KR20150075910A - Method for detecting solar radio burst - Google Patents

Abstract

Disclosed is a method for detecting a solar radio burst which may automatically detect the occurrence of a solar radio burst by using a spectrum characteristic according to a mode of the solar radio burst. The method for detecting a solar radio burst includes: a step of removing noise in an obtained solar radio spectrum; and a step of transforming a space by radon-transforming the solar radio spectrum with the noise element removed and detecting the solar radio burst according to a radon transformation value calculated in the transformed space. According to the method for detecting the solar radio burst, the present invention may reduce worker fatigue, detection errors or detection omission by the worker, and other problems by automatically detecting the unique spectrum that the solar radio burst represents.

Description

METHOD FOR DETECTING SOLAR RADIO BURST [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for detecting a solar-radio-wave explosion, and more particularly, to a method for detecting a solar-radio-blast explosion that can detect occurrence of a solar-wave explosion automatically using spectral characteristics according to the type of solar-

The explosion of solar radiation has a profound effect on the civilization life on Earth, such as geomagnetic disturbance, radio disturbance.

Type III of the solar explosion type explosion lasts for 1 to 3 seconds, and the propagation speed is fast enough to be more than 10% of the speed of light. Form III may also appear as a group, the duration of the whole group being from 1 to 5 minutes and the frequency range from 10 kHz to 1 GHz. Type III appears after the flare explosion and the high energy electrons associated with the explosion lead to plasma emission as it passes through the solar atmosphere. Since high-density regions move quickly to lower regions, the radio wave explosion also moves quickly from high frequencies to low frequencies.

Type II of the solar propagation explosion occurs in shock waves related to coronal mass ejection. Type II is considerably slower than Type III and lasts from minutes to tens of minutes, often with second harmonics. The plasma emission is also propagated and the fundamental mode starts at approximately 150 MHz and ends at several tens of MHz. The propagation velocity is calculated to be less than 2000 km / sec, and the frequency is significantly lower than that of Form III.

Such solar explosions should be monitored at all times, as they have a profound effect on Earth's civilization life, such as geomagnetic disturbances, radio disturbances, GPS signal anomalies, satellite position changes, pipeline corrosion, extreme route radioactivity exposure, However, continuous monitoring by a person for a solar electron explosion may cause operator fatigue, thereby causing problems such as data loss.

Accordingly, there is a need in the art for a technique capable of automatically monitoring and detecting sunlight explosion.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of detecting a solar-radio-wave explosion that can automatically detect occurrence of a solar-wave explosion automatically using spectral characteristics according to the type of a solar-wave explosion.

According to an aspect of the present invention,

Removing a noise component from the acquired solar propagation spectrum; And

Detecting a sun propagation explosion in accordance with the radon conversion value calculated in the converted space by radon conversion of the sun propagation spectrum from which the noise component is removed,

And a method for detecting a solar radio wave explosion.

An embodiment of the present invention may further comprise setting a frequency range for detecting the solar propagation spectrum and the solar radio explosion before the step of removing the noise component.

In one embodiment of the present invention, the step of removing the noise component comprises the steps of: subtracting a previously prepared high frequency noise interference (RFI) sample spectrum in the acquired solar propagation spectrum; And removing the spike component in the subtracted data of the high frequency noise interference (RFI) sample spectrum.

In one embodiment of the present invention, the step of removing the spike component comprises filtering the data obtained by subtracting the high frequency noise interference (RFI) sample spectrum by applying a median filter having a wide window in the direction of the time axis .

In one embodiment of the present invention, the step of detecting the solar-wave explosion includes a step of performing Radon transformation in a frequency-time space showing the solar-radio spectrum from which the noise component is removed, ; Calculating a radon conversion value in the transformed space; And detecting a time at which a radon conversion value larger than a preset threshold value among the plurality of radon conversion values calculated in the calculating step is calculated as the time at which the type III sunlight explosion occurred.

In one embodiment of the present invention, the step of detecting the solar propagation explosion includes the steps of: converting a frequency-time space representing the solar propagation spectrum from which the noise component is removed into a frequency inverse-time space; Performing Radon transformation on the transformed inverse-time space in the step of transforming into the frequency inverse number-time space to transform the transformed space into a space expressed by a slice and a slope; Calculating a radon conversion value in the transformed space at the step of transforming into a space represented by the slice and the slope; And a time corresponding to a highest frequency and a lowest frequency in a region having a radon conversion value larger than a preset threshold value among the radon conversion values calculated in the calculating step, And detecting at a time when the time has ended.

