Imprints of coronal temperature disturbances on type III bursts

Abstract

The electron temperature T e and ion temperature T i in the corona vary with time and location, due to transient and persistent activity on the Sun. The effects of spatially localized disturbances in T e and T i on coronal type III radio bursts are simulated. The disturbances are superimposed on monotonically varying temperature backgrounds and arise from spatially confined solar activity, Qualitatively and quantitatively different imprints are found on the curve of the maximum flux versus frequency of type III bursts, because of the disturbances in T e and T i . The results indicate that nonthermal coronal type III bursts offer a new tool to probe and distinguish between spatially localized structures of T e and T i along the paths of type III beams. Furthermore, localized temperature disturbances may be responsible for some fine structures in type III bursts, e.g., striae in type IIIb bursts in the presence of multiple, localized temperature disturbances.

Plasma Emission by Nonlinear Electromagnetic Processes

“…The first theory of plasma emission and type III radio bursts was proposed in 1958 by Ginzburg & Zheleznyakov (1958), though their original theory has undergone a considerable amount of modifications and improvements over the decades (Tsytovich 1967;Kaplan & Tsytovich 1968;Zheleznyakov & Zaitsev 1970a;Melrose 1982Melrose , 1987Goldman & Dubois 1982;Cairns 1987;Robinson & Cairns 1998a;Li et al 2005aLi et al , 2005bLi et al , 2006aLi et al , 2006bLi et al , 2008aLi et al , 2008bLi et al , 2009Li et al , 2010Li et al , 2011aLi et al , 2011bLi et al , 2011c. Essentially, the standard paradigm of plasma emission first involves energetic electrons produced at the solar active region during the flare.…”

“…Such an elaborate process can, in principle, be demonstrated on the basis of EM weak turbulence theory,-the fundamental equations thereof and their derivation can be found, e.g., in Yoon (2006), Yoon et al (2012a), and Ziebell et al (2014b). Indeed, over the past several decades, the physics of plasma emission was discussed within the framework of reduced or partial EM weak turbulence theory (Li et al 2005a(Li et al , 2005b(Li et al , 2006a(Li et al , 2006b(Li et al , 2008a(Li et al , 2008b(Li et al , 2009(Li et al , 2010(Li et al , 2011a(Li et al , 2011b(Li et al , 2011cSchmidt & Cairns 2012a. However, the complete numerical solution of the entire set of EM weak turbulence equations has not been done until quite recently, when Ziebell et al (2014a) numerically solved the complete equations of EM weak turbulence theory for the first time.…”

“…We should note, however, that the above comments are not meant to diminish the value and importance of reduced theories. Some of these theories, especially those from the University of Sydney (Li et al 2005a(Li et al , 2005b(Li et al , 2006a(Li et al , 2006b(Li et al , 2008a(Li et al , 2008b(Li et al , 2009(Li et al , 2010(Li et al , 2011a(Li et al , 2011b(Li et al , 2011cSchmidt & Cairns 2012a, have advanced to the point where simple yet reliable plasma emission models are incorporated into macroscopic models so as to yield global-kinetic models for both type II and type III radio bursts with predictive capabilities. Nevertheless, since reduced models are based upon various assumptions, it is difficult to quantitatively assess the importance of various physical processes.…”

Plasma Emission by Counter-Streaming Electron Beams

“…The general consensus is that the radiation emission mechanism responsible for type-III bursts is plasma emission, first proposed by Ginzburg & Zheleznyakov (1958) and subsequently refined over the intervening decades (Tsytovich 1967;Kaplan & Tsytovich 1968;Zheleznyakov & Zaitsev 1970a;Melrose 1982, 1987, Cairns 1987a, 1987b, 1987cGoldman & Dubois 1982;Robinson & Cairns 1998a, 1998b, 1998cLi et al 2005aLi et al , 2005bLi et al , 2006aLi et al , 2006bLi et al , 2008aLi et al , 2008bLi et al , 2009Li et al , 2010Li et al , 2011aLi et al , 2011bLi et al , 2011cRatcliffe et al 2012;Reid & Ratcliffe 2014;Ziebell et al 2014Ziebell et al , 2015. In addition to theory, full particle simulations of the plasma emission process have also been carried out (Kasaba et al 2001;Karlický & Vandas 2007;Rhee et al 2009aRhee et al , 2009bUmeda 2010;Ganse et al 2012aGanse et al , 2012b.…”

Solar Type Iii Radio Bursts Modulated by Homochromous Alfvén Waves

“…In the context of plasma emission, several causes for the intermittent emissions in type III bursts were suggested. They are coronal density irregularities (Takakura & Yousef 1975), modulational instability (Smith & de La Noe 1976), and coronal temperature disturbances (Li et al 2010). However, these intermittent emissions have never been explained in terms of ECME.…”