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Updated: Jun 6, 2025
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Magnetic Tweezers for the Measurement of Twist and Torque
Published on: May 19, 2014
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Oceanic and ionospheric tidal magnetic fields extracted from global geomagnetic observatory data
Robert H Tyler1, David S Trossman2
1NASA Goddard Space Flight Center, Planetary Magnetospheres Laboratory, Greenbelt, Maryland, MD, USA.
Summary
Ocean magnetic fields reveal heat content changes. Researchers extracted tidal signals from geomagnetic data, finding ephemeris predictors superior for remote sensing of Earth
Area of Science:
- Geophysics
- Oceanography
- Magnetometry
Background:
- Ocean tides generate magnetic fields that encode information about ocean dynamics.
- Remotely sensed magnetic data offers a potential avenue for monitoring ocean heat content and transport.
- Establishing a baseline of extracted tidal signals is crucial for developing this remote sensing capability.
Purpose of the Study:
- To extract and analyze ocean tide-generated magnetic signals from land-based geomagnetic observatory data.
- To establish a baseline for the potential retrieval of ocean heat content and transport information from magnetic data.
- To compare the efficacy of different prediction models for tidal signal extraction.
Main Methods:
- Utilized robust iteratively reweighted least squares for tidal signal extraction.
- Analyzed 288 land geomagnetic observatory records spanning 1965-2015.
- Compared time-harmonic predictors with predictors based on lunar and solar ephemerides and gravitational theory.
Main Results:
- Ephemeris-based predictors demonstrated superior performance over time-harmonic methods, fitting more variance with fewer parameters.
- The vertical magnetic vector component, after principle-component rotation, yielded the highest signal-to-noise ratio for lunar tidal signals.
- Specific ephemeris predictors, such as lunar azimuth weighted by lunar distance, proved effective for semidiurnal tidal signal prediction.
Conclusions:
- Ocean tide-generated magnetic fields contain valuable information about oceanographic processes.
- Ephemeris-based modeling provides a more effective method for extracting tidal magnetic signals compared to traditional approaches.
- This study provides a foundational dataset and methodology for magnetometric remote sensing of Earth's oceans.
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