New ionosphere modeling technology based on continuity equation and Beidou synchronous orbit satellite constraint

Abstract

The invention provides a novel ionosphere modeling technology based on a continuity equation and Beidou synchronous orbit satellite constraint, and relates to the technical field of ionosphere monitoring. Comprising the following steps: step 1, an ionosphere modeling method based on a continuity equation, step 2, constructing constraint conditions by using Beidou synchronous orbit satellite observation data, and step 3, establishing a high-precision ionosphere TEC model based on the constraint conditions so as to solve the problem of insufficient precision of an existing ionosphere function model. The ionosphere continuity equation reflects two physical processes of a photochemical reaction and a transportation process in the ionosphere, the physical law of ionosphere activity can be effectively considered by introducing the ionosphere continuity equation into the ionosphere model, meanwhile, continuous monitoring data of Beidou synchronous orbit satellite data on TEC at a part of IPP is introduced, a synchronous orbit satellite IPP point serves as a stable point, and the stability of the ionosphere is improved. Constraint conditions of the ionosphere model are established, and the accuracy of ionosphere TEC inversion and the sensitivity of ionosphere disturbance detection are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ionosphere monitoring, and in particular to a new ionosphere modeling technology based on continuity equations and Beidou synchronous orbit satellite constraints. Background Art

[0002] As an important part of the solar-terrestrial space environment, the ionosphere has a significant impact on human activities such as satellite navigation and positioning, aerospace, and radio communications. At present, the vigorous development of the Global Navigation Satellite System (GNSS) has made it the main means of ionospheric detection. Compared with traditional ionospheric detection technology, GNSS has the advantages of all-weather, global coverage, high temporal and spatial resolution, high accuracy, and low cost. The importance of GNSS ionospheric monitoring is reflected in its significant contribution to improving the accuracy of the global positioning system, optimizing the effect of radio wave communication, and improving the accuracy of space weather forecasts. By accurately measuring and updating the ionospheric state in real time, the accuracy of navigation and positioning can be improved and the quality of communication can be guaranteed. The accuracy of GNSS ionospheric monitoring is directly related to the adopted ionospheric model. Therefore, it is necessary to establish a high-precision ionospheric model.

[0003] The existing ionosphere model still has the following defects, which are specifically reflected in: 1. The existing ionospheric function models are mainly based on fitting and approximation by mathematical methods such as polynomials, spherical harmonic functions, and trigonometric series, without taking into account the physical characteristics and laws of ionospheric activities.

[0004] 2. GNSS satellites move at high speed relative to the ground, and the line of sight (LOS) between the satellite and the ground receiver changes dynamically, resulting in the IPP position being different at each epoch, making it difficult to continuously monitor the TEC at the same location. The consistency of modeling data at different times is poor, resulting in unsatisfactory fitting accuracy of the existing ionospheric model.

[0005] 3. In practical applications, the existing technology generally uses the least squares method to estimate the ionospheric model coefficients, which only takes into account the size of the comprehensive error and does not consider the fitting accuracy at a single IPP, which may lead to a large local fitting deviation of the model. Summary of the invention

[0006] The purpose of the present invention is to provide a new ionospheric modeling technology based on continuity equations and Beidou synchronous orbit satellite constraints, which solves the problems existing in the background technology.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solution: The present invention provides a new ionospheric modeling technology based on the continuity equation and Beidou synchronous orbit satellite constraints, which is characterized by comprising: Step 1: Ionosphere modeling method based on continuity equation.

[0008] Step 2: Use BeiDou synchronous orbit satellite observation data to construct constraints.

[0009] Step 3: Establish a high-precision ionospheric TEC model based on constraints.

[0010] As a preferred solution, the new ionospheric modeling technology based on the continuity equation and Beidou synchronous orbit satellite constraints is characterized in that the step 1: the ionospheric modeling method based on the continuity equation, the specific analysis method is: The physical processes of the ionosphere can be roughly divided into two types: photochemical processes and transport processes. The ionosphere continuity equation derived from these processes is: ,in represents the rate of change of electron concentration, where N is the electron concentration, t is time, q is the electron generation rate, L(N) is the electron loss rate, NV represents the flux of charged particles generated by the transport process, and V is the net drift velocity. represents the divergence of NV.

[0011] Solar far ultraviolet radiation and X-ray radiation act on the neutral atmosphere, ionizing neutral atmospheric particles and generating ion-electron pairs. Assuming X is a microscopic particle of a certain atmospheric component, according to the law of mass action: ,in represents photons, and e represent positively charged ions and electrons respectively, thus producing positive ions and free electrons in the ionosphere, and the above reaction is a reversible process, which is a photochemical process. The process includes two key factors that cause changes in electron concentration: the generation rate and the loss rate.

[0012] As a preferred solution, the new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints is characterized in that the generation rate is specifically analyzed by the following method: Assume that the production rate of a single gas is: ,in , , , They represent the generation rate, ionization efficiency, absorption area, and gas density of the i-th gas, respectively. is the solar radiation flux, which is processed by averaging, namely: ,in , , , Denote the average generation rate, average ionization efficiency, average absorption area, and average gas density in the local area of ​​the ionosphere. , then (4) can be simplified to: .

