GST high-resolution observations of small-scale flux emergence in multiwavelengths
Abstract
The near-infrared imaging spectropolarimeter (NIRIS) of the 1.6 m Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO) produces vector magnetograms at 0.24" resolution and up to 30 s cadence. These unprecedented high spatiotemporal resolution data provide us a unique opportunity to study the small-scale magnetic flux emergence and cancellation events, which can advance our understanding of the structural evolution of photospheric fields and related dynamic activities spanning the solar atmosphere. In our previous study using NIRIS observations, we detected that during flux emergence there appears two components of magnetic fluxes, the central diffused magnetic structure with enhancing horizontal field and concentrated opposite-polarity fluxes at the two ends. In this work, we jointly analyze NIRIS and other BBSO/GST observations of NOAA AR 12665 on 2017 July 13, with the goal of shedding light on the signatures and responses of small-scale flux emergence in multiple heights. We focus on case studies of flux emergence events near the magnetic polarity inversion line. With direct imaging in broadband TiO (a proxy for continuum in photosphere at 705.7 nm) at 0.1" resolution and 15 s cadence, we observe that magnetic flux emergence is associated with darkening of granular boundaries and elongation of granules. When newly emerged magnetic elements cancel with the existing opposite-polarity fields, bright point features are seen and they travel along the intergranular dark lanes at a speed of about 4 km/s. The canceled flux is in the order of 4x1016 Mx. In Hα observations (0.1 resolution and 34 s cadence) at several line positions (±1.0, ±0.6, ±0.4, and line center), we see transient brightenings in the red and blue wings, which are most probably Ellerman bombs. In a particularly well observed event, we find brightenings in Hα red-wing(0.4 Å) around the central diffused emerging region, where horizontal flux density increases and peaks at 250 Mx/cm2; when it restores to its initial state, the horizontal flux density increases at the concentrated flux regions at the two ends. In the mean time, brightenings are also observed at concentrated flux footpoints in Hα far red-wing (0.6 Å, 1.0 Å). We suggest that these observations may reflect the reconnection process between the emerging flux and overlying field.
- Publication:
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American Astronomical Society Meeting Abstracts #234
- Pub Date:
- June 2019
- Bibcode:
- 2019AAS...23421701W