On the significance of polarization charge and isomagnetic surface in the interaction between conducting fluid and magnetic field

TL;DR

This paper reevaluates the frozen-in magnetic field line concept in conducting fluids, emphasizing the roles of polarization charges and isomagnetic surfaces, and demonstrates conditions under which fluids can freely cross magnetic field lines.

Contribution

It introduces the significance of polarization charges and isomagnetic surfaces, providing a new analytical perspective on fluid-magnetic field interactions and sunspot magnetic field origins.

Findings

Conducting fluids can traverse magnetic field lines along isomagnetic surfaces.

Magnetic resistance depends solely on magnetic gradient in the direction of fluid motion.

Experimental results support the analytical conclusions.

Abstract

From the frozen-in field lines concept, a highly conducting fluid can move freely along, but not traverse to, magnetic field lines. We discuss this topic and find that in the study of the frozen-in field lines concept, the effects of inductive and capacitive reactance have been omitted. When admitted, the relationships among the motional electromotive field, the induced electric field, the eddy electric current, and the magnetic field becomes clearer and the frozen-in field line concept can be reconsidered. We emphasize the importance of isomagnetic surfaces and polarization charges, and show analytically that whether a conducting fluid can freely traverse magnetic field lines or not depends solely on the magnetic gradient in the direction of fluid motion. If a fluid does not change its density distribution and shape (can be regarded as a quasi-rigid body), and as long as it is moving along an isomagnetic surface, it can freely traverse magnetic field lines without any magnetic resistance no matter how strong the magnetic field is. When our analysis is applied, the origin of the magnetic field of sunspots can be interpreted easily. In addition, we also present experimental results to support our analysis.