[0013] set up is the zenith angle of solar radiation. Assuming that solar radiation is uniformly irradiated on the single-layer model of the ionosphere, the amount of solar radiation received per unit area of ​​the ionosphere is only related to the incident angle and radiation intensity. If the solar radiation flux is , the solar radiation flux actually received by the ionosphere per unit area It can be expressed as , the functional relationship between the average generation rate and the solar radiation intensity can be obtained from equations (5) and (6), as shown in equation (7): .

[0014] As a preferred solution, the new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints is characterized in that the loss rate is specifically analyzed by: The loss rate of charged particles in the ionosphere, L(N), is determined by the type and reaction rate of the photochemical reaction in the ionosphere. For the convenience of explanation, X and Y are used to represent neutral particles, and , Respectively represent positive and negative ions, represents ions in a certain excited state, then there are main ion reactions in the ionosphere as shown in equations (8) to (12): Ion-atom exchange: .....(8) Ion-ion complexation: .....(9) Ion-electron recombination: 1) Decomposition type: .....(10) 2) Radiation type: 3) Tritype: .....(12) Among the types of ion-electron recombination reactions, the radiation type is not easy to satisfy the conservation of energy and momentum at the same time, so the reaction speed is very slow. In the three-body reaction, M is a catalyst, and the concentration of the catalyst affects the reaction speed. In fact, the three-body reaction rate coefficient is proportional to the square of the atmospheric concentration. This type of reaction is only obvious in the D layer of the ionosphere, and the decomposition and recombination to generate two material particles is easy to satisfy the conservation of energy. The reaction speed is 5 orders of magnitude greater than the radiation type. It is the main recombination reaction in the ionosphere. In fact, the loss process of most electrons and ions in the ionosphere goes through two processes: 1) Ion-atom exchange: .....(13) 2) Decomposition and compounding: .....(14) When the main component of the charged particles is molecular ions, the electron loss is determined by the decomposition and recombination reaction, see formula (14), which satisfies the square law loss formula: .....(15), where is the composite coefficient, is the concentration of molecular or atomic positive ions, and N is the electron concentration. Since the ionosphere is electrically neutral as a whole, we have: .....(16), then equation (15) can be transformed into: .....(17).

[0015] When the charged ions are mainly atomic ions, the ion-atom exchange reaction is the main process of electron loss, satisfying the linear loss formula: .....(18), where The adhesion coefficient represents the linear response.

[0016] Since the two loss processes exist simultaneously but their reaction speeds are different at different altitudes, the electron loss of the entire ionosphere is controlled by equations (17) and (18), and the composite coefficient and adhesion coefficient Temperature dependent, assuming square law losses account for % of total losses , then the linear loss accounts for , therefore, the comprehensive ionospheric loss rate can be expressed as: .....(19), among which, Dependent on the height, when the ionosphere single-layer model is determined, the height of the single-layer model is fixed. is a constant, let , , then the functional relationship between the loss rate and the electron concentration can be obtained by simplifying formula (19), as shown in formula .....(20), From formula (20), it can be seen that the electron loss rate in the ionosphere is a quadratic function of the electron concentration.

[0017] As a preferred solution, the new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints is characterized in that the specific analysis method of the transportation process is: The transport term in the continuity equation (1) is caused by various forces that cause the movement of charged particles, thereby changing the concentration of free electrons. The transport term can be expanded as: .....(21), where u, v, and w are the components of the charge velocity V in the x, y, and z directions, respectively. The x-axis is parallel to the geomagnetic meridian and is positive toward the north, the y-axis is parallel to the geomagnetic latitude and is positive toward the east, and the z-axis is vertical and is positive downward. Under assumption 5, ignoring the viscosity of particles, electron-ion collisions, gravity, and the effects of pressure gradient, the motion equation of charged particles in the ionosphere can be simplified as follows: , U is the neutral atmospheric motion speed, V is the net drift speed of charged particles, m is the particle mass, is the collision frequency of charged particles with neutral particles, Charge the particles.

[0018] Assume that the total driving force on the electron is F=( , , ),in, , , are the components of the total driving force in the three coordinate directions respectively. Assuming the magnetic field intensity at any position is B, and the angle between it and the single-layer model (magnetic inclination) is ζ, the moving speed of the charged particles in the three coordinate directions can be obtained as follows: , where Ω is the magnetic rotation frequency related to the geomagnetic intensity, charge mass, and charge, and its expression is .....(twenty four).

[0019] Under the assumption of a single-layer model, the vertical motion of charged particles can be ignored, and equation (21) can be rewritten as: .....(25), from (25), we can see that the transport term is related to the electron concentration N, the horizontal motion speed u, v. Since the divergence of the electron or ion flux is also a physical characteristic of ionospheric activity, under the condition of assumption 4, the transport term in a short time and small range can be regarded as a constant, set as ,Right now: .....(26).

