scholarly journals Investigation of TEC and VLF space measurements associated to L'Aquila (Italy) earthquakes

2011 ◽  
Vol 11 (4) ◽  
pp. 1019-1024 ◽  
Author(s):  
G. Stangl ◽  
M. Y. Boudjada ◽  
P. F. Biagi ◽  
S. Krauss ◽  
A. Maier ◽  
...  
Keyword(s):  
Low Frequency ◽  
Time Profile ◽  
Electron Content ◽  
Pixel Resolution ◽  
Electronic Density ◽  
Total Electron ◽  
Demeter Satellite ◽  
Before And After ◽  
The One ◽  
A Tec

Abstract. In this study, we report on Total Electron Content (TEC) and Very Low Frequency (VLF) space measurements derived from Global Positioning System (GPS) and DEMETER satellites, respectively. These measurements are associated with the earthquake (EQ) of a magnitude of 6.3, which occurred on 6 April 2009, in L'Aquila (Italy). Anomaly features are derived from the analysis of TEC and VLF observations recorded two weeks before and after the seismic event occurrence. A TEC map with an interpolated regional pixel resolution of 1° × 1° × 15 min in latitude, longitude and time was generated, allowing for the checking of a possible presence of disturbances over the L'Aquila region. This analysis is combined with the study of the time profile associated to the VLF flux density variations recorded by the Instrument Champ Electrique (ICE) experiment on-board DEMETER satellite. We discuss, on the one hand, the combination efficiency of the electronic density and the VLF electromagnetic measurements and, on the other hand, the difficulty to distinguish between global effects and regional ones related to the earthquake.

scholarly journals Investigation of GIM-TEC disturbances before M ≥ 6.0 inland earthquakes during 2003–2017

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fuying Zhu ◽  
Yingchun Jiang
Keyword(s):  
Rapid Development ◽  
Science Research ◽  
Satellite System ◽  
Statistical Investigation ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Distributions ◽  
Before And After ◽  
Global Ionosphere Map ◽  
Global Navigation Satellite

Abstract With the rapid development of the Global Navigation Satellite System (GNSS) and its wide applications to atmospheric science research, the global ionosphere map (GIM) total electron content (TEC) data are extensively used as a potential tool to detect ionospheric disturbances related to seismic activity and they are frequently used to statistically study the relation between the ionosphere and earthquakes (EQs). Indeed, due to the distribution of ground based GPS receivers is very sparse or absent in large areas of ocean, the GIM-TEC data over oceans are results of interpolation between stations and extrapolation in both space and time, and therefore, they are not suitable for studying the marine EQs. In this paper, based on the GIM-TEC data, a statistical investigation of ionospheric TEC variations of 15 days before and after the 276 M ≥ 6.0 inland EQs is undertaken. After eliminating the interference of geomagnetic activities, the spatial and temporal distributions of the ionospheric TEC disturbances before and after the EQs are investigated and compared. There are no particularly distinct features in the time distribution of the ionospheric TEC disturbances before the inland EQs. However, there are some differences in the spatial distribution, and the biggest difference is precisely in the epicenter area. On the other hand, the occurrence rates of ionospheric TEC disturbances within 5 days before the EQs are overall higher than those after EQs, in addition both of them slightly increase with the earthquake magnitude. These results suggest that the anomalous variations of the GIM-TEC before the EQs might be related to the seismic activities.

scholarly journals Ionospheric Anomalies Related to the (M = 7.3), August 27, 2012, Puerto Earthquake, (M = 6.8), August 30, 2012 Jan Mayen Island Earthquake, and (M = 7.6), August 31, 2012, Philippines Earthquake: Two-Dimensional Principal Component Analysis

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Jyh-Woei Lin
Keyword(s):  
Principal Component Analysis ◽  
Principal Component ◽  
Component Analysis ◽  
The Philippines ◽  
Electron Content ◽  
Two Dimensional ◽  
Total Electron ◽  
Duration Time ◽  
Time Period ◽  
A Tec

