Data DescriptionThis dataset contains three comprehensive components for the FHD (Fitted Horizontal Disturbance) geomagnetic index calculation and validation:01_DataSet_FHD_index.zipFHD Index Dataset Structure The FHD index dataset is organized by year and month, with each folder following the naming convention FHD-YYYYMM (e.g., FHD-200812 for December 2008). File Contents and Descriptions:      01 FHD_global.csvContent: FHD_global index values for the corresponding monthDescription: This file contains the global FHD index calculated using the Fourier series fitting method. The index represents the fitted horizontal disturbance in the Earth's magnetic field, derived from low-latitude geomagnetic stations (magnetic latitude ≤ 50°). The data provides minute-by-minute resolution of geomagnetic activity.Format: CSV file with columns:DATE: Timestamp in YYYY-MM-DD HH:MM:SS formatFHD_global: Global FHD index values in nT (nanotesla)     02 FHD_mean.csvContent: FHD_mean index values for the corresponding monthDescription: This file contains the mean FHD index calculated using direct averaging of corrected Dst values from all available low-latitude stations. This provides a straightforward estimate of the horizontal disturbance without Fourier series fitting.Format: CSV file with columns:DATE: Timestamp in YYYY-MM-DD HH:MM:SS formatFHD_mean: Mean FHD index values in nT (nanotesla)      03 mat_fit_paras_for_FHD_mlt.csvContent: Fourier series fitting parametersDescription: This file contains the Fourier series fitting parameters that can be used to reconstruct all FHD_mlt index family members. These parameters enable the generation of magnetic local time (MLT) dependent FHD indices, providing a complete characterization of the fitted horizontal disturbance pattern as a function of local time.Format: CSV file with columns:DATE: Timestamp in YYYY-MM-DD HH:MM:SS formatParameter_columns: Various Fourier series coefficients (a0, a1, b1, a2, b2, a3, b3) for each time point      07 station_avaliable_df_v2.csvContent: Final station information used in index calculationDescription: This file contains comprehensive information about all stations that were ultimately included in the FHD index calculation. It includes station metadata such as geographic coordinates, geomagnetic coordinates, data quality metrics, and availability flags.Format: CSV file with columns:Station codes as indexglon, glat: Geographic longitude and latitudemlon, mlat: Geomagnetic longitude and latitudeNaNprop: Proportion of missing dataAdditional quality control parametersData Coverage The dataset spans from December 2008 to April 2024, providing continuous coverage of geomagnetic activity over approximately 15.5 years. Each monthly folder contains the complete set of files necessary for both the global FHD index and the reconstruction of MLT-dependent index variations. Quality Control The dataset incorporates multiple levels of quality control:Station selection based on magnetic latitude criteria (≤ 50°)Data completeness verificationOver-fitting detection and station removalFourier series fitting quality assessment02_Cubic Spline Interpolation Verification Figures.zipCubic Spline Interpolation Effect Verification Figure Collection This collection contains comprehensive verification figures demonstrating the effectiveness of cubic spline interpolation in processing geomagnetic station data. The figures include:Data quality assessment plots for individual stationsInterpolation effect comparisons before and after processingStation-specific verification images showing data integrityQuality control visualization for the FHD index calculation processThese figures provide essential validation for the data processing methodology and ensure the reliability of the FHD index calculations.03_Code_Data_Download&Process.zipFHD Index Calculation Code Package This comprehensive code package provides the complete software solution for downloading, processing, and calculating the FHD geomagnetic index. The package includes: Main Scripts:dataDL&process_partA.py: Data download and initial processing moduledataDL&process_partB.py: Advanced processing and FHD calculation moduleFunction Modules:DstCalculation/func_DstCalculation.py: Dst index calculation functionsadd_mlt_time_columns/func_mlt_time_calculator.py: Magnetic Local Time calculation functionsprocess_station_data/func_process_station_data.py: Station data processing and validation functionsfit_dst_data_paras/func_fit_curve_paras.py: Fourier series fitting parameter calculation functionsAPI Interface:supermag-api-2025.py: SuperMAG API interface moduleFeatures:Automated data download from SuperMAG APIComprehensive data quality control and station filteringDual FHD index calculation methods (direct averaging and Fourier series fitting)Debug mode for testing and developmentComplete documentation and usage instructions

