Analytical method for evaluating DIXSG factor performance in monitoring global ionospheric scintillation

Abstract

The present invention discloses an analysis method for evaluating the performance of DIXSG factor in monitoring global ionospheric scintillation, and belongs to the field of space weather monitoring and satellite navigation applications. By calculating the ionospheric total electron content change rate index ROTI and the ionospheric disturbance spatial gradient index DIXSG that take into account satellite altitude angle suppression; dividing the globe and a certain region into longitude and latitude grids, calculating the ROTI and DIXSG factor maps within the spatial range; using the time and space amplitude disturbance trends of ROTI and DIXSG factors, the DIXSG factor is evaluated to monitor the disturbance degree of ionospheric scintillation on a global scale. This method has simple steps, helps to evaluate the scintillation monitoring performance of the DIXSG factor on a global scale and in high, medium and low latitude regions from a temporal and spatial perspective, and has wide practicality.

Description

Technical Field

[0001] The invention relates to an analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance, and belongs to the field of space weather monitoring and satellite navigation applications. Technical Background

[0002] Ionospheric irregularities caused by geomagnetic disturbances will interfere with the propagation of satellite signals. When the Global Navigation Satellite System (GNSS) signal passes through ionospheric irregularities, the amplitude or phase of the signal will fluctuate rapidly. This phenomenon is called ionospheric scintillation. Ionospheric scintillation not only reflects the structural characteristics of ionospheric irregularities, but also affects the GNSS satellite-to-ground link, thereby interfering with the GNSS's stable positioning, navigation and timing services. Obviously, ionospheric scintillation poses a serious threat to the sustainable development of human society. Therefore, monitoring the laws of ionospheric disturbances and verifying their prediction accuracy are of great practical significance for preventing and mitigating ionospheric scintillation disasters and reducing economic losses.

[0003] Traditionally, two types of scintillation factors provided by ionospheric scintillation monitoring receivers (ISMRs) are used, namely, the amplitude scintillation factor S4 and the phase scintillation factor σ φ Quantitatively characterize the impact of ionospheric scintillation on GNSS signals. Since ISMR requires a large amount of memory to store data and a highly stable receiver clock to maintain tracking performance during scintillation, a series of conditions limit the distribution of ISMR and cannot support regional or global intensive scintillation monitoring research. Compared with ISMR, the sampling frequency of geodetic receivers is usually 1 / 30Hz, which can stably provide long-term GNSS observation data and is widely distributed, especially in the Arctic region, where full coverage can be achieved. Therefore, extracting ionospheric scintillation factors using GNSS geodetic receiver network data with a widely distributed 30s sampling interval is conducive to studying the actual disturbance of ionospheric scintillation and verifying the accuracy of ionospheric scintillation monitoring. Most of the existing studies focus on the analysis of monitoring accuracy of a certain disturbance event in the past or a short period of time, focusing on describing the changing characteristics of GNSS signals in the time domain, and the study of spatial scale changes is insufficient. At present, there is no evaluation of the performance of DIXSG factor in monitoring global ionospheric scintillation in time and space, especially the adaptability to global ionospheric scintillation monitoring under the complex environmental conditions of the new solar cycle. Summary of the invention

[0004] In view of the shortcomings of the existing technology, an analysis method for evaluating the performance of DIXSG factor in monitoring global ionospheric scintillation is provided, which can promote the monitoring of ionospheric scintillation by widely distributed geodetic receivers and solve the technical problem of evaluating the performance of DIXSG factor in monitoring global ionospheric scintillation in time and space.