In one embodiment of the present invention, the step of performing the Radon transform to convert the slice into a space represented by the slope and the slope may include: converting the frequency spectrum of the sun in the frequency inverse time space before the radon conversion And may include a thinning step.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to reduce the fatigue of the operator by automatically detecting a specific spectrum represented by the solar-wave explosion, and there is an excellent effect of solving the problem of detection error or missing detection by the operator.

1 is a flow chart of a method for detecting a solar wave explosion according to an embodiment of the present invention.
Fig. 2 is a flowchart showing in detail the step of setting the solar propagation data range of the solar propagation explosion detection method according to an embodiment of the present invention.
3 is a flow chart showing in detail the step of removing noise components in the method of detecting sunlight explosion according to an embodiment of the present invention.
4 is a graph showing an example of the RFI sample spectrum used in the step of removing the noise component of the method of detecting a solar radio explosion according to an embodiment of the present invention.
FIG. 5 is a spectrogram showing a sun-free spectrum in which noises are removed in the step of removing a noise component in the method of detecting a solar-radio-wave explosion according to an embodiment of the present invention.
FIG. 6 is a spectrogram showing the result of removing a spike component by applying a median filter to the solar propagation spectrum shown in FIG. 5. FIG.
7 is a flowchart showing in detail the type III sunlight explosion detection step of the method of detecting sunlight explosion according to an embodiment of the present invention.
8 is a graph showing an example of a radon conversion value and a threshold value calculated in the type III sunlight explosion detection step of the method of detecting a solar radio wave explosion according to an embodiment of the present invention.
9 is a flowchart showing in detail the type II sunlight explosion detection step of the method of detecting sunlight explosion according to an embodiment of the present invention.
Fig. 10A shows a spectrum of frequency-time space used in the type II solar propagation explosion detection step of the method of detecting solar-wave explosion according to an embodiment of the present invention, Fig. 10B shows the spectrum of Fig. FIG. 10C shows a result of performing thinning on the spectrum of FIG. 10B. FIG.
11 is a graph showing the distribution of radon transformed values as a function of the end time and the duration in the type II solar propagation explosion detection step of the method of detecting sunlight explosion according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. In addition, in describing the present invention, the defined terms are defined in consideration of the functions of the present invention, and they may be changed depending on the intention or custom of the technician working in the field, so that the technical components of the present invention are limited It will not be understood as meaning.

1 is a flow chart of a method for detecting a solar wave explosion according to an embodiment of the present invention.

1, a method of detecting a solar radio wave explosion according to an embodiment of the present invention includes a step (S12) of removing a noise component from a acquired solar propagation spectrum, a step (S12) of removing a noise component from the solar propagation spectrum, (S13, S14) of converting a space and detecting a solar propagation explosion according to the radon conversion value calculated in the converted space.

In addition, the method of detecting a solar radio wave explosion according to an embodiment of the present invention includes the step S11 of setting a frequency range for detecting the solar radio spectrum explosion and the solar radio spectrum explosion before the step S12 of removing the noise component, As shown in FIG.

The method of detecting sunlight explosion according to an embodiment of the present invention can be started from step S11 of setting a solar propagation data range for setting a sunlight propagation spectrum acquisition time and a frequency range for detecting sunlight explosion.

Fig. 2 is a flow chart showing in detail the step of setting the solar propagation data range of the solar radio wave explosion detection method of the present invention.

As shown in Fig. 2, step S11 of setting the solar propagation data range of the solar propagation explosion detection method includes a step S111 of setting the solar propagation spectrum acquisition time and a step of setting the acquisition frequency of the solar propagation spectrum (S111).

In step S111 of setting the solar radio spectrum acquisition time, a time for acquiring the solar propagation data is set in consideration of the sunrise and sunset time of the observation site provided with the radio telescope for acquiring the solar radio spectrum and the natural environment of the observation place .

A radio-frequency interference (hereinafter referred to as RFI), which is a noise component according to a location (for example, sky and mountain) of a radio telescope, And background power are different. Since this phenomenon can affect the data processing, it is desirable to obtain the RFI and background power for the acquired solar propagation when the sun is completely above the mountain. To do this, it is necessary to accurately grasp the sunrise and sunset times in the area where the radio telescope is located (in Korea, Icheon or Jeju). The inventor of the present invention creates and uses a program to read and produce a file in the form of a file provided by the astronomical research institute in Korea on a monthly basis.

