Plasma heating of small-scale loops in the solar atmosphere

• Applicant: Dr. Thomas Wiegelmann
• Subject Area: Astrophysics and Astronomy
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452856778

Loops are the fundamental structures that shape the magnetic skeleton of the solar atmosphere. The extreme-ultra-violet emission from plasma at a temperature of a million degrees in the quiet Sun is mostly confined to small-scale magnetic loops. Therefore, it is imperatively important to understand the physical mechanisms that heat the plasma in these loops. The main objective of the project is to further advance our understanding of the mechanisms of plasma heating in small-scale loops. Clusters of these small-scale loops are as coronal bright points (CBPs) known. We will investigate what is the role of eruptions in CBPs in the mass and energy transfer in the solar atmosphere and the solar wind. Although the past several years steps forward in this research domain were made, numerous fundamental open questions remain that require further comprehensive observational and theoretical modelling. Some of the open questions are: Which plasma-heating models of small-scale loop systems match best the observed morphology, evolution of plasma and magnetic field properties of small-scale loops? What is the possible interplay of magnetic reconnection and magneto-acoustic wave propagation in the heating of plasma confined in small-scale coronal magnetic loop structures? Are intensity variations in individual small-scale loops related to micro- or nanoflare heating, or are other physical mechanisms at play? In phase one of this project, we will derive the observational constraints of plasma-heating models of small-scale magnetic loops. The model constraints will be obtained through the comparison of model-predicted scaling of heating rates with loop lengths and magnetic fluxes with those determined observationally. Model constraints will also be obtained from the morphology and evolution of magnetic loops and their plasma properties. This will be done in emerging CBPs, which are formed from many loops as recorded in spectroscopic and imaging data, but also from the evolution and lifetime of the loops. In phase 2, we will conduct a statistical investigation of microflares and loop brightenings and their link to various heating processes. In phase 3, we will investigate CBP evolution and eruptions and their possible link to plumes and magnetic switchbacks both statistically and through case studies. To achieve the goals of the new project we will use state-of-the-art observations from space (IRIS, Hinode, Solar Orbiter, and Parker Solar Probe) and ground-based observatories (Fast Imaging Solar Spectrograph, Solar Swedish Telescope, and Daniel K. Inouye Solar Telescope). A state-of-the-art modelling including linear magneto-hydrostatic and non-linear force-free field extrapolations, magneto-frictional, and 3D radiative MHD will also be employed or compared with observations. The project will provide benchmarking knowledge on plasma heating of small-scale loops.

• DFG Programme: Research Grants