The pre-earthquake ionospheric anomalies in Wenchuan,China(21°-41°N,93°-113°E)are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER(Detection of Electro-Mag...The pre-earthquake ionospheric anomalies in Wenchuan,China(21°-41°N,93°-113°E)are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER(Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions)satellite detectors ICE(Internet Communications Engine),IAP(In Application Programming),and ISL(Interior Switching Link).In this paper,we take the 12 May 2008 Wenchuan earthquake as an example,use the spatial gridding method to construct the background field over the epicenter,analyze the background characteristics of very low frequency(VLF)electric field components,low-energy particle parameters,and plasma parameters,and define the perturbation intensity index of each parameter before the earthquake to extract each parameter anomaly in both space and time dimensions.The results show that the background values of some ionospheric parameters in the Wenchuan area are related to spatial distribution.Moreover,anomalous enhancement of low-frequency electric field power spectral density,H+concentration,He+concentration and ion concentration with different intensities and anomalous weakening of ion temperature were extracted in the fifteen days before the Wenchuan earthquake.After filtering the data to exclude external interference,such as solar activity,this paper concludes that there is some connection between these anomalies and the Wenchuan earthquake.展开更多
The recently developed high-quality WHU ELF/VLF receiver system has been deployed in Suizhou, China （geomagnetic lati- tude 21.81°N, longitude 174.44°E, L=1.16） to detect low latitude extremely-low-frequen...The recently developed high-quality WHU ELF/VLF receiver system has been deployed in Suizhou, China （geomagnetic lati- tude 21.81°N, longitude 174.44°E, L=1.16） to detect low latitude extremely-low-frequency （ELF： 0.3-3 kHz） and very-low-frequency （VLF： 3-30 kHz） emissions originating from either natural or artificial sources since February 2016. Dur- ing the first-month operation of the receiver system, a total of 3039 clear whistlers have been recorded at this low latitude sta- tion with the majority （97.0%） occurring on 28 February and 1 March 2016. Observed whistlers manifest various types includ- ing single one-hop, echo train, multi-flash, and multi-path. They tend to intensify after local midnight, reach the peak around 04435 LT, and then weaken quickly. Both features of lower cutoff frequencies of most whistlers below -1.6 kHz and almost uniform dispersion for many successive multi-flash whistlers suggest that these whistlers propagate along the geomagnetic field lines in the duct mode. The computed dispersion varies between -15 s1/2 and 23 s1/2 for observed one-hop whistlers and is greater than 50 sm for three-hop echo train whistlers, indicating that the whistlers observed at the Suizhou station are low lati- tude whistlers.展开更多
The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the io...The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.展开更多
The troposphere and lower stratosphere(TLS) is a region with active atmospheric fluctuations. The Wuhan Mesosphere-Stratosphere-Troposphere(MST) radar is the first MST radar to have become operational in China's M...The troposphere and lower stratosphere(TLS) is a region with active atmospheric fluctuations. The Wuhan Mesosphere-Stratosphere-Troposphere(MST) radar is the first MST radar to have become operational in China's Mainland. It is dedicated to real-time atmospheric observations. In this paper, two case studies about inertia gravity waves(IGWs) derived from three-dimensional wind field data collected with the Wuhan MST radar are presented. The intrinsic frequencies, vertical wavelengths, horizontal wavelengths, vertical wavenumber spectra, and energy density are calculated and analyzed. In this paper, we also report on multiple waves existing in the lower stratosphere observed by the Wuhan MST radar. Lomb-Scargle spectral analysis and the hodograph method were used to derive the vertical wavenumber and propagation direction. Meanwhile, an identical IGW is observed by Wuhan MST radar both in troposphere and lower stratosphere regions. Combining the observations, the source of the latter IGW detected in the TLS would be the jet streams located in the tropopause region, which also produced wind shear above and below the tropopause.展开更多
A numerical model has been developed.Based on the numerical simulation results,the spatial effects of the ionosphere,mainly consisting of the change on electron density(ED)and electron temperature(ET),heated by the hi...A numerical model has been developed.Based on the numerical simulation results,the spatial effects of the ionosphere,mainly consisting of the change on electron density(ED)and electron temperature(ET),heated by the high frequency(HF)pump wave have been analyzed quantitatively.Results are presented as the space-time evolution regulation on the main parameters of the ionosphere resulted by the HF heating waves under the different heat-conditions,just as different regions,such as high latitude and mid-low latitude;different heating power or frequency,such as underdense heating and over-dense heating and regions at different altitudes.The heating effects in different regions with different heating conditions have been presented in figures.Finally,some primary conclusions are given by comparing the simulation results with experimental observation.展开更多
文摘The pre-earthquake ionospheric anomalies in Wenchuan,China(21°-41°N,93°-113°E)are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER(Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions)satellite detectors ICE(Internet Communications Engine),IAP(In Application Programming),and ISL(Interior Switching Link).In this paper,we take the 12 May 2008 Wenchuan earthquake as an example,use the spatial gridding method to construct the background field over the epicenter,analyze the background characteristics of very low frequency(VLF)electric field components,low-energy particle parameters,and plasma parameters,and define the perturbation intensity index of each parameter before the earthquake to extract each parameter anomaly in both space and time dimensions.The results show that the background values of some ionospheric parameters in the Wenchuan area are related to spatial distribution.Moreover,anomalous enhancement of low-frequency electric field power spectral density,H+concentration,He+concentration and ion concentration with different intensities and anomalous weakening of ion temperature were extracted in the fifteen days before the Wenchuan earthquake.After filtering the data to exclude external interference,such as solar activity,this paper concludes that there is some connection between these anomalies and the Wenchuan earthquake.
基金supported by the National Natural Science Foundation of China(Grants Nos.41204120,41474141,41304127,41304130,and 41574160)the Projects funded by China Postdoctoral Science Foundation(Grants Nos.2013M542051,2014T70732)the 985 funded project of School of Electronic information,Wuhan University
文摘The recently developed high-quality WHU ELF/VLF receiver system has been deployed in Suizhou, China （geomagnetic lati- tude 21.81°N, longitude 174.44°E, L=1.16） to detect low latitude extremely-low-frequency （ELF： 0.3-3 kHz） and very-low-frequency （VLF： 3-30 kHz） emissions originating from either natural or artificial sources since February 2016. Dur- ing the first-month operation of the receiver system, a total of 3039 clear whistlers have been recorded at this low latitude sta- tion with the majority （97.0%） occurring on 28 February and 1 March 2016. Observed whistlers manifest various types includ- ing single one-hop, echo train, multi-flash, and multi-path. They tend to intensify after local midnight, reach the peak around 04435 LT, and then weaken quickly. Both features of lower cutoff frequencies of most whistlers below -1.6 kHz and almost uniform dispersion for many successive multi-flash whistlers suggest that these whistlers propagate along the geomagnetic field lines in the duct mode. The computed dispersion varies between -15 s1/2 and 23 s1/2 for observed one-hop whistlers and is greater than 50 sm for three-hop echo train whistlers, indicating that the whistlers observed at the Suizhou station are low lati- tude whistlers.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804042 and 41074115)the Post Doctor Foundation of China (Grant No. 200902445)the Fundamental Research Funds for the Central Universities (Grant No. 4081004)
文摘The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.
基金supported by the National Natural Science Foundation of China (Grant No. 41204111)the Fundamental Research Fund for the Central Universities of China (Grant No. 2014212020202)
文摘The troposphere and lower stratosphere(TLS) is a region with active atmospheric fluctuations. The Wuhan Mesosphere-Stratosphere-Troposphere(MST) radar is the first MST radar to have become operational in China's Mainland. It is dedicated to real-time atmospheric observations. In this paper, two case studies about inertia gravity waves(IGWs) derived from three-dimensional wind field data collected with the Wuhan MST radar are presented. The intrinsic frequencies, vertical wavelengths, horizontal wavelengths, vertical wavenumber spectra, and energy density are calculated and analyzed. In this paper, we also report on multiple waves existing in the lower stratosphere observed by the Wuhan MST radar. Lomb-Scargle spectral analysis and the hodograph method were used to derive the vertical wavenumber and propagation direction. Meanwhile, an identical IGW is observed by Wuhan MST radar both in troposphere and lower stratosphere regions. Combining the observations, the source of the latter IGW detected in the TLS would be the jet streams located in the tropopause region, which also produced wind shear above and below the tropopause.
基金supported by the Hi-Tech Research and Development Program of China(No.2004733AA101).
文摘A numerical model has been developed.Based on the numerical simulation results,the spatial effects of the ionosphere,mainly consisting of the change on electron density(ED)and electron temperature(ET),heated by the high frequency(HF)pump wave have been analyzed quantitatively.Results are presented as the space-time evolution regulation on the main parameters of the ionosphere resulted by the HF heating waves under the different heat-conditions,just as different regions,such as high latitude and mid-low latitude;different heating power or frequency,such as underdense heating and over-dense heating and regions at different altitudes.The heating effects in different regions with different heating conditions have been presented in figures.Finally,some primary conclusions are given by comparing the simulation results with experimental observation.
