Exploring the influence of the ‘Smiley Sun’ on the dynamics of inner solar corona and near-Earth space environment

Abstract

ABSTRACT The image captured by SDO/AIA (Solar Dynamics Observatory) in the 193 Å ultraviolet channel from 2022 October 25–27, unveiled a remarkable trio of dark coronal holes near the heliocentric equator, forming a distinctive smiling face. Serendipitously, during that period, coronal radio science experiments were being conducted using the Akatsuki spacecraft to investigate turbulence regimes in the inner-middle corona and track the acceleration of solar wind streams. By analysing Doppler frequency residuals, we derived valuable insights into plasma turbulence characteristics, estimated electron density fluctuations and flow speeds using isotropic quasi-static turbulence methods. The analysis consistently unveiled a shallow turbulence spectrum and flow speeds ranging from 180 to 400 km s−1 at heliocentric distances of 3–9 Rs. During this period, the solar wind flow speed, recorded at the L1 point near Earth, was of the order of 600–650 km s−1. This presented a unique opportunity to delve into turbulence within the inner corona and explore the mechanisms responsible for energizing and accelerating high-speed streams emanating from these trans-equatorial coronal holes. The study also suggests the innovative use of spacecraft signals as radio beacons for enhanced forecasting of potential space weather events triggered by Earth-directed high-speed solar wind streams.