A method for identifying sudden ionospheric disturbance events based on ionospheric vertical sounding data

Abstract

The present invention discloses a method for identifying sudden ionospheric disturbance events based on ionospheric vertical sounding data, comprising the following steps: Step 1, collecting and organizing fmin and foF2 data from each ionospheric observation station during a historical M5.0 solar flare eruption that occurred during daytime in my country; Step 2, calculating the ratio of fmin to foF2 data at each ionospheric observation station at the corresponding time, statistically analyzing the distribution of fmin / foF2, and determining the different intensity levels of ionospheric absorption at each ionospheric observation station; Step 3, determining the intensity level of the sudden ionospheric disturbance event. The method for identifying sudden ionospheric disturbance events disclosed by the present invention utilizes the minimum echo frequency of the ionospheric vertical sounding ionogram and the ionospheric critical frequency to calculate an absorption index representing the degree of ionospheric absorption. This method can simply and directly characterize the degree of ionospheric absorption in a certain region and can provide ionospheric absorption information for different regions of my country for shortwave and other electronic information systems.

Description

Technical Field

[0001] The present invention belongs to the field of ionospheric physics research, and in particular relates to a method for identifying sudden ionospheric disturbance events based on ionospheric vertical detection data in this field. Background Art

[0002] Solar activity strongly controls the behavior of the ionosphere. A solar flare is a sudden brightening of a localized region of the solar atmosphere, accompanied by enhanced radiation and particle events in various electromagnetic bands. A solar flare can release 10 32 During a solar flare, the solar radiation The intensity of soft X-rays can reach 10 times that of a quiet day. 3 These soft X-rays and ultraviolet rays generated by the sun travel to the earth at the speed of light (about 8.3 minutes).

[0003] When electromagnetic waves propagate through plasma, the wave's electric vector causes electrons to move. Collisions between electrons and other particles cause the wave's amplitude to decay, converting ordered momentum into random thermal motion. If there are no collisions, the oscillating electrons (or ions) will radiate all their energy, which is then returned to the electromagnetic wave. When collisions occur, some of this energy is transferred to neutral molecules, ultimately converting into heat. During a solar flare, the electron density in the D layer of the ionosphere on the dayside of Earth increases significantly, increasing collisions between electrons and neutral molecules and leading to increased energy loss in the electromagnetic wave signal. During a solar flare, shortwave signal propagation on the dayside is severely impacted or even interrupted. This direct effect associated with a solar flare is called a sudden ionospheric disturbance.

[0004] Currently, there is no quantitative method for identifying sudden ionospheric disturbances (SIDs). The meteorological industry standard "Classification of Sudden Ionospheric Disturbances" uses satellite carrier phase observations to calculate the TEC increase caused by solar flares and classify the intensity of SIDs. While using phase TEC can detect small disturbances in the ionosphere, it may also produce TEC increases caused by other factors, leading to erroneous judgments of SIDs. There are various other methods for detecting ionospheric absorption, such as pulse reflection, ionospheric relative turbidity meter, and continuous wave methods. However, these methods all have limitations, such as difficulty in calibration and sensitivity to interference. Using an empirical model based on soft X-ray flux, the global distribution of ionospheric D-layer absorption can be calculated. Due to the influence of multiple factors (such as the time of occurrence of the X-ray flare and the ground location), the degree of ionospheric disturbance caused by X-ray flares of the same intensity can vary. Therefore, monitoring and identifying SIDs using solar X-ray observations alone is not feasible. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a simple and easy-to-implement method for identifying sudden ionospheric disturbance events based on ionospheric vertical detection data.

[0006] The present invention adopts the following technical solutions:

[0007] A method for identifying sudden ionospheric disturbance events based on ionospheric vertical sounding data is improved in that it includes the following steps:

[0008] Step 1: Collect and organize the fmin and foF2 data of each ionospheric observatory during the M5.0 historical solar flare eruptions that occurred during the daytime in my country. The daytime period refers to 07:00-19:00 Beijing time.

[0009] Step 2: Calculate the ratio of fmin to foF2 at each ionospheric observation station at the corresponding time, statistically analyze the distribution of fmin / foF2, and determine the different intensity levels of ionospheric absorption at each ionospheric observation station based on the distribution;

[0010] Step 3: Calculate the ionospheric absorption characterization index of the entire region based on the fmin / foF2 data of each ionospheric observation station, and determine the intensity level of the sudden ionospheric disturbance event.

