Field-aligned currents (dual-satellite A-C)
Thematic areas: Ionosphere/Magnetosphere, Space Weather
Applicable missions: Swarm
Applicable spacecraft: Swarm-A, Swarm-C
Time series of field-aligned and radial current densities along the orbit using the dual-satellite method. Field-aligned current (FAC) density is derived by the multiplication of the radial current (IRC) density with the inclination angle of the geomagnetic field. The field-aligned current density can only be calculated at latitudes, where the magnetic field is well inclined, i.e. |I| > 30°. Near the magnetic equator for magnetic inclination angles |I| < 30° FAC values are set to NaN. The radial current density can be provided along the whole orbit, except for latitudes θ>86° (near poles), where both FAC and IRC values are set to NaN.
Note that the magnetic field data used for the dual-satellite method is low-pass filtered with a 3-dB cutoff period of 20 s (corresponding to a wavelength of 150 km). This step is indispensable because the lateral distance between Swarm A and Swarm C has to be taken into account.
N/A
(delivered separately)
| Variable | Units | Description | Dim | Type |
|---|---|---|---|---|
| Timestamp | ms | Time, UTC | 1 | CDF_EPOCH |
| Latitude | degrees | Position in ITRF, Latitude | 1 | CDF_DOUBLE |
| Longitude | degrees | Position in ITRF, Longitude | 1 | CDF_DOUBLE |
| Radius | m | Position in ITRF, Radius | 1 | CDF_DOUBLE |
| IRC | uA/m2 | Ionospheric radial current (IRC) | 1 | CDF_DOUBLE |
| IRC_Error | uA/m2 | uncertainty of IRC | 1 | CDF_DOUBLE |
| FAC | uA/m2 | Field-aligned current (FAC) | 1 | CDF_DOUBLE |
| FAC_Error | uA/m2 | uncertainty of FAC | 1 | CDF_DOUBLE |
| Flags | - | Flags characterizing the product quality (processing flags) | 1 | CDF_UINT4 |
| Flags_F | - | Flags_F passed through from L1b and accumulated for quad points | 1 | CDF_UINT4 |
| Flags_B | - | Flags_B passed through from L1b and accumulated for quad points | 1 | CDF_UINT4 |
| Flags_q | - | Flags_q passed through from L1b and accumulated for quad points | 1 | CDF_UINT4 |
| Product identifier | FAC_TMS_2F |
| Definition | Time series of field-aligned and radial current densities along the orbit using the dual-satellite method. Field-aligned current (FAC) density is derived by the multiplication of the radial current (IRC) density with the inclination angle of the geomagnetic field. The field-aligned current density can only be calculated at latitudes, where the magnetic field is well inclined, i.e. |I| > 30°. Near the magnetic equator for magnetic inclination angles |I| < 30° FAC values are set to NaN. The radial current density can be provided along the whole orbit, except for latitudes θ>86° (near poles), where both FAC and IRC values are set to NaN. Note that the magnetic field data used for the dual-satellite method is low-pass filtered with a 3-dB cutoff period of 20 s (corresponding to a wavelength of 150 km). This step is indispensable because the lateral distance between Swarm A and Swarm C has to be taken into account. |
| Input data | MAGA_LR_1B, MAGC_LR_1B, Time stamps (UTC), AUX_IGR_2F, AUX_COR_2F, AUX_LIT_2F, AUX_PMF_2F, AUX_F10_2F, AUX_DST_2F, AUX_IMF_2F, AUX_SWV_2F, AUX_PSM_2F, AUX_PGM_2F |
| Input time span | 3 days |
| Spatial representation | Current density estimates along entire orbits at positions between Swarm A and C |
| Time representation | Time series of current density, Δt=1sec |
| Units | Current density: µA/m2 |
| Resolution | Current density: 1E-6 µA/m2 |
| Uncertainty | 50 nA/m2 for periods 10s to 90min on top of constant bias of <200nA/m2, for latitudes below 80°, gradually degrading between 80° to 86°, no values beyond 86° |
| Quality indicator | See Flags |
| Data volume | 5 MB per day |
| Output data | CDF file with time series |
| Output time span | 1day |
| Update rate | 1 per day |
| Latency | 10 min |
| Notes |
Flags: A table below presents the list of 10 individual and independent digits, characterizing the FAC-dual (FAC_TMS_2F) product quality. Digits from 1 to 8 report issues that may have been occurred at one or more of the measurement points used for the computation of a current density value. Digits 9 and 10 report whether the NaN values for the current density were used or not. Values N>0 mark the number of measurement points that were affected and value 0 marks not affected ones. For FAC-dual N can be equal to 1, 2, 3, or 4. Flags_B, Flags_F and Flags_q are handed through from Level 1b processing
| Digit-Nr. | Value | Meaning |
|---|---|---|
| 1 | 0/N | A short (< 5 seconds) data gap occurred, which was interpolated linearly |
| 2 | 0/N | A long (> 5 seconds) data gap occurred, which cannot be interpolated linearly, in the vicinity |
| 3 | 0/N | No EST (external part of AUX_DST_2F) data were available, and a default value was used for the magnetospheric field model |
| 4 | 0/N | No IST (external part of AUX_DST_2F) data were available, and a default value was used for the magnetospheric field model |
| 5 | 0/N | No solar radio flux (AUX_F10_2F) data were available, and a default value was used for the magnetospheric field model |
| 6 | 0/N | No interplanetary magnetic field (AUX_IMF_2F) data were available, and a default value was used for the magnetospheric field model |
| 7 | 0/N | No Em (merging electric field) data were available, and a default value was used for the magnetospheric field model |
| 8 | 0/N | No magnetospheric field coefficients (Aux_PMF_2F or Aux_PSM_2F or Aux_PGM_2F) were available, and magnetospheric field is set to 0 |
| 9 | 0/1 | For FAC-dual, this digit is equal to 1 if latitude |θ| >86° (near geographic poles) (IRC = NaN and FAC = NaN) |
| 10 | 0/1 | This digit is equal to 1 if inclination |I| < 30° (near magnetic equator) (FAC = NaN) |
Swarm L2 FAC-dual Product Description
N/A