Scintillation of VHF/UHF and <i>L</i> band satellite signals at Guam

Paulson, M. R.

doi:10.1029/rs016i005p00877

Cited by 12 publications

(15 citation statements)

References 5 publications

(1 reference statement)

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“…At the longitudes where the magnetic declination angle is small, like Southeast Asia to India, ESF and plasma bubbles tend to be active around the equinoctial seasons (Maruyama and Matuura, 1984;Burke et al, 2004a, b). Similar equinoctial occurrence maxima of gigahertz equatorial scintillations were reported by Paulson (1981) and Fang and Liu (1983).…”

Section: Drift Velocity and Spatial Structuresupporting

confidence: 70%

Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

Maruyama

Kawamura

2006

Ann. Geophys.

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Abstract.A transequatorial radio-wave propagation experiment at shortwave frequencies (HF-TEP) was done between Shepparton, Australia, and Oarai, Japan, using the radio broadcasting signals of Radio Australia. The receiving facility at Oarai was capable of direction finding based on the MUSIC (Multiple Signal Classification) algorithm. The results were plotted in azimuth-time diagrams (AT plots). During the daytime, the propagation path was close to the great circle connecting Shepparton and Oarai, thus forming a single line in the AT plots. After sunset, off-great-circle paths, or satellite traces in the AT plot, often appeared abruptly to the west and gradually returned to the great circle direction. However, there were very few signals across the great circle to the east. The off-great-circle propagation was very similar to that previously reported and was attributed to reflection by an ionospheric structure near the equator. From the rate of change in the direction, we estimated the drift velocity of the structure to range mostly from 100 to 300 m/s eastward. Multiple instances of off-great-circle propagation with a quasi-periodicity were often observed and their spatial distance in the east-west direction was within the range of large-scale traveling ionospheric disturbances (LS-TIDs). Off-great-circle propagation events were frequently observed in the equinox seasons. Because there were many morphological similarities, the events were attributed to the onset of equatorial plasma bubbles.

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Section: Drift Velocity and Spatial Structuresupporting

confidence: 70%

Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

Maruyama

Kawamura

2006

Ann. Geophys.

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“…Besides in situ satellite measurements mentioned in section 2.1, time‐continuous measurements of scintillations have been made from GUM, using transmissions from the geostationary INTELSAT [ Taur , ] and two MARISAT [ Paulson , ] satellites. Beacon signal frequencies were 4/6 GHz from INTELSAT and 257.55 MHz and 1.542 GHz from MARISAT.…”

Section: Esf Results: Satellite Measurementsmentioning

confidence: 99%

“…Beacon signal frequencies were 4/6 GHz from INTELSAT and 257.55 MHz and 1.542 GHz from MARISAT. The POFs for INTELSAT (POF INTELSAT ) and MARISAT (POF MARISAT ) are not presented here, but they can be seen in Tsunoda [, Figure ], Taur [, Figure 10], or Paulson [, Figure ]. The elevation angle to INTELSAT was 58°, and those to the two MARISAT satellites were 10° to the west to the Indian Ocean satellite and 50° to the east to the Pacific Ocean satellite.…”

Section: Esf Results: Satellite Measurementsmentioning

confidence: 99%

Effects of tidal forcing, conductivity gradient, and active seeding on the climatology of equatorial spread F over Kwajalein

Tsunoda

Nguyen

2015

JGR Space Physics

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Plasma structure in nighttime equatorial F layer, referred to as equatorial spread F (ESF), displays climatology whose seasonal variation depends on longitude. At longitudes where ESF favors equinoxes, times when maxima occur can be predicted in terms of the day of year, when E region sunset is simultaneous in conjugate hemispheres (i.e., "sunset nodes"). Aside from occurrences around equinoxes, there are only three longitudes where ESF also occurs during a solstice; one is the central Pacific region. Here ESF activity is strong during the June solstice, when solar activity is high. To understand this puzzling behavior, ESF climatology over the Kwajalein Atoll was compared with properties of the postsunset rise (PSSR) of the F layer and seeding activity in the troposphere. The key findings are as follows: (1) Maxima in PSSR velocity (V PSSR ) are better aligned with equinoxes than with sunset nodes; hence, seasonal pattern of V PSSR , not only sunset nodes, should be included in interpretation of ESF climatology. (2) The source of V PSSR during solstice appears to differ from that during equinoxes. (3) Equinoctial maxima in V PSSR could be related to a semiannual variation in equatorial electrojet strength and its contribution to polarization of the F region dynamo current. (4) Enhanced V PSSR during the June solstice is interpreted in terms of tidal forcing with a wave number of 2. (5) Displacements of maxima in ESF climatology from maxima in V PSSR are shown to be consistent with deep convective activity.

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“…Furthermore, it would seem that the statistics for these events should mimic those of intense scintillation observed at a tropical Pacific site such as Guam. However, the studies performed there by Taur [ 1973] and Paulson [1981] show a minimum in occurrence frequency of gigahertz scintillation in the summer months.…”

Section: Mid-latitude F Regionmentioning

confidence: 99%

Turbulent upwelling of the mid‐latitude ionosphere: 2. Theoretical framework

Kelley¹,

Fukao²

1991

J. Geophys. Res.

175

174

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In a companion paper, data from the MU radar have been presented which show that during sunspot minimum conditions in Japan the mid‐latitude ionosphere is sometimes characterized by regions of rapid and turbulent upwelling. In this paper we explore possible mechanisms for these events. The most likely process seems to be the instability of the equilibrium which occurs when the mid‐latitude plasma is supported against gravity either by an eastward electric field component or by a southward neutral wind, as was proposed by Perkins (1973). We show, for example, that the growth rate determined by Perkins is considerably higher in sunspot minimum conditions than at sunspot maximum for comparable altitudes of the ionospheric F layer. The growth rate is not very large, however, and we argue here that the observed structures must evolve from preexisting undulations of the bottomside of the F region which are generated by gravity waves. That is, the gravity waves create finite amplitude structures which are amplified by the plasma instability. An intriguing feature of the gravity wave role in this process is that the echoing patches detected by the MU radar and the height bands detected by the Arecibo radar, which we believe to be related phenomena, all seem to propagate to the west. This is the same direction reported for the angle‐of‐arrival measurements of classic mid‐latitude spread F by a number of researchers using ionosonde techniques. Since the MU radar detects the upwelling regions from nonthermal 3‐m irregularities there must be mechanism to create such tracers. We propose that secondary structures are created at intermediate scales via the E×B instability operating on the dome of the upwelling structure and by the neutral wind‐driven process on either the west or the east wall of the structure, depending on the direction of the zonal wind. The 3‐m waves are then created in a cascade process which brings energy into a range of k space in which the structures are linearly damped. Finally, we discuss the fine structure of the echoing patches and suggest several plausible mechanisms, two of which involve E region coupling and one which deals with the vertical structure of the gravity wave seeding process.

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Scintillation of VHF/UHF and L band satellite signals at Guam

Cited by 12 publications

References 5 publications

Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

Effects of tidal forcing, conductivity gradient, and active seeding on the climatology of equatorial spread F over Kwajalein

Turbulent upwelling of the mid‐latitude ionosphere: 2. Theoretical framework

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