Origin of the Chromospheric Umbral Waves in Sunspots

Abstract

Oscillations are ubiquitous in sunspots and the associated higher atmospheres. However, it is still unclear whether these oscillations are driven by the external acoustic waves (p-modes) or generated by the internal magnetoconvection. To obtain clues about the driving source of umbral waves in sunspots, we analyzed the spiral wave patterns (SWPs) in two sunspots registered by IRIS MgII 2796 Å slit-jaw images. By tracking the motion of the SWPs, we find for the first time that two one-armed SWPs coexist in the umbra, and they can rotate either in the same or opposite directions. Furthermore, by analyzing the spatial distribution of the oscillation centers of the one-armed SWPs within the umbra (the oscillation center is defined as the location where the SWP first appears), we find that the chromospheric umbral waves repeatedly originate from the regions with high oscillation power and most of the umbral waves occur in the dark nuclei and strong magnetic field regions of the umbra. Our study results indicate that the chromospheric umbral waves are likely excited by the p-mode oscillations.

References in corpus (31)

• The Interface Region Imaging Spectrograph (IRIS)
• Relationship between wave processes in sunspots and quasi-periodic pulsations in active region flares
• High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph
• Physical Properties of a Sunspot Chromosphere with Umbral Flashes
• The Source of Three-minute Magneto-acoustic Oscillations in Coronal Fans
• Multi-height observations of magnetoacoustic cut-off frequency in a sunspot atmosphere
• An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers
• On the Source of Propagating Slow Magneto-acoustic Waves in Sunspots
• Wave dynamics in a sunspot umbra
• Height variation of the cutoff frequency in a sunspot umbra
• The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere
• Magnetohydrodynamic waves driven by p-modes
• Dynamics in Sunspot Umbra as Seen in New Solar Telescope and Interface Region Imaging Spectrograph Data
• Height distribution of the power of 3-min oscillations over sunspots
• The Physical Nature of Spiral Wave Patterns in Sunspots
• Detection of Fast-Moving Waves Propagating Outward along Sunspots' Radial Direction in the Photosphere
• Stable Umbral Chromospheric Structures
• Magnetohydrodynamic wave mode identification in circular and elliptical sunspot umbrae: evidence for high order modes
• Proper Orthogonal and Dynamic Mode Decomposition of Sunspot Data
• Spiral-shaped wavefronts in a sunspot umbra
• Observations of Running Penumbral Waves emerging in a Sunspot
• Properties of local oscillations in the lower sunspot atmosphere
• Source Depth of Three-minute Umbral Oscillations
• The Observational Evidence for the Internal Excitation of Sunspot Oscillations Inferred from the Fe I 5435 A Line
• Spatial Distribution of Origin of Umbral Waves in a Sunspot Umbra
• Dependence of sunspot photospheric waves on the depth of the source of solar $p-$modes
• Doppler shift oscillations of a sunspot detected by CYRA and IRIS
• Analysis of Helioseismic Power-Spectrum Diagram of A Sunspot
• The dynamics of 3-minute wavefronts and their relation to sunspot magnetic fields
• Magneto-Acoustic Waves in Magnetic Twisted Flux Tube
• The Decay of Two Adjacent Sunspots Associated with Moving Magnetic Features