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Engineering topics

Vranjes, J

Publications and source records attributed to Vranjes, J.

5 records

All sources NASA NTRS DOE OSTI

DOE OSTI2012

The stability of weakly ionized collisional dusty plasma in the presence of flow

The stability of weakly ionized and magnetized plasma in the presence of transverse (to the magnetic field) neutral wind is investigated in the present work. The collisional coupling of ambient background flow to the magnetized plasma gives rise to an electric field. In the presence of charged unmagnetized dust, electrostatic fluctuations in such plasma become unstable, with the growth rate dependent on the plasma thermal speed as well as on the dust charge and collision frequencies. This instability is similar to the Farley-Buneman instability. However, unlike Farley-Buneman, where the growth rate is directly dependent on the background flow, this dependence in the present case is only indirect. It is shown that this instability can grow over few seconds in the Earth's lower ionosphere and thus could play an important role in the structure formation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Dust acoustic mode in inhomogeneous plasma

A purely kinetic instability of the dust acoustic mode in inhomogeneous plasmas is discussed. In the presence of a magnetic field, electrons and ions may be magnetized while at the same time dust grains may remain un-magnetized. Although the dynamics of the light species is strongly affected by the magnetic field, the dust acoustic mode may still propagate in practically any direction. The inhomogeneity implies a source of free energy for an instability that develops through the diamagnetic drift effects of the magnetized species.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Dust acoustic instability driven by solar and stellar winds

A quantitative analysis is presented of the dust acoustic wave instability driven by the solar or stelar wind. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion plasma propagates through another quasi-neutral plasma which contains dust, electrons and ions. The cometary dusty plasma in the solar wind appears to be practically always unstable.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Current-less solar wind driven dust acoustic instability in cometary plasma

A quantitative analysis is presented of the dust acoustic wave instability driven by the solar and stellar winds. This is a current-less kinetic instability which develops in permeating plasmas, i.e.., when one quasi-neutral electron-ion wind plasma in its propagation penetrates through another quasi-neutral plasma which contains dust, electrons, and ions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Slow EIT waves as gravity modes

The EIT waves [named after the extreme-ultraviolet imaging telescope (EIT) onboard the solar and heliospheric observatory (SOHO)] are in the literature usually described as fast magneto-acoustic (FMA) modes. However, observations show that a large percentage of these events propagate with very slow speeds that may be as low as 20 km/s. This is far below the FMA wave speed which cannot be below the sound speed, the latter being typically larger than 10{sup 2} km/s in the corona. In the present study, it is shown that, to account for such low propagation speed, a different wave model should be used, based on the theory of gravity waves, both internal (IG) and surface (SG) ones. The gravity modes are physically completely different from the FMA mode, as they are essentially dispersive and in addition the IG wave is a transverse mode. Both the IG and the SG mode separately can provide proper propagation velocities in the whole low speed range.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