A method of calculating foF2 affected by weak geomagnetic activity

Abstract

The application discloses a method for calculating foF2 affected by weak geomagnetic activity and relates to the technical field of ionospheric physical research and application. The method comprises the following steps: acquiring an Ap index and a Dst index, wherein the Ap index and the Dst index satisfy a first condition; acquiring an ionospheric solar activity index S by processing an F10.7 index; calculating a solar activity influence value T by using a Fourier polynomial; acquiring an actual observation value R; and acquiring a weak geomagnetic activity influence value G by using the actual observation value R and the solar activity influence value T. The method can effectively separate the influence of weak geomagnetic activity on foF2 when studying foF2 by improving the F10.7 index and further putting forward the ionospheric solar activity index S, and is favorable for more directly studying the influence of weak geomagnetic activity on foF2 and the ionosphere. The method is easy to operate, simple in data selection and easy to realize.

Description

Technical Field

[0001] This invention belongs to the field of ionospheric physics research and application technology, and in particular relates to a method for calculating foF2 affected by weak geomagnetic activity. Background Technology

[0002] Ionospheric radio wave propagation is well-known for long-distance high-frequency (HF) communication. During adverse space weather, the ionosphere becomes highly unstable, interfering with the operation of technologies such as HF communications and affecting other applications such as navigation and positioning. This impact can be observed in multiple data sources, such as ion detection instruments and the Global Positioning System (GPS). The highly dynamic and variable F2 layer of the ionosphere can lead to unreliable HF communication. Near-real-time monitoring of the ionospheric response under geomagnetic storm conditions is crucial for reliable communication, while the ionospheric response under weak geomagnetic activity plays a vital role in improving the accuracy and stability of various communication systems.

[0003] Ionospheric activity indices play an important role in studying the characteristic parameters of the ionosphere. Many studies have been conducted to establish ionospheric activity indices, such as (1) the ionospheric T index, which is a global index based on the number of sunspots; (2) the monthly ionospheric index MF2 for the Northern Hemisphere, which is to better predict foF2 in the long term, rather than just using the direct sunspot number (R12); and (3) the planetary ionospheric storm index (Wp), which is derived from the GPS-IONEX map of the total vertical electron content (VTEC), and is used to facilitate the observation of the decrease or increase in electron density in the ionosphere.

[0004] The critical frequency of the F2 layer (foF2) is one of the most important parameters in the ionosphere. Most current foF2 modeling methods combine solar activity index and geomagnetic activity index, which means that when analyzing the effects of geomagnetic activity alone, the variation of foF2 cannot fully explain the disturbance effect of geomagnetic activity on the ionosphere.

[0005] Many factors characterize the variation between weak geomagnetic activity and foF2. Key factors include solar events, Earth's motion (seasonal variations), and external variability factors related to the interaction between the solar wind and the magnetosphere. Weaker geomagnetic activity occurs more frequently than ionospheric storms, yet the ionosphere's response to it is studied far less. One reason is that it is often difficult to distinguish the effects of weaker geomagnetic activity from the complex diurnal variability of the ionosphere caused simultaneously by solar irradiance, geomagnetic activity, and waves from the lower atmosphere. Even so, the effects of weak geomagnetic activity can still be identified under certain specific conditions. Summary of the Invention

[0006] The object of the present invention is to provide a method for calculating foF2 affected by weak geomagnetic activity, which uses the ionospheric solar activity index S to isolate foF2 affected by weak geomagnetic activity, facilitating a more intuitive study of the impact of weak geomagnetic activity on the ionosphere, especially the impact of weak geomagnetism on foF2.

[0007] The object of the present invention can be achieved through the following technical solutions:

[0008] An embodiment of the present application provides a method for calculating foF2 affected by weak geomagnetic activity, including:

[0009] Obtain the Ap index and the Dst index, where the Ap index and the Dst index satisfy the first condition;

[0010] Obtain the ionospheric solar activity index S by processing the F10.7 index;

[0011] Calculate the solar activity influence value T using a Fourier polynomial;

[0012] Obtain the actual observation value R;

[0013] Obtain the weak geomagnetic activity influence value G using the actual observation value R and the solar activity influence value T.

[0014] As a preferred technical solution of the present invention, the first condition is that the Ap index is within the first index range and / or the Dst index is within the second index range.

[0015] As a preferred technical solution of the present invention, the first index range is 8 < Ap < 30, and the second index range is -30 < Dst < 10.

