Plasma Dynamics Above Solar Flare Soft X-Ray Loop Tops

Doschek, G. A.; McKenzie, D. E.; Warren, Harry P.

doi:10.1088/0004-637x/788/1/26

Cited by 47 publications

(54 citation statements)

References 50 publications

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“…We can use Equations (12) and (13) to express the effective viscosity turb n in terms of two measurable quantities such as u turb and l turb . A crude estimate of the dimensionless constant in » -(for the value of l turb used in our simulations), which is well within the range reported by Doschek et al (2014) from Hinodeobservations. It is important to recall that other effects besides turbulence might contribute to reduce the instability growth rate.…”

Section: Discussionsupporting

confidence: 86%

“…One of them is the apparent development of the KH instability as some CMEs expand in the ambient corona, as shown by AIA/SDOimages (Foullon et al 2011;Ofman & Thompson 2011;Foullon et al 2013). The second one is that the coronal plasma seems to be in a turbulent state, as evidenced by the nonthermal broadening of coronal spectral lines measured from EIS/Hinodedata (Doschek et al 2008(Doschek et al , 2014Brooks & Warren 2011;Tian et al 2012).…”

Section: Discussionmentioning

confidence: 99%

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Simulations of the Kelvin–helmholtz Instability Driven by Coronal Mass Ejections in the Turbulent Corona

Gomez

DeLuca

Mininni

2016

ApJ

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Recent high-resolution Atmospheric Imaging Assembly/Solar Dynamics Observatoryimages show evidence of the development of the Kelvin-Helmholtz (KH) instability, as coronal mass ejections (CMEs) expand in the ambient corona. A large-scale magnetic field mostly tangential to the interface is inferred, both on the CME and on the background sides. However, the magnetic field component along the shear flow is not strong enough to quench the instability. There is also observational evidence that the ambient corona is in a turbulent regime, and therefore the criteria for the development of the instability are a priori expected to differ from the laminar case. To study the evolution of the KH instability with a turbulent background, we perform three-dimensional simulations of the incompressible magnetohydrodynamic equations. The instability is driven by a velocity profile tangential to the CME-corona interface, which we simulate through a hyperbolic tangent profile. The turbulent background is generated by the application of a stationary stirring force. We compute the instability growth rate for different values of the turbulence intensity, and find that the role of turbulence is to attenuate the growth. The fact that KH instability is observed sets an upper limit on the correlation length of the coronal background turbulence.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Simulations of the Kelvin–helmholtz Instability Driven by Coronal Mass Ejections in the Turbulent Corona

Gomez

DeLuca

Mininni

2016

ApJ

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“…Doschek et al (2014), for example, only measured values of 20-60 km s −1 in Figures 5-7, the trend is not a function of temperature within an AR core. Rather, it is a trend between different AR cores.…”

Section: Summary and Discussionmentioning

confidence: 84%

Measurements of Non-Thermal Line Widths in Solar Active Regions

Brooks

Warren

2016

ApJ

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Spectral line widths are often observed to be larger than can be accounted for by thermal and instrumental broadening alone. This excess broadening is a key observational constraint for both nanoflare and wave dissipation models of coronal heating. Here we present a survey of non-thermal velocities measured in the high temperature loops (1-4 MK) often found in the cores of solar active regions. This survey of Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) observations covers 15 non-flaring active regions that span a wide range of solar conditions. We find relatively small non-thermal velocities, with a mean value of 17.6 ± 5.3 km s −1 , and no significant trend with temperature or active region magnetic flux. These measurements appear to be inconsistent with those expected from reconnection jets in the corona, chromospheric evaporation induced by coronal nanoflares, and Alfvén wave turbulence models. Furthermore, because the observed non-thermal widths are generally small, such measurements are difficult and susceptible to systematic effects.

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“…For example, high-resolution soft X-ray images from the TRACE and Hinode satellites have confirmed that reconnection of magnetic fields in the upper atmosphere of the Sun plays a key role in producing the explosive ejection of solar material outward into the solar system (Goff et al 2005;Doschek et al 2014). Such eruptive events, known as coronal mass ejections or CMEs, are responsible for major magnetic storms on Earth (Webb et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Magnetospheric Multiscale Overview and Science Objectives

et al. 2015

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Magnetospheric Multiscale (MMS), a NASA four-spacecraft constellation mission launched on March 12, 2015, will investigate magnetic reconnection in the boundary regions of the Earth's magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. The most important goal of MMS is to conduct a definitive experiment to determine what causes magnetic field lines to reconnect in a collisionless plasma. The significance of the MMS results will extend far beyond the Earth's magnetosphere because reconnection is known to occur in interplanetary space and in the solar corona where it is responsible for solar flares and the disconnection events known as coronal mass ejections. Active research is also being conducted on reconnection in the laboratory and specifically in magnetic-confinement fusion devices in which it is a limiting factor in achieving and maintaining electron temperatures high enough to initiate fusion. Finally, reconnection is proposed as the cause of numerous phenomena throughout the universe such as comet-tail disconnection events, magnetar flares, supernova ejections, and dynamics of neutron-star accretion disks. The MMS mission design is focused on answering specific questions about reconnection at the Earth's magnetosphere. The prime focus of the mission is on determining the kinetic processes occurring in the electron diffusion region that are responsible for reconnection and that determine how it is initiated; but the mission will also place that physics into the context of the broad spectrum of physical processes associated with reconnection. Connections to other disciplines such as solar physics, astrophysics, and laboratory plasma physics are expected to be made through theory and modeling as informed by the MMS results.

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Plasma Dynamics Above Solar Flare Soft X-Ray Loop Tops

Cited by 47 publications

References 50 publications

Simulations of the Kelvin–helmholtz Instability Driven by Coronal Mass Ejections in the Turbulent Corona

Simulations of the Kelvin–helmholtz Instability Driven by Coronal Mass Ejections in the Turbulent Corona

Measurements of Non-Thermal Line Widths in Solar Active Regions

Magnetospheric Multiscale Overview and Science Objectives

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