• C Venugopal

      Articles written in Journal of Earth System Science

    • Particle diffusion and adiabatic expansion of plasmoids

      M S Sindhu G Renuka C Venugopal

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      In this paper neutral point (coalescence) instability (NPI) of plasmoids (PMD) associated with tailward streaming O+, H+ and e particles and diffusion region (spatial extent and particle life time) are studied. Also, radial and pitch angle diffusion studies have been carried out in the near-earth region (10 and 11 RE during substorm onset. Our study revealed that coalescence instability is favoured by a heavier ion like O+ and the time required for a heavier ion to reach from one X point to an adjacent X point is minimum. Near an X type neutral line (diffusion region) ions spend a fairly long time and gain a significant amount of energy. Radial and pitch angle diffusion studies showed that higher energy particles are largely confined near the reconnection region (near-earth region) and lower energy particles are rapidly depleted from the near-earth region during substorm onset.

    • Ion acoustic instability of HPT particles, FAC density, anomalous resistivity and parallel electric field in the auroral region

      C S Jayasree G Renuka C Venugopal

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      During the magnetic storm of 21st March 1990, the DE-1 spacecraft encountered the auroral region at high invariant latitude at altitudes ranging from a few thousand kilometers in the ionosphere to many earth radii in the magnetosphere. The magnetic field perturbations interpretable as field aligned current (FAC) layers and the electrostatic turbulence possibly due to electrostatic ion acoustic instability driven by these currents are shown. The critical drift velocity of Hot Plasma Torus (HPT) electrons and the growth rate of ion acoustic wave as a function of electron to ion temperature ratio (Te/Ti) for low and high current densities and energy of HPT electrons are found out. The intense FAC destabilizes the ion acoustic wave and the resultant electrostatic turbulence creates an anomalous resistivity. The current driven resistivity produces parallel electric field and high power dissipation. The anomalous resistivityη, potential difference along the auroral field lines Vt|, intensity of electric field turbulenceEt| and power produced per unit volumeP are computed. It is found that the change in westward magnetic perturbation increasesJt|, η, Vt|, Et| andP. Hence HPT electrons are heated and accelerated due to power dissipation during magnetically active periods in the auroral region. Concerning, applications, such HPT electrons can be used in particle accelerators like electron ring accelerator, smokatron etc.

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