CN111369034B - Long-term change analysis method for total electron content of ionized layer - Google Patents
Long-term change analysis method for total electron content of ionized layer Download PDFInfo
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Abstract
The invention relates to a long-term change analysis method of total electron content of an ionized layer, which comprises the steps of firstly considering the influence of solar activity, geomagnetic activity and neutral atmospheric components, establishing a model of the total electron content of the ionized layer changing along with time on the basis, then establishing an equation set by utilizing a long-term observation result of the total electron content of the ionized layer obtained by a global observation system, and calculating a model coefficient; and further utilizing a long-term ionospheric total electron content observed value to calculate the correlation between the model value and the observed value, and taking the correlation as an evaluation standard of the model precision. And respectively carrying out model correlation analysis on the long-term observed values of the total electron content of the multi-source ionized layer, and judging the action weight of each influence factor on the long-term change of the total electron content of the ionized layer. And respectively carrying out the analysis on different regions of the world, and judging the difference of the total electron content of the ionized layer of each region along with the change of time. The method can effectively analyze the long-term change of the total electron content of the global ionized layer.
Description
Technical Field
The invention belongs to the field of ionized layers, and particularly relates to a method for analyzing long-term change of total electron content of an ionized layer.
Background
The ionosphere is a high-rise atmosphere located 60km to 1000km above earth and is an important space strategic resource. The ionosphere is filled with a large number of charged particles and free electrons, has certain influence on radio waves penetrating through the earth atmosphere, and is one of important sources of satellite navigation signal ranging errors in the atmosphere. The total electron content of the ionosphere is an important physical quantity reflecting the activity and the state of the ionosphere, and is influenced by solar activity and a space magnetic field, so that strong disturbance can occur during solar storms and geomagnetic storms. The total electron content of the ionized layer can be obtained by inversion of satellite navigation signals through the ionized layer through double-frequency observed quantity, in order to describe the space-time distribution characteristics of the total electron content of the ionized layer more effectively, global satellite navigation service (IGS) ionized layer working groups invert the global distribution of the total electron content of the ionized layer by utilizing the all-day observed quantity of a plurality of GNSS observation stations of a global foundation, and the formed product provides effective technical support for researching and analyzing the space-time change trend of the total electron content of the ionized layer. Although much research work has been carried out to date on the short-term variation characteristics of the total electron content of the ionosphere, its long-term variation trend and impact remain the focus of attention of those in the relevant field. The long-term change characteristics and trends of the total electron content of the ionosphere are deeply understood, and further analysis of the influence of the lower atmosphere and human activities on the ionosphere is possible. Meanwhile, the long-term change rule of the total electron content of the ionosphere is mastered, so that the influence of a space weather event on the ionosphere and related activities of human beings can be known more clearly, and potential hazards such as ionosphere navigation error abnormity, navigation integrity risk and space signal propagation distortion caused by space weather can be effectively forecasted and prevented. Therefore, analyzing and mastering the long-term change characteristics of the total electron content of the ionized layer is a key technical problem to be solved urgently in the related field, and is one of the difficulties to be overcome by researchers in the related field.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method fully considers the influence of solar activity, geomagnetic activity and neutral atmospheric components on the change of the total electron content of the ionized layer, and establishes a long-term trend model of the change of the total electron content of the ionized layer along with time. Further, the accuracy of the model is analyzed by utilizing the correlation between the calculated value of the model and the observed value of the total electron content of the actual ionized layer, and the weight of the influence of solar activity, geomagnetic activity and neutral atmospheric components on the change of the total electron content of the ionized layer is deduced through the correlation analysis between the observed value of the total electron content of the actual ionized layer and the calculated value of the model; meanwhile, the activity conditions of different regions of the world are analyzed to master the difference of long-term change of the total electron content of the ionosphere in different regions.
The technical scheme adopted by the invention is as follows: a method for analyzing long-term change of total electron content of an ionized layer comprises the following concrete implementation steps:
step (1), considering the influence of solar activity, geomagnetic activity and neutral atmosphere components, and establishing a model of the change of the total electron content of the ionized layer along with time. Wherein, the solar activity is described by a solar activity index F10.7, the geomagnetic activity is described by a geomagnetic activity index Ap, the geomagnetic disturbance is described by a geomagnetic disturbance index AE, and the neutral atmospheric composition change is described by the proportion of oxygen atoms and nitrogen. The model of the change of total electron content TEC of the ionized layer along with the time t is described as follows:
wherein, γiI-1, 2, …,12 and fjJ is 1,2,3,4 is a correlation coefficient. Ap represents geomagnetic index, F10.7 represents solar activity index, AE represents polar region electric current disturbance, alphaO/NOxygen to nitrogen ratio, TEC, of neutral atmosphere0Is the background ionospheric total electron content, which does not change over time; d is the number of days and has a value from 1 to 365 (non-leap years) or 366 (leap years).
