Testing a theory for type II radio bursts from the Sun to near 0.5 AU

[摘要] Type II solar radio bursts have resisted detailed explanation for over 60 years despite being the archetype for collective radio emission associated with shocks. Type II bursts are important because they involve fundamental physics and because most large space weather events at Earth are associated with large, fast, coronal mass ejections (CMEs) and so with type II bursts. Here we present strong evidence for the accurate and quantitative simulation of a type II burst from the deep corona (near 3 solar radii) to near 0.5 AU. The event was observed by the widely separated STEREO A and B spacecraft between 29 November and 1 December 2013. To do so we combine data-driven three-dimensional magnetohydrodynamic simulations (the BATS-R-US code) for the CME and plasma background with an analytic quantitative kinetic model for electron reflection at the shock, transfer of electron energy into Langmuir waves and radio emission, and propagation of radiation to an arbitrary observer. The intensities and frequencies of the radio emissions vary by factors ≈ 104and ≈ 102, respectively. The theory predicts the intensities, frequencies, and timings of the multiple islands of type II emission very well, with the theory typically in error by less than a factor of 10, 20%, and less than an hour, respectively, for both STEREO A and B. This agreement is strong evidence for the type II theory itself and for accurate prediction by BATS-R-US, when carefully initialised with available data, of the background plasma and magnetic field configurations and of the CME's properties and motion.

[发布机构] School of Physics, University of Sydney, Sydney; NSW; 2006, Australia^1

[效力级别] 天文学 [学科分类] 天文学(综合)

[关键词] Accurate prediction;Coronal mass ejection;Fundamental physics;Magnetic field configurations;Magnetohydrodynamic simulations;Quantitative kinetics;Quantitative simulation;Solar radio bursts