利用DEMETER卫星LANGMIUR探针观测数据研究强震前的电离层扰动
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摘要
文中介绍了Langmiur探针的观测原理,并利用电子浓度(Ne)和电子温度(Te)数据研究了2006年5月3日MW7.9汤加地震和2006年12月16日MW7.1台湾地震。结果发现汤加地震前2～5d电子浓度连续4d降低,电子温度变化不明显。台湾地震前后电子浓度的变化不明显,但电子温度在地震当天及后续3d出现了低值。目前没有直接的证据表明这些变化是由地震活动引发的,但在数据处理过程中选择了当地22时至次日3时的观测数据,并且剔除了Dst≤-30nT,Kp≥3,AE≥200nT时的记录数据,在一定程度上排除了太阳、地磁等因素引起的电离层异常情况。
Using Ne(electron density) and Te(electron temperature) data of Langmuir Probe onboard DEMETER(Detection of Electro-magnetic Emissions Transmitted from Earthquake Regions) satellite,the paper studies the variations of electron density and electron temperature associated with strong earthquakes.The specific scientific objectives of Langmuir Probe are to map the bulk plasma parameters and to study their variations associated with seismic activity,volcanism and human activity and other sources of perturbations.Langmuir probe sweeps in voltage allow to obtain a current-voltage(Ⅰ-Ⅴ) characteristic every second.Bulk plasma parameters are obtained from the analysis of the Ⅰ-Ⅴ characteristics.The work principle,data format of Langmuir Probe onboard DEMETER is briefly introduced.We mainly studied the 2006 MW 7.9 Tonga earthquake and the MW 7.1 Taiwan earthquake in this paper.For each earthquake,we choose the orbits which passed over the area about 2000km around epicenter,including four months data before and two months data after the earthquakes.There are mainly three steps to reprocess the raw data,in order to avoid disturbances resulting from solar activities and geomagnetic activities.The result on the MW 7.9 Tonga earthquake shows that at the equatorial region the electron density was relatively low before 28 April,while it began to increase from 28 April,and got the highest at 2 May one day before the earthquake.Until 4 May after the main shock,Ne began to decline.Based on comparison between revisited orbits,the orbit 097681(before shock) and 098721(after shock) observed certain disturbance.To further investigate the features of the preearthquake ionospheric anomalies,using 5 days as time window and 1 day as step size,we examined the temporal and spatial evolution of electron density within the area of 2000km around epicenter.Results show that the normal distribution of Ne kept at a relatively high level,except a relatively sharp reduction of Ne from 29 April to 2 May.The result on the MW 7.1Taiwan earthquake shows that Ne changed randomly,while Te kept at a relatively high level,but dropped gradually before the quake.Currently we have no evidence to conclude that these changes are the results from the seismic activity,but based on data reprocessing,we can exclude the disturbances induced by solar activity and magnetic field at certain degree.If these changes of Ne/Te really resulted from earthquake,we may prudently conclude that ionospheric disturbance associated with seismic activity may possibly occur in a short time impending an earthquake with a short duration.
Using Ne(electron density) and Te(electron temperature) data of Langmuir Probe onboard DEMETER(Detection of Electro-magnetic Emissions Transmitted from Earthquake Regions) satellite,the paper studies the variations of electron density and electron temperature associated with strong earthquakes.The specific scientific objectives of Langmuir Probe are to map the bulk plasma parameters and to study their variations associated with seismic activity,volcanism and human activity and other sources of perturbations.Langmuir probe sweeps in voltage allow to obtain a current-voltage(Ⅰ-Ⅴ) characteristic every second.Bulk plasma parameters are obtained from the analysis of the Ⅰ-Ⅴ characteristics.The work principle,data format of Langmuir Probe onboard DEMETER is briefly introduced.We mainly studied the 2006 MW 7.9 Tonga earthquake and the MW 7.1 Taiwan earthquake in this paper.For each earthquake,we choose the orbits which passed over the area about 2000km around epicenter,including four months data before and two months data after the earthquakes.There are mainly three steps to reprocess the raw data,in order to avoid disturbances resulting from solar activities and geomagnetic activities.The result on the MW 7.9 Tonga earthquake shows that at the equatorial region the electron density was relatively low before 28 April,while it began to increase from 28 April,and got the highest at 2 May one day before the earthquake.Until 4 May after the main shock,Ne began to decline.Based on comparison between revisited orbits,the orbit 097681(before shock) and 098721(after shock) observed certain disturbance.To further investigate the features of the preearthquake ionospheric anomalies,using 5 days as time window and 1 day as step size,we examined the temporal and spatial evolution of electron density within the area of 2000km around epicenter.Results show that the normal distribution of Ne kept at a relatively high level,except a relatively sharp reduction of Ne from 29 April to 2 May.The result on the MW 7.1Taiwan earthquake shows that Ne changed randomly,while Te kept at a relatively high level,but dropped gradually before the quake.Currently we have no evidence to conclude that these changes are the results from the seismic activity,but based on data reprocessing,we can exclude the disturbances induced by solar activity and magnetic field at certain degree.If these changes of Ne/Te really resulted from earthquake,we may prudently conclude that ionospheric disturbance associated with seismic activity may possibly occur in a short time impending an earthquake with a short duration.
