Nanodust dynamics during a coronal mass ejection

Andrzej Czechowski,Jens Kleimann

doi:10.5194/angeo-35-1033-2017

Andrzej Czechowski, Jens Kleimann

Open Access

https://doi.org/10.5194/angeo-35-1033-2017

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Abstract

Abstract. The dynamics of nanometer-sized grains (nanodust) is strongly affected by electromagnetic forces. High-velocity nanodust was proposed as an explanation for the voltage bursts observed by STEREO. A study of nanodust dynamics based on a simple time-stationary model has shown that in the vicinity of the Sun the nanodust is trapped or, outside the trapped region, accelerated to high velocities. We investigate the nanodust dynamics for a time-dependent solar wind and magnetic field configuration in order to find out what happens to nanodust during a coronal mass ejection (CME). The plasma flow and the magnetic field during a CME are obtained by numerical simulations using a 3-D magnetohydrodynamic (MHD) code. The equations of motion for the nanodust particles are solved numerically, assuming that the particles are produced from larger bodies moving in near-circular Keplerian orbits within the circumsolar dust cloud. The charge-to-mass ratios for the nanodust particles are taken to be constant in time. The simulation is restricted to the region within 0.14 AU from the Sun. We find that about 35 % of nanodust particles escape from the computational domain during the CME, reaching very high speeds (up to 1000 km s−1). After the end of the CME the escape continues, but the particle velocities do not exceed 300 km s−1. About 30 % of all particles are trapped in bound non-Keplerian orbits with time-dependent perihelium and aphelium distances. Trapped particles are affected by plasma ion drag, which causes contraction of their orbits.

Highlights

The vicinity of the Sun is a possible source region of nanometer-sized dust grains produced by collisional fragmentation of larger dust grains or released from comets (Mann et al, 2007; Mann and Czechowski, 2012; Ip and Yan, 2012)
We study the effect of a coronal mass ejection (CME) on nanodust dynamics in the vicinity of the Sun by numerical simulation
The mass of the CME as described by the model is about 5.7 × 1013 kg, which puts the CME in the moderate to strong class

Summary

Introduction

The vicinity of the Sun is a possible source region of nanometer-sized dust grains (nanodust) produced by collisional fragmentation of larger dust grains or released from comets (Mann et al, 2007; Mann and Czechowski, 2012; Ip and Yan, 2012). Because of high charge-to-mass ratio, the effect of electromagnetic forces on nanodust is much stronger than for larger grains. A dedicated study of the dust dynamics near the Sun (Krivov et al, 1998) was restricted to larger grains. Czechowski and Mann (2010, 2011a, 2012) studied the nanodust dynamics in a simplified model of solar wind and solar magnetic field by assuming a purely radial, timeand distance-independent solar wind velocity and a Parker spiral form of the magnetic field. It was found that, depending on the initial position and velocity, the nanodust particles can either be trapped near the Sun (in non-Keplerian orbits strongly affected by electromagnetic forces) or escape to large distances. The escaping particles can be accelerated to high speeds comparable to those of the solar wind

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