Galaxy rotation curves: the effect of j x B force

TL;DR

This paper investigates how the j x B magnetic force influences galaxy rotation curves, showing it is significant mainly beyond 15 kpc, and offers a model fitting observed baryonic matter with magnetic effects.

Contribution

It presents a model demonstrating the impact of j x B force on galactic rotation curves, emphasizing its importance at larger galactic radii.

Findings

j x B force is negligible at 6-12 kpc

The force significantly affects rotation curves beyond 15 kpc

Magnetic field parameters influence the rotational dynamics

Abstract

Using the Galaxy as an example, we study the effect of j x B force on the rotational curves of gas and plasma in galaxies. Acceptable model for the galactic magnetic field and plausible physical parameters are used to fit the flat rotational curve for gas and plasma based on the observed baryonic (visible) matter distribution and j x B force term in the static MHD equation of motion. We also study the effects of varied strength of the magnetic field, its pitch angle and length scale on the rotational curves. We show that j x B force does not play an important role on the plasma dynamics in the intermediate range of distances 6-12 kpc from the centre, whilst the effect is sizable for larger r (r > 15 kpc), where it is the most crucial.