Method for eliminating long-term trend of total electron content of ionized layer based on GNSS (Global Navigation Satellite System) observation

Abstract

The invention discloses a GNSS observation-based method for eliminating the long-term trend of the total electron content of an ionized layer, and the method comprises the steps: extracting the inclined total electron content TEC observation data of a GNSS satellite before and after the disturbance of the ionized layer, and converting the total electron content TEC observation data into vertical TEC observation data; performing time sequence preprocessing on the vertical TEC observation data to obtain target TEC time sequence data; calculating a disturbance occurrence time range based on the target TEC time sequence data; in combination with the disturbance occurrence time range, performing TEC background observation preprocessing to obtain TEC original background observation during disturbance occurrence; calculating the long-term trend of the total electron content of the ionized layer in the disturbance generation period based on TEC original background observation in the disturbance generation period; and the long-term trend of total electron content during ionosphere disturbance is eliminated. The method can quickly and accurately eliminate the long-term trend of the total electron content during the ionosphere disturbance period, and improves the accuracy and reliability of ionosphere disturbance monitoring.

Description

Technical Field

[0001] The present invention belongs to the technical field of space physics, and in particular relates to a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation. Background Art

[0002] The ionosphere is located between the fully ionized magnetosphere and the completely neutral lower atmosphere. It is an important transitional region for the exchange of matter, energy and momentum between the spheres. In addition to the conventional background changes such as annual changes, seasonal changes and daily changes, the ionosphere is also susceptible to various extreme weather, space activities and human activities, which in turn produce abnormal structures such as ionospheric disturbances. The total electron content (TEC) observation obtained by the Global Navigation Satellite System (GNSS) inversion has the advantages of wide coverage, strong real-time observation, good temporal and spatial resolution, high measurement accuracy, and no weather influence. It is currently the most important means of ionospheric detection. The long-term trend items in the ionospheric TEC data are often formed by the combined effects of complex factors such as solar activity, geomagnetic activity and neutral atmospheric components, which interfere with the short-term changes of TEC. By eliminating these long-term trends, the TEC data can more truly reflect the short-term disturbances and abnormal changes of the ionosphere, which can provide a clearer and more accurate data basis for ionospheric scientific research.

[0003] Methods for eliminating the long-term trend of the total electron content of the ionosphere can generally be divided into background correction and direct correction. Background correction means that the long-term trend of the ionospheric TEC can be described by referring to the background value, using the GNSS observation data before and after the disturbance, and eliminating the diurnal and daily changes of the background ionosphere when the disturbance occurs by means of secondary difference, and estimating the TEC background trend before and after the disturbance. The direct correction method uses the TEC measured data to monitor the time range of the disturbance, and replaces the TEC observation data when the disturbance occurs with the connecting line of the disturbance boundary point to eliminate the influence of long-term trends and other non-disturbance factors. Both of the above methods have certain limitations. The background correction method can more accurately reflect the long-term change trend of the ionosphere, but the temporal and spatial range of the disturbance is related to the GNSS ground and satellite positions, and sufficient reference data is required to ensure the accuracy of the disturbance extraction range; the direct correction method can directly process the observation data without relying on external models or reference data, but it cannot accurately reflect the background changes of TEC during the disturbance.

[0004] Therefore, there is an urgent need for a method to eliminate the long-term trend of TEC based on GNSS observations, which combines the advantages of direct correction methods and background correction methods, to address the current limitations of eliminating the long-term trend of the total electron content of the ionosphere. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observations, which uses a direct correction method to monitor the time range of disturbance occurrence, and then uses the GNSS data reference background value method to eliminate the long-term trend of the total electron content during the ionosphere disturbance, so as to achieve the purpose of extracting ionosphere disturbances.

