Automatic recognition and characterisation of supergranular cells from photospheric velocity fields

Potts, H.E. and Diver, D.A. (2008) Automatic recognition and characterisation of supergranular cells from photospheric velocity fields. Solar Physics, 248(2), pp. 263-275. (doi: 10.1007/s11207-007-9068-5)

Abstract

We have developed an exceptionally noise resistant method for accurate and automatic identification of supergranular cell boundaries from velocity measurements. Due to its high noise tolerance the algorithm can produce reliable cell patterns with only very small amounts of smoothing of the source data in comparison to conventional methods. In this paper we describe the method and test it with simulated data. We then apply it to the analysis of velocity fields derived from high-resolution continuum data from MDI (Michelson Doppler Imager) on SOHO. From this, we can identify certain basic properties of supergranulation cells, such as their characteristic sizes, the flow speeds within cells and their dependence on cell areas at high resolution. The effect of the noise and smoothing on the derived cell boundaries is investigated and quantified using simulated data. We show in detail the evolution of supergranular cells over their lifetime, including observations of emerging, splitting, and coalescing cells. A key result of our analysis of cell internal velocities is that there is a simple linear relation between cell size and cell internal velocity, rather than the power law usually suggested.

• Item Type: Articles
• Keywords: Photosphere, supergranulation, granules, photospheric flow.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Potts, Hugh and Diver, Professor Declan
• Authors: Potts, H.E., and Diver, D.A.
• Subjects: Q Science > QB Astronomy; Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Research Group: Astronomy
• Journal Name: Solar Physics
• Publisher: Springer Verlag
• ISSN: 0038-0938
• ISSN (Online): 1573-093X
• Published Online: 13 November 2007
• Copyright Holders: Copyright © 2007 Springer
• First Published: First published in Solar Physics 248(2):263-275
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
46593	1	Solar, stellar and cosmological plasmas: a synthesis of data, modelling and theory.	Declan Diver	Science & Technologies Facilities Council (STFC)	ST/F002149/1	Physics and Astronomy