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Perhaps the most compelling evidence for the role of magnetic reconnection in solar flares comes from the supra-arcade downflows that have been observed above many post-flare loop arcades. These downflows are thought to be related to highly…

Solar and Stellar Astrophysics · Physics 2015-05-30 Harry P. Warren , Casey M. O'Brien , Neil R. Sheeley

One of the key challenges in solar and heliospheric physics is to understand the acceleration of the solar wind. As a super-sonic, super-Alfv\'enic plasma flow, the solar wind carries mass, momentum, energy, and angular momentum from the…

Solar and Stellar Astrophysics · Physics 2021-08-11 Daniel Verscharen , Stuart D. Bale , Marco Velli

We investigate the origin of mesoscale structures in the solar wind called microstreams defined as enhancements in solar wind speed and temperature that last several hours. They were first clearly detected in Helios and Ulysses solar wind…

Solar and Stellar Astrophysics · Physics 2023-10-24 Bahaeddine Gannouni , Victor Réville , Alexis Rouillard

The origin of solar transition region redshifts is not completely understood. Current research is addressing this issue by investigating three-dimensional magneto-hydrodynamic models that extend from the photosphere to the corona. By…

Solar and Stellar Astrophysics · Physics 2015-05-28 Pia Zacharias , Sven Bingert , Hardi Peter

In May 2024, the Sun exhibited intense magnetic activity, marked by numerous high-intensity flares resulting from the interaction and merging of NOAA ARs 13664 and 13668 in the southern hemisphere and AR 13663 in the northern hemisphere.…

Solar and Stellar Astrophysics · Physics 2025-07-04 B Lekshmi , Sushanta Tripathy , Kiran Jain , Alexei Pevtsov

Arch filament systems (AFSs) are chromospheric and coronal manifestations of emerging magnetic flux. Using high spatial resolution observations taken at a high cadence by the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter, we…

Solar and Stellar Astrophysics · Physics 2024-11-13 Yajie Chen , Sudip Mandal , Hardi Peter , Lakshmi Pradeep Chitta

Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which…

Solar flares are one of the main forces behind space weather events. However the mechanism that drives such energetic phenomena is not fully understood. The standard eruptive flare model predicts that magnetic reconnection occurs high in…

Solar and Stellar Astrophysics · Physics 2015-06-17 S. Imada , K. Aoki , H. Hara , T. Watanabe , L. K. Harra , T. Shimizu

We analyze the complete chain of effects caused by a solar eruptive event in order to better understand the dynamic evolution of magnetic-field related quantities in interplanetary space, in particular that of magnetic flux and helicity. We…

Solar and Stellar Astrophysics · Physics 2023-01-11 J. K. Thalmann , M. Dumbovic , K. Dissauer , T. Podladchikova , G. Chikunova , M. Temmer , E. Dickson , A. M. Veronig

The solar interior is filled with turbulent thermal convection, which plays a key role in the energy and momentum transport and the generation of the magnetic field. The turbulent flows in the solar interior cannot be optically detected due…

Solar and Stellar Astrophysics · Physics 2024-10-10 Hiroyuki Masaki , Hideyuki Hotta

Massive star-forming regions (MSFRs) are commonly associated with hub-filament systems (HFSs) and sites of cloud-cloud collision (CCC). Recent observational studies of some MSFRs suggest a possible connection between CCC and the formation…

Astrophysics of Galaxies · Physics 2024-08-14 A. K. Maity , T. Inoue , Y. Fukui , L. K. Dewangan , H. Sano , R. I. Yamada , K. Tachihara , N. K. Bhadari , O. R. Jadhav

In the corona, plasma is accelerated to hundreds of kilometers per second, and heated to temperatures hundreds of times hotter than the Sun's surface, before it escapes to form the solar wind. Decades of space-based experiments have shown…

The variability of helium abundance in the solar corona and the solar wind is an important signature of solar activity, solar cycle, solar wind sources, as well as coronal heating processes. Motivated by recently reported remote sensing UV…

Solar and Stellar Astrophysics · Physics 2024-06-24 Leon Ofman , Yogesh , Silvio Giordano

Galactic winds are a crucial player in galaxy formation and evolution, but observations of them have proven extraordinarily difficult to interpret, leaving large uncertainties even in basic quantities such as mass outflow rates. Part of…

Astrophysics of Galaxies · Physics 2022-11-30 Yuxuan Yuan , Mark R. Krumholz , Crystal L. Martin

The connection between turbulence and solar-wind acceleration, long known in space physics, is further developed in this Letter by establishing a robust empirical law that relates the bulk-flow speed to the magnetohydrodynamic-scale…

Space Physics · Physics 2026-04-14 Rohit Chhiber , Yanwen Wang , Manuel E. Cuesta , Jiaming Wang , Sohom Roy

Chromospheric activities prior to solar flares provide important clues to solar flare initiation, but are as yet poorly understood. We report a significant and rapid H$\alpha$ line broadening before the solar flare SOL2011-09-29T18:08, that…

Solar and Stellar Astrophysics · Physics 2020-05-14 Kyuhyoun Cho , Jeongwoo Lee , Jongchul Chae , Haimin Wang , Kwangsu Ahn , Heesu Yang , Eun-kyung Lim , Ram Ajor Maurya

Disconnection of open magnetic flux by reconnection is required to balance the injection of open flux by CMEs and other eruptive events. Making use of recent advances in heliospheric background subtraction, we have imaged many abrupt…

Solar and Stellar Astrophysics · Physics 2015-06-03 C. E. DeForest , T. A. Howard , D. J. McComas

Fast and slow solar wind have distinct properties linked to their solar sources.Alfv\'enic slow wind complicates the usual speed-based classification, especially at intermediate speeds. Solar Orbiter's Solar Wind Analyzer (SWA) offers…

In space weather studies and forecasting we employ magnetohydrodynamic (MHD) simulations which can provide rather accurate reconstruction of the solar wind dynamics and its evolution. However, all MHD simulations are restricted by the input…

Solar and Stellar Astrophysics · Physics 2023-06-14 G. M. Shaifullah , J. Magdalenic , C. Tiburzi , I. Jebaraj , E. Samara , P. Zucca

We present a new optical Tully-Fisher (TF) investigation for a complete, full-sky sample of 297 Sb-Sc spirals with redshifts between 4500 and 7000 km/s. The survey was specifically designed to provide uniform, well- calibrated data over…

Astrophysics · Physics 2007-05-23 S. Courteau , J. Willick , M. Strauss , D. Schlegel , M. Postman