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Apparent and Intrinsic Evolution of Active Region Upflows
Deborah Baker1, Miho Janvier2, Pascal Démoulin3
11Mullard Space Science Laboratory, University College London, Holmbury, St. Mary, Dorking, Surrey, KT22 9XF UK.
Solar Physics
|February 28, 2020
Summary
Solar rotation influences observed coronal plasma upflows, with actual evolution depending on active region activity. Upflows often appear in pairs, suggesting non-local driving mechanisms like magnetic reconnection.
Area of Science:
- Solar Physics
- Plasma Physics
- Heliophysics
Background:
- Analysis of Fe xii coronal plasma upflows from active regions (ARs) crossing the solar disk.
- Utilizes data from the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS).
Purpose of the Study:
- To analyze the evolution of Fe xii coronal plasma upflows from active region edges.
- To determine the impact of solar rotation and intrinsic activity on observed upflow evolution.
- To constrain the driving mechanisms of these upflows.
Main Methods:
- Observation of ten active regions (ARs) using Hinode/EIS as they transit the solar disk.
- Analysis of Doppler velocities and line widths of Fe xii spectral lines.
- Estimation of unprojected upflow velocity and inclination using projection effects from solar rotation.
Main Results:
- Observed long-term evolution of upflows is largely due to solar rotation, altering the viewpoint of stationary flows.
- Estimated unprojected upflow velocities fan away from AR cores (40° to vertical for following polarity; -29° to 28° for leading polarity).
- Intrinsic evolution of upflows, dependent on AR activity, is also identified.
- Line widths correlate with Doppler velocities only in ARs with very high velocities.
- Upflows frequently occur in pairs or multiple pairs, indicating a non-local driving mechanism.
Conclusions:
- Solar rotation significantly influences the apparent evolution of coronal upflows.
- Intrinsic AR activity also drives changes in upflow behavior.
- The common occurrence of paired upflows supports models involving reconnection along quasi-separatrix layers, rather than local mechanisms.
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