The Apparent Behavior of Electron Density during an Alternating O/X-Mode Heating Experiment

We present the observations of the artificial ionospheric modification experiment of EISCAT on 18 October 2012 in Tromsø, Norway. When the pump of alternating O mode and X mode is switched on, the UHF radar observation shows some strong enhancements in electron density, ion lines and plasma lines. Based on some existing theories, we find the following: First, during the experiment, the frequency of plasma line (), ion line () and pump () matches = − 3 and = − 5 occasionally demonstrated that the cascade process occurred. Second, through quantitative calculation, we found that the O-mode component mixed in X-mode wave satisfies the thresholds of the parametric decay instability and the oscillation two-stream instability, from which we infer that the HF-induced plasma lines (HFPLs) and HF-enhanced ion lines (HFILs) observed in X-mode pulse could have been caused by the O-mode component mixed in X-mode wave. Third, the UHF radar observation shows some apparent enhancements over a wide altitude range (from approximately the reflection altitude to ~670 km) in electron density during X-mode pulse, which also does not, in fact, correspond to a true increase in electron density, but due to the enhancement in ion line or the enhancement in radar backscatter induced by some unknown mechanism.

Particle-in-Cell Simulations of High-Power THz Generator Based on the Collision of Strongly Focused Relativistic Electron Beams in Plasma

Based on particle-in-cell simulations, we propose to generate sub-nanosecond pulses of narrowband terahertz radiation with tens of MW power using unique properties of kiloampere relativistic (2 MeV) electron beams produced by linear induction accelerators. Due to small emittance of such beams, they can be focused into millimeter and sub-millimeter spots comparable in sizes with the wavelength of THz radiation. If such a beam is injected into a plasma, it becomes unstable against the two-stream instability and excites plasma oscillations that can be converted to electromagnetic waves at the plasma frequency and its harmonics. It is shown that several radiation mechanisms with high efficiency of power conversion (∼1%) come into play when the radial size of the beam–plasma system becomes comparable with the wavelength of the emitted waves.

Determinants of Corporate Cash Holdings in Textile Sector of Pakistan

This study analyzes the impact of tools used for cash holding in the textile sector of Pakistan for the period of 14 years (2005-2018). The tools consist of firm dimension, influence, capital expenditure, expansion opportunity, liquidity, cash stream and cash stream instability and extra expenditure. Unbalanced dynamic panel data is engaged for empirical estimation. For estimation of consistent result active panel information i-e Two-step scheme widespread process of moments is used. System generalized method of moments (GMM) design estimation reveals that compact dimension control, capital expenses, cash stream, cash stream instability and extra dummy affect cash holdings positively while liquidity and growth opportunities affect cash holdings negatively. Lagged cash is used as an instrumental variable and its positive implication (coefficient) reveal that the prior year reserve of cash have a significant impact on the current year and, suggesting these companies have a target level of cash. The academic implication indicates that larger companies in the textile sector retain more cash and easy access to diversify and advance sophisticated technology projects and furthermore will compete in the open market economy.