Laser remote magnetometry using mesospheric sodium

TL;DR

This paper demonstrates a novel remote magnetometry technique using laser illumination of mesospheric sodium atoms at 106 km, achieving a sensitivity comparable to ground-based measurements and outlining pathways for significant improvements.

Contribution

The study introduces a remote magnetometer based on mesospheric sodium atoms, achieving measurements at 106 km distance with potential for enhanced sensitivity using advanced optics and lasers.

Findings

Measured magnetic field consistent with Earth's known field within a fraction of a percent

Achieved sensitivity of 162 nT/√Hz with current setup

Projected improvements could reach 1 nT/√Hz sensitivity

Abstract

We have demonstrated a remote magnetometer based on sodium atoms in the Earth's mesosphere, at a 106-kilometer distance from our instrument. A 1.33-watt laser illuminated the atoms, and the magnetic field was inferred from back-scattered light collected by a telescope with a 1.55-meter-diameter aperture. The measurement sensitivity was 162 nT/$\sqrt{Hz}$. The value of magnetic field inferred from our measurement is consistent with an estimate based on the Earth's known field shape to within a fraction of a percent. Projected improvements in optics could lead to sensitivity of 20 nT/$\sqrt{Hz}$, and the use of advanced lasers or a large telescope could approach 1-nT/$\sqrt{Hz}$ sensitivity. All experimental and theoretical sensitivity values are based on a 60$^\circ$ angle between the laser beam axis and the magnetic field vector; at the optimal 90$^\circ$ angle sensitivity would be improved by about a factor of two.