Ablation of Persistent and Long Lasting Persistent Atrial Fibrillation
Persistent structures in near-surface flows from ring diagrams
description
Transcript of Persistent structures in near-surface flows from ring diagrams
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PERSISTENT STRUCTURES IN NEAR-
SURFACE FLOWS FROM RING DIAGRAMS
RACHEL HOWE, UNIVERSITY OF BIRMINGHAM
D. BAKER, L. HARRA, MSSL
R. KOMM, NSO
R. BOGART, STANFORD
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PROBING THE SUN INSIDE AND OUTLeverhulme-funded project at MSSL
1st Workshop June 2011
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INTRODUCTION
• The Sun has flows at many scales, from global rotation to flows around active regions and down to granules.
• Many of these show variations with solar cycle.
• Here we are looking for persistent structures in local flow features over an extended period.
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DIFFERENTIAL ROTATION
• 2D rotation profile, based on RLS inversions
• Faster near equator, slower at poles
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ANALYSIS
• Use synoptic maps of zonal/meridional flows from ring diagrams (GONG and HMI)
• Average over all depths
• At each latitude and rotation, we subtract mean over all times/longitudes to remove differential rotation and first-order temporal variations such as the torsional oscillation (as well as systematic effects)
• Then plot residuals as longitude—time maps
• Differential rotation causes features to drift in longitude from one rotation to the next.
• Features (e.g., flows into active regions/remnants) persisting for more than one rotation will show up as diagonal streaks
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GONG ZONAL VELOCITYLONGITUDE—TIME PLOTS
Note diagonal ‘grain’
Paired light-dark streaks suggest flows into or out of feature that drifts with differential rotation.
Slope up == faster than Carrington rate
Slope down == slower than C.R.
Shallower slope means more difference.
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GONG MERIDIONAL VELOCITY
Not much to see here – quieter at minimum?
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MDI/HMI MAGNETOGRAMS(Timescale of GONG)
Note slope of features differs from that seen in flows
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GONG ZONAL VELOCITYOn HMI timescale.
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HMI ZONAL VELOCITYNote strong stripes at high latitudes.
For common data, correlation with GONG is > 80%
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HMI MERIDIONAL VELOCITYSome grain visible here too.
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HMI MAGNETOGRAMS
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DIFFERENTIAL ROTATION
Use cross-correlation analysis to translate stripes slope to rotation rate
Green – Magnetograms
Black – Global inversions
Red – HMI ring vx correlation
Blue – GONG ring vx correlation
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DIFFERENTIAL ROTATION
Use cross-correlation analysis to translate stripes slope to rotation rate
Green – Magnetograms
Black – Global inversions
Red – HMI ring vx correlation
Blue – GONG ring vx correlation
Cyan – EIT 195 Angstrom correlation
Orange – GONG PFSS coronal hole maps
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HIGH-LATITUDE VX REWRAPPED WITH ESTIMATED VELOCITY
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HIGH-LATITUDE VX REWRAPPED WITH EST. VELOCITY -5 NHZ
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DISCUSSION
• Near-surface flows –especially zonal – show signatures of features persisting from a few to many rotations, migrating as would be expected from differential rotation.
• Low latitudes traceable to active region/plage?
• Rotation rate from magnetic features not quite the same as from flows – anchoring depth?
• High latitudes – Hathaway giant cells? Looks like an l=1 structure, anticorrelated n/s.
• Correlation analysis not good enough to pick up changes in differential rotation.