Computation of Rotational Flow of the Sun Using Satellite Data and Doppler Shift Calculations

Ali Shan; Aarib Zaheer; Waleed Ajmal; Maira Ghazanfar; Hamid Gulzar

Authors

Ali Shan Institute of Space Science, University of the Punjab, Lahore, Pakistan
Aarib Zaheer Institute of Space Science, University of the Punjab, Lahore, Pakistan
Waleed Ajmal Institute of Space Science, University of the Punjab, Lahore, Pakistan
Maira Ghazanfar Institute of Space Science, University of the Punjab, Lahore, Pakistan
Hamid Gulzar University of the Punjab

Keywords:

CHASE, Doppler Velocity, Hα Line, Solar Differential Rotation, Solar Dynamics, Voigt Fitting

Abstract

Solar rotational flow governs the Sun’s magnetic activity, space weather variability, and long-term dynamo processes. Traditional tracer-based techniques offer limited precision in mapping these flows, creating the need for direct spectroscopic velocity measurements. This study presents a computational framework for deriving full-disk Doppler velocity maps of the Sun using high-resolution Hα spectra from the Chinese H-alpha Solar Explorer (CHASE) mission. The H-alpha Imaging Spectrograph (HIS) data cube (2304 × 2313 × 46 pixels) was processed through a workflow of preprocessing, continuum normalization, Voigt profile fitting, and pixel-wise Doppler conversion to retrieve line-of-sight velocities. The resulting field of ~5.3 million pixels shows clear differential rotation, with blue shifts up to −7.89 km s⁻¹ on the approaching limb and red shifts up to +2.19 km s⁻¹ on the receding limb, corresponding to equatorial and polar rotation periods of ~25 and ~31 days, respectively. Localized asymmetries in active regions further reveal small-scale velocity perturbations. These results validate CHASE–HIS spectroscopy as a reliable tool for global solar flow diagnostics and highlight the utility of Voigt-based Doppler modeling in resolving fine-scale plasma dynamics. The developed approach bridges spectroscopic and Helio seismic methods, offering a reproducible foundation for future studies on solar dynamo modeling and space weather prediction.

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