Normally, there is an acid around the observation area where the radio telescope is present, so correction is necessary because the sun will not rise or fall precisely at this time. This is obtained by comparing the background value of the measurement data with the point at which the value changes before and after sunrise and sunset, and the sunrise and sunset times.

The step S112 of setting the spectrum acquisition frequency is a step of setting the data processing frequency in consideration of the frequency range in which the solar propagation explosion occurs.

For example, in consideration of the fact that the solar propagation explosion occurs mainly at a low frequency, the solar propagation measurement frequency itself is 30 MHz to 2.5 GHz, but can be determined as a frequency range for data processing in the range of 30 MHz to 170 MHz. In fact, data from 2011 and 2012 Icheon show very little radio wave explosion above 170MHz.

Subsequently, a step S12 of removing the noise component from the solar propagation data acquired in accordance with the time and frequency range determined in step S11 is performed.

3 is a flow chart showing in detail the step of removing noise components from the solar propagation data of the solar radio wave explosion detection method of the present invention.

3, removing the noise component from the solar propagation data of the solar radio wave explosion detection method of the present invention (S12) includes the steps of subtracting the previously prepared RFI sample spectrum from the acquired solar propagation data S121) and removing the spike component in the data from which the RFI sample spectrum is subtracted (S122).

The solar propagation data, or spectrum, obtained through the radio telescope contains a large number of RFIs. In particular, the lower the frequency, the more RFI can be present. In addition, since the RFI varies with time, it is very difficult to properly remove the RFI from the measured data. One of the most desirable RFI removal techniques is to use data from similar time periods that are close to the data acquisition date but without the sunburst explosion. It is not suitable because the operator has to intervene and judge every moment to choose the one without explosion.

The inventors of the present invention will use the measured 24 hour average value of a specific day without explosion as a kind of sample and store it in our eyes. To this end, the inventors of the present invention have developed a program for creating a sample spectrum and storing it as a file. FIG. 4 shows a sample spectrum of spiked components having a narrow width created by averaging RFI spectra from 14:00 to 16:00 on March 14, 2012. FIG.

In step S121 of subtracting the previously prepared RFI sample spectrum from the acquired solar propagation data, this RFI sample spectrum may be subtracted from the acquired data to remove the RFI component. In particular, the data applied to the computation is logarithmic, which is equivalent to performing this subtraction, and in this context a flat fielding process may be performed to compensate for the different gain of each spectral channel.

5 is a spectrogram showing the result after subtracting the sample spectrum from the spectrum of the solar propagation explosion at about 08:00 on July 7, 2012 (KST), as described above. The solar propagation explosion shown in Fig. 5 is data that is useful for verifying the solar radio explosion detection method according to the present invention, in which Form III and Form II appear at the same time. In particular, in FIG. 5, the fundamental mode and the second harmonics coexist in Form II.

Since the RFI may not be perfectly removed even if the process of step S121 is performed, the RFI may remove the spike component having a narrow frequency width by using the fact that the frequency width is narrow in step S122.

In an embodiment of the present invention, the step of removing the spike component (S122) may be implemented by applying a median filter in the time axis direction in the solar explosion spectrum. Since the RFI fluctuates very slowly but fluctuates with time, it is possible to efficiently remove the RFI by performing filtering by setting the filtering window of the median filter to be wide (for example, 2000 seconds or more). The result of removing the RFI by applying the median filter is shown in Fig.

As shown in FIG. 6, it can be seen from FIG. 5 that the RFI (spike component) that has passed through the narrow frequency band for a long time has been removed through median filtering.

When the data range setting step (S11) and the noise removing step (S12) are ended as described above, steps (S13 and S14) for detecting substantial solar propagation explosion are performed. The solar-electron explosion detecting step (S13, S14) is a step of converting a space by radon-converting the solar-radio spectrum from which the noise component is removed, and detecting a solar-radio-wave explosion in accordance with the radon- There is some difference depending on the type of explosion.

First, a step S13 of detecting a solar propagation explosion of type III will be described.

7 is a flowchart showing in detail a type III sunlight explosion detection step according to an embodiment of the present invention.

