Method for calculating three-dimensional distribution of earth magnetic layer pole gap region parameters

Abstract

The invention provides a method for calculating three-dimensional distribution of parameters in a pole gap region of an earth magnetic layer. According to the technical scheme, an earth magnetic layer polar gap region boundary is calibrated according to mass satellite observation data; and two-dimensional distribution grids of the earth magnetic layer pole gap region in the X direction and the Z direction are calculated according to the boundary. The X direction refers to the direction pointing to the sun from the earth center, and the Z direction refers to the direction of the earth magnetic field dipole axis. Taking a magnetic place corresponding to a satellite observation point as a Y1 direction; uniformly dividing the Z direction into a plurality of intervals according to a fixed step length; uniformly dividing the Y1 direction into a plurality of intervals according to a fixed step length; and after the division, the calculated parameter value of each two-dimensional grid region is the average value of observation values of satellites passing through the two-dimensional grid regions. According to the invention, the parameter distribution characteristics of the fan-shaped earth magnetic layer pole gap region can be fully expressed, and the solar wind-magnetic layer-ionized layer coupling process can be better researched.

Description

Technical Field

[0001] The invention relates to the field of space physics, and in particular to an algorithm for studying the three-dimensional distribution of parameters in the polar gap region of the earth's magnetosphere. Background Art

[0002] The layers on the surface of the Earth are the atmosphere, ionosphere and magnetosphere. Among them, the magnetosphere is the interaction between the solar wind and the Earth's magnetic field. The polar gap region of the magnetosphere is an important channel for solar wind plasma particles to enter the magnetosphere and ionosphere, and the charged particles ascending from the ionosphere can also escape into the solar wind through the polar gap region. In this way, the polar gap region closely links the solar wind, magnetosphere and ionosphere. The study of the polar gap region has very important scientific significance for understanding and understanding the coupling process of the solar wind-magnetosphere-ionosphere. Statistical research is an important means to understand and recognize the polar gap region of the Earth's magnetosphere. For example, scientists previously used the DMSP satellite to select 12,000 low-altitude Earth magnetosphere polar gap region crossing events as a database, and studied the influence of the Earth's dipole inclination on the position of the low-altitude magnetosphere polar gap region. They found that at low altitudes, as the dipole inclination increases, the low-altitude magnetosphere polar gap region will move toward the equator of the sunward side, and the low-altitude magnetosphere polar gap region is closer to the dipole axis. The results also show that when the interplanetary magnetic field is southward, the low-altitude magnetosphere polar gap region moves 0.76 degrees to low latitudes for every 1nT increase in IMF-Bz, while when the interplanetary magnetic field is northward, the low-altitude magnetosphere polar gap region has no obvious position change. The magnetic fields near the low-altitude magnetosphere polar gap region with different dipole inclinations are integrated in the geocentric magnetosphere equatorial coordinate system using the five-year HEOS satellite low-altitude magnetosphere polar gap region detection data, and the magnetic field distribution near the low-altitude polar gap region is given.

[0003] However, previous statistical studies have shown that the polar gap region of the Earth's magnetosphere is affected by a variety of complex conditions such as dipole inclination, interplanetary magnetic field, and solar wind dynamic pressure, so it is difficult to determine the boundary of the polar gap region of the Earth's magnetosphere, which will lead to difficulties in studying the three-dimensional distribution of parameters such as the magnetic field and plasma in the polar gap region of the Earth's magnetosphere. Articles published by the inventors: Xiao, C., Liu, WL, Zhang, DJ, and Zhang, Z. (2020). A normalized statistical study of Earth's cusp region based on nine-years of Cluster measurements. Earth Planet. Phys., 4 (3), 266-273. doi: 10.26464 / epp2020031. This article mainly proposes a method for calculating the two-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere. However, this article does not provide a method for constructing a three-dimensional space and how to calculate the parameters of the polar gap region of the Earth's magnetosphere in three-dimensional space. At present, no literature has been found that proposes a method for calculating the three-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere. Summary of the invention

[0004] The present invention provides a new method for calculating the three-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere.

[0005] The technical solution of the present invention is a new method for calculating the three-dimensional distribution of parameters of the polar gap region of the earth's magnetosphere, which calibrates the boundary of the polar gap region of the earth's magnetosphere based on a large amount of satellite observation data; and calculates the two-dimensional distribution grid of the polar gap region of the earth's magnetosphere in the X direction and the Z direction based on the boundary. The X direction refers to the direction from the center of the earth to the sun, and the Z direction is the direction of the dipole axis of the earth's magnetic field.

