J/A+A/587/A29 Time and positions of coronal bright points (Sudar+, 2016)
Meridional motions and Reynolds stress from SDO/AIA coronal bright points data.
Sudar D., Saar S.H., Skokic I., Poljancic Beljan I., Brajsa R.
<Astron. Astrophys. 587, A29 (2016)>
=2016A&A...587A..29S 2016A&A...587A..29S (SIMBAD/NED BibCode)
ADC_Keywords: Sun
Keywords: Sun: rotation - Sun: corona - Sun: activity
Abstract:
It is possible to detect and track coronal bright points (CBPs) in
Solar Dynamics Observatory / Atmospheric Imaging Assembly (SDO/AIA)
images. A combination of high resolution and high cadence provides a
wealth of data that can be used to determine velocity flows on the
solar surface with very high accuracy. We derived a very accurate
solar rotation profile and investigated meridional flows, torsional
oscillations, and horizontal Reynolds stress based on ∼6 months of
SDO/AIA data. We used a segmentation algorithm to detect CBPs in
SDO/AIA images. We also used invariance of the solar rotation profile
with central meridian distance (CMD) to determine the height of CBPs
in the 19.3nm channel. The best fit solar rotation profile is given
by ω(b)=(14.4060±0.0051+(-1.662±0.050)sin2b+
(-2.742±0.081)sin4b)°/day. The height of CBPs in the SDO/AIA
19.3nm channel was found to be ∼6500km. Meridional motion is
predominantly poleward for all latitudes, while solar velocity
residuals show signs of torsional oscillations. Horizontal Reynolds
stress was found to be smaller than in similar works, but still showed
transfer of angular momentum towards the solar equator. Most of the
results are consistent with Doppler measurements rather than tracer
measurements. The fairly small calculated value of horizontal Reynolds
stress might be due to the particular phase of the solar cycle.
Accuracy of the calculated rotation profile indicates that it is
possible to measure changes in the profile as the solar cycle evolves.
Analysis of further SDO/AIA CBP data will also provide a better
understanding of the temporal behaviour of the rotation velocity
residuals, meridional motions, and Reynolds stress.
Description:
Positional information about CBPs detected by the segmentation
algorithm are presented. For each CBP time in Julian days (JD) and x
and y coordinates in pixels are given.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 46 4758248 Time in JD and position of CBPs in pixels
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d JD Julian Date of observation (JD-2450000.0)
12- 20 I9 --- ID ID number of CBP
21- 33 F13.6 pix xPos x position of CBP in pixels
34- 46 F13.6 pix yPos y position of CBP in pixels
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Acknowledgements:
Davor Sudar, davor.sudar(at)gmail.com
(End) Davor Sudar [Hvar Obs., Croatia], Patricia Vannier [CDS] 11-Jan-2016