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Solar Physics

, Volume 290, Issue 2, pp 321–333 | Cite as

Families of Granules, Flows, and Acoustic Events in the Solar Atmosphere from Hinode Observations

  • J.-M. MalherbeEmail author
  • T. Roudier
  • Z. Frank
  • M. Rieutord
Article

Abstract

We investigate the relationship between trees of fragmenting granules (TFG), horizontal and vertical flows, and acoustic events (AE) in the photospheric network. AE are spatially concentrated and short-duration locations of acoustic energy flux. We performed observations at disk center of a 2D field of view (FOV) with high spatial and temporal resolutions provided by the Solar Optical Telescope onboard Hinode. Line profiles of Fe i 557.6 nm were recorded by the Narrow-band Filter Imager on an 80″×36″ FOV during five hours with a cadence of 22 seconds and 0.08″ pixel size. Vertical velocities were derived at two atmospheric levels allowing the determination of the energy flux at the acoustic frequency of 3.3 mHz. Families of granules and horizontal velocities were obtained from local correlation tracking (LCT) after segmentation and labeling of either continuum intensities or granular Doppler shifts. AE exhibit durations in the range 0.25 to 1 hour compatible with the lifetime of families (80 % do not last more than two hours). High-energy AE have the shortest lifetimes. We found that most AE occur in intergranular lanes located in or close to the boundaries between different families (called inter families) in regions with predominantly downward vertical motions and horizontal converging flows. In contrast, diverging flows are observed inside families, with a few AE in the intergranules. At the beginning of the sequence, when families are not yet detected, the distribution of AE is not uniform and is already organized at spatial lengths related to the mesogranular scale, with maximum contribution in the range 5″ to 10″, fully compatible with the scale of the maximum contribution of families in the TFG space. Although all sizes and durations seem to exist for families, their number decreases with increasing size and lifetime.

Keywords

Granulation Mesogranulation Dynamics Acoustic waves Photosphere 

Notes

Acknowledgments

We are indebted to the Hinode team for the possibility to use their data. Hinode is a Japanese mission developed and launched by ISAS/JAXA, collaborating with NAOJ as a domestic partner, NASA and STFC (UK) as international partners. Scientific operation of the Hinode mission is conducted by the Hinode science team organized at ISAS/JAXA. This team mainly consists of scientists from institutes in the partner countries. Support for the post-launch operation is provided by JAXA and NAOJ (Japan), STFC (UK), NASA, ESA, and NSC (Norway). The authors thank the anonymous referee for helpful comments and suggestions. This work was supported by the Centre National de la Recherche Scientifique (C.N.R.S.), France.

Supplementary material

11207_2014_630_MOESM1_ESM.mp4 (20.1 mb)
Families of granules and Doppler shifts in Fe i 557.6 nm. Granules belonging to the same family have uniform gray level corresponding to the family number. Families can be identified as mesogranules. Doppler velocities appear in blue/red for, respectively, upward/downward motions and affect both granules (mainly upward) and intergranules (mostly downward). Families detected by the LCT need several hours to appear (MP4 20.1 MB)
11207_2014_630_MOESM2_ESM.mp4 (20.3 mb)
Families of granules and Doppler gradient in Fe i 557.6 nm. Vertical gradients (through a 50 km layer) of velocities (core/inflection point difference) appear in blue/red, respectively, for positive/negative values. Positive gradients are dominant in intergranules (MP4 20.3 MB)
11207_2014_630_MOESM3_ESM.mp4 (20 mb)
Interfamilies, horizontal motions and AE. The boundaries between families of granules (interfamilies) are shown in gray. AE (white) form close to interfamilies. Quadratic horizontal velocities appear in gray levels with maxima mostly located inside families (MP4 20.0 MB)
11207_2014_630_MOESM4_ESM.mp4 (19.9 mb)
Interfamilies, divergence of horizontal velocities and AE. Diverging/converging areas are, respectively, blue/red. Most diverging regions are located inside families, while boundaries (interfamilies) together with AE are more often associated to converging patterns (MP4 19.9 MB)
11207_2014_630_MOESM5_ESM.mp4 (10 mb)
AE are flux concentrations in space and time with lifetime in the range 0.25 to 1 hour. Upward/downward flux is shown, respectively, in white/black. The spatial distribution is not uniform: most of the flux is located near the boundaries between TFG (interfamilies at mesogranular scale) (MP4 10.0 MB)
11207_2014_630_MOESM6_ESM.mp4 (20.3 mb)
Families of granules (gray levels) and AE. The major part of the flux (upward/downward, respectively, in blue/red) occur in intergranular lanes close to the boundaries between families (interfamilies). AE and families have lifetimes of the same order of magnitude (MP4 20.3 MB)
11207_2014_630_MOESM7_ESM.mp4 (20.1 mb)
Families of granules and AE. Granules belonging to the same family have uniform color. Most AE (white) appear in dark intergranular regions close to the boundaries between families (MP4 20.1 MB)

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • J.-M. Malherbe
    • 1
    Email author
  • T. Roudier
    • 2
  • Z. Frank
    • 3
  • M. Rieutord
    • 2
  1. 1.LESIAObservatoire de ParisMeudonFrance
  2. 2.IRAP, Université de ToulouseCNRSToulouseFrance
  3. 3.Lockheed Martin Solar and Astrophysics LaboratoryPalo AltoUSA

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