基于FIR滤波的磁静期电离层-磁层磁场信号分离
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摘要
Swarm是欧空局第4个"地球探测者"任务,其主要目的是确定地球磁场及其时空演化特征。利用Swarm构建地球各圈层磁场模型的关键问题之一是对不同场源的地磁信号实施准确分离。以Swarm磁静期观测数据为例,采用FIR沿轨高通滤波对外源场信号进行处理,分析并给出了滤波器窗口长度的确定方法,利用欧空局2016年发布的MIO_SHA_2D和MMA_SHA_2C电离层-磁层磁场模型验证了该方法的可行性。结果表明:FIR对外源场长波信号的滤波结果与模型改正结果的一致性吻合较好,在给定通带波长1 200 km、阻带波长3 000 km的情况下,将滤波器长度设置为87～129阶,可同时顾及水平方向和径向方向的滤波精度。
Swarm, the fourth "Earth Explorer" mission of the ESA, is mainly to determine the geomagnetic field. One of the key issues in using Swarm's data to construct the magnetic field model for each layer of the earth is to accurately separate geomagnetic signals from different field sources. In this paper, based on quiet magnetic period observations data of the ESA's Swarm satellites, the external source fields are processed with finite impulse response(FIR) high-pass filtering along the satellite tracks, the length of the filter window is discussed. In addition, the feasibility of this method is proven by the MIO_SHA_2D and MMA_SHA_2C, which are ionospheric and magnetospheric magnetic field models published by the ESA in 2016. The results indicate that the outcome of FIR filter for long wave signals of the external source fields well agree with the model correction results. When the passband and stopband wavelengths are set to 1 200 km and 3 000 km, respectively, if we set the length of the filter to 87-129 orders, it can achieve a better balance of the filtering accuracy in the horizontal and radial.
Swarm, the fourth "Earth Explorer" mission of the ESA, is mainly to determine the geomagnetic field. One of the key issues in using Swarm's data to construct the magnetic field model for each layer of the earth is to accurately separate geomagnetic signals from different field sources. In this paper, based on quiet magnetic period observations data of the ESA's Swarm satellites, the external source fields are processed with finite impulse response(FIR) high-pass filtering along the satellite tracks, the length of the filter window is discussed. In addition, the feasibility of this method is proven by the MIO_SHA_2D and MMA_SHA_2C, which are ionospheric and magnetospheric magnetic field models published by the ESA in 2016. The results indicate that the outcome of FIR filter for long wave signals of the external source fields well agree with the model correction results. When the passband and stopband wavelengths are set to 1 200 km and 3 000 km, respectively, if we set the length of the filter to 87-129 orders, it can achieve a better balance of the filtering accuracy in the horizontal and radial.
引文
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[10] Sabaka T J,Olsen N.Enhancing Comprehensive Inversions Using the Swarm Constellation[J].Earth,Planets and Space,2006,58(4):371-395
[11] Lühr H,Maus S.Solar Cycle Dependence of Quiet-time Magnetospheric Currents and a Model of Their Near-Earth Magnetic Fields[J].Earth,Planets and Space,2010,62(10):843-848
[12] Olsen N,Sabaka T J,Lowes F.New Parameterization of External and Induced Fields in Geomagnetic field Modeling,and a Candidate Model for IGRF 2005[J].Earth,Planets and Space,2005,57(12):1 141-1 149
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[14] Olsen N,Friischristensen E,Floberghagen R,et al.The Swarm Satellite Constellation Application and Research Facility (SCARF) and Swarm Data Produ-cts[J].Earth,Planets and Space,2013,65(11):1 189-1 200
