Wave heating of the solar atmosphere

Abstract

One contribution of 13 to a Theo Murphy meeting issue 'New approaches in coronal heating' . Magnetic waves are a relevant component in the dynamics of the solar atmosphere. Their significance has increased because of their potential as a remote diagnostic tool and their presumed contribution to plasma heating processes. We discuss our current understanding of coronal heating by magnetic waves, based on recent observational evidence and theoretical advances. The discussion starts with a selection of observational discoveries that have brought magnetic waves to the forefront of the coronal heating discussion. Then, our theoretical understanding of the nature and properties of the observed waves and the physical processes that have been proposed to explain observations are described. Particular attention is given to the sequence of processes that link observed wave characteristics with concealed energy transport, dissipation and heat conversion. We conclude with a commentary on how the combination of theory and observations should help us to understand and quantify magnetic wave heating of the solar atmosphere.

Recent advances in coronal heating

“…However, as recent observations have revealed that significant wave power is present in (closed) coronal loops, wave heating mechanisms are regaining the attention of the solar physics community [14]. An important point to note here is that (observed) wave damping does not automatically imply dissipation, and hence heating, as the two processes could potentially operate on very different spatial and temporal scales.…”

“…In recent years, there has been a wealth of observations of various waves and oscillations in the corona [14]. As well as potentially being directly involved in heating, the detection of waves and oscillations has opened up the field of coronal seismology, potentially allowing parameters such as magnetic field strengths to be inferred (see [15] for a recent review).…”

“…An important point to note here is that (observed) wave damping does not automatically imply dissipation, and hence heating, as the two processes could potentially operate on very different spatial and temporal scales. Theoretical models face the challenge to confirm that the observed waves and oscillations do indeed contribute to coronal heating on relevant time scales [4,14].…”

“…Careful analysis of observational data provides evidence of such structure [8], whose existence has implications for heating both through waves [14] and reconnection [20] and with obvious relevance for flux braiding experiments, instabilities and nanoflare modelling, among others.…”

Impulsively Generated Wave Trains in Coronal Structures. I. Effects of Transverse Structuring on Sausage Waves in Pressureless Tubes

“…Apart from being important agents for atmospheric heating (see e.g., Klimchuk 2006;Parnell & De Moortel 2012;Arregui 2015;De Moortel & Browning 2015, for some recent reviews), these waves and oscillations can also be exploited in the context of solar magneto-seismology (SMS) to infer the atmospheric parameters that are difficult to directly measure (for early ideas that laid the foundation of this practice, see Uchida 1970, Rosenberg 1970, Zajtsev & Stepanov 1975, Roberts et al 1984; also see recent reviews by e.g., Nakariakov & Verwichte 2005, Roberts 2008, Erdélyi & Goossens 2011, Nakariakov et al 2016. For instance, "high-frequency" fast waves with periods of order seconds were theoretically shown to play an important role in heating the solar corona (e.g., Porter et al 1994b,a).…”