As shown in Fig. 7, in the type III sunlight explosion detection step S13, radon conversion is performed in a frequency-time space representing a solar propagation spectrum to transform the space into a space expressed by a slice and a slope (S132) of determining a time point at which the maximum frequency appears in the transformed space as an x-axis intercept and calculating a radon transform value for a plurality of slopes, and a step (S132) of calculating a radon transform value (S133) of detecting the time at which the larger radon conversion value is calculated as the time when the type III sunlight explosion occurred.

The type III solar propagation explosion appears as a nearly vertical line in the frequency-time plane. Propagation speeds are propagated to the upper atmosphere at a rate of 10% or more of the speed of light even at low speeds. Since the solar propagation explosion of type III appears almost as a vertical line in the frequency-time plane, it can be detected by applying a radon conversion algorithm recognizing a straight line pattern in a certain space. In other words, the type III solar propagation explosion generates a straight line as a function of the frequency axis intercept and slope by applying the radon transformation algorithm in frequency-time space, and this is the case where the explosion phenomenon is most correlated.

The radon transformation performed in the step S131 of performing the Radon transformation in the frequency-time space representing the solar propagation spectrum and transforming into the space expressed by the slice and the tilt can be expressed as Equation 1 below .

,

가 된다. 직선 방향으로 라돈 변환 수행한 경우 라돈 변환값 R이 최대가 된다. In Equation (1), t and f mean time and frequency, and s is a length element on a straight line in a two-dimensional plane made of time-frequency. If you describe this straight line as a slice and a slope,

,

. When radon conversion is performed in the linear direction, the radon conversion value R becomes maximum.

In step S132, an x-axis intercept is defined as a point at which the maximum frequency appears. In this case, the x-axis intercept can be regarded as the start of the radio wave explosion. Naturally, if the integration of Equation 1 is performed in the direction in which the radio wave explosion appears, the radon conversion value R will be the maximum value.

The equation of the fitting curve in the spectrum from 30 MHz to 170 MHz at 4 second intervals can be used to generate the intercept and tilt as shown below and in Equation 2, assuming that the event starts at 170 MHz and the event ends at 30 MHz.

In step S132, a radon conversion value R is obtained for several slopes with respect to a given x-axis intercept, and a maximum value is obtained from the two-dimensional plane. However, as described above, the type III solar radiation explosion ends within a few seconds, so the range of the tilt is very limited. It is not a problem to draw the radon conversion value R as a function of the x-axis intercept, that is, the start time of the radio wave explosion.

In step S133, when the radon conversion value is larger than the predetermined threshold, it can be considered that the solar propagation explosion of type III occurs. FIG. 8 is a graph showing an example of detecting a type III solar explosion explosion according to a selected threshold value. If you set the threshold to 20, one type III solar-blast explosion is detected between 23 and 08-09 minutes. Between 10 and 12 minutes, there is also a high-value zone, which is due to solar-blast explosion of type II. Because the solar electron explosion does not appear as a straight line, the value is smaller than the event between 08-09 minutes, so that Form III and Form II can be distinguished. The threshold value can be appropriately preset in view of the result of many solar propagation explosions that occurred in the past.

Next, a step S14 of detecting the solar propagation explosion of type II will be described.

FIG. 9 is a flow chart showing in detail the type II solar radio wave explosion detection step according to an embodiment of the present invention.

9, the type II sunlight explosion detection step S14 includes a step S141 of converting the frequency-time space representing the solar propagation spectrum into the frequency inverse-time space, A step S142 of converting Radon transformation into a space represented by a slice and a slope by performing a Radon transformation on the radon transformation value S143, calculating a radon transformation value R using a function of a start time and a duration, The time corresponding to the highest frequency and the time corresponding to the lowest frequency in the region having the radon conversion value larger than the predetermined threshold value among the radon conversion values detected at the time when the type II solar radio wave explosion occurred and the time when the explosion occurred Step S144.

Type II solar wave explosion occurs at high frequencies and has the characteristic of moving to lower frequencies over time. The duration is approximately 3 to 30 minutes.

When the frequency-time space is converted to the reciprocal-time space of frequency, the type II solar wave explosion is known to appear as a straight line, and the type II solar wave explosion is the inverse of the frequency- Can be detected through radon conversion.

Accordingly, the frequency-time space representing the solar propagation spectrum is converted into the frequency inverse-time space in step S141, and the radar transformation is performed in the inverse-time space converted in step S142, (Step S143).