[0006] To achieve the above object, the present invention provides a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation, comprising:

[0007] Extracting the oblique ionospheric total electron content (TEC) observation data of the GNSS satellite before and after the ionospheric disturbance occurs, and converting the oblique ionospheric total electron content (TEC) observation data into vertical TEC observation data;

[0008] Performing time series preprocessing on the vertical TEC observation data to obtain target TEC time series data;

[0009] Calculating a disturbance occurrence time range based on the target TEC time series data;

[0010] Combined with the time range of the disturbance, TEC background observation preprocessing is performed to obtain the original TEC background observation during the disturbance period;

[0011] Based on the original TEC background observations during the period when the disturbance occurs, the long-term trend of the total electron content in the ionosphere during the period when the disturbance occurs is calculated;

[0012] Based on the original TEC background observations during the disturbance and the long-term trend of the total electron content in the ionosphere during the disturbance, the long-term trend of the total electron content in the ionosphere during the disturbance is eliminated.

[0013] Optionally, using a projection function to convert the oblique ionospheric total electron content TEC observation data into vertical TEC observation data includes:

[0014]

[0015] Among them, TEC S is the observed oblique TEC; TEC V is the vertical TEC; SF is the tilt factor; E i is the elevation angle at the puncture point; E 0 is the elevation angle at the receiver location; r e is the average radius of the Earth; h m is the ionospheric thin layer model height.

[0016] Optionally, performing time series preprocessing on the vertical TEC observation data to obtain target TEC time series data includes:

[0017]

[0018] Where x is the time after class normalization; y is the TEC time series after class normalization; τ 0 is the total duration of the TEC sequence, ζ 0 is the TEC background value.

[0019] Optionally, calculating the disturbance occurrence time range based on the target TEC time series data includes:

[0020] The sphere center is set at (x 0 ,y 0 ), with a radius of R 0 When the ball rolls over the normalized TEC time series, there is a contact point between the ball and the normalized TEC time series, and the ball rotates around the contact point. The ball rolls in the direction of increasing time t until it falls on the next contact point. The contact point between the ball and the normalized TEC time series (x 0 +Δx,y 0 +Δy):

[0021]

[0022]

[0023] Among them, α is the angle between the line connecting the two contact points and the radius of the ball; β is the complementary angle of α; θ is the angle between the horizontal line when the y value of the first contact point is fixed and the line connecting the two contact points; δ is the leading edge angle of the ball; Δx is the time step after class normalization; Δy is the step size of TEC after class normalization; R 0 is the radius of the sphere.

[0024] Optionally, in combination with the disturbance occurrence time range, TEC background observation preprocessing is performed to obtain the TEC original background observation during the disturbance occurrence period, including:

[0025] Normalize the TEC time series to XY space by class:

[0026]

[0027] Among them, (x 1 ,y 1 ) and (x 2 ,y 2 ) The corresponding point is (t 1 ,TEC 1 ), (t 2 ,TEC 2 ), the TEC value during the disturbance is TEC d ; τ 0 is the total duration of TEC sequence; is the TEC background value;

[0028] The original TEC background observation during the disturbance is obtained based on the average value of the GNSS vertical TEC data reference background two days before and after the disturbance:

[0029]

[0030] TEC Previous TEC is the TEC value between the start time and the end time of the disturbance one day before the disturbance occurs; TEC after is the TEC value between the start and end time of the disturbance one day after the disturbance occurs; TEC m is the original TEC background observation during the disturbance; TEC m1 ,TEC m2 TEC m The starting point value and the ending point value.

[0031] Optionally, based on the original TEC background observation during the disturbance, calculating the long-term trend of the total electron content in the ionosphere during the disturbance comprises:

[0032] The original TEC background observation during the disturbance is linearly transformed so that the starting point value of the original TEC background observation during the disturbance is TEC 1 , the end point value is TEC 2 , obtain the long-term trend of the total electron content in the ionosphere during the disturbance t :

[0033] TEC t =kTEC m +c

[0034]

[0035] Among them, TEC t is the long-term trend of the total electron content in the ionosphere during the disturbance; TEC m is the original TEC background observation during the disturbance; k is the slope of the linear transformation; c is the intercept of the linear transformation; TEC 2 For TEC timing and TEC m The end point value of the corresponding time range; TEC 1 For TEC timing and TEC m The starting point value of the corresponding time range; TEC m2 For TEC m The end point value of TEC m1 For TEC m The starting point value.

