Comparison of solar horizontal velocity fields from SDO/HMI and Hinode data

Abstract

The measurement of the Sun's surface motions with a high spatial and temporal resolution is still a challenge. We wish to validate horizontal velocity measurements all over the visible disk of the Sun from Solar Dynamics Observatory/ Helioseismic and Magnetic Imager (SDO/HMI) data. Horizontal velocity fields are measured by following the proper motions of solar granules using a newly developed version of the Coherent Structure Tracking (CST) code. The comparison of the surface flows measured at high spatial resolution (Hinode, 0.1 arcsec) and low resolution (SDO/HMI, 0.5 arcsec) allows us to determine corrections to be applied to the horizontal velocity measured from HMI white light data. We derive horizontal velocity maps with spatial and temporal resolutions of respectively 2.5 Mm and 30 min. From the two components of the horizontal velocity Vx and Vy measured in the sky plane and the simultaneous line of sight component from SDO/HMI dopplergrams v_D, we derive the spherical velocity components (Vr, Vtheta, Vphi). The azimuthal component Vphi gives the solar differential rotation with a high precision (+-0.037km/s) from a temporal sequence of only three hours. By following the proper motions of the solar granules, we can revisit the dynamics of the solar surface at high spatial and temporal resolutions from hours to months and years with the SDO data.

8 pages, 13 figures, accepted in Astronomy and Astrophysics

References in corpus (2)

• Tracking granules on the Sun's surface and reconstructing horizontal velocity fields: I. the CST algorithm
• Helioseismology challenges models of solar convection

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• Statistics of Photospheric Supergranular Cells Observed by SDO/HMI
• Texture of average solar photospheric flows and the donut-like pattern
• Observational characterisation of large-scale transport and horizontal turbulent diffusivity in the quiet Sun
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