Various Local Heating Events in the Earliest Phase of Flux Emergence

Abstract

Emerging flux regions (EFRs) are known to exhibit various sporadic local heating events in the lower atmosphere. To investigate the characteristics of these events, especially to link the photospheric magnetic fields and atmospheric dynamics, we analyze Hinode, IRIS, and SDO data of a new EFR in NOAA AR 12401. Out of 151 bright points (BPs) identified in Hinode/SOT Ca images, 29 are overlapped by an SOT/SP scan. Seven BPs in the EFR center possess mixed-polarity magnetic backgrounds in the photosphere. Their IRIS UV spectra (e.g., Si IV 1402.8 A) are strongly enhanced and red- or blue-shifted with tails reaching +/- 150 km/s, which is highly suggestive of bi-directional jets, and each brightening lasts for 10 - 15 minutes leaving flare-like light curves. Most of this group show bald patches, the U-shaped photospheric magnetic loops. Another 10 BPs are found in unipolar regions at the EFR edges. They are generally weaker in UV intensities and exhibit systematic redshifts with Doppler speeds up to 40 km/s, which could exceed the local sound speed in the transition region. Both types of BPs show signs of strong temperature increase in the low chromosphere. These observational results support the physical picture that heating events in the EFR center are due to magnetic reconnection within cancelling undular fields like Ellerman bombs, while the peripheral heating events are due to shocks or strong compressions caused by fast downflows along the overlying arch filament system.

17 pages, 10 figures, accepted for publication in ApJ. Corresponding movie for Figure 1 can be found at http://www-space.eps.s.u-tokyo.ac.jp/~toriumi/toriumi2017b.mov

References in corpus (6)

• The Solar Optical Telescope for the Hinode Mission: An Overview
• Hot Explosions in the Cool Atmosphere of the Sun
• Solar surface emerging flux regions: a comparative study of radiative MHD modeling and Hinode SOT observations
• Observations of Subarcsecond Bright Dots in the Transition Region above Sunspots with the Interface Region Imaging Spectrograph
• Detection of supersonic downflows and associated heating events in the transition region above sunspots
• Statistical Analysis of the Horizontal Divergent Flow in Emerging Solar Active Regions

Cited by in corpus (23)

• Flare-productive active regions
• Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)
• Ellerman bombs and UV bursts: reconnection at different atmospheric layers
• Flame-like Ellerman Bombs and Their Connection to Solar UV Bursts
• A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating II. 2D Theory and Simulations
• An observationally-constrained model of strong magnetic reconnection in the solar chromosphere. Atmospheric stratification and estimates of heating rates
• IRIS observations of magnetic interactions in the solar atmosphere between pre-existing and emerging magnetic fields. II. UV emission properties
• Automating Ellerman bomb detection in ultraviolet continua
• The formation of small-scale umbral brightenings in sunspot atmospheres
• Three-dimensional magnetic field structure of a flux emerging region in the solar atmosphere
• Emergence of small-scale magnetic flux in the quiet Sun
• Multi-Scale Deep Learning for Estimating Horizontal Velocity Fields on the Solar Surface
• High-resolution Observations of Small-scale Flux Emergence by GST
• Sunspot penumbral filaments intruding into a light bridge and the resultant reconnection jets
• Transition region loops in the very late phase of flux-emergence in IRIS sit-and-stare observations
• Signatures of the impact of flare ejected plasma on the photosphere of a sunspot light-bridge
• Magnetic Topology of quiet-Sun Ellerman bombs and associated Ultraviolet brightenings
• Small-scale dynamic phenomena associated with interacting fan-spine topologies: quiet-Sun Ellerman bombs, UV brightenings, and chromospheric inverted-Y-shaped jets
• Various Activities above Sunspot Light Bridges in IRIS Observations: Classification and Comparison
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Data-driven Radiative Magnetohydrodynamics Simulations with the MURaM Code: Coronal Heating and Dynamics in an Emerging Active Region
• SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation
• Observations of the formation of a proto-spot in a pre-existing field environment