[0020] Under the condition of assumption 2, the change of electron concentration within a certain period of time is Ignoring the above, after substituting formulas ), (7), (20), and (26) into the ionospheric continuity equation (1), we can obtain: .....(27), Formula (27) can be regarded as a second-order polynomial about the electron concentration N, and the solution of the equation can be expressed as: .....(28).

[0021] Assume that the solar altitude angle is θ, the solar declination is δ, the geographical latitude of the observation location is represented by B, the geographical longitude is L, t is the local time, and λ is the hour angle of the local time. The calculation formula of the solar altitude angle can be expressed as formula (29): .....(29), Substituting formula (29) into formula (28), we can get: ....(30), .....(31), where DOY represents the accumulated days per year. Since the solar radiation received by the night hemisphere is very weak, when the solar hour angle λ satisfies (λ<-90°,λ>90°), the solar radiation flux received by the ionosphere can be considered to be zero, that is, , at this time, the first formula of formula (30) will be further simplified to obtain the night model function expression of the model, because , are parameters related to the composite coefficient and the attachment coefficient, respectively. It can be judged that they are non-negative numbers. Since the electron content is also non-negative, after rearranging equation (30), the final function expression of the new ionosphere model can be obtained, as shown in equation (32). (32).

[0022] As a preferred solution, the new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints is characterized in that the step 2: using Beidou synchronous orbit satellite observation data to construct constraint conditions, the specific analysis method is: Assume that the ionosphere is a spherical shell with a thickness of 0. All electrons are concentrated on this spherical shell. See the schematic diagram for details. Figure 3 Under this assumption, the vertical total electron content VTEC is obtained using the mapping function, and the calculation formula is: ...(33), where Re is the mean radius of the Earth, Z' is the zenith distance of the puncture point, E is the satellite altitude, H is the effective height of the single-layer model, VTEC represents the vertical total electron content, Represent the hardware delay of the satellite and receiver respectively.

[0023] Since the BeiDou synchronous orbit satellite GEO can continuously monitor the total electron content TEC at a fixed position in the ionosphere, the monitoring data quality of the GEO satellite IPP is better than that of general medium-orbit satellites. Therefore, assuming that the VTEC penetrated by the GEO satellite is the accurate value of the zenith total electron content, formula (33) can be rewritten as: .....(32), among which, is the total electron content at the zenith at the GEO satellite penetration point, is the phase-smoothed pseudorange observation value of the GEO satellite, is the hardware delay of the GEO satellite.

[0024] The electron content at the GEO satellite IPP is used to establish constraints: = .....(33), among which, Represents the ionosphere at a certain epoch The zenithal total electron content at position, is the latitude of a GEO satellite puncture point, is the longitude of a GEO satellite puncture point.

[0025] As a preferred solution, the new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints is characterized in that the step three: establishing a high-precision ionospheric TEC model based on constraint conditions, and the specific analysis method is: According to formula (32), the electron concentration can be expressed as a function of the geographical location and the solar hour angle, namely: .....(34), where B is the latitude of the puncture point, is the solar hour angle. Combining the constraint condition (33) and the least squares method, the functional expression of the ionospheric modeling algorithm integrating the Beidou synchronous orbit satellite data constraints can be obtained as follows: .....(35), where V represents the residual value, P is the unit weight matrix, The specific expression of is shown in formula (32).

[0026] The electron concentration data at the IPP is calculated by using BeiDou observation data. Then, combined with the constraints of the second and third equations in equation (35), the value in equation (32) is obtained. , , , , The five model coefficients realize the construction of the ionospheric model based on the continuity equation and Beidou synchronous orbit satellite constraints.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. The ionosphere model is constructed using the continuity equation, which takes into account the three physical processes of electron generation rate, loss rate and transport process in the ionosphere. It can more accurately describe the activity laws of the ionosphere and improve the accuracy of the ionosphere model.

[0028] 2. Using BeiDou synchronous orbit satellites to monitor ionospheric disturbances can achieve continuous monitoring of electron concentrations at some IPP locations, improve the reliability of monitoring data, and help analyze the temporal characteristics of ionospheric disturbances.

[0029] 3. Taking into account the physical characteristics of ionospheric activity and the constraints of Beidou and geostationary orbit satellite data, the fitting accuracy of the ionospheric model can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 The present invention is a schematic flow chart of the steps for implementing the method.

[0032] Figure 2 Schematic diagram of solar radiation flux.

[0033] Figure 3 Schematic diagram of the ionospheric single-layer model and puncture point geometry.

[0034] Figure symbols: 1. SR represents solar radiation, 2. SLM represents a synchronous orbit satellite, 3. Ionosphere represents ionosphere, 4. RX represents a receiver, 5. GND represents ground, 6. P represents a puncture point, and 7. P' represents a sub-satellite point of the puncture point. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Reference Figure 1 As shown, the present invention provides a new ionospheric modeling technology based on the continuity equation and Beidou synchronous orbit satellite constraints, including: Step 1: an ionospheric modeling method based on the continuity equation.

