Relaxation time evaluation method and system applied to radiation band modeling process

Abstract

The invention discloses a relaxation time evaluation method and system applied to a radiation band modeling process, and solves the technical problem that the distribution and relaxation time of high-energy particles in a radiation band cannot be accurately reflected in the prior art. Comprising the following steps: firstly, dividing a space into three-dimensional grids; secondly, establishing a local coordinate system; then, high-energy particles with different angles and different energies are put into the grid points, and the motion state of the high-energy particles is tracked; then, counting particle distribution states at different time intervals, and generating a particle distribution image; establishing a function of relaxation time of the high-energy particles by comparing particle images at different times; and finally, calculating relaxation time under different space weather conditions, and establishing a database containing the function relationship between the input parameters and the relaxation time. The spatial range of the method can obviously cross a radiation band and a near-earth space, and the calculated relaxation time can provide necessary technical support for communication, navigation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation belt modeling, and in particular to a relaxation time evaluation method and system used in the radiation belt modeling process. Background Art

[0002] High-energy particles pose a huge potential threat to satellites in orbit, causing single particle flips and other events, resulting in satellite loss of control. At the same time, high-energy particles settling into the near-Earth space atmosphere will cause changes in the ionization rate of the ionosphere and upper atmosphere, affecting communications. This shows that high-energy particles in near-Earth space are of great significance in basic space research and practical applications.

[0003] High-energy particles are mainly concentrated in the Earth's radiation belt, which refers to the gathering area of ​​a large number of high-energy charged particles in the space around the Earth, also known as the Van Allen radiation belt. It is divided into two belts, the inner and outer belts, one on the sun-facing side and one on the dark side. The inner radiation belt is closer to the ground, while the outer radiation belt is farther from the ground. It is a specific area formed by the geomagnetic field that constrains high-energy particles.

[0004] The distance from the center of the inner radiation belt to the center of the earth is about 1.5 earth radii (Re), and the distance from the center of the outer radiation belt to the center of the earth is about 3 to 4 earth radii. The particle environment of the inner and outer radiation belts on the sunlit side and the dark side is not completely symmetrical in space.

[0005] The inner radiation belt is referred to as the inner belt. The inner belt contains a large number of high-energy protons and electrons. In the absence of solar proton events and when the geomagnetic disturbance is not large, the spatial distribution and intensity of high-energy protons and electrons in the inner radiation belt are quite stable, and it is called the stable inner radiation belt.

[0006] Since the discovery of space radiation belts, people have launched countless probes to detect radiation belts and established radiation belt models based on the detection data.

[0007] Due to the special structure and function of the Earth's magnetic field, the distribution of high-energy particles in the radiation belt and near-Earth space is energy- and direction-dependent. The most widely used AE8 / AP8 model currently established was developed by the United States in the 1960s. It is well known that the flux of high-energy particles in near-Earth space has an important relationship with the structure of the Earth's magnetic field. Since the Earth's magnetic field has long-period variation characteristics, especially the obvious acceleration of geomagnetic changes in recent years (IGRF13 model was released in advance), the shielding effect of the Earth's magnetic field on high-energy particles will change significantly, resulting in changes in the background high-energy particle environment caused by the entry of solar / galactic cosmic rays into the magnetosphere. Therefore, it is necessary to re-measure the cutoff stiffness of high-energy particles caused by magnetic field changes, and make certain corrections to the AE8 / AP8 model.

[0008] Due to the shortcomings and disadvantages of existing methods and the urgent need for practical applications, the present invention provides a method for relaxation time applied in the radiation belt modeling process to achieve optimized high-energy particle radiation belt modeling. Summary of the invention

[0009] The purpose of the present invention is to provide a relaxation time evaluation method and system for use in the radiation belt modeling process, so as to solve the technical problem that the prior art cannot accurately reflect the distribution and relaxation time of high-energy particles in the radiation belt.

[0010] To achieve the above object, the present invention provides the following technical solutions: In a first aspect, the present invention provides a method for evaluating relaxation time in a radiation belt modeling process, comprising the following steps: Step 1: Space grid point division: Set the calculation range of the three-dimensional space according to actual needs, and divide the space into three-dimensional grids according to accuracy requirements; Step 2, establish a local coordinate system, including a FAC coordinate system and a NEC / ENU coordinate system; the FAC coordinate system is a field coordinate system, used to establish the dependency of the pitch angle, and the NEC / ENU coordinate system is a northeast and northeast upper coordinate system, used to establish the dependency of the azimuth angle; Step 3: Place high-energy particles of different angles and energies at grid points as required; Step 4: Track the motion state of high-energy particles. The time interval of particle motion is set to 5 minutes. The motion direction of particles: the pitch angle interval is 20°, and the azimuth angle interval is set to 20°. The exit condition of particles is set as follows: the outer boundary is the direction of the top of the magnetosphere, and the inner boundary is 1Re. Step 5, counting the motion states of particles at different time intervals, and generating a particle distribution state image of the entire calculation area; Step 6: Compare the particle images at different times and establish the function of the relaxation time of high-energy particles at different energies and angles; Step 7, calculating the relaxation time function for different space weather conditions; Step 8, establishing a database including the functional relationship between input parameters and relaxation time; Step 9: Apply the calculation of relaxation time in the actual radiation belt to evaluate the time it takes for high-energy particles to reach a steady-state distribution under different space weather conditions.

