A Turbulence-Driven Model for Heating and Acceleration of the Fast Wind in Coronal Holes

Verdini, A.; Velli, M.; Matthaeus, W. H.; Oughton, Sean; Dmitruk, P.

doi:10.1088/2041-8205/708/2/l116

Cited by 219 publications

(234 citation statements)

References 44 publications

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“…Spectral indices obtained from the power-law distribution indicates presence of Kolmogorov like turbulence (Kolmogorov 1941). Results presented in this study may be important in the theoretical modelling of coronal heating and acceleration of the fast solar wind in the coronal holes from the MHD turbulence Verdini et al 2010).…”

Section: Resultsmentioning

confidence: 86%

“…Recently, Cranmer & van Ballegooijen (2005); Cranmer et al (2007) and Verdini et al (2010) developed models of selfconsistent coronal heating and acceleration of fast solar wind. In these models, convective motions at the foot-points of magnetic flux tubes are assumed to generate wave-like fluctuations that propagate up into the extended corona, partially reflect back, develop into strong magnetohydrodynamic (MHD) turbulence, and then damped by an anisotropic turbulent cascade.…”

Section: Turbulence Power Spectra In the Polar Coronal Holementioning

confidence: 99%

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Observations of dissipation of slow magneto-acoustic waves in a polar coronal hole

Gupta

2014

A&A

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Aims. We focus on a polar coronal hole region to find any evidence of dissipation of propagating slow magneto-acoustic waves. Methods. We obtained time-distance and frequency-distance maps along the plume structure in a polar coronal hole. We also obtained Fourier power maps of the polar coronal hole in different frequency ranges in 171 Å and 193 Å passbands. We performed intensity distribution statistics in time domain at several locations in the polar coronal hole. Results. We find the presence of propagating slow magneto-acoustic waves having temperature dependent propagation speeds. The wavelet analysis and Fourier power maps of the polar coronal hole show that low-frequency waves are travelling longer distances (longer detection length) as compared to high-frequency waves. We found two distinct dissipation length scales of wave amplitude decay at two different height ranges (between 0-10 Mm and 10-70 Mm) along the observed plume structure. The dissipation lengths obtained at higher height range show some frequency dependence. Individual Fourier power spectrum at several locations show a power-law distribution with frequency whereas probability density function of intensity fluctuations in time show nearly Gaussian distributions. Conclusions. Propagating slow magneto-acoustic waves are getting heavily damped (small dissipation lengths) within the first 10 Mm distance. Beyond that waves are getting damped slowly with height. Frequency dependent dissipation lengths of wave propagation at higher heights may indicate the possibility of wave dissipation due to thermal conduction, however, the contribution from other dissipative parameters cannot be ruled out. Power-law distributed power spectra were also found at lower heights in the solar corona, which may provide viable information on the generation of longer period waves in the solar atmosphere.

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Section: Resultsmentioning

confidence: 86%

Section: Turbulence Power Spectra In the Polar Coronal Holementioning

confidence: 99%

Observations of dissipation of slow magneto-acoustic waves in a polar coronal hole

Gupta

2014

A&A

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“…The presence of these Alfvénic wave motions in the plumes may also go a long way to explaining the enigmatic plume-interplume 1 relationship of emission line widths (e.g., Hassler et al 1997;Wilhelm 2000). Finally, we speculate that because the (Alfvén) phase speed of the waves is significantly higher than the field-aligned upflows, the mass on the field line can lead to ideal reflecting conditions for the formation of a turbulent cascade of the Alfvénic wave energy into the plasma that is needed to accelerate the wind (e.g., Velli 1993;Matthaeus et al 1999;Verdini et al 2010). It is likely that precise spectroscopic imaging experiments (e.g., Tomczyk et al 2007) must be made in polar regions to accurately investigate the propagation and magnitude of Alfvén waves in the plume and inter-plume regions.…”

Section: Discussionmentioning

confidence: 86%

STEREO observations of quasi-periodically driven high velocity outflows in polar plumes