[0037] The continuity equation is an important equation that describes the physical processes of the ionosphere. The physical processes of the ionosphere can be roughly divided into two categories: A causes the generation and disappearance of plasma, and B causes the movement of plasma. These two processes are called photochemical processes and transport processes, respectively. The ionosphere continuity equation derived from this is: ,in It represents the rate of change of electron concentration, where N is the electron concentration, t is the time, q is the electron generation rate, L(N) is the electron loss rate, NV represents the flux of electrons (or ions) generated by the transport process, and V is the net escape velocity. represents the divergence of the NV, that is, the rate of change of electron concentration caused by the transport process.

[0038] It should be noted that the electron generation rate refers to the ion-electron pairs generated per unit time and per unit volume, and the unit is: The main way charged particles are produced is the result of neutral atmosphere absorbing solar ultraviolet radiation (Extreme Ultraviolet, EUV) and X-rays. The electron loss rate represents the number of ion-electron pairs that disappear per unit time and per unit volume. The unit is: The loss rate is a function of the electron concentration N. The main loss processes in the ionosphere are: the recombination of atomic ions and electrons, the recombination of molecular ions and electrons, and the attachment process in the lower ionosphere. The movement of free electrons in the ionosphere includes drift and diffusion. The main driving factors are the electric field, the geomagnetic field, and the neutral atmospheric wind. That is, the driving force of electron movement is mainly the electric field force and the Lorentz force. Therefore, the movement characteristics of electrons in the ionosphere in the earth's magnetic field and electric field satisfy the Maxwell equations theory.

[0039] The present invention utilizes the continuity equation to construct an ionosphere model, taking into account three physical processes of the generation rate, loss rate and transport process of electrons in the ionosphere, and can more accurately describe the activity laws of the ionosphere, thereby improving the accuracy of the ionosphere model.

[0040] Solar far ultraviolet radiation and X-ray radiation act on the neutral atmosphere, ionizing neutral atmospheric particles and generating ion-electron pairs. Assuming X is a molecule or atom of a certain atmospheric component, according to the law of mass action: ,in represents photons, and e represent positively charged ions and electrons respectively, thus producing positive ions and free electrons in the ionosphere, and the above reaction is a reversible process, which is a photochemical process. The process includes two key factors that cause changes in electron concentration: the generation rate and the loss rate.

[0041] It should be noted that radiation intensity and the density of neutral atmospheric components are two basic factors that control the ionization rate. During the sunrise stage, solar radiation gradually increases, the forward reaction rate is greater than the reverse reaction rate, free electrons are generated, and this is manifested as an increase in the electron concentration in the ionosphere. When the solar radiation reaches its peak, the electron content also reaches its peak. During the sunset stage, solar radiation gradually weakens, and the reverse reaction rate is greater than the forward reaction rate, which is manifested as a decrease in the total electron content in the ionosphere, and it tends to a state of equilibrium at night.

[0042] In a specific embodiment, the generation rate is specifically analyzed by: assuming that the generation rate of a single gas is: ,in , , , They represent the generation rate, ionization efficiency, absorption area, and gas density of the i-th gas, respectively. I is the solar radiation flux. Due to the large number of gas types in the ionosphere, it is difficult to accurately measure the generation rate of all gases. In order to simplify the process, the concept of average generation rate is introduced, namely: ,in , , , Denote the average generation rate, average ionization efficiency, average absorption area, and average gas density in the local area of ​​the ionosphere. , then (4) can be simplified to: .

[0043] It should be noted that the Earth's atmosphere is a mixture of various gases. Different gases have different physical properties, which leads to differences in their ability to produce electrons under the action of solar radiation. The ionization efficiency refers to the number of photoelectrons generated after absorbing a photon, and the solar radiation flux refers to the number of photons passing through a unit volume per unit time.

[0044] set up is the zenith angle of solar radiation. Assuming that solar radiation is uniformly irradiated on the single-layer model of the ionosphere, the amount of solar radiation received per unit area of ​​the ionosphere is only related to the incident angle and radiation intensity, such as Figure 2 If the solar radiation flux is , the solar radiation flux I actually received per unit area of ​​the ionosphere can be expressed as , the functional relationship between the average generation rate and the solar radiation intensity can be obtained from equations (5) and (6), as shown in equation (7).

[0045] If the solar radiation flux is approximately a constant, it can be seen that when It is determined that the average electron production rate in the ionosphere is proportional to the cosine value of the solar radiation zenith angle, or, when the solar altitude angle is constant and When it is determined, the average electron production rate in the ionosphere is proportional to the intensity of solar radiation. .

