Diagnosing low-/mid-latitude ionospheric currents using platform magnetometers: CryoSat-2 and GRACE-FO

Earth, Planets and Space

Nils Olsen¹  Jan Rauberg²  Ingo Michaelis²  Yosuke Yamazaki²  Claudia Stolle³  Jaeheung Park⁴ 

[1] DTU Space, National Space Institute, Technical University of Denmark, Kongens Lyngby, Denmark;GFZ-German Research Centre for Geosciences, Sect. 2.3, Geomagnetism, Potsdam, Germany;GFZ-German Research Centre for Geosciences, Sect. 2.3, Geomagnetism, Potsdam, Germany;Faculty of Science, University of Potsdam, Potsdam, Germany;Space Science Division, Korea Astronomy and Space Science Institute, Daejeon, South Korea;Department of Astronomy and Space Science, Korea University of Science and Technology, Daejeon, South Korea;

关键词: Platform magnetometers;    CryoSat-2;    GRACE-FO;    Inter-hemispheric field-aligned currents;    F-region dynamo currents;   

DOI  :  10.1186/s40623-020-01274-3

来源: Springer

【 摘 要 】

Electric currents flowing in the terrestrial ionosphere have conventionally been diagnosed by low-earth-orbit (LEO) satellites equipped with science-grade magnetometers and long booms on magnetically clean satellites. In recent years, there are a variety of endeavors to incorporate platform magnetometers, which are initially designed for navigation purposes, to study ionospheric currents. Because of the suboptimal resolution and significant noise of the platform magnetometers, however, most of the studies were confined to high-latitude auroral regions, where magnetic field deflections from ionospheric currents easily exceed 100 nT. This study aims to demonstrate the possibility of diagnosing weak low-/mid-latitude ionospheric currents based on platform magnetometers. We use navigation magnetometer data from two satellites, CryoSat-2 and the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), both of which have been intensively calibrated based on housekeeping data and a high-precision geomagnetic field model. Analyses based on 8 years of CryoSat-2 data as well as ~ 1.5 years of GRACE-FO data reproduce well-known climatology of inter-hemispheric field-aligned currents (IHFACs), as reported by previous satellite missions dedicated to precise magnetic observations. Also, our results show that C-shaped structures appearing in noontime IHFAC distributions conform to the shape of the South Atlantic Anomaly. The F-region dynamo currents are only partially identified in the platform magnetometer data, possibly because the currents are weaker than IHFACs in general and depend significantly on altitude and solar activity. Still, this study evidences noontime F-region dynamo currents at the highest altitude (717 km) ever reported. We expect that further data accumulation from continuously operating missions may reveal the dynamo currents more clearly during the next solar maximum.

【 授权许可】

CC BY