[0011] Furthermore, in step 3, the number of particles released is determined by the integral formula: ; Among them, x, y, and z represent the three-dimensional coordinate positions of the particles, is the high energy particle throwing angle, is the particle energy, is the particle azimuth.

[0012] Furthermore, in step 4, the step of using the Newton-Lorentz equation to track the motion state of high-energy particles includes: Under the influence of the background magnetic field, the movement of high-energy particles in the magnetosphere is described by the Lorentz equation: ; in, is the particle momentum, is the particle speed, is the particle charge, is the background magnetic field, is the electric field, The motion state of high-energy particles is expressed as: ; in, =The speed of light, ignoring the influence of background electric field, and then trace the motion state of high-energy particles backwards.

[0013] Furthermore, in step 4, the step of using the stochastic partial differential equation method to track the motion state of high-energy particles includes: In the presence of diffusion effect, the Fokker Planck equations are converted into a set of six-dimensional stochastic partial differential equations using the stochastic partial differential equation method to backward trace the particle motion state.

[0014] Furthermore, the step 6 specifically includes: The high energy particle relaxation time function is expressed as , which is a function of coordinate position, energy, pitch angle, and azimuth; The particle distribution state function is expressed as , which is also a function of coordinate position, energy, pitch angle, and azimuth; According to the principle of the movement zone and forbidden zone of charged high-energy particles in the Earth's magnetosphere, there will always be a time node in the movement of high-energy particles in the Earth's magnetosphere space, when the particles in the space reach a certain equilibrium state; Mark different times t i , i=1,2,3..., the corresponding high-energy particle distribution state function is , the corresponding distribution function is obtained by tracking the motion state of high-energy particles at each grid point; At any time , the particle distribution function satisfies: and ; Where N is the number of particles released, To preset the accuracy threshold, adjust it according to the required accuracy, define the above state to reach convergence, the time when the particle distribution state function reaches convergence corresponds to the relaxation time of high-energy particles, that is: .

[0015] Furthermore, step 7 specifically includes: by adjusting different parameters of space weather, including solar wind dynamic pressure, solar wind speed, interplanetary magnetic field strength, magnetic inclination, and Dst index, repeating steps 1 to 6, and calculating the relationship between relaxation time and various parameters.

[0016] In a second aspect, the present invention provides a relaxation time evaluation system for use in a radiation belt modeling process, comprising: Space grid and coordinate system configuration unit: used to divide the three-dimensional space grid and establish the local coordinate system; Particle management and tracking unit: used to determine the number of particles passing through and track the motion state of high-energy particles; Data statistics and distribution analysis unit: Count the particle distribution states at different time points, and compare the distribution differences at adjacent moments to determine whether the convergence threshold has been reached; Relaxation time calculation unit: used to calculate the relaxation time under different space weather conditions; Multi-parameter simulation and database unit: used to adjust space weather parameters, repeat simulations to obtain relaxation times under different conditions, and build a database to store the mapping relationship between input parameters and relaxation times, supporting fast retrieval and comparative analysis.

[0017] In a third aspect, the present invention provides an electronic device comprising a processor and a memory, wherein the memory stores computer instructions, and the processor is used to execute the computer instructions stored in the memory to implement the steps of a relaxation time evaluation method applied in the radiation belt modeling process.

[0018] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute steps of a relaxation time estimation method applied in a radiation belt modeling process.

[0019] Based on the above technical solution, the embodiments of the present invention can at least produce the following technical effects: The relaxation time evaluation method proposed in the present invention can obviously cover the radiation belt and near-Earth space, and the calculated relaxation time can provide necessary technical support for communication, navigation, etc. At the same time, it is urgent in view of its potential role in space security. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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 the structures shown in these drawings without paying creative work.

[0021] Figure 1 is a technical flow chart of an embodiment of the present invention; Figure 2 Graph 1 is a proton distribution image of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in 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. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] Referring to body 1, a relaxation time estimation method applied in radiation belt modeling process comprises the following steps: Step 1: Space grid point division: Set the calculation range of the three-dimensional space according to actual needs, and divide the space into three-dimensional grids according to accuracy requirements.