[0016] As a preferred technical solution of the present invention, the F10.7 index is weighted, and the solar activity index S is obtained through the formula to obtain the solar activity index S.

[0017] As a preferred technical solution of the present invention, the solar activity influence value T is obtained through the formula

[0018]

[0019] to obtain the solar activity influence value T.

[0020] As a preferred technical solution of the present invention, the weak geomagnetic activity influence value G is obtained through the formula to obtain the weak geomagnetic activity influence value G.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) This invention proposes an ionospheric solar activity index S by improving the F10.7 index, which can effectively separate the influence of weak geomagnetic activity on foF2 when studying foF2, and is conducive to a more intuitive study of the influence of weak geomagnetic activity on foF2 and the ionosphere.

[0023] (2) The method proposed in this invention is highly operable, easy to select data, and easy to implement. Attached Figure Description

[0024] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0025] Figure 1 A flowchart illustrating the steps of a method for calculating foF2 affected by weak geomagnetic activity, provided in an embodiment of this application;

[0026] Figure 2 A flowchart illustrating the steps of a method for calculating foF2 affected by weak geomagnetic activity, provided in another embodiment of this application. Detailed Implementation

[0027] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description relating to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods and systems consistent with some aspects of this application as detailed in the appended claims.

[0028] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0029] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0030] Example 1

[0031] Please see Figure 1 This application provides a method for calculating foF2 affected by weak geomagnetic activity, the method comprising:

[0032] S101: Obtain the Ap index and Dst index, where the Ap index and Dst index satisfy the first condition;

[0033] S102: Obtain the ionospheric solar activity index S by processing the F10.7 index;

[0034] S103: Calculate the solar activity impact value T using Fourier polynomials;

[0035] S104: Obtain the actual observed value R;

[0036] S105: Obtain the influence value G of weak geomagnetic activity using the actual observed value R and the influence value T of solar activity.

[0037] The following will provide a detailed explanation of steps S101 to S105.

[0038] The geomagnetic activity index is a commonly used indicator to measure the strength of geomagnetic activity. The Ap index and the Dst index are different types of geomagnetic activity indices.

[0039] The ionosphere is closely coupled with the magnetosphere and solar wind. When energy from the magnetosphere and solar wind is deposited into the high-latitude ionosphere and upper atmosphere, the ionosphere is significantly disturbed. Generally, this energy deposition is very frequent, usually weak, and occasionally strong. Accompanying this energy deposition, space current systems, including ionospheric currents, are disturbed. Therefore, the magnetic field measured on the ground is disturbed, and the degree of disturbance is positively correlated with the energy deposition. Consequently, various geomagnetic activity indices have been developed from ground magnetic field measurements to estimate the intensity of energy deposition. Geomagnetic activity indices have been widely used in space physics research and space weather applications.

[0040] Different types of variability in the ionosphere are influenced by many interrelated driving factors, which can be summarized as follows: (a) solar ionizing radiation; (b) geomagnetic activity; and (c) meteorological influences. In practical research utilizing foF2, the factors that can be artificially controlled are mainly (a) and (b).

[0041] Regarding step S101, obtain the Ap index and Dst index from the research data, and determine whether these two indices meet the first condition defined in this application. If the first condition is met, proceed to step S102.

[0042] Among them, the Ap index and the Dst index are used to measure the above factor (b). Among them, the Ap index represents the global daily average geomagnetic disturbance intensity, with the unit of 2 nT. The larger the value, the stronger the intensity; the Dst index is designed to measure the disturbance of the magnetic field near the equator by the current flowing above the ionosphere, with the unit of nT. The Dst index is calculated by monitoring the change of the geomagnetic activity intensity over time and the ring current. Its data source is provided by 4 low-latitude observation stations, which are arranged at relatively regular intervals in longitude. The high-energy cations generated by the geomagnetic storm drift westward, generating a westward flowing current. Therefore, the disturbed Dst index is negative, and the smaller the value, the stronger the disturbance. It also represents the global geomagnetic disturbance intensity, but the Dst index has a higher resolution, with a value every 1 hour interval.

[0043] In an embodiment provided by the present application, the Ap index is within the first index range and / or the Dst index is within the second index range.

[0044] In an embodiment provided by the present application, the first index range is 8 < Ap < 30, and the second index range is -30 < Dst < 10.