[0005] To achieve the above technical objectives, the present invention discloses an analysis method for evaluating the performance of DIXSG factor in monitoring global ionospheric scintillation, which is characterized in that the ability of DIXSG factor in monitoring ionospheric scintillation is evaluated based on the global GNSS geodetic receiver network data, and the steps are as follows:

[0006] S1 selects at least two geodetic receivers in the international GNSS service IGS to form a network, generates a network data set from the network data of all geodetic receivers, and performs data preprocessing on the network data set: removing short arc segments, controlling altitude angles, and detecting and repairing cycle slips;

[0007] S2 estimates the slant path total electron content STEC using the carrier phase smoothed pseudorange method for the preprocessed receiver network data set, and calculates the total electron content change rate index factor ROTI and the ionospheric disturbance spatial gradient index factor DIXSG of the receiver network data set suppressed by all visible satellite elevation angles within a preset time interval;

[0008] S3 divides the global range into 1°×1° longitude and latitude grids, and divides the area to be studied into 0.5°×0.5° longitude and latitude grids, and calculates the spatial variation maps of ROTI factor and DIXSG factor respectively;

[0009] S4 sorts the calculated ROTI factors by time and draws a time series diagram and a spatial variation map, evaluating the performance of the DIXSG factor in monitoring global ionospheric scintillation in time and space. The evaluation criteria include two aspects:

[0010] Evaluate the monitoring performance of the DIXSG factor for global ionospheric scintillation monitoring;

[0011] Evaluate the monitoring performance of DIXSG factor in monitoring ionospheric scintillation in the high, middle or low latitudes of the Earth, where the high latitudes are 60 degrees and above, the middle latitudes are 30 to 60 degrees, and the low latitudes are 0 to 30 degrees.

[0012] The temporal and spatial variation map of the ROTI factor is used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor. If they are consistent, it means that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation; if they are inconsistent, it means that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in a certain area; and the temporal and spatial fluctuation trends of the ROTI factor and the DIXSG factor are used to evaluate the temporal and spatial scintillation monitoring performance of the DIXSG factor from multiple latitudes.

[0013] Furthermore, the method for calculating ROTI and global DIXSG factor taking into account satellite elevation angle suppression is as follows:

[0014] A single geodetic receiver data is selected from the international GNSS service IGS to construct a receiver network dataset consisting of at least two receivers, and all visible satellite data observed within a preset time period are preprocessed: observations less than 10 epochs are regarded as too short arc segments and are eliminated; in order to optimize the efficiency of DIXSG factor calculation, the distance between any two geodetic receivers is limited to between 10 and 1000 kilometers; the satellite cut-off elevation angle is set to 20° to avoid interference from multipath effects; the dual-frequency undifferenced cycle slip processing method TurboEdit and the dual-frequency pseudorange and carrier combination method Hatch-Melbourne-Wübbena are used to detect and repair the cycle slips of dual-frequency and triple-frequency observations of co-located geodetic GNSS receivers respectively;

[0015] Calculate the rate of change of total electron content index ROTI: First, the slant path total electron content STEC value of each visible satellite in the monitoring period of a single receiver is calculated by the carrier phase smoothed pseudorange method. Then, the STEC value is used to assign different weights to the elevation angle of each visible satellite that can be observed by the GNSS receiver to weaken the adverse effects of satellite elevation angle interference:

[0016]

[0017]

[0018]

[0019] Where, the total electron content change rate ROT represents the temporal gradient change of STEC; M represents the weight mapping function; t represents the epoch; T represents the time in minutes; R E H represents the mean radius of curvature of the Earth ellipsoid; E It represents the assumed height of the ionosphere; E represents the altitude angle of the satellite visible to the GNSS side-to-ground receiver within a preset time period.