[15] Chulliat A,Vigneron P,Thébault E,et al.Swarm SCARF Dedicated Ionospheric Field Inversion Chain[J].Earth,Planets and Space,2013,65(11):1 257-1 270
[16] Thébault E.Global Lithospheric Magnetic Field Modelling by Successive Regional Analysis[J].Earth,Planets and Space,2006,58(4):485-495
[17] Zhou Boyang,Luo Zhicai,Ning Jinsheng,et al.Design of FIR Lowpass Digital filters for Airborne Vector Gravimetry [J].Geomatics and Information Science of Wuhan University,2015,40(6):772-778(周波阳,罗志才,宁津生,等.航空矢量重力测量中有限冲激响应低通数字滤波器的设计[J].武汉大学学报·信息科学报,2015,40(6):772-778)
[18] Sun Zhongmiao,Xia Zheren,Li Yingchun.Determination and Analysis of the Beam Scale Factor for the LaCoste&Romberg Airborne Gravimeter [J].Geomatics and Information Science of Wuhan University,2002,27(4):367-371 (孙中苗,夏哲仁,李迎春.L&R航空重力仪摆杆尺度因子的确定与分析[J].武汉大学学报·信息科学版,2002,27(4):367-371)
[19] Maus S,Yin F,Lühr H,et al.Resolution of Direction of Oceanic Magnetic Lineations by the Sixth-generation Lithospheric Magnetic Field Model from CHAMP Satellite Magnetic Measurements [J].Geo-chemistry Geophysics Geosystems,2008,9(7):1 335-1 346
[20] Kother L,Hammer M D,Finlay C C,et al.An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field [J].Geophysical Journal International,2015,203(1):553-566
[21] Huang Cheng.Using LAGEOS Laser Ranging Data to Accurately Measure the Earth Rotation Parameters [D].Shanghai:Shanghai Astronomical Observatory,Chinese Academy of Sciences,1985(黄珹.利用LAGEOS激光测距资料精确测定地球自转参数[D].上海:中国科学院上海天文台,1985)
[22] Yan Haojian.Space-based GPS Meteorology and Inversion Technique[M].Beijing:China Science and Technology Press,2007(严豪健.天基GPS气象学与反演技术[M].北京:中国科学技术出版社,2007)
[23] Chen Huaichen.MATLAB and Its Application in the Course of Science and Engineering[M].Xi’an:Xidian University Press,2007(陈怀琛.MATLAB及其在理工课程中的应用指南[M].西安:西安电子科技大学出版社,2007)
[24] Sun Zhongmiao,Xiazheren.Optimal Determination of the Lowpass Filter Parameters in Airborne Gravimetry[J].Journal of the PLA Institute of Surveying & Mapping,2002(1):11-14,18(孙中苗,夏哲仁.航空重力测量中低通滤波器参数的优选[J].测绘科学技术学报,2002(1):11-14,18
[2] Chang Yifeng.Research on Satellite Geomagnetic Data Process and Geomagnetic Model Recovery Theory and Method[D].Zhengzhou:Information Engineering University,2015(常宜峰.卫星磁测数据处理与地磁场模型反演理论与方法研究[D].郑州:信息工程大学,2015)
[3] An Zhenchang,Tan Donghai,Wang Yuehua,et al.Mangnetic Anomalies for Qinghai-Xizang (Tibetan) Plateau and Adjacent Region Derived from MAGSAT Data [J].Acta Geodaetica et Cartographica Sinica,1996,25(3):221-225(安振昌,谭东海,王月华,等.利用MAGSAT卫星数据研究青藏高原及其邻近地区磁异常[J].测绘学报,1996,25(3):221-225)
[4] Ou J,Gillet N,Du A.Geomagnetic Observatory Monthly Series,1930 to 2010:Empirical Analysis and Unmodeled Signal Estimation[J].Earth,Planets and Space,2015,67(1):1-20
[5] Du Jinsong,Chen Chao.Progress and Outlook in Global Lithospheric Magnetic Field Modelling by Satellite Magnetic Measurements [J].Progress in Geophysics,2015,30(3):1 017-1 033 (杜劲松,陈超.基于卫星磁测数据的全球岩石圈磁场建模进展与展望[J].地球物理学进展,2015,30(3):1 017-1 033)
[6] Qu Chunkai,Li Fei,Yang Xuan,et al.Improving MEX Orbit Determination Accuracy by Using Zero- Phase Kaiser Window Filter[J].Geomatics and Information Science of Wuhan University,2018,43(7) :1 071-1 077(曲春凯,李斐,杨轩,等.利用零相位Kaiser窗滤波器改善MEX多普勒数据定轨精度[J].武汉大学学报·信息科学版,2018,43(7):1 071-1 077)
[7] Thébault E,Vigneron P,Maus S,et al.Swarm SCARF Dedicated Lithospheric Field Inversion Chain[J].Earth,Planets and Space,2013,65(11):1 257-1 270
