| Electromagnetic ion cyclotron wave is a common electromagnetic emission in the earth’s magnetosphere,which plays an important role in magnetosphere particle dynamics.Because of the regional limitations of previous studies on the global distribution of EMIC waves and the incomplete periodically modulated physical scenario,the Van Allen Probe(VAP)and Magnetospheric Multiscale(MMS)data are used to investigate the following issures:1)The automatic algorithm of EMIC wave recognition.An automatic algorithm of EMIC wave recognition is developed,including the data reading module,the PSD acquisition module,the automatic recognition module and,the time storage module.The algorithm is demonstrated to be available by automatic identification of different events,which provides useful tools for the subsequent statistical studies.2)The global distribution characteristics of EMIC waves in the Earth’s magnetosphere.The observation data of VAP-A satellite and MMS-1 satellite are combined to obtain the distribution characteristics of EMIC waves in the spatial range L=3-10.The statistical results show that the EMIC wave has the maximum occurrence rate about 34.7%at L～7-9,and MLT～13:00-14:00.Besides,the EMIC wave has the secondary peak value of occurrence rate 12.7%at dawn region L～6-10 in MLT～05:00-08:00.The occurrence rate of dayside is significantly higher than that of night side,and the occurrence rate of the high L-shell region is much higher than that of the low L-shell region.3)The periodic modulation of EMIC Wave:(a)The data from MMS and WIND satellites show that the solar wind dynamic pressure is the generation of periodic EMIC wave packet by modulating the growth rate of EMIC wave.The observations of solar wind,EMIC wave,proton distribution and ULF wave support the proposition.(b)Using the data from two MMS satellites,we analyze a periodic modulation even of the EMIC wave in broad region,and obtain the time scale that the periodic modulation can last.In this paper,we develop an automatic recognition algorithm to recognize the EMIC waves obtained by VAP and MMS satellites from September1,2015 to September 30,2018,and completes the global distribution statistics of EMIC waves in the region of L=3-10.It is beneficial to further study on the excitation and propagation of EMIC waves and the effect of EMIC waves on magnetospheric particles and space weather.Additional,multi-satellite combined obserrvations are used to research the periodic EMIC wave modulation,whose time scale is proved to be several hours.It shows the process that the solar wind energy affect the magnetospheric EMIC wave and thus the magnetospheric dynamics process. |
