L‐Band Synthetic Aperture Radar Observation of Ionospheric Density Irregularities at Equatorial Plasma Depletion Region

Hiroatsu Sato,Eurico Rodrigues De Paula,Jun Su Kim,Jonas Rodrigues De Souza,Cristiano Max Wrasse,Yuichi Otsuka

doi:10.1029/2021gl093541

Abstract

AbstractPlasma density irregularities in the equatorial ionosphere are thought to cause the distortions of L‐band Synthetic Aperture Radar (SAR) images, which have been observed in recent years, but the origin of the image distortion has not yet been clearly identified experimentally. We report on the first simultaneous observation of equatorial plasma bubbles (EPBs) by the ALOS‐2/PALSAR‐2 satellite and ground 630‐nm airglow imager in northern Brazil. We observe stripe‐like distortions of SAR signal power that are aligned in the direction of local magnetic field lines. The stripe‐like patterns are observed in the vicinity of airglow depletion. The result shows that the observed L‐band SAR stripes are caused by ionospheric scintillation due to plasma irregularities with the scale size of hundreds of meters associated with EPBs. We show that the SAR scintillation stripes are predominantly found at the location of sharp density gradients in the two‐dimensional form.

Highlights

Plasma density depletions in the post-sunset equatorial ionosphere, known as Equatorial Plasma Bubbles (EPBs), are thought to be a primary source of plasma irregularities on a scale from centimeters to kilometers that scatter radio waves at various wavelengths (e.g., Basu et al, 1978; McNamara et al, 2013; Saito et al, 2008; Tsunoda, 1980)
We report on the first simultaneous observation of equatorial plasma bubbles (EPBs) by the ALOS-2/PALSAR-2 satellite and ground 630-nm airglow imager in northern Brazil
The objective of this paper is to report the first simultaneous observations of EPB by the ALOS-2/PALSAR-2 satellite and 630-nm airglow all-sky imager in northern Brazil in order to experimentally show what may be an origin of L-band Synthetic Aperture Radar (SAR) scintillation at equatorial regions in the two-dimensional form

Summary

Introduction

Plasma density depletions in the post-sunset equatorial ionosphere, known as Equatorial Plasma Bubbles (EPBs), are thought to be a primary source of plasma irregularities on a scale from centimeters to kilometers that scatter radio waves at various wavelengths (e.g., Basu et al, 1978; McNamara et al, 2013; Saito et al, 2008; Tsunoda, 1980). Two-dimensional large-scale structures of the density depletion along the magnetic field lines have been studied by using 630-nm airglow imaging and GPS total electron content (TEC) mapping techniques (e.g., Otsuka et al, 2002; Takahashi et al, 2015). While plasma irregularities at low latitudes have been well studied by means of GPS scintillation (e.g.,Kintner et al, 2007), a two-dimensional observation of scintillation sources for L-band radio signals that are comparable to the horizontal structure of the density depletion is not yet available. A recent report shows that SAR and GPS scintillation were

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Discussion

Conclusion