Meanwhile, in step S143, a process of skeletonizing the spectrum expressed in the reciprocal-time space converted prior to the radon conversion may be performed taking into consideration the characteristics of the type II solar propagation explosion.

The type Ⅱ solar radio explosion has a long duration and frequency harmonics for a given frequency, so it is difficult to determine the start time and end time of the event. To solve this problem, thinning techniques can be applied. The thinning technique extracts only the skeletal structure of a shape having a dull structure, and various specific algorithms are known. 10A shows a spectrum of a frequency-time space for a typical type II solar wave explosion at 09:00 on July 31, 2012, and FIG. 10B shows a spectrum obtained by converting the spectrum of FIG. 10A into a frequency inverse-time space And FIG. 10C shows a result of thinning the spectrum of FIG. 10B. As shown in FIG. 10C, the thinning process shows that the key part of the event is well represented.

In step S143, the radon conversion value R is calculated using a function of the start time and the duration. The fitting curve used at this time is expressed by the following equation (3).

The above equation (3) is such that the frequency is inversely proportional to time, f = 170 MHz at t = ts, and f = 30 MHz when t = ts + ?. Using this equation (3), similarly to the above-described type III sunlight explosion detection process, the radon conversion value can be obtained as a function of the start time ts and the duration?.

In the step S144, the time corresponding to the highest frequency and the time corresponding to the lowest frequency in the region having the radon conversion value larger than the predetermined threshold value among the calculated radon conversion values are referred to as the time at which the type II sunlight explosion occurred, It can be detected at the end time.

11 shows the distribution of the radon conversion value as a function of the end time (= ts +?) And the duration? Instead of the start time. Referring to FIG. 11, the largest peak is found near the approximate duration of 540 seconds and the end time of 680 seconds. The example shown in Fig. 11 shows a satisfactory detection result through the above-described steps S141 to S144 when a relatively type II solar radio explosion is clearly identified.

As described above, according to the embodiment of the present invention, the specific spectrum indicated by the solar wave explosion is automatically detected, so that fatigue can be saved to the operator, and problems such as detection error and missing detection by the operator can be solved .

Although the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the scope of the present invention should not be limited to the embodiments described, but should be determined by the scope of the following claims and equivalents thereof.

Claims (7)

Removing a noise component from the acquired solar propagation spectrum; And
Detecting a sun propagation explosion in accordance with the radon conversion value calculated in the converted space by radon conversion of the sun propagation spectrum from which the noise component is removed,
And detecting the solar radiation explosion. The method according to claim 1,
Further comprising the step of setting a frequency range for detecting the solar radio spectrum acquisition time and the solar radio explosion prior to the step of removing the noise component. The method according to claim 1,
The step of removing the noise component includes:
Subtracting a prefabricated high frequency noise interference (RFI) sample spectrum from the acquired solar propagation spectrum; And
Removing the spike component in the subtracted data of the high frequency noise interference (RFI) sample spectrum. 4. The method of claim 3, wherein removing the spike component comprises:
Applying a median filter having a wide window in the time axis direction to the subtracted data of the high frequency noise interference (RFI) sample spectrum. The method according to claim 1,
The step of detecting the solar propagation explosion includes:
Performing a Radon transformation in a frequency-time space representing the solar propagation spectrum from which the noise component is removed to convert the space into a space expressed by a slice and a slope;
Calculating a radon conversion value in the transformed space; And
Detecting a time at which a radon conversion value larger than a predetermined threshold value among a plurality of radon conversion values calculated at the calculating step is calculated as a time at which a type III sunlight explosion occurs; Way. The method according to claim 1,
The step of detecting the solar propagation explosion includes:
Transforming the frequency-time space representing the solar propagation spectrum from which the noise component is removed into a frequency inverse-time space;
Performing Radon transformation on the transformed inverse-time space in the step of transforming into the frequency inverse number-time space to transform the transformed space into a space expressed by a slice and a slope;
Calculating a radon conversion value in the transformed space at the step of transforming into a space represented by the slice and the slope; And
The time corresponding to the highest frequency and the time corresponding to the lowest frequency in the region having the radon conversion value larger than the predetermined threshold value among the radon conversion values calculated in the calculating step are referred to as the time and And detecting the detected time at the terminated time. The method according to claim 6,
The step of performing the Radon transformation to transform the space into a space represented by the slice and slope may include thinning the solar propagation spectrum converted into the frequency inverse time space before the radon conversion Wherein the solar electron explosion detecting method comprises the steps of:

Images