Wavelet analysis on transient behaviour of tidal amplitude fluctuations observed by meteor radar in the lower thermosphere above Bulgaria

Pancheva, D.; Mukhtarov, Plamen

doi:10.1007/s00585-000-0316-3

Cited by 57 publications

(41 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As was mentioned before we would like to study in detail the strength and time of occurrence of any oscillations in neutral wind and in tidal amplitudes which are simultaneously present over both sites. However, as the neutral wind and tidal variability in each site are investigated in detail separately and results are presented for UK and Bulgaria respectively in Beard et al, (1999b) and in Pancheva and Mukhtarov (2000), we have to underline here that the signi®cance of all discussed later oscillations present over both sites is higher than 95% con®dence level. Figure 6a presents a cross-wavelet power spectrum calculated from the hourly time series of zonal winds over Bulgaria and the UK.…”

Section: Day-to-day Variability Of Neutral Wind and Tidesmentioning

confidence: 90%

A comparative study of winds and tidal variability in the mesosphere/lower-thermosphere region over Bulgaria and the UK

et al. 2000

Self Cite

View full text Add to dashboard Cite

Abstract. Meteor radars located in Bulgaria and the UK have been used to simultaneously measure winds in the mesosphere/lower-thermosphere region near 42.5°N, 26.6°E and 54.5°N, 3.9°W, respectively, over the period January 1991 to June 1992. The data have been used to investigate planetary waves and diurnal and semidiurnal tidal variability over the two sites. The tidal amplitudes at each site exhibit¯uctuations as large as 300% on time scales from a few days to the intra-seasonal, with most of the variability being at intra-seasonal scales. Spectral and cross-wavelet analysis reveals closely related tidal variability over the two sites, indicating that the variability occurs on spatial scales large compared to the spacing between the two radars. In some, but not all, cases, periodic variability of tidal amplitudes is associated with simultaneously present planetary waves of similar period, suggesting the variability is a consequence of non-linear interaction. Calculation of the zonal wave number of a number of large amplitude planetary waves suggests that during summer 1991 the 2-day wave had a zonal wave number of 3, but that during January±February 1991 it had a zonal wave number of 4.

show abstract

Section: Day-to-day Variability Of Neutral Wind and Tidesmentioning

confidence: 90%

A comparative study of winds and tidal variability in the mesosphere/lower-thermosphere region over Bulgaria and the UK

et al. 2000

Self Cite

View full text Add to dashboard Cite

show abstract

“…The analysis presented here used the continuous Morlet wavelet, which consists of a plane wave modulated by a Gaussian envelope. The Morlet wavelet was selected because of its simplicity and resemblance to the modulated planetary-wave "packets", which are frequently observed in the ionosphere and MLT region variability (Pancheva and Mukhtarov, 2000). In the following results, we present the wavelet coefficients as a function of period and time.…”

Section: Data Set and Methods Of Analysismentioning

confidence: 99%

“…For any given time all the periods above these lines are expected to suffer from edge effects. The thick contour lines represent 95% confidence levels (Pancheva and Mukhtarov, 2000). The 3-hourly mean data are used in this wavelet analysis to reduce the noise of the time series from hourly values of hmF2.…”

Section: Data Set and Methods Of Analysismentioning

confidence: 99%

Variability in the maximum height of the ionospheric F2-layer over Millstone Hill (September 1998–March 2000); influence from below and above

