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We investigate two candidate solar sources or active regions (ARs) in association with a solar impulsive energetic electron (SIEE) event on 2002 October 20. The solar particle release (SPR) times of SIEEs are derived by using their velocity…

Solar and Stellar Astrophysics · Physics 2014-12-30 C. Li , L. P. Sun , X. Y. Wang , Y. Dai

A comparison between a Coronal Hole (CH) and the adjacent Quiet-Sun (QS) has been performed using spectroscopic diagnostics of Hinode/ the EUV Imaging Spectrometer (EIS). Coronal funnels play an important role in the formation and…

Solar and Stellar Astrophysics · Physics 2015-11-04 P. Kayshap , D. Banerjee , A. K. Srivastava

Extreme-ultraviolet images from the Solar Dynamics Observatory often show looplike fine structure to be present where no minority-polarity flux is visible in magnetograms, suggesting that the rate of ephemeral region (ER) emergence inside…

Solar and Stellar Astrophysics · Physics 2021-04-14 Y. -M. Wang

We have performed a three-dimensional magnetohydrodynamic simulation to study the emergence of a twisted magnetic flux tube from -20,000 km of the solar convection zone to the corona through the photosphere and the chromosphere. The middle…

Solar and Stellar Astrophysics · Physics 2015-06-03 S. Toriumi , T. Yokoyama

From radiation magnetohydrodynamic simulations of the solar atmosphere we find a new mechanism for the excitation of longitudinal slow modes within magnetic flux concentrations. We find that the convective downdrafts in the immediate…

Solar and Stellar Astrophysics · Physics 2015-05-27 Yoshiaki Kato , Oskar Steiner , Matthias Steffen , Yoshinori Suematsu

Solar activity can be witnessed in the form of sunspots and active regions, where the magnetic field is enhanced by up to a factor 1000 as compared to that of the quiet Sun. In addition, solar activity manifests itself in terms of flares,…

Solar and Stellar Astrophysics · Physics 2025-07-25 Gottfried Mann , Frédéric Schuller

The solar corona produces coronal rain, hundreds of times colder and denser material than the surroundings. Coronal rain is known to be deeply linked to coronal heating, but its origin, dynamics, and morphology are still not well…

Solar and Stellar Astrophysics · Physics 2023-07-05 Seray Şahin , Patrick Antolin , Clara Froment , Thomas A. Schad

The recent rediscovery of magnetic field switchbacks or deflections embedded in the solar wind flow by the Parker Solar Probe mission lead to a huge interest in the modelling of the formation mechanisms and origin of these switchbacks.…

Solar and Stellar Astrophysics · Physics 2021-04-28 Norbert Magyar , Dominik Utz , Robertus Erdélyi , Valery M. Nakariakov

We analyse the topology of photospheric magnetic fields and sub-photospheric flows of several active regions (ARs) that are observed during the peak to descending phase of the solar cycle 23. Our analysis shows clear evidence of hemispheric…

Solar and Stellar Astrophysics · Physics 2020-08-12 R. A. Maurya , A. Ambastha