McIntosh¹,

Innes

Pontieu

et al. 2010

A&A

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Context. Plumes are one of the most ubiquitous features seen at the limb in polar coronal holes and are considered to be a source of high density plasma streams to the fast solar wind. Aims. We analyze STEREO observations of plumes and aim to reinterpret and place observations with previous generations of EUV imagers within a new context that was recently developed from Hinode observations. Methods. We exploit the higher signal-to-noise, spatial and temporal resolution of the EUVI telescopes over that of SOHO/EIT to study the temporal variation of polar plumes in high detail. We employ recently developed insight from imaging (and spectral) diagnostics of active region, plage, and quiet Sun plasmas to identify the presence of apparent motions as high-speed upflows in magnetic regions as opposed to previous interpretations of propagating waves.Results. In almost all polar plumes observed at the limb in these STEREO sequences, in all coronal passbands, we observe high speed jets of plasma traveling along the structures with a mean velocity of 135 km s −1 at a range of temperatures from 0.5-1.5 MK. The jets have an apparent brightness enhancement of ∼5% above that of the plumes they travel on and repeat quasi-periodically, with repeattimes ranging from five to twenty-five minutes. We also notice a very weak, fine scale, rapidly evolving, but ubiquitous companion of the plumes that covers the entire coronal hole limb. Conclusions. The observed jets are remarkably similar in intensity enhancement, periodicity and velocity to those observed in other magnetic regions of the solar atmosphere. They are multi-thermal in nature. We infer that the jets observed on the plumes are a source of heated mass to the fast solar wind. Further, based on the previous results that motivated this study, we suggest that these jets originated in the upper chromosphere.

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“…A primary goal of this study is to explore the potential unification of a wave-turbulence model that describes the heating and acceleration of the fast solar wind with one that describes heating in the low corona. To this end, we employ the same formulation for the evolution of low-frequency Alfvén wave turbulence as Lionello et al (2014b, a solar wind study), which is based on the work of Velli (1993) and most recently Verdini et al (2010). Invoking symmetry in the perpendicular direction to the mean field and the limit of low frequencies (ω → 0), the evolutionary equations can be expressed in terms of the scalar magnitude of the Elsässer variables, z ± = δu∓δb/ √ 4πρ, and take the following form:…”

Section: Wtd Heating Modelmentioning

confidence: 99%

“…For an open flux tube, such as those studied by (Verdini et al 2010;Lionello et al 2014b), heating strictly arises from the self-reflection of the outward propagating waves, while for a closed flux tube, interactions may arise both from self-reflection and via the counter-propagating waves launched at the opposite loop footpoint. In the latter case, the degree to which the fluctuations are correlated will determine their level of interaction and hence the dissipation rate.…”

Section: Wtd Heating Modelmentioning

confidence: 99%

Closed-Field Coronal Heating Driven by Wave Turbulence

Downs

Lionello

Mikić

et al. 2016

ApJ

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To simulate the energy balance of coronal plasmas on macroscopic scales, we often require the specification of the coronal heating mechanism in some functional form. To go beyond empirical formulations and to build a more physically motivated heating function, we investigate the wave-turbulence-driven (WTD) phenomenology for the heating of closed coronal loops. Our implementation is designed to capture the large-scale propagation, reflection, and dissipation of wave turbulence along a loop. The parameter space of this model is explored by solving the coupled WTD and hydrodynamic evolution in 1D for an idealized loop. The relevance to a range of solar conditions is also established by computing solutions for over one hundred loops extracted from a realistic 3D coronal field. Due to the implicit dependence of the WTD heating model on loop geometry and plasma properties along the loop and at the footpoints, we find that this model can significantly reduce the number of free parameters when compared to traditional empirical heating models, and still robustly describe a broad range of quiet-sun and active region conditions. The importance of the self-reflection term in producing relatively short heating scale heights and thermal nonequilibrium cycles is also discussed.

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A Turbulence-Driven Model for Heating and Acceleration of the Fast Wind in Coronal Holes

Cited by 219 publications

References 44 publications

Observations of dissipation of slow magneto-acoustic waves in a polar coronal hole

Observations of dissipation of slow magneto-acoustic waves in a polar coronal hole

STEREO observations of quasi-periodically driven high velocity outflows in polar plumes

Closed-Field Coronal Heating Driven by Wave Turbulence

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