Origin of Deep Acoustic Sources Associated with Solar Magnetic Structures

Abstract

It is generally accepted that solar acoustic (p) modes are excited by near-surface turbulent motions, in particular, by downdrafts and interacting vortices in intergranular lanes. Recent analysis of Solar Dynamics Observatory data by (Zhao et al., 2015) revealed fast-moving waves around sunspots, which are consistent with magnetoacoustic waves excited approximately 5 Mm beneath the sunspot. We analyzed 3D radiative MHD simulations of solar magnetoconvection with a self-organized pore-like magnetic structure, and identified more than 600 individual acoustic events both inside and outside of this structure. By performing a case-by-case study, we found that surrounding the magnetic structure, acoustic sources are associated with downdrafts. Their depth correlates with downdraft speed and magnetic fields. The sources often can be transported into deeper layers by downdrafts. The wave front shape, in the case of a strong or inclined downdraft, can be stretched along the downdraft. Inside the magnetic structure, excitation of acoustic waves is driven by converging flows. Frequently, strong converging plasma streams hit the structure boundaries, causing compressions in its interior that excite acoustic waves. Analysis of the depth distribution of acoustic events shows the strongest concentration at 0.2 - 1 Mm beneath the surface for the outside sources and 2.5 - 3 Mm for the excitation event inside the structure.

arXiv comment23 pages, 12 figures

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• SUNRISE/IMaX observations of convectively driven vortex flows in the Sun
• Mechanism of spontaneous formation of stable magnetic structures on the Sun
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• Excitation of acoustic waves by vortices in the quiet Sun
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• Line asymmetry of solar p-modes: Properties of acoustic sources
• Vortex Tubes of Turbulent Solar Convection
• Simulations of Oscillation Modes of the Solar Convection Zone
• Detection of Fast-Moving Waves Propagating Outward along Sunspots' Radial Direction in the Photosphere
• Simulations of Stellar Magnetoconvection using the Radiative MHD Code `StellarBox'
• Dependence of sunspot photospheric waves on the depth of the source of solar $p-$modes

Cited by in corpus (6)

• The Physical Nature of Spiral Wave Patterns in Sunspots
• Source Depth of Three-minute Umbral Oscillations
• Identifying Acoustic Wave Sources on the Sun. II. Improved Filter Techniques for Source Wavefield Seismology
• Observations of Locally Excited Waves in the Low Solar Atmosphere Using the Daniel K. Inouye Solar Telescope (DKIST)
• Connecting Atmospheric Properties and Synthetic Emission of Shock Waves Using 3D RMHD Simulations of Quiet Sun
• Assessment of DKIST/VTF Capabilities for the Detection of Local Acoustic Source Wavefronts