[0036] Optionally, the long-term trend of total electron content during periods of ionospheric disturbance removal includes:

[0037] DTEC=TEC d -TEC t

[0038] Where DTEC is the TEC value during the ionospheric disturbance that eliminates the long-term trend of the total electron content, and TEC d is the TEC value during the disturbance, TEC t is the long-term trend of the total electron content in the ionosphere during the disturbance.

[0039] Technical effect of the invention: The invention discloses a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observations, which can quickly and accurately eliminate the long-term trend of the total electron content during ionospheric disturbances, improve the accuracy and reliability of ionospheric disturbance monitoring, and have a profound impact on ionospheric scientific research and space weather monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0041] Figure 1 A schematic diagram of extracting the time range of occurrence of ionospheric disturbance calculated by an embodiment of the present invention;

[0042] Figure 2 A schematic flow chart of a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observations according to an embodiment of the present invention;

[0043] Figure 3 A schematic diagram of a long-term trend calculation of the total electron content during ionospheric disturbances calculated based on GNSS observation data according to an embodiment of the present invention;

[0044] Figure 4 It is a schematic diagram of ionospheric disturbance after eliminating the long-term trend of total electron content calculated based on GNSS observation data according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0046] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0047] like Figure 2 As shown, this embodiment provides a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation, including:

[0048] Extract the oblique ionospheric total electron content (TEC) observation data of the GNSS satellite before and after the ionospheric disturbance occurs, and convert the oblique ionospheric total electron content (TEC) observation data into vertical TEC observation data;

[0049] Perform time series preprocessing on vertical TEC observation data to obtain target TEC time series data;

[0050] Calculate the time range of disturbance occurrence based on the target TEC time series data;

[0051] Combined with the time range of disturbance occurrence, TEC background observation preprocessing is performed to obtain the original TEC background observation during the disturbance period;

[0052] Based on the original TEC background observations during the disturbance period, the long-term trend of the total electron content in the ionosphere during the disturbance period is calculated;

[0053] Based on the original TEC background observations during the disturbance and the long-term trend of the total electron content in the ionosphere during the disturbance, the long-term trend of the total electron content in the ionosphere during the disturbance is eliminated.

[0054] Furthermore, the projection function is used to convert the oblique ionospheric total electron content TEC observation data into vertical TEC observation data, including:

[0055]

[0056] Among them, TEC S is the observed oblique TEC; TEC V is the vertical TEC; SF is the tilt factor; E i is the elevation angle at the puncture point; E 0 is the elevation angle at the receiver location; r e is the average radius of the Earth; h m is the ionospheric thin layer model height.

[0057] Furthermore, the vertical TEC observation data is preprocessed to obtain the target TEC time series data, including: unifying the ionospheric disturbance observation into the disturbance of TEC decrease, if the ionospheric disturbance is the disturbance of TEC rapid increase, the TEC value takes a negative sign; in addition, the TEC time series class is normalized to the XY space by using the total duration of the TEC time series and the TEC background value, so that the TEC time series data is limited to a certain range:

[0058]

[0059] Where x is the time after class normalization; y is the TEC time series after class normalization; τ 0 is the total duration of the TEC sequence, is the TEC background value.

[0060] Further, such as Figure 1 The disturbance occurrence time range calculated based on the target TEC time series data includes:

[0061] Set the sphere center at (x 0 ,y 0 ), with a radius of R 0 When the ball rolls over the normalized TEC time series, there is a contact point between the ball and the normalized TEC time series, and the ball rotates around the contact point. The ball rolls forward until it falls on the next contact point. The contact point between the ball and the normalized TEC time series (x 0 +Δx,y 0 +Δy):

[0062]

[0063]

[0064] Among them, α is the angle between the line connecting the two contact points and the radius of the ball; β is the complementary angle of α; θ is the angle between the horizontal line when the y value of the first contact point is fixed and the line connecting the two contact points; δ is the leading edge angle of the ball; Δx is the time step after class normalization; Δy is the step size of TEC after class normalization; R 0 is the radius of the sphere. During the non-disturbance period, the contact points have the same timing as the TEC; during the disturbance period, there is a long time span between adjacent contact points. The starting point of the disturbance is (x 1 ,y 1 ), the end point is (x 2 ,y 2 ).

