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Magnetic flux ropes (FRs) are twisted structures appearing on the sun, predominantly in the magnetically concentrated regions. These structures appear as coronal features known as filaments or prominences in H$\alpha$ observations, and as…

Solar and Stellar Astrophysics · Physics 2024-10-04 P. Vemareddy

We present a method for performing data-driven simulations of solar active region formation and evolution. The approach is based on magnetofriction, which evolves the induction equation assuming the plasma velocity is proportional to the…

Solar and Stellar Astrophysics · Physics 2015-06-11 Mark C. M. Cheung , Marc L. DeRosa

Rapid Blue Excursions (RBEs) are transient blue-shifted chromospheric absorption features widely interpreted as the on-disk counterparts of Type II solar spicules. We investigate their dynamic properties using high-cadence spectral…

Solar and Stellar Astrophysics · Physics 2026-02-27 Govindswaroop Rahangdale

We use high spatial resolution observations and numerical simulations to study the velocity distribution of solar photospheric magnetic bright points. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere…

Coronal pseudostreamer flux systems have a specific magnetic configuration that influences the morphology and evolution of coronal mass ejections (CMEs) from these regions. Here we continue the analysis of the Wyper et al. (2024, ApJ 975,…

Recent detections of high-energy $\gamma$-rays from behind-the-limb (BTL) solar flares by the \emph{Fermi $\gamma$-ray Space Telescope} pose a puzzle and challenge on the particle acceleration and transport mechanisms. In such events, the…

Solar radio spikes are short duration and narrow bandwidth fine structures in dynamic spectra observed from GHz to tens of MHz range. Their very short duration and narrow frequency bandwidth are indicative of sub-second small-scale energy…

Solar and Stellar Astrophysics · Physics 2021-08-31 Daniel L. Clarkson , Eduard P. Kontar , Mykola Gordovskyy , Nicolina Chrysaphi , Nicole Vilmer

The Mg II h&k lines form in the middle to upper chromosphere and are well-suited to study the structure of the chromosphere. However, the details of their formation in the solar chromosphere are not fully understood. We aim to study the…

Solar and Stellar Astrophysics · Physics 2026-05-25 P. Ondratschek , D. Przybylski , H. N. Smitha , J. Leenaarts , R. Cameron , S. K. Solanki

The Solar Hemispherical Helicity Rule(s) (SHHR) is a term used to represent a bias observed in proxies for the magnetic helicity in active regions at the solar surface. The SHHR states that predominantly negative magnetic helicity is…

Solar and Stellar Astrophysics · Physics 2026-02-10 Jacob B. Noone Wade , Nicholas H. Brummell

The origin of the near-ultraviolet and optical continuum radiation in flares is critical for understanding particle acceleration and impulsive heating in stellar atmospheres. Radiative-hydrodynamic simulations in 1D have shown that high…

Solar and Stellar Astrophysics · Physics 2018-01-10 Adam F. Kowalski , Joel C. Allred

The photometric variations due to magnetically confined material around He-strong stars are investigated within the framework of the Rigidly Rotating Magnetosphere (RRM) model. For dipole field topologies, the model is used to explore how…

Astrophysics · Physics 2009-11-13 R. H. D. Townsend

Active regions often host large-scale gas flows in the chromosphere presumably directed along curved magnetic field lines. Spectropolarimetric observations of these flows are critical to understanding the nature and evolution of their…

Solar and Stellar Astrophysics · Physics 2011-01-05 Tom Schad , Sarah Jaeggli , Haosheng Lin , Matthew Penn

Emission of solar flares across the electromagnetic spectrum is often observed in the form of two expanding ribbons. The standard flare model explains the flare ribbons as footpoints of magnetic arcades, emitting due to interaction of…

Solar and Stellar Astrophysics · Physics 2015-06-19 I. N. Sharykin , A. G. Kosovichev

The solar chromosphere contains thin, highly dynamic strands of plasma known as spicules. Recently, it has been suggested that the smallest and fastest (Type II) spicules are identical to intermittent jets observed by the Interface Region…

Solar and Stellar Astrophysics · Physics 2015-10-14 Steven R. Cranmer , Lauren N. Woolsey

High-spectral resolution observations using the VTT echelle spectrograph in the chromospheric H$\alpha$ line were obtained in the early growth phase of active region NOAA 12722. Noise-stripped H$\alpha$ line profiles yield maps of line-core…

Solar and Stellar Astrophysics · Physics 2020-07-08 M. Verma , C. Denker , A. Diercke , C. Kuckein , H. Balthasar , E. Dineva , I. Kontogiannis , P. S. Pal , M. Sobotka

We present radiative hydrodynamic simulations of solar flares generated by the RADYN and RH codes to study the perturbations induced in photospheric Fe I lines by electron beam heating. We investigate how variations in the beam parameters…

Solar and Stellar Astrophysics · Physics 2021-07-07 Aaron J. Monson , Mihalis Mathioudakis , Aaron Reid , Ryan Milligan , David Kuridze

Solar active regions (ARs) are thought to be formed by magnetic fields from the convection zone. Our flux emergence simulations revealed that a strong horizontal divergent flow (HDF) of unmagnetized plasma appears at the photosphere before…

Solar and Stellar Astrophysics · Physics 2015-06-22 Shin Toriumi , Keiji Hayashi , Takaaki Yokoyama

We studied the acceleration mechanisms of chromospheric jets associated with emerging flux using a two dimensional magnetohydrodynamic (MHD) simulation. We found that slow mode shock waves generated by magnetic reconnection in the…

Solar and Stellar Astrophysics · Physics 2015-06-12 Shinsuke Takasao , Hiroaki Isobe , Kazunari Shibata

Understanding how active-region properties influence coronal mass ejection (CME) dynamics is essential for constraining eruption models and improving space-weather prediction. Magnetic diagnostics derived above polarity inversion lines…

Solar and Stellar Astrophysics · Physics 2025-10-23 Harshita Gandhi , Huw Morgan