Ionospheric scintillations on 3.925 GHz signal from Intelsat (701) at low latitude in the South Pacific region

Abstract

The morphological features of initial ionospheric scintillations on 3.925 GHz beacon signal from geostationary satellite Intelsat (701) at Suva (Lat., 18.08° S, Long., 178.3° E, Geom. Lat., 22.1° S), Fiji, a low latitude station in the South Pacific region have been studied during the period of December 2003 to June 2004. Scintillations were, in general, sparse, of which activity was more pronounced in the daytime. Scintillation occurrence was less in general, showing a peak value of about 2.5% at 09 h LT and a secondary peak of about 2% at around 16 h LT. Scintillations were weak (S4 index ⩽ 0.25) and occurred mostly in patches of short duration of 2–5 min. It is reported here that weak and short duration scintillations with more daytime occurrence are mainly due to (i) the higher frequency beacon signal used, (ii) the recording station being situated off the equatorial ionisation anomaly belt, and (iii) the period of observation falling in the low solar activity phase of the current solar cycle.

A Study of Daytime L‐Band Scintillation in Association With Sporadic E Along the Magnetic Dip Equator

“…This theory has proven to work well in the midlatitude, where the inclination angle (I) is steep enough to produce Es layers (Whitehead, , ). Evidence regarding the midlatitude (Hajkowicz, , ; Hajkowicz & Minakoshi, ; Ogawa, Suzuki, & Kunitake, ), low latitude, and equatorial regions (Alfonsi et al, ; Huang, ; Kumar et al, ; Patel et al, , ; Seif et al, , , , ; Zou & Wang, ; Zou, ) have shown correlation between the occurrence of daytime scintillation and the Es layer. Nevertheless, thus far, very little is known about the nature of daytime L‐band scintillations and characteristics of Es at the magnetic dip equator, where wind shear theory fails to operate.…”

“…Es can occur during daytime and nighttime. The occurrence of daytime Es can result in strong ionospheric scintillations (Aarons, 1982) even in the frequency range of gigahertz (GHz) (Kumar, Kishore, & Ramachandran, 2007;Seif et al, 2015;Zou, 2011;Zou & Wang, 2009). That is, during daytime, scintillation-producing irregularities are requiring a steep gradient associated with the background plasma-density profile, and a current driven by a neutral wind, where the Es layer is presumed to provide the exceptionally steep gradient particularly in the midlatitude.…”

Daytime gigahertz scintillations near magnetic equator: relationship to blanketing sporadic E and gradient-drift instability

“…Nevertheless, daytime GHz scintillation studies attracted as much attention as nighttime scintillation studies, perhaps because daytime scintillation have a relatively lower rate of occurrence and milder nature (Patel et al 2009). For the most part, scintillations are generally believed to be associated with the F layer at night and the blanketing sporadic E (E sb ) layer during the day (Kumar et al 2007;Zou and Wang 2009;Zou 2011;Seif et al 2012;Alfonsi et al 2013). …”

“…Additionally, a few observations of scintillation in the range of GHz have been also investigated for low latitudes. For example, Kumar et al (2007) used radio transmissions from geostationary satellite Intelsat to determine scintillations at 3.925 GHz at Suva, Fiji (18.08°S, 178.3°E; dip latitude (Ф) = 22.55°S). They showed that scintillation was more pronounced during the daytime.…”