Observation of NPG VLF transmissions at tracy california during path equinox

Abstract

Phase and amplitud e of fiv e NPC wavefront co mpone nt s were recorded at Tracy, Californ ia in March 1964 at a tim e wh e n th e s unri se and s unset lin es were almost p aralle d with th e propaga ti on path. La rge ra pid ph ase and a mplitud e variation s were associate d with sunri se; and at s un set, exac tl y o ne full cyc le of ph ase was acc umul a ted o n 18 of 20 days of recording. Su mm at ion calcula ti o ns based on sim plifi e d ray th eo ry we re ab le to ex plain, a t least qualitative ly, mo s t of the gross featur es of th e data. Howeve r, phase accum ul ati on on thi s particular pat h see ms to req uire an ionosp he ri c mod e l in which partica] re Aec ti o ns ca n be received s imult a neo us ly from two he ight s during the illuminati on tra ns it io n.

Low ionospheric reactions on tropical depressions prior hurricanes

“…The ionosphere properties relevant to propagation of electromagnetic waves are different during daytime and nighttime conditions (see Figure 2). Also, the propagation path of considered signal is very long and several hours during sunrise and sunset it is partially sunlit that results into a highly non-stationary behavior of the recorded VLF signal amplitude (Carpenter and Whitson, 1965;Clilverd et al, 1999). Therefore, to analyze the existing low ionosphere sudden disturbances in the period around TDBs, our sample is additionally divided into four subsamples regarding given TDBs at 3 h UT, 9 h UT, 15 h UT and 21 h UT.…”

Detection of acoustic‐gravity waves in lower ionosphere by VLF radio waves

“…Shaded time intervals in Figure that separate the quasi‐stationary domains indicate the occurrence of complex processes due to ST that perturb the atmospheric layers and VLF wave reflection and propagation conditions, which results into a highly nonstationary behavior of the recorded VLF signal amplitude at sunsets and sunrises. Particular features of these amplitude variations were studied elsewhere [see Carpenter and Whitson , ; Clilverd et al , ], and we take them as a fact meaning that a quasi‐stationary basic state is being perturbed during a given period of time (around the sunrises and sunsets) and it eventually evolves into a new different quasi‐stationary basic state. Each of these two quasi‐stationary basic states contains its own characteristic oscillation spectrum.…”