TY  - JOUR
A1  - Park, Jaeheung
A1  - Stolle, Claudia
A1  - Yamazaki, Yosuke
A1  - Rauberg, Jan
A1  - Michaelis, Ingo
A1  - Olsen, Nils
T1  - Diagnosing low-/mid-latitude ionospheric currents using platform magnetometers
BT  - CryoSat-2 and GRACE-FO
JF  - Earth, planets and space
N2  - 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 similar to 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.
KW  - Platform magnetometers
KW  - CryoSat-2
KW  - GRACE-FO
KW  - Inter-hemispheric
KW  - field-aligned currents
KW  - F-region dynamo currents
Y1  - 2020
U6  - https://doi.org/10.1186/s40623-020-01274-3
SN  - 1343-8832
SN  - 1880-5981
VL  - 72
IS  - 1
PB  - Springer
CY  - New York
ER  -