SW_FAC_LLS_2F

Product List

Filters

Short product names

CH_DNS_ACC_2_CH_TEC_TMS_2F CH_WND_ACC_2_CS_MAG GF_DNSxACC_2_GF_NE__KBR_2F GF_TECxTMS_2F GF_WNDxACC_2_GFx_FGM_ACAL_CORR GO_MAG_ACAL_CORR GR_DNSxACC_2_GR_NE__KBR_2F GR_TECxTMS_2F GR_WNDxACC_2_GRACE_x_MAG MM_CON_EPH_2_SW_ACCx_AE_2_SW_ACCxCAL_2_SW_ACCxPOD_2_SW_AEJxLPL_2F SW_AEJxLPS_2F SW_AEJxPBL_2F SW_AEJxPBS_2F SW_AOBxFAC_2F SW_ASMxAUX_1B SW_ASMxBUR_1B SW_AUXxORBCNT SW_CFW_SHA_2Y SW_DNSxACC_2_SW_DNSxPOD_2_SW_EEFxTMS_2F SW_EFIx_LP_1B SW_EFIx_LP_FP SW_EFIx_LP_HM SW_EFIx_TCT02 SW_EFIx_TCT16 SW_EFIx_TII1B SW_EFIxIDM_2_SW_EFIxLPI_1B SW_EFIxTIE_2_SW_EFIxTISH1B SW_EFIxTISL1B SW_EGF_SHA_2_SW_FAC_LLS_2F SW_FAC_SVD_2F SW_FAC_TMS_2F SW_FACxTMS_2F SW_GPSx_RN_1B SW_GPSx_RO_1B SW_GPSxNAV_1B SW_IBIxTMS_2F SW_IBP_CLI_2_SW_IPDxIRR_2F SW_LP_x_CA_1B SW_MAGx_CA_1B SW_MAGx_HR_1B SW_MAGx_LR_1B SW_MCO_SHA_2C SW_MCO_SHA_2D SW_MCO_SHA_2F SW_MCO_SHA_2X SW_MCO_SHA_2Y SW_MCR_1DM_2_SW_MIN_1DM_2_SW_MIO_SHA_2C SW_MIO_SHA_2D SW_MIO_SHA_2E SW_MITx_LP_2F SW_MITxTEC_2F SW_MLI_SHA_2C SW_MLI_SHA_2D SW_MLI_SHA_2E SW_MMA_SHA_2C SW_MMA_SHA_2F SW_MODx_SC_1B SW_MTI_SHA_2C SW_NIX_TMS_2F SW_PC1xMAG_2F SW_PPIxFAC_2F SW_SC_xDYN_1B SW_SP3xCOM_2_SW_SP3xKIN_2_SW_STRxATT_1B SW_STRxEPF_1B SW_TECxTMS_2F SW_TIX_TMS_2F SW_ULFxMAG_2F SW_VFMxAUX_1B SW_VOBS_1M_2_SW_VOBS_4M_2_SW_WHIxEVT_2_

Full product name

Field-aligned currents (dual-satellite A-C, local least-squares method)

DOI:

European Space Agency, Romanian Institute of Space Science, 2025, "SW_FAC_LLS_2F", European Space Agency, https://doi.org/10.57780/esa-2879355

Description

Time-series of field-aligned current (FAC) and radial current (IRC) densities along the orbit using the dual-satellite local least-squares (LLS) 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. IRC density is provided along the whole orbit, except in the region close to the orbital cross-point, when the geometry of the four-point configurations becomes too elongated (i.e. for absolute values in latitude > approx. 86.6° during Swarm nominal orbit configuration). 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.

Data Access

Files
- HTTPS (Product files): https://swarm-diss.eo.esa.int/#swarm/Level2daily/Latest_baselines/FAC/LLS/Sat_AC
- FTP (Product files): ftp://swarm-diss.eo.esa.int/Level2daily/Latest_baselines/FAC/LLS/Sat_AC

Output variables

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	-

Details

Product Identifier

FAC_LLS_2F

Definition

Time-series of field-aligned current (FAC) and radial current (IRC) densities along the orbit using the dual-satellite local least-squares (LLS) 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. IRC density is provided along the whole orbit, except in the region close to the poles (i.e. for absolute values in latitude > approx. 86.6°). 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.

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

Quality Indicator

Product quality flag. The meaning of the individual bits are described below:

Bit nr.	Value	Meaning
1	0/1	Value is 1 when at least one absent magnetic field value at quad’s corners
2-4	0/N	Number of bad magnetic field values (i.e. magnetic field components set to zero in the MAGx_LR_1B files) at quad’s corners. N = 0 - 4
5-7	0/N	Number of interpolated magnetic field value at quad’s corners. Interpolated values occur when the interval of bad magnetic data is less than 4 s. N = 0 - 4
8	0/1	Value is 1 when the interval of valid magnetic data is too small for data filtering. This occurs when the interval of time-consecutive quads is < 30 s.
9	0/1	Value is 1 when the quad is too elongated / too close to the orbital cross-point. This roughly corresponds to absolute values in (quad mesocenter) geographic latitude > 86.6 deg. for Swarm nominal phase.
10	0/1	Value is 1 when the quad is too close to the Equator and the FAC density cannot be computed. This occurs when the (absolute value of) magnetic field inclination with respect to the quad plane is < 30 deg.

Examples:

Flag = 1 (binary 0000000001): Valid IRC estimation; FAC density could not be computed because the quad is too close to the Equator.
Flag = 128 (binary 0010000000): 2 bad magnetic field values at quad’s corners that were not interpolated. IRC and FAC are set to NaN.

Data Volume

< 4 MB per day

Data Format

CDF

Output Data

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

Output Time Span

1 day

Update Rate

daily

Latency

< 1 min

Notes

¹Version information of Input Data are available in the CDF global attributes.

SW_FAC_LLS_2F

Filters

Short product names

SW_FAC_LLS_2F

Description

Data Access

Output variables

Details

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