[0006] It is characterized by taking the magnetic local time (MLT) corresponding to the satellite observation point as Y 1 Direction, in Y 1 The value of each point in the direction is determined by the coordinates in the Solar Magnetic Coordinates (SM coordinate system). 1 The Z plane is divided into appropriate two-dimensional grid areas. When dividing, the Z direction is evenly divided into several intervals according to a fixed step size; then the Y 1 The direction is evenly divided into several intervals according to a fixed step size. After the above division, the parameter value of each two-dimensional grid area is calculated as: the average value of the satellite observation value passing through the two-dimensional grid area.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] The present invention proposes an algorithm for studying the three-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere. On the basis of calculating the two-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere, a circular magnetic local time is proposed as the Y of the three-dimensional distribution. 1 The directional coordinate system axis can fully express the parameter distribution characteristics of the fan-shaped polar gap region of the Earth's magnetosphere, which is convenient for better studying the coupling process of the solar wind-magnetosphere-ionosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of the principle flow of the present invention;

[0010] Figure 2 The distribution of the parameters of the polar gap region of the Earth's magnetosphere in the XZ plane calculated using a specific embodiment of the present invention;

[0011] Figure 3 The distribution of the parameters of the polar gap region of the Earth's magnetosphere in the YZ plane calculated using a specific embodiment of the present invention. DETAILED DESCRIPTION

[0012] like Figures 1 to 3 As shown, here we take Cluster satellite data as an example to demonstrate the specific method steps of this algorithm for studying the three-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere, as follows:

[0013] Step 1: Calculate the boundary of the polar gap region of the Earth's magnetosphere by calculating a large amount of satellite observation data. For example, using the Cluster-3 satellite (C3 satellite) to obtain the Earth's magnetosphere ion data from 2001 to 2009, it was determined that the preliminary range of the polar gap region of the Earth's magnetosphere is -1 <X<10R E , -8 <Y<8R E and 0 <Z<10R E , R E Represents the radius of the Earth. Based on the ion characteristics of typical Earth magnetosphere polar gap crossing events (such as high density, low velocity, and wide energy spectrum), 470 Earth magnetosphere polar gap crossing events in the northern hemisphere were manually selected from the C3 satellite ion data, giving 470 boundary positions of the Earth magnetosphere polar gap.

[0014] Step 2: Using 470 boundary positions, the width W of the polar gap region in the Earth's magnetosphere in the X direction was obtained by fitting method. X The relationship between the change in the Z direction can be expressed by W X =0.43-0.17*z+0.064*z 2 Indicates that z represents the value in the Z direction.

[0015] Step 3: Using 470 boundary positions, the relationship between the X-direction and Z-direction variation of the middle position of the polar gap region of the Earth's magnetosphere is obtained by fitting method. This relationship can be expressed as x=0.731×z-1.43, where x represents the value in the X-direction.

[0016] Step 4: Convert the X-direction value x and the Y-direction value y of the boundary position of the polar gap region of the Earth's magnetosphere into magnetic local time, and use the magnetic local time as the Y1 direction. The specific calculation process is MLT = arctan (y / x), where the negative X direction is MLT = 0h and the negative Y direction is MLT = 6h. Then, divide the polar gap region into appropriate two-dimensional grid areas in the Y1Z plane, here divided into Z = 2: 0.2: 8RE, MLT = 8: 0.5: 16h, where h represents hours.

[0017] Step 5: Map the measured values ​​of all the research parameters of the Earth's magnetosphere interpolar gap crossing events (mainly magnetic pressure, thermal pressure, dynamic pressure and electron number density) to the corresponding two-dimensional grid, and finally average the values ​​in the two-dimensional grid area to obtain the three-dimensional distribution of the parameters in the Earth's magnetosphere interpolar gap region as a whole, as shown in the following figure. Figure 2 and Figure 3 shown. Figure 2 It is the distribution in the XZ plane. (a) to (e) represent the distribution of magnetic pressure, thermal pressure, dynamic pressure, disturbed magnetic pressure and electron number density. Figure 2 Yes 1 The distribution in the Z plane, (a) to (e) show the distribution of magnetic pressure, thermal pressure, dynamic pressure, disturbed magnetic pressure and electron number density.

Claims

1. A new method for calculating the three-dimensional distribution of parameters in the Earth's magnetosphere polar gap region. The boundary of the Earth's magnetosphere polar gap region is calibrated based on a large amount of satellite observation data; the two-dimensional distribution grid of the Earth's magnetosphere polar gap region in the X direction and the Z direction is obtained based on the boundary calculation; the X direction refers to the direction from the center of the earth to the sun, and the Z direction is the direction of the Earth's magnetic field dipole axis; It is characterized in that The magnetic local time corresponding to the satellite observation point is taken as Y 1 Direction, in Y 1 The value of each point in the direction is determined according to the coordinates in the solar magnetic field coordinate system; then the polar gap region of the Earth's magnetosphere is determined in Y 1 The Z plane is divided into appropriate two-dimensional grid areas. When dividing, the Z direction is evenly divided into several intervals according to a fixed step size; then the Y 1 The direction is evenly divided into several intervals according to a fixed step size; after the above division, the parameter value of each two-dimensional grid area is calculated as: the average value of the satellite observation values ​​crossing the two-dimensional grid area.

2. The method for calculating the three-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere according to claim 1, characterized in that: The width of the polar gap region of the Earth's magnetosphere in the X direction is W X The relationship with the change in the Z direction is expressed by W X =0.43-0.17*z+0.064*z 2 Indicates that z represents the value in the Z direction.

3. The method for calculating the three-dimensional distribution of parameters in the polar gap region of the Earth's magnetosphere according to claim 2, characterized in that: The relationship between the change in the middle position of the polar gap region of the Earth's magnetosphere in the X direction and the Z direction is expressed by x=0.731×z-1.43, where x represents the value in the X direction.

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