"Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales" . "Acoustic-gravity waves; Ionospheric effects on radio waves; Ionospheric dynamics; Ionospheric disturbances; Wave propagation"@en . "Compared to investigations of the influence of gravity and planetary waves on the ionosphere, the effects of infrasound variations have not been studied very much in the last 20 years. Here we present some recent results on peculiar transient phenomena occurring at infrasound timescales, as observed by HF Doppler sounding. First, we present examples of S-shaped traces. We show that S-shape phenomena appear to be concentrated near sunset and sunrise. We also discuss their relationship to gravity and infrasound waves. Then we show rare patterns with Doppler shifts corresponding to quasi-linear shape (QLS) phenomena in the time\u2013frequency space. Their slope may be positive or negative. We discuss the possible origin of such a phenomenon. Several potential sources of QLSs were excluded, such as aircrafts, satellites, bolides, meteors, meteorites, thunderstorms or geomagnetic storms. We speculate that QLSs may correspond to the radio waves in the Z-mode reflected at the upper hybrid resonance frequency."@en . "Journal of Atmospheric and Solar-Terrestrial Physics" . "5"^^ . . . "5"^^ . . "Ve srovn\u00E1n\u00ED s gravita\u010Dn\u00EDmi a planet\u00E1rn\u00EDmi vlnami, byly efekty infrazvuku na ionosf\u00E9ru v posledn\u00EDch 20 letech m\u00E9n\u011B studov\u00E1ny. P\u0159edstavujeme zvl\u00E1\u0161tn\u00ED p\u0159echodn\u00E9 jevy pozorovan\u00E9 Dopplerovsk\u00FDmi m\u011B\u0159en\u00EDmi na \u010Dasov\u00FDch \u0161k\u00E1l\u00E1ch infrazvuku. Zaprv\u00E9 jsou to sign\u00E1ly, kter\u00E9 v Doplerovsk\u00E9m spektrogramu vytv\u00E1\u0159\u00ED p\u00EDsmeno S. Ukazujeme, \u017Ee se vyskytuj\u00ED nej\u010Dast\u011Bji kolem v\u00FDchodu \u010Di z\u00E1padu Slunce. Diskutujeme jejich mo\u017En\u00FD vztaj ke gravita\u010Dn\u00EDm \u010Di akustick\u00FDm vln\u00E1m. Za druh\u00E9 p\u0159edstavujeme vz\u00E1cn\u00E9 jevy maj\u00EDc\u00ED v Dopplerovsk\u00FDch spektrogramech kvazi-line\u00E1rn\u00ED tvar; jejich sklon m\u016F\u017Ee b\u00FDt pozitivn\u00ED i negativn\u00ED. Diksutujeme jejich p\u016Fvod. Vylou\u010Dili jsme odraz od letadel, dru\u017Eic, meteorit\u016F i efekty bou\u0159ek. Jako mo\u017En\u00E9 spekulativn\u00ED vysv\u011Btlen\u00ED uv\u00E1d\u00EDme odraz vln transformovan\u00FDch v ionosf\u00E9\u0159e do Z modu na frekvenci horn\u00ED hybridn\u00ED resonance."@cs . . . "\u0160indel\u00E1\u0159ov\u00E1, Tereza" . . . "13"^^ . . . "6" . "Zvl\u00E1\u0161tn\u00ED p\u0159echodn\u00E9 jevy pozorovan\u00E9 Dopplerovsk\u00FDmi m\u011B\u0159en\u00EDmi na \u010Dasov\u00FDch \u0161k\u00E1l\u00E1ch infrazvuku"@cs . "Bure\u0161ov\u00E1, Dalia" . "Zvl\u00E1\u0161tn\u00ED p\u0159echodn\u00E9 jevy pozorovan\u00E9 Dopplerovsk\u00FDmi m\u011B\u0159en\u00EDmi na \u010Dasov\u00FDch \u0161k\u00E1l\u00E1ch infrazvuku"@cs . . "RIV/68378289:_____/08:00306521!RIV08-GA0-68378289" . . "Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales"@en . "Chum, Jaroslav" . "[6105E7BD60CC]" . "Compared to investigations of the influence of gravity and planetary waves on the ionosphere, the effects of infrasound variations have not been studied very much in the last 20 years. Here we present some recent results on peculiar transient phenomena occurring at infrasound timescales, as observed by HF Doppler sounding. First, we present examples of S-shaped traces. We show that S-shape phenomena appear to be concentrated near sunset and sunrise. We also discuss their relationship to gravity and infrasound waves. Then we show rare patterns with Doppler shifts corresponding to quasi-linear shape (QLS) phenomena in the time\u2013frequency space. Their slope may be positive or negative. We discuss the possible origin of such a phenomenon. Several potential sources of QLSs were excluded, such as aircrafts, satellites, bolides, meteors, meteorites, thunderstorms or geomagnetic storms. We speculate that QLSs may correspond to the radio waves in the Z-mode reflected at the upper hybrid resonance frequency." . . "70" . . . "La\u0161tovi\u010Dka, Jan" . . . "386149" . "Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales" . . "RIV/68378289:_____/08:00306521" . "GB - Spojen\u00E9 kr\u00E1lovstv\u00ED Velk\u00E9 Brit\u00E1nie a Severn\u00EDho Irska" . . . "1364-6826" . . "Hru\u0161ka, Franti\u0161ek" . . . . "866;878" . . "Peculiar transient phenomena observed by HF Doppler sounding on infrasound time scales"@en . "P(GA205/04/2110), P(GA205/07/1367), Z(AV0Z30420517)" .