引文
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赵国泽,陈小斌,蔡军涛.2007.电磁卫星和地震预测[J].地球物理学进展,22(3):667—673.ZHAO Guo-ze,CHEN Xiao-bin,CAI Jun-tao.2007.Electromagnetic observation by satellite and earthquake prediction[J].Progress in Geophysics,22(3):667—673(in Chinese).
张学民,赵国泽,陈小斌,等.2007.国外地震电磁现象观测[J].地球物理学进展,22(3):687—694.ZHANG Xue-min,ZHAO Guo-ze,CHEN Xiao-bin,et al.2007.Seismo-electromagnetic observation abroad[J].Progress in Geophysics,22(3):687—694(in Chinese).
曾昭宪,王世金,曾力.2006.基于Langmiur探针技术的空间等离子体探测方法[J].上海航天,5:41—45.ZENG Zhao-xian,WANG Shi-jin,ZENG Li.2006.Space plasma detecting method based on the Langmuir Probe[J].Aerospace Shanghai,5:41—45(in Chinese).
曾中超,张蓓,方广有,等.2009.利用DEMETER卫星数据分析汶川地震前的电离层异常[J].地球物理学报,52(1):11—19.ZENG Zhong-chao,ZHANG Bei,FANG Guang-you,et al.2009.The analysis of ionospheric variations before Wenchuan earthquake with DEMETER data[J].Chinese J Geophys,52(1):11—19(in Chinese).
Barnes R A,Leonard R S.1965.Observations of ionospheric disturbances following the Alaska earthquake[J].J Geo-phys Res,70:1250—1253.
Calais E,Minster J B.1995.GPS detection of ionospheric perturbations following the January17,1994,Northridge earth-quake[J].Geophys Res Lett,22:1045—1048.
Hayakawa M.2004.Electromagnetic phenomena associated with earthquakes:A frontier in terrestrial electromagnetic noise environment[J].Recent Res Devel Geophysics,6:81—112.
Isaev N V,Serebryakova O N.2001.Electromagnetic and plasma effects of seismic activity in the earth ionosphere[J].Chem Phys Reports,19:1177—1188.
Lebreton J P,Stverak S,Travnicek P,et al.2006.The ISL Langmuir Probe experiment and its data processiing onboard DEMETER:Scientific objectives,description and first results[J].Planetary and Space Science,54:472—486.
Liu J Y,Chen YⅠ,Pulinets S A,et al.2000.Seismo-ionosphere signatures prior to M≥6.0Taiwan earthquake[J].Geophys Res Lett,27:3113—3116.
Molchanov O A,Fedorov E,Schekotov A,et al.2004.Lithosphere-atmosphere-ionosphere coupling as governing mecha-nism for preseismic short-term events in atmosphere and ionosphere[J].Natural Hazards and Earth System Sci-ences,4:757—767.
Oyama KⅠ,Kakinami Y,Liu J Y,et al.2008.Behaviour of ionosphere Te and Ne prior to earthquake-Role of earth-quake related electric field[J].Journal of Geophysical Research,113:A11317.1—A11317.14.
Parrot M,Berthelier J J,Lebreton J P,et al.2006.Examples of unusual ionospheric observations made by the DEME-TER satellite over seismic regions[J].Phys Chem Earth,31:486—495.
Pulinets S A,Legen'ka A D.2003.Spatial-temporal characteristics of the large scale disturbances of the electron concen-tration observed in the F-region of the ionosphere before strong earthquake[J].Cosm Res,41:221—229.
Pulinets S,Boyarchuk K.2004.Ionospheric Precursors of Earthquakes[M].Springer Verlag.
