The pantograph-catenary arc is a crucial factor that significantly impacts the effective current collection of high-speed railway pantograph-catenary systems. Investigating the electrical properties of this arc has engineering applications for enhancing the reliability and operational lifespan of such systems. The electrical characteristics of the pantograph-catenary arc in high-altitude areas with low gas pressure differ from those in low-altitude areas with atmospheric pressure across various aspects. In this article, we model the pantograph-catenary arc based on both Mayr arc and Schwarz arc mathematical models. By adjusting the dissipation power value, we investigate the arc voltage-time, arc conductance-time, and arc power-time characteristic curves under different altitudes, and establish the mechanism of low gas pressure on pantograph-catenary arc. A comparison between simulation results obtained using these two models reveals that Schwarz’s model is more suitable for modeling high-altitude pantograph-catenary arcs. The results indicate that, throughout the arcing process, the arc conductance of the pantograph-catenary system significantly decreases with increasing altitude, while the arc quenching capability of the pantograph-catenary system synchronously increases with altitude. This finding provides valuable insights for designing parameters related to pantograph-catenary systems in high-altitude regions worldwide.

The influence of the magnetic field shear is studied on the E × B (and/or gravitational) and the Current Convective Instabilities (CCI) occurring in the high‐latitude F layer ionosphere. It is shown that magnetic shear reduces the growth rate of these instabilities. The magnetic shear‐induced stabilization is more effective at the larger‐scale sizes (≥ tens of kilometers) while at the scintillation causing intermediate scale sizes (∼ a few kilometers), the growth rate remains largely unaffected. The eigenmode structure gets localized about a rational surface due to finite magnetic shear and has broken reflectional symmetry due to centroid shift of the mode by equilibrium parallel flow or current.

The effect of power-law dust size distribution and dust number density on the low frequency hall current instabilities have been studied in and above the equatorial electrojet altitudes using a linear fluid model consisting of electrons, ions and dust particles. The dispersion relation includes electron and ion drift perpendicular to the equilibrium uniform electric and magnetic field, mass and pressure of the charged species and collision between charged and neutral particles. The effect of dust size variation and dust number density on the instability have been investigated by varying the dust-plasma frequency in the dispersion relation. It has been found that in the region of the electrojet altitudes the variation of dust size for the case of broad dust size distribution and dust number density can substantially increase the growth rate and frequency of the instability. However, above the electrojet region where ions become weakly magnetized, the above two dust parameters have a negligible effect on the instability.The present analysis is applicable to the dusty meteor trail plasma of the ionospheric E-region.

Helical and chiral plasma structures are ubiquitous, especially in nuclear fusion devices and space plasmas. However, the spontaneous formation of helical structures has rarely been noticed in non-equilibrium cold plasma jets that have wide applications in biomedicine and material science. Recently the chiral plasma plume without any notable asymmetry has been discovered. Under the specific parameters of pulsed discharges, the plasma bullets that at the beginning propagated in the straight lines spontaneously turn into 3-D helical discharge trajectories. Here, the electromagnetic mechanism for the chiral plasma plumes is clarified by the numerical investigation of the 3-D electromagnetic field. According to the specific standing-wave mode with the periodic poloidal component in simulation, a type of plasma plume which shows the apparent poloidal rotation only at the periodic position of the tube and moves nearly in a straight line at other positions is revealed. These findings are relevant to the development of high-voltage active electromagnetic media for artificial 3-D optical meta-material devices and precise 3-D materials processing involving helical and chiral patterns in diverse fields.

The Farley-Buneman and Gradient Drift instabilities have been investigated using a fluid model, in a partially ionized dusty electrojet region in which dust and neutral particles constitute a uniform static background. The effects of dissociative electron-ion recombination and dust charge fluctuation on the instabilities also have been taken into account. The electron-ion dynamics are considered to derive the perturbed densities which further lead to the generalized dispersion relation. The dispersion relation describes the propagation of electrojet instabilities having frequency within dust ion acoustic range in a magnetized partially ionized dusty plasma. The dispersion relation is separately solved numerically and analytically for the two values of anisotropy parameters which correspond to the two different altitudes in the electrojet region. It is found that Gradient drift instability is unstable at a much longer wavelength as compared to Farley-Buneman instability both with or without dust. At lower altitudes(90 km) the increase of negative charge on dust decreases the threshold electron drift velocity for Farley-Buneman instability while it shows the opposite behavior at higher altitudes(100 km). A much lower electron drift velocity is required to excite the Gradient drift instability than the Farley-Buneman instability at both altitudes. The dissociative electron-ion recombination damps both modes much more than the dust charge fluctuation. A significant changes in threshold drift velocity is observed for the Farley-Buneman mode as compared to the Gradient Drift mode due to the two main damping mechanisms. The present analysis is applicable in the lower ionospheric electrojet region where meteoric ablation processes are dominant.