[0046] In a specific embodiment, the loss rate is specifically analyzed as follows: the loss rate L(N) of charged particles in the ionosphere is determined by the type and reaction rate of the photochemical reaction in the ionosphere. For the convenience of explanation, X and Y are used to represent neutral particles, and , Respectively represent positive and negative ions, represents ions in a certain excited state, then there are main ion reactions in the ionosphere as shown in equations (8) to (12): Ion-atom exchange: .....(8) Ion-ion complexation: .....(9) Ion-electron recombination: 1) Decomposition type: .....(10) 2) Radiation type: 3) Tritype: .....(12) Among the types of ion-electron recombination reactions, the radiation type is not easy to satisfy the conservation of energy and momentum at the same time, so the reaction speed is very slow. In the three-body reaction, M is a catalyst, and the concentration of the catalyst affects the reaction speed. In fact, the three-body reaction rate coefficient is proportional to the square of the atmospheric concentration. This type of reaction is only obvious in the D layer of the ionosphere, and the decomposition and recombination to generate two material particles is easy to satisfy the conservation of energy. The reaction speed is 5 orders of magnitude greater than the radiation type. It is the main recombination reaction in the ionosphere. In fact, the loss process of most electrons and ions in the ionosphere goes through two processes: 1) Ion-atom exchange: .....(13) 2) Decomposition and compounding: .....(14) When the main components of charged particles are molecular ions (ionosphere below 200 km), the electron loss is determined by the decomposition and recombination reaction, see formula (14), which satisfies the square law loss formula: .....(15), where is the composite coefficient, is the concentration of molecular or atomic positive ions, and N is the electron concentration. Since the ionosphere is electrically neutral as a whole, we have: .....(16), then equation (15) can be transformed into: .....(17).

[0047] When the charged ions are mainly atomic ions (ionosphere above 200 km), the ion-atom exchange reaction is the main process of electron loss, satisfying the linear loss formula: .....(18), where The adhesion coefficient represents the linear response.

[0048] Since the two loss processes exist simultaneously but their reaction speeds are different at different altitudes, the electron loss of the entire ionosphere is controlled by equations (17) and (18), and the composite coefficient and adhesion coefficient Temperature dependent, assuming square law losses account for % of total losses ( ), then the linear loss accounts for , therefore, the comprehensive ionospheric loss rate can be expressed as: .....(19), among which, Dependent on the height, when the ionosphere single-layer model is determined, the height of the single-layer model is fixed. is a constant, let , , then the functional relationship between the loss rate and the electron concentration can be obtained by simplifying formula (19), as shown in formula .....(20), It can be seen from formula (20) that the electron loss rate in the ionosphere is a quadratic function of the electron concentration.

[0049] In a specific embodiment, the transport process is specifically analyzed as follows: the change in the electron concentration in the ionosphere is not only affected by the photochemical reaction, but also related to the movement of the plasma. The ionosphere can be regarded as a plasma layer, which is affected by gravity, collisions between particles and electromagnetic forces. The transport term in the continuity equation (1) is caused by the movement of charged particles due to various forces, thereby changing the concentration of free electrons. The transport term can be expanded as follows: .....(21), where u, v, and w are the components of the charge velocity V in the x, y, and z directions, respectively. The x-axis is parallel to the geomagnetic meridian and is positive toward the north, the y-axis is parallel to the geomagnetic latitude and is positive toward the east, and the z-axis is vertical and is positive downward. Under assumption 5, ignoring the viscosity of particles, electron-ion collisions, gravity, and the effects of pressure gradient, the motion equation of charged particles in the ionosphere can be simplified as follows: , U is the neutral atmospheric motion speed, V is the net drift speed of charged particles, m is the particle mass, is the collision frequency of charged particles with neutral particles, Charge the particles.

[0050] Assume that the total driving force on the electron is F=( , , ),in, , , are the components of the total driving force in the three coordinate directions respectively. Assume that the magnetic field intensity at any position is B, and its angle with the single-layer model (magnetic inclination) is , then the speed of charged particles in the three coordinate directions is: , where Ω is the magnetic rotation frequency related to the geomagnetic intensity, charge mass, and charge, and its expression is .....(twenty four).

[0051] Under the assumption of a single-layer model, the vertical motion of charged particles can be ignored, and equation (21) can be rewritten as: .....(25), from (25), we can see that the transport term is related to the electron concentration N, the horizontal motion speed u, v. Since the divergence of the electron or ion flux is also a physical characteristic of ionospheric activity, under the condition of assumption 4, the transport term in a short time and small range can be regarded as a constant, set as ,Right now: .....(26).

[0052] Under the condition of assumption 2, the change of electron concentration within a certain period of time is Ignoring the above, after substituting formulas ), (7), (20), and (26) into the ionospheric continuity equation (1), we can obtain: .....(27), Formula (27) can be regarded as a second-order polynomial about the electron concentration N, and the solution of the equation can be expressed as: .....(28).

[0053] Assume that the solar altitude angle is θ, the solar declination is δ, the geographical latitude of the observation location is represented by B, the geographical longitude is L, t is the local time, and λ is the hour angle of the local time. The calculation formula of the solar altitude angle can be expressed as formula (29): .....(29), Substituting formula (29) into formula (28), we can get: .....(30), It should be noted that the solar altitude angle changes with the local time and the solar declination. The hour angle is 0° at 14:00 local time, that is, the sun rises to its highest position of the day at 14:00 local time.

