Type II radio bursts: 1. New entirely analytic formalism for the electron beams, Langmuir waves, and radio emission

Abstract

[1] Type II radio bursts drift in frequency as shock waves and coronal mass ejections (CMEs) move through the Sun's corona and the solar wind. This paper extends the theoretical models for type II radio bursts of Knock et al. (2001Knock et al. ( , 2003, Knock and Cairns (2005), Cairns and Knock (2006) and Schmidt and Gopalswamy (2008). The theory treats the acceleration of electrons at the shock, formation of electron beams, growth of Langmuir waves, and conversion of Langmuir energy into radiation. An entirely analytical and more general formalism is developed, which includes kappa electron velocity distribution functions for the plasma electrons and the shock-reflected electron beam. The radiation model also includes the plateauing of the electron beam, which releases energy for the Langmuir waves. This paper has two parts. First, the new entirely analytical formalism is presented. Second, first numerical results for synthetic radio images and synthetic dynamic spectra are discussed, gained by applying our radiation model to MHD simulations of a shock driven by a CME. The results are compared with earlier analytic approaches. This work is also applicable to other shock-related emissions in space and astrophysical plasmas.Citation: Schmidt, J. M., and I. H. Cairns (2012), Type II radio bursts: 1. New entirely analytic formalism for the electron beams, Langmuir waves, and radio emission,

Type II solar radio bursts predicted by 3‐D MHD CME and kinetic radio emission simulations

“…Both were associated with multiple days of strong space weather activity (see http://www.swpc.noaa.gov/weekly/2011_WeeklyPDF/prf1851.pdf and http://www.swpc.noaa.gov/weekly/2012_WeeklyPDF/prf1906.pdf). This agreement strongly supports the validity of the type II theory [ Knock et al , , , ; Knock and Cairns , ; Cairns and Knock , ; Florens et al , ; Schmidt and Cairns , , ] and the quality of the CME simulations. It also opens up a near‐term capability for the extraction of CME properties from radio data combined with simulations for the refinement of space weather predictions at Earth and elsewhere.…”

“…In this paper a detailed quantitative test of state‐of‐the‐art type II theory with event‐specific 3‐D CME and shock predictions is carried out. This test combines the radio theory developed at the University of Sydney [ Knock et al , , , ; Knock and Cairns , ; Cairns and Knock , ; Florens et al , ; Schmidt and Cairns , , ] with simulations of the University of Michigan's Block‐Adaptive‐Tree‐Solarwind‐Roe‐Upwind‐Scheme (BATS‐R‐US) magnetohydrodynamic (MHD) code [ Powell et al , ; Roussev et al , , ; Tôth et al , ] for the 15 February 2011 and 7 March 2012 type IIs and CMEs, going beyond a first short application to the 15 February 2011 event [ Schmidt et al , ]. Data from multiple ground (Wilcox, Learmonth) and space (ACE, STEREO, and Wind) platforms are used to develop models for the background corona and CME initiation used in the BATS‐R‐US code.…”

Quantitative prediction of type II solar radio emission from the Sun to 1 AU

“…The spatially varying shock normal and the upstream magnetic field and plasma parameters are taken from the underlying BATS-R-US simulation. The plasma and electron beam parameters are then used to analytically calculate the frequency and radiated power per unit volume for these radio emission processes [Schmidt and Cairns, 2012;Robinson and Cairns, 1998;Knock et al, 2001]. Sufficiently, intense Langmuir waves undergo electrostatic decay into backscattered Langmuir waves and ion acoustic waves.…”

Large-scale Globally Propagating Coronal Waves

“…Type II radio emission is generated by the conversion of enhanced Langmuir waves to electromagnetic waves, therefore, the radiation is emitted at the fundamental and the first harmonic of the Langmuir frequency, also referred to as electron plasma frequency pe . The enhanced Langmuir turbulence is thought to be caused by energy input due to electrons that are accelerated by the shock wave (see e.g., Schmidt and Cairns, 2012, and references therein). …”