And (2) establishing an equation set by utilizing a long-term observation result of the total electron content of the ionized layer obtained by the global observation system, solving undetermined coefficients in the model, and further solving the model. The undetermined coefficient in the model is solved by a least square method, and the undetermined coefficient is specifically as follows:
and (3) calculating the correlation between the long-term observation result of the global observation system and the model output value by using the long-term observation result of the global observation system, and taking the correlation as an evaluation standard of the model accuracy, namely, the higher the correlation is, the higher the model accuracy is, and the closer the model accuracy is to the actual situation. The correlation calculation method comprises the following steps:
wherein
Is the average of the observed values and is,
is the calculated value of the model according to step 1, R represents the correlation coefficient, y is the observed value, i is 1, …, and n is the number of observed values.
Step (4), model correlation calculation is carried out by respectively utilizing different types of long-term observation results, and the weight of the influence of solar activity, geomagnetic activity and neutral atmospheric components on the model precision is analyzed; the actual observed values of the global total electron content of the ionosphere of different types comprise a global ground GNSS observation network, an ionosphere total electron content global distribution diagram product provided by an international ionosphere service (IGS) and the total electron content of the ionosphere obtained by a satellite-based observation ionosphere electron density profile. The influence weight of the solar activity, the geomagnetic activity and the neutral atmospheric composition on the long-term change of the total electron content of the ionized layer is represented by the corresponding correlation magnitude.
And (5) respectively carrying out model correlation calculation aiming at different regions in the world, and analyzing the difference of the total electron content of the ionosphere in each region along with the change of time. Wherein, the selection basis of different global areas is to select low latitude, middle latitude and high latitude areas according to the latitude; north america, europe and africa, and asia and australian regions by longitude; differences between southern and northern hemispheres were analyzed as hemispheres.
And (6) comprehensively analyzing results, and optimizing the model according to the weight of different influence factors on the model and the difference characteristics of different regions.
Compared with the prior art, the invention has the advantages that:
(1) compared with the traditional calculation method, the method disclosed by the invention (shown in figure 1) has the advantages that the long-term time change characteristics of the total electron content of the ionized layer can be more accurately analyzed, and the influence of solar activity, geomagnetic activity and neutral atmospheric components on the change of the total electron content of the ionized layer is clarified. As shown in fig. 2.
(2) Compared with the traditional method, the ionospheric total electron content long-term change model has higher correlation with the actual observed value, which shows that the method has higher precision and accuracy when describing the ionospheric total electron content long-term change, and the effect is shown in fig. 3.
(3) Compared with the traditional calculation method, the method can effectively research the difference of the influence of the AE index on the long-term change characteristics of the total electron content of the ionosphere in different regions of the world, and the effect is shown in figure 4.
Drawings
FIG. 1 is a flow chart of a method implementation of the present invention;
FIG. 2 is a graph showing the effect of solar activity, geomagnetic activity and neutral atmospheric composition on the change of total electron content in the ionosphere obtained by the method;
FIG. 3 is a correlation coefficient between an ionospheric actual observation and a model fitting obtained by the conventional method and the present method;
fig. 4 is the difference of correlation coefficient between the actual observed value of ionosphere in different regions of the world and the fitted value of the model, both with and without taking AE index into account, wherein fig. 4(a) is the result calculated by using the global ionosphere total electron content distribution diagram product provided by the WHU analysis center, fig. 4(b) is the result calculated by using the global ionosphere total electron content distribution diagram product provided by the COD analysis center, and fig. 4(c) is the result calculated by using the global ionosphere total electron content distribution diagram product provided by the UPC analysis center.
Detailed Description
The invention will be described in detail below with reference to the accompanying drawings and specific embodiments, which are only intended to facilitate the understanding of the invention and are not intended to limit the invention.
The invention provides a method for analyzing the long-term change of the total electron content of an ionized layer, which fully considers the influence of solar activity, geomagnetic activity and neutral atmospheric components on the change of the total electron content of the ionized layer, establishes a long-term trend model of the change of the total electron content of the ionized layer along with time, and can better describe the long-term change trend of the total electron content of the ionized layer and the difference of the long-term change characteristics of the total electron content of the ionized layer in different regions of the world.
