Laser remote magnetometry using mesospheric sodium

• Main Authors: Kane, Thomas J, Hillman, Paul D, Denman, Craig A, Hart, Michael, Scott, R. Phillip, Purucker, Michael E, Potashnik, Stephen J
• Format: Journal Article
• Language: English
• Published: 17.10.2016
• Subjects: Physics - Atomic Physics; Physics - Earth and Planetary Astrophysics; Physics - Instrumentation and Detectors; Physics - Instrumentation and Methods for Astrophysics; Physics - Space Physics
• DOI: 10.48550/arxiv.1610.05385

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.