Browsing by Author "Hari Om Upadhyay"

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Cosmic ray ionization of lower Venus atmosphere
(Kluwer Academic Publishers, 1994) Hari Om Upadhyay; R.P. Singh; R.N. Singh
Cosmic ray particles passing through dense lower atmosphere of Venus decay giving rise to various charged and neutral particles. The flux and degradation of dominant cascade particles namely neutrinos and pions are computed and ionization contributions at lower altitudes are estimated. Using the height profile of pion flux, the muon flux is computed and used to estimate ionization at lower altitudes. It is shown that cosmic ray produced ionization descends to much lower altitudes intercepting the thickness of Venus cloud deck. The dynamical features of Venus cloud deck are used to allow the likely charging and charge separation processes resulting into cloud-to-cloud lightning discharges. © 1994 Kluwer Academic Publishers.
Detachment and instability of cometotail
(1993) Hari Om Upadhyay; R.P. Singh
The two types of comet tails (ion and dust) present different morphological structures whose origin has been reviewed in this paper. The change of magnetic field direction during sector boundary crossings is known to be the source of blob formation in cometotail regions. In this paper it is shown that in the absence of sector boundary changes, the predominant velocity shear on the lower and upper side of the cometotail may result into the instability and blob formation. The growth rate of the instability for different conditions of plasma tail has been studied. It is shown that the onset of instability depends on the shape and thickness of the ion cometotail. In the extended thick ion cometotails, the onset of Kelvin-Helmholtz (K-H) instability is less likely whereas in the thin and extended tail, the K-H instability mechanism is more effective in structuring the ion cometotails into blobs. © 1993.
Lightning-generated waves escaping out through plasma holes in the nightside Venus ionosphere
(Springer India, 1991) R.N. Singh; Hari Om Upadhyay
The plasma waves in the Venus ionosphere measured by OEFD aboard PVO are analysed. It is shown that these waves are generated by lightning like cloud-to-cloud discharges anywhere in the Venus ionosphere-surface waveguide. The theoretical minimum attenuation for waveguide mode propagation at 5.4 kHz is consistent with the maximum occurrence rate at this frequency. The lightning-generated and globally-propagating signals when encountered with plasma holes or ion-trough structures escape out partially and are detected by the OEFD aboard PVO. The 100 Hz signals can propagate upwards in whistler mode. Even the localized electrostatic mode waves would be converted into electromagnetic waves in the plasma holes and ion-trough regions. © 1991 Indian Academy of Sciences.