Internal gravity waves deduced from the HF Doppler data during the April 19, 1958, solar eclipse

Ichinose, Takumi; Ogawa, Teiichiro

doi:10.1029/ja081i013p02401

Cited by 16 publications

(9 citation statements)

References 10 publications

(2 reference statements)

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“…As the lunar shadow sweeps at supersonic speed across the Earth, the cooling spot acts as a continuous source of gravity waves that build up into a bow wave [ Chimonas and Hines , 1970]. When the wave propagates upward and passes through the ionosphere, it produces wavelike variation in the stratified electron density and may cause the HF Doppler shifts in the radio waves propagating through this region [ Ichinose and Ogawa , 1976]. The wavelike fluctuation with 30 min period in the maximum electron density was clearly observed by the ionosonde in Wuhan, and oscillations with 48 and 60 min periods were also discovered in the DFS spectra of the oblique incidence waves received in Suzhou and Huaian, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The first recorded atmospheric gravity waves (AGS) in the ionosphere induced by solar eclipse were associated with the periodic electron content fluctuation on 7 March 1970 [ Davis and Da Rosa , 1970]. In this event, the gravity waves were detected in the virtual/true height change of F region [ Butcher , 1973; Cheng et al , 1992; Altadill et al , 2001; Jakowski et al , 2008] and in the high‐frequency (HF) Doppler data [ Ichinose and Ogawa , 1976; Hanuise et al , 1982; Jones et al , 2004].…”

Section: Introductionmentioning

confidence: 99%

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Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

et al. 2010

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[1] The sporadic E (Es) frequently emerging in midlatitude during summer is a very special layer in the ionosphere, and its formation mechanism is different to from that of other layers. The total solar eclipse of 22 July 2009 provided a very unique opportunity to study the relationship of Es and solar radiation. During the solar eclipse day and the days before and after, the vertical incidence ionosonde was located in Wuhan to record the ionograms for this event. Two oblique incidence high-frequency radio systems were used to record the waves from Wuhan to Suzhou and from Wuhan to Huaian. The enhancement of Es during the eclipse period was observed in the vertical and oblique incidence ionograms. The quasi-periodic fluctuations in the critical frequency and Doppler frequency shift curves indicated the possible existence of the gravity waves, which may be responsible for the Es enhancement. However, we find that the enhancement occurred earlier than the appearance of gravity waves and consider that there may be other mechanisms which contribute to the observed enhancement in the ionosphere. A hypothesis is put forward that the cooling effect of the lunar shadow induced powerful airflow from the northern and southern limits of the shadow toward its center, which accelerated the irregularities in Es to produce the large-scale Doppler shift in the reflected waves and form the meridional windshear. Both the windshear and the gravity waves may affect the Es layer and increase the electron concentration. Many observed phenomena are in accordance with this.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

et al. 2010

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“…The internal gravity waves seem to affect the electron density in the F layer. (Ichinose, & Ogawa, 1976) 2…”

Section: Solar Phnomenamentioning

confidence: 99%

Fifty Years of HF Doppler Observations

Ogawa¹,

Ichinose²

2009

Data Sci. J.

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“…Ichinose and Ogawa (1974) examined the vertical motion of the ionosphere using HFD observations and showed that the derivative of the horizontal component of the geomagnetic eld varied in phase with the Doppler frequency during a sudden commencement (SC). Concerning the internal gravity waves caused by a solar eclipse, Ichinose and Ogawa (1976) showed that uctuations with a period of 22 min appeared on the day of a solar eclipse. The University of Electro-Communications (UEC) and the Radio Research Laboratory (RRL, now the National Institute of Information and Communications Technology) have also promoted HFD sounding in Japan.…”

Section: Introductionmentioning

confidence: 99%

Software-Defined-Radio Based HF Doppler Receiving System

Nakata

Nozaki

Oki

et al. 2021

Preprint

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High-frequency Doppler (HFD) sounding is a major remote sensing technique for monitoring the ionosphere. Conventional systems for HFDs mainly utilize analog circuits. However, existing analog systems have become difficult to maintain as the number of individuals adept at working with analog circuits has declined. To solve this problem, we developed an alternate HFD receiver system based on digital signal processing. The software-defined radio (SDR) technique enables the receiver to be set up without the knowledge of analog circuit devices. This approach also downsizes the system and reduces costs. A highly stabilized radio system for both the transmitter and receiver is necessary for stable long-term observations of various phenomena in the ionosphere. The global positioning system disciplined oscillator with an accuracy of H compensates for the frequency stability required by the new receiving system. In the new system, four frequencies are received and signal-processed simultaneously. The dynamic range of the new system is wider (> 130 dB) than that of the conventional system. The signal-to-noise ratio significantly improved by 20 dB. The new digital system enables radio waves to be received with much smaller amplitudes at four different frequencies. New digital receivers have been installed at some of the stations in the HFD observation network in Japan and have already captured various ionospheric phenomena, including medium-scale traveling ionospheric disturbances and sudden commencement induced electric field fluctuations, which indicates the feasibility of SDR for actual ionospheric observations. The new digital receiver is simple, inexpensive, and small in size, which makes it easy to deploy new receiving stations in Japan and elsewhere. These advantages of the new system will help drive the construction of a wide HFD observation network.

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Internal gravity waves deduced from the HF Doppler data during the April 19, 1958, solar eclipse

Cited by 16 publications

References 10 publications

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

Enhancement and HF Doppler observations of sporadic‐E during the solar eclipse of 22 July 2009

Fifty Years of HF Doppler Observations

Software-Defined-Radio Based HF Doppler Receiving System

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