[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P24] Observation of geomagnetic field variations with low-cost magnetometers using magneto-
impedance (MI) sensors

*Taiki Maeda¹, Masahito Nose¹, Nomura Hiroshi¹, Takumi Adachi¹, Yuka Yamamoto¹, Atshushi Kumamoto², Sachinobu Ishida³, Hiroshi Ichihara⁴, Takeshi Kawano⁵, Yoshihiro Iwanaga⁵, Shunichi Tatematsu⁵, Seiki Asari⁶, Hideyuki Hirahara⁶, Megumi Kaito⁶, Shingo Nagamachi⁶ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Space and Terrestrial Plasma Physics Laboratory, Tohoku University, 3.Graduate School of Science and Technology, Hirosaki University, 4.Graduate School of Environmental Studies, Nagoya University, 5.Aichi Steel Corporation, 6.Kakioka Magnetic Observatory, Japan Meteorological Agency)

Magneto-impedance (MI) effect was discovered about 25 years ago and a micro-size magnetic sensor that utilizes this effect becomes commercially available. Nosé et al. [2022, JGR, doi:10.1029/2022JA030809] made some modifications to the commercially available MI sensors as they can cover the range of the geomagnetic field. For the period of March 30 to April 27, 2018, they conducted experimental observations of geomagnetic field variations with the MI sensors at Mineyama observation site, which is located about 100 km north-west of Kyoto. Data obtained with the MI sensors were compared with those from the fluxgate magnetometer that has been working at the site. Results showed that the MI sensor recorded geomagnetic variations with amplitudes of ~1 nT that were also detected with the fluxgate magnetometer. This suggests that MI sensors are useful for research in geomagnetism or space physics, although they are much less expensive than fluxgate magnetometers.
Nomura [2021, Master thesis] developed a triaxial magnetometer which is composed of the MI sensors, Raspberry Pi, low-cost 24-bit A/D converters, and stable power supply circuits. This magnetometer is named MIM-Pi, and the cost of MIM-Pi is about one-tenth of that of fluxgate magnetometer. However, the result of the test experiments at Inabu observation site in Japan showed that MIM-Pi had step noises with amplitudes of 2–3 nT which originated from an A/D converter. Therefore, we replaced the A/D converter with a new A/D conversion module (ADPi) and confirmed that modified MIM-Pi did not have such step noises. Long-term observation at Inabu with MIM-Pi has been performed since November 19, 2021 to January 14, 2022. The results show that MIM-Pi can record Sq variations and geomagnetic pulsations with amplitudes of 1–2 nT that were also detected with the fluxgate magnetometer at the same site. We also performed long-term observation at Kakioka Magnetic Observatory and found that MIM-Pi can identify Pc4 pulsations. To install MIM-Pi in a field, we made a jig for MI sensors and a case for the Raspberry Pi and electric components. The continuous observations with MIM-Pi started at Kawatabi Observatory from September 9, 2022 and at Shirakami Observatory from November 15, 2022. We found that the geomagnetic field data acquired by MIM-Pi were affected by temperature changes. In presentation, we will show the MIM-Pi data corrected with temperature data and preliminary analysis results for geomagnetic pulsations.