Two-dimensional principal component analysis (2DPCA) and principal component analysis (PCA) are used to examine the ionospheric total electron content (TEC) data during the time period from 00:00 on August 21 to 12: 45 on August 31 (UT), which are 10 days before the M = 7.6 Philippines earthquake at 12:47:34 on August 31, 2012 (UT) with the depth at 34.9 km. From the results by using 2DPCA, a TEC precursor of Philippines earthquake is found during the time period from 4:25 to 4:40 on August 28, 2012 (UT) with the duration time of at least 15 minutes. Another earthquake-related TEC anomaly is detectable for the time period from 04:35 to 04:40 on August 27, 2012 (UT) with the duration time of at least 5 minutes during the Puerto earthquake at 04: 37:20 on August 27, 2012 (UT) (Mw= 7.3) with the depth at 20.3 km. The precursor of the Puerto earthquake is not detectable. TEC anomaly is not to be found related to the Jan Mayen Island earthquake (Mw= 6.8) at 13:43:24 on August 30, 2012 (UT). These earthquake-related TEC anomalies are detectable by using 2DPCA rather than PCA. They are localized nearby the epicenters of the Philippines and Puerto earthquakes.

scholarly journals A multi-instrumental and modelling analysis of the ionospheric responses to the solar eclipse of December 14, 2020, over the Brazilian region

2021 ◽  
Author(s):  
Laysa Cristina Araujo Resende ◽  
Yajun Zhu ◽  
Clezio Marcos Denardini ◽  
Sony Su Chen ◽  
Ronan Arraes Jardim Chagas ◽  
...  
Keyword(s):  
Solar Eclipse ◽  
Satellite System ◽  
Electron Content ◽  
Electronic Density ◽  
Total Electron ◽  
Density Reduction ◽  
Modelling Analysis ◽  
E Region ◽  
South Of Brazil ◽  
Global Navigation Satellite

Abstract. This work presents an analysis of the ionospheric responses to the solar eclipse that occurred on December 14, 2020, over the Brazilian sector. This event partially covers the south of Brazil, providing an excellent opportunity to study the modifications in the peculiarities that occur in this sector, as the Equatorial Ionization Anomaly (EIA). Therefore, we used the Digisonde data available in this period for two sites, Campo Grande (CG, 20.47° S, 54.60° W, dip ∼23° S) and Cachoeira Paulista (CXP, 22.70° S, 45.01° W, dip ∼35° S), assessing the E, and F regions, and Es layer behaviors. Additionally, a numerical model (MIRE, Portuguese acronym for E Region Ionospheric Model) is used to analyze the E layer dynamics modification around these times. The results show the F1 region disappearance and an apparent electronic density reduction in the E region during the solar eclipse. We also analyzed the total electron content (TEC) maps from the Global Navigation Satellite System (GNSS) that indicate a weakness in the EIA. On the other hand, we observe the rise of the Es layer electron density, which is related to the gravity waves strengthened during solar eclipse events. Finally, our results lead to a better understanding of the restructuring mechanisms in the ionosphere at low latitudes during the solar eclipse events, even though they only partially reached the studied regions.

Direction of ionospheric structures in LOFAR calibration data

2020 ◽  
Author(s):  
Katarzyna Budzińska ◽  
Maaijke Mevius ◽  
Marcin Grzesiak ◽  
Mariusz Pożoga ◽  
Barbara Matyjasiak ◽  
...  
Keyword(s):  
Low Frequency ◽  
High Sensitivity ◽  
Electromagnetic Signal ◽  
Electron Content ◽  
Calibration Data ◽  
Total Electron ◽  
Medium Scale ◽  
Frequency Regime ◽  
Scale Structures

<pre>The Low Frequency Array (LOFAR) interferometer is a radio telescope network that provides the radio astronomical observations with the highest up-to-date sensitivity in the frequency regime between 10 and 240 MHz. As these frequencies approach the ionospheric plasma frequency, ionospheric perturbation of propagating electromagnetic signal is the main environmental factor affecting the quality of observations. Removal of ionospheric influence is a part of routinely conducted data calibration, resulting in high sensitivity differential Total Electron Content (dTEC) values between LOFAR stations. In this study we present a method for medium scale ionospheric structures detection applied to interferometric data obtained from calibration solutions of one of the key LOFAR projects- the Epoch of Reionization. Each observation spans 110-250 MHz of frequency range and lasts 6-8 hours during winter nighttime. Due to operating frequency and sensitivity of interferometric data, studies conducted with LOFAR can complement GNSS research with medium scale structures.</pre>

scholarly journals Seismo-ionospheric anomalies in ionospheric TEC and plasma density before the 17 July 2006 <i>M</i>7.7 south of Java earthquake

