Theory of gravity wave emission from moving sources in the upper atmosphere

Katō, Susumu; Kawakami, Takato; John, Dennis St

doi:10.1016/0021-9169(77)90067-8

Cited by 17 publications

(13 citation statements)

References 7 publications

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“…The resultant wave is composition of all possible waves generated at every point, and it is difficult to specify what kinds of waves finally remain at a later time. In particular, the flow velocity for v = 600 m/s case exceeds the sonic speed at some altitudes where acoustic waves (bow waves) are emitted instead of gravity waves, giving a stronger oscillation near the heating region (Kato et al, 1977;Kato, 1980). Strong and sudden pressure jump occurs in front of the heating region, and sudden decrease behind the heating region, which results in a large upward and downward motion near the arc.…”

Section: Discussionmentioning

confidence: 99%

“…Acoustic-gravity waves radiated from moving sources were investigated by Kato et al (1977) and Kato (1980). They employed a linear analysis to study gravity wave emission from a moving line source as well as a moving point source in the upper atmosphere.…”

Section: Discussionmentioning

confidence: 99%

“…Subsonic, transonic, and supersonic cases for the moving sources were studied. It is noted that the studies of Kato et al (1977) and Kato (1980) are not able to give actual velocity fields because (1) a point source or a line source is assumed, (2) nature of the source is not specified, (3) linearity of the system, i.e., small amplitude is assumed, and (4) the realistic atmosphere is not included. Nonetheless, they successfully showed that when the speed of the source becomes closer to the sonic speed, the physical quantities jump suddenly as the source passes the observation point, indicating strong compression occurs in front of the moving source.…”

Section: Discussionmentioning

confidence: 99%

“…Figure 12 shows the dispersion diagram for acousticgravity waves. A linear analysis by Kato et al (1977) and by Kato (1980) shows that when the source moves at the supersonic speed (line a), acoustic-mode waves are radiated from the source. When the source speed is exactly the same as the sonic speed (line b), the Lamb wave is radiated.…”

Section: Discussionmentioning

confidence: 99%

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A two-dimensional simulation of thermospheric vertical winds in the vicinity of an auroral arc

Shinagawa

Oyama

2006

Earth Planet Sp

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The observations made by Fabry-Perot interferometers (FPIs), radars, and satellites have indicated that large vertical motion in the polar region is occasionally generated in the thermosphere associated with auroral activities. However, the behavior of the vertical wind is often very complicated, and the cause of the vertical wind has not been explained by auroral heating or by ion-neutral drag alone. It has been pointed out that a background horizontal flow is likely to significantly alter the dynamics of the neutral atmosphere near an auroral arc. Recent observations have also suggested that strong downward motion is generated in the vicinity of an auroral arc. To study the thermospheric dynamics near a local heating region embedded in a large-scale horizontal flow, a twodimensional numerical simulation of the thermospheric dynamics has been performed. It is found that interaction of local heating and strong horizontal flow could play an important role in generating vertical motion near an auroral arc. The simulation results indicate that for a horizontal wind speed larger than about 300 m/s, a steady wave-like structure of the neutral wind is formed within and downstream of the heated region. For a horizontal wind speed less than about 300 m/s, on the other hand, no significant vertical motion is generated outside the heated region. This process might account for at least some of the observed features of vertical motion within and outside an auroral arc.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A two-dimensional simulation of thermospheric vertical winds in the vicinity of an auroral arc

Shinagawa

Oyama

2006

Earth Planet Sp

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“…Swift [1973] showed that supersonic motion of the auroral electrojet could radiate auroral infrasonic waves. The effects of moving sources on the generation of AGWs have been investigated theoretically under the assumption that auroral arcs move at a subsonic speed [Kato et al, 1977].…”

Section: 543mentioning

confidence: 99%

Generation of atmospheric gravity waves associated with auroral activity in the polar F region

Oyama¹,

Ishii²,

Murayama³

et al. 2001

J. Geophys. Res.

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Changes in the D region associated with three recent solar eclipses in the South Pacific region

Kumar

Maurya

et al. 2016

JGR Space Physics

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We estimate D region changes due to 22 July 2009 total solar eclipse (SE), 13–14 November 2012 total SE, and 9–10 May 2013 annular SE, using VLF navigational transmitters signal observations at Suva, Fiji. The North West Cape (NWC) signal (19.8 kHz) showed an amplitude and phase decrease of 0.70 dB and 23° during November SE and 2.0 dB and 90° during May SE. The modeling using Long Wave Propagation Capability code for NWC‐Suva path during November and May SEs showed an increase in average D region reflection height (H′) and sharpness factor (β) by 0.6 and 0.5 km and 0.012 and 0.015 km−1, respectively. The July total SE for JJI‐Suva path showed an increase in H′ of 1.5 km and a decrease in β of 0.055 km−1. The decrease in the electron density calculated using SE time H′ and β is maximum for July total SE and minimum for May annular SE. The effective recombination coefficient estimated from the decay and recovery of signal phase associated with May annular SE was higher (27%) than normal daytime value 5.0 × 10−7 cm−3 s−1 and varied between 1.47 × 10−6 and 1.15 × 10−7 cm−3 s−1 in the altitude 70 to 80 km. Morlet wavelet analysis of signals amplitude shows strong wave‐like signatures (WLS) associated with three SEs with period ranging 24–66 min, but the intensity and duration of WLS show no clear dependence on SE magnitude and type. Apart from the cooling spot, the eclipse shadow can also generate WLS associated with atmospheric gravity waves.

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Theory of gravity wave emission from moving sources in the upper atmosphere

Cited by 17 publications

References 7 publications

A two-dimensional simulation of thermospheric vertical winds in the vicinity of an auroral arc

A two-dimensional simulation of thermospheric vertical winds in the vicinity of an auroral arc

Generation of atmospheric gravity waves associated with auroral activity in the polar F region

Changes in the D region associated with three recent solar eclipses in the South Pacific region

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