Waves In Solar Corona Research Articles

THE EFFECT OF TURBULENCE INTERMITTENCE ON THE EMISSION OF SOLAR ENERGETIC PARTICLES BY CORONAL AND INTERPLANETARY SHOCKS

Major solar energetic particle events are associated with shock waves in solar corona and solar wind. Fast scattering of charged particles by plasma turbulence near the shock wave increases the efficiency of the particle acceleration in the shock, but prevents particles from escaping ahead of the shock. However, the turbulence energy levels in neighboring magnetic tubes of solar wind may differ from each other by more than one order of magnitude. We present the first theoretical study of accelerated particle emission from an oblique shock wave propagating through an intermittent turbulence background that consists of both highly turbulent magnetic tubes, where particles are accelerated, and quiet tubes, via which the accelerated particles can escape to the non-shocked solar wind. The modeling results imply that the presence of the fast transport channels penetrating the shock and cross-field transport of accelerated particles to those channels may play a key role in high-energy particle emission from distant shocks and can explain the prompt onset of major solar energetic particle events observed near the Earth's orbit.

Properties of Alfvén waves in the outer solar corona from two-station faraday rotation observations

Faraday rotation fluctuations (FRF) of S-band polarized radio signals observed during the 1981 solar conjunction of the Helios spacecraft are used to investigate Alfvén waves in the solar corona. The occultation geometry enabled coronal radio sounding of the heliographic equatorial region at solar offset distances from 3–12 R⊙. Spectral analysis was performed with the FRF data to determine the turbulence regime of the magnetic field irregularities. Cross-correlation functions of signals received simultaneously at two widelyseparated ground stations were used to obtain the propagation speed of Alfvén waves traversing the ray paths.

Nonlinear Dynamics and Chaos in Space Plasmas

The theory and observation of nonlinear wave coupling phenomena in solar-system plasmas are reviewed. Rocket and satellite observations have provided evidence of nonlinear wave interactions in space plasmas, in particular, in relation to the generation and propagation of radio waves in solar corona, interplanetary medium and Earth’s magnetosphere. These radio waves represent the electromagnetic signature of solar-terrestrial coupling and are useful for forecasting and monitoring of space weather. Nonlinear wave-wave coupling in plasmas can be modeled as a dynamical system of coupled oscillators involving one, two or higher-order wave triplets. For a three-wave dissipative system, the temporal transition from order to chaos may evolve via period doubling or intermittence. For a four-wave Hamiltonian system involving two coupled wave triplets, the spatiotemporal transition from order to chaos is analyzed using the concepts of stable and unstable homogeneous manifolds. Plasma dynamics is governed by a variety of wave motions resulting from the collective electrodynamic interactions involving plasma fields and plasma particles. Nonlinear wave-wave coupling in plasmas can occur due to the growth of parametric instabilities. In this paper, we present an overview of theoryand observation of nonlinear mode coupling in space plasmas. In §2 we discuss the theoryof nonlinear interaction involving a single wave triplet in the presence of source and dissipation. We consider the transition from order to low-dimensional temporal chaos. In § 3w e discuss the theoryof nonlinear interaction involving two wave triplets in the absence of source and dissipation. We treat the transition from order to high-dimensional spatiotemporal chaos. Before discussing the theorylet us first summarize some recent observational evidence of nonlinear wave-wave interactions in the solar system. Comprehensive reviews of this topic are given in Refs. 1) and 2). Radio waves provide the electromagnetic signature of solar-terrestrial relation and serve as a tool to forecast and monitor the space weather. The radio emis