Analysing the effects of apodizing windows on local correlation tracking using Nirvana simulations of convection

Abstract

We employ different shapes of apodizing windows in the local correlation tracking (LCT) routine to retrieve horizontal velocities using numerical simulations of convection. LCT was applied on a time sequence of temperature maps generated by the Nirvana code with four different apodizing windows, namely--Gaussian, Lorentzian, trapezoidal and triangular, with varying widths. In terms of correlations (between the LCT-retrieved and simulated flow field), the triangular and the trapezoidal perform the best and worst, respectively. On segregating the intrinsic velocities in the simulations on the basis of their magnitudes, we find that for all windows, a significantly higher correlation is obtained for the intermediate and high-velocity bins and only modest or weak values in the low-velocity bins. The differences between the LCT-retrieved and simulated flow fields were determined spatially which show large residuals at or close to the boundary of granules. The extent to which the horizontal flow vectors retrieved by LCT compare with the simulated values, depends entirely on the width of the central peak of the apodizing window for a given $\sigma$. Even though LCT suffers from a lack of spatial content as seen in simulations, its simplicity and speed could serve as a viable first-order tool to probe horizontal flows--one that is ideal for large data sets.

Accepted for publication in Solar Physics: 14 pages, 6 figures, 1 table

References in corpus (15)

• Simulations of stellar convection with CO5BOLD
• The Sunrise Mission
• Simulation of the Formation of a Solar Active Region
• Penumbral structure and outflows in simulated sunspots
• The intensity contrast of solar granulation: comparing Hinode SP results with MHD simulations
• Simulations of the solar near-surface layers with the CO5BOLD, MURaM, and Stagger codes
• Detection of vortex tubes in solar granulation from observations with Sunrise
• Vortices in simulations of solar surface convection
• Motions of Isolated G-Band Bright Points in the Solar Photosphere
• Are granules good tracers of solar surface velocity fields?
• Evaluating local correlation tracking using CO5BOLD simulations of solar granulation
• Reconstruction of an Inductive Velocity Field Vector from Doppler Motions and a Pair of Solar Vector Magnetograms
• The relation between photospheric supergranular flows and magnetic flux emergence
• The power spectrum of solar convection flows from high-resolution observations and 3D simulations
• The cross helicity at the solar surface by simulations and observations

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