scholarly journals The ionosphere and radio interferometry

1997 ◽  
Vol 40 (4) ◽  
Author(s):  
T. A. Th. Spoelstra
Keyword(s):  
Gravity Waves ◽  
Daily Variation ◽  
Lower Thermosphere ◽  
Time Of Day ◽  
Ionospheric Disturbances ◽  
Frequency Of Occurrence ◽  
Radio Interferometry ◽  
Travelling Ionospheric Disturbances ◽  
Propagation Parameters ◽  
Definition Of

This paper reviews the effects of the ionosphere on radio astronomjcal observations, what we can learn about the ionosphere from radio interferometry, and a procedure to correct for these effects. This study analyzes the results obtained from observations of celestial point soUl.ces with the Westerbork Synthesis Radio Telescope, WSRT, in the Netherlands from the period 1970-1991. The main conc1usions are: 1) A1though seasona1 effects are c1ear, the occurrence and "strength" of ionospheric irregu1arities show no dependence on solar activity. 2) Assuming that the frequency of occurrence of ionospheric disturbances in Spring and Autumn are similar, Ihe "ionospheric" Winter starts on day 348 ± 3 and ali seasons last for three months. 3) Travelling ionospheric disturbances, TIDs, occur most frequently during daytime in Winter periods. 4) The propagation parameters of these travelling ionospheric irregularities and their periods indicate that these belong main1y to the c1ass of medium sca]e TIDs. 5) Radio interferometry is a powerful tool to locate irregularities causing scintillation and to determine their dimensions. 6) The occurrence of non-periodic irregu1arities is, however, not a function of time of day. 7) The daily variation in the amplitude and frequency of occurrence of the TIDs suggest that the generation of gravity waves may be caused by winds and tides in the lower thermosphere/mesosphere. On the basis of the availab1e data, a definition of a "disturbance measure" indicating to what extent the ionosphere is "quiet" is proposed. Procedures to correct for ionospheric effects and an eva1uation of the different methods to obtain information on the ionospheric e1ectron content are reviewed in sections 8 and 9, respectively.

scholarly journals A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

1997 ◽  
Vol 15 (8) ◽  
pp. 1048-1056 ◽  
Author(s):  
R. L. Balthazor ◽  
R. J. Moffett
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Ionospheric Disturbance ◽  
Magnetic Equator ◽  
Ionospheric Disturbances ◽  
Atmospheric Gravity Waves ◽  
Opposite Hemisphere ◽  
Travelling Ionospheric Disturbances ◽  
F Region ◽  
Atmospheric Gravity

Abstract. A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the 'fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak) increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs first interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex effects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic field lines by the neutral air pressure wave.

scholarly journals A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995

1996 ◽  
Vol 14 (9) ◽  
pp. 917-940 ◽  
Author(s):  
K. Hocke ◽  
K. Schlegel
Keyword(s):  
Gravity Waves ◽  
Ionospheric Disturbances ◽  
Atmospheric Gravity Wave ◽  
Atmospheric Gravity Waves ◽  
Travelling Ionospheric Disturbances ◽  
The Past ◽  
Low Latitudes ◽  
Subsequent Propagation ◽  
Atmospheric Gravity ◽  
Inversion Techniques

Abstract. Recent investigations of atmospheric gravity waves (AGW) and travelling ionospheric disturbances (TID) in the Earth\\'s thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS), the results are presented in the first part of the review. The second part describes the progress towards understanding the AGW/TID characteristics. It points to the AGW/TID relationship which has been recently revealed with the aid of model-data comparisons and by the application of new inversion techniques. We describe the morphology and climatology of gravity waves and their ionospheric manifestations, TIDs, from numerous new observations.

scholarly journals Estimated influence of stratospheric activity on the ionosphere according to measurements with ISTP SB RAS tools

2021 ◽  
Vol 7 (4) ◽  
pp. 79-84
Author(s):  
Maksim Tolstikov ◽  
Konstantin Ratovsky ◽  
Irina Medvedeva ◽  
Denis Khabituev
Keyword(s):  
Gravity Waves ◽  
Lower Thermosphere ◽  
Correlation Coefficients ◽  
Internal Gravity Waves ◽  
Reanalysis Data ◽  
Time Shift ◽  
Ionospheric Disturbances ◽  
Time Intervals ◽  
Temperature Variations ◽  
Comprehensive Study

