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manfred

Prof
Manfred
Hellberg
Bio
NASSP Lecturer Research Profile: Plasma is the dominant form of matter in the universe. An understanding of this state plays a fundamental role in astrophysics and space science, as well as in nuclear fusion research and a variety of industrial processes from chip manufacture to lighting, from metal cutting to metallurgy. An important aspect of plasma behaviour lies in collective effects. While simple plasmas (electrons and ions) support a variety of wave phenomena, multi-species and non-Maxwellian plasmas open up even more possibilities, with applications in both natural and laboratory plasmas. My research interests embrace linear and nonlinear wave studies in a variety of multi-species and non-Maxwellian plasmas. I have recently worked, inter alia, with collaborators in Durban, Ghent, Garching, Stockholm, and Bochum. Multi-ion plasmas and plasmas with two electron temperatures occur, for instance, in auroral zones, and other space situations. Both electromagnetic waves and nonlinear structures (e.g. solitons and double layers) in such plasmas are studied with a view to explaining satellite observations. Charged dust grains play an important role in planetary rings and cometary tails, and the presence of dust grains in a plasma has a strong influence on wave behaviour. Strongly-coupled dusty plasmas (complex plasmas), giving rise to plasma crystals, form an exciting new field that is being studied in microgravity experiments. One of our current interests involves the effects of dust grain self-gravitation on cosmic plasmas, as the Jeans instability couples with typical plasma modes. An important example of a non-Maxwellian plasma is one with an enhanced high energy tail. This may be modelled by a generalized Lorentzian distribution (a so-called "kappa distribution"). We are now applying our recently developed plasma dispersion function to waves in such magnetized space plasmas. Selected Publications: M. A. Hellberg, A computer simulation of the plasma resonance probe, Journal of Plasma Physics, 2, 395-435 (1967). I. M. A Gledhill and M. A Hellberg, Criteria governing ion-acoustic waves in two-ion plasmas, Journal of Plasma Physics 35, 75-96 (1986). M. A. Hellberg, S. Baboolal, R. L. Mace and R. Bharuthram, The role of self-consistency in double layer calculations IEEE Transactions on Plasma Science, 20, 695-700 (1992). R. L. Mace and M.A. Hellberg, Electron-acoustic and cyclotron-sound instabilities driven by field-aligned hot-electron streaming, Journal of Geophysical Research, 98A, 5881-5891 (1993).


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by Dr. Radut
manfred | National Astrophysics and Space Science Programme

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