High Resolution Observations of Chromospheric Jets in Sunspot Umbra

Abstract

Recent observations of sunspot's umbra suggested that it may be finely structured at a sub-arcsecond scale representing a mix of hot and cool plasma elements. In this study we report the first detailed observations of the umbral spikes, which are cool jet-like structures seen in the chromosphere of an umbra. The spikes are cone-shaped features with a typical height of 0.5-1.0 Mm and a width of about 0.1 Mm. Their life time ranges from 2 to 3 min and they tend to re-appear at the same location. The spikes are not associated with photospheric umbral dots and they rather tend to occur above darkest parts of the umbra, where magnetic fields are strongest. The spikes exhibit up and down oscillatory motions and their spectral evolution suggests that they might be driven by upward propagating shocks generated by photospheric oscillations. It is worth noting that triggering of the running penumbral waves seems to occur during the interval when the spikes reach their maximum height.

References in corpus (3)

• Dynamic Fibrils are driven by Magnetoacoustic Shocks
• Magneto-convection in a sunspot umbra
• Spectroscopic measurements of dynamic fibrils in the Ca {\small{II}} 8662 Å line

Cited by in corpus (15)

• Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results
• The European Solar Telescope
• Inference of the chromospheric magnetic field orientation in the Ca II 8542 A line fibrils
• A Hot Downflowing Model Atmosphere For Umbral Flashes And The Physical Properties Of Their Dark Fibrils
• Dynamics in Sunspot Umbra as Seen in New Solar Telescope and Interface Region Imaging Spectrograph Data
• Chromospheric Plasma Ejections in a Light Bridge of a Sunspot
• The formation of small-scale umbral brightenings in sunspot atmospheres
• The Propagation of Coherent Waves Across Multiple Solar Magnetic Pores
• On Modeling the Kelvin--Helmholtz Instability in Solar Atmosphere
• Stable Umbral Chromospheric Structures
• Alfvénic motions arising from asymmetric acoustic wave drivers in solar magnetic structures
• Spatial Distribution of Origin of Umbral Waves in a Sunspot Umbra
• Downflowing umbral flashes as an evidence of standing waves in sunspot umbrae
• First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash
• Behaviour of oscillations in loop structures above active regions