Annual and semiannual variations in the ionospheric F2-layer. I. Modelling

By L. Zou, H. Rishbeth, I. Müller‐Wodarg, A. Aylward, G. Millward, T. Fuller‐Rowell, D. W. Idenden, R. Moffett. 2000

161 citations recorded by the source corpus.

Annual, seasonal and semiannual variations of F2-layer electron density (NmF2) and height (hmF2) have been compared with the coupled thermosphere-ionosphere-plasmasphere computational model (CTIP), for geomagnetically quiet conditions. Compared with results from ionosonde data from midlatitudes, CTIP reproduces quite well many observed features of NmF2, such as the dominant winter maxima at high midlatitudes in longitude sectors near the magnetic poles, the equinox maxima in sectors remote from the magnetic poles and at lower latitudes generally, and the form of the month-to-month variations at latitudes between about 60°N and 50°S. CTIP also reproduces the seasonal behaviour of NmF2 at midnight and the summer-winter changes of hmF2. Some features of the F2-layer, not reproduced by the present version of CTIP, are attributed to processes not included in the modelling. Examples are the increased prevalence of the winter maxima of noon NmF2 at higher solar activity, which may be a consequence of the increase of F2-layer loss rate in summer by vibrationally excited molecular nitrogen, and the semiannual variation in hmF2, which may be due to tidal effects. An unexpected feature of the computed distributions of NmF2 is an east-west hemisphere difference, which seems to be linked to the geomagnetic field configuration. Physical discussion is reserved to the companion paper by Rishbeth et al.

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Citations in the corpus

Climatology of the mean total electron content derived from GPS global ionospheric maps (2009, result): “…et al., 2000; Duncan, 1969; Mendillo et al., 2005; Oliver et al., 2008; Richards, 2001; Rishbeth, 1998; Rishbeth et al., 2000; Rüster and King, 1973; Su et al., 1998; Torr and Torr, 1973; Torr et al., 1980; West et al., 1997; Wright, 1963; Yonezawa, 1971; Zhang and Holt, 2007; Zou et al., 2000].”
Solar activity variations of nighttime ionospheric peak electron density (2006, background): “The higher noontime electron density in winter is a manifestation of the well-known winter anomaly, which is mainly explained by the O/N2 effect [Rishbeth and Setty, 1961; Rishbeth et al., 2000; Yu et al., 2004].”
Why is there more ionosphere in January than in July? The annual asymmetry in the F2-layer (2006, methodology): “The heavy circles denote the north and south magnetic poles as used in the CTIP model, and the magnetic dip equator is shown. affects F2-layer seasonal behaviour, as can be seen in the maps of Torr and Torr (1973) and has been discussed by Rishbeth (1998) and Zou et al. (2000).”
Modeling the effects of gravity wave momentum deposition on the general circulation above the turbopause (2009, background): “Most thermosphere models even entirely neglect the contribution of small-scale GWs to the energy and momentum budget of the upper atmosphere [e.g., Richmond et al., 1992; Zou et al., 2000; Smithtro and Sojka, 2005; Tian et al., 2008].”