IRIS observations of chromospheric heating by acoustic waves in solar quiet and active regions

Abbasvand, Vahid; Sobotka, M.; Švanda, Michal; Heinzel, P.; Liu, W.; Mravcová, Lucia

doi:10.1051/0004-6361/202140344

Cited by 12 publications

(9 citation statements)

References 39 publications

(48 reference statements)

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“…Therefore, the energy flux available at a height of 800 km (i.e., ∼10 4 W m −2 ) is just sufficient to balance the estimated radiative losses in the layers above this height, as estimated by Withbroe & Noyes (1977). This is in contrast to previous studies where acoustic flux was found to be insufficient to compensate for the radiative losses (Fossum & Carlsson 2005b;Beck et al 2009;Abbasvand et al 2020Abbasvand et al , 2021. Additionally, the acoustic wave flux in the height range of 250-600 km is much larger than estimated in previous studies pertaining to quiet Sun regions (Wunnenberg et al 2002;Straus et al 2008;Bello González et al 2009).…”

Section: Resultsmentioning

confidence: 72%

Slow magneto-acoustic waves in simulations of a solar plage region carry enough energy to heat the chromosphere

Yadav

Cameron

Solanki

2021

A&A

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Aims. We study the properties of slow magneto-acoustic waves that are naturally excited as a result of turbulent convection and we investigate their role in the energy balance of a plage region using three dimensional radiation magnetohydrodynamic simulations. Methods. To follow slow magneto-acoustic waves traveling along the magnetic field lines, we selected 25 seed locations inside a strong magnetic element and tracked the associated magnetic field lines both in space and time. We calculate the longitudinal component (i.e., parallel to the field) of velocity at each grid point along the field line and compute the temporal power spectra at various heights above the mean solar surface. Additionally, the horizontally-averaged (over the whole domain) frequency power spectra for both longitudinal and vertical (i.e., the component perpendicular to the surface) components of velocity are calculated using time series at fixed locations. To compare our results with the observations, we degrade the simulation data with Gaussian kernels having a full width at half maxium of 100 km and 200 km and calculate the horizontally-averaged power spectra for the vertical component of velocity using time series at fixed locations. Results. The power spectra of the longitudinal component of velocity, averaged over 25 field lines in the core of a kG magnetic flux concentration reveal that the dominant period of oscillations shifts from ∼6.5 min in the photosphere to ∼4 min in the chromosphere. This behavior is consistent with earlier studies that were restricted to vertically propagating waves. At the same time, the velocity power spectra, averaged horizontally over the whole domain, show that low frequency waves (∼6.5 min period) may reach well into the chromosphere. In addition, the power spectra at high frequencies follow a power law with an exponent close to −5/3, suggestive of turbulent excitation. Moreover, waves with frequencies above 5 mHz propagating along different field lines are found to be out of phase with each other, even within a single magnetic concentration. The horizontally-averaged power spectra of the vertical component of velocity at various effective resolutions show that the observed acoustic wave energy fluxes are underestimated by a factor of three, even if determined from observations carried out at a high spatial resolution of 200 km. Since the waves propagate along the non-vertical field lines, measuring the velocity component along the line-of-sight, rather than along the field, contributes significantly to this underestimation. Moreover, this underestimation of the energy flux indirectly indicates the importance of high-frequency waves that are shown to have a smaller spatial coherence and are thus more strongly influenced by the spatial averaging effect compared to low-frequency waves. Conclusions. Inside a plage region, there is on average a significant fraction of low frequency waves leaking into the chromosphere due to inclined magnetic field lines. Our results show that longitudinal waves carry (just) enough energy to heat the chromosphere in the solar plage. However, phase differences between waves traveling along different field lines within a single magnetic concentration can lead to underestimations of the wave energy flux due to averaging effects in degraded simulation data and, similarly, in observations with lower spatial resolution. We find that current observations (with spatial resolution around 200 km) underestimate the energy flux by roughly a factor of three – or more if the observations are carried out at a lower spatial resolution. We expect that even at a very high resolution, which is expected with the next generation of telescopes such as DKIST and the EST, less than half, on average, of the energy flux carried by such waves will be detected if only the line-of-sight component of the velocity is measured.

