efieldtool

The Geoelectric Field Calculator Tool was developed by NASA Goddard Space Flight Center and DHS Science and Technology Directorate (S&T). It allows computation of the ground geoelectric field for a given single-point geomagnetic field time series coupled with either a one-dimensional (1D) ground conductivity, or a three-dimensional (3D) surface impedance, ground response model. The 1D option uses the simplified plane wave source and 1D ground formulation of the geomagnetic induction process; the horizontal components of the geoelectric field are computed.

The tool has three options for computing the geoelectric field:

1. Select a time period of interest and geomagnetic field data recorded at one of six different USGS stations. The 1D ground models used for the corresponding stations are from the physiographic CONUS model. Please note that USGS data collected in the tool database include only the past few years and in "real-time" quality. Please apply the second element of the tool with data retrieved from the USGS database to use verified science quality USGS data for historical events.

2. Upload the desired geomagnetic field data and 1D ground model. The geomagnetic data is provided in IAGA2002 format, an international standard in which most observatories and databases (such as Intermagnet) can provide data. The 1D ground conductivity model is provided in the Earth Resistivity Model (ERM) format compatible with that for the models found here. Any of the 1D model files from the USGS site will work directly with the tool.

3. Upload the desired geomagnetic field data and 3D surface impedance, AKA Electromagnetic Transfer Function (EMTF). The geomagnetic data is provided in IAGA2002 format. The 3D surface impedance is provided in the EMTF XML format. Most EMTFs from that site will work directly with the tool.

NOTE! While the tool uses the well-known plane wave method, 3D surface impedance method and verified online computational engine, the output can be only as good as the input. Any erroneous geomagnetic field or ground model data fed into the tool will lead to erroneous geoelectric field output. Users are encouraged to consult with the appropriate NASA official for verifying the quality of the geoelectric field time series before usage in further assessments.

Acknowledgments: USGS is acknowledged for their data that is used in one of the elements of the tool. The development of the tool was supported by DHS S&T.

User needs to be careful to make sure that the geomagnetic field time series is of good quality (no non-physical spikes etc).

Geomagnetic field time series (horizontal components) and ground conductivity model (as 1D ground model or surface impedance)

Time series (horizontal components) of the geoelectric field.