[0011] Furthermore, the step 1 is specifically as follows:

[0012] Step 1A: Based on the historical solar flare event set published by SWPC, select events with a solar flare magnitude of M5.0 or above and a solar flare start time between 07:00 and 19:00 Beijing time;

[0013] Step 1B, collect fmin and foF2 data from each ionospheric observation station during the start and end of the solar flare, and preprocess the data as follows: if the foF2 data in the ionogram cannot be read, replace the foF2 value with the monthly median value; if both fmin and foF2 data are missing, discard the data set; when the fmin measurement value is symbol "B", it is full absorption, in which case fmin = 1 and foF2 = 1.

[0014] Furthermore, the step 2 is specifically as follows:

[0015] Step 2A, calculate the ratio of fmin to foF2 data at each ionospheric observation station at the corresponding time, absorption index IAi = fmin / foF2;

[0016] Step 2B, taking the fmin / foF2 values ​​of each ionospheric observation station as a whole data set, statistically analyzing the distribution of fmin / foF2, and obtaining the proportion of samples in different fmin / foF2 value intervals to the total samples;

[0017] Step 2C, determine the fmin / foF2 value ranges for weak, medium, and strong levels of ionospheric absorption based on the distribution of fmin / foF2: weak: 0.5≤IAi<0.65; medium: 0.65≤IAi<0.8; strong: IAi≥0.8.

[0018] Furthermore, the step 3 is specifically as follows:

[0019] Step 3A: Based on the ionospheric absorption degree judgment results of each ionospheric observation station, the conditions for reaching a sudden ionospheric disturbance event are determined: if more than one-third of the ionospheric observation stations experience shortwave absorption of weak or above level, it is considered that a sudden ionospheric disturbance event has occurred.

[0020] Step 3B, average the fmin / foF2 data that reach the weak absorption level to obtain an ionospheric absorption characterization index IA that characterizes the degree of regional ionospheric absorption:

[0021]

[0022] In the above formula, N is the number of ionospheric observation stations that have reached the weak absorption level;

[0023] Step 3C: Determine the value range of the ionospheric absorption characterization index IA for different levels of sudden ionospheric disturbance events:

[0024] Red: 0.5≤IA<0.65; Orange: 0.65≤IA<0.8; Yellow: IA≥0.8.

[0025] The beneficial effects of the present invention are:

[0026] The method for identifying sudden ionospheric disturbance events disclosed in the present invention uses the minimum echo frequency fmin of the ionospheric vertical sounding ionogram and the critical frequency foF2 of the ionospheric F2 layer to calculate an absorption index representing the degree of ionospheric absorption. This method can simply and directly characterize the degree of ionospheric absorption in a certain area and provide ionospheric absorption degree information in different regions of my country for shortwave and other electronic information systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the method for identifying sudden ionospheric disturbance events disclosed in the present invention;

[0028] Figure 2 is the statistical distribution map of the ionospheric absorption index;

[0029] Figure 3 is the absorption index of each ionospheric observation station on August 4, 2011;

[0030] Figure 4It is the average ionospheric absorption index of various regions in my country on August 4, 2011;

[0031] Figure 5 is the absorption index of each ionospheric observation station on August 18, 2012;

[0032] Figure 6 It is the average ionospheric absorption index of various regions in my country on August 18, 2012;

[0033] Figure 7 is the absorption index of each ionospheric observation station on July 19, 2012;

[0034] Figure 8 It is the average ionospheric absorption index of various regions in my country on July 19, 2012. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] The minimum echo frequency fmin parameter on the ionosphere vertical sounding ionogram can partially reflect the degree of absorption of the ionosphere to shortwave signals. Factors affecting the fmin parameter include: (1) the change of the recording system's amplification and sensitivity with frequency; (2) ionospheric absorption; and (3) noise level. The fmin parameter is insensitive to small changes in the ionosphere and is suitable for identifying the enhanced absorption of ionospheric shortwave signals caused by solar flares. If appropriate measures are taken, the fmin parameter can be used as an "indicator" of the degree of ionospheric absorption. Therefore, it is reasonable and feasible to use the ionospheric vertical sounding fmin data from different regions of my country to conduct quasi-real-time monitoring of sudden ionospheric disturbance events. It can be used as an effective technical means to monitor sudden ionospheric disturbance events and provide effective ionospheric environmental information for shortwave systems. Using the ratio of fmin to foF2 as an absorption index to describe the degree of absorption of ionospheric shortwave signals caused by solar flares is more reasonable and effective than the fmin value or TEC.