[0045] Specifically, according to the content of the above embodiment, when the Ap index and the Dst index meet the above first condition, step S102 can be executed. The above first condition is: the Ap index is within the first index range and / or the Dst index is within the second index range; and the first index range is 8 < Ap < 30, and the second index range is -30 < Dst < 10. Therefore, generally speaking, when the Ap index and the Dst index meet any one of the following two conditions: (1) 8 < Ap < 30, (2) -30 < Dst < 10, the subsequent step S102 can be executed. Of course, if both conditions (1) and (2) are met simultaneously, the subsequent step S102 can also be executed.

[0046] Regarding step S102, by performing weighted processing on different types of F10.7 indices, an improved F10.7 index is obtained, which is called the ionospheric solar activity index S and is used to calculate the foF2 value under solar forcing.

[0047] In an embodiment provided by the present application, the formula for calculating the solar activity index S is S=(0.35F 10.7 +0.65F 10.7A ), where F 10.7 is the F10.7 value on a certain determined day, and F 10.7A is the 81-day average running value of F10.7.

[0048] The F10.7 index is a commonly used index to measure factor (a). It represents the solar radio flux at a wavelength of 10.7 cm (2800 MHz), and is a typical parameter used to measure solar radiation activity, reflecting its intensity. The unit is sfu, where sfu = 10-10. -22 Wgm -2 ·Hz -1 .

[0049] Solar forcing can cause changes in the solar cycle and short-term diurnal variations in the ionosphere. In this embodiment, the solar forcing effect should be excluded in order to determine the influence of weak geomagnetic activity on the ionospheric parameter foF2.

[0050] Regarding step S103, the solar activity index S is obtained through step S102 above. Then, the foF2 value affected by solar activity is calculated using a third-order Fourier polynomial. The calculation formula is as follows:

[0051] ;

[0052] in, , , , , , , , denoted as the Fourier coefficient, representing the influence of the sun on foF2. It indicates the day of the year. The solar activity index in step S102 The value is the value from the previous day. Research has shown that short-term EUV and F10.7 changes are asynchronous; F10.7 changes lead EUV changes, with a typical time shift of one day between daily EUV and F10.7. Therefore, when using the F10.7 index to estimate solar EUV, this one-day lag of EUV to F10.7 should be taken into account.

[0053] It should be noted that the EUV mentioned above refers to solar extreme ultraviolet radiation, which is electromagnetic radiation with wavelengths between 124 nm and 10 nm. This type of radiation produced by the sun is called solar extreme ultraviolet radiation. Although solar extreme ultraviolet radiation ionizes the upper atmosphere to form the ionosphere, it is not continuously measured. Therefore, for historical ionospheric measurements, various solar proxy indices are typically used, such as the widely used F10.7 index, to estimate the solar forcing on the ionosphere. The solar periodic effect of EUV can be well captured by using a nonlinear fit between ionospheric electron density and solar proxy. However, for short-term EUV variations, the solar proxy is not as effective as for solar periodic variations.

[0054] The slope of the relationship between solar extreme ultraviolet radiation (EUV) and F10.7 over a short period is variable and significantly lower than the slope of EUV and F10.7 over a solar cycle. Therefore, embodiments of this application propose an ionospheric solar activity index S, which is a weighted average of short-term F10.7 and F10.7 changes over a solar cycle, to improve the F10.7 index and eliminate the slope difference between EUV and F10.7 across short-term and solar cycle timescales.

[0055] Compared with the solar F10.7 measured by current instruments, the improved index S has a better ability to estimate EUV. The ionospheric solar activity index S proposed in this application makes its slope of change with EUV in the short term the same as the slope of change of F10.7 with EUV in the long term. Using this index, the influence of weak geomagnetic activity on foF2 and the ionosphere can be more clearly highlighted.

[0056] Regarding steps S104-S105, the observed foF2 value R is obtained by measuring with scientific instruments. The most commonly used observation tool is a ground-based vertical sounder. The observed foF2 value is obtained by analyzing the ionization map obtained from the vertical sounder. Since the foF2 value affected by solar activity calculated in step S103 is a daily value, while the time resolution of the actual foF2 value measured by tools such as ionospheric vertical sounders may be 0.5 hours, 1 hour, etc., it is necessary to convert the time resolution of the actually measured foF2 value to one day. Subtracting the foF2 value T affected by solar activity from the observed foF2 value R yields the foF2 value G affected by weak geomagnetic activity.

[0057] In one embodiment provided in this application, the formula is used. Obtain the influence value G of the aforementioned weak geomagnetic activity.