[0054] It should be noted that in practical applications, the radiation flux in formula (31) is can be set as a constant. The solar declination δ is the angle between the Earth's equatorial plane and the line connecting the Sun and the Earth's center, that is, the latitude of the point where the Sun is directly above the Earth. The solar declination moves within the range of +23°26′ and -23°26′ with a year as a period. Since the position of the solar declination at any time during the annual motion is strictly known, δ can be calculated by formula (31) in radians.

[0055] .....(31), where DOY represents the accumulated days per year. Since the solar radiation received by the night hemisphere is very weak, when the solar hour angle λ satisfies (λ<-90°,λ>90°), the solar radiation flux received by the ionosphere can be considered to be zero, that is, , at this time, the first formula of formula (30) will be further simplified to obtain the night model function expression of the model, because , are parameters related to the composite coefficient and the attachment coefficient, respectively. It can be judged that they are non-negative numbers. Since the electron content is also non-negative, after rearranging equation (30), the final function expression of the new ionosphere model can be obtained, as shown in equation (32). (32) Step 2: Use BeiDou synchronous orbit satellite observation data to construct constraints.

[0056] In a specific embodiment, the constraint conditions are constructed by using Beidou synchronous orbit satellite observation data. The specific analysis method is: the ionosphere is assumed to be a spherical shell with a thickness of 0, and all electrons are concentrated on this spherical shell. The schematic diagram is shown in Figure 3 Under this assumption, the vertical total electron content VTEC is obtained using the mapping function, and the calculation formula is: ....(33), where Re is the mean radius of the Earth, Z' is the zenith distance of the puncture point, E is the satellite altitude angle, H is the effective height of the single-layer model, VTEC represents the vertical total electron content, Represent the hardware delay of the satellite and receiver respectively.

[0057] It should be noted that the use of smoothed pseudorange observations can obtain a more reliable path total electron content. The English name of the vertical total electron content is Vertical Total Electron Content, abbreviated as VTEC.

[0058] Since the BeiDou synchronous orbit satellite GEO can continuously monitor the total electron content TEC at a fixed position in the ionosphere, the monitoring data quality of the GEO satellite IPP is better than that of general medium-orbit satellites. Therefore, assuming that the VTEC penetrated by the GEO satellite is the accurate value of the zenith total electron content, formula (33) can be rewritten as: .....(32), among which, is the total electron content at the zenith at the GEO satellite penetration point, is the phase-smoothed pseudorange observation value of the GEO satellite, is the hardware delay of the GEO satellite.

[0059] The electron content at the GEO satellite IPP is used to establish constraints: = .....(33), among which, Represents the ionosphere at a certain epoch The zenithal total electron content at position, is the latitude of a GEO satellite puncture point, is the longitude of a GEO satellite puncture point.

[0060] The present invention utilizes Beidou synchronous orbit satellites to monitor ionospheric disturbances, can realize continuous monitoring of electron concentrations at some IPP positions, improves the reliability of monitoring data, and is helpful for analyzing the time characteristics of ionospheric disturbances.

[0061] Step 3: Establish a high-precision ionospheric TEC model based on constraints.

[0062] In a specific embodiment, the step 4: establishing a high-precision ionospheric TEC model based on constraint conditions, the specific analysis method is: From formula (32), it can be seen that the electron concentration can be expressed as a function of the geographical location and the solar hour angle, that is: .....(34), where B is the latitude of the puncture point, is the solar hour angle. Combining the constraint condition (33) and the least squares method, the functional expression of the ionospheric modeling algorithm integrating the Beidou synchronous orbit satellite data constraints can be obtained as follows: .....(35), where V represents the residual value, P is the unit weight matrix, The specific expression of is shown in formula (32).

[0063] It should be noted that in the actual modeling process, the least squares method is generally used to estimate the ionospheric model coefficients. However, when using the least squares method to estimate the model coefficients, only the size of the comprehensive error is taken into account, and the fitting accuracy at a single IPP is not considered, which may lead to large local fitting deviations of the model.

[0064] The present invention takes into account the constraints of Beidou and synchronous orbit satellite data on the physical characteristics of ionospheric activity, and can effectively improve the fitting accuracy of the ionospheric model.

[0065] The electron concentration data at the IPP is calculated by using BeiDou observation data. Then, combined with the constraints of the second and third equations in equation (35), the value in equation (32) is obtained. , , , , The five model coefficients realize the construction of the ionospheric model based on the continuity equation and Beidou synchronous orbit satellite constraints.

[0066] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they should all fall within the protection scope of the present invention.

Claims

1. New ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints, involving the field of ionospheric monitoring technology, including: Step 1: Ionosphere modeling method based on continuity equation; Step 2: Use BeiDou synchronous orbit satellite observation data to construct constraint conditions; Step 3: Establish a high-precision ionospheric TEC model based on constraints.

