Remote sensing of geomagnetic fields and atomic collisions in the mesosphere

Abstract

Magnetic-field sensing has contributed to the formulation of the plate-tectonics theory, mapping of underground structures on Earth, and the study of magnetism of other planets. Filling the gap between space-based and near-Earth observations, we demonstrate a remote measurement of the geomagnetic field at an altitude of 85–100 km. The method consists of optical pumping of atomic sodium in the mesosphere with an intensity-modulated laser beam, and ground-based observation of the resultant magneto-optical resonance near the Larmor precession frequency. Here we validate this technique and measure the Larmor precession frequency of sodium and the corresponding magnetic field with an accuracy level of 0.28 mG Hz−1/2. These observations allow the characterization of atomic-collision processes in the mesosphere. Remote detection of mesospheric magnetic fields has potential applications such as mapping magnetic structures in the lithosphere, monitoring space weather, and electric currents in the ionosphere.

Evidence for degenerate mirrorless lasing in alkali metal vapor: forward beam magneto-optical experiment

“…Future work will include comprehensive studies of mirrorless lasing in the backward direction, which could be useful for remote mesospheric magnetic sensing using the sodium layer as a sensor [18].…”

Remote Magnetometry With Mesospheric Sodium Based on Gated Photon Counting

“…To further eliminate current noise, we plan to develop a lock‐in amplifier detection method from the gated photon counting data collection and the differential/ratio counter as described in Pedreros Bustos, Bonaccini Calia, et al (). PRF varies between f c + Δ f and f c − Δ f at a dither frequency f dither , where the central frequency f c sweeps in a linear fashion and Δ f is fixed to a value greater than the resonance width.…”

“…In 2018, Kane et al first determined geomagnetic fields in the mesosphere remotely (Kane et al, ). Soon afterward, due to the more advanced laser and other experimental conditions, another result of mesospheric magnetometry was reported, while the accuracy level was enhanced by nearly an order of magnitude (Pedreros Bustos, Bonaccini Calia, et al, ). Mesospheric magnetometry was also demonstrated by modulating the polarization of a continuous‐wave laser (Pedreros Bustos, Calia, et al, ).…”

Quantum magnetic gradiometer with entangled twin light beams

“…Precision measurement technology based on optical magnetometry with high sensitivity (1-7) has great potential for applications in a diversity of fields, such as fundamental physics (8)(9)(10)(11)(12)(13), biomag (14)(15)(16)(17)(18)(19), chemistry (20,21), materials science (22)(23)(24)(25)(26), geology (27), and astronomy (28). So far, there have existed several limits including spin projection noise (SPN), photon shot noise (PSN), and ambient magnetic field noise, which are the obstacles to further improving the sensitivity of conventional magnetometry.…”

“…Quantum-enhanced magnetometry with squeezed light has been proposed and demonstrated for decades (30)(31)(32)(33)(34)(35)(36)(37). Because of technically existing incompatibility between squeezing source and magnetometer, the quantum enhancement has not been observed at low frequencies and the enhanced sensitivity remains subpicotesla level even at high frequencies, which greatly restricts its practicability in certain applications requiring high sensitivity at low frequencies (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(25)(26)(27)(28). On the other hand, the now reported quantum-enhanced magnetometry is well shielded from ambient magnetic field noise.…”