Anomalous variations in the ionospheric F 2-layer structure at geomagnetic midlatitudes of the Southern and Northern hemispheres at the transition from summer to winter conditions under low solar activity

Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

“…This decrease in the relative role of these two sources of the NmF2 winter anomaly can be responsible for the decrease of Q(R>1) with decreasing solar activity over the Argentine Islands (see Table 2). At solar minimum, the mid-latitude winter anomaly of NmF2 is practically not produced by seasonal variations of the vibrationally excited N 2 and O 2 temperatures, and the role of electronically excited oxygen ions in producing the mid-latitude winter/summer anomalous difference in NmF2 is less than that caused by seasonal variations of neutral number densities (Pavlov et al, 2008b). We conclude that seasonal neutral composition variations are mainly responsible for the very low probability to observe the winter anomaly of NmF2 over the Argentine Islands at solar minimum shown in Table 2.…”

“…The fundamental laboratory measurements (Schmeltekopf et al, 1968;Hierl et al, 1997) show that vibrationally excited N 2 and O 2 react much more strongly with O + ( 4 S) ions than vibrationally unexcited N 2 and O 2 . The daytime mid-latitude electron density of the F2-region is decreased up to a factor of 2-3 due to vibrationally excited N 2 and O 2 (Pavlov, 1998;Pavlov et al, 1999;Pavlov and Foster, 2001;Prolss and Werner, 2002). As a result, a part of the mid-latitude F2-layer winter anomaly can be attributed to the seasonal difference of the increase in the loss rate of O + ( 4 S) ions due to vibrationally excited N 2 and O 2 (Torr et al, 1980;Pavlov and Pavlova, 2005;Pavlov et al, 2008a, b).…”

A statistical study of the mid-latitude NmF2 winter anomaly

“…At solar minimum, the mid-latitude winter anomaly of NmF2 is practically not produced by seasonal variations of the vibrationally excited N 2 and O 2 temperatures, and the role of electronically excited oxygen ions in producing the mid-latitude winter/summer anomalous difference in NmF2 is less than that caused by seasonal variations of neutral number densities (Pavlov et al, 2008b). We conclude that seasonal neutral composition variations are mainly responsible for the values of P(R > 1), R MP , and hRi at solar minimum.…”