et al. 2002

Self Cite

View full text Add to dashboard Cite

Abstract. The basic aim of this 'case study' is to investigate the variability in the maximum height of the ionospheric F2-layer, hmF2, with periods of planetary waves (2-30 days), and to make an attempt to determine their origin. The hourly data of hmF2 above Millstone Hill (42.6 • N, 71.5 • W) during 01 September 1998 -31 March 2000 were used for analysis. Three types of disturbances are studied in detail: (i) the 27-day oscillations observed in the hmF2 above Millstone Hill are generated by the geomagnetic activity and by the globalscale 27-day wave present in the zonal mesosphere/lower thermosphere (MLT) neutral wind. The time delay between the 27-day oscillation in the zonal wind and that in the hmF2 is found to be 5-6 days, while between the 27-day oscillation in the geomagnetic activity and that in the hmF2 is found to be 0.8-1 day; (ii) the 16-day oscillation in the hmF2 observed during summer 1999 is probably generated by the global scale 16-day modulation of the semidiurnal tide observed in the MLT region during PSMOS campaign in June-August. We found that if the modulated semidiurnal tide mediates the planetary wave signature in the ionosphere, this planetary wave oscillation has to be best expressed in the amplitude and in the phase of the 12-h periodicity of the ionosphere; and (iii) the third type of disturbances studied is the quasi-2-day activity in the hmF2 that increases during geomagnetic disturbances. The strong pseudo diurnal periodicities generated during the geomagnetic storms can interact between each other and produce the quasi-2-day oscillations in the ionosphere.

show abstract

“…The rTEC oscillations with periods 5-30 days are transient phenomena that are most effectively identified by a wavelet transform method. The wavelet analysis presented here (Pancheva & Mukhtarov 2000) employs the continuous Morlet wavelet, which consists of a cosine wave modulated by a Gaussian envelope. Figure 1 shows the magnitude of 27-day oscillation in both rTEC27 (red line) and rTEC38 (green line) for the whole period of analysis [2000][2001][2002][2003][2004][2005][2006][2007][2008].…”

Section: Medium-and Long-term Ionospheric Response To the Changes In mentioning

confidence: 99%

Solar activity impact on the Earth’s upper atmosphere

Kutiev

Tsagouri

Perrone

et al. 2013

J. Space Weather Space Clim.

View full text Add to dashboard Cite

The paper describes results of the studies devoted to the solar activity impact on the Earth's upper atmosphere and ionosphere, conducted within the frame of COST ES0803 Action. Aim: The aim of the paper is to represent results coming from different research groups in a unified form, aligning their specific topics into the general context of the subject. Methods: The methods used in the paper are based on data-driven analysis. Specific databases are used for spectrum analysis, empirical modeling, electron density profile reconstruction, and forecasting techniques. Results: Results are grouped in three sections: Medium-and long-term ionospheric response to the changes in solar and geomagnetic activity, storm-time ionospheric response to the solar and geomagnetic forcing, and modeling and forecasting techniques. Section 1 contains five subsections with results on 27-day response of low-latitude ionosphere to solar extreme-ultraviolet (EUV) radiation, response to the recurrent geomagnetic storms, long-term trends in the upper atmosphere, latitudinal dependence of total electron content on EUV changes, and statistical analysis of ionospheric behavior during prolonged period of solar activity. Section 2 contains a study of ionospheric variations induced by recurrent CIR-driven storm, a case-study of polar cap absorption due to an intense CME, and a statistical study of geographic distribution of so-called E-layer dominated ionosphere. Section 3 comprises empirical models for describing and forecasting TEC, the F-layer critical frequency foF2, and the height of maximum plasma density. A study evaluates the usefulness of effective sunspot number in specifying the ionosphere state. An original method is presented, which retrieves the basic thermospheric parameters from ionospheric sounding data.

show abstract

Wavelet analysis on transient behaviour of tidal amplitude fluctuations observed by meteor radar in the lower thermosphere above Bulgaria

Cited by 57 publications

References 51 publications

A comparative study of winds and tidal variability in the mesosphere/lower-thermosphere region over Bulgaria and the UK

A comparative study of winds and tidal variability in the mesosphere/lower-thermosphere region over Bulgaria and the UK

Variability in the maximum height of the ionospheric F2-layer over Millstone Hill (September 1998–March 2000); influence from below and above

Solar activity impact on the Earth’s upper atmosphere

Contact Info

Product

Resources

About