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Vinod Krishan
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Volume 10 Issue 1 March 1989 pp 1-20
C. Debi Prasad T. Chandrasekhar J. N. Desai N. M. Ashok Vinod Krishan
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 -
Volume 43 All articles Published: 7 April 2022 Article ID 0019 Editorial
Ram Prasad Prajapati Vinod Krishan
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Volume 43 All articles Published: 23 July 2022 Article ID 0043
Different representations of a partially ionized plasma
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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Journal of Astrophysics and Astronomy
Volume 44, 2023
All articles
Continuous Article Publishing mode
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Journal of Astrophysics and Astronomy | News
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Continuous Article Publication
Posted on January 27, 2016Since 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.
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Editorial Note on Continuous Article Publication
Posted on July 25, 2019Click here for Editorial Note on CAP Mode
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