We present the results of a comprehensive study of the manifestation of wave activity with periods of internal gravity waves (IGW) in various regions of the atmosphere: in the stratosphere, upper mesosphere, and in the F2-region of the ionosphere. The study is based on radiophysical and spectrometric measurements made with tools of the Institute of Solar-Terrestrial Physics (ISTP) SB RAS and the Era-Interim reanalysis data. The correlation coefficient with time shift between ionospheric and stratospheric activity for the annual interval varies in the range from 0.45 to 0.54, and for the 27-day interval it reaches the levels 0.4–0.8 in seventy percent of the cases. Thirty percent of correlation coefficients less than 0.4 can be explained by the influence of neutral wind, geomagnetic activity, and non-stratospheric IGW sources. Comparison between stratospheric activity and variations in characteristics of traveling ionospheric disturbances (TID) has shown that a ~15 day shift in stratospheric activity results in a fairly high correlation between stratospheric activity and disturbance of IGW characteristics (~0.6). The delay of about 15 days can be attributed to the delay in the temperature variations at heights of the lower thermosphere relative to the temperature variations at the altitude pressure level of 1 hPa. Comparative analysis of variations in mesospheric and ionospheric activity has revealed time intervals when their behavior is consistent.

scholarly journals First GPS TEC maps of ionospheric disturbances induced by reflected tsunami waves: The Tohoku case study

2016 ◽  
Author(s):  
L. Tang ◽  
Y. Zhao ◽  
J. An
Keyword(s):  
Gravity Waves ◽  
Arrival Time ◽  
Tohoku Earthquake ◽  
Internal Gravity Waves ◽  
Ionospheric Disturbances ◽  
Propagation Characteristics ◽  
Tsunami Waves ◽  
Travelling Ionospheric Disturbances ◽  
Ionospheric Height

Abstract. The straight tsunami waves from epicenter can be reflected when they reach to coasts or underwater obstacles. In this study, we present the first ionospheric maps of reflected tsunami signature caused by the great 11 March 2011 Tohoku earthquake using the dense GPS network GEONET in Japan. We observed tsunami-like travelling ionospheric disturbances (TIDs) with similar propagation characteristics in terms of waveform, horizontal velocity, direction, period and arrival time compared to the reflected tsunami at the sea-level, indicating the TIDs are induced by the reflected tsunami. The results confirm the atmospheric internal gravity waves (IGWs) produced by reflected tsunami can also propagate upward to the atmosphere and interact with the plasma at the ionospheric height.

scholarly journals Estimated influence of stratospheric activity on the ionosphere according to measurements with ISTP SB RAS tools

2021 ◽  
Vol 7 (4) ◽  
pp. 84-90
Author(s):  
Maksim Tolstikov ◽  
Konstantin Ratovsky ◽  
Irina Medvedeva ◽  
Denis Khabituev
Keyword(s):  
Gravity Waves ◽  
Lower Thermosphere ◽  
Correlation Coefficients ◽  
Internal Gravity Waves ◽  
Reanalysis Data ◽  
Time Shift ◽  
Ionospheric Disturbances ◽  
Time Intervals ◽  
Temperature Variations ◽  
Comprehensive Study

We present the results of a comprehensive study of the manifestation of wave activity with periods of internal gravity waves (IGW) in various regions of the atmosphere: in the stratosphere, upper mesosphere, and in the F2-region of the ionosphere. The study is based on radiophysical and spectrometric measurements made with tools of the Institute of Solar-Terrestrial Physics (ISTP) SB RAS and the Era-Interim reanalysis data. The correlation coefficient with time shift between ionospheric and stratospheric activity for the annual interval varies in the range from 0.45 to 0.54, and for the 27-day interval it reaches the levels 0.4–0.8 in seventy percent of the cases. Thirty percent of correlation coefficients less than 0.4 can be explained by the influence of neutral wind, geomagnetic activity, and non-stratospheric IGW sources. Comparison between stratospheric activity and variations in characteristics of traveling ionospheric disturbances (TID) has shown that a ~15 day shift in stratospheric activity results in a fairly high correlation between stratospheric activity and disturbance of IGW characteristics (~0.6). The delay of about 15 days can be attributed to the delay in the temperature variations at heights of the lower thermosphere relative to the temperature variations at the altitude pressure level of 1 hPa. Comparative analysis of variations in mesospheric and ionospheric activity has revealed time intervals when their behavior is consistent.

scholarly journals Travelling Ionospheric Disturbances in the F Region

1958 ◽  
Vol 11 (1) ◽  
pp. 91 ◽  
Author(s):  
GH Munro
Keyword(s):  
Seasonal Variation ◽  
Radio Frequency ◽  
Diurnal Variation ◽  
Diurnal Variations ◽  
Ionospheric Disturbances ◽  
Frequency Of Occurrence ◽  
Travelling Ionospheric Disturbances ◽  
F Region ◽  
Seasonal And Diurnal Variations ◽  
Single Radio

Observations of the horizontal movements of travelling ionospheric disturbances recorded on a single radio frequency from April 1948 to March 1957 are analysed for seasonal and diurnal variations of occurrence and of direction and speed of travel. Recording was mainly in daylight hours but some limited night results are included. The average number of disturbances recorded was six per day over the period. Observing accuracy and significance of the deduced data are discussed. The frequency of occurrence has a diurnal variation with a marked midday maximum and a seasonal variation with minima at the equinoxes.

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