Data DescriptionThis dataset contains three comprehensive components for the FHD (Fitted Horizontal Disturbance) geomagnetic index calculation and validation:01_DataSet_FHD_index.zipFHD Index Dataset Structure The FHD index dataset is organized by year and month, with each folder following the naming convention FHD-YYYYMM (e.g., FHD-200812 for December 2008). File Contents and Descriptions:      01 FHD_global.csvContent: FHD_global index values for the corresponding monthDescription: This file contains the global FHD index calculated using the Fourier series fitting method. The index represents the fitted horizontal disturbance in the Earth's magnetic field, derived from low-latitude geomagnetic stations (magnetic latitude ≤ 50°). The data provides minute-by-minute resolution of geomagnetic activity.Format: CSV file with columns:DATE: Timestamp in YYYY-MM-DD HH:MM:SS formatFHD_global: Global FHD index values in nT (nanotesla)     02 FHD_mean.csvContent: FHD_mean index values for the corresponding monthDescription: This file contains the mean FHD index calculated using direct averaging of corrected Dst values from all available low-latitude stations. This provides a straightforward estimate of the horizontal disturbance without Fourier series fitting.Format: CSV file with columns:DATE: Timestamp in YYYY-MM-DD HH:MM:SS formatFHD_mean: Mean FHD index values in nT (nanotesla)      03 mat_fit_paras_for_FHD_mlt.csvContent: Fourier series fitting parametersDescription: This file contains the Fourier series fitting parameters that can be used to reconstruct all FHD_mlt index family members. These parameters enable the generation of magnetic local time (MLT) dependent FHD indices, providing a complete characterization of the fitted horizontal disturbance pattern as a function of local time.Format: CSV file with columns:DATE: Timestamp in YYYY-MM-DD HH:MM:SS formatParameter_columns: Various Fourier series coefficients (a0, a1, b1, a2, b2, a3, b3) for each time point      07 station_avaliable_df_v2.csvContent: Final station information used in index calculationDescription: This file contains comprehensive information about all stations that were ultimately included in the FHD index calculation. It includes station metadata such as geographic coordinates, geomagnetic coordinates, data quality metrics, and availability flags.Format: CSV file with columns:Station codes as indexglon, glat: Geographic longitude and latitudemlon, mlat: Geomagnetic longitude and latitudeNaNprop: Proportion of missing dataAdditional quality control parametersData Coverage The dataset spans from December 2008 to April 2024, providing continuous coverage of geomagnetic activity over approximately 15.5 years. Each monthly folder contains the complete set of files necessary for both the global FHD index and the reconstruction of MLT-dependent index variations. Quality Control The dataset incorporates multiple levels of quality control:Station selection based on magnetic latitude criteria (≤ 50°)Data completeness verificationOver-fitting detection and station removalFourier series fitting quality assessment02_Cubic Spline Interpolation Verification Figures.zipCubic Spline Interpolation Effect Verification Figure Collection This collection contains comprehensive verification figures demonstrating the effectiveness of cubic spline interpolation in processing geomagnetic station data. The figures include:Data quality assessment plots for individual stationsInterpolation effect comparisons before and after processingStation-specific verification images showing data integrityQuality control visualization for the FHD index calculation processThese figures provide essential validation for the data processing methodology and ensure the reliability of the FHD index calculations.03_Code_Data_Download&Process.zipFHD Index Calculation Code Package This comprehensive code package provides the complete software solution for downloading, processing, and calculating the FHD geomagnetic index. The package includes: Main Scripts:dataDL&process_partA.py: Data download and initial processing moduledataDL&process_partB.py: Advanced processing and FHD calculation moduleFunction Modules:DstCalculation/func_DstCalculation.py: Dst index calculation functionsadd_mlt_time_columns/func_mlt_time_calculator.py: Magnetic Local Time calculation functionsprocess_station_data/func_process_station_data.py: Station data processing and validation functionsfit_dst_data_paras/func_fit_curve_paras.py: Fourier series fitting parameter calculation functionsAPI Interface:supermag-api-2025.py: SuperMAG API interface moduleFeatures:Automated data download from SuperMAG APIComprehensive data quality control and station filteringDual FHD index calculation methods (direct averaging and Fourier series fitting)Debug mode for testing and developmentComplete documentation and usage instructions