2. The new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints according to claim 1 is characterized in that: The step 1: ionosphere modeling method based on the continuity equation, the specific analysis method is: The physical processes of the ionosphere can be roughly divided into two types: photochemical processes and transport processes. The ionosphere continuity equation derived from these processes is: ,in represents the rate of change of electron concentration, where N is the electron concentration, t is time, q is the electron generation rate, L(N) is the electron loss rate, NV represents the flux of charged particles generated by the transport process, and V is the net drift velocity. represents the divergence of NV; Solar far ultraviolet radiation and X-ray radiation act on the neutral atmosphere, ionizing neutral atmospheric particles and generating ion-electron pairs. Assuming X is a microscopic particle of a certain atmospheric component, according to the law of mass action: ,in represents photons, and e represent positively charged ions and electrons respectively, thus producing positive ions and free electrons in the ionosphere, and the above reaction is a reversible process, which is a photochemical process. The process includes two key factors that cause changes in electron concentration: the generation rate and the loss rate.

3. The new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints according to claim 2 is characterized in that: The specific analysis method of the generation rate is as follows: Assume that the production rate of a single gas is: ,in , , , They represent the generation rate, ionization efficiency, absorption area, and gas density of the i-th gas, respectively. I is the solar radiation flux, and the average value is processed, that is: ,in , , , represents the average generation rate, average ionization efficiency, average absorption area, and average gas density in the local area of ​​the ionosphere. , then (4) can be simplified to: ; set up is the zenith angle of solar radiation. Assuming that solar radiation is uniformly irradiated on the single-layer model of the ionosphere, the amount of solar radiation received per unit area of ​​the ionosphere is only related to the incident angle and radiation intensity. If the solar radiation flux is , the solar radiation flux I actually received per unit area of ​​the ionosphere can be expressed as , the functional relationship between the average generation rate and the solar radiation intensity can be obtained from equations (5) and (6), as shown in equation (7): .

4. The new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints according to claim 2 is characterized in that: The specific analysis method of the loss rate is as follows: The loss rate of charged particles in the ionosphere, L(N), is determined by the type and reaction rate of the photochemical reaction in the ionosphere. For the convenience of explanation, X and Y are used to represent neutral particles, and , Respectively represent positive and negative ions, and use represents ions in a certain excited state, then there are main ion reactions in the ionosphere as shown in equations (8) to (12): Ion-atom exchange: .....(8) Ion-ion complexation: .....(9) Ion-electron recombination: 1) Decomposition type: .....(10) 2) Radiation type: 3) Three body types: .....(12) Among the types of ion-electron recombination reactions, the radiation type is not easy to satisfy the conservation of energy and momentum at the same time, so the reaction speed is very slow. In the three-body reaction, M is a catalyst, and the concentration of the catalyst affects the reaction speed. In fact, the three-body reaction rate coefficient is proportional to the square of the atmospheric concentration. This type of reaction is only obvious in the D layer of the ionosphere, and the decomposition and recombination to generate two material particles is easy to satisfy the conservation of energy. The reaction speed is 5 orders of magnitude greater than that of the radiation type. It is the main recombination reaction in the ionosphere. In fact, the loss process of most electrons and ions in the ionosphere goes through two processes: 1) Ion-atom exchange: .....(13) 2) Decomposition and compounding: .....(14) When the main component of the charged particles is molecular ions, the electron loss is determined by the decomposition and recombination reaction, see formula (14), which satisfies the square law loss formula: .....(15), where is the composite coefficient, is the concentration of molecular or atomic positive ions, and N is the electron concentration. Since the ionosphere is electrically neutral as a whole, we have: .....(16), then equation (15) can be transformed into: .....(17); When the charged ions are mainly atomic ions, the ion-atom exchange reaction is the main process of electron loss, satisfying the linear loss formula: .....(18) in, The adhesion coefficient represents the linear response; Since the two loss processes exist simultaneously but their reaction speeds are different at different altitudes, the electron loss of the entire ionosphere is controlled by equations (17) and (18), and the composite coefficient and adhesion coefficient Temperature dependent, assuming square law losses account for % of total losses , then the linear loss accounts for , therefore, the comprehensive ionospheric loss rate can be expressed as: .....(19), among which, Dependent on the height, when the ionosphere single-layer model is determined, the height of the single-layer model is fixed. is a constant, let , , then the functional relationship between the loss rate and the electron concentration can be obtained by simplifying formula (19), as shown in formula .....(20) It can be seen from formula (20) that the electron loss rate in the ionosphere is a quadratic function of the electron concentration.