[0037] Example 1: In view of the shortcomings of the existing technology in identifying sudden ionospheric disturbance events, such as the inability of the fmin value to well reflect the degree of influence of ionospheric absorption on shortwave signals, the possible misjudgment problem of using TEC data for detection, and the difficulty of engineering application of other monitoring methods, this embodiment discloses a method for identifying sudden ionospheric disturbance events based on ionospheric vertical detection data, such as Figure 1 As shown, the following steps are included:

[0038] Step 1: Collect and organize the fmin and foF2 data of each ionospheric observatory during the M5.0 historical solar flare eruptions that occurred during the daytime in my country. The daytime period refers to 07:00-19:00 Beijing time.

[0039] Step 1A: Based on the historical solar flare event set published by SWPC, select events with a solar flare magnitude of M5.0 or above and a solar flare start time between 07:00 and 19:00 Beijing time;

[0040] Step 1B collects fmin and foF2 data from each ionospheric observatory during the onset and end of the solar flare and performs data preprocessing, such as deleting invalid data and identifying full absorption. Due to equipment failure, ionospheric F layer diffusion, occasional E layer, etc., foF2 data may be unavailable in the ionogram. In this case, the monthly median value is used instead of the foF2 value. If both fmin and foF2 data are missing, the data set is discarded. When the fmin metric value is symbolized as "B", it indicates full absorption; in this case, fmin = 1 and foF2 = 1. The locations of the ionospheric observatories used are shown in the following table:

[0041]

[0042]

[0043] Step 2: Calculate the ratio of fmin to foF2 at each ionospheric observation station at the corresponding time, statistically analyze the distribution of fmin / foF2, and determine the different intensity levels of ionospheric absorption at each ionospheric observation station based on the distribution;

[0044] Step 2A, using the processed valid data, calculate the ratio of fmin to foF2 data at each ionospheric observation station at the corresponding time, absorption index IAi = fmin / foF2;

[0045] Step 2B: Take the fmin / foF2 of each ionospheric observation station as a whole data set and perform statistics on the distribution of fmin / foF2 to obtain the proportion of samples in different fmin / foF2 value intervals to the total samples; the statistical results are as follows: Figure 2 As shown in the figure, the proportion of samples with an absorption index greater than 0.5 is 18%, the proportion of samples with an absorption index greater than 0.65 is 8%, and the proportion of samples with an absorption index greater than 0.8 is 5%.

[0046] Step 2C, according to Figure 2 The distribution of medium fmin / foF2 determines the fmin / foF2 value ranges for weak, medium and strong levels of ionospheric absorption: weak: 0.5≤IAi<0.65; medium: 0.65≤IAi<0.8; strong: IAi≥0.8.

[0047] Step 3: Calculate the ionospheric absorption characterization index of the entire region based on the fmin / foF2 data of each ionospheric observation station, and determine the intensity level of the sudden ionospheric disturbance event:

[0048] Step 3A: Based on the ionospheric absorption degree judgment results of each ionospheric observation station, the conditions for reaching a sudden ionospheric disturbance event are determined: if more than one-third of the ionospheric observation stations experience shortwave absorption of weak or above level, it is considered that a sudden ionospheric disturbance event has occurred.

[0049] Step 3B, average the fmin / foF2 data that reach the weak absorption level to obtain an ionospheric absorption characterization index IA that characterizes the degree of regional ionospheric absorption:

[0050]

[0051] In the above formula, N is the number of ionospheric observation stations that have reached the weak absorption level;

[0052] Step 3C: Determine the value range of the average ionospheric absorption characterization index IA for different levels of sudden ionospheric disturbance events:

[0053] Red: 0.5≤IA<0.65; Orange: 0.65≤IA<0.8; Yellow: IA≥0.8.

[0054] To verify the effectiveness of this patent in identifying sudden ionospheric disturbance events, this example presents the occurrence of solar flares of magnitude M5.0 or greater, occurring between 07:00 and 19:00 Beijing Time, and sudden ionospheric disturbance events in my country from 2010 to 2014. Of the 49 solar flare events shown in the table below, 29 were confirmed as sudden ionospheric disturbance events using this method, accounting for 60% of the total. Of these, 18 were yellow, 7 were orange, and 4 were red. "--" in the table below indicates missing fmin and foF2 data during these events.

[0055]

[0056]

[0057] This example provides the ionospheric absorption conditions in various regions of my country during the M9.3 flare on August 4, 2011. Figure 3 The absorption index of each ionospheric observation station during this event is given. The solid circles in the figure represent strong, moderate, and weak ionospheric absorption, respectively, from dark to light. Figure 4The average ionospheric absorption index for August 4th is shown, with the dashed vertical lines indicating the start and end times of the solar flare. After the flare began, sudden increases in ionospheric absorption occurred across my country, with the average absorption index exceeding 0.9. This patented method identified the sudden ionospheric disturbance event caused by this solar flare.

