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We study the effect that non-equilibrium chemistry in dynamical models of collapsing molecular cloud cores has on measurements of the magnetic field in these cores, the degree of ionization, and the mean molecular weight of ions. We find that OH and CN, usually used in Zeeman observations of the line-of-sight magnetic field, have an abundance that decreases toward the center of the core much faster than the density increases. As a result, Zeeman observations tend to sample the outer layers of the core and consistently underestimate the core magnetic field. The degree of ionization follows a complicated dependence on the number density at central densities up to 10^5 cm^{-3} for magnetic models and 10^6 cm^{-3} in non-magnetic models. At higher central densities the scaling approaches a power-law with a slope of -0.6 and a normalization which depends on the cosmic-ray ionization rate {zeta} and the temperature T as ({zeta}T)^1/2. The mean molecular weight of ions is systematically lower than the usually assumed value of 20 - 30, and, at high densities, approaches a value of 3 due to the asymptotic dominance of the H3+ ion. This significantly lower value implies that ambipolar diffusion operates faster.
We combine dynamical and non-equilibrium chemical modeling of evolving prestellar molecular cloud cores, and explore the evolution of molecular abundances in the contracting core. We model both magnetic cores, with varying degrees of initial magnetic
We study the abundance of CCH in prestellar cores both because of its role in the chemistry and because it is a potential probe of the magnetic field. We also consider the non-LTE behaviour of the N=1-0 and N=2-1 transitions of CCH and improve curren
Comparison of linewidths of spectral line profiles of ions and neutral molecules have been recently used to estimate the strength of the magnetic field in turbulent star-forming regions. However, the ion (HCO+) and neutral (HCN) species used in such
We have studied the effect of time-dependent ionization and recombination processes on magnetic reconnection in the solar corona. Petschek-type steady reconnection, in which model the magnetic energy is mainly converted at the slow-mode shocks, was a
The CS molecule is known to be absorbed onto dust in the cold and dense conditions, causing it to get significantly depleted in the central region of cores. This study is aimed to investigate the depletion of the CS molecule using the optically thin