As shown in fig. 1, the method of the invention comprises the following steps:
step 1, considering the influence of solar activity, geomagnetic activity and neutral atmosphere components, and establishing a model of the change of the total electron content of the ionized layer along with time. Wherein, the solar activity is described by a solar activity index F10.7, the geomagnetic activity is described by a geomagnetic activity index Ap, the geomagnetic disturbance is described by a geomagnetic disturbance index AE, and the neutral atmospheric composition change is described by the proportion of oxygen atoms and nitrogen. The model of the change of total electron content TEC of the ionized layer along with the time t is described as follows:
wherein, γiI-1, 2, …,12 and fjJ is 1,2,3,4 is a correlation coefficient. Ap represents geomagnetic index, F10.7 represents solar activity index, AE represents polar region electric current disturbance, alphaO/NOxygen to nitrogen ratio, TEC, of neutral atmosphere0Is the background ionospheric total electron content, which does not change over time; d is the number of days and has a value from 1 to 365 (non-leap years) or 366 (leap years).
And 2, establishing an equation set by utilizing the long-term observation result of the total electron content of the ionized layer obtained by the global observation system, solving undetermined coefficients in the model, and further solving the model. And solving the undetermined coefficient in the model by adopting a least square method.
And 3, calculating the correlation between the long-term observation result of the global observation system and the model output value by using the long-term observation result of the global observation system as an evaluation standard of the model accuracy, wherein the higher the correlation is, the higher the model accuracy is, and the closer the model accuracy is to the actual situation. The correlation calculation method comprises the following steps:
wherein
Is the average of the observed values and is,
is the calculated value of the model according to step 1, R represents the correlation coefficient, y is the observed value, i is 1, …, and n is the number of observed values.
Step 4, model correlation calculation is carried out by respectively utilizing different types of long-term observation results, and the weight of the influence of solar activity, geomagnetic activity and neutral atmospheric components on the model precision is analyzed; here, the global distribution map product of the total electron content of the ionosphere provided by the global ground-based GNSS observation network and the international ionosphere service (IGS) is used to calculate the observed value of the actual total electron content of the ionosphere. The influence weight of the solar activity, the geomagnetic activity and the neutral atmospheric composition on the long-term change of the total electron content of the ionized layer is represented by the corresponding correlation magnitude.
And 5, respectively carrying out model correlation calculation aiming at different regions of the world, and analyzing the difference of the total electron content of the ionosphere in each region along with the change of time. Wherein, the selection basis of different global areas is to select low latitude, middle latitude and high latitude areas according to the latitude; north america, europe and africa, and asia and australian regions by longitude; differences between southern and northern hemispheres were analyzed as hemispheres.
And 6, comprehensively analyzing results, and optimizing the model according to the weight of different influence factors on the model and the difference characteristics of different regions.
The invention provides a method for analyzing the long-term change of the total electron content of an ionized layer, which is shown in figure 2. The method describes how the total electron content of the ionized layer changes under the influence of solar activity, geomagnetic activity and neutral atmospheric composition change in detail, mainly reflects the long-term characteristics of the total electron content change of the ionized layer, and reveals the difference of the long-term change of the total electron content of the ionized layer in different regions of the world.
From the simulation results, as shown in fig. 3 and fig. 4, the time distribution diagrams of S4 (line 1), ROTI (line 2) and the irregular body drift velocity (line 3) during the years of the australian WEIP (left side) and DWNI (right side) observation stations 2011-2015 are calculated in fig. 3, and it can be seen that the irregular body drift velocity has similar distribution characteristics with the amplitude flicker index S4 and the ROTI index, and the drift velocity generally accelerates as the S4 and the ROTI value increase. In fig. 4, (a) the graph analyzes the correlation between the irregular body drift velocity and the ROTI, the elevation angle and the S4, and it is known that the graph easily finds a larger drift velocity and a higher S4 at a low elevation angle, and (b) the graph analyzes the correlation between the irregular body drift velocity and the ROTI, the signal-to-noise ratio α and the S4, and it is known that the irregular body drift velocity is larger and more easily causes strong ionospheric amplitude flicker at a lower signal-to-noise ratio, which is consistent with the actual situation.
Fig. 2 is a correlation analysis of total ionospheric electron content calculated by using the model of the present invention and an actual observed value, which is obtained by resolving data provided by a global ground-based GNSS observation network provided by international satellite navigation service (IGS) in the calculation process, and the contributions of two influencing factors, AE and O/N2, to a correlation coefficient are analyzed respectively. There may be some contribution to the improvement of the correlation coefficient from both AE and O/N2, and O/N2 is larger than AE.
FIG. 3 is a graph of the difference in correlation coefficient between the total ionospheric electron content calculated using the model of the present invention and the results calculated from the global ionospheric total electron content profile, both without consideration of and with consideration of the AE index modeling, respectively. The result shows that the AE index can well improve the correlation coefficient of the high latitude area, shows that the AE index mainly influences the change of the total electron content of the ionosphere of the high latitude area, and has more obvious influence on the AE index in low-year solar activity.
