Investigating Alfvénic wave propagation in coronal open-field regions

Morton, R. J.; Tomczyk, S.; Pinto, Rui

doi:10.1038/ncomms8813

Cited by 148 publications

(230 citation statements)

References 72 publications

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“…It should instead be B ≈ 2.4 ± 0.6 G. Although this value is lower than the original (incorrect) value quoted in Long et al (2017), it does not affect the qualitative results or conclusions of the paper. The magnetic field strength estimated using the oscillation of the transequatorial loop system is still comparable to the values estimated using both the independent magnetoseismology approach of Morton et al (2015Morton et al ( , 2016 and the extrapolated magnetic field obtained from both the HMI and GONG magnetograms. This indicates that the approach is still sound, albeit with a lower estimated value.…”

supporting

confidence: 62%

Measuring the magnetic field of a trans-equatorial loop system using coronal seismology (Corrigendum)

Long¹,

Valori²,

Pérez–Suárez³

et al. 2017

A&A

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It has been brought to our attention (B. Roberts, 2017, priv. comm.) that the formula used in Eq. (2) of our paper (Long et al. 2017) was incorrect. This equation should instead have readwhere B is the magnetic field strength, L is the loop length, P is the period of the oscillation, ρ in is the internal density of the loop system and ρ ex is the external density of the surrounding corona (cf. Roberts et al. 1984;Nakariakov & Ofman 2001; Van Doorsselaere et al. 2008a;Aschwanden & Schrijver 2011). As a result of the incorrect equation used, the value of the magnetic field strength estimated using the oscillation of the transequatorial loop system quoted in Sect. 5.1 of Long et al. (2017) is also incorrect. It should instead be B ≈ 2.4 ± 0.6 G. Although this value is lower than the original (incorrect) value quoted in Long et al. (2017), it does not affect the qualitative results or conclusions of the paper. The magnetic field strength estimated using the oscillation of the transequatorial loop system is still comparable to the values estimated using both the independent magnetoseismology approach of Morton et al. (2015Morton et al. ( , 2016 and the extrapolated magnetic field obtained from both the HMI and GONG magnetograms. This indicates that the approach is still sound, albeit with a lower estimated value.

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supporting

confidence: 62%

Measuring the magnetic field of a trans-equatorial loop system using coronal seismology (Corrigendum)

Long¹,

Valori²,

Pérez–Suárez³

et al. 2017

A&A

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“…Alfvén waves are of particular interest because they can propagate over large distances in the corona before giving up their energy. Transverse waves have been observed in the corona above the solar limb (Tomczyk et al 2007;Tomczyk & McIntosh 2009;Threlfall et al 2013;Morton et al 2015), in the swaying motions of spicules (De Pontieu et al 2007), in network jets on the solar disk (Tian et al 2011(Tian et al , 2014, and in the solar wind (Coleman 1968;Belcher 1971;Matthaeus et al 1990;Bale et al 2005;Borovsky 2012). The observed amplitudes of Alfvén waves at the coronal base are sufficient to heat and accelerate the solar wind (De Pontieu et al 2007;McIntosh et al 2011), and Alfvén waves are believed to be the main driver of the fast wind (e.g., Suzuki & Inutsuka 2005;Cranmer et al 2007;Verdini & Velli 2007;Chandran et al 2011).…”

Section: Introductionmentioning

confidence: 99%

The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

Ballegooijen¹,

Asgari-Targhi

Voß

2017

ApJ

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In this paper we further develop a model for the heating of coronal loops by Alfvén wave turbulence (AWT). The Alfvén waves are assumed to be launched from a collection of kilogauss flux tubes in the photosphere at the two ends of the loop. Using a three-dimensional magneto-hydrodynamic (MHD) model for an active-region loop, we investigate how the waves from neighboring flux tubes interact in the chromosphere and corona. For a particular combination of model parameters we find that AWT can produce enough heat to maintain a peak temperature of about 2.5 MK, somewhat lower than the temperatures of 3 -4 MK observed in the cores of active regions. The heating rates vary strongly in space and time, but the simulated heating events have durations less than 1 minute and are unlikely to reproduce the observed broad Differential Emission Measure distributions of active regions. The simulated spectral line non-thermal widths are predicted to be about 27 km s −1 , which is high compared to the observed values. Therefore, the present AWT model does not satisfy the observational constraints. An alternative "magnetic braiding" model is considered in which the coronal field lines are subject to slow random footpoint motions, but we find that such long period motions produce much less heating than the shorter period waves launched within the flux tubes. We discuss several possibilities for resolving the problem of producing sufficiently hot loops in active regions.

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“…Magnetohydrodynamic waves, particularly Alfvén(ic) waves, have been a topic of intense study (e.g., Cranmer & van Ballegooijen 2005;Verdini & Velli 2007;Van der Holst et al 2014), as they can simultaneously address both coronal heating and solar wind acceleration. While Alfvénic waves have been detected in the solar wind from in situ measurements since the 1970s (Belcher & Davis 1971), it is only recently that propagating transverse waves have been observed in the corona (Tomczyk et al 2007;McIntosh et al 2011;Thurgood et al 2014;Morton et al 2015Morton et al , 2016b.…”

Section: Introductionmentioning

confidence: 99%

An Automated Algorithm for Identifying and Tracking Transverse Waves in Solar Images

Weberg

Morton

McLaughlin

2018

ApJ

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Recent instrumentation has demonstrated that the solar atmosphere supports omnipresent transverse waves, which could play a key role in energizing the solar corona. Large-scale studies are required in order to build up an understanding of the general properties of these transverse waves. To help facilitate this, we present an automated algorithm for identifying and tracking features in solar images and extracting the wave properties of any observed transverse oscillations. We test and calibrate our algorithm using a set of synthetic data, which includes noise and rotational effects. The results indicate an accuracy of 1%-2% for displacement amplitudes and 4%-10% for wave periods and velocity amplitudes. We also apply the algorithm to data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and find good agreement with previous studies. Of note, we find that 35%-41% of the observed plumes exhibit multiple wave signatures, which indicates either the superposition of waves or multiple independent wave packets observed at different times within a single structure. The automated methods described in this paper represent a significant improvement on the speed and quality of direct measurements of transverse waves within the solar atmosphere. This algorithm unlocks a wide range of statistical studies that were previously impractical.

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Investigating Alfvénic wave propagation in coronal open-field regions

Cited by 148 publications

References 72 publications

Measuring the magnetic field of a trans-equatorial loop system using coronal seismology (Corrigendum)

Measuring the magnetic field of a trans-equatorial loop system using coronal seismology (Corrigendum)

The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

An Automated Algorithm for Identifying and Tracking Transverse Waves in Solar Images

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