5. The new ionospheric modeling technology based on continuity equation and Beidou synchronous orbit satellite constraints according to claim 2 is characterized in that: The specific analysis method for the transportation process is as follows: The transport term in the continuity equation (1) is caused by various forces that cause the movement of charged particles, thereby changing the concentration of free electrons. The transport term can be expanded as: .....(21), where u, v, and w are the components of the charge velocity V in the x, y, and z directions, respectively. The x-axis is parallel to the geomagnetic meridian and is positive toward the north, the y-axis is parallel to the geomagnetic latitude and is positive toward the east, and the z-axis is vertical and is positive downward. Under assumption 5, ignoring the viscosity of particles, electron-ion collisions, gravity, and the effects of pressure gradient, the motion equation of charged particles in the ionosphere can be simplified as follows: , U is the neutral atmospheric motion speed, V is the net drift speed of charged particles, m is the particle mass, is the collision frequency of charged particles with neutral particles, Charge the particles; Assume that the total driving force on the electron is F=( , , ),in, , , are the components of the total driving force in the three coordinate directions respectively. Assume that the magnetic field intensity at any position is B, and its angle with the single-layer model (magnetic inclination) is , then the speed of charged particles in the three coordinate directions is: , where Ω is the magnetic rotation frequency related to the geomagnetic intensity, charge mass, and charge, and its expression is .....(twenty four); Under the assumption of a single-layer model, the vertical motion of charged particles can be ignored, and equation (21) can be rewritten as: .....(25), from (25), we can see that the transport term is related to the electron concentration N, the horizontal motion speed u, v. Since the divergence of the electron or ion flux is also a physical characteristic of ionospheric activity, under the condition of assumption 4, the transport term in a short time and small range can be regarded as a constant, set as ,Right now: .....(26); Under the condition of assumption 2, the change of electron concentration within a certain period of time is Ignoring the above, after substituting formulas (7), (20), and (26) into the ionospheric continuity equation (1), we can obtain: .....(27), Formula (27) can be regarded as a second-order polynomial about the electron concentration N, and the solution of the equation can be expressed as: .....(28); Assume that the solar altitude angle is θ, the solar declination is δ, the geographical latitude of the observation location is represented by B, the geographical longitude is L, t is the local time, and λ is the hour angle of the local time. The calculation formula of the solar altitude angle can be expressed as formula (29): .....(29), Substituting formula (29) into formula (28), we can get: .....(30), .....(31), where DOY represents the accumulated days per year. Since the solar radiation received by the night hemisphere is very weak, when the solar hour angle λ satisfies (λ<-90°,λ>90°), the solar radiation flux received by the ionosphere can be considered to be zero, that is, , at this time, the first formula of formula (30) will be further simplified to obtain the night model function expression of the model, because , are parameters related to the composite coefficient and the attachment coefficient, respectively. It can be judged that they are non-negative numbers. Since the electron content is also non-negative, after rearranging equation (30), the final function expression of the new ionosphere model can be obtained, as shown in equation (32). (32).

6. The new ionospheric modeling technology based on continuity equation and BeiDou synchronous orbit satellite constraints according to claim 1 is characterized in that: The second step is to use Beidou synchronous orbit satellite observation data to construct constraint conditions. The specific analysis method is as follows: The ionosphere is assumed to be a spherical shell with a thickness of 0. All electrons are concentrated on this spherical shell. Under this assumption, the vertical total electron content VTEC is obtained using the mapping function. The calculation formula is: ....(33), where Re is the mean radius of the Earth, Z' is the zenith distance of the puncture point, E is the satellite altitude angle, H is the effective height of the single-layer model, VTEC represents the vertical total electron content, represent the hardware delays of the satellite and receiver respectively; Since the BeiDou synchronous orbit satellite GEO can continuously monitor the total electron content TEC at a fixed position in the ionosphere, the monitoring data quality of the GEO satellite IPP is better than that of general medium-orbit satellites. Therefore, assuming that the VTEC penetrated by the GEO satellite is the accurate value of the zenith total electron content, formula (33) can be rewritten as: .....(32), among which, is the total electron content at the zenith at the GEO satellite penetration point, is the phase-smoothed pseudorange observation value of the GEO satellite, The hardware delay of GEO satellite; The electron content at the GEO satellite IPP is used to establish constraints: = .....(33), among which, Represents the ionosphere at a certain epoch The zenithal total electron content at position, is the latitude of a GEO satellite puncture point, is the longitude of a GEO satellite puncture point.

7. The new ionospheric modeling technology based on continuity equation and BeiDou synchronous orbit satellite constraints according to claim 6 is characterized in that: The step three: establishing a high-precision ionospheric TEC model based on constraint conditions, the specific analysis method is as follows: It can be seen from formula (32) that the electron concentration can be expressed as a function of the geographical location and the solar hour angle, that is: .....(34), where B is the latitude of the puncture point, is the solar hour angle. Combining the constraint condition (33) and the least squares method, the functional expression of the ionospheric modeling algorithm integrating the Beidou synchronous orbit satellite data constraints can be obtained as follows: .....(35), where V represents the residual value, P is the unit weight matrix, The specific expression of is shown in formula (32); The electron concentration data at the IPP is calculated by using BeiDou observation data. Then, combined with the constraints of the second and third equations in equation (35), the value in equation (32) is obtained. , , , , The five model coefficients realize the construction of the ionospheric model based on the continuity equation and Beidou synchronous orbit satellite constraints.

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