EDP Sciences
Free access
Issue
A&A
Volume 454, Number 3, August II 2006
Page(s) 983 - 988
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20065130


A&A 454, 983-988 (2006)
DOI: 10.1051/0004-6361:20065130

Simulated enhancement of solar type II radio bursts during the collision of two shocks associated with coronal mass ejections

J. I. Sakai1, T. Mori1, S. Saito1, Y. Tanaka1 and H. Aurass2

1  Laboratory for Plasma Astrophysics, Faculty of Engineering, University of Toyama, 3190, Gofuku, Toyama 930-8555, Japan
    e-mail: sakaijun@eng.u-toyama.ac.jp
2  Astrophysical Institute Potsdam, An der Sternwarte 16a, 14482 Potsdam, Germany

(Received 2 March 2006 / Accepted 3 April 2006 )

Abstract
Aims.We investigate how solar type II radio bursts can be enhanced when two fast magnetosonic shocks associated with coronal mass ejections (CMEs) collide. This work was motivated by recent observations showing that the radio signature is in the form of intense continuum-like radio emission following an interplanetary type II burst, when a fast CME overtakes a slow CME.
Methods. We used a 2D3V fully relativistic, electromagnetic particle-in-cell (PIC) simulation.
Results. We found that during the collision between a fast shock with Alfvén Mach $M_{\rm A}=3$ and a slow wave with Alfvén Mach $M_{\rm A}=0.75$, the radio emission with a broad band can be enhanced with an amplitude about ten times larger than for the undisturbed type II burst. We also found that when a fast shock with Alfvén Mach $M_{\rm A}=3$ overtakes a slow shock with Alfvén Mach $M_{\rm A}=1.5$, the enhancement of the radio emission is about five times greater than the undisturbed type II burst.


Key words: plasmas -- radiation mechanisms: non-thermal -- shock waves -- methods: numerical -- Sun: radio radiation



© ESO 2006