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Mayank P., Vaidya B., and Chakrabarty D. 

The Astrophysical Journal Supplement Series

(Sep. 2022, volume 262, page 23)

This work presents an indigenous 3D solar wind model (SWASTi-SW). This numerical framework for forecasting the ambient solar wind is based on a well-established scheme that uses a semiempirical coronal model and a physics-based inner heliospheric model. This study demonstrates a more generalized version of the WSA relation, which provides a speed profile input to the heliospheric domain. Line-of-sight observations of GONG and HMI magnetograms are used as inputs for the coronal model, which in turn provides the solar wind plasma properties at 0.1 au. These results are then used as an initial boundary condition for the MHD model of the inner heliosphere to compute the solar wind properties up to 2.1 au. Along with the validation run for multiple Carrington rotations, the effect of variation of specific heat ratio and study of the SIR are also presented. This work showcases the multidirectional features of SIRs and provides synthetic measurements for potential observations from the SWIS subsystem of the ASPEX payload on board ISRO’s upcoming solar mission Aditya-L1.

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Mayank P., Vaidya B., Mishra W. and Chakrabarty D. 

The Astrophysical Journal Supplement Series

(Jan. 2024, volume 270, page 10)

Coronal mass ejections (CMEs) are primary drivers of space weather, and studying their evolution in the inner heliosphere is vital to prepare for a timely response. Solar wind streams, acting as background, influence their propagation in the heliosphere and associated geomagnetic storm activity. This study introduces SWASTi-CME, a newly developed MHD-based CME model integrated into the Space Weather Adaptive SimulaTion (SWASTi) framework. It incorporates a nonmagnetized elliptic cone and a magnetized flux rope CME model. To validate the model's performance with in situ observation at L1, two Carrington rotations were chosen: one during solar maxima with multiple CMEs, and one during solar minima with a single CME. The study also presents a quantitative analysis of CME–solar wind interaction using this model. To account for ambient solar wind effects, two scenarios of different complexity in solar wind conditions were established. The results indicate that ambient conditions can significantly impact some of the CME properties in the inner heliosphere. We found that the drag force on the CME front exhibits a variable nature, resulting in asymmetric deformation of the CME leading edge. Additionally, the study reveals that the impact on the distribution of CME internal pressure primarily occurs during the initial stage, while the CME density distribution is affected throughout its propagation. Moreover, regardless of the ambient conditions, it was observed that, after a certain propagation time (t), the CME volume follows a nonfractal power-law expansion (∝t3.03−3.33) due to the attainment of a balanced state with ambient.

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