Results 141 to 150 of about 3,051 (167)

Doppler Frequency Shifts Associated With the 18 September 2022 M6.8 Taitung Earthquake Observed by Local CW‐HF Doppler Sounding Systems in Taiwan

Journal of Geophysical Research: Space Physics
Abstract Doppler frequency shifts (DFSs) recorded by local continuous wave‐high frequency (CW‐HF) Doppler sounding systems have been used to study seismo‐traveling ionospheric disturbances (STIDs) triggered by seismic waves of M  ≥ 5.5 earthquakes in the Taiwan vicinity ...
Jann‐Yenq Liu, Tzu‐Hsun Kao, Yao‐Chun Chen, Jaroslav Chum, Wen‐Yen Chang, Bor‐Shouh Huang, Jaroslav Urbář, Katsumi Hattori, Yu‐Xiang Zhao, I.‐Ching Yang, Cheng‐Hao Lu, Yu‐Chi Chang   +11 more
openaire   +4 more sources

Identification of Acoustic Wave Signatures in the Ionosphere From Conventional Surface Explosions Using MF/HF Doppler Sounding

Radio Science, 2022
AbstractWe present an experiment to detect one ton TNT‐equivalent chemical explosions using pulsed Doppler radar observations of isodensity layers in the ionospheric E region during two campaigns. The first campaign, conducted on 15 October 2019, produced potential detections of all three shots. The detections closely resemble the temporal and spectral
K. S. Obenberger, D. C. Bowman, E. Dao
openaire   +1 more source

Passive HF Doppler Radar for Oblique-Incidence Ionospheric Sounding

2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON), 2019
A multi-path multi-frequency passive HF Doppler radar for oblique-incidence sounding the ionosphere, that has been produced in collaboration between researchers at the Harbin Engineering University and V. N. Karazin Kharkiv National University, is briefly described.
Q. Guo, Y. Zheng, L. F. Chernogor, K. P. Garmash, V. T. Rozumenko   +4 more
openaire   +1 more source

Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales

Journal of Atmospheric and Solar-Terrestrial Physics, 2008
Abstract Compared to investigations of the influence of gravity and planetary waves on the ionosphere, the effects of infrasound (periods from about 0.01 s to several minutes) variations have not been studied very much in the last 20 years. Here we present some recent results on peculiar transient phenomena occurring at infrasound timescales, as ...
J. Chum, J. Laštovička, T. Šindelářová, D. Burešová, F. Hruška   +4 more
openaire   +1 more source

Estimation algorithm of Doppler shift and time delay in HF channel sounding

IEEE 2011 10th International Conference on Electronic Measurement & Instruments, 2011
Doppler shift and propagation time delay are important parameters that require measuring in HF channel sounding. For the purpose of exact measurement of Doppler shift and time delay of HF channel, a parameter estimation algorithm is proposed on the basis of digital pulse compression technique, which achieves precise estimation of Doppler shift and ...
null Liu Yueliang, null Jiang Yuzhong, null Jiang Wei, null Feng Yanqing   +3 more
openaire   +1 more source

Coherent-array HF Doppler sounding of traveling ionospheric disturbances: I. Basic technique

Journal of Atmospheric and Terrestrial Physics, 1989
Abstract We present an introduction to the use of phase-coherent, multi-receiver HF Doppier sounding arrays for measuring the horizontal velocity of traveling ionospheric disturbances (TID's). The point of departure is the theorem of Pfister (1971, J. atmos. terr. Phys .
A.R. Jacobson, R.C. Carlos
openaire   +1 more source

Long‐period oceanic rayleigh wave group velocity dispersion curve from HF Doppler sounding of the ionosphere

Journal of Geophysical Research: Space Physics, 1979
Earthquake‐generated Rayleigh waves excite shock waves at the surface of the earth which propagate upward nearly vertically through the atmosphere as infrasound. The HF Doppler sounder is a sensitive tool for detecting and recording these infrasounds at ionospheric heights.
K. Najita, P. C. Yuen
openaire   +1 more source

Model of the Long Island Sound outflow: Comparison with year-long HF radar and Doppler current observations

Continental Shelf Research, 2008
A three-dimensional primitive-equation model is used to simulate the Long Island Sound (LIS) outflow for a 1-year (2001) period. The model domain includes LIS and New York Bight (NYB). Tidal and wind forcing are included, and seasonal salinity and temperature variations are assimilated. The model results are validated with the HF radar, moored acoustic
Jenq-Chi Mau, Dong-Ping Wang, David S. Ullman, Daniel L. Codiga   +3 more
openaire   +1 more source

Coseismic ionospheric disturbances at multiple altitudes associated with the foreshock of Tohoku earthquake observed by HF Doppler sounding

2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), 2017
Many studies have reported that ionospheric disturbances occur after big earthquakes. One of the causes of these coseismic ionospheric disturbances (CIDs) is the infrasound wave excited by Rayleigh wave propagated on the ground from the epicenter. The infrasound wave propagates upward and produces CIDs.
Hiroyuki Nakata, Kazuto Takaboshi, Toshiaki Takano, Ichiro Tomizawa   +3 more
openaire   +1 more source

Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations

Journal of Geophysical Research: Oceans, 2004
Surface current (HF radar) and velocity profile observations, obtained as part of the Front‐Resolving Observational Network with Telemetry (FRONT) project over an approximately 2‐year period, are used to describe the seasonal variability of a coastal jet in the Long Island Sound outflow region.
D. S. Ullman, D. L. Codiga
openaire   +1 more source