[0024] Step 2: Establish a local coordinate system, including the FAC coordinate system and the NEC / ENU coordinate system. The FAC coordinate system is a field coordinate system used to establish the dependency of the pitch angle, and the NEC / ENU coordinate system is a northeast and northeast coordinate system used to establish the dependency of the azimuth angle.

[0025] Step 3: High-energy particles of different angles (including azimuth, throwing angle, etc.) and different energies are placed at the grid points as required; the number of particles placed is determined by the integral formula: ; Among them, x, y, and z represent the three-dimensional coordinate positions of the particles, is the high energy particle throwing angle, is the particle energy, is the particle azimuth.

[0026] Step 4: Track the motion state of high-energy particles. The particle motion time interval is set to 5 minutes. The particle motion direction: the pitch angle interval is 20°, and the azimuth angle interval is set to 20° (the angle interval can be continuously adjusted according to actual needs). The particle exit condition is set as follows: the outer boundary is the direction of the magnetosphere top, and the inner boundary is 1Re. Using the equations of motion for high energy particles (there are two ways to do this, the first using the simple Newton-Lorentz equations and the second using a complex set of stochastic partial differential equations).

[0027] First, the Newton-Lorentz equations (under the influence of the background magnetic field) The motion of high-energy particles in the magnetosphere is described by the Lorentz equations ,in is the particle momentum, is the particle speed, is the particle charge, is the background magnetic field, is the electric field, , is the speed of light. Usually the influence of the background electric field can be ignored. Then the particle motion state is tracked backwards.

[0028] Second, the stochastic partial differential equation method (under the condition of diffusion effect) is used to transform the Fokker Planck equation into a six-dimensional stochastic partial differential equation group to backward track the particle motion state.

[0029] Step 5, counting the motion states of particles at different time intervals, and generating a particle distribution state image of the entire calculation area; Step 6: Compare the particle images at different times and establish the function of the relaxation time of high-energy particles with different energies and different angles (throw angle, azimuth angle); The high energy particle relaxation time function is expressed as , which is a function of coordinate position, energy, pitch angle, and azimuth; The particle distribution state function is expressed as , which is also a function of coordinate position, energy, pitch angle, and azimuth; According to the principle of the movement zone and forbidden zone of charged high-energy particles in the Earth's magnetosphere, it can be inferred that there will always be a time node in the movement of high-energy particles in the Earth's magnetosphere space, when the particles in the space reach a certain equilibrium state; Mark different times t i , i=1,2,3..., the corresponding high-energy particle distribution state function is , the corresponding distribution function is obtained by tracking the motion state of high-energy particles at each grid point; At any time , the particle distribution function satisfies: and ; Where N is the number of particles released, is the preset accuracy threshold, which can be adjusted according to the required accuracy. At this time, the above state is defined to reach convergence, and the particle distribution state function The time to convergence is t i The corresponding relaxation time is the relaxation time of high-energy particles, namely: .

[0030] Step 7, calculating the relaxation time function for different space weather conditions; By adjusting different parameters of space weather, including solar wind dynamic pressure, solar wind speed, interplanetary magnetic field strength, magnetic inclination, Dst index and other related parameters, the above steps 1-6 are repeated to calculate the relationship between relaxation time and various parameters.

[0031] Step 8: Establish a database, establish data volume for the various calculation input parameters and output parameters, and analyze the dependence of relaxation time on each input parameter; Specifically, the database contains the quantitative relationship between relaxation time and solar wind dynamic pressure, solar wind speed, interplanetary magnetic field strength, magnetic inclination and Dst index.

[0032] Step 9: Apply the calculation of relaxation time in the actual radiation belt to evaluate the time it takes for high-energy particles to reach a steady-state distribution under different space weather conditions.

[0033] Using the above method, the distribution image of high-energy protons in the range of [0,8] in the X-axis direction and [0,8] in the Z-axis direction during the period of geomagnetic calm under the dipole field background is calculated, corresponding to a proton with a stiffness of 200MV for one hour, as shown in Figure 2 As shown (due to the involvement of a large number of single-particle motion calculation processes, only the results up to the 5th step are shown here, not the final relaxation time results).

