The Interaction of the Solar Granulation with Small-Scale Solar Magnetic Fields

The Sun is the most important object for astrophysical research due to two premises. First of all it is the only star on which scientists can study ongoing physical processes in detail and spatially resolved. Moreover, the Sun provides the energy and radiation needed by our society. Yet, it is not only a friendly source of energy, but also sets up the space environment in which we are living. Sometimes this space can be harsh and dangerous (especially for satellite infrastructure and manned space- flight). Therefore it is important to investigate these changing conditions of space for which the term - space weather was coined. For an improved understanding of the Sun and the caused space-weather effects in depth knowledge of the solar atmosphere, which creates the space-weather, is indispensable. The atmosphere is structured due to the presence of magnetic fields which themselves are influenced by the underlying convective energy transport. But on large scales the magnetic fields are vice-versa influencing the granulation and the energy transport itself. Up to now these effects of magneto-convection and the detailed interaction of magnetic fields and granulation the visible pattern of the convection on the solar surface , especially on small-scales, are nevertheless not studied in full detail. Due to recent improvements in telescopes, as well as in numerical simulation schemes and computer technology, it is nowadays possible to produce highest spatially and temporally resolved data sets which allow such in depth studies of the interaction of the convection and small-scale magnetic fields and caused phenomena like magnetic bright points, waves, shocks, or solar tornadoes. The current project aims on providing new insights into this topic and for that purpose will use highest resolved data sets of the best currently available telescopes (Hinode, Sunrise, GREGOR). For that purpose 2D and 3D segmentation algorithms for the granulation pattern will be developed and applied. Furthermore, identification routines for small-scale magnetic fields will be applied on the data sets and the results for the granulation will be compared and correlated with the results for the magnetic fields. The obtained knowledge will facilitate an improved knowledge of the magneto- convection and may be the funding base for understanding the energy build up in the solar atmosphere which is finally responsible via flares and CMEs for the space weather.

Short Project Report for the general-public to FWF Stand Alone Project "The interaction of the solar granulation with small-scale solar magnetic fields" In the mentioned project the scientific goal was to obtain a better understanding of the interaction of the granulation with small-scale solar magnetic fields and its caused activity. The solar granulation is the visible surface pattern of the hot plasma rising from inside the Sun to the solar surface. It causes a permanently changing pattern on the surface similar to the pattern created in a pot of cooking water. The moving plasma takes existing magnetic field with the flows and sweeps it to the boundaries of the cell structures. In these boundaries dynamic interaction processes happen with the magnetic field. Among the two most important ones are the cancellation of magnetic fields if they are orientated in opposite direction. The experts talk hereby of so-called magnetic field reconnection, often leading to the creation of huge amounts of free energy which leads to heating as well as plasma up and outflows. For small-scale magnetic fields this can lead to the creation of spicules which are thin up-shooting columns of plasma. This process was witnessed in the project and described in as much details as never before. On the other hand, the interaction of the plasma with the magnetic field can lead to the creation of waves which can travel to the upper atmosphere and lead to a heating of the upper atmospheric layers. This was another point which was investigated in detail in the project. Finally the project was interested what is happening on long time scales with the small-scale magnetic fields as well as how the small-scale fields help in creating large scale structures within the solar atmosphere such as coronal holes which are areas in the solar atmosphere which is filled with less dense as well as cooler plasma. To perform all the before mentioned works the project team applied successfully for observational time at the largest European solar telescope. Moreover, they asked for the support of the Hinode spacecraft and the IRIS spacecraft operated by JAXA and NASA respective. With this suit of highest resolving state of the art telescopes the project team successfully performed the project goals.