Thomas Neukirch: Research Interests

Research Topics (numbers refer to publication list)

• Solar Magnetic Fields [10, 11, 17, 18, 20-22, 25, 30, 31, 33-41, 47, 49-51, 55, 57, 58 ]
• Magnetic Reconnection [14, 16, 23, 26, 46, 52, 54, 60 ]
• Basic MHD aspects [ 12, 42, 45 ]
• Particle Acceleration [19, 61,62]
• Stability of Current Carrying Plasmas [9, 53]
• Earth's Magnetosphere and Ionosphere [ 13, 15, 27, 32, 43 ]
• Rotating Magnetospheres (Planets, Stars, Compact Objects) and Accretion Disks [ 3, 4, 5, 8, 24, 44, 48, 59 ]
• Structure formation in Galaxies and the Interstellar Medium [ 1, 2, 6, 7, 28, 29, 56 ]

My main research interest is the application of theoretical plasma physics methods to space and astrophysical plasma systems. This includes planetary magnetospheres, the solar atmosphere, magnetospheres of stars and compact objects etc. I have also done work on structure formation in galaxies and the interstellar medium.

A large part of my work focuses on plasma equilibria and their stability. I am especially interested in equilibrium sequences depending on external control parameters, bifurcation properties of plasma systems and other nonlinear aspects of equilibrium theory. This is important because

• The stationary states indicate the possible ground states of a system.
• Often space and astrophysical plasma systems exhibit periods of slow quasi-static evolution (energy accumulation) ending in a violent eruptive process (energy release); equilibrium sequences are very helpful to model this type of behavior.
• In general, equilibrium diagrams together with suitable criteria for stability can indicate when and how a plasma equilibrium looses its stability and time-dependent behavior is to be expected

Both analytical and numerical methods are used to solve the plasma equilibrium equations. This concept has been applied to systems like current sheets, rotating magnetospheres, solar magnetic arcades and galactic disks.

As said above equilibrium theory represents a first step towards the understanding of activity processes. The activity itself has to be modelled time-dependently. Usually this can only by done by the means of plasma simulations. Sometimes, however, even in that case analytical methods can be used. So far work has been done on interacting flux systems in the solar corona, the development of resistive instabilities in the ionosphere and on finding exact time-dependent solutions of the MHD equations.