An evaluation method and system for relaxation time in the process of radiation belt modeling

Abstract

The present invention discloses a method and system for evaluating relaxation time in the process of radiation belt modeling, which solves the technical problem that the prior art cannot accurately reflect the distribution and relaxation time of high-energy particles in the radiation belt. The method includes the following steps: First, divide the space into three-dimensional grids; second, establish a local coordinate system; then, release high-energy particles with different angles and energies at the grid points and track their motion states; next, count the particle distribution states at different time intervals to generate particle distribution images; establish a function of the relaxation time of high-energy particles by comparing the particle images at different times; finally, calculate the relaxation time under different space weather conditions and establish a database containing the functional relationship between input parameters and the relaxation time function. The spatial range targeted by the present invention can significantly span the radiation belt and near-Earth space, and the calculated relaxation time can provide necessary technical support for communications, navigation, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation belt modeling, and particularly to an evaluation method and system for relaxation time in the process of radiation belt modeling. Background Technique

[0002] High-energy particles pose a great potential threat to on-orbit satellites, which will cause single-event upsets and the like, resulting in satellite out-of-control. At the same time, when high-energy particles precipitate into the near-earth space atmosphere, it will cause changes in the ionization rate of the ionosphere and the upper atmosphere, affecting communication. Thus, it can be seen that near-earth space high-energy particles are of great significance in space basic research and practical applications.

[0003] High-energy particles are mainly concentrated in the Earth's radiation belt. The Earth's radiation belt refers to the aggregation 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 an inner belt and an outer belt, and each has a region on the sun-facing side and the anti-sun-facing side. The inner radiation belt is closer to the ground, while the outer radiation belt is farther from the ground. It is a specific region formed by the geomagnetic field restricting high-energy particles.

[0004] The distance from the center position of the inner radiation belt to the center of the Earth is about 1.5 Earth radii (Re), and the center of the outer radiation belt is about 3 - 4 Earth radii away from the center of the Earth. The particle environments of the inner and outer radiation belts on the sun-facing side and the anti-sun-facing side are not completely symmetric in space.

[0005] The inner radiation belt is simply called the inner belt. The inner belt contains a large number of high-energy protons and electrons. In the case of no solar proton event and little geomagnetic disturbance, the spatial distribution and intensity of high-energy protons and electrons in the inner radiation belt are quite stable, which is called the stable inner radiation belt.

[0006] Since the discovery of the space radiation belt, countless detectors have been launched for radiation belt detection, and radiation belt models have been established based on the detection data.

[0007] Due to the special structure and action of the Earth's magnetic field, the distribution of high-energy particles in the radiation belt and near-earth space has energy and direction dependence. The currently most widely used AE8 / AP8 model was developed by the United States in the 1960s. As is well known, the high-energy particle flux in near-earth space has an important relationship with the Earth's magnetic field structure. Due to the long-period variation characteristics of the geomagnetic field, especially the obvious acceleration of geomagnetic changes in recent years (the early release of the IGRF13 model), 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 high-energy particle cutoff rigidity caused by magnetic field changes and make certain corrections to the AE8 / AP8 model.

[0008] Due to the deficiencies and drawbacks of existing methods and the urgent needs of practical applications, the present invention provides a method for relaxation time in the process of radiation belt modeling, so as to optimize the modeling of high-energy particle radiation belts. Summary of the Invention

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

[0010] To achieve the above purpose, the present invention provides the following technical solutions:

[0011] In the first aspect, the present invention provides an evaluation method for relaxation time in the process of radiation belt modeling, including the following steps:

[0012] Step 1, Spatial 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 the accuracy requirements;

[0013] Step 2, Establish local coordinate systems, including the FAC coordinate system and the NEC / ENU coordinate system; the FAC coordinate system is a field-aligned coordinate system for establishing the dependence of the pitch angle, and the NEC / ENU coordinate system is the north-east-earth and north-east-up coordinate system for establishing the dependence of the azimuth angle;

[0014] Step 3, Place high-energy particles with different angles and different energies at the grid points according to requirements;