[0058] The method proposed in this invention is more applicable when solar activity is weak, because when solar activity is weak, solar irradiance is relatively stable, which increases the importance of geomagnetic activity to the diurnal variability of the ionosphere and is beneficial for detecting the influence of weak geomagnetic activity.

[0059] In summary, this invention proposes an ionospheric solar activity index S by improving the F10.7 index. When studying foF2, this method can effectively separate the influence of weak geomagnetic activity on foF2, which is beneficial for a more intuitive study of the impact of weak geomagnetic activity on foF2 and the Earth's ionosphere.

[0060] Compared with the solar F10.7 obtained by current instruments, the improved ionospheric solar activity index S has a better ability to estimate EUV. In the study of long-term weak geomagnetic activity, we use the ionospheric solar activity index S to improve the effectiveness of solar EUV estimation.

[0061] Furthermore, the method proposed in this invention is highly operable, easy to select data, and easy to implement.

[0062] Example 2

[0063] This application provides a set of experiments and experimental data to further support the above-mentioned method for calculating foF2 affected by weak geomagnetic activity. The experiments and experimental data will be described in detail below.

[0064] 2017 fell within the 24th solar cycle, which is the least solar active cycle in the last 100 years. This provided an excellent opportunity to study the impact of weak geomagnetic activity on foF2 and the ionosphere. In this experiment, the four observation stations selected were Hainan Station (20°N, 110.34°E), Kunming Station (25.64°N, 103.72°E), Changchun Station (43.84°N, 125.28°E), and Manzhouli Station (49.56°N, 117.52°E). The foF2 data measured at these four stations in 2017 were processed using the method proposed in this application.

[0065] Please see Figure 2 This application provides a method for calculating foF2 affected by weak geomagnetic activity, which specifically includes the following steps:

[0066] S201: Determine the F10.7 value for a given day. And the 81-day average running value of F10.7 ;

[0067] S202: Calculate the ionospheric solar activity index S;

[0068] Specifically, in this embodiment, we refer to the F10.7 index modified using formula (1) as the ionospheric solar activity index S. The S index is used to calculate the solar forcing effect. The method for calculating the S index is as follows:

[0069] Formula (1)

[0070] in and This has been determined in step S201.

[0071] S203: Calculate foF2 affected by solar activity using Fourier polynomials;

[0072] Specifically, the value of foF2 T affected by solar activity is calculated using a third-order Fourier polynomial, as shown in the following formula (2):

[0073] Formula (2)

[0074] S204: The foF2 value G, which is influenced by weak geomagnetic activity, was isolated;

[0075] Specifically, the foF2 value affected by weak geomagnetic activity is obtained by subtracting the foF2 value T calculated in step S203 from the actually observed foF2 value R. The calculation formula is shown in the following formula (3):

[0076] Formula (3)

[0077] S205: Analyze the impact of weak geomagnetic activity on foF2.

[0078] The method proposed in this application can completely separate the influence of weak geomagnetic activity on foF2, making the effect of weak geomagnetic activity on the ionosphere more prominent, and at the same time, it is beneficial to study the coupling effect between the ionosphere and the magnetosphere.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for calculating foF2 affected by weak geomagnetic activity, characterized in that, The method includes: Obtaining an Ap index and a Dst index, where the Ap index and the Dst index satisfy a first condition; Obtaining an ionospheric solar activity index S by processing the F10.7 index; Calculating a solar activity influence value T using a Fourier polynomial; Obtaining an actual observation value R; Obtaining a weak geomagnetic activity influence value G using the actual observation value R and the solar activity influence value T; Through the formula Obtain the solar activity impact value T, where, , , , , , , , Here are the Fourier coefficients, representing the influence of the sun on foF2. Indicates the day of the year. Solar Activity Index The value of the previous day; Through formula Obtain the influence value G of the weak geomagnetic activity.

2. The method for calculating foF2 affected by weak geomagnetic activity according to claim 1, characterized in that, The first condition is that the Ap index is within a first index range and / or the Dst index is within a second index range.

3. The method for calculating foF2 affected by weak geomagnetic activity according to claim 2, characterized in that, The first index range is 8 < Ap < 30, and the second index range is -30 < Dst < 10.

4. The method for calculating foF2 affected by weak geomagnetic activity according to claim 1, characterized in that, The F10.7 index is weighted and processed using the formula. Obtain the solar activity index S, where This represents the 81-day average operating value of F10.7.

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