Bimodal instability dynamics in nonthermal complex tridust astroclouds towards structure formation

¹ Department of Physics, Pranab Jubilee College - Bokajan-782480, Karbi- Anglong, Assam, India
² Department of Physics, Tezpur University - Napaam-784028, Tezpur, Assam, India

^(a) pkk@tezu.ernet.in

Received: 25 April 2019
Accepted: 11 November 2019

Abstract

The ultra-low frequency instability that can be excited in a star-forming nonthermal tridust molecular cloud (TMC) is analyzed. The theoretic TMC model is composed of the Cairns-distributed tiny electrons and ions; and bipolar (hetero-polar) massive dust grains alongside partial ionization. The global quasi-neutrality condition is presumed to subsist initially in a homogeneous hydrostatic equilibrium configuration on the Jeans spatiotemporal scales. A procedural normal mode analysis over the perturbed composite vast cloud results in a generalized sextic linear dispersion relation (degree-6) having a unique set of multi-parametric coefficients. It is seen analytically that, in the ultra-low frequency instability regime, the real propagation frequency and the growth rate have explicit nontrivial nonlinear dependences on the Jeans-normalized wave number. A numerical illustrative platform is provided for further depiction and confirmation of the exact nature of the fluctuations alongside stabilizing and destabilizing factors. The Cairns thermo-statistical parameter acts both as a destabilizer in the gravitational domain and stabilizer in the acoustic domain. We conjecture that the neutral dust viscosity, negatively charged dust viscosity, and positively charged dust viscosity stabilize the TMC. The fluctuations get stabilized with an augmentation in the TMC spatial size, and vice versa. The results investigated here go in fair agreement piecewise as diversified special cases reported in the literature. At last, the real astronomical implications and nontrivial applications of the explored results in astrostructures are summarily actualized.