[0020] Calculate the global ionospheric disturbance spatial gradient index DIXSGt: First, calculate the gradient change cROT of the distance between adjacent epochs of ionospheric puncture points at the assumed ionospheric height H based on ROT, and then calculate the difference ΔDIXSG(cROT) between any two receiver stations in the preset time period. (level) ) and assign values:

[0021]

[0022]

[0023] Where cROT represents the gradient change of the distance between the ionospheric puncture points in adjacent epochs; i represents the receiver; k represents the satellite; Δs iIndicates the distance between adjacent epochs of ionospheric puncture points; cROT (level) Indicates the selectable recognition level, select L i (i=1, 2, 3, 4, 5)=50, 100, 150, 200 and 250 five constant data as initial sensitivity; ΔDIXSG(cROT (level) ) represents the difference in cROT between any two stations at this sensitivity; j represents the receiver; d represents the distance between the satellite and the ionospheric puncture point of receivers i and j; since the distance between any two receivers is limited to 10 to 1000 km, D is fixed to 1000 km. The assignment principle is as follows: According to the above formula, ΔDIXSG(cROT (level) (L i )) The value greater than 1 is assigned to 1, otherwise it is assigned to 0, which is convenient for drawing spatial variation maps. Finally, the global range is divided into 1°×1° longitude and latitude regions, and the ratio of the maximum ΔDIXSG sum in each region to the total number of effective regions is used to represent the global ionospheric disturbance spatial gradient index DIXSGt:

[0024]

[0025] Where N is the total number of all valid 1°×1° areas within 1 hour.

[0026] Furthermore, the spatial variation diagrams of ROTI and DIXSG factors for the world and a certain area to be studied are calculated:

[0027] The global range is divided into 1°×1° longitude and latitude regions, and the ROTI map is drawn based on the maximum ROTI value within the 1°×1° region within 1 hour:

[0028] ROTIp=ROTI (max(1°×1°))

[0029] The maximum ΔDIXSG value in the 1°×1° area within the preset time period represents the ionospheric space disturbance state DIXSGp on the earth's surface during the corresponding time period;

[0030] DIXSGp=ΔDIXSG (5-level,max(1°×1°))

[0031] Since the spatial resolution of 1°×1° is too coarse, an area to be studied is selected at high, medium and low latitudes respectively, and the spatial resolution of the area to be studied is set to 0.5°×0.5°, so as to ensure that the calculated DIXSG value is maximized and the scintillation disturbance state of the area can be effectively characterized. The ROTI map, disturbance state DIXSGr and time series area DIXSGt of the area to be studied are calculated:

[0032] ROTIr=ROTI (max(0.5°×0.5°))

[0033] DIXSGr=ΔDIXSG (5-level,max(0.5°×0.5°))

[0034]

[0035] Furthermore, the monitoring performance of DIXSG factor in monitoring global ionospheric scintillation is evaluated:

[0036] First, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, solar X-ray flares X-rays and coronal mass ejections CMEs are obtained from the agencies that provide space weather parameters to characterize space weather conditions.

[0037] After searching the data, select Dst<-30nT, Ap>22, X-ray>10 -5 W / m 2 The time period of CME>1080km / s is taken as the analysis interval of space weather disturbance, and the time series diagram of ROTI and DIXSG factors in this disturbance interval is drawn accordingly;

[0038] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIp and DIXSGp, were plotted with a time interval of 1 hour and a spatial resolution of 1°×1° longitude and latitude interval;

[0039] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation on a global scale; otherwise, it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation on a global scale.

[0040] Furthermore, the monitoring performance of the DIXSG factor in monitoring ionospheric scintillation in high-latitude regions is evaluated:

[0041] First, we selected high-latitude areas of 60 degrees and above as the research objects, and ensured that there were at least two or more side-land observation stations in the area;

[0042] Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and polar magnetic substorm intensity index AE are obtained through institutions that can provide space weather parameters to characterize space weather conditions;

[0043] Then, the time period of Dst<-30nT, Ap>22, and AE>300nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly;

[0044] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval;

[0045] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in high-latitude regions, otherwise it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in high-latitude regions.

[0046] Furthermore, the monitoring performance of DIXSG factor in monitoring ionospheric scintillation in mid-latitude regions was evaluated:

[0047] First, we selected the mid-latitude region between 30 and 60 degrees as the research object, and ensured that there were at least two or more lateral ground-type observation stations in the region;

[0048] Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and three-hour magnetic index Kp are obtained through institutions that can provide space weather parameters to characterize space weather conditions;

[0049] Then, the time period of Dst<-30nT, Ap>22, and Kp>300nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly;

[0050] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval;

[0051] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region, otherwise it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region.

