Ionospheric S4 Scintillations from GNSS Radio Occultation (RO) at Slant Path

Dong L Wu

doi:10.3390/rs12152373

Abstract

Ionospheric scintillation can significantly degrade the performance and the usability of space-based communication and navigation signals. Characterization and prediction of ionospheric scintillation can be made from the Global Navigation Satellite System (GNSS) radio occultation (RO) technique using the measurement from a deep slant path where the RO tangent height (ht) is far below the ionospheric sources. In this study, the L–band S4 from the RO measurements at ht = 30 km is used to infer the amplitude scintillation on the ground. The analysis of global RO data at ht = 30 km shows that sporadic–E (Es), equatorial plasma bubbles (EPBs), and equatorial spread–F (ESF) produce most of the significant S4 enhancements, although the polar S4 is generally weak. The enhanced S4 is a strong function of local time and magnetic dip angle. The Es–induced daytime S4 tends to have a negative correlation with the solar cycle at low latitudes but a positive correlation at high latitudes. The nighttime S4 is dominated by a strong semiannual variation at low latitudes.

Highlights

Irregular structures and variations in plasma density often cause scintillation of radio wave communication in a transionospheric link
Because changes of the refractive index are proportional to electron density gradient, as well as to the inverse of radio wavelength squared, ionospheric scintillations are strongly scale and frequency–dependent
Because ionospheric scintillations can significantly degrades the performance of transionospheric communication and navigation systems on the ground, a considerable amount of efforts have been devoted to connect the L–band S4 scintillations observed from space to those experienced on the ground [17,18,19,20,21,22]

Summary

Introduction

Irregular structures and variations in plasma density often cause scintillation of radio wave communication in a transionospheric link. Because ionospheric scintillations can significantly degrades the performance of transionospheric communication and navigation systems on the ground, a considerable amount of efforts have been devoted to connect the L–band S4 scintillations observed from space to those experienced on the ground [17,18,19,20,21,22]. These studies show satellite in–situ measurements tend to yield a better correlation with the ground–based scintillations than the RO–based measurements. The scintillation measurements from the deep ht share a similar viewing geometry as a ground–based receivers in terms of sensitivity to vertically–tilted density gradients and small–scale horizontal structures

Data and Method

S4 Calculation and Aggregation

RO Slant Views and Smearing Effects on Scintillations

Polar Scintillations

Findings

Implication for Scintillation Nowcast