Suresh Chandra — Page 2

arXiv2007

Controversy on a dispersion relation for MHD waves

Kumar et al. (2006) obtained a fifth order polynomial in $ω$ for the dispersion relation and pointed out that the calculations preformed by Porter et al. (1994) and by Dwivedi & Pandey (2003) seem to be in error, as they obtained a sixth order polynomial. The energy equation of Dwivedi & Pandey (2003) was dimensionally wrong. Dwivedi & Pandey (2006) corrected the energy equation and still claimed that the dispersion relation must be a sixth order polynomial. The equations (11) $-$ (19) of Dwivedi & Pandey (2006) and the equations (24) $-$ (32) Kumar et al. (2006) are the same. This fact has been expressed by Kumar et al. (2006) themselves. Even then they tried to show this set of equations on one side gives the sixth order polynomial as they got; on the other side, the same set of equations gives the fifth order polynomial as Kumar et al. (2006) obtained. The situation appears to be non-scientific, as the system of equations is a linear one. These are simple algebraic equations where the variables are to be eliminated. However, it is a matter of surprise that by solving these equations, two scientific groups are getting polynomials of different degrees. In the present discussion, we have attempted to short out this discrepancy.

astro-ph↗

arXiv2003

Anomalous Absorption in Cyclic C$_3$H Radical

Yamamoto et al. (1987) reported the first detection of $c$-C$_3$H radical in {TMC-1} through its transition $2_{1 2} \to 1_{1 1}$ at 91.5 GHz. Mangum and Wootten (1990) detected $c$-C$_3$H through the transition $1_{1 0} \to 1_{1 1}$ at 14.8 GHz in 12 additional galactic objects. The column density of $c$-C$_3$H in the objects was estimated to be about one order of magnitude lower than that of the C$_3$H$_2$ which is ubiquitous in the galactic objects. The most probable production mechanism of both the C$_3$H and C$_3$H$_2$ in dark clouds is a common dissociation reaction of C$_3$H$_3^+$ ion (Adams & Smith, 1987). Although the $c$-C$_3$H is 0.8 eV less stable than its isomer $l$-C$_3$H, finding of comparable column densities of both the isomers in {TMC-1} supports the idea of comparable formation of both the $c$-C$_3$H and $l$-C$_3$H in the cosmic objects. Existence of a metaisomer in interstellar condition is a well known phenomenon in astronomy. We propose that $c$-C$_3$H may be identified through the transition $3_{3 1} \to 3_{3 0}$ at 3.4 GHz in absorption against the cosmic 2.7 K background in dense cosmic objects when no strong source is present in the background. When there is some strong source in the background of the object, peak of the absorption line decreases with the increase of the strength of the background source. However, at low densities, the intensity is found to increase. Hence, in low density regions, a background source can help in detection of the line. This absorption line may play an important role for identification of $c$-C$_3$H in a large number of cosmic objects. Similar absorption features are found for $c$-C$_3$D radical also.

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