[0052] Furthermore, the monitoring performance of the DIXSG factor in monitoring ionospheric scintillation in low-latitude regions is evaluated:

[0053] First, we selected the mid-latitude area between 0 and 30 degrees as the research object, and ensured that there were at least two or more side-land observation stations in the area;

[0054] Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and global equatorial H component SYM-H are obtained through institutions that can provide space weather parameters to characterize space weather conditions;

[0055] Then, the time period of Dst<-30nT, Ap>22, and SYM-H<-30nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly;

[0056] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval;

[0057] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region, otherwise it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region.

[0058] Beneficial effects: Compared with the existing time-series ionospheric scintillation monitoring research using ionospheric scintillation monitoring receivers, the geodetic GNSS receiver network data introduced in this method evaluates the DIXSG factor monitoring scintillation accuracy from the temporal and spatial aspects, greatly reducing the cost of ionospheric scintillation monitoring. Combined with the wide distribution of geodetic GNSS receivers, it is conducive to the complete monitoring of ionospheric scintillation in time and space on a global scale, and has wide practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 A schematic flow chart of the analytical method for evaluating the DIXSG factor to monitor global ionospheric scintillation performance according to the present invention. DETAILED DESCRIPTION

[0060] The embodiments of the present invention are further described below in conjunction with the accompanying drawings:

[0061] like Figure 1 As shown, the analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance of the present invention evaluates the scintillation monitoring performance of the DIXSG factor for the global geodetic GNSS receiver network data, and the steps are as follows:

[0062] a. Select two or more geodetic receiver network data in the international GNSS service IGS for data preprocessing: remove short arc segments, control altitude angles, and perform cycle slip detection and repair;

[0063] b. Estimate the total electron content (STEC) of the slant path using the carrier phase smoothed pseudorange method for the preprocessed data, and calculate the total electron content change rate index (ROTI) and the ionospheric disturbance spatial gradient index (DIXSG) of all visible satellite elevation angles observed by the GNSS receiver network data within a preset time period;

[0064] Preprocess all visible satellite data observed within a preset time period for the selected IGS network data. Observations with less than 10 epochs are considered as too short arc segments and are eliminated; in order to optimize the efficiency of DIXSG factor calculation, the distance between any two groups of receivers is limited to between 10 and 1000 kilometers; the satellite elevation angle is set to 20° to avoid interference from multipath effects; the dual-frequency undifferenced cycle slip processing method TurboEdit and the improved dual-frequency pseudorange and carrier combination method Hatch-Melbourne-Wübbena are used to detect and repair the cycle slips of dual-frequency and triple-frequency observations of co-located geodetic GNSS receivers respectively;

[0065] Calculate the total electron content rate of change index ROTI. First, the slant path total electron content STEC value of each visible satellite during the monitoring period is calculated by the carrier phase smoothed pseudorange method, and then the STEC value is used to assign different weights to the elevation angle of each visible satellite that the GNSS receiver can observe to weaken the adverse effects of satellite elevation angle interference:

[0066]

[0067]

[0068]

[0069] Where ROT represents the temporal gradient of STEC; t represents the epoch; T represents the time in minutes; R E H represents the mean radius of curvature of the Earth ellipsoid; E It represents the assumed height of the ionosphere; E represents the altitude angle of the satellite visible to the GNSS receiver within the preset time period.

