Oscillatory Response of the Solar Chromosphere to a Strong Downflow above a Sunspot

Abstract

We report three-minute oscillations in the solar chromosphere driven by a strong downflow event in a sunspot. We used the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope and the Interface Region Imaging Spectrograph (IRIS). The strong downflow event is identified in the chromospheric and transition region lines above the sunspot umbra. After the event, oscillations occur at the same region. The amplitude of the Doppler velocity oscillations is 2 km/s, and gradually decreases with time. In addition, the period of the oscillations gradually increases from 2.7 minutes to 3.3 minutes. In the IRIS 1330 slit-jaw images, we identify a transient brightening near the footpoint of the downflow detected in the Ha+0.5A image. The characteristics of the downflowing material are consistent with those of sunspot plumes. Based on our findings, we suggest that the gravitationally stratified atmosphere came to oscillate with three minute period in response to the impulsive downflow event as was theoretically investigated by Chae & Goode(2015).

arXiv comment13 pages, 4 figures, accepted for publication in ApJ Letters

References in corpus (5)

• The Interface Region Imaging Spectrograph (IRIS)
• Dynamic Hydrogen Ionization
• High-resolution Observations of the Shock Wave Behavior for Sunspot Oscillations with the Interface Region Imaging Spectrograph
• Properties of Flares-Generated Seismic Waves on the Sun
• Sunspot transition region oscillations in NOAA 8156

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• Narrow-line-width UV bursts in the transition region above Sunspots observed by IRIS
• Observations of upward propagating waves in the transition region and corona above Sunspots
• Downflowing umbral flashes as an evidence of standing waves in sunspot umbrae
• Spatial Distribution of Origin of Umbral Waves in a Sunspot Umbra
• Oscillations accompanying a He I 10830 Å negative flare in a solar facula
• Three-minute Sunspot Oscillations Driven by Magnetic Reconnection in a Light Bridge
• Spatial and temporal analysis of 3-minute oscillations in the chromosphere associated with the X2.2 Solar Flare on 2011 February 15
• The effect of a solar flare on chromospheric oscillations
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)