Observation of F-layer and sporadic-E scatter at VHF in the Far East

Abstract

This p aper describes proper t ies of sporad icE scatter and F-layer scaLtcr observed ove r t he Okinawa-to-Tokyo path (1480 kilometers) a nd the Philippines-to-To kyo p at h (2 850 kilo met ers) operating at frequ encies of a bou t 50 megacy cles p er second. Spora dicE scatter is ofte n obser ved on t he Okin a wa signal in t he e \'cn ing homs and has t he closest correlation (0.94 i n co rrelation ratio) wi t h the occ urrence of sporadi c E chara cterized by the descriptive symbol " M " of a ll ionospheri c facto rs. Beari ng o f t he E s sca tter shows a regular diurn al va riation simila r to t hat of t he no rma l E-layer scatter. F-layer scatter ge nerally a ppears on t he Philippine signal in a ut umn when t he F-IavC' l' at t he p ath midpoin t displays an a nom a ly denoted by t he symbol " R " o r "8" having a to p freque ncy of hi gher t han J4 megacycles pel' second. A pulse test ex hibited a patLe l'll o f m ultipat ll s ig na ls exte nding over more t ha n 1 mill isecond. Bearing of t llC Player scatter an even ing ph eno menon, gradu a lly de viates \yestwa rds from the great-circle path \y it h th~ lapse of t ime.

Interrelations of Sporadic E and Ionospheric Currents

“…Es in middle latitudes (designated as m-Es in the present paper) observed by VHF oblique incidence ·shows that there are at least two distinctly different types [e.g., Miya et al, 1961;Tao, 1962;A. Spizzichino, private communication].…”

Characteristics of Ionospheric Es Propagation and Calculation of Es Signal Strength

“…The authors [Miya et al, 1961] have classified the ionospheric signal via the E-region into three modes of Ea specular reflection signal, Ea scatter, and normal E scatter, in addition to the normal E reflection signal. These signals, which have peculiar behavior in fading and characteristic features in angle of arrival, can be distinguished according to the amount of ionospheric attenuation, as shown in table 2.…”

The Structure of the Sporadic E Layer Detected from VHF Ionospheric Propagation

“…Measured field intensities observed over several oblique VHF propagation paths in middle latitudes show that there are different kinds of fadin~ depend- ing on the appearance time of sporadic E. During the daytime, in general, interference-type fadings are superimposed on fairly high field intensities, while the field intensities at night are not higher than those in •he daytime and usually are accompanied by scatteringtype fadings. Miya et al [1961] also suggested that the VHF ionospheric propagation mode could be classified into three propagation modes, i.e., Es reflection, E. scatter, and D scatter, depending on the magnitude of attenuation f. From the discussion in section 2, it is reasonable to assume that the sporadic E propagation mode is divided into £ 5 reflection and E. scatter.…”