F layer postsunset height rise due to electric field prereversal enhancement: 1. Traveling planetary wave ionospheric disturbance effects

Abstract

An ionospheric sounding station is operational at Palmas (10.2°S, 48.2°W, dip latitude 5.5°S), Brazil, since 2002. Observations of F layer virtual height day‐to‐day variations during evening hours (1800 LT to 2000 LT) show a strong variability, even during geomagnetically quiet periods. From the ionospheric multifrequency virtual height variations (at 3, 4, 5, 6, 7, and 8 MHz), observed from July 2003 to May 2004, it is found that the virtual height day‐to‐day variability presents oscillations with periods of days during the evening hours. The thermospheric wind component perpendicular to the magnetic meridian (zonal wind) is one of the primary sources that generate the F region dynamo near sunset, which causes the zonal electric field prereversal enhancement (PRE) that induces the E × B vertical F layer postsunset height rise. Therefore, the planetary wave (PW) component that flows superposed on the thermospheric wind induces a traveling planetary wave ionospheric disturbance (TPWID) on the vertical F layer displacement. This indicates that the postsunset ionospheric height rise can be strongly modulated by TPWID oscillations. Our study shows that TPWIDs with periods of several days control the strength of the electric field PRE and, therefore, slowly push the F layer heights up or down, according to the TPWID phase. Also, simultaneous virtual height variations at Sao José dos Campos (low latitude) and Palmas (equatorial region) for October and November show similar behavior. This suggests that TPWID oscillation is a manifestation of atmospheric equatorial Kelvin waves that modulate the thermospheric wind.

Quiet time variability of the GPS TEC and EEJ strength over Indian region associated with major sudden stratospheric warming events during 2005/2006

“…Recently, Liu et al [2010]have modeled the ionospheric variability during solar minimum conditions when PWs are excited in the winter stratosphere using TIME‐GCM model. The model results suggest that PW and tidal interaction leads to large changes in the tides, which can strongly impact the ionosphere at low and midlatitudes through E region wind dynamo Fagundes et al [2009a, 2009b]…”

Ionospheric response to the 2009 sudden stratospheric warming over the equatorial, low, and middle latitudes in the South American sector

“…This VTEC enhancement is due to the electric field prereversal enhancement that takes place just after the sunset, and it reinforces the EIA. It is important to mention that the effects of the electric field prereversal enhancement in the TEC, at low latitude, depend on season and solar cycle [for more details, see Fejer et al, 1979;Fagundes et al, 2009].…”

Zonal flows and magnetic fields driven by large‐amplitude Rossby‐Alfvén‐Khantadze waves in the E‐layer ionosphere

“…There are numerous ground-based and satellite observations of planetaryscale structures in the ionosphere with periods of days: Cavalieri et al [1974], Cavalieri [1976], Manson et al [1981], Hirooka and Hirota [1985], Randel [1987], Sorokin [1988], Sharadze et al [1988Sharadze et al [ , 1989, Williams and Avery [1992], Forbes and Leveroni [1992], Bauer et al [1995], Zhou et al [1997], Lastovicka [1997], Smith [1997], Lawrence and Jarvis [2003], Burmaka et al [2006], and Alperovich and Fedorov [2007]. Fagundes et al [2005Fagundes et al [ , 2009aFagundes et al [ , 2009b report correlations of the planetary-scale structures with periods of days with enhanced levels of ionospheric disturbances between 18:00 and 21:00 UT. There is increasing interest in these planetary-scale ultralow-frequency (ULF) fluctuations owing to their being associated with extraordinary high-energy phenomena including major solar storms, earthquakes, and volcano eruptions [Haykowicz, 1991;Liperovsky et al, 1992;Cheng and Huang, 1992;Pokhotelov et al, 1995;Lewis et al, 1999;Burmaka and Chernogor, 2004;Burmaka et al, 2005].…”

“…Both types of waves create traveling ionospheric disturbances and are discussed by Fagundes et al [2009aFagundes et al [ , 2009b from analysis of the structures of ionospheric backscattering data from time-resolved six-frequency (at 3,4,5,6,7,and 8 MHz) time-resolved radar backscattering data. The data show correlations of long-period planetary waves with enhanced ionospheric disturbances in the postsunset [~18:00 to 21:00UT] ionospheric plasma.…”