[0070] Calculate the spatial gradient index DIXSG of ionospheric disturbance. First, calculate the gradient change cROT of the distance between adjacent epochs of ionospheric puncture points at the assumed ionospheric height H based on ROT, and then calculate the difference ΔDIXSG (cROT) between any two groups of stations in the preset time period. (level) ) and simplify it:

[0071]

[0072]

[0073] Where cROT represents the gradient change of the distance between the ionospheric puncture points in adjacent epochs; i represents the receiver; k represents the satellite; Δs i Indicates the distance between adjacent epochs of ionospheric puncture points; cROT (level) Indicates the selectable recognition level, and five sets of data of 50, 100, 150, 200 and 250 are selected as the initial sensitivity; ΔDIXSG(cROT (level) ) represents the difference in cROT between any two groups of stations at this sensitivity; j represents the receiver; d represents the distance between the satellite and the ionospheric puncture point of receivers i and j. Since the distance between any two groups of receivers is limited to 10 to 1000 km, D is fixed to 1000 km. The simplified principle is as follows: ΔDIXSG(cROT (level) (L)) values ​​greater than 1 are simplified to 1, otherwise simplified to 0. Finally, the research scope is divided into 1°×1° longitude and latitude regions according to the requirements, and the global DIXSG is expressed as the ratio of the sum of the maximum ΔDIXSG in each region to the total number of valid regions:

[0074]

[0075] Where N represents the total number of all valid 1°×1° areas over a period of time.

[0076] c The study area is divided into longitude and latitude grids, and the spatial variation maps of ROTI and DIXSG factors are calculated;

[0077] The global range is divided into 1°×1° longitude and latitude regions, and the ROTI map is drawn based on the maximum ROTI value within the 1°×1° region over a period of time:

[0078] ROTIp=ROTI (max(1°×1°))

[0079] The maximum ΔDIXSG value in the 1°×1° area within the preset time period represents the ionospheric space disturbance state DIXSGp on the earth's surface during the corresponding time period;

[0080] DIXSGp=ΔDIXSG (5-level,max(1°×1°))

[0081] The spatial resolution of high, mid and low latitude regions is positioned at 0.5° × 0.5°, and the regional ROTI map, disturbance state DIXSGr and time series regional DIXSG are calculated as follows:

[0082] ROTIr=ROTI (max(0.5°×0.5°))

[0083] DIXSGr=ΔDIXSG (5-level,max(0.5°×0.5°))

[0084]

[0085] d. Using ROTI maps, evaluate the monitoring performance of DIXSG factor in monitoring global ionospheric scintillation;

[0086] First, we obtain the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, solar X-ray flares X-rays and coronal mass ejections CMEs through institutions that can provide space weather parameters to characterize space weather conditions;

[0087] Reference Adekoya, BJ, & Chukwuma, VU (2017). Classification and quantification of solar wind driver gases leading to intense geomagneticstorms. Advances in Space Research, 61(1), 274-286. https: / / doi.org / 10.1016 / j.asr.2017.09.036 Set the threshold, then select Dst<-30nT, Ap>22, X-ray>10 -5 W / m 2 The time period of CME>1080km / s is taken as the analysis interval of space weather disturbance, and the time series diagram of ROTI and DIXSG factors in this disturbance interval is drawn accordingly;

[0088] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIp and DIXSGp, were plotted with a time interval of 1 hour and a spatial resolution of 1°×1° longitude and latitude interval;

[0089] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude variation trend of the DIXSG factor itself is consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation on a global scale; otherwise, it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation on a global scale.

[0090] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation on a global scale; otherwise, it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation on a global scale.

[0091] e Using ROTI maps, the monitoring performance of DIXSG factor in monitoring ionospheric scintillation in high latitudes is evaluated;

[0092] First, we selected high latitudes of 60 degrees and above in the northern hemisphere as the research object, and ensured that there were at least two or more GNSS monitoring stations in the area;

[0093] Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and polar magnetic substorm intensity index AE are obtained through institutions that can provide space weather parameters to characterize space weather conditions;

[0094] According to the literature: Adekoya, BJ, & Chukwuma, VU (2017). Classification and quantification of solar wind driver gases leading to intense geomagnetic storms. Advances in Space Research, 61(1), 274-286. https: / / doi.org / 10.1016 / j.asr.2017.09.036, the time period with thresholds of Dst<-30nT, Ap>22, and AE>300nT was selected as the analysis interval of space weather disturbance, and the time series of ROTI and DIXSG factors in this disturbance interval were drawn accordingly;

[0095] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval;

[0096] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in high-latitude regions, otherwise it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in high-latitude regions.