[0065] α, β, θ and δ are angles, Δx is positive, all angles are in radians, α∈[0,π], θ∈[-π / 2,π / 2], δ∈[-π,π]. According to the geometric relationship, the next contact point is the contact point with the smallest angular distance δ relative to the leading edge of the ball. If the next contact point is located at 2R 0 In addition, specify more than 2R 0 The first data point outside is the next contact point. During the non-disturbance period, the contact points have the same timing as the TEC; during the disturbance period, the TEC drops rapidly, resulting in a long time span between adjacent contact points. The starting point of the disturbance is (x 1 ,y 1 ), the end point is (x 2 ,y 2 ).

[0066] Furthermore, combined with the time range of the disturbance, TEC background observation preprocessing is performed to obtain the original TEC background observation during the disturbance period, including:

[0067] Normalize the TEC time series to XY space by class:

[0068]

[0069] Among them, (x 1 ,y 1 ) and (x 2 ,y 2 ) The corresponding point is (t 1 ,TEC 1 ), (t 2 ,TEC 2 ), the TEC value during the disturbance is TEC d ; τ 0 is the total duration of the TEC sequence; 0 is the TEC background value;

[0070] The original TEC background observation during the disturbance is obtained based on the average value of the GNSS vertical TEC data reference background two days before and after the disturbance:

[0071]

[0072] TEC Previous TEC is the TEC value between the start time and the end time of the disturbance one day before the disturbance occurs; TEC after is the TEC value between the start and end time of the disturbance one day after the disturbance occurs; the original TEC background observation during the disturbance is recorded as TEC m ;TEC m1 ,TEC m2 TEC mThe starting point value and the ending point value.

[0073] Furthermore, based on the original TEC background observations during the disturbance, the long-term trend of the total electron content in the ionosphere during the disturbance is calculated, including:

[0074] The TEC m Do a linear transformation so that TEC m The starting point value is TEC 1 , the end point value is TEC 2 , obtain the long-term trend of the total electron content in the ionosphere during the disturbance t :

[0075] TEC t =kTEC m +c

[0076]

[0077] Among them, TEC t is the long-term trend of the total electron content in the ionosphere during the disturbance; TEC m is the original TEC background observation during the disturbance; k is the slope of the linear transformation; c is the intercept of the linear transformation; TEC 2 For TEC timing and TEC m The end point value of the corresponding time range; TEC 1 For TEC timing and TEC m The starting point value of the corresponding time range; TEC m2 For TEC m The end point value of TEC m1 For TEC m The starting point value.

[0078] Furthermore, the long-term trend of total electron content during the period of eliminating ionospheric disturbances includes:

[0079] DTEC=TEC d -TEC t

[0080] Where DTEC is the TEC value during the ionospheric disturbance that eliminates the long-term trend of the total electron content, and TEC d is the TEC value during the disturbance, TEC t is the long-term trend of the total electron content in the ionosphere during the disturbance.

[0081] An application example of this embodiment is:

[0082] Taking the measured data of a GNSS observation station on December 7, 2014 as an example, the Long March 4B carrier rocket launched at 03:26:04 UT on that day injected exhaust gas into the ionosphere, causing a significant decrease in the total electron content of the ionosphere near the rocket track. In order to eliminate the long-term trend of the total electron content during the ionospheric disturbance on that day and obtain the TEC change value caused by the ionospheric disturbance, taking the observation information of a GNSS station and the 10th satellite at 03:20:00 UT as an example, perform the following steps:

[0083] Extract the oblique TEC observation data of the GNSS satellite and use the projection function to convert the oblique TEC into vertical TEC: Take the two target times of 03:26:04 (the time of rocket launch, that is, the time when ionospheric disturbance has not yet occurred) and 03:31:01 (the time when TEC begins to drop rapidly) as examples. The oblique TEC values ​​observed by GNSS at 03:26:04 and 03:31:01 are TEC respectively. S01 =39.252621138615800TECU and TEC S02 =39.672895715650380TECU, the elevation angle E at the receiver position 0 E 01 =0.9462 and E 02 =0.9103. The average radius of the earth is r e Take 6378km, the height of the ionosphere thin layer model h m Take 350km and use the projection function to convert the oblique TEC to vertical TEC:

[0084]

[0085] TEC timing preprocessing: Normalize the TEC timing class to XY space, τ 0 Take 2h, ζ 0 Take 40TECU. Take the TEC values ​​of 03:26:04 and 03:31:01 UTC as an example:

[0086]

[0087] Calculate the contact point: take the radius R 0 = 0.5. The time before the disturbance occurs: 03:26:04 UT (x 01 ,y 01 ) and the moment when TEC began to drop rapidly: 03:31:01 and (x 02 ,y 02 ) as an example:

[0088] (1) Calculate the time when the ionospheric disturbance has not yet occurred (x 01 ,y01 )'s next touchpoint:

[0089] (x 01 ,y 01 ) and the first moment after (x 01_next1 ,y 01_next1 ) is: Δx 01_1 =1.3888888888889106×10 -4 , Δy 01_1 =1.503571014093152×10 -4 .

[0090]

[0091] δ 01_1 =β 01_1 -θ 01_1 =-0.824821366604825,

[0092] (x 01 ,y 01 ) and the second moment after (x 01_next2 ,y 01_next2 ) is: Δx 01_2 =2.7777777777778212×10 -4 , Δy 01_2 =-8.561414517538335×10 -4 .

[0093]

[0094] δ 01_2 =β 01_2 -θ 01_2 =0.299263296368674,

[0095] (x 01 ,y 01 ) and the 3933th moment (x 01_next3933 ,y 01_next3933 ) is:

[0096] Δx 01_3933 =0.546250000000000, Δy 01_3933 =-0.030083169546805.

[0097]

[0098] δ 01_3933 =β 01_3933 -θ 01_3933=0.633885824937236

[0099] Calculate (x 01 ,y 01 ) and then 2R 0 Within the range, the leading edge angle v of a total of 3933 moments 01_1 to δ 01_3933 , after calculation, we get 01_1 is the minimum value, that is, (x 01 ,y 01 ) is the next contact point at the next moment (x 01_next1 ,y 01_next1 ).

[0100] (2) Calculate the time when TEC begins to drop rapidly (x 02 ,y 02 )'s next touchpoint:

[0101] (x 02 ,y 02 ) and the first moment after (x 02_next1 ,y 02_next1 ) is: Δx 02_1 =1.3888888888889106×10 -4 , Δy 02_1 =-0.007534892018917.

[0102]

[0103] δ 02_1 =β 02_1 -γ 02_1 =1.559901892946139.

[0104] (x 02 ,y 02 ) and the second moment after (x 02_next2 ,y 02_next2 ) is: Δx 02_2 =2.7777777777778212×10 -4 , Δy 02_2 =-0.024166831198669.

[0105]

[0106] δ 02_2 =β 02_2 -θ 02_2 =1.583473439350501.

[0107] (x 02 ,y02 ) and the 2654th moment after that (x 02_next2654 ,y 02_next2654 ) is: Δx 02_2654 =0.368611111111111, Δy 02_2654 =-0.053589760385010.

[0108]

[0109] δ 02_2654 =β 02_2654 -θ 02_2654 =0.526058073413885.

[0110] (x 02 ,y 02 ) and the 3636th moment (x 02_next3636 ,y 02_next3636 ) is: Δx 02_3636 =0.505000000000000, Δy 02_3636 =-0.020173451757626.

