scholarly journals The LAI Coupling Associated with the M6 Luxian Earthquake in China on 16 September 2021

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1621
Author(s):  
Chieh-Hung Chen ◽  
Yang-Yi Sun ◽  
Kai Lin ◽  
Jing Liu ◽  
Yali Wang ◽  
...  
Keyword(s):  
Frequency Band ◽  
Atmospheric Pressure ◽  
Low Frequency ◽  
Electron Content ◽  
Ground Vibrations ◽  
Broadband Seismometer ◽  
Total Electron ◽  
Acoustic Gravity Waves ◽  
Micro Cracks ◽  
Vertical Electric Field

Periodic signals replaced noise that was found in continuous seismic data, particularly in the nighttime, from the broadband seismometer at the MVP-LAI (monitoring vibrations and perturbations in the lithosphere, atmosphere and ionosphere) system before the occurrence of the Luxian earthquake on 16 September 2021. A short distance of ~150 km between the MVP-LAI system and the epicenter of the Luxian earthquake suggests the periodic singles as promising seismo-phenomena, due to that the radius of the earthquake preparation zone is ~380 km for an M6 event. Integration of geophysical parameters, including atmospheric pressure, vertical electric field, radon concentration, groundwater level and precipitation, at the MVP-LAI system provides an excellent opportunity for studying the seismo-LAI coupling associated with the Luxian earthquake. Analytical results show that ground vibrations, atmospheric pressure and total electron content varied from ~10−3 to ~10−2 Hz before the Luxian earthquake. The seismo-LAI coupling in the relatively low frequency band (~10−3 Hz) can be referred to as the acoustic-gravity waves triggered by the amplified ground vibrations. In contrast, the seismo-LAI coupling in a relatively high frequency band (~10−2 Hz) would be caused by micro-cracks and/or the high-mode natural frequency that further drives changes of TEC due to the atmospheric resonance.

scholarly journals Isolated ionospheric disturbances as deduced from global GPS network

2004 ◽  
Vol 22 (1) ◽  
pp. 47-62 ◽  
Author(s):  
E. L. Afraimovich ◽  
E. I. Astafieva ◽  
S. V. Voyeikov
Keyword(s):  
Total Electron Content ◽  
Acoustic Waves ◽  
Mean Value ◽  
Global Network ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Radio Science ◽  
Acoustic Gravity Waves ◽  
Medium Scale

Abstract. We investigate an unusual class of medium-scale traveling ionospheric disturbances of the nonwave type, isolated ionospheric disturbances (IIDs) that manifest themselves in total electron content (TEC) variations in the form of single aperiodic negative TEC disturbances of a duration of about 10min (the total electron content spikes, TECS). The data were obtained using the technology of global detection of ionospheric disturbances using measurements of TEC variations from a global network of receivers of the GPS. For the first time, we present the TECS morphology for 170 days in 1998–2001. The total number of TEC series, with a duration of each series of about 2.3h (2h18m), exceeded 850000. It was found that TECS are observed in no more than 1–2% of the total number of TEC series mainly in the nighttime in the spring and autumn periods. The TECS amplitude exceeds the mean value of the "background" TEC variation amplitude by a factor of 5–10 as a minimum. TECS represent a local phenomenon with a typical radius of spatial correlation not larger than 500km. The IID-induced TEC variations are similar in their amplitude, form and duration to the TEC response to shock-acoustic waves (SAW) generated during rocket launchings and earthquakes. However, the IID propagation velocity is less than the SAW velocity (800–1000m/s) and are most likely to correspond to the velocity of background medium-scale acoustic-gravity waves, on the order of 100–200m/s. Key words. Ionosphere (ionospheric irregularities, instruments and techniques) - Radio science (ionospheric propagation)

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 Large air pressure changes triggered by P-SV ground motion in a cave in northern Taiwan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chieh-Hung Chen ◽  
Yang-Yi Sun ◽  
Li-Ching Lin ◽  
Peng Han ◽  
Huai-Zhong Yu ◽  
...  
Keyword(s):  
Phase Angle ◽  
Air Pressure ◽  
Electron Content ◽  
Confined Space ◽  
Ground Vibrations ◽  
Total Electron ◽  
Causal Mechanisms ◽  
Unusual Phenomenon ◽  
Vertical Ground ◽  
Pressure Changes