[0034] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A relaxation time evaluation method for radiation belt modeling, characterized in that: The following steps are involved: Step 1: Space grid point division: Set the calculation range of the three-dimensional space according to actual needs, and divide the space into three-dimensional grids according to accuracy requirements; Step 2: Establish the local coordinate system, including the FAC coordinate system and the NEC / ENU coordinate system; Step 3: Place high-energy particles of different angles and energies at grid points as required; Step 4: Track the motion state of high-energy particles. The time interval of particle motion is set to 5 minutes. The motion direction of particles: the pitch angle interval is 20°, and the azimuth angle interval is set to 20°. The exit condition of particles is set as follows: the outer boundary is the direction of the top of the magnetosphere, and the inner boundary is 1Re. Step 5, counting the motion states of particles at different time intervals, and generating a particle distribution state image of the entire calculation area; Step 6: Compare the particle images at different times and establish the function of the relaxation time of high-energy particles at different energies and angles; Step 7, calculating the relaxation time function for different space weather conditions; Step 8, establishing a database including the functional relationship between input parameters and relaxation time; Step 9: Apply the calculation of relaxation time in the actual radiation belt to evaluate the time it takes for high-energy particles to reach a steady-state distribution under different space weather conditions.

2. The method for evaluating relaxation time in the radiation belt modeling process according to claim 1, characterized in that: In step 3, the number of particles released is determined by the integral formula: ； Among them, x, y, and z represent the three-dimensional coordinate positions of the particles, is the high energy particle throwing angle, is the particle energy, is the particle azimuth.

3. The method for evaluating relaxation time in the radiation belt modeling process according to claim 1, characterized in that: In step 4, the step of using the Newton-Lorentz equation to track the motion state of high-energy particles includes: Under the influence of the background magnetic field, the movement of high-energy particles in the magnetosphere is described by the Lorentz equation: ； in, is the particle momentum, is the particle speed, is the particle charge, is the background magnetic field, is the electric field, The motion state of high-energy particles is expressed as: ； in, =The speed of light, ignoring the influence of background electric field, and then trace the motion state of high-energy particles backwards.

4. The method for evaluating relaxation time in the radiation belt modeling process according to claim 1, characterized in that: In step 4, the step of using the stochastic partial differential equation method to track the motion state of high-energy particles includes: In the presence of diffusion effect, the Fokker Planck equations are converted into a set of six-dimensional stochastic partial differential equations using the stochastic partial differential equation method to backward trace the particle motion state.

5. The method for evaluating relaxation time in the radiation belt modeling process according to claim 1, characterized in that: The step 6 specifically includes: The high energy particle relaxation time function is expressed as , which is a function of coordinate position, energy, pitch angle, and azimuth; The particle distribution state function is expressed as , which is also a function of coordinate position, energy, pitch angle, and azimuth; According to the principle of the movement zone and forbidden zone of charged high-energy particles in the Earth's magnetosphere, there will always be a time node in the movement of high-energy particles in the Earth's magnetosphere space, when the particles in the space reach a certain equilibrium state; Mark different times t i , i=1,2,3..., the corresponding high-energy particle distribution state function is , the corresponding distribution function is obtained by tracking the motion state of high-energy particles at each grid point; At any time , the particle distribution function satisfies: and ; Where N is the number of particles released, To preset the accuracy threshold, adjust it according to the required accuracy, define the above state to reach convergence, the time when the particle distribution state function reaches convergence corresponds to the relaxation time of high-energy particles, that is: 。 6. The method for evaluating relaxation time in the radiation belt modeling process according to claim 1, characterized in that: The step 7 specifically includes: adjusting different parameters of space weather, including solar wind dynamic pressure, solar wind speed, interplanetary magnetic field strength, magnetic inclination, and Dst index, repeating steps 1 to 6, and calculating the relationship between relaxation time and various parameters.

7. A relaxation time evaluation system for use in radiation belt modeling, characterized in that: A relaxation time evaluation method for a radiation belt modeling process according to any one of claims 1 to 6 is implemented, comprising: Space grid and coordinate system configuration unit: used to divide the three-dimensional space grid and establish the local coordinate system; Particle management and tracking unit: used to determine the number of particles passing through and track the motion state of high-energy particles; Data statistics and distribution analysis unit: Count the particle distribution states at different time points, and compare the distribution differences at adjacent moments to determine whether the convergence threshold has been reached; Relaxation time calculation unit: used to calculate the relaxation time under different space weather conditions; Multi-parameter simulation and database unit: used to adjust space weather parameters, repeat simulations to obtain relaxation times under different conditions, and build a database to store the mapping relationship between input parameters and relaxation times, supporting fast retrieval and comparative analysis.

8. An electronic device comprising a processor and a memory, characterized in that: The memory stores computer instructions, and the processor is used to execute the computer instructions stored in the memory to implement the steps of a relaxation time evaluation method applied to the radiation belt modeling process as described in any one of claims 1-6.

9. A computer-readable storage medium storing computer instructions, characterized in that: The computer instructions are used to make a computer execute the steps of a method for estimating relaxation time in a radiation belt modeling process as claimed in any one of claims 1 to 6.

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