Magnetic Field and Electron Density Scaling Properties in the Equatorial Plasma Bubbles

Paola De Michelis,Fabio Giannattasio,Alessio Pignalberi,Roberta Tozzi,Igino Coco,Michael Pezzopane,Tommaso Alberti,Giuseppe Consolini

doi:10.3390/rs14040918

Abstract

The ionospheric plasma density irregularities are known to play a role in the propagation of electromagnetic signals and to be one of the most important sources of disturbance for the Global Navigation Satellite System, being responsible for degradation and, sometimes, interruptions of the signals received by the system. In the equatorial ionospheric F region, these plasma density irregularities, known as plasma bubbles, find the suitable conditions for their development during post-sunset hours. In recent years, important features of plasma bubbles such as their dependence on latitude, longitude, and solar and geomagnetic activities have been inferred indirectly using their magnetic signatures. Here, we study the scaling properties of both the electron density and the magnetic field inside the plasma bubbles using measurements on board the Swarm A satellite from 1 April 2014 to 31 January 2016. We show that the spectral features of plasma irregularities cannot be directly inferred from their magnetic signatures. A relation more complex than the linear one is necessary to properly describe the role played by the evolution of plasma bubbles with local time and by the development of turbulent phenomena.

Highlights

One of the most interesting features of the equatorial ionospheric F region is the existence of plasma density irregularities, which find the suitable conditions for their development during post-sunset hours [1]
Taking into account the relation between the second-order scaling exponent and the Fourier power spectral density exponent (β = γ(2) + 1), we notice that the spectral features obtained in the case of electron density (β ' 2) are in agreement with previous results
Livingston et al [58] analyzing the spectra of electron density data recorded from the Atmospheric Explorer-E satellite (AE-E) in the interval 20:00–02:00 local time (LT) found a distribution of spectral slopes in the range between 1 and 3 centered around 1.9, which is a mean value that agrees with our results and is close to those of Dyson et al [59], who used data recorded by the OGO satellite, Basu et al [60], who analyzed AE-E measurements, and

Summary

Introduction

One of the most interesting features of the equatorial ionospheric F region is the existence of plasma density irregularities, which find the suitable conditions for their development during post-sunset hours [1]. “bite-outs,” or “plasma holes”, because the irregularities were recorded mostly at locations where the electron density is depleted with respect to the background ionosphere (e.g., McClure et al [3], Dyson and Benson [4]). It is worth noting that recent studies (e.g., Kil et al [8]) introduced the expression “plasma depletion shell” to highlight the three-dimensional structure of bubbles The formation of these irregularities is recognized to be driven by the Rayleigh–Taylor instability mechanism [6,9,10] that generates in the ionosphere a situation similar to that occurring when a heavy fluid flows over

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