[0015] Step 4, Track the motion state of high-energy particles, and set the motion time interval of the particles to 5 minutes; the motion direction of the particles: the pitch angle interval is 20°, and the azimuth angle interval is set to 20°; the exit condition of the particles is set as: the outer boundary is the direction of the magnetopause, and the inner boundary is 1 Re;

[0016] Step 5, Statistically analyze the motion states of high particles at different time intervals, and generate a particle distribution state image of the entire calculation area;

[0017] Step 6, Compare the particle images at different times, and establish functions of relaxation time for high-energy particles with different energies and different angles;

[0018] Step 7, Calculate the relaxation time function under different space weather conditions;

[0019] Step 8, Establish a database containing the relationship between input parameters and relaxation time functions;

[0020] Step 9, Apply it to the calculation of the actual radiation belt relaxation time, and evaluate the time for high-energy particles to reach a steady-state distribution under different space weather conditions.

[0021] Further, in step 3, the number of particles injected is determined by the integral formula:

[0022] ;

[0023] where x, y, and z respectively represent the three-dimensional coordinate positions of the particles, is the high-energy particle injection angle, is the particle energy, is the particle azimuth angle.

[0024] Further, in step 4, the steps of using the Newton-Lorentz equation to track the motion state of high-energy particles include:

[0025] Under the action of the background magnetic field, the motion of high-energy particles in the magnetosphere is described using the Lorentz equation:

[0026] ;

[0027] where, is the particle momentum, is the particle motion velocity, is the particle charge, is the background magnetic field, is the electric field,

[0028] The motion state of high-energy particles is expressed as:

[0029] ;

[0030] where, is the speed of light, ignoring the influence of the background electric field, and then backward tracking the motion state of high-energy particles.

[0031] Further, in step 4, the steps of using the stochastic partial differential equation method to track the motion state of high-energy particles include:

[0032] Under the condition of the existence of diffusion effects, the Fokker-Planck equation is converted into a six-dimensional stochastic partial differential equation system using the stochastic partial differential equation method, and the particle motion state is backward tracked.

[0033] Further, step 6 specifically includes:

[0034] Denote the high-energy particle relaxation time function as , which is a function of the coordinate position, energy, injection angle, and azimuth angle;

[0035] Express the particle distribution state function as , which is also a function of the coordinate position, energy, injection angle, and azimuth angle;

[0036] According to the principle of the motion area and motion forbidden area of charged high-energy particles in the Earth's magnetosphere, there will always be a time node in the motion of high-energy particles in the Earth's magnetosphere space. At this time, the particles in the space range reach a certain equilibrium state;

[0037] Mark different times t i , i = 1, 2, 3..., and the corresponding distribution state function of high-energy particles is , and the corresponding distribution function is obtained by tracking the motion state of high-energy particles at each grid point;

[0038] At any time , the particle distribution function satisfies:

[0039] And ;

[0040] Among them, N is the number of particles put in, is the preset precision threshold, which is adjusted according to the required precision. Defining that the above state reaches convergence, the time corresponding to the convergence of the particle distribution state function is the relaxation time of high-energy particles, that is:

[0041] .

[0042] Furthermore, the specific content of step 7 includes: by adjusting different parameters of space weather, including solar wind dynamic pressure, solar wind speed, interplanetary magnetic field strength, magnetic dip angle, Dst index, repeating steps 1-step 6, and calculating the relationship between the relaxation time and various parameters.

[0043] In the second aspect, the present invention provides an evaluation system for relaxation time in the process of radiation belt modeling, which includes:

[0044] Spatial grid and coordinate system configuration unit: used to divide three-dimensional spatial grids and establish a local coordinate system;

[0045] Particle management and tracking unit: used to determine the number of passing particles and track the motion state of high-energy particles;

[0046] Data statistics and distribution analysis unit: statistically analyze the particle distribution state at different time points, compare the distribution differences at adjacent times, and judge whether the convergence threshold is reached;

[0047] Relaxation time calculation unit: used to calculate the relaxation time under different space weather conditions;

[0048] 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 based on this to store the mapping relationship between input parameters and relaxation times, supporting fast retrieval and comparative analysis.

[0049] In a third aspect, the present invention provides an electronic device, including a processor and a memory, with computer instructions stored on the memory, and the processor is configured to run the computer instructions stored on the memory to implement the steps of a method for evaluating relaxation time in the process of radiation belt modeling.