[0058] This example provides the ionospheric absorption conditions in various regions of my country during the M5.5 flare on August 18, 2012. Figure 5 The absorption index of each ionospheric observation station during this event is given. The solid circles in the figure represent strong, moderate, and weak ionospheric disturbances, respectively, from dark to light. Figure 6 The average ionospheric absorption index for August 18th is shown, with the dashed vertical lines indicating the start and end times of the solar flare. Following this solar flare, ionospheric absorption increased across all regions of my country, with the average absorption index exceeding 0.5, reaching the yellow level of a sudden ionospheric disturbance event. This patented method identified the sudden ionospheric disturbance event caused by this solar flare.

[0059] This example provides the ionospheric absorption conditions in various regions of my country during the M7.7 flare on July 19, 2012. Figure 7 The absorption index of each ionospheric observation station during this event is given. The solid circles in the figure represent strong, moderate, and weak ionospheric disturbances, respectively, from dark to light. Figure 8 The average ionospheric absorption index for July 19th is shown, with the dashed vertical lines indicating the start and end times of the solar flare. Following this solar flare, ionospheric absorption increased across all regions of my country, with the average absorption index exceeding 0.8, reaching the red level of a sudden ionospheric disturbance event. This patented method identified the sudden ionospheric disturbance event caused by this solar flare.

[0060] This embodiment illustrates that the average absorption index calculated by the method of this patent can reflect the degree of ionospheric absorption caused by solar flares and can identify sudden ionospheric disturbance events of different levels.

Claims

1. A method for identifying sudden ionospheric disturbance events based on ionospheric vertical sounding data, characterized in that: The steps include: Step 1: Collect and organize the fmin and foF2 data of each ionospheric observatory during the M5.0 historical solar flare eruptions that occurred during the daytime in my country. The daytime period refers to 07:00-19:00 Beijing time. The step 1 is specifically as follows: Step 1A: Based on the historical solar flare event set published by SWPC, select events with a solar flare magnitude of M5.0 or above and a solar flare start time between 07:00 and 19:00 Beijing time; Step 1B: Collect fmin and foF2 data from each ionospheric observatory during the start and end of the solar flare, and preprocess the data as follows: if the foF2 data in the ionogram cannot be read, replace the foF2 value with the monthly median value; if both fmin and foF2 data are missing, discard the data set; when the fmin metric value is symbol "B", it is full absorption, in which case fmin = 1 and foF2 = 1; Step 2: Calculate the ratio of fmin to foF2 at each ionospheric observation station at the corresponding time, statistically analyze the distribution of fmin / foF2, and determine the different intensity levels of ionospheric absorption at each ionospheric observation station based on the distribution; The step 2 is specifically as follows: Step 2A, calculate the ratio of fmin to foF2 data at each ionospheric observation station at the corresponding time, absorption index IAi = fmin / foF2; Step 2B, taking the fmin / foF2 of each ionospheric observation station as a whole data set, statistically analyzing the distribution of fmin / foF2, and obtaining the proportion of samples in different fmin / foF2 value intervals to the total samples; Step 2C, determine the fmin / foF2 value ranges for weak, moderate, and strong ionospheric absorption based on the distribution of fmin / foF2: weak: 0.5≤IAi<0.65; moderate: 0.65≤IAi<0.8; strong: IAi≥0.8; Step 3: Calculate the ionospheric absorption characterization index of the entire region based on the fmin / foF2 data of each ionospheric observation station, and determine the intensity level of the sudden ionospheric disturbance event; The step 3 is specifically as follows: Step 3A: Based on the ionospheric absorption degree judgment results of each ionospheric observation station, the conditions for reaching a sudden ionospheric disturbance event are determined: if more than one-third of the ionospheric observation stations experience shortwave absorption of weak or above level, it is considered that a sudden ionospheric disturbance event has occurred. Step 3B, average the fmin / foF2 data that reach the weak absorption level to obtain an ionospheric absorption characterization index IA that characterizes the degree of regional ionospheric absorption: In the above formula, N is the number of ionospheric observation stations that have reached the weak absorption level; Step 3C: Determine the value range of the ionospheric absorption characterization index IA for different levels of sudden ionospheric disturbance events: Red: 0.5≤IA<0.65; Orange: 0.65≤IA<0.8; Yellow: IA≥0.8.

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