Detection of acoustic‐gravity waves in lower ionosphere by VLF radio waves

Nina, Aleksandra; Čadež, V. M.

doi:10.1002/grl.50931

Cited by 50 publications

(54 citation statements)

References 21 publications

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“…The previous studied have shown the solar terminator (ST) associated WLS of variable periods. Nina and Cadež [2013] using DHO, France, transmitter signal at 23.4 kHz recorded at Belgrade Serbia, reported WLS of period 1 s to 90 min during ST passes. Afraimovich [2008] reported GPS TEC oscillations with periods of about 1 h at 100 km altitude.…”

Section: Normal Day Wave-like Signaturesmentioning

confidence: 99%

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Maurya¹,

Phanikumar

Singh³

et al. 2014

JGR Space Physics

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We present first report on the periodic wave-like signatures (WLS) in the D region ionosphere during 22 July 2009 total solar eclipse using JJI, Japan, very low frequency (VLF) navigational transmitter signal (22.2 kHz) observations at stations, Allahabad, Varanasi and Nainital in Indian Sector, Busan in Korea, and Suva in Fiji. The signal amplitude increased on 22 July by about 6 and 7 dB at Allahabad and Varanasi and decreased by about 2.7, 3.5, and 0.5 dB at Nainital, Busan, and Suva, respectively, as compared to 24 July 2009 (normal day). The increase/decrease in the amplitude can be understood in terms of modal interference at the sites of modes converted at the discontinuity created by the eclipse intercepting the different transmitter-receiver great circle paths. The wavelet analysis shows the presence of WLS of period~16-40 min at stations under total eclipse and of period~30-80 min at stations under partial eclipse (~85-54% totality) with delay times between~50 and 100 min at different stations. The intensity of WLS was maximum for paths in the partially eclipsed region and minimum in the fully eclipsed region. The features of WLS on eclipse day seem almost similar to WLS observed in the nighttime of normal days (e.g., 24 July 2009). The WLS could be generated by sudden cutoff of the photo-ionization creating nighttime like conditions in the D region ionosphere and solar eclipse induced gravity waves coming to ionosphere from below and above. The present observations shed additional light on the current understanding of gravity waves induced D region ionospheric perturbations.

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Section: Normal Day Wave-like Signaturesmentioning

confidence: 99%

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Maurya¹,

Phanikumar

Singh³

et al. 2014

JGR Space Physics

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“…The daytime low ionospheric variations have the greatest affect on radio wave propagation at low (30 kHz -300 kHz), very low (3 kHz -30 kHz) and ultra low (0.3 kHz -3 kHz) frequency bands [11,12]. Prediction of such variations is important for the variety of reasons: remote sensing detection of narrow bipolar events in clouds [13], monitoring of acoustic and gravity waves in the atmosphere [6], and monitoring specific perturbations in the ionosphere that precede seismic activity [14] and tropical cyclones [15]. The parameters describing EM waves and characteristics of medium important for radio wave propagation are: the refractivity index and the electron plasma frequency, respectively.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric D-region temperature relaxation and its influences on radio signal propagation after solar X-flares occurrence

et al. 2015

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In this paper our attention is focused on relations between radio signal propagation characteristics and temperature changes in D-region after solar X-flare occurrence. We present temperature dependencies of electron plasma frequency, the parameter that describes medium conditions for propagation of an electromagnetic wave, and the refractive index which describes how this wave propagates. As an example for quantitative calculations based on obtained theoretical equations we choose the reaction of the D-region to the solar X-flare occurred on May 5 th , 2010. The ionospheric modelling is based on the experimental data obtained by low ionosphere observations using very low frequency radio signal.

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“…A possible reason for this phenomenon is that the high-frequency signal only reaches the lower ionosphere due to the viscous dissipation within the thermosphere which is inversely proportional to frequency. The acoustic waves or acoustic-gravity waves in lower ionosphere can also induce detectable disturbances (Choosakul et al, 2009;Watada and Kanamori, 2010;Nina andČadež, 2013). This explanation can be strengthened by the results: observed average velocities of high-frequency TIDs are basically larger than the low-frequency TIDs.…”

Section: Observations and Resultsmentioning

confidence: 89%

Traveling ionospheric disturbances triggered by the 2009 North Korean underground nuclear explosion

Zhang

Tang

2015

Ann. Geophys.

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Abstract. Underground nuclear explosions (UNEs) can induce acoustic-gravity waves, which disturb the ionosphere and initiate traveling ionospheric disturbances (TIDs). In this paper, we employ a multi-step and multi-order numerical difference method with dual-frequency GPS data to detect ionospheric disturbances triggered by the North Korean UNE on 25 May 2009. Several International GNSS Service (IGS) stations with different distances (400 to 1200 km) from the epicenter were chosen for the experiment. The results show that there are two types of disturbances in the ionospheric disturbance series: high-frequency TIDs with periods of approximately 1 to 2 min and low-frequency waves with period spectrums of 2 to 5 min. The observed TIDs are situated around the epicenter of the UNE, and show similar features, indicating the origin of the observed disturbances is the UNE event. According to the amplitudes, periods and average propagation velocities, the high-frequency and low-frequency TIDs can be attributed to the acoustic waves in the lower ionosphere and higher ionosphere, respectively.

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Detection of acoustic‐gravity waves in lower ionosphere by VLF radio waves

Cited by 50 publications

References 21 publications

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Low‐mid latitude D region ionospheric perturbations associated with 22 July 2009 total solar eclipse: Wave‐like signatures inferred from VLF observations

Ionospheric D-region temperature relaxation and its influences on radio signal propagation after solar X-flares occurrence

Traveling ionospheric disturbances triggered by the 2009 North Korean underground nuclear explosion

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