[8] Sabaka T J,Olsen N,Langel R A.A Comprehensive Model of the Quiet-time,Near-Earth Magnetic Field:Phase 3[J].Geophysical Journal International,2002,151(1):32-68
[9] Sabaka T J,Olsen N,Purucker M E.Extending Comprehensive Models of the éarth’s Magnetic Field with ?rsted and CHAMP Data[J].Geophysical Journal International,2004,159(2):521-547
[10] Sabaka T J,Olsen N.Enhancing Comprehensive Inversions Using the Swarm Constellation[J].Earth,Planets and Space,2006,58(4):371-395
[11] Lühr H,Maus S.Solar Cycle Dependence of Quiet-time Magnetospheric Currents and a Model of Their Near-Earth Magnetic Fields[J].Earth,Planets and Space,2010,62(10):843-848
[12] Olsen N,Sabaka T J,Lowes F.New Parameterization of External and Induced Fields in Geomagnetic field Modeling,and a Candidate Model for IGRF 2005[J].Earth,Planets and Space,2005,57(12):1 141-1 149
[13] Feng yan,An Zhenchang,Mao Fei,et al.Study on External Weak Magnetic Field During Magnetic Quiet Periods over Chinese Mainland[J].Chinese Journal of Space Science,2012,32(3):321-335 (冯彦,安振昌,毛飞,等.磁静日期间中国大陆地区外源弱磁场研究[J].空间科学学报,2012,32(3):321-335)
[14] Olsen N,Friischristensen E,Floberghagen R,et al.The Swarm Satellite Constellation Application and Research Facility (SCARF) and Swarm Data Produ-cts[J].Earth,Planets and Space,2013,65(11):1 189-1 200
[15] Chulliat A,Vigneron P,Thébault E,et al.Swarm SCARF Dedicated Ionospheric Field Inversion Chain[J].Earth,Planets and Space,2013,65(11):1 257-1 270
[16] Thébault E.Global Lithospheric Magnetic Field Modelling by Successive Regional Analysis[J].Earth,Planets and Space,2006,58(4):485-495
[17] Zhou Boyang,Luo Zhicai,Ning Jinsheng,et al.Design of FIR Lowpass Digital filters for Airborne Vector Gravimetry [J].Geomatics and Information Science of Wuhan University,2015,40(6):772-778(周波阳,罗志才,宁津生,等.航空矢量重力测量中有限冲激响应低通数字滤波器的设计[J].武汉大学学报·信息科学报,2015,40(6):772-778)
[18] Sun Zhongmiao,Xia Zheren,Li Yingchun.Determination and Analysis of the Beam Scale Factor for the LaCoste&Romberg Airborne Gravimeter [J].Geomatics and Information Science of Wuhan University,2002,27(4):367-371 (孙中苗,夏哲仁,李迎春.L&R航空重力仪摆杆尺度因子的确定与分析[J].武汉大学学报·信息科学版,2002,27(4):367-371)
[19] Maus S,Yin F,Lühr H,et al.Resolution of Direction of Oceanic Magnetic Lineations by the Sixth-generation Lithospheric Magnetic Field Model from CHAMP Satellite Magnetic Measurements [J].Geo-chemistry Geophysics Geosystems,2008,9(7):1 335-1 346
[20] Kother L,Hammer M D,Finlay C C,et al.An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field [J].Geophysical Journal International,2015,203(1):553-566
[21] Huang Cheng.Using LAGEOS Laser Ranging Data to Accurately Measure the Earth Rotation Parameters [D].Shanghai:Shanghai Astronomical Observatory,Chinese Academy of Sciences,1985(黄珹.利用LAGEOS激光测距资料精确测定地球自转参数[D].上海:中国科学院上海天文台,1985)
[22] Yan Haojian.Space-based GPS Meteorology and Inversion Technique[M].Beijing:China Science and Technology Press,2007(严豪健.天基GPS气象学与反演技术[M].北京:中国科学技术出版社,2007)
[23] Chen Huaichen.MATLAB and Its Application in the Course of Science and Engineering[M].Xi’an:Xidian University Press,2007(陈怀琛.MATLAB及其在理工课程中的应用指南[M].西安:西安电子科技大学出版社,2007)
[24] Sun Zhongmiao,Xiazheren.Optimal Determination of the Lowpass Filter Parameters in Airborne Gravimetry[J].Journal of the PLA Institute of Surveying & Mapping,2002(1):11-14,18(孙中苗,夏哲仁.航空重力测量中低通滤波器参数的优选[J].测绘科学技术学报,2002(1):11-14,18