AbstractAcoustic-gravity waves are generally considered to be one of the major factors that drive changes of the total electron content in the ionosphere. However, causal mechanisms of couplings between sources in the lithosphere and responses in the atmosphere and the ionosphere are not fully understood, yet. A barometer in the cave of the SBCB station records an unusual phenomenon of larger amplitudes in air pressure changes inside than those at the Xinwu station (outside). Accordingly, the comparison between the recorded data at the SBCB and Xinwu station can drive investigations of potential sources of the unusual phenomenon. Analytical results of phase angle differences reveal that the air pressure outside the cave at the Xinwu station often leads air pressure changes inside at the SBCB station at relatively low frequency bands. In contrast, the larger pressure changes at frequencies >  ~ 5 × 10–4 Hz inside the cave at the SBCB station lead smaller changes outside at the Xinwu station. To expose causal mechanisms of the unusual phenomenon, continuous seismic waveforms are further conducted for examination. When the horizontal and vertical ground velocities of ground vibrations yield a difference in the phase angle close to 90°, coherence values between the air pressure changes and ground vibrations become large. This suggests that the pressure-shear vertical ground vibrations can drive air pressure changes. Meanwhile, the results shed light on investigating the existence of acoustic waves near the Earth’s surface using a partially confined space underground due to that the assumptions of the waves can propagate upward into the atmosphere driving changes in the ionosphere.

scholarly journals Influence of meteorological storms on ionospheric parameters in the Baltic region in 2010

2016 ◽  
Vol 2 (2) ◽  
pp. 77-81 ◽  
Author(s):  
Иван Карпов ◽  
Ivan Karpov ◽  
Ольга Борчевкина ◽  
Olga Borchevkina ◽  
Руслан Дадашев ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Critical Frequency ◽  
Diurnal Variations ◽  
Electron Content ◽  
Atmospheric Parameters ◽  
Baltic Region ◽  
Total Electron ◽  
Meteorological Effect ◽  
Kaliningrad Region ◽  
The Baltic

The paper presents observations of atmospheric and ionospheric parameters during strong meteorological disturbances (storms) in the Kaliningrad region. The critical frequency of the F2 layer (foF2) and the total electron content (TEC) were observed at the station Kaliningrad (20 °E, 54.20 °N). Atmospheric pressure and wind were taken to be the atmospheric parameters under study. The analysis of ionospheric observations has shown that during meteorological storms the amplitude of diurnal variations in TEC decreases to 50 %; and in foF2, to 15 % as compared to quiet days. The revealed changes in ionospheric conditions during meteorological storms are regularly registered and represent a characteristic feature of the meteorological effect on the ionosphere.

scholarly journals Influence of meteorological storms on ionospheric parameters in Baltic region in 2010

2016 ◽  
Vol 2 (2) ◽  
pp. 64-68 ◽  
Author(s):  
Иван Карпов ◽  
Ivan Karpov ◽  
Ольга Борчевкина ◽  
Olga Borchevkina ◽  
Руслан Дадашев ◽  
...  
Keyword(s):  
Characteristic Feature ◽  
Total Electron Content ◽  
Atmospheric Pressure ◽  
Critical Frequency ◽  
Diurnal Variations ◽  
Electron Content ◽  
Atmospheric Parameters ◽  
Baltic Region ◽  
Total Electron ◽  
Kaliningrad Region

The paper presents observations of atmospheric and ionospheric parameters during strong meteorological disturbances (storms) in the Kaliningrad region. The critical frequency of the F2 layer (foF2) and the total electron content (TEC) were observed at the station Kaliningrad (20 °E, 54.20 °N). Atmospheric pressure and wind were taken to be the atmospheric parameters under study. The analysis of ionospheric observations has shown that during meteorological storms the amplitude of diurnal variations in TEC decreases to 50 %; and in foF2, to 15 % as compared to quiet days. The revealed changes in ionospheric conditions during meteorological storms are regularly registered and represent a characteristic feature of the meteo-rological effect on the ionosphere.

scholarly journals The Propagation of Tsunami-Generated Acoustic–Gravity Waves in the Atmosphere

