Nonlinear electromagnetic waves and spherical arc-polarized waves in space plasmas

Abstract

We review observations of nonlinear plasma waves detected by interplanetary spacecraft. For this paper we will focus primarily on the phase-steepened properties of such waves. Plasma waves at comet Giacobini - Zinner measured by the international cometary explorer (ICE), at comets Halley and Grigg - Skjellerup measured by Giotto, and interplanetary Alfvén waves measured by Ulysses, will be discussed and intercompared. Owing to the page limitations of this paper we will keep the cometary wave discussion brief (but references for the interested reader will be provided), and we will focus more on the recent Ulysses observations of phase-steepened Alfvén waves. For the latter, classical `interplanetary rotational discontinuities' are explained as phase-steepened edges of Alfvén waves. Both the Alfvén waves and their phase-steepened edges will be shown to be arc-polarized. A method of determination of the direction of propagation of these waves will be discussed.