2017 ◽  
Vol 35 (3) ◽  
pp. 589-598 ◽  
Author(s):  
Dan Tao ◽  
Jinbin Cao ◽  
Roberto Battiston ◽  
Liuyuan Li ◽  
Yuduan Ma ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Plasma Density ◽  
Spatial Variations ◽  
Asymmetric Structure ◽  
Electron Content ◽  
Total Electron ◽  
Significant Evidence ◽  
Demeter Satellite ◽  
Global Ionosphere Map ◽  
Geomagnetic Activities

Abstract. In this paper, we report significant evidence for preseismic ionospheric anomalies in total electron content (TEC) of the global ionosphere map (GIM) and plasma density appearing on day 2 before the 17 July 2006 M7.7 south of Java earthquake. After distinguishing other anomalies related to the geomagnetic activities, we found a temporal precursor around the epicenter on day 2 before the earthquake (15 July 2006), which agrees well with the spatial variations in latitude–longitude–time (LLT) maps. Meanwhile, the sequences of latitude–time–TEC (LTT) plots reveal that the TECs on epicenter side anomalously decrease and lead to an anomalous asymmetric structure with respect to the magnetic equator in the daytime from day 2 before the earthquake. This anomalous asymmetric structure disappears after the earthquake. To further confirm these anomalies, we studied the plasma data from DEMETER satellite in the earthquake preparation zone (2046.4 km in radius) during the period from day 45 before to day 10 after the earthquake, and also found that the densities of both electron and total ion in the daytime significantly increase on day 2 before the earthquake. Very interestingly, O+ density increases significantly and H+ density decreases, while He+ remains relatively stable. These results indicate that there exists a distinct preseismic signal (preseismic ionospheric anomaly) over the epicenter.

scholarly journals The effect of the ionosphere on ultra-low-frequency radio-interferometric observations

2018 ◽  
Vol 615 ◽  
pp. A179 ◽  
Author(s):  
F. de Gasperin ◽  
M. Mevius ◽  
D. A. Rafferty ◽  
H. T. Intema ◽  
R. A. Fallows
Keyword(s):  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Systematic Errors ◽  
Electron Content ◽  
Satellite Measurements ◽  
Third Order ◽  
Low Frequencies ◽  
Total Electron ◽  
Main Driver ◽  
Systematic Effects

Context. The ionosphere is the main driver of a series of systematic effects that limit our ability to explore the low-frequency (<1 GHz) sky with radio interferometers. Its effects become increasingly important towards lower frequencies and are particularly hard to calibrate in the low signal-to-noise ratio (S/N) regime in which low-frequency telescopes operate. Aims. In this paper we characterise and quantify the effect of ionospheric-induced systematic errors on astronomical interferometric radio observations at ultra-low frequencies (<100 MHz). We also provide guidelines for observations and data reduction at these frequencies with the LOw Frequency ARray (LOFAR) and future instruments such as the Square Kilometre Array (SKA). Methods. We derive the expected systematic error induced by the ionosphere. We compare our predictions with data from the Low Band Antenna (LBA) system of LOFAR. Results. We show that we can isolate the ionospheric effect in LOFAR LBA data and that our results are compatible with satellite measurements, providing an independent way to measure the ionospheric total electron content (TEC). We show how the ionosphere also corrupts the correlated amplitudes through scintillations. We report values of the ionospheric structure function in line with the literature. Conclusions. The systematic errors on the phases of LOFAR LBA data can be accurately modelled as a sum of four effects (clock, ionosphere first, second, and third order). This greatly reduces the number of required calibration parameters, and therefore enables new efficient calibration strategies.

scholarly journals DETECTING IONOSPHERIC ANOMALIES ASSOCIATED WITH THREE JAPAN MIYAKO EARTHQUAKES TO SHOW THEIR CORRELATIONS AND ASSOCIATED EARTHQUAKE-INDUCED TSUNAMIS

2016 ◽  
Vol 42 (1) ◽  
pp. 7-15 ◽  
Author(s):  
Lin Jyh-Woei
Keyword(s):  
Principal Component Analysis ◽  
Principal Component ◽  
Electron Content ◽  
Mathematical Tool ◽  
Two Dimensional ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Duration Time ◽  
Close Proximity ◽  
A Tec

