Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals

A G Pavelyev,V N Gubenko,Y Kuleshov,K Zhang,C S Wang,A A Pavelyev,J Wickert,T Schmidt,Y A Liou

doi:10.5194/amt-5-1-2012

Abstract

Abstract. By using the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data, a description of different types of the ionospheric impacts on the RO signals at the altitudes 30–90 km of the RO ray perigee is given and compared with the results of measurements obtained earlier in the satellite-to-Earth communication link at frequency 1.5415 GHz. An analytical model is introduced for describing propagation of radio waves in a stratified medium consisting of sectors with spherically symmetric refractivity distribution. This model gives analytical expressions for the phase, bending angle, and refractive attenuation of radio waves and is applied to the analysis of radio wave propagation phenomena along an extended path including the atmosphere and two parts of the ionosphere. The model explains significant amplitude and phase variations at altitudes 30–90 km of the RO ray perigee and attributes them to inclined ionospheric layers. Based on this analytical model, an innovative technique is introduced to locate layers in the atmosphere and ionosphere. A necessary and sufficient criterion is obtained for a layer to be located at the RO ray perigee. This criterion gives both qualitative and quantitative estimation of the displacement of an ionospheric and/or atmospheric layer from the RO ray perigee. This is important, in particular, for determining the location of wind shears and directions of the internal wave propagation in the lower ionosphere, and, possibly, in the atmosphere.

Highlights

An analytical model is introduced that accounts for the local mechanism of multiple-radio occultation (RO) ionospheric phenomena and involves horizontal gradients in the ionosphere
As applied to the RO data analysis, the analytical model associates the Coherent variations of the eikonal and intensity of the RO signals at 30–90 km altitude of the RO ray perigee to the contribution of inclined layers in the ionosphere
The quality of CHAllenge Minisatellite Payload (CHAMP) RO data and the analytical model have demonstrated the important application of a comparative analysis of the amplitude and phase channels of satellite radio-holograms to classifying the ionospheric influence on the RO signals

Summary

Introduction

Phenomenon of strong amplitude and phase frequency dependent variations in the RO signals is often observed within the altitudes of the RO ray perigee h between 30 and 90 km above the main part of the neutral atmosphere and below the E-layer of the ionosphere This effect is interesting for investigating propagation of radio waves and communication in the satellite-to-satellite links. The goals of this paper are (i) to describe different kinds of ionospheric influence on the GPS RO signals within the altitudes of h between 30 and 90 km, and to compare them with the noisy (C-type) and regular (S-type) scintillations detected earlier by Karasawa et al (1985) in the satellite-toEarth communication link; (ii) to present an analytical model for the refractive attenuation and excess phase path (eikonal) of electromagnetic waves in locally spherical symmetric media; and (iii) to identify the contributions and to measure parameters of the inclined plasma layers by analyzing the CHAMP RO experimental data.

Types of ionospheric influence on the CHAMP RO signal

Identification and location of plasma layers

Conclusions