Electrodynamics of the vertical coupling processes in the atmosphere-ionosphere system of the low latitude region

Abstract

Dynamical, electro-dynamical and electrical coupling processes originating from upward propagation of atmospheric waves, and magnetosphere-ionosphere interaction are responsible for the large degree of variabilities observed in the low latitude ionosphere. One of the most outstanding aspects of its phenomenology is related to the sunset electrodynamical processes responsible for the evening enhancements in zonal and vertical electric fields and the associated spread of F/plasma bubble irregularity development. Recent observational results have provided evidence of significant contribution to their quiet time variability arising from thermospheric wind patterns, upward propagating planetary waves and possibly sporadic E layers. This paper provides an overview and some new results on planetary wave coupling with the equatorial F region, the E layer conductivity as key connecting mechanism, a possibly interactive role by sporadic E layers, and the resulting day-today variability in the evening prereversal electric field enhancements with consequences on spread F development.

Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development

“…Detailed calculations have shown (e.g., Abdu et al 2003) that an increasing westward wind could cause increase in the longitudinal/local time gradient in the post sunset E layer electron density and hence in the integrated conductivity. The effect of such an increase in the conductivity gradient is to raise the PRE vertical drift amplitude, as demonstrated, for example, by Abdu and Brum (2009). Conversely, an increase in eastward wind could produce a decrease in the conductivity longitudinal gradient with corresponding decrease in the PRE vertical drift.…”

“…The effect of the PRE on the hF diminishes towards later hours approaching midnight with almost no effect into the post midnight hours. In this context, it was shown by Abdu and Brum (2009) that while the PW oscillation in the PRE vertical drift was present also in the hF values of the post sunset hours, it was totally absent in the hF values of the post midnight hours, over the same station, Fortaleza. Thus, the observation of the PW/UFK wave oscillations in the F layer height during post sunset-pre midnight hours reported in the literature (for example, Takahashi et al 2007Takahashi et al , 2009Fagundes et al 2009) are indeed indicative of the manifestations of the PRE modulation by the upward propagating waves.…”

“…The well-established mechanism for the development of the evening PRE vertical drift/eastward electric field enhancement is based on the E and F layer sunset electrodynamic coupling involving the F layer dynamo. As explained by Abdu and Brum (2009), the thermospheric zonal wind that turns eastward near 17 LT induces vertical electric field (E z ) in the F region as represented by…”

Correlation between the global occurrences of ionospheric irregularities and deep atmospheric convective clouds in the intertropical convergence zone (ITCZ)

“…Close relationship of the electrodynamic perturbations with the irregularity occurrences in the post-sunset ionosphere has been discussed by Hysell (2000) and Mendillo et al (2001). The occurrences of electrodynamic perturbation have further been discussed by Abdu and Brum (2009) as due to changes in the longitudinal/local-time gradients of E-region conductivities caused by the vertical coupling process in the atmosphere-ionosphere system in the low-latitude region. The electrodynamic coupling process comes from the upward propagating atmospheric waves, such as tidal modes, planetary waves, and gravity waves.…”

Thermospheric planetary wave‐type oscillations observed by FPIs over Xinglong and Millstone Hill

“…These PW‐type oscillations (PWTOs) have been observed in the ionosphere parameters such as f o F 2 (critical frequency in the F 2 layer), h m F 2 (height of the maximum electron density), h'F (apparent height of the F region), and total electron content. Ionospheric observations of these oscillations were also reproduced by numerical simulations [e.g., Chen , ; Forbes and Zhang , ; Takahashi et al ., ; Xiong et al ., ; Abdu and Brum , ; Liu et al ., ; Vergasova et al ., ; Yue et al ., ].…”