Results 41 to 50 of about 334 (164)

Solar Wind Heavy Ions and Alpha Particles Within Earth's Magnetosphere and Their Variability With Upstream Conditions

Journal of Geophysical Research: Space Physics, Volume 130, Issue 8, August 2025.
Abstract Working toward the goal of understanding solar wind (SW) entry to the Earth's magnetosphere, this study examines solar‐origin ion composition in the magnetotail. During its trajectory, Wind spent a significant amount of time in the Earth's magnetotail, where its SupraThermal Ion Composition Spectrometer (STICS) measured the mass and mass per ...
S. Colón‐Rodríguez, M. W. Liemohn, J. M. Raines, S. T. Lepri   +3 more
wiley   +1 more source

The Near-infrared Ca ii Triplet as a Stellar Activity Indicator: A Library and Comparative Study

The Astrophysical Journal Supplement Series
We have established and released a new stellar index library of the Ca ii triplet, which serves as an indicator for characterizing the chromospheric activity of stars.
Xin Huang, Yuji He, Zhongrui Bai, Hailong Yuan, Mingkuan Yang, Ming Zhou, Yiqiao Dong, Mengxin Wang, Han He, Jinghua Zhang, Yaoquan Chu, Yongheng Zhao, Yong Zhang, Haotong Zhang   +13 more
doaj   +1 more source

Magnetic Activity in M-type Stars Based on LAMOST DR11 and TESS Observations

The Astrophysical Journal Supplement Series
We have used 898,351 M-type stellar spectra released by Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR11 to calculate the equivalent width of the Ca II infrared triplet (IRT) lines, the residual chromospheric emission, and the parameter ${R}
Linfeng Ren, Li-yun Zhang, Xianming L. Han, Tianhao Su, Wenjie Li, Yinpeng Wang, Prabhakar Misra   +6 more
doaj   +1 more source

Stellar activity with LAMOST – II. Chromospheric activity in open clusters [PDF]

Monthly Notices of the Royal Astronomical Society, 2018
We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and Hyades to study how chromospheric activity vary as a function of mass and rotation at different age. We measured excess equivalent widths of H$ $, H$ $, and Ca~{\sc ii} K based on estimated chromospheric contributions from old and inactive field dwarfs, and excess luminosities ...
Fang, Xiang-Song, Zhao, Gang, Zhao, Jing-Kun, Kumar, Yerra Bharat   +3 more
openaire   +2 more sources

Slow Solar Wind: Origin in an Independent Small‐Scale Solar Dynamo

Geophysical Research Letters, Volume 52, Issue 13, 16 July 2025.
Abstract Separation of the solar wind (SW) into three flow types (coronal mass ejections (CMEs), high speed streams (HSSs), and slow solar wind (SSW)) reveals an inverse relationship between the percentage of time Earth spends in SSW during a year and its annually averaged magnetic field strength (B).
E. W. Cliver, I. G. Richardson, S. F. Martin   +2 more
wiley   +1 more source

Predicting Photospheric Ultraviolet Emission from Stellar Evolutionary Models

The Astrophysical Journal
Stellar ultraviolet (UV) emission serves as a crucial indicator for estimating magnetic activity and evaluating the habitability of exoplanets orbiting stars.
Song Wang, Xue Li, Henggeng Han, Jifeng Liu   +3 more
doaj   +1 more source

Wavelet Analysis of Stellar Chromospheric Activity Variations

The Astrophysical Journal, 1997
Observations of chromospheric activity variations for some lower main-sequence stars from the Mount Wilson Observatory's HK project reveal a cyclic behavior comparable to the sunspot cycle. Even in the relatively short interval that they have been observed, those stars show stellar cycles and other features, like grand minima. The quasi-periodic nature
P. Frick, S. L. Baliunas, D. Galyagin, D. Sokoloff, W. Soon   +4 more
openaire   +1 more source

Robust Statistical Techniques for Operational Maintenance of the 10.7 cm Solar Radio Flux

Space Weather, Volume 23, Issue 5, May 2025.
Abstract The F10.7 solar radio flux is a critical quantity for operational space weather nowcasting and forecasting, where it is routinely used as a driver for coupled atmospheric models to estimate a variety of important quantities such as the neutral atmospheric density.
Daniel A. Brandt, Erick F. Vega, Brian J. Thelen   +2 more
wiley   +1 more source

Far-ultraviolet Emission Line Investigation of Flares on AU Mic

The Astrophysical Journal
The role of nonthermal proton energy transportation during solar and stellar flares is largely unknown; a better understanding of this physical process will allow us to rectify longstanding deficiencies in flare models.
Adalyn Gibson, Adam F. Kowalski, Adina D. Feinstein   +2 more
doaj   +1 more source

Quasi‐Periodic Pulsations in Ionospheric TEC Synchronized With Solar Flare EUV Emission

Journal of Geophysical Research: Space Physics, Volume 130, Issue 4, April 2025.
Abstract The extreme ultraviolet (EUV) and X‐ray radiation emitted during solar flares has been shown to significantly increase the electron density of the Earth's ionosphere. During flares, quasi‐periodic pulsations in X‐ray flux originating in the corona have previously been linked to subsequent pulsations in the Earth's ionospheric D‐region. Similar
Aisling N. O’Hare, Susanna Bekker, Laura A. Hayes, Ryan O. Milligan   +3 more
wiley   +1 more source