Internal Gravity Waves in the Magnetized Solar Atmosphere. II. Energy Transport

Abstract

In this second paper of the series on internal gravity waves (IGWs), we present a study of the generation and propagation of IGWs in a model solar atmosphere with diverse magnetic conditions. A magnetic field free, and three magnetic models that start with an initial, vertical, homogeneous field of 10 G, 50 G, and 100 G magnetic flux density, are simulated using the CO 5 BOLD code. We find that the IGWs are generated in similar manner in all four models in spite of the differences in the magnetic environment. The mechanical energy carried by IGWs is significantly larger than that of the acoustic waves in the lower part of the atmosphere, making them an important component of the total wave energy budget. The mechanical energy flux (10 6 -10 3 W m −2 ) is few orders of magnitude larger than the Poynting flux (10 3 -10 1 W m −2 ). The Poynting fluxes show a downward component in the frequency range corresponding to the IGWs, which confirm that these waves do not propagate upwards in the atmosphere when the fields are predominantly vertical and strong. We conclude that, in the upper photosphere, the propagation properties of IGWs depend on the average magnetic field strength and therefore these waves can be potential candidate for magnetic field diagnostics of these layers. However, their subsequent coupling to Alfvénic waves are unlikely in a magnetic environment permeated with predominantly vertical fields and therefore they may not directly or indirectly contribute to the heating of layers above plasma-β less than 1.

On the influence of magnetic topology on the propagation of internal gravity waves in the solar atmosphere

“…Our aim is to better understand the link between the brightness fluctuations in the internetwork region and IGWs, and the role of the magnetic field topology on their propagation characteristics. This paper extends on the previous studies [5][6][7] by comparing the propagation of IGWs in models with different magnetic field orientations. These environments are far from idealistic and have magnetic field properties that are more representative of the network/internetwork-like regions of the solar surface.…”

“…Finally, to represent the magnetic field behaviour in an internetwork-like region, we build a third model with an initial, horizontal, homogeneous field of 100 G flux density (Sun-h100). The former two models were part of an earlier study [6,7]. In this work, we present the new model that is constructed by introducing a horizontal magnetic field aligned in the x coordinate direction.…”

“…Low-frequency ultraviolet (UV) brightness fluctuations observed in the internetwork region of the low solar chromosphere are believed to be caused by IGWs dissipating in the higher layers [2]. However, the strong effects of magnetic field orientation (attack angle) on the propagation of IGW have been demonstrated by Newington & Cally [3,4] and realistic numerical simulations have shown that the magnetic field present in the solar atmosphere influence the propagation of these waves and likely hinder them from propagating into the upper atmosphere [5][6][7]. At this point, it is still unclear what role the magnetic field plays in the propagation of IGWs into higher layers and how this fits with the brightness fluctuations seen in chromosphere.…”

Review on “Photospheric vortex flows close to the polarity inversion line of a fully emerged active region”

“…I think it is more precise "However, strong flares (M-or X-class) are sometimes associated to rapid (abnormal) sunspot rotation", since the focus is on rotation but the main mechanism may be shear motions. Vorticity is very important, not only in the context for flares, but in different solar scenarios (e.g., the authors can check the relationship of vorticity and internal waves in Vigeesh et al, 2017).…”

A new method for detecting solar atmospheric gravity waves

“…IGWs have also been proposed as an agent for the mechanical heating of stellar atmospheres and coronae [10]. More recent studies [11][12][13] show the diagnostic potential of the IGWs for magnetic field in the solar atmosphere at different heights above the solar surface.…”