http://arxiv.org/abs/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{\deg} angle between the laser beam axis and the magnetic field vector; at the optimal 90{\deg} angle sensitivity would be improved by about a factor of two.
T. Kane, P. Hillman, C. Denman, et. al.
Wed, 19 Oct 16
31/87
Comments: 15 pages, 15 figures, 4 tables