that are believed to have prominent contribution into the maintenance of the energy balance in the solar atmosphere. More concretely the energy transport from the photosphere upwards, energy release and physical mechanisms for solar wind and flares/CMEs, have been realized as central fundamental problems and actual tasks of the project. 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 allowed a systematic identification of the small and large-scale flow patterns, gathering of the information about the physical mechanisms of their origin and involvement of these flow patterns into the several kind of instability processes with the appropriate indications on the links with the effects of the chromospheric, solar coronal and solar wind processes, also issues related with the partial ionization. In the latter respect, the aim was to reveal observationally the specific examples of the dynamic processes, their spatiotemporal topology and the characteristic physical conditions of their relevance in further theoretical modelling.(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 based on the observationally detected processes of the energy release and transport through a different type of flow patterns observed by us. Several analytical and numerical models have been developed. They concern further establishment of the notion of the flow patterns at various spatiotemporal scales, by means of a combined mathematical framework related to the partial ionization and background flow effects.