• Vinod Krishan

      Articles written in Journal of Astrophysics and Astronomy

    • Optical interferometric observations of a transient event of 1986 March 13 in the coma of Comet Halley

      C. Debi Prasad T. Chandrasekhar J. N. Desai N. M. Ashok Vinod Krishan

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      During the recent apparition of Comet Halley in 1985-86 a transient ionic event in the form of a blob of H2 O+ emission was recorded in thecoma at ∼ 0h UT on 1986 March 13. Observations were carried out using a special IHW filter for H2 O+ emission at 7000 å/175 å, a 35 cm telescope, a Fabry-Perot interferometer and an image intensifier camera from Gurushikhar, Mt Abu. (24‡39’N,72‡ 47’E). A Fabry-Perot inter-ferogram in Ha taken a few minutes later at the same location reveals strong hydrogen emission (Hα) associated with the blob. The velocity field in the blob is structured with relative velocities upto ∼ 35km s−1. The event is interpreted as arising due to the sector boundary crossing of the interplanetary magnetic field by the comet

    • Editorial

      Ram Prasad Prajapati Vinod Krishan

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    • Different representations of a partially ionized plasma


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      It is economical to devise ways and means to simplify a multi-species particle system. A partially ionized plasma consisting of electrons, ions and neutral particles can be described as a three-fluid, a two-fluid or a single-fluid system by appropriately combining the dynamics of each of the species. Here, oneof the three possible two-fluid descriptions is discussed wherein the electron fluid and the neutral fluid are combined into one fluid, christened as ENe fluid, and treat the ions as the second fluid. It is found that the process of combining the electrons and the neutrals endows the neutrals with a negative electric charge.Hence, here is a plasma with heavy (with nearly the mass of the neutral particle) negatively charged particles along with the positively charged ions. After establishing the framework for the two-fluid, the ENe–ion, system, the characteristic electrostatic wave mode of this novel unmagnetized plasma is determined. A new mode of frequency $\omega=\omega_{\rm EN}$ emerges in the limit $(2\gamma_{\rm en}+ \gamma_{\rm ei})\gg \omega$, where $\gamma_{\rm en}$ and $\gamma_{\rm ei}$ are, respectively, theelectron–neutral and the electron–ion collision frequencies. This is identified as a collective mode of the ENe fluid, a counterpart of the electron plasma mode in a fully ionized plasma.

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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