2016 ◽  
Vol 73 (8) ◽  
pp. 3025-3036 ◽  
Author(s):  
Yue Wu ◽  
Stefan G. Llewellyn Smith ◽  
James W. Rottman ◽  
Dave Broutman ◽  
Jean-Bernard H. Minster
Keyword(s):  
Gravity Waves ◽  
Lower Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
Realistic Case ◽  
Acoustic Gravity Waves ◽  
Total Transmission ◽  
2004 Sumatra Tsunami ◽  
Atmospheric Profile ◽  
The Difference

Abstract Tsunami-generated acoustic–gravity waves have been observed to propagate in the atmosphere up to the ionosphere, where they have an impact on the total electron content. The authors simulate numerically the propagation of two-dimensional linear acoustic–gravity waves in an atmosphere with vertically varying stratification and horizontal background winds. The authors’ goal is to compare the difference in how much energy reaches the lower ionosphere up to an altitude of 180 km, where the atmosphere is assumed to be anelastic or fully compressible. The authors consider three specific atmospheric cases: a uniformly stratified atmosphere without winds, an idealized case with a wind jet, and a realistic case with an atmospheric profile corresponding to the 2004 Sumatra tsunami. Results show that for the last two cases, the number and height of turning points are different for the anelastic and compressible assumptions, and the net result is that compressibility enhances the total transmission of energy through the whole atmosphere.

Worldwide GNSS ionospheric response of the magnitude 8.8 2010 Chilean earthquake and tsunami: a revisit

2021 ◽  
Author(s):  
Lucie Rolland ◽  
Edhah Munaibari ◽  
Florian Zedek ◽  
Pierre Sakic ◽  
Anthony Sladen ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Electron Content ◽  
Total Electron ◽  
Peak Displacement ◽  
Ionospheric Response ◽  
Acoustic Gravity Waves ◽  
Depth Analysis ◽  
Ocean Atmosphere ◽  
Gnss Network ◽  
The Impact

<p>The third-largest earthquake of this 21st century ruptured the Andes subduction zone offshore of the Maule region in central Chile on 27 February 2010, in the middle of the night (3:35 am local time). This huge event triggered strong and destructive seismic motions accompanied by a devastating local tsunami and a significant transpacific tsunami. We investigate the impact of this earthquake on the ionosphere using Global Positioning System (GPS) satellites and other Global Navigation Satellite System (GNSS) data. Investigations related to ionospheric disturbances induced by mega-earthquakes accelerated with the Mw9.0 Tohoku earthquake of March 2011. The worldwide GNSS network, including the exceptionally dense Japanese GNSS network, observed a complex ionospheric response. With a better understanding of the physical mechanisms behind it and a more exhaustive data collection, we revisit the ionospheric wavefield triggered by the Mw8.8 Chile earthquake and tsunami.</p><p>When a large underwater earthquake occurs, the sudden shaking of an extended region of the sea-floor immediately transfers energy to the water column and the air above through an efficient solid-ocean-atmosphere coupling mechanism. The earthquake at depth thus excites seismic and tsunami waves in the ocean and acoustic-gravity waves in the atmosphere. In the lower frequency range (< 20 mHz), these atmospheric waves can propagate to the upper atmosphere, which shakes the ionosphere. During propagation in the rarefying atmosphere, the wave amplitude drastically increases by about four orders of magnitude. Typically, a tsunami with a height of the order of a meter in an open ocean puts the ionosphere into motion with peak displacement exceeding a kilometer at about 200 km of altitude. The shaken charged particles of the ionosphere plasma eventually induce fluctuations of propagation delays in radio signals, such as those emitted by GPS and GNSS satellites. We convert GNSS measurements into Total Electron Content (TEC) variations to study the ionospheric imprint.</p><p>We revisit the Maule earthquake with an in-depth analysis of the TEC data derived from a worldwide collection of GNSS records. We also compare the observed ionospheric responses to ground or ocean motions derived from high-frequency GNSS receiver data recorded onshore and offshore. Doing so, we further characterize the filtering effect of the atmosphere on acoustic-gravity waves driven from the Earth’s surface. Finally, we use numerical tools specifically developed to investigate the complex seismo-ionospheric wavefield triggered by large seismic ruptures. We focus on the resonant part of the seismo-acoustic response and the tsunami-induced ionospheric response and link them to waveguides in the solid-ocean-atmosphere system. This revisit intends ultimately to shed new and independent light on the 2010 Maule mega-earthquake rupture itself.</p>

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 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.

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