[0111]

[0112] δ 02_3636 =β 02_3636 -θ 02_3636 =0.569774883335386

[0113] Calculate (x 02 ,y 02 ) and then 2R 0 Within the range, the leading edge angle δ of a total of 3636 moments 02_1 to δ 02_3636 , after calculation, we get 02_2654 is the minimum value, that is, (x 02 ,y 02 ) is the next contact point 2654 moments later (x 02_next2654 ,y 02_next2654 ).

[0114] The above calculation proves that during the non-disturbance period, the contact points have the same timing as the TEC; during the disturbance period, there is a long time span between adjacent contact points. The starting point of the disturbance is (x 02 ,y 02 ), the end point is (x 02_next2654 ,y 02_next2654 );

[0115] TEC background observation preprocessing: normalize the contact points obtained in the previous step by inverse class, taking the starting point of the disturbance as (x 02 ,y 02 ) and the end point (x 02_next2654 ,y 02_next2654 ) as an example:

[0116]

[0117] Get the starting point of disturbance in TEC time series: (t 02 ,TEC 02 ),lie in Figure 3 The beginning of the middle dashed line; the perturbation termination point in the TEC time series: (t 02_next2654 ,TEC 02_next2654 ),lie in Figure 3 The end of the middle dashed line. The TEC value during the disturbance is TEC d ,for Figure 3 The background value of GNSS vertical TEC data two days before and after the disturbance is Figure 3 Medium fine line, Figure 3 The thin line at the bottom is the vertical TEC data of the day before the disturbance. Previous , Figure 3 The thin line on the top is the vertical TEC data one day after the disturbance occurred. after The vertical TEC data before and after the disturbance are added and averaged. Denoted as TEC m TEC m The starting point is the TEC data background value at the beginning of the disturbance, denoted as TEC m1 =31.548326846658036TECU;TEC m The end of the disturbance is the TEC data background value at the end of the disturbance, denoted as TEC m2 =29.943995178658910TECU.

[0118] Calculate the long-term trend of the total electron content in the ionosphere during the disturbance: m Do a linear transformation so that TEC m1 =TEC 02 ,TEC m2 =TEC 02_next2654 ;

[0119]

[0120] Obtain the long-term trend of the total electron content in the ionosphere during the disturbance period t =kTEC m +c, for Figure 3 Middle dotted line.

[0121] Obtain the TEC change value DTEC=TEC after eliminating the long-term trend of the total electron content during the ionospheric disturbance d -TEC t ,for Figure 4 Middle solid line.

[0122] like Figure 3 As shown, the method of this embodiment is used to calculate the long-term trend of the ionospheric disturbance caused by rocket exhaust based on the actual measurement data of satellite No. 10 on December 7, 2014 at a certain GNSS observation station. Figure 3 The middle dashed line is the long-term trend of the total electron content during the ionospheric disturbance. Figure 4 This is the TEC value after eliminating the long-term trend of the total electron content during the ionospheric disturbance. It can be seen that using GNSS observations to eliminate the long-term trend of the total electron content during the ionospheric disturbance clearly shows the decrease in TEC during the ionospheric disturbance, and can effectively extract the ionospheric disturbance.

[0123] The present invention discloses a method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observations, which can quickly and accurately eliminate the long-term trend of the total electron content during ionospheric disturbances, improve the accuracy and reliability of ionospheric disturbance monitoring, and have a profound impact on ionospheric scientific research and space weather monitoring.

[0124] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observations, characterized in that: include: Extracting the oblique ionospheric total electron content (TEC) observation data of the GNSS satellite before and after the ionospheric disturbance occurs, and converting the oblique ionospheric total electron content (TEC) observation data into vertical TEC observation data; Performing time series preprocessing on the vertical TEC observation data to obtain target TEC time series data; Calculating a disturbance occurrence time range based on the target TEC time series data; Combined with the time range of the disturbance, TEC background observation preprocessing is performed to obtain the original TEC background observation during the disturbance period; Based on the original TEC background observations during the period when the disturbance occurs, the long-term trend of the total electron content in the ionosphere during the period when the disturbance occurs is calculated; Based on the original TEC background observations during the disturbance and the long-term trend of the total electron content in the ionosphere during the disturbance, the long-term trend of the total electron content in the ionosphere during the disturbance is eliminated.

