| Es(Sporadic E)is a region where the electron density incident in the E layer of the ionosphere is enhanced relative to the background ionosphere environment.Since the critical frequency of Es can sometimes be compared to the critical frequency of the F-layer,and even much larger than the critical frequency of the F-layer,the appearance of the ionospheric Es has an important effect on the radio propagation.At the same time,the physical mechanism of ionospheric Es needs to be further studied and improved,so it is of great scientific significance for the study of ionospheric Es.The appearance of Es in the ionogram,especially the two-hop echo,has a great influence on the measurement and inversion of F-layer.Firstly,this paper verifies the performance of the iono Scaler,which is used in Wuhan Ionospheric Sounding System,this software can automatically measure the performance of Es parameters,and then proposed a method based on decision tree algorithm to automatically identify Es layer and its echoes on ionogram and further verify the effect of Es two-hop echo on iono Scaler’s automatic measurement of F-layer parameters.In addition,this paper statistically analyzes the daily variation and seasonal variation of Es in Pu’er City,Yunnan Province in 2015.The main work of this article is as follows:Firstly,introduced the various types of Es layer in detail,and verified the function of iono Scaler in measuring Es layer.iono Scaler software was used to automatically measure the Es parameters of the ionosphere in Pu’er,Yunnan in 2015.The automatic measurement results were compared with the artificial measurement data.The results show that 81.55% accuracy for differences between 0.5 MHz,66.97% accuracy for differences between 5 km,which meets the basic expectations.Secondly,this paper proposes an algorithm that can automatically identify Es multi-hop in the ionogram.First,the ionogram was preprocessed by adaptive binarization and median filtering algorithms,the effective Es echo region was extracted from ionograms.Moreover,with characteristics of Es layer echoes on ionograms,the features were selected by image projection method.The features of Es layer on the projection values of the virtual height and the occurrence time of the Es layer were used as input of the decision tree algorithm to construct the decision tree.Train a suitable decision tree model to realize the automatic identification of Es multi-hop.The automatic identification of Es multi-hop can greatly reduce the timeand manpower required to manually identify Es multi-hop,and improve the efficiency of identifying Es multi-hop.Thirdly,In order to verify the effect of Es two-hop echo on iono Scaler’s automatic measurement of F-layer parameter,this paper uses the Es two-hop automatic identification algorithm to find and remove the ionogram where Es two-hop echoes is exist,and then uses the iono Scaler software to automatically measure the F-layer parameter.And compared with the automatic measurement results of the data set with the Es two-hop ionogram,the results show that the existence of the Es two-hop echo will significantly affect the accuracy of the automatic measurement of the F-layer parameters.This work provides good guidance for the improvement of iono Scaler software.Finally,in this paper,the statistical analysis of the Es layer in Pu’er area in 2015 found that the critical frequency of the Es layer(fo Es)is mainly distributed at 4MHz-5 MHz.The average value of fo Es is significantly larger in summer than in other seasons,and it is smallest at 4: 00-8: 00 in the morning and in the afternoon.13:00-17: 00 is the largest.The virtual height of the Es layer(hv Es)is mainly distributed at 95.0 km-97.5 km,and the average value of hv Es is the largest in March and November,the smallest in May and December,and higher during the day than at night.In 2015,the highest probability of Es in Pu’er area was in June and the smallest was in February.The probability of Es in the afternoon and before midnight was slightly higher than in other periods.The physical mechanism that affects Es is discussed.The analysis shows that the Es distribution in Puer area has typical local temporal and seasonal characteristics;Es have no obvious correlation with F10.7;during the June24 magnetic storm,Es has a certain degree of enhancement.Planetary waves and tidal waves may also affect Es.However,the specific physical processes and mechanisms need further analysis. |
