Wave and plasma measurements and GPS diagnostics of the main ionospheric trough as a hybrid method used for Space Weather purposes

H Rothkaehl,I Stanislawska,J.-J Berthelier,J Błęcki,A Krakowski,J.-P Lebreton,M Parrot

doi:10.5194/angeo-26-295-2008

Abstract

Abstract. The region of the main ionospheric trough is a unique region of the ionosphere, where different types of waves and instabilities can be generated. This region of the ionosphere acts like a lens, focusing a variety of indicators from the equator of plasmapause and local ionospheric plasma. This paper reports the results of monitoring the mid-latitude trough structure, dynamics and wave activity. For these purposes, the data gathered by the currently-operating DEMETER satellite and past diagnostics located on IK-19, Apex, and MAGION-3 spacecraft, as well as TEC measurements were used. A global-time varying picture of the ionospheric trough was reconstructed using the sequence of wave spectra registered and plasma measurements in the top-side ionosphere. The authors present the wave activity from ULF frequency band to the HF frequency detected inside the trough region and discuss its properties during geomagnetic disturbances. It is thought that broadband emissions are correlated with low frequency radiation, which is excited by the wave-particle interaction in the equatorial plasmapause and moves to the ionosphere along the geomagnetic field line. In the ionosphere, the suprathermal electrons can interact with these electrostatic waves and excite electron acoustic waves or HF longitudinal plasma waves. Furthermore, the electron density trough can provide useful data on the magnetosphere ionosphere dynamics and morphology and, in consequence, can be used for Space Weather purposes.

Highlights

The mid-latitude trough region is one of most important regions in the ionosphere, as a deeper understanding of the physical processes occurring in this region can enhance knowledge about ionosphere-magnetosphere coupling
Consider in situ plasma, wave diagnostics and the ground network of different diagnostic instruments and TEC data derived from the commercial GPS network
Horizontal convection, field-aligned plasma transport, changes in the electric and magnetic fields, precipitation of electrons, interaction of ionospheric plasma with neutral components and recombination and ionisation processes and wave particle interactions in the ionosphere and inner magnetosphere are responsible for main ionospheric trough formation

Summary

Introduction

The mid-latitude trough region is one of most important regions in the ionosphere, as a deeper understanding of the physical processes occurring in this region can enhance knowledge about ionosphere-magnetosphere coupling. Since the first trough features registration, a number of different empirical equations which express the position of the main ionospheric trough in functions of local time and geomagnetic indexes were elaborated (Rycroft and Burnell, 1970; Tulunay, 1972; Werner and Proelss, 1997; Bradley et al, 1998; Karpatchev et al, 2003) All of these models are incomplete, due to the limitation of temporal and spatial measurement resolution. The current in situ wave and particle measurements performed on the DEMETER satellite and on the GPS diagnostics provide new challenges to describe the dynamics and detailed structures of the main ionopsheric trough These analyses give new data on wave particle interaction in the topside ionosphere and could be very helpful for improving the understanding of the ionosphere-magnetosphere coupling processes. The proposed mechanism of intensification of broad band VLF and HF frequency emissions during strong geomagnetic disturbances could show the links between the topside ionosphere and the remote plasmapause region

Diagnostics techniques and instrumentations

Growth phase of geomagnetic storm

Main phase

Recovery phase

Conclusion