Morphology of quantified ionospheric range spread-F over a wide range of midlatitudes in the Australian longitudinal sector

Hajkowicz, L. A. (2007) Morphology of quantified ionospheric range spread-F over a wide range of midlatitudes in the Australian longitudinal sector. Annales Geophysicae, 25 5: 1125-1130. doi:10.5194/angeo-25-1125-2007


Author Hajkowicz, L. A.
Title Morphology of quantified ionospheric range spread-F over a wide range of midlatitudes in the Australian longitudinal sector
Journal name Annales Geophysicae   Check publisher's open access policy
ISSN 0992-7689
1432-0576
Publication date 2007-06-04
Sub-type Article (original research)
DOI 10.5194/angeo-25-1125-2007
Open Access Status DOI
Volume 25
Issue 5
Start page 1125
End page 1130
Total pages 6
Editor Wlodek Kofman
Place of publication Goettingen, Germany
Publisher Copernicus
Language eng
Subject 249999 Physical Sciences not elsewhere classified
C1
780102 Physical sciences
Formatted abstract
Ionograms from a standard vertical-incidence ionosonde chain (nine stations), obtained over a wide range of southern latitudes (in geom.lat. range: 23°–52° S), were digitally scanned at 5-min intervals at nighttime (18:00–06:00 LT) for 13 months (January 2004–January 2005). An important parameter of the F-region, so-called range spread-F (Sr), was for the first time quantified in km. Maximum in Sr was recorded at a sounding frequency of 1.8 MHz for each night and for each ionosonde station. A distinct pattern in the magnitude (in km) and in the percentage occurrence of the range spread-F was present in southern winter only (the June solstice). The sub-auroral region (geom. lat. ≥52° S) is characterised by consistently high spread-F (average Sr≈100 km) on 80–100 per cent of the observed nights. There is a sharp equatorward boundary in the spread-F activity in a latitudinal range: 52°–48° S followed by a midlatitude region (44°–48° S) which exhibits a peak in Sr (≈50 km) in winter only, observed on half of the nights. The midlatitude activity reaches its minimum at 42°–43° S, with Sr less than 20 km on one third of the nights. The low midlatitudes (23°–36° S) are characterised by a strong peak in Sr again in winter, centred at about 30° S (average Sr≈70 km) on 80 per cent of the nights. The pattern becomes largely absent during other seasons particularly in southern summer (the December solstice) when spread-F activity shifts to sub-auroral latitudes. The pattern in the occurrence of spread-F appears to have a global character as the enhanced spread-F activity is observed in the Japanese sector in local summer (i.e. the June solstice).

It appears that the midlatitude spread-F minimum is only apparent but not real. It delineates the boundary between aurorally generated spread-F (due to travelling ionospheric disturbances, TIDs) and low midlatitude spread-F whose origin is not known.
Keyword Astronomy & Astrophysics
Ionosphere
Ionospheric disturbances
Ionospheric irregularities
Mid-latitude ionosphere
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2008 Higher Education Research Data Collection
School of Physical Sciences Publications
 
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Created: Wed, 09 Apr 2008, 23:27:14 EST by Jenny Robinson on behalf of School of Mathematics & Physics