FIG. 4 is a correlation analysis between the total electron content of the ionosphere calculated using the model of the present invention and the results calculated from the global ionosphere total electron content profile, and compared to conventional methods. In the calculation process, products of global ionospheric total electron content distribution diagrams provided by three IGS analysis centers of WHU (a diagram), COD (b diagram) and UPC (c diagram) are respectively analyzed, and the results show that the models of the invention all obtain better correlation coefficients, which shows the superiority of the invention compared with the traditional method.
In summary, the invention provides an analysis method for the long-term change of the total electron content of the ionized layer, which is helpful for deeply understanding the influence of the total electron content of the ionized layer by the change of solar activity, geomagnetic activity and neutral atmospheric composition, simultaneously discloses the difference of the long-term change of the total electron content of the ionized layer in different regions of the world, provides a high-precision long-term change model of the total electron content of the ionized layer, and provides effective technical support for further mastering the long-term change rule of the total electron content of the ionized layer, analyzing the influence of low-level atmosphere and human activity on the long-term change of the ionized layer and predicting and preventing the influence of space weather events on the ionized layer.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. A method for analyzing long-term change of total electron content of an ionized layer is characterized by comprising the following steps:
step A, considering the influence of solar activity, geomagnetic activity and neutral atmospheric components, and establishing a model of the change of the total electron content of an ionized layer along with time; the model of the change of the total electron content TEC of the ionized layer along with the time t is described as follows:
wherein, gamma isiI-1, 2, …,12 and fjJ is 1,2,3,4 is a correlation coefficient, Ap represents a geomagnetic index, F10.7 represents a solar activity index, AE represents a polar region electric current disturbance, αO/NOxygen to nitrogen ratio, TEC, of neutral atmosphere0Is the background ionospheric total electron content, which does not change over time; d is the number of days, and the value is from 1 to 365 in the case of non-leap years, and from 1 to 366 in the case of leap years;
b, establishing an equation set by utilizing an ionized layer total electron content long-term observation result obtained by a global observation system, and solving undetermined coefficients in the model so as to solve the model;
step C, calculating the correlation between the long-term observation result of the global observation system and the output value of the model, and taking the correlation as the evaluation standard of the model precision, wherein the higher the correlation is, the higher the model precision is, and the closer the model precision is to the actual condition; the correlation calculation method of the actual observed quantity of the total electron content of the ionized layer and the model calculation value comprises the following steps:
wherein
Is the average of the observed values and is,
a calculated value of the model in step a, R represents a correlation coefficient, y is an observed value, i is 1, …, and n is the number of observed values;
d, respectively utilizing different types of long-term observation results to calculate the correlation of the model, and analyzing the weight of the influence of solar activity, geomagnetic activity and neutral atmospheric components on the precision of the model; the sources of the actual observed values of the total electron content of the global ionized layer of different types comprise a global ground GNSS observation network, a global distribution diagram product of the total electron content of the ionized layer provided by the international ionized layer service and the total electron content of the ionized layer obtained by a star-based observation ionized layer electron density profile;
step E, model correlation calculation is carried out on different regions of the world respectively, and the difference of the total electron content of the ionized layer of each region along with the change of time is analyzed;
and F, comprehensively analyzing results, and optimizing the model according to the weight of the model and the difference characteristics of different regions by different influence factors.
2. The method for analyzing the long-term change of the total electron content of the ionized layer according to claim 1, wherein: and in the step B, solving undetermined coefficients in the model by adopting a least square method.
3. The method for analyzing the long-term change of the total electron content of the ionized layer according to claim 1, wherein: in the step D, the influence weight of the solar activity, the geomagnetic activity and the neutral atmospheric composition on the long-term change of the total electron content of the ionized layer is represented by the corresponding correlation size.
4. The method for analyzing the long-term change of the total electron content of the ionized layer according to claim 1, wherein: in the step E, the selection basis of different global areas is to select low latitude, medium latitude and high latitude areas according to the latitude; north america, europe and africa, and asia and australian regions by longitude; differences between southern and northern hemispheres were analyzed as hemispheres.
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| CN106934113A (en) * | 2017-02-21 | 2017-07-07 | 东南大学 | Suitable for the modeling method of the improved polynomial of the vertical total electron content modeling in region ionosphere |
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| CN110441795A (en) * | 2019-08-13 | 2019-11-12 | 苏州时空复弦网络科技有限公司 | A kind of regional ionosphere VTEC Precise modeling based on space-time structure information |
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