Statistical investigation of horizontal propagation of gravity waves in the ionosphere over Europe and South Africa

Chum, Jaroslav; Athieno, R.; Baše, Jiří; Burešová, Dalia; Hruška, František; Laštovička, Jan; McKinnell, Lee-Anne; Šindelářová, Tereza

doi:10.1029/2011ja017161

Cited by 21 publications

(28 citation statements)

References 38 publications

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“…Similar seasonal behavior, i.e., poleward propagation in summer and equatorward in winter, was observed in previous studies using HF Doppler sounding over the Czech Republic, South Africa, and Argentina (Chum et al 2010(Chum et al , 2012(Chum et al , 2014. Ding et al (2011) investigated MSTIDs over Central China using GPS-TEC measurements.…”

Section: Resultsmentioning

confidence: 64%

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Medium-scale traveling ionospheric disturbances over Taiwan observed with HF Doppler sounding

Fišer

Chum

Liu

2017

Earth Planets Space

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We analyzed horizontal velocities of medium-scale traveling ionospheric disturbances using HF Doppler sounding over Taiwan from January 2014 to January 2016. Meridional components of the observed horizontal velocities are in most cases larger than zonal components. In summer, poleward propagation prevails, whereas in winter, disturbances primarily propagate southward. Zonal components of the analyzed events are mostly eastward. Seasonal behaviors of the observed propagation directions are similar at other locations with HF Doppler sounding at middle and low latitudes. Horizontal velocities of the observed events are in the 50-400-ms −1 range. The upper limit is determined using the spacing between reflection points, making the uncertainty in velocity very large for events with velocities larger than this limit. The mean horizontal velocity is 210 ms .

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Section: Resultsmentioning

confidence: 64%

“…1. A more detailed description of similar Doppler sounding systems operating in other locations can be found in Chum et al (2010Chum et al ( , 2012, and Doppler sounding theory is described in more detail in Chum et al (2016).…”

Section: Doppler Sounding Systemmentioning

confidence: 99%

Medium-scale traveling ionospheric disturbances over Taiwan observed with HF Doppler sounding

Fišer

Chum

Liu

2017

Earth Planets Space

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“…Tsugawa et al (2007) found from GPS measurements over the USA on 28 November 2006 daytime: λ x = 300-1000 km. Chum et al (2012) found using multiple Doppler sounders in the Czech Republic values of λ x between 100 and 300 km.…”

Section: Comparisons With Other Studiesmentioning

confidence: 99%

“…Also the wave observed by Tsugawa et al (2007) over the USA on 28 November 2006 in the daytime with λ x similar to this paper, propagated southeastward. Chum et al (2012) found that the TIDs over the Czech Republic in the winter propagated with azimuths between 90 and 180 • .…”

Section: Comparisons With Other Studiesmentioning

confidence: 99%

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TID characterised using joint effort of incoherent scatter radar and GPS

2014

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Abstract. Travelling Ionospheric Disturbances (TIDs), which are caused by Atmospheric Gravity Waves (AGWs), are detected and characterised by a joint analysis of the results of two measurement techniques: incoherent scatter radar and multiple-receiver GPS measurements. Both techniques to measure TIDs are already well known, but are developed further in this study, and the strengths of the two are combined, in order to obtain semi-automatic tools for objective TID detection. The incoherent scatter radar provides a good vertical range and resolution and the GPS measurements provide a good horizontal range and resolution, while both have a good temporal resolution. Using the combination of the methods, the following parameters of the TID can be determined: the time of day when the TID occurs at one location, the period length (or frequency), the vertical phase velocity, the amplitude spectral density, the vertical wavelength, the azimuth angle of horizontal orientation, the horizontal wavelength, and the horizontal phase velocity. This technique will allow a systematic characterisation of AGWTIDs, which can be useful, among other things, for statistical analyses.The presented technique is demonstrated on data of 20 January 2010 using data from the EISCAT incoherent scatter radar in Tromsø and from the SWEPOS GPS network in Sweden. On this day around 07:00-12:00 UT, a mediumscale TID was observed from both data sets simultaneously. The TID had a period length of around 2 h, and its wave propagated southeastward with a horizontal phase velocity of about 67 m s −1 and a wavelength of about 500 km. The TID had its maximum amplitude in Tromsø at 10:00 UT. The period length detected from the GPS results was twice the main period length detected from the radar, indicating a different harmonic of the same wave. The horizontal wavelength and phase velocity are also estimated from the radar results using Hines' theory, using the WKB approximation to account for inhomogeneity of the atmosphere. The results of this estimate are higher than those detected from the GPS data. The most likely explanation for this is that Hines' theory overestimated the values, because the atmosphere was too inhomogeneous even for the WKB approximation to be valid.

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Estimating the propagation characteristics of large‐scale traveling ionospheric disturbances using ground‐based and satellite data

2013

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In this article, the propagation characteristics of large‐scale traveling ionospheric disturbances (LS TIDs) are estimated during the geomagnetic storm periods of 14–16 May 2005 and 25–27 September 2011 over South Africa. One and two GPS arrays have been independently considered for the storms of 15 May 2005 and 26 September 2011, respectively. The average periods of dominant modes (≈ 2.5–3.5h) in the time series data were determined by applying wavelet analysis on both ionosonde and GPS data. The consideration of diurnal GPS total electron content (TEC) variability from receivers along three different longitude sectors showed a time shift in TEC enhancement with increasing latitude, the first indication of equatorward motion of the traveling ionospheric disturbances (TIDs). The statistical method (based on GPS radio interferometry) employed shows that these TIDs were mostly propagating nearly equatorward (for both storm periods), which is consistent with the existing literature about storm‐induced TIDs. On storm days, TID horizontal velocities have been determined in the range of ≈200–500m/s. The analysis of diurnal TEC response from different stations confirmed that the positive storm effect observed on 15 May 2005 was a result of the large‐scale TIDs of wavelength ≈4000 km. On the other hand, the estimated wavelengths of LS TIDs on 26 September 2011 were ≈2400–3400km between 10 and 17 UT. A time lag is observed between the times at which enhancements in TEC, ionosonde foF2, and hmF2 data are revealed, and this has been attributed to the passage of the TID.

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Statistical investigation of horizontal propagation of gravity waves in the ionosphere over Europe and South Africa

Cited by 21 publications

References 38 publications

Medium-scale traveling ionospheric disturbances over Taiwan observed with HF Doppler sounding

Medium-scale traveling ionospheric disturbances over Taiwan observed with HF Doppler sounding

TID characterised using joint effort of incoherent scatter radar and GPS

Estimating the propagation characteristics of large‐scale traveling ionospheric disturbances using ground‐based and satellite data

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