[0097] f. Using ROTI maps, evaluate the monitoring performance of DIXSG factor in monitoring ionospheric scintillation in mid-latitude regions;

[0098] First, we selected the mid-latitude areas between 30 and 60 degrees and above in the northern hemisphere as the research objects, and ensured that there were at least two or more GNSS monitoring stations in the area;

[0099] Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and three-hour magnetic index Kp are obtained through institutions that can provide space weather parameters to characterize space weather conditions;

[0100] Reference: Adekoya, BJ, & Chukwuma, VU (2017). Classification and quantification of solar wind driver gases leading to intense geomagnetic storms. Advances in Space Research, 61(1), 274-286. https: / / doi.org / 10.1016 / j.asr.2017.09.036 The time period with thresholds Dst<-30nT, Ap>22, and Kp>300nT was selected as the analysis interval of space weather disturbance, and the time series of ROTI and DIXSG factors in this disturbance interval were plotted accordingly;

[0101] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval;

[0102] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region, otherwise it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region.

[0103] g. Using ROTI maps, evaluate the monitoring performance of DIXSG factor in monitoring ionospheric scintillation in low latitudes;

[0104] First, we selected the mid-latitude areas between 0 and 30 degrees and above in the northern hemisphere as the research objects, and ensured that there were at least two or more GNSS monitoring stations in the area;

[0105] Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and global equatorial H component SYM-H are obtained through institutions that can provide space weather parameters to characterize space weather conditions;

[0106] Then, the time period of Dst<-30nT, Ap>22, and SYM-H<-30nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly;

[0107] Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval;

[0108] Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; if the trends are consistent, it is determined that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in the low-latitude region, otherwise it is determined that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in the low-latitude region.

Claims

1. The analytical method for evaluating the performance of DIXSG factor in monitoring global ionospheric scintillation is characterized in that the ability of DIXSG factor in monitoring ionospheric scintillation is evaluated for the data of the global GNSS geodetic receiver network. The steps are as follows: S1 selects at least two geodetic receivers from the international GNSS service IGS to form a network, generates a network data set from the network data of all geodetic receivers, and performs data preprocessing on the network data set: removing short arc segments, controlling altitude angles, and detecting and repairing cycle slips; S2 estimates the slant path total electron content STEC using the carrier phase smoothed pseudorange method for the preprocessed receiver network data set, and calculates the total electron content change rate index factor ROTI and the ionospheric disturbance spatial gradient index factor DIXSG of the receiver network data set suppressed by all visible satellite elevation angles within a preset time interval; S3 divides the global range into 1°×1° longitude and latitude grids, and divides the area to be studied into 0.5°×0.5° longitude and latitude grids, and calculates the spatial variation maps of ROTI factor and DIXSG factor respectively; S4 sorts the calculated ROTI factors by time and draws a time series diagram and a spatial variation map, evaluating the performance of the DIXSG factor in monitoring global ionospheric scintillation in time and space. The evaluation criteria include two aspects: Evaluate the monitoring performance of the DIXSG factor for global ionospheric scintillation monitoring; Evaluate the monitoring performance of DIXSG factor in monitoring ionospheric scintillation in the high, middle or low latitudes of the Earth, where the high latitudes are 60 degrees and above, the middle latitudes are 30 to 60 degrees, and the low latitudes are 0 to 30 degrees. Using the time and space variation map of ROTI factor, we can judge whether the amplitude trend and spatial distribution characteristics of DIXSG factor time series are consistent with ROTI factor. If they are consistent, it means that DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation; if they are inconsistent, it means that DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in a certain area. The temporal and spatial fluctuation trends of the ROTI factor and the DIXSG factor are utilized to evaluate the temporal and spatial scintillation monitoring performance of the DIXSG factor from multiple latitudes.