Sarkar S,Gwal A K,Parrot M.2007.Ionospheric variations observed by the DEMETER satellite in the midlatitude re-gion during strong earthquakes[J].Journal of Atmospheric and Solar Terrestrial Physics,69:1524—1540.
Zhang X,Shen X,Liu J,et al.2009.Analysis of ionospheric plasma perturbations before Wenchuan earthquake[J].Natural Hazards and Earth System Sciences,28:1259—1266.
赵国泽,陈小斌,蔡军涛.2007.电磁卫星和地震预测[J].地球物理学进展,22(3):667—673.ZHAO Guo-ze,CHEN Xiao-bin,CAI Jun-tao.2007.Electromagnetic observation by satellite and earthquake prediction[J].Progress in Geophysics,22(3):667—673(in Chinese).
张学民,赵国泽,陈小斌,等.2007.国外地震电磁现象观测[J].地球物理学进展,22(3):687—694.ZHANG Xue-min,ZHAO Guo-ze,CHEN Xiao-bin,et al.2007.Seismo-electromagnetic observation abroad[J].Progress in Geophysics,22(3):687—694(in Chinese).
曾昭宪,王世金,曾力.2006.基于Langmiur探针技术的空间等离子体探测方法[J].上海航天,5:41—45.ZENG Zhao-xian,WANG Shi-jin,ZENG Li.2006.Space plasma detecting method based on the Langmuir Probe[J].Aerospace Shanghai,5:41—45(in Chinese).
曾中超,张蓓,方广有,等.2009.利用DEMETER卫星数据分析汶川地震前的电离层异常[J].地球物理学报,52(1):11—19.ZENG Zhong-chao,ZHANG Bei,FANG Guang-you,et al.2009.The analysis of ionospheric variations before Wenchuan earthquake with DEMETER data[J].Chinese J Geophys,52(1):11—19(in Chinese).
Barnes R A,Leonard R S.1965.Observations of ionospheric disturbances following the Alaska earthquake[J].J Geo-phys Res,70:1250—1253.
Calais E,Minster J B.1995.GPS detection of ionospheric perturbations following the January17,1994,Northridge earth-quake[J].Geophys Res Lett,22:1045—1048.
Hayakawa M.2004.Electromagnetic phenomena associated with earthquakes:A frontier in terrestrial electromagnetic noise environment[J].Recent Res Devel Geophysics,6:81—112.
Isaev N V,Serebryakova O N.2001.Electromagnetic and plasma effects of seismic activity in the earth ionosphere[J].Chem Phys Reports,19:1177—1188.
Lebreton J P,Stverak S,Travnicek P,et al.2006.The ISL Langmuir Probe experiment and its data processiing onboard DEMETER:Scientific objectives,description and first results[J].Planetary and Space Science,54:472—486.
Liu J Y,Chen YⅠ,Pulinets S A,et al.2000.Seismo-ionosphere signatures prior to M≥6.0Taiwan earthquake[J].Geophys Res Lett,27:3113—3116.
Molchanov O A,Fedorov E,Schekotov A,et al.2004.Lithosphere-atmosphere-ionosphere coupling as governing mecha-nism for preseismic short-term events in atmosphere and ionosphere[J].Natural Hazards and Earth System Sci-ences,4:757—767.
Oyama KⅠ,Kakinami Y,Liu J Y,et al.2008.Behaviour of ionosphere Te and Ne prior to earthquake-Role of earth-quake related electric field[J].Journal of Geophysical Research,113:A11317.1—A11317.14.
Parrot M,Berthelier J J,Lebreton J P,et al.2006.Examples of unusual ionospheric observations made by the DEME-TER satellite over seismic regions[J].Phys Chem Earth,31:486—495.
Pulinets S A,Legen'ka A D.2003.Spatial-temporal characteristics of the large scale disturbances of the electron concen-tration observed in the F-region of the ionosphere before strong earthquake[J].Cosm Res,41:221—229.
Pulinets S,Boyarchuk K.2004.Ionospheric Precursors of Earthquakes[M].Springer Verlag.
Sarkar S,Gwal A K,Parrot M.2007.Ionospheric variations observed by the DEMETER satellite in the midlatitude re-gion during strong earthquakes[J].Journal of Atmospheric and Solar Terrestrial Physics,69:1524—1540.
Zhang X,Shen X,Liu J,et al.2009.Analysis of ionospheric plasma perturbations before Wenchuan earthquake[J].Natural Hazards and Earth System Sciences,28:1259—1266.
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