

European Space Agency, Romanian Institute of Space Science, 2025, "SW_FAC_SVD_2F", European Space Agency, https://swarmhandbook.earth.esa.int/catalogue/SW_FAC_SVD_2F
| Variable Name | Data Type | Description | Units |
|---|---|---|---|
| Timestamp | CDF_EPOCH | Time, UTC | milliseconds |
| Latitude | CDF_DOUBLE | Position in ITRF, Latitude | degrees |
| Longitude | CDF_DOUBLE | Position in ITRF, Longitude | degrees |
| Radius | CDF_DOUBLE | Position in ITRF, Radius | m |
| FAC | CDF_DOUBLE | FAC density | µA/m2 |
| IRC | CDF_DOUBLE | IRC density | µA/m2 |
| FACerr | CDF_DOUBLE | Uncertainty of FAC | µA/m2 |
| IRCerr | CDF_DOUBLE | Uncertainty of IRC | µA/m2 |
| Flag | CDF_UINT2 | Quality flag | - |
| Product Identifier | FAC_SVD_2F | ||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Definition |
Time-series of field-aligned current (FAC) and radial current (IRC) densities along the orbit using the dual-satellite singular value decomposition (SVD) method. IRC density is obtained by applying the Ampere’s law on four-point configurations, formed along the orbit by combining satellite positions from Swarm A and Swarm C. When the satellite’s cross-track separation is much smaller than the along-track distance, only the along-track gradients are used in the analysis and the algorithm yields estimates that are close to the average (over the satellites) single-satellite estimates. To avoid discontinuous current density solutions, the transition between full planar and linear gradient estimations is smoothed. IRC density is thus provided along the whole orbit. The FAC density, derived from IRC density by considering the local inclination of the magnetic field, can only be calculated at latitudes where the geomagnetic field inclination is > 30° or < - 30°.
Note: to minimize the influence of small-scale fluctuations at each satellite and to match the scale of the magnetic perturbations with the configuration scale, the magnetic field data is filtered with a Butterworth, order 5, 20 s cut-off low-pass filter. |
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| Input Data | MAGx_LR_1B, AUXxORBCNT, x = [A,C], latest CHAOS model1 including contributions from core, lithosphere, magnetosphere and secondary currents. | ||||||||||||||||||||||||||||||||||||||||
| Input Time Span | 3 days | ||||||||||||||||||||||||||||||||||||||||
| Spatial representation | Current density estimates along the entire orbits at positions between Swarm A and Swarm C | ||||||||||||||||||||||||||||||||||||||||
| Time representation | Time-series of current densities at 1 s resolution | ||||||||||||||||||||||||||||||||||||||||
| Units | Current densities: µA/m2 | ||||||||||||||||||||||||||||||||||||||||
| Resolution | Current density: 1E-6 µA/m2 | ||||||||||||||||||||||||||||||||||||||||
| Uncertainty | 25 nA/m2 around ± 86.6°, decreasing towards Equator and poles | ||||||||||||||||||||||||||||||||||||||||
| Quality Indicator |
Product quality flag. The meaning of the individual bits are described below:
Examples:
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| Data Volume | < 4 MB per day | ||||||||||||||||||||||||||||||||||||||||
| Data Format | CDF | ||||||||||||||||||||||||||||||||||||||||
| Output Data |
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| Output Time Span | 1 day | ||||||||||||||||||||||||||||||||||||||||
| Update Rate | daily | ||||||||||||||||||||||||||||||||||||||||
| Latency | < 1 min | ||||||||||||||||||||||||||||||||||||||||
| Notes | 1Version information of Input Data are available in the CDF global attributes. |