A Numerical Study on the 3‐D Approach of the Equatorial Plasma Bubble Seeded by the Prereversal Vertical Drift

Abstract

Numerical studies concerning equatorial plasma bubble (EPB) seeding source mechanisms have been performed for the last decades. Density perturbations, gravity waves, shear instabilities among others were used in the literature. In all the cases the prereversal vertical drift has a central role, being a necessary condition in addition to all these seeding mechanisms. Notwithstanding, since the prereversal vertical drift presents an asymmetric distribution, this longitudinal variation was hypothesized to act as a seeding source mechanism. This mechanism is capable of providing both contributions: elevate the ionosphere and seed the collisional interchange instability. Two-dimensional investigation was already done, showing the validity of this hypothesis in a bidimensional scenario. Nonetheless, the inclusion of the parallel dynamics could alter the outcome of such analysis, once the component of the conductivity along the geomagnetic field direction causes a load effect reducing the growth rate and shifting its altitude of maximization, thus a 3-D model was developed, named MATPLAB_3D (Mathematical Plasma Bubble Model 3D), and the hypothesis was tested. A progressive approach was performed starting with an oversimplified configuration and concluding with a more realistic profile of prereversal vertical drift obtained using the SAMI2 model. The numerical simulations revealed the existence of a quasi-gaussian seeding source. Also, in case of a prereversal vertical drift varying within 20-60 m/s, the seeded instability evolves into an EPB structure with a longitudinal extension of~2°within~22 min. This EPB maps to low latitude regions and presents secondary structures in its west side. This result further suggests that even though a decrease in the EPB growth due to the inclusion of the parallel conductivity occurred, the hypothesis remains valid.

Modeling of Multi‐Ion Plasma Bubbles in the Equatorial Ionosphere

“…It leads to a slight different reconnection process between the branch A and adjacent bubbles (compared with the cartoon of Figure 1 in Sousasantos et al. (2019)).…”

“…It can be seen from Figure 1 that the left plasma bubbles of branch A have a larger velocity than branch A. It leads to a slight different reconnection process between the branch A and adjacent bubbles (compared with the cartoon of Figure 1 in Sousasantos et al (2019)).…”

“…Sousasantos et al. (2019) shows that the velocities and growth speed of plasma bubbles are larger in the two‐dimensional model than in three‐dimensional models. It can be seen from Figure 1 that the left plasma bubbles of branch A have a larger velocity than branch A.…”

“…Two‐dimensional models of plasma bubbles were first developed by many researchers (e.g., Alam Kherani et al., 2004; Huang & Kelley, 1996; Huba & Joyce, 2007; Zalesak & Ossakow, 1980; Zalesak et al., 1982). To be close to realistic conditions in the ionosphere, three‐dimensional models have been further developed (Aveiro & Hysell, 2010; Huba et al., 2008; Retterer, 2010; Sousasantos et al., 2019; Yokoyama et al., 2014).…”