Detection of the wave-like structures in the F-region electron density: Two station measurements

Abstract

Comparative studies of short-term ionospheric variability in the F region ionosphere during rapid sequence sounding campaign "HIRAC/SolarMax" (23−29 April 2001) are presented. The ionospheric short-term fluctuations have been studied in detail using measurements from vertical sounding at Ebro (40.8°N, 0.5°E) and Průhonice (49.9°N, 14.5°E) in the period range from 15 minutes to 2 hours. The electron density measurements contain variations that indicate the possible presence of propagating gravity waves. Regular wave-like bursts were found during quiet days at both stations in electron concentration in F region, with an increase of the oscillation activity after sunrise and then during late afternoon, and at sunset and after sunset. Solar Terminator is assumed to be one of the sources of the regular wave bursts detected in the ionosphere during campaign HIRAC. As expected, substantial intensification in longer period gravity waves was found to occur during the disturbed period on April 28. Particular enhancement of the wave-like activity during disturbed day is discussed, being significant evidences of a change of the wave-like activity pattern at a height around 200 km.

Wavelet characterisation of ionospheric acoustic and gravity waves occurring during the solar eclipse of August 11, 1999

“…Waves with significant vertical component of movement that propagate from lower layers of the atmosphere and might have their origin in, for instance, meteorological phenomena etc., and waves with very small vertical component of movement that propagate horizontally from auroral region and that are related to the geomagnetic disturbances. Works by Somsikov (1991), Bosˇka et al (2003) and Sˇauli et al (2005) reported regular occurrence of gravity waves during morning and evening hours that are likely to be produced by solar terminator movements. Such waves remain within ionosphere only for a short time period during sunrise and sunset hours and have characteristics similar to the waves detected in the present work in terms of source region location (round 200 km) and propagations upward and downward from this region.…”

“…However, such ideal comparisons cannot be simply performed due to the lack of the corresponding measurements. Comparisons can be drawn against studies of 5-min ionospheric sounding, such as those in , Bosˇka and Sˇauli (2001), Bosˇka et al (2003), Martinis and Manzano (1999), Sˇauli and Bosˇka (2001) and Sˇauli et al (2005), satellite or rocket measurements such as Bertin et al (1978) and Kelley (1997), arrays of ionosonds as reported in Somsikov (1991) and many others. We can compare the times of occurrence, differences and similarities in the vertical structure and source location.…”

Ionospheric behavior over Europe during the solar eclipse of 3 October 2005

“…They are almost always present in the atmosphere showing high day-to-day variability. It has been found that gravity waves are generated by many sources including topography, explosions, motion of large meteorological systems, wind shear, solar terminator motion, and others (Somsikov, 1995;Manzano et al, 1998;Martinis and Manzano, 1999;Fritts and Alexander, 2003;Fritts et al, 2006;Sauli et al, 2006b). Properties of the neutral waves, such as period and wavelength, are closely reflected by the electron density fluctuation due to the coupling of neutral and ionized components of the atmosphere.…”

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

“…GW propagation from below is also influenced by thermal ducts that can transfer wave-associated energy and momentum over large horizontal distances (Hocke and Schlegel 1996;Yu and Hickey 2007). Another mechanism for generating GWs is the solar terminator, when gradients in the thermosphere arise and wave activity is a mechanism for reversing to the equilibrium state (Boška et al 2003;Šauli et al 2006). Auroral processes also generate GWs, which propagate equatorward (Hunsucker 1982).…”