SW_TIX_TMS_2F

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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

TEGIX: TEC-gradient ionosphere index

DOI:

European Space Agency, Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), 2025, "SW_TIX_TMS_2F", European Space Agency, https://doi.org/10.57780/esa-1a69b15

Description

TEGIX is the TEC-gradient ionosphere index developed as part of the MIGRAS project to monitor mid-scale irregularities in the total electron content domain with horizontal spatial scales in the order of 100 km. Similar to NEGIX, this product also benefits from the coordinated flight of Swarm satellites A and C that are orbiting the Earth in high inclination Polar orbits, and availability of GNSS satellites in view. The location (referred as measurement points) of the vertical TEC data used for the estimation of gradients is determined by the intersection of the GNSS-Swarm links and an ionospheric layer at an altitude of about 670 km above the Earth’s surface (height of Swarm orbit + 200 km).

Data Access

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

Output variables

Name	Description	Type	Unit
Timestamp	Time in Universal Time	CDF_EPOCH	-
Longitude_Swarm	Averaged geocentric longitude of the Swarm satellites for all combined measurements for a certain epoch.	CDF_DOUBLE	deg
Latitude_Swarm	Averaged geocentric latitude of the Swarm satellites for all combined measurements for a certain epoch.	CDF_DOUBLE	deg
Longitude_IPPs	Position of TEGIX (X, Y) in geocentric longitude. Averaged longitude position of the central points (CPs) derived from the combination of VTEC measurements of Swarm A and C.	CDF_DOUBLE	deg
Latitude_IPPs	Position of TEGIX (X, Y) in geocentric latitude. Averaged latitude position of the central points (CPs) derived from the combination of VTEC measurements of Swarm A and C.	CDF_DOUBLE	deg
Distance	Averaged distance value from all dipoles used for the estimation of TEGIX values	CDF_DOUBLE	m
Azimuth	Averaged azimuth value from all dipoles used for the estimation of TEGIX values	CDF_DOUBLE	deg
Tegix_X	Mean value of TEGIX for the West-East component	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_X_Sigma	Standard deviation value of TEGIX for the West-East component	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_X_P95	95-percentile value of TEGIX for the West-East component	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_Y	Mean value of TEGIX for the South-North component	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_Y_Sigma	Standard deviation value of TEGIX for the South-North component	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_Y_P95	95-percentile value of TEGIX for the South-North component	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_Total	Total vector value of TEGIX, derived from the mean West-East and South-North components	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_Sigma	Vector value of the standard deviation of TEGIX, derived from the standard deviation values of West-East and South-North components	CDF_DOUBLE	milli-TECU m⁻¹
Tegix_P95	Vector value of the 95-percentile of TEGIX, derived from the 95-percentile values of West-East and South-North components	CDF_DOUBLE	milli-TECU m⁻¹
N_Measurements	Number of elements for a data record from which TEGIX is determined	CDF_UINT2	-
Flag_Tegix	Flags characterising the dispersion of VTEC-gradient values within a given spatial resolution that are used to compute the total vector	CDF_UINT1	-
Orbit_Label	Value defining whether the magnitude belongs to an ascending or descending orbit of the Swarm satellites	CDF_INT1	-

Details

Value of Flag_Tegix	Pearson’s Coefficient Value	Description
0	-0.5 ≤ value ≤ 0.5	The distribution of the sample of TEGIX total vectors within the given resolution is slightly skewed.
1	-1.5 ≤ value < -0.5, 0.5 < value ≤ 1.5	The distribution of the sample of TEGIX total vectors within the given resolution is slightly skewed, with possible outliers in the sample.
2	value < -1.5, value > 1.5	The distribution of the sample of TEGIX total vectors within the given resolution is strongly skewed, with a strong influence of outliers that may require more cautious investigation or removal.

It is recommended to cautiously investigate or discard Flags TEGIX with values of 2 when using this product.
It is recommended to cautiously interpret TEGIX values close to the polar regions. These latitudes are not only affected by different sources of ionospheric variability, but the rapidly changing position of Swarm satellites A and C with respect to each other, and therefore of the geometrical distribution of gradient vectors, can also affect TEGIX estimations. Moreover, GNSS satellites near the poles are available at low elevation angles and may create uncertainties in magnitude and position of VTEC gradients.
The values of TEGIX and the location reference of the vector result from statistical estimations of a large sample of IPPs. The estimation of reference positions of the TEGIX vector can be affected by the complex geometrical distribution of GNSS links to the Swarm satellites A and C when they move in the longitude transition -180 to 180 degrees.

Product Identifier	TIX_TMS_2F
Definition	TEGIX is the TEC-gradient ionosphere index developed as part of the MIGRAS project to monitor mid-scale irregularities in the total electron content domain with horizontal spatial scales in the order of 100 km.
Input Data	TECATMS_2F, TECCTMS_2F
Input Time Span	1 day
Spatial Representation	The spatial resolution for each dataset record is 0.5 degrees in latitude along the path of Swarm satellites A and C. Geocentric longitude and latitude coordinates for each dataset record are provided.
Time Representation	The spatial resolution of 0.5 degrees represents ca. 8 seconds of records of Swarm satellites A and C. Therefore, a daily file product contains ca. 10,800 records.
Units	milli-TECU m⁻¹
Resolution	1 milli-TECU m⁻¹
Uncertainty	The uncertainty is reflected in the flags. Higher values in flags indicate irregularities, potential measurement inconsistencies, or issues with geometries, especially in the polar regions.
Quality Indicator	The quality of the product depends on the quality of the input TEC L2 products for Swarm A and C. If the differential code bias error of any of the daily input files is larger than 2 TECU, then the product quality indicator is degraded from 0 to 1. These values are stored in the XML file, as well as in the CDF global attributes.
Data Volume	2 MB
Data Format	CDF
Output Time Span	1 day
Update Rate	Daily
Latency	7 minutes

MIGRAS project

SW_TIX_TMS_2F

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SW_TIX_TMS_2F

Description

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Details

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