Study of Interplanetary Magnetic Field with Ground State Alignment

TL;DR

This paper introduces Ground State Alignment (GSA) as a novel ground-based spectropolarimetric method for mapping interplanetary magnetic fields, offering a cost-effective alternative to space probes by analyzing polarization in spectral lines influenced by magnetic realignment.

Contribution

The paper presents GSA as a new technique for magnetic field mapping using ground telescopes, demonstrated through synthetic observations of planetary and cometary environments.

Findings

GSA effectively traces spatial and temporal magnetic field variations.

Polarization signals correlate with magnetic field strength and orientation.

Method applicable to remote regions like IBEX ribbons.

Abstract

We demonstrate a new way of studying interplanetary magnetic field -- Ground State Alignment (GSA). Instead of sending thousands of space probes, GSA allows magnetic mapping with any ground telescope facilities equipped with spectropolarimeter. The polarization of spectral lines that are pumped by the anisotropic radiation from the Sun is influenced by the magnetic realignment, which happens for magnetic field (<1G). As a result, the linear polarization becomes an excellent tracer of the embedded magnetic field. The method is illustrated by our synthetic observations of the Jupiter's Io and comet Halley. Polarization at each point was constructed according to the local magnetic field detected by spacecrafts. Both spatial and temporal variations of turbulent magnetic field can be traced with this technique as well. The influence of magnetic field on the polarization of scattered light is discussed in detail. For remote regions like the IBEX ribbons discovered at the boundary of interstellar medium, GSA provides a unique diagnostics of magnetic field.