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Subtle structure of streamers under conditions resembling those of Transient Luminous Events

Błęcki J. S., Mizerski K. A.

Archives of Mechanics

2018

Vol. 70, nr 6

535--550

The paper presents a brief review of the observational facts related to plasma filamentation in astrophysics and the subtle structures of plasma in Transient Luminous Events (TLE’s) and an analysis of the physical mechanism that could contribute to formation of filaments in plasma inside streamers. The values of physical parameters are assumed such as to resemble the physical conditions in streamers of the TLE’s. Estimates of the typical spatial scales of these structures and temporal characteristics of filament formation are given. The analysis concerns a non-magnetic mechanism based on a form of non-relativistic dissipative instability and the electron-nitrogen collisional 2Πg resonance. It is argued that the influence of the magnetic field is negligible at the leading order at least up to the altitudes of about 65–70 km. Under the conditions related to those in plasma inside the TLE’s, derived based on the current knowledge of physical parameters within the electric discharges, the identified dissipative-resonant instability is demonstrated to be the only/most vigorous linear instability developing in the system. It results in periodic plasma density distribution in the direction transverse to the electric field. The obtained time scales of the instability development are quick and proportional to the inverse of the ion-neutral collision frequency, 1/νi, whereas the proposed spatial scale of the density stripes/filaments is proportional to the electron temperature and inversely proportional to the speed of the discharge.

The need of using anomalous resistivity due to Lower Hybrid Instabilities in plasma-magnetic field interfaces

Bruzzone H., Bernal L.

Nukleonika

2001

Vol. 46, nr 2

59-61

Anomalous plasma can arise in dense plasmas as a consequence of the development resistivity of the Lower Hybrid drift Instability (LHI), which is triggered whenever the electron drift velocity becomes comparable to or larger than the thermal ion velocity. This effect was carefully evaluated for theta-pinch plasmas and later on used in the modelling of denser pinches, like Plasma Focus columns or Z-pinches, because of the diverging electron drift velocity expected in the classical equilibrium (uniform current, parabolic plasma density) pinch. Conceptually, the possibility of diverging drift velocities is far more a general situation than Z-pinches, and in this work we study it, in general, for plasma-magnetic field interfaces existing in other configurations, like that found in devices producing travelling current sheets (Plasma Focus devices, imploding pinches, etc.). We show that it is essential to account for this effect in steady state situations, and that it could be also important