Characteristics and Evolution of the Magnetic field and Chromospheric Emission in an Active Region Core Observed by Hinode

Abstract

We describe the characteristics and evolution of the magnetic field and chromospheric emission in an active region core observed by the Solar Optical Telescope on Hinode. Consistent with previous studies, we find that the moss is unipolar, the spatial distribution of magnetic flux evolves slowly, and the magnetic field is only moderately inclined. We show that the field line inclination and horizontal component are coherent, and that the magnetic field is mostly sheared in the inter-moss regions where the highest magnetic flux variability is seen. Using extrapolations from SP magnetograms we show that the magnetic connectivity in the moss is different than in the quiet Sun because most of the magnetic field extends to significant coronal heights. The magnetic flux, field vector, and chromospheric emission in the moss also appear highly dynamic, but actually show only small scale variations in magnitude on time-scales longer than the cooling times for hydrodynamic loops computed from our extrapolations, suggesting high-frequency (continuous) heating events. Some evidence is found for flux (Ca 2 intensity) changes on the order of 100--200 G (DN) on time-scales of 20--30 mins that could be taken as indicative of low-frequency heating. We find, however, that only a small fraction (10%) of our simulated loops would be expected to cool on these time-scales, and we find no clear evidence that the flux changes consistently produce intensity changes in the chromosphere. The magnetic flux and chromospheric intensity in most individual SOT pixels in the moss vary by less than ~ 20% and ~ 10%, respectively, on loop cooling time-scales. In view of the high energy requirements of the chromosphere, we suggest that these variations could be sufficient for the heating of `warm' EUV loops, but that the high basal levels may be more important for powering the hot core loops rooted in the moss.

Accepted by ApJ, 16 pages, 20 figures. Abridged abstract (original is in PDF file). Figures 1 & 2 are reduced resolution to meet size limits

References in corpus (9)

• The Solar Optical Telescope for the Hinode Mission: An Overview
• A Critical Assessment of Nonlinear Force-Free Field Modeling of the Solar Corona for Active Region 10953
• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
• Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode
• Evidence for Steady Heating: Observations of an Active Region Core with Hinode and TRACE
• Flows and Motions in Moss in the Core of a Flaring Active Region: Evidence for Steady Heating
• Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode
• Density structure of an active region and associated moss using Hinode/EIS
• Static and Impulsive Models of Solar Active Regions

Cited by in corpus (3)

• High-resolution observations of active region moss and its dynamics
• Energetics of magnetic transients in a solar active region plage
• Magnetic filed dynamics and varying plasma emission in large coronal loops