2. The method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation as claimed in claim 1, characterized in that: The projection function is used to convert the oblique ionospheric total electron content TEC observation data into vertical TEC observation data, including: Among them, TEC S is the observed oblique TEC; TEC V is the vertical TEC; SF is the tilt factor; E i is the elevation angle at the puncture point; E0 is the elevation angle at the receiver position; r e is the average radius of the Earth; h m is the ionospheric thin layer model height.

3. The method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation as claimed in claim 1, characterized in that: Performing time series preprocessing on the vertical TEC observation data to obtain target TEC time series data includes: Among them, x is the time after class normalization; y is the TEC time series after class normalization; τ0 is the total time length of the TEC time series, is the TEC background value.

4. The method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation as claimed in claim 1, characterized in that: The disturbance occurrence time range calculated based on the target TEC time series data includes: A ball with a center at (x0, y0) and a radius of R0 is set above the target TEC time series data. When the ball rolls over the class-normalized TEC time series, there is a contact point between the ball and the class-normalized TEC time series, and the ball rotates around the contact point. The ball rolls in the direction of increasing time t until it falls on the next contact point. The contact point between the ball and the class-normalized TEC time series is calculated (x0+Δx, y0+Δy): Among them, α is the angle between the line connecting the two contact points and the radius of the ball; β is the complementary angle of α; θ is the angle between the horizontal line when the y value of the first contact point is fixed and the line connecting the two contact points; δ is the leading edge angle of the ball; Δx is the time step after class normalization; Δy is the step size of TEC after class normalization; R0 is the radius of the ball.

5. The method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation as claimed in claim 1, characterized in that: Combined with the time range of the disturbance, TEC background observation preprocessing is performed to obtain the original TEC background observation during the disturbance period, including: Normalize the TEC time series to XY space by class: Among them, the corresponding points of (x1, y1) and (x2, y2) are (t1, TEC1) and (t2, TEC2), and the TEC value during the disturbance is TEC d ;τ0 is the total duration of TEC sequence; is the TEC background value; The original TEC background observation during the disturbance is obtained based on the average value of the GNSS vertical TEC data reference background two days before and after the disturbance: TEC Previous TEC is the TEC value between the start time and the end time of the disturbance one day before the disturbance occurs; TEC after is the TEC value between the start and end time of the disturbance one day after the disturbance occurs; TEC m is the original TEC background observation during the disturbance; TEC m1 ,TEC m2 TEC m The starting point value and the ending point value.

6. The method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation as claimed in claim 1, characterized in that: Based on the original TEC background observations during the disturbance, the long-term trend of the total electron content in the ionosphere during the disturbance is calculated, including: The original TEC background observation during the disturbance is linearly transformed so that the starting point value of the original TEC background observation during the disturbance is TEC1 and the ending point value is TEC2, and the long-term trend of the total electron content in the ionosphere during the disturbance is obtained. t : TEC t =kTEC m +c Among them, TEC t is the long-term trend of the total electron content in the ionosphere during the disturbance; TEC m is the original TEC background observation during the disturbance; k is the slope of the linear transformation; c is the intercept of the linear transformation; TEC2 is the TEC time series and TEC m The end point value of the corresponding time range; TEC1 is the TEC timing and TEC m The starting point value of the corresponding time range; TEC m2 For TEC m The end point value of TEC m1 For TEC m The starting point value.

7. The method for eliminating the long-term trend of the total electron content of the ionosphere based on GNSS observation as claimed in claim 1, characterized in that: Long-term trends in total electron content during the period of ionospheric disturbance removal include: DTEC=TEC d -TEC t Where DTEC is the TEC value during the ionospheric disturbance that eliminates the long-term trend of the total electron content, and TEC d is the TEC value during the disturbance, TEC t is the long-term trend of the total electron content in the ionosphere during the disturbance.

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