Estimating the Poynting Flux of Alfvénic Waves in Polar Coronal Holes across Solar Cycle 24

The Astrophysical Journal, Journal Year: 2025, Volume and Issue: 985(1), P. 13 - 13

Published: May 12, 2025

Abstract Alfvénic waves are known to be prevalent throughout the corona and solar wind. Determining Poynting flux supplied by is required for constraining their role in plasma heating acceleration, as well providing a constraint Alfvén-wave-driven models that aim predict coronal wind properties. Previous studies of polar holes have been able provide measure energy arbitrary case studies. Here, we build upon previous work take more systematic approach, examining if there evidence any variation vertical over course cycle. We use imaging data from Solar Dynamics Observatory's Atmospheric Imaging Assembly displacements fine-scale structure present holes. It found broadly similar cycle, implying consistent contribution budget There across measurements (around 30%), but this suggested due differences individual rather than feature Our direct estimates agreement with recent Z. Huang et al., who constrain through comparison predicted properties Alfvénic-wave-driven turbulence those observed OMNI at 1 au. Taken together, both sets results points toward lack correlation between

Language: Английский

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Kepler main-sequence solar-like stars: surface rotation and magnetic-activity evolution

Frontiers in Astronomy and Space Sciences, Journal Year: 2024, Volume and Issue: 11

Published: March 15, 2024

While the mission’s primary goal was focused on exoplanet detection and characterization, Kepler made continues to make extraordinary advances in stellar physics. Stellar rotation magnetic activity are no exceptions. allowed for these properties be determined tens of thousands stars from main sequence up red giant branch. From photometry, this can achieved by investigating brightness fluctuations due active regions, which cause surface inhomogeneities, or through asteroseismology as oscillation modes sensitive fields. This review summarizes single main-sequence solar-like within field. We contextualize sample comparing it known transitions magnetic-activity evolution, such convergence (from saturated unsaturated regime activity) Vaughan-Preston gap. reviewing publicly available data, we also uncover one interesting finding related intermediate-rotation gap seen other surveys. find evidence previous ground-based data X-ray luminosity. Understanding complex evolution interplay between is crucial, sheds light fundamental processes governing including our own Sun.

Language: Английский

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Studying the Properties of Spacetime with an Improved Dynamical Model of the Inner Solar System

Universe, Journal Year: 2024, Volume and Issue: 10(11), P. 413 - 413

Published: Nov. 3, 2024

Physical properties of the Sun (orientation rotation axis, oblateness coefficient J2⊙, and change rate gravitational parameter μ˙⊙) are determined using a dynamical model describing motion Sun, planets, Moon, asteroids, Trans-Neptunian objects (TNOs). Among many kinds observations used to determine orbits physical bodies, most important for our study precise interplanetary ranging data: Earth–Mercury ranges from MESSENGER spacecraft Earth–Mars Odyssey MRO. The findings allow us improve in modern planetary ephemerides. First, dynamically direction Sun’s pole is ≈2° off visible axis surface, which corroborated by present knowledge interior. Second, found be smaller (in absolute value) than nominal value derived estimate mass loss through radiation solar wind. Possible interpretations discussed.

Language: Английский

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TESS Asteroseismology of β Hydri: A Subgiant with a Born-again Dynamo

The Astrophysical Journal, Journal Year: 2024, Volume and Issue: 974(1), P. 31 - 31

Published: Oct. 1, 2024

Abstract The solar-type subgiant β Hyi has long been studied as an old analog of the Sun. Although rotation period never measured directly, it was estimated to be near 27 days. As a Southern Hemisphere target, not monitored by long-term stellar activity surveys, but archival International Ultraviolet Explorer data revealed 12 yr cycle. Previous ground-based asteroseismology suggested that star is slightly more massive and substantially larger older than Sun, so similarity both rate cycle solar values perplexing. We use two months precise time-series photometry from Transiting Exoplanet Survey Satellite detect solar-like oscillations in determine fundamental properties asteroseismic modeling. also obtain direct measurement period, which previously ultraviolet activity–rotation relation. then rotational evolution modeling predict expected either standard spin-down or weakened magnetic braking (WMB). conclude consistent with WMB changes structure on branch can reinvigorate large-scale dynamo briefly sustain cycles. Our results support existence “born-again” evolved subgiants—previously explain 94 Aqr Aa—which best understood within scenario.

Language: Английский

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The impact of stellar metallicity on rotation and activity evolution in the Kepler field using gyro-kinematic ages

Monthly Notices of the Royal Astronomical Society, Journal Year: 2024, Volume and Issue: 533(2), P. 1290 - 1299

Published: July 30, 2024

ABSTRACT In recent years, there has been a push to understand how chemical composition affects the magnetic activity levels of main sequence low-mass stars. Results indicate that more metal-rich stars are magnetically active for given stellar mass and rotation period. This metallicity dependence implications periods evolve over their lifetimes. Numerical modelling suggests at late ages should be rotating slowly active. this work, we study evolution using sample Kepler field We use gyro-kinematic age dating technique estimate our photometric index as proxy activity. find clear evidence that, ages, have spun down slower in agreement with theoretical modelling. However, further investigation is required definitively determine whether occurs dependent way.

Language: Английский

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