[0050] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer instructions, and the computer instructions are used to cause a computer to execute the steps of a method for evaluating relaxation time in the process of radiation belt modeling.

[0051] Based on the above technical solutions, the embodiments of the present invention can at least produce the following technical effects:

[0052] The method for evaluating relaxation time proposed by the present invention can significantly span the radiation belt and near-Earth space in terms of the targeted spatial range, and the calculated relaxation time can provide necessary technical support for communication, navigation, etc. At the same time, due to its potential role in space security, there is an urgency. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0054] Figure 1 is the technical flow chart of the embodiments of the present invention;

[0055] Figure 2 is the distribution image of protons in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of the technical solutions results in contradictions 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.

[0057] Please refer to FIG. 1. A method for evaluating relaxation time in the process of radiation belt modeling includes the following steps:

[0058] Step 1, Spatial 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 the accuracy requirements.

[0059] Step 2, Establish local coordinate systems, including the FAC coordinate system and the NEC / ENU coordinate system. Among them, the FAC coordinate system is a field-aligned coordinate system used to establish the dependence of the pitch angle, and the NEC / ENU coordinate system is the north-east-down and north-east-up coordinate system used to establish the dependence of the azimuth angle.

[0060] Step 3, Place high-energy particles with different angles (including azimuth angle, pitch angle, etc.) and different energies at the grid points according to requirements; the number of particles placed is determined by the integral formula:

[0061] ;

[0062] where x, y, and z represent the three-dimensional coordinate positions of the particles respectively, is the pitch angle of the high-energy particle, is the particle energy, is the azimuth angle of the particle.

[0063] 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 the particles: 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 exit condition of the particles is set as: the outer boundary is the direction of the magnetopause, and the inner boundary is 1 Re;

[0064] Use the high-energy particle motion equation (there are two methods here. The first is to use the simple Newton-Lorentz equation, and the second is to use the complex stochastic partial differential equation system).

[0065] First, for the Newton-Lorentz equation (under the action of the background magnetic field), the motion of high-energy particles in the magnetosphere is described by the Lorentz equation , where is the particle momentum, is the particle motion velocity, 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 trace the particle motion state backward.

[0066] Second, for the stochastic partial differential equation method (under the condition of diffusion effect), use the stochastic partial differential equation method to convert the Fokker-Planck equation into a six-dimensional stochastic partial differential equation system and trace the particle motion state backward.

[0067] Step 5, counting the motion states of particles at different time intervals, and generating a particle distribution state image of the entire calculation area;

[0068] 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);

[0069] The high energy particle relaxation time function is expressed as , which is a function of coordinate position, energy, pitch angle, and azimuth;

[0070] The particle distribution state function is expressed as , which is also a function of coordinate position, energy, pitch angle, and azimuth;

[0071] 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;

[0072] 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;

[0073] At any time , the particle distribution function satisfies:

[0074] and ;

[0075] 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:

[0076] .

[0077] Step 7, calculating the relaxation time function for different space weather conditions;

[0078] 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.

[0079] Step 8: Establish a database, create a data volume for the above various calculation input parameters and output parameters, and analyze to obtain the dependence of the relaxation time on each input parameter;

[0080] Specifically, the database contains the quantitative relationships between the relaxation time and the solar wind dynamic pressure, solar wind velocity, interplanetary magnetic field strength, magnetic dip angle, and Dst index.

[0081] Step 9: Apply it to the calculation of the actual radiation belt relaxation time, and evaluate the time for high-energy particles to reach a steady-state distribution under different space weather conditions.

[0082] Using the above method, calculate the 1-hour distribution image of protons with a rigidity of 200 MV corresponding to high-energy protons in the range of [0, 8] in the X-axis direction and [0, 8] in the Z-axis direction during geomagnetically quiet periods under the background of the dipole field, as Figure 2 shown (since it involves a large number of single-particle motion calculation processes, only the results up to the 5th step are schematically shown here, and it is not the final relaxation time result).

[0083] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended 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; 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: ； 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 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.

6. 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 5 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.

7. 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 1-5.

8. 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 5.

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