Umbral Dynamics in the Near Infrared Continuum

TL;DR

This study investigates umbral oscillations in a sunspot using near-infrared data, revealing localized oscillatory behavior, persistent umbral dots, and distinct oscillation periods with specific propagation characteristics.

Contribution

It provides new insights into the spatial and temporal properties of umbral oscillations and the behavior of umbral dots in the near-infrared continuum.

Findings

Detected oscillations at 3 and ~6.5 minutes in the umbra.

Umbral dots persist for over 30 minutes and are stationary.

Most powerful oscillations near 6.5 minutes do not propagate upward.

Abstract

We detected peaks of oscillatory power at 3 and ~6.5 minutes in the umbra of the central sunspot of the active region NOAA AR 10707 in data obtained in the near infrared (NIR) continuum at 1565.7 nm. The NIR dataset captured umbral dynamics around 50 km below the photospheric level. The umbra does not oscillate as a whole, but rather in distinct parts that are distributed over the umbral surface. The most powerful oscillations, close to a period of ~ 6.5, do not propagate upward. We noted a plethora of large umbral dots that persisted for more than 30 minutes and stayed in the same locations. The peaks of oscillatory power above the detected umbral dots are located at 3 and 5 minutes oscillations, but are very weak in comparison with the oscillations of ~ 6.5 minutes.