Magnetic tides in atmosphere and ocean driven by moon

Both Earth’s oceans and upper atmosphere produce electric current and electromagnetic (EM) fields. Tides caused by the gravitational interaction between the Earth, the Sun and the Moon create reliable, easily constrained electromagnetic signals in both the ocean and upper atmosphere. Geophysicists are interested in using these ocean tidal electromagnetic signals to study the electrical conductivity of Earth’s interior—however, this requires a solid understanding of the upper atmosphere’s contribution to the electromagnetic signal. This study uses a physics-based model to estimate the relative electromagnetic tidal signals of the ocean versus the upper atmosphere to immediately address this concern. We also compare the model predictions with the electromagnetic tidal signals constrained from 64 global observatories. Considering the level of complexity of the upper atmosphere’s electromagnetic tidal signals, we find remarkable agreement between the observed and modeled electromagnetic tidal signals. Some of the discrepancies may be of interest to those in upper atmospheric / space physics because they may be due to unmodeled physical processes. Our results are also very encouraging for geophysicists aiming to use electromagnetic tidal signals to study Earth’s interior since they suggest a small upper atmosphere contribution to the electromagnetic tidal signal generally used.

The background map illustrates the total scalar M2 magnetic field amplitude (left) and phase (right) predicted from the sum of the ionosphere and ocean sources. Each colored dot represents the total M2 scalar field amplitude (left) and phase (right) at a geomagnetic observatory (Reproduced from Schnepf et al., 2018).

 

Grids of the ionospheric and oceanic M2 tidal magnetic fields at sea level. Methodology and discussion of results in:

Schnepf, N. R., M. Nair, A. Maute, N. M. Pedatella, A. Kuvshinov, A. D. Richmond (2018). A comparison of model-based ionospheric and ocean tidal magnetic signals with observatory data. Geophysical Research Letters. (doi: 10.1029/2018GL078487)

Download Ionospheric-Oceanic M2 Simulation (IOMS) Data
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The readme.

Download Data .csv 0.574 iono_Fi (180x360): the imaginary part of F calculated from the sealevel ionospheric M2 prediction.
Download Data .csv 0.574 iono_Fr (180x360): the real part of F calculated from the sealevel ionospheric M2 prediction.
Download Data .csv 0.552 iono_pi (180x360): The imaginary part of the ionospheric M2 predicted phi component
Download Data .csv 0.550 iono_pr (180x360): The real part of the ionospheric M2 predicted phi component
Download Data  .csv 0.592 iono_ri (180x360): The imaginary part of the ionospheric M2 predicted radial component
Download Data .csv 0.594 iono_rr (180x360): The real part of the ionospheric M2 predicted radial component
Download Data  .csv 0.556 iono_ti (180x360): The imaginary part of the ionospheric M2 predicted theta component
Download Data  .csv 0.555 iono_tr (180x360): The real part of the ionospheric M2 predicted theta component
Download Data .csv 9.0 ocean_Fi (720x1440): the imaginary part of F calculated from the sealevel oceanic M2 prediction
Download Data .csv 8.9 ocean_Fr (720x1440): the real part of F calculated from the sealevel oceanic M2 prediction
Download Data  .csv 9.1 ocean_pi (720x1440): The imaginary part of the oceanic M2 predicted phi component
Download Data .csv 9.0 ocean_pr (720x1440): The real part of the oceanic M2 predicted phi component
Download Data .csv 9.0 ocean_ri (720x1440): The imaginary part of the oceanic M2 predicted radial component
Download Data .csv 8.9 ocean_rr (720x1440): The real part of the oceanic M2 predicted radial component
Download Data  .csv 9.0 ocean_ti (720x1440): The imaginary part of the oceanic M2 predicted theta component
Download Data .csv  9.0 ocean_tr (720x1440): The real part of the oceanic M2 predicted theta component