Model of equatorial scintillations from in‐situ measurements

Abstract

In‐situ measurements of F‐region irregularity amplitude and ambient electron density made by the retarding potential analyzer on OGO‐6 near the perigee altitude of 400 km have been utilized to derive the variation of electron density deviation over the equatorial region. Based on these measured electron density deviations and other assumed model parameters including a three‐dimensional power law form of irregularity spectrum with index 4, a model of equatorial scintillations is developed in the framework of diffraction theory. The percentage occurrence contours of estimated equatorial scintillations ≥ 4.5 dB at 140 MHz during 1900–2300 LMT for the period November–December 1969 and 1970 have been derived. The model is found to depict a pronounced longitude variation with the scintillation belt width and percentage occurrence being maximum over the African sector. The latitude extent of the spatial scintillation belt narrows over the American sector without much decrease in the scintillation occurrence whereas over the Indian and Far Eastern sectors both the extent and the occurrence are found to decrease. The percentage occurrence of scintillations estimated from this model is found to be consistent with VHF scintillation measurements at Ghana, Huancayo, and Calcutta. In addition, the model was found to be in qualitative agreement with GHz observations at various longitudes made by the COMSAT group. The effects of varying model parameters on scintillation estimates at VHF, UHF, and GHz are discussed. Implications of the observed longitudinal variation of scintillations on current theories of equatorial irregularity formation are indicated.

Analysis of ionospheric scintillation spectra and TEC in the Chinese low latitude region

“…The percentage of irregularities in these fluctuations is usually very small, but it can be as large as nearly 100% near the equator (Basu and Khan, 1976). The irregularities are predominantly in the F-layer of the ionosphere at altitudes ranging from 200 to 1000 km, with the primary disturbance region being typically between 250 and 400 km.…”

Statistical analysis of C/NOFS planar Langmuir probe data

“…Indeed, as stressed by Yeh and Liu (1982), the above is the basic equation upon which ionospheric scintillation theories are developed. The weak-scattering theory (Rufenach, 1975;Basu et al, 1976;Costa and Kelley, 1977;Rino, 1979) estimates the scintillation index S 4 of the signal received on the ground after propagating through an irregularity layer by the equation…”

Modelling of Equatorial Phase and Amplitude Scintillations From Ogo-6 and Ae Irregularity Data

“…However, it is possible to obtain estimates of this parameter from insitu data obtained by satellites in elliptic orbit or direct radar backscatter observations [15,37]. The observing period encompassed two magnetic storms but due to paucity of data separation on the basis of magnetic activity levels was not possible.…”

“…At the equator, Basu et al [14,15] and improving it by comparing the model predictions of scintillations against available ground scintillation observations. While the step was in the right direction, more than 60% of their thirty modelling categories had to remain untested because of a lack of data at that time.…”