Supervisor: David Tsiklauri, Ph.D., Prof. RNDr. Jana Šafránková, DrSc., Prof. RNDr. Zdeněk Němeček, DrSc.
Status: Interrupted
Abstract:
There are two fundamentally different levels of modelling of plasma by means of (i) magnetohydrodynamic (MHD) i.e., fluid-like description and (ii) fully kinetic, for example Particle-In-Cell (PIC) or Vlasov, i.e., when individual plasma particle dynamics is resolved. The advantages of MHD modelling are that it can successfully model large volumes such as entire solar coronal active regions (ARs) or entire magnetosphere of Earth and its interaction with the solar wind. The disadvantage of MHD modelling is that whilst it gets the basic picture right, it ignores rich physics of wave-particle interactions, plasma micro-instabilities, fast magnetic reconnection and alike. The advantages of kinetic, PIC, modelling include ability to resolve full plasma-kinetic picture, i.e., rich diversity of wave-particle interactions, plasma micro-instabilities, fast magnetic reconnection. The major disadvantage of the kinetic modelling is that is can model only small volumes of space and for short time duration.
In these projects we aim to use MHD and PIC descriptions, namely state of the art 3D MHD and PIC numerical codes developed in Great Britain, to model exciting, unsolved problems in Solar and Space Physics.
Theme 1: Solar coronal active region (AR) dynamics. It is known that ARs heating contributes to 80% of coronal heating budget during solar activity cycle maximum. The major unsolved problem of mankind and indeed solar physics is the coronal heating problem. The problem is that current theories cannot explain why solar corona has a temperature of few million degrees Kelvin. about 200 times hotter than solar photosphere. We plan initiation of Solar coronal active region 3D modelling: i.e., Active Region (AR) heating challenge in analogy with Geo-Environmental Modelling (GEM) or Newton magnetic reconnection challenges. The goal is to identify the key mechanisms of AR magnetic energy release using MHD, multi-fluid and kinetic numerical codes with magnetic fields taken from ATST and SDO HMI magnetogram data and using 3D potential field extrapolations based on Green's function algorithm. This should give us an insight into wave dissipation versus reconnection coronal heating debate. Further details are described in Refs.[1--3]. The project will have extensive use of HPC facilities and is very data- and CPU- intensive.
Theme 2: Interaction of solar wind with Earth magnetosphere. There are several models which study how solar wind interacts with the Earth magnetic field. The key novelty is to include anomalous resistivity (i.e., spatially localized threshold based resistivity) which can facilitate fast magnetic reconnection. Hence provide realistic treatment of relevant physical processes.
Literature: [1] Tsiklauri, D., Missing pieces of the solar jigsaw puzzle, Astronomy #amp; Geophysics 50, 5, 5.32-5.38, 2009. [2] Boocock, C., Kusano, K., Tsiklauri, D., The effects of oscillations and collisions of emerging bipolar regions on the triggering of solar flares, Astrophys. J., 900, 1, id.65, 9 pp., 2020. [3] Boocock, C. M. and Tsiklauri, D., A simple and accurate potential magnetic field calculator for solar physics applications using staggered grids, Astron. Astrophys., 625, A47, 2019. [4] Tsiklauri, D., Three dimensional particle-in-cell simulation of particle acceleration by circularly polarised inertial Alfven waves in a transversely inhomogeneous plasma, Phys. Plasmas 19, 082903, 2012. [5] Tsiklauri, D., Particle acceleration by circularly and elliptically polarised dispersive Alfven waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes, Phys. Plasmas 18, 092903, 2011. [6] Tsiklauri D., J.-I. Sakai, S. Saito, Particle-In-Cell simulations of circularly polarised Alfven wave phase mixing: A new mechanism for electron acceleration in collisionless plasmas, Astron. Astrophys., 435, 1105-1113, 2005.