A basal contribution from p-modes to the Alfvénic wave flux in the Sun’s corona

Morton, R. J.; Weberg, M. J.; McLaughlin, James

doi:10.1038/s41550-018-0668-9

Cited by 85 publications

(104 citation statements)

References 38 publications

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“…Random synthetic time-series are generated following the method suggested by Timmer & Koenig (1995), where the power spectra of the time-series is designed to match typical values from observed coronal power spectra (Morton et al 2016;Morton et al 2019). The time-series are produced in pairs, one representing the outward waves and the other series having a power spectra multiplied by a frequency dependent exponential term to represent the damping of the inward waves.…”

Section: Appendixmentioning

confidence: 99%

Damping of Propagating Kink Waves in the Solar Corona

Tiwari

Morton

Régnier

et al. 2019

ApJ

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Alfvénic waves have gained renewed interest since the existence of ubiquitous propagating kink waves were discovered in the corona. It has long been suggested that Alfvénic waves play an important role in coronal heating and the acceleration of the solar wind. To this effect, it is imperative to understand the mechanisms that enable their energy to be transferred to the plasma. Mode conversion via resonant absorption is believed to be one of the main mechanisms for kink wave damping, and is considered to play a key role in the process of energy transfer. This study examines the damping of propagating kink waves in quiescent coronal loops using the Coronal Multi-channel Polarimeter (CoMP). A coherencebased method is used to track the Doppler velocity signal of the waves, enabling us to investigate the spatial evolution of velocity perturbations. The power ratio of outward to inward propagating waves is used to estimate the associated damping lengths and quality factors. To enable accurate estimates of these quantities, we provide the first derivation of a likelihood function suitable for fitting models to the ratio of two power spectra obtained from discrete Fourier transforms. Maximum likelihood estimation is used to fit an exponential damping model to the observed variation in power ratio as a function of frequency. We confirm earlier indications that propagating kink waves are undergoing frequency dependent damping. Additionally, we find that the rate of damping decreases, or equivalently the damping length increases, for longer coronal loops that reach higher in the corona.

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Section: Appendixmentioning

confidence: 99%

Damping of Propagating Kink Waves in the Solar Corona

Tiwari

Morton

Régnier

et al. 2019

ApJ

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“…This restriction could be eliminated if we apply magnetoseismology to more ubiquitous and continuous oscillations or waves in the corona. At least two types of such oscillations/waves are known to exist in the corona: the decayless/persistent standing transverse waves in coronal loops observed through extreme-ultraviolet (EUV) imaging and spectroscopic observations [43][44][45][46], and the pervasive propagating transverse waves observed with the Coronal Multi-channel Polarimeter (CoMP, [47]) [48][49][50][51][52][53]. These ubiquitous oscillations/waves, especially the latter, are potentially important for continuous diagnostics of coronal magnetic field [51,54].…”

Section: Introductionmentioning

confidence: 99%

Mapping the magnetic field in the solar corona through magnetoseismology

Yang

Tomczyk

Morton

et al. 2020

Sci. China Technol. Sci.

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of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe xiii 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere.

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“…There are some differences between the location of the wedge and its exact shape. However, this variation can likely be attributed to differences in the coronal magnetic field and plasma conditions, which leads to different wave properties (e.g, Morton et al 2016Morton et al , 2019.…”

Section: Observationsmentioning

confidence: 99%

“…where periods (hence, ω's) are chosen from the observed log-normal distribution (Thurgood et al 2014;Weberg et al 2018;Morton et al 2015Morton et al , 2019. The magnitude of U i and V i are randomly chosen from a uniform distribution of…”

Section: Wave Excitationmentioning

confidence: 99%

“…These authors reported waves with amplitudes of ∼ 20 km s −1 , suggesting that they are capable of providing the energy flux of 100-200 W m −2 to accelerate fast solar wind and balance radiative losses in quiet corona. The coronal counterpart to these propagating Alfvénic waves was observed using Doppler velocity data (Tomczyk et al 2007(Tomczyk et al , 2008Tomczyk & McIntosh 2009;Morton et al 2015) from the Coronal Multi-Channel Polarimeter (CoMP Tomczyk et al 2008), and through direct measurements with SDO/AIA (Thurgood et al 2014;Weberg et al 2018;Morton et al 2019). Both decaying (Nakariakov et al 1999;Aschwanden et al 2002) and decayless Anfinogentov et al 2013) transverse oscillations have been observed in the solar atmosphere through direct imaging.…”

Section: Introductionmentioning

confidence: 99%

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Investigating “Dark” Energy in the Solar Corona Using Forward Modeling of MHD Waves

Pant¹,

Magyar²,

Doorsselaere³

et al. 2019

ApJ

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It is now well established that the Alfvénic waves are ubiquitous in the solar corona. However, the Alfvénic wave energy estimated from the Doppler velocity measurements in the corona was found to be four orders of magnitude less than that estimated from non-thermal line widths. McIntosh & De Pontieu (2012) suggested that this discrepancy in energy might be due to the line-of-sight (LOS) superposition of the several oscillating structures, which can lead to an underestimation of the Alfvénic wave amplitudes and energies. McIntosh & De Pontieu (2012) termed this coronal 'dark' or 'hidden' energy. However, their simulations required the use of an additional, unknown source of Alfvénic wave energy to provide agreement with measurements of the coronal non-thermal line widths. In this study, we investigate the requirement of this unknown source of additional 'dark' energy in the solar corona using gravitationally stratified 3D magnetohydrodynamic (MHD) simulations of propagating waves. We excite the transverse MHD waves and generate synthetic observations for the Fe XIII emission line. We establish that the LOS superposition greatly reduces the Doppler velocity amplitudes and increases the non-thermal line widths. Importantly, our model generates the observed wedge-shaped correlation between Doppler velocities and non-thermal line widths. We find that the observed wave energy is only 0.2-1% of the true wave energy which explains 2-3 orders of magnitude of the energy discrepancy. We conclusively establish that the true wave energies are hidden in the non-thermal line widths. Hence, our results rule out the requirement for an additional 'dark' energy in the solar corona.

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A basal contribution from p-modes to the Alfvénic wave flux in the Sun’s corona

Cited by 85 publications

References 38 publications

Damping of Propagating Kink Waves in the Solar Corona

Damping of Propagating Kink Waves in the Solar Corona

Mapping the magnetic field in the solar corona through magnetoseismology

Investigating “Dark” Energy in the Solar Corona Using Forward Modeling of MHD Waves

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