Results 21 to 30 of about 334 (164)

Extrasolar planets, stellar winds and chromospheric hotspots [PDF]

Monthly Notices of the Royal Astronomical Society: Letters, 2006
Abstract Recent observations have shown what is believed to be planet-induced chromospheric activity on stars with hot Jupiters. We present a model of the magnetic interaction between a planet and a star with a dipolar magnetic field. Reconnection between the fields of the star and planet accelerates electrons along the field lines that ...
T. McIvor, M. Jardine, V. Holzwarth
openaire   +1 more source

Periodic Density Structures Observed in Ulysses Data: First Results

Journal of Geophysical Research: Space Physics, Volume 131, Issue 3, March 2026.
Abstract Periodic density structures (PDSs) are advecting quasi‐periodic (periodicities between several minutes and several hours) density enhancements observed in the solar wind and corona. There is strong evidence that PDSs are formed at the Sun.
Brent M. Randol, Nicholeen Viall, Larry Kepko, Simone Di Matteo   +3 more
wiley   +1 more source

Physical Parameters and Chromospheric Activity of Eclipsing Binaries Observed by the LAMOST DR10 Survey

The Astrophysical Journal Supplement Series
In this study, we present a comprehensive study of more than 50,000 spectra of 32,257 eclipsing binaries from the LAMOST DR10 survey, including 5200 systems with spectroscopy.
Ansong Shi, Li-yun Zhang, Tianhao Su, Yinpeng Wang, Qi An, Xianming L. Han, Prabhakar Misra, Linyan Jiang, Rui Guo, Qingfeng Pi   +9 more
doaj   +1 more source

On the Freeze‐In Distance of Solar Wind Fluid Entropy Variability in the Corona

Journal of Geophysical Research: Space Physics, Volume 131, Issue 3, March 2026.
Abstract The strong correlation between solar wind entropy and the frozen‐in ion charge state ratio O7+/O6+ ${\mathrm{O}}^{7+}/{\mathrm{O}}^{6+}$ indicates that entropy variability on timescales of hours or longer is preserved from its solar source. This prompts the question: where in the solar atmosphere does this entropy variability come from, and at
Aidan J. Nakhleh, Nicholeen M. Viall, Susan T. Lepri, Jim M. Raines   +3 more
wiley   +1 more source

In the Trenches of the Solar–Stellar Connection. VII. Wilson–Bappu 2022

The Astrophysical Journal Supplement Series, 2023
The Wilson–Bappu effect (WBE) is a remarkable correlation between the width of the chromospheric emission core of the Ca ii 3934 Å K line and stellar absolute visual magnitude over an astonishing range, from diminutive red dwarfs to bloated yellow ...
Thomas Ayres
doaj   +1 more source

Ultraviolet observations of stellar chromospheric activity

The Astrophysical Journal, 1982
A survey is presented of chromospheric and transition region (TR) line emission in late-type stars obtained with the IUE satellite. A wide variation in TR emission (ions formed near T = 100,000 K) at a given position in the H-R diagram is found, contradicting theories that incorporate only acoustic energy generation and deposition.
L. Hartmann, A. K. Dupree, J. C. Raymond
openaire   +1 more source

A New Method for Probabilistic Spatiotemporal Forecasts of Solar Soft X‐Ray “S‐Class” (>X10) Superflares

Journal of Geophysical Research: Space Physics, Volume 131, Issue 2, February 2026.
Abstract Solar superflares of S‐class (>X10 in soft X‐rays) pose extreme space weather hazards, yet their prediction remains a fundamental challenge owing to their rapid and transient natures and the limitations of conventional event‐based forecasts. We introduce for the first time, a probabilistic spatiotemporal framework designed to identify extended
V. M. Velasco Herrera, G. Velasco Herrera, W. Soon, A. Özgüç, N. Babynets, A. Tlatov, M. Švanda, S. Qiu, S. Baliunas, B. Kotan, G. González González, L. A. Bautista Flores, M. Pazos   +12 more
wiley   +1 more source

Magnetic Activity of TESS Objects Observed in the LAMOST Medium-resolution Spectral Survey

The Astrophysical Journal Supplement Series
A combination of spectroscopic and photometric observations provides an excellent data sample for studying stellar chromospheric activity. We have combined LAMOST medium-resolution spectra with TESS 2 minute light curves and extracted over 530,000 ...
Tianhao Su, Li-yun Zhang, Prabhakar Misra, Xianming L. Han, Yinpeng Wang, Wenjie Li, Zhongzhong Zhu, Qingfeng Pi, Hongpeng Lu   +8 more
doaj   +1 more source

Space Weather Impact of Three Solar Flares Observed by the POEMAS Telescope at 45 and 90 GHz

Journal of Geophysical Research: Space Physics, Volume 130, Issue 11, November 2025.
Abstract Solar flares are often associated with coronal mass ejections (CMEs) that, when directed toward Earth, can disrupt the magnetosphere and impact space weather. In this study, we investigate three long‐duration solar flares observed in 2012 by the POlarization Emission of Millimeter Activity at the Sun (POEMAS) telescopes at 45 and 90 GHz.
Adriana Valio, Karla F. Lopez, José Luis Gamonal Valenzuela, Ruben M. Romero Ramírez, Dougas F. da Silva   +4 more
wiley   +1 more source

The California Legacy Survey. VI. The Fate of Activity Cycles in Sun-like Stars

The Astronomical Journal
We analyze the spectra of 91 solar-type G- and K-type main-sequence dwarfs in the solar neighborhood to assess activity trends with stellar properties.
Howard Isaacson, Stephen R. Kane, Brad Carter, Andrew W. Howard   +3 more
doaj   +1 more source