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The elemental composition of the Sun's hot atmosphere, the corona, shows a distinctive pattern that is different than the underlying surface, or photosphere (Pottasch 1963). Elements that are easy to ionize in the chromosphere are enhanced…

Solar and Stellar Astrophysics · Physics 2022-05-18 David H. Brooks , Deborah Baker , Lidia van Driel-Gesztelyi , Harry P. Warren , Stephanie L. Yardley

Heavy ion ratio abundances in Solar Energetic Particle (SEP) events, e.g.~Fe/O, often exhibit decreases over time. Using particle instruments on the ACE, SOHO and STEREO spacecraft, we analysed heavy ion data from 4 SEP events taking place…

Space Physics · Physics 2017-01-25 P. Zelina , S. Dalla , C. M. S. Cohen , R. A. Mewaldt

We report an observation of a partially erupting prominence and associated dynamical plasma processes based on observations recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The prominence…

Solar and Stellar Astrophysics · Physics 2015-06-17 Durgesh Tripathi , Katharine K. Reeves , Sarah E. Gibson , Abhishek Srivastava , Navin C. Joshi

We present results on carbon, nitrogen, and oxygen abundances for a sample of unevolved metal-poor stars with metallicities in the range -0.3< [Fe/H]< -3. Oxygen abundances derived from different indicators are compared showing consistently…

Astrophysics · Physics 2016-01-27 G. Israelian , R. Garcia Lopez , Rafael Rebolo

We analyze the evolution of Fe XII coronal plasma upflows from the edges of ten active regions (ARs) as they cross the solar disk using the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS). Confirming the results of Demoulin et al.…

Solar and Stellar Astrophysics · Physics 2017-04-12 Deborah Baker , Miho Janvier , Pascal Demoulin , Cristina Mandrini

Solar vortex regions show enhanced Poynting flux and favourable heating conditions, but how the vortices reorganize and influence their surroundings remains unclear. Here we apply information-theoretic diagnostics to a Bifrost simulation to…

Solar and Stellar Astrophysics · Physics 2025-11-21 Suzana S. A. Silva , Erico Rempel , Gary Verth , Istvan Ballai , Viktor Fedun

We study the effect of newly emerged solar active regions (ARs) on the large-scale magnetic environment of pre-existing ARs (PEARs). We first present a theoretical approach to quantify the "interaction energy" between new ARs and PEARs as…

Solar and Stellar Astrophysics · Physics 2016-06-09 Yixing Fu , Brian T. Welsch

A long-standing problem is to predict the future flare productivity of an active region (AR) when it is on the stage of early emergence. The aim of this study is to probe two parameters of the photospheric magnetic field, both derived…

Solar and Stellar Astrophysics · Physics 2020-11-25 Alexander S. Kutsenko , Valentina I. Abramenko , Olga K. Kutsenko

Emerging dimming occurs in isolated solar active regions (ARs) during the early stages of magnetic flux emergence. Observed by the Atmospheric Imaging Assembly, it features a rapid decrease in extreme-ultraviolet (EUV) emission in the 171…

Solar and Stellar Astrophysics · Physics 2021-05-05 Anna V. Payne , Xudong Sun

$PSP$ and $SolO$ data are utilized to investigate magnetic field intermittency in the solar wind (SW). Small-scale intermittency $(20-100d_{i})$ is observed to radially strengthen when methods relying on higher-order moments are considered…

We have studied the spatial and temporal distribution of abundances of chemical elements in large "gradual" solar energetic-particle (SEP) events, and especially the source plasma temperatures, derived from those abundances, using…

Solar and Stellar Astrophysics · Physics 2017-09-19 Donald V. Reames

We present a radiative magnetohydrodynamics simulation of the formation of an Active Region on the solar surface. The simulation models the rise of a buoyant magnetic flux bundle from a depth of 7.5 Mm in the convection zone up into the…

Solar and Stellar Astrophysics · Physics 2015-05-19 M. C. M. Cheung , M. Rempel , A. M. Title , M. Schüssler

We report multi-wavelength ultraviolet observations taken with the IRIS satellite, concerning the emergence phase in the upper chromosphere and transition region of an emerging flux region (EFR) embedded in the unipolar plage of active…

Solar and Stellar Astrophysics · Physics 2019-07-17 S. L. Guglielmino , F. Zuccarello , P. R. Young , P. Romano , M. Murabito

We investigate the self-consistent formation and long-term evolution of proton beams in the expanding solar wind using an ensemble of one-dimensional hybrid expanding box simulations. Initial conditions are chosen to represent a range of…

Space Physics · Physics 2026-02-24 J. S. Bianco , A. Tenerani , C. Gonzalez , L. Matteini , K. G. Klein

We present and discuss the strong correspondence between evolution of the emission length scale in the lower transition region and in situ measurements of the fast solar wind composition during this most recent solar minimum. We combine…

Solar and Stellar Astrophysics · Physics 2015-05-30 Scott W. McIntosh , Kandace K. Kiefer , Robert J. Leamon , Justin C. Kasper , Michael S. Stevens

Solar energetic particles (SEPs) in the energy range 10s KeV/nucleon-100s MeV/nucleon originate from Sun. Their high flux near Earth may damage the space borne electronics and generate secondary radiations harmful for the life on Earth and…

Plasma Physics · Physics 2025-07-18 Neeraj Jain , Jörg Büchner , Miroslav Bárta , Radoslav Bučík

The abrupt and permanent changes of photospheric magnetic field in the localized regions of active regions during solar flares called magnetic imprints (MIs), have been observed for the past nearly three decades. The well known "coronal…

Solar and Stellar Astrophysics · Physics 2022-03-14 N. Vasantharaju , P. Vemareddy , B. Ravindra , V. H. Doddamani

{In order to understand the emergence of the active region, we investigate the emerging process and magnetic properties of a naked anti-Hale active region during the period between August 24 to 25, 2018.} {Using the data from Helioseismic…

Solar and Stellar Astrophysics · Physics 2021-08-11 Jincheng Wang , Xiaoli Yan , Defang Kong , Zhike Xue , Liheng Yang , Qiaoling Li , Yan Zhang , Hao Li

Observations with JWST have revealed an unexpected high abundance of bright z>10 galaxy candidates. We explore whether a stellar initial mass function (IMF) that becomes increasingly top-heavy towards higher redshifts and lower gas-phase…

In-situ observations of the solar wind (SW) plasma from 0.29 to 1AU show that the protons and alpha particles are often non-Maxwellian, with evidence of kinetic instabilities, temperature anisotropies, differential ion streaming, and…

Space Physics · Physics 2019-05-15 Leon Ofman