Plasma Kinetic Theory

** Prof. Peter Yoon **

University of Maryland, USA

and

** Prof. Reinhard Schlickeiser**

Astrophysics

Kinetic theory of linear fluctuations in collision-free plasmas

Fluctuations are a generic feature of all plasmas with finite random velocities of the plasma particles. Consequently, their state variables such as number density, pressure and electromagnetic fields fluctuate in position and time around mean values. The quantitative determination of the strengths of these fluctuations is essential for understanding the origin of seed magnetic fields in the unmagnetized early intergalactic medium, the operation of the turbulent small-scale dynamo process from the seed velocity fluctuations, the formation of collisionless shock waves and the transport of relativistic charged particles in turbulent electromagnetic fields.

Unlike in the solar wind, where spacecraft instruments routinely measure the solar wind plasma parameters, for more distant astrophysical objects we have only very limited information on plasma fluctuations. For these systems kinetic plasma theory is the only way to calculate the properties of fluctuations. Because of their low gas densities, all fully and partially ionized non-stellar cosmic plasmas are collision-poor, so that fully kinetic plasma descriptions are necessary.

In-situ spacecraft solar wind turbulence observations have confirmed the presence of both weakly amplified/damped and weakly propagating fluctuations.

In this project we develop the fluctuation theory for magnetized plasmas for general values of the complex frequency using the existing fluctuation theory of unmagnetized plasmas. These magnetized plasmas harbour an ordered magnetic field, uniform on spatial scales which are large compared to the wavelengths of the fluctuations. Due to the high conductivity of cosmic plasmas, no large-scale stationary electric fields exist in these systems.

May 2015 - June 2015

Prof. Yoon has worked one month in May 2015 in Bochum lecturing twice on the theory of plasma fluctuations. His next stay is planned for May 2016.

Joint completed publications resulting from this project are:

Electromagnetic fluctuations in magnetized plasmas I: The rigorous relativistic kinetic theory; R. Schlickeiser, P. H. Yoon, 2015, Phys. of Plasmas 22, 072108.

Linear theory of low frequency magnetosonic instabilities in counterstreaming bi-Maxwellian plasmas; S. Vafin, R Schlickeiser, P. H. Yoon, 2015, Phys. of Plasmas 22, 092131.

Quasilinear saturation of the aperiodic ordinary mode streaming instability; A. Stockem, Novo, P. H. Yoon, M. Lazar, R. Schlickeiser, S. Poedts, J. Seough, 2015, Phys. of Plasmas 22, 092301.

Electromagnetic fluctuations in magnetized plasmas II: Extension of the theory for parallel wave vectors; R. Schlickeiser, A. Ganz, U. Kolberg, P. H. Yoon, 2015, Phys. of Plasmas 22, 102111.

2016

VIP Lectures at the chair:

11 May 2016: "Nonlinear Plasma Wave Interaction: Basic Methodology"

25 May 2016: "Nonlinear Plasma Wave Interaction: Applications"

The lectures were accompanied with discussions and interviews with doctoral researchers. The collaboration resulted in the following publications:

S. Vafin, R. Schlickeiser, P.H. Yoon (2016), ApJ 829, 41

S. Vafin, R. Schlickeiser, P.H. Yoon (2016), Phys. Plasmas 23, 052117

S. Vafin, R. Schlickeiser, P.H. Yoon (2016), Phys. Plasmas 23, 052106

P.H. Yoon, L.F. Ziebell, E.P. Kontar, R. Schlickeiser (2016), Phys. Rev. E 93, 033203

U. Kolberg, R. Schlickeiser, P.H. Yoon (2016), ApJ 817, 159

2017

Mercator Professor from DFG funding 01 April 2017- 31 May 2017

Lectures at the chair:

11 May 2017: "On the Isotropization of Solar Wind Protons"

24 May 2017: "Turbulent Equilibria in Space Plasmas"

The lectures were accompanied with discussions and interviews with doctoral researchers. The collaboration resulted in the following publications:

S. Kim, R. Schlickeiser, P.H. Yoon, R.A. Lopez, M. Lazar (2017), Plasma Phys. Control. Fusion 59, 125003

P.H. Yoon, R.A. Lopez, S. Vafin, S. Kim, R. Schlickeiser (2017), Plasma Phys. Control. Fusion 59, 095002

U. Kolberg, R. Schlickeiser, P.H. Yoon (2017), ApJ 844, 124