Equatorial F-region irregularities generated by the Rayleigh-Taylor instability mechanism – rocket observations from Brazil

Abstract

Several sounding rockets carrying plasma diagnostic experiments were launched from the Brazilian rocket launching stations in Natal (5.9 • S, 35.2 • W Geog. Lat.) and Alcântara (2.31 • S, 44.4 • W Geog. Lat.). Langmuir Probes (LP) were used to measure the height profiles of electron density and electron temperature and High Frequency Capacitance (HFC) probes were used to measure electron density. The LP's were also used to measure the amplitude of electron density fluctuations.A detailed study of the characteristic features of electron density irregularities in the scale size range of less than a meter to a few kilometres, observed by rocket-borne electron density probes under different ionospheric conditions is presented here. The main objective of these studies is the identification of these irregularities from the point of view of the dynamic and electrodynamic processes responsible for their generation. The existing theories of the Rayleigh Taylor Instability (RTI) mechanism applicable for conditions of the geomagnetic equatorial ionosphere over Brazil are critically examined in the light of the observations. The observed characteristics of the irregularities during four rocket launches are compared with the theoretically expected characteristics. These results confirm the operation of a cascade process that is responsible for the generation of a wide spectrum of irregularities. The large-scale irregularities are first generated probably by the RTI mechanism that creates conditions favourable for the operation of the Cross-Field (CFI) or the Gradient Drift Instability (GDI) mechanism. From the k-spectra of irregularities it is possible to obtain the spectral index n corresponding to the height chosen. In most of the cases the estimated spectral indices agree well with those published in the literature for the cases of irregularities generated by the GDI mechanism.

An Imaging Evidence of the East Wall Structuring of Eastward Drifting Depletions Observed Near the EIA Crest in India

“…In accordance with Huba and Joyce (2007) simulations, such diffusion can result in its complex evolution with multiple bifurcations on both its walls. Muralikrishna and Vieira (2007) also suggest that the cascade process linked with the large‐scale upwellings could generate SIs via cross‐field instability and GDI. Studies by Garcia et al.…”

“…Often secondary instabilities (SIs) are seen to develop on the walls of nonlinearly growing equatorial plasma bubbles (EPBs) (Hysell, 2000; Huba & Joyce, 2007; Li et al., 2021; Muralikrishna & Vieira, 2007; Zalesak et al., 1982). Numerous radar and optical airglow observations from the Northern Hemisphere have shown their development on the west wall of an eastward drifting depletion (EDD) (Kelley et al., 2000; Makela, 2006; Mukherjee, 2003; Mendillo & Baumgardner, 1982; Rodrigues et al., 2018; Rohrbaugh et al., 1989; Tsunoda, 1983, 2015; Tsunoda & White, 1981; Tsunoda et al., 1982, 2011; Xiong et al., 2018; Yokoyama et al., 2014, 2015).…”

Influence of Zonal Wind Velocity Variation on Equatorial Plasma Bubble Occurrences Over Southeast Asia

“…However, EPB occurrences vary from day‐to‐day (Sharma et al., 2014). This phenomenon has been extensively investigated for decades using various equipment such as the incoherent back scatter radar, all‐sky imager and satellites (Immel et al., 2004; Mukherjee et al., 1997; Muralikrishna and Vieira, 2007; Sharma et al., 2014; Tsunoda, 2015).…”

Hindcasting of Equatorial Spread F Using Seasonal Empirical Models

“…It has been established that the seeding by these waves becomes pertinent in the solstice months, when the post sunset rise (PSSR) of the F layer is weak (Tsunoda, ). Muralikrishna and Vieira () reported that a higher F region base is preferable for R‐T instability to operate. Ossakow et al () presented a numerical simulation study, showing that the injection of an artificial depletion at the bottom side of the F layer can cause ESF to occur.…”