Dynamics in the transition region beneath active region upflows viewed by IRIS

Abstract

Coronal upflows at the edges of active regions (AR), which are a possible source of slow solar wind, have been found to connect with dynamics in the transition region. To infer at what scale transition region dynamics connect to AR upflows, we investigate the statistical properties of the small-scale dynamics in the transition region underneath the upflows at the edge of AR NOAA 11934. With observations from the Interface Region Imaging Spectragraph (IRIS), we found that the Si IV 1403\,Å Doppler map consists of numerous blue-shifted and red-shifted patches mostly with sizes less than 1\,$M{m}^2$. The blue-shifted structures in the transition region tend to be brighter than the red-shifted ones, but their nonthermal velocities have no significant difference. With the SWAMIS feature tracking procedure, in IRIS slit-jaw 1400\,Å images we found that dynamic bright dots with an average size of about 0.3\,$M{m}^2$ and lifetimes mostly less than 200\,s spread all over the region. Most of the bright dots appear to be localised, without clear signature of propagation of plasma to a long distance on the projection plane. Surge-like motions with speeds about 15 km/s could be seen in some events at the boundaries of the upflow region, where the magnetic field appear to be inclined. We conclude that the transition region dynamics connecting to coronal upflows should occur in very fine scale, suggesting that the corresponding coronal upflows should also be highly-structured. It is also plausible that the transition region dynamics might just act as stimulation at the coronal base that then drives the upflows in the corona.

arXiv comment16 pages, 7 figures, accepted for publication in ApJ

References in corpus (50)

• The Interface Region Imaging Spectrograph (IRIS)
• The Solar Optical Telescope for the Hinode Mission: An Overview
• The Solar Orbiter mission -- Science overview
• The formation of IRIS diagnostics II. The formation of the Mg II h&k lines in the solar atmosphere
• Persistent Doppler shift oscillations observed with HINODE/EIS in the solar corona: spectroscopic signatures of Alfvenic waves and recurring upflows
• The Magnetic Field in the Solar Atmosphere
• Full-Sun observations for identifying the source of the slow solar wind
• Establishing a Connection Between Active Region Outflows and the Solar Wind: Abundance Measurements with EIS/Hinode
• Flows and Non-thermal Velocities in Solar Active Regions Observed with the Extreme-ultraviolet Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?
• The formation of IRIS diagnostics. III. Near-ultraviolet Spectra and Images
• Quasi-periodic Propagating Signals in the Solar Corona: The Signature of Magnetoacoustic Waves or High-Velocity Upflows?
• Magnetic Reconnection along Quasi-Separatrix Layers as a Driver of Ubiquitous Active Region Outflows
• Solar Magnetic Tracking. I. Software Comparison and Recommended Practices
• The Spectroscopic Signature of Quasi-periodic Upflows in Active Region Timeseries
• Iris si iv line profiles: An indication for the plasmoid instability during small-scale magnetic reconnection on the sun
• Coronal hole boundaries at small scales: IV. SOT view Magnetic field properties of small-scale transient brightenings in coronal holes
• The Temperature Dependence of Solar Active Region Outflows
• Velocity measurements for a solar active region fan loop from Hinode/EIS observations
• Upflows in the upper solar atmosphere
• Tracking Solar Active Region Outflow Plasma from its Source to the near-Earth Environment
• Oscillating light wall above a sunspot light bridge
• The coronal source of extreme-ultraviolet line profile asymmetries in solar active region outflows
• IRIS observations of short-term variability in moss associated with transient hot coronal loops
• Temporal Variability of Active Region Outflows
• Surge-like oscillations above sunspot light bridges driven by magnetoacoustic shocks
• Cool transition region loops observed by the Interface Region Imaging Spectrograph
• Coronal sources and in situ properties of the solar winds sampled by ACE during 1999-2008
• Sources of quasi-periodic propagating disturbances above a solar polar coronal hole
• Solar Magnetic Tracking. IV. The Death of Magnetic Features
• Charge States and FIP Bias of the Solar Wind from Coronal Holes, Active Regions, and Quiet Sun
• Flows at the Edge of an Active Region: Observation and Interpretation
• Signatures of the slow solar wind streams from active regions in the inner corona
• How Can Active Region Plasma Escape into the Solar Wind from below a Closed Helmet Streamer?
• The 3D geometry of active region upflows deduced from their limb-to-limb evolution
• The drivers of active region outflows into the slow solar wind
• Light Walls Around Sunspots Observed by the Interface Region Imaging Spectrograph
• Spectroscopic analysis of interaction between an EIT wave and a coronal upflow region
• Active region upflows: 2. Data driven MHD modeling
• IRIS observations of the low-atmosphere counterparts of active region outflows
• Apparent and Intrinsic Evolution of Active Region Upflows
• Spatial Nonlocality of the Small-Scale Solar Dynamo
• Quasi-period outflows observed by the X-Ray Telescope onboard Hinode in the boundary of an active region
• Kinetic Simulation of Slow Magnetosonic Waves and Quasi-periodic Upflows in the Solar Corona
• Observations of upward propagating waves in the transition region and corona above Sunspots
• A comparison of the active region upflow and core properties using simultaneous spectroscopic observations from IRIS and Hinode
• The Formation and Lifetime of Outflows in a Solar Active Region
• Multi-channel Observations of Plasma Outflows and the Associated Small-Scale Magnetic Field Cacellations on the Edges of an Active Region
• On Thermal-Pulse-Driven Plasma Flows in Coronal Funnels as Observed by Hinode/EUV Imaging Spectrometer (EIS)
• Electron density of active region outflows measured by the EUV Imaging Spectrometer onboard Hinode
• Transition region bright dots in active regions observed by the Interface Region Imaging Spectrograph

Cited by in corpus (1)

• Active region upflows in various coronal structures and their coupling to the lower atmosphere