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Section: Resultsmentioning

confidence: 72%

Slow magneto-acoustic waves in simulations of a solar plage region carry enough energy to heat the chromosphere

Yadav

Cameron

Solanki

2021

A&A

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“…The temperature in the quiet chromosphere oscillates between an atmosphere in radiative equilibrium and one with a moderate chromospheric temperature rise, and horizontal canopy structure reflects itself in temperature maps at heights in the low chromosphere (Beck et al 2013). Using Ca II 853.2 IBIS data, Abbasvand et al(2020a) found that the deposited magnetoacoustic wave energy balances 30-50% radiative losses in the quiet chromosphere and 50-60% of the losses in a plage with vertical field, rising up to 70-90% in the plage regions with inclined field. This way, significant portions of the radiative losses could be compensated via acoustic wave flux which has been previously converted to magnetoacoustic wave flux in the regions with the inclined fields.…”

Section: Wave Heating Of the Large-scale Chromospherementioning

confidence: 99%

Chromospheric Heating by Magnetohydrodynamic Waves and Instabilities

et al. 2021

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The importance of the chromosphere in the mass and energy transport within the solar atmosphere is now widely recognised. This review discusses the physics of magnetohydrodynamic (MHD) waves and instabilities in large-scale chromospheric structures as well as in magnetic flux tubes. We highlight a number of key observational aspects that have helped our understanding of the role of the solar chromosphere in various dynamic processes and wave phenomena, and the heating scenario of the solar chromosphere is also discussed. The review focuses on the physics of waves and invokes the basics of plasma instabilities in the context of this important layer of the solar atmosphere. Potential implications, future trends and outstanding questions are also delineated.

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“…Magnetic reconnection and heating due to waves are not independent mechanisms, however, since magnetic reconnection can be a source of waves (Verwichte et al 2004;Jess et al 2008;Luna et al 2008;Li & Zhang 2012;Provornikova et al 2018), and waves can produce instabilities needed to trigger reconnection processes (Isobe & Tripathi 2006;Lee et al 2014;McLaughlin et al 2009). Moreover, recent advances in observational instrumentation and simulation capabilities imply that wave-based heating could be a viable process for maintaining the high temperatures of the solar atmosphere (Abbasvand et al 2020(Abbasvand et al , 2021Yadav et al 2021b). These new results have drawn renewed interest in wave-heating mechanisms, both observationally and theoretically.…”

Section: Introductionmentioning

confidence: 99%

3D MHD wave propagation near a coronal null point: New wave mode decomposition approach

Yadav

Keppens

Braileanu

2022

A&A

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Context. Ubiquitous vortex flows at the solar surface excite magnetohydrodynamic (MHD) waves that propagate to higher layers of the solar atmosphere. In the solar corona, these waves frequently encounter magnetic null points. The interaction of MHD waves with a coronal magnetic null in realistic 3D setups requires an appropriate wave identification method. Aims. We present a new MHD wave decomposition method that overcomes the limitations of existing wave identification methods. Our method allows for an investigation of the energy fluxes in different MHD modes at different locations of the solar atmosphere as waves generated by vortex flows travel through the solar atmosphere and pass near the magnetic null. Methods. We used the open-source MPI-AMRVAC code to simulate wave dynamics through a coronal null configuration. We applied a rotational wave driver at our bottom photospheric boundary to mimic vortex flows at the solar surface. To identify the wave energy fluxes associated with different MHD wave modes, we employed a wave decomposition method that is able to uniquely distinguish different MHD modes. Our proposed method utilizes the geometry of an individual magnetic field-line in the 3D space to separate the velocity perturbations associated with the three fundamental MHD waves. We compared our method with an existing wave decomposition method that uses magnetic flux surfaces instead. Over the selected flux surfaces, we calculated and analyzed the temporally averaged wave energy fluxes, as well as the acoustic and magnetic energy fluxes. Our wave decomposition method allowed us to estimate the relative strengths of individual MHD wave energy fluxes. Results. Our method for wave identification is consistent with previous flux-surface-based methods and provides the expected results in terms of the wave energy fluxes at various locations of the null configuration. We show that ubiquitous vortex flows excite MHD waves that contribute significantly to the Poynting flux in the solar corona. Alfvén wave energy flux accumulates on the fan surface and fast wave energy flux accumulates near the null point. There is a strong current density buildup at the spine and fan surface. Conclusions. The proposed method has advantages over previously utilized wave decomposition methods, since it may be employed in realistic simulations or magnetic extrapolations, as well as in real solar observations whenever the 3D fieldline shape is known. The essential characteristics of MHD wave propagation near a null – such as wave energy flux accumulation and current buildup at specific locations – translate to the more realistic setup presented here. The enhancement in energy flux associated with magneto-acoustic waves near nulls may have important implications in the formation of jets and impulsive plasma flows.

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IRIS observations of chromospheric heating by acoustic waves in solar quiet and active regions

Cited by 12 publications

References 39 publications

Slow magneto-acoustic waves in simulations of a solar plage region carry enough energy to heat the chromosphere

Slow magneto-acoustic waves in simulations of a solar plage region carry enough energy to heat the chromosphere

Chromospheric Heating by Magnetohydrodynamic Waves and Instabilities

3D MHD wave propagation near a coronal null point: New wave mode decomposition approach

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