This study employed two-dimensional principal component analysis (2DPCA) for the detection of anomalies in the two-dimensional ionospheric total electron content (TEC) associated with Japan three earthquakes and earthquake-induced tsunamis. From 04:40 to 04:50 (UTC) on February 15th, first TEC precursor was detected over the epicentre of the 16 February quake with the duration time of at least 10 minutes. A weak TEC anomaly associated with an earthquake-induced tsunami was also detected from 23:15 to 23:20 (UTC) on 16 February with the duration time of at least 5 minutes. An additional earthquake (Mw = 6.3) occurred in Miyako in the vicinity of the first earthquake. Second TEC precursor to the 20 February Miyako earthquake was recorded over the epicentre between 10:20 and 10:30 (UTC) on 19 February with the duration time of at least 10 minutes. A supplemental earthquake occurred (Mw = 6.1) as well in Miyako in the vicinity of the first earthquake. A TEC precursor to the 21 February Miyako earthquake was recorded over the epicentre between 04:15 and 04:25 (UTC) on 20 February with the duration time of at least 10 minutes. The three Miyako earthquakes presented similar anomalies and duration time in the TEC fluctuations, due largely to similarities in the magnitudes of the largest principal eigenvalues and the close proximity of the epicentres. Our results led to the reasonable confirmation that the very weak TEC anomaly following the Miyako earthquake on 16 February was associated with the earthquake-induced tsunami. 2DPCA is a useful mathematical tool for the monitoring of anomalous ionospheric fluctuations for use in the early warning of weak tsunamis.

scholarly journals ULF wave effects on high frequency signal propagation through the ionosphere

2009 ◽  
Vol 27 (7) ◽  
pp. 2779-2788 ◽  
Author(s):  
C. L. Waters ◽  
S. P. Cox
Keyword(s):  
High Frequency ◽  
Time Delays ◽  
Low Frequency ◽  
Signal Propagation ◽  
Temporal Variations ◽  
Electron Content ◽  
High Frequency Signal ◽  
Total Electron ◽  
Near Earth Space ◽  
Ulf Wave

Abstract. Variations in the total electron content (TEC) of the ionosphere alter the propagation characteristics of EM radiation for frequencies above a few megahertz (MHz). Spatial and temporal variations of the ionosphere TEC influence highly sensitive, ground based spatial measurements such as those used in radio astronomy and Global Positioning System (GPS) applications. In this paper we estimate the magnitudes of the changes in TEC and the time delays of high frequency signals introduced by variations in the ionosphere electron density caused by the natural spectrum of ultra-low frequency (ULF) wave activity that originates in near-Earth space. The time delays and associated phase shifts depend on the frequency, spatial structure and amplitude of the ULF waves.

scholarly journals The very low-frequency transmitter radio wave anomalies related to the 2010 Ms 7.1 Yushu earthquake observed by the DEMETER satellite and the possible mechanism

2020 ◽  
Vol 38 (5) ◽  
pp. 969-981
Author(s):  
Shufan Zhao ◽  
XuHui Shen ◽  
Zeren Zhima ◽  
Chen Zhou
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Satellite Observation ◽  
Low Earth Orbit ◽  
Electron Content ◽  
Yushu Earthquake ◽  
Total Electron ◽  
Very Low Frequency

Abstract. Earthquakes may disturb the lower ionosphere through various coupling mechanisms during the seismogenic and coseismic periods. The VLF (very low-frequency) signal radiated from ground-based transmitters will be affected when it penetrates the disturbed ionosphere above the epicenter area, and this anomaly can be recorded by low-Earth orbit satellites under certain conditions. In this paper, the temporal and spatial variation of the signal-to-noise ratio (SNR) of the VLF transmitter signal in the ionosphere over the epicenter of 2010 Yushu Ms 7.1 earthquake in China is analyzed using DEMETER (Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions) satellite observation. The results show that SNR over the epicenter of the Yushu earthquake especially in the southwestern region decreased (or dropped) before the main shock, and a GPS–TEC (Global Positioning System; total electron content) anomaly accompanied, which implies that the decrease in SNR might be caused by the enhancement of TEC. A full-wave method is used to study the mechanism of the change in SNR before the earthquake. The simulated results show SNR does not always decrease before an earthquake. When the electron density in the lower ionosphere increases by 3 times, the electric field will decrease about 2 dB, indicating that the disturbed-electric-field decrease of 20 % compared with the original electric field and vice versa. It can be concluded that the variation of electron density before earthquakes may be one of the important factors influencing the variation of SNR.

Sign in / Sign up

Export Citation Format

Share Document