2. The analysis method for evaluating the DIXSG factor to monitor global ionospheric scintillation performance according to claim 1 is characterized in that: The method for calculating ROTI and global DIXSG factors taking into account satellite elevation angle suppression is as follows: A single geodetic receiver data is selected from the international GNSS service IGS to construct a receiver network dataset consisting of at least two receivers, and all visible satellite data observed within a preset time period are preprocessed: observations less than 10 epochs are regarded as too short arc segments and are eliminated; in order to optimize the efficiency of DIXSG factor calculation, the distance between any two geodetic receivers is limited to between 10 and 1000 kilometers; the satellite cut-off elevation angle is set to 20° to avoid interference from multipath effects; the dual-frequency undifferenced cycle slip processing method TurboEdit and the dual-frequency pseudorange and carrier combination method Hatch-Melbourne-Wübbena are used to detect and repair the cycle slips of dual-frequency and triple-frequency observations of co-located geodetic GNSS receivers respectively; Calculate the rate of change of total electron content index ROTI: First, the slant path total electron content STEC value of each visible satellite in the monitoring period of a single receiver is calculated by the carrier phase smoothed pseudorange method. Then, the STEC value is used to assign different weights to the elevation angle of each visible satellite that can be observed by the GNSS receiver to weaken the adverse effects of satellite elevation angle interference: Where, the total electron content change rate ROT represents the temporal gradient change of STEC; M represents the weight mapping function; t represents the epoch; T represents the time in minutes; R E H represents the mean radius of curvature of the Earth ellipsoid; E Indicates the assumed height of the ionosphere; E indicates the altitude angle of the visible satellite of the GNSS side-to-ground receiver within a preset time period; Calculate the global ionospheric disturbance spatial gradient index DIXSGt: First, calculate the gradient change cROT of the distance between adjacent epochs of ionospheric puncture points at the assumed ionospheric height H based on ROT, and then calculate the difference ΔDIXSG(cROT) between any two receiver stations in the preset time period. (level) ) and assign values: Where cROT represents the gradient change of the distance between the ionospheric puncture points in adjacent epochs; i represents the receiver; k represents the satellite; Δs i Indicates the distance between adjacent epoch ionospheric puncture points; cROT (level) Indicates the selectable recognition level, select L i (i=1, 2, 3, 4, 5)=50, 100, 150, 200 and 250 five constant data as initial sensitivity; ΔDIXSG(cROT (level) ) represents the difference in cROT between any two stations at this sensitivity; j represents the receiver; d represents the distance between the satellite and the ionospheric puncture point of the receivers i and j; since the distance between any two receivers is limited to 10-1000 km, D is fixed to 1000 km; the assignment principle is as follows: According to the above formula, ΔDIXSG(cROT (level) (L i )) The value greater than 1 is assigned to 1, otherwise it is assigned to 0, which is convenient for drawing spatial variation maps. Finally, the global range is divided into 1°×1° longitude and latitude regions, and the ratio of the maximum ΔDIXSG sum in each region to the total number of effective regions is used to represent the global ionospheric disturbance spatial gradient index DIXSGt: Where N is the total number of all valid 1°×1° areas within 1 hour.

3. The analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance according to claim 2 is characterized in that: Calculate the spatial variation map of ROTI and DIXSG factors for the world and a certain area to be studied: The global range is divided into 1°×1° longitude and latitude regions, and the ROTI map is drawn based on the maximum ROTI value within the 1°×1° region within 1 hour: WHEELS=WHEELS (max(1°×1°)) The maximum ΔDIXSG value in the 1°×1° area within the preset time period represents the ionospheric space disturbance state DIXSGp on the earth's surface during the corresponding time period; DIXSGp=ΔDIXSG (5-level，max(1°×1°)) Since the spatial resolution of 1°×1° is too coarse, an area to be studied is selected at high, medium and low latitudes respectively, and the spatial resolution of the area to be studied is set to 0.5°×0.5°, so as to ensure that the calculated DIXSG value is maximized and the scintillation disturbance state of the study area can be effectively characterized. The ROTI map, disturbance state DIXSGr and time series area DIXSGt of the area to be studied are calculated: BREAD=BREAD (max(0.5°×0.5°)) DIXSGr=ΔDIXSG (5-level，max(0.5°×0.5°)) 4. The analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance according to claim 3 is characterized in that: Evaluation of the DIXSG factor for monitoring global ionospheric scintillation performance: First, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, solar X-ray flares X-rays and coronal mass ejections CMEs are obtained from the agencies that provide space weather parameters to characterize space weather conditions. After searching the data, select Dst<-30nT, Ap>22, X-ray>10 -5 W / m 2 The time period of CME>1080km / s is taken as the analysis interval of space weather disturbance, and the time series diagram of ROTI and DIXSG factors in this disturbance interval is drawn accordingly; Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIp and DIXSGp, were plotted with a time interval of 1 hour and a spatial resolution of 1°×1° longitude and latitude interval; Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; If the trends are consistent, it is judged that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation on a global scale. Otherwise, it is judged that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation on a global scale.

5. The analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance according to claim 4 is characterized in that: Evaluation of the DIXSG factor in monitoring the performance of ionospheric scintillation in high latitudes: First, we selected the high-latitude area of ​​60 degrees and above as the research object, and ensured that there were at least two or more side-land observation stations in the area; Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and polar magnetic substorm intensity index AE are obtained through institutions that can provide space weather parameters to characterize space weather conditions; Then, the time period of Dst<-30nT, Ap>22, and AE>300nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly; Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval; Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; If the trends are consistent, it is judged that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in high-latitude regions. Otherwise, it is judged that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in high-latitude regions.

6. The analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance according to claim 4, characterized in that: Evaluation of the DIXSG factor for monitoring ionospheric scintillation in mid-latitude regions: First, the mid-latitude area between 30 and 60 degrees was selected as the research object, and it was ensured that there were at least two or more side-land type observation stations in the area; Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and three-hour magnetic index Kp are obtained through institutions that can provide space weather parameters to characterize space weather conditions; Then, the time period of Dst<-30nT, Ap>22, and Kp>300nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly; Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval; Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; If the trends are consistent, it is judged that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region. Otherwise, it is judged that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region.

7. The analysis method for evaluating the DIXSG factor to monitor the global ionospheric scintillation performance according to claim 4, characterized in that: Evaluation of the DIXSG factor for monitoring ionospheric scintillation in low-latitude regions: First, the mid-latitude area between 0 and 30 degrees was selected as the research object, and it was ensured that there were at least two or more side-land type observation stations in the area; Secondly, the global geomagnetic index Dst, global geomagnetic disturbance amplitude Ap, and global equatorial H component SYM-H are obtained through institutions that can provide space weather parameters to characterize space weather conditions; Then, the time period of Dst<-30nT, Ap>22, and SYM-H<-30nT is selected as the analysis interval of space weather disturbance, and the time series diagrams of ROTI and DIXSG factors in this disturbance interval are drawn accordingly; Again, the spatial variation maps of ROTI and DIXSG factors within the disturbance interval, ROTIr and DIXSGr, were plotted with a time interval of 1 hour and a spatial resolution of 0.5°×0.5° longitude and latitude interval; Finally, the temporal and spatial variations of the ROTI factor are used to determine whether the amplitude trend and spatial distribution characteristics of the DIXSG factor time series are consistent with the ROTI factor; If the trends are consistent, it is judged that the DIXSG factor can effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region. Otherwise, it is judged that the DIXSG factor cannot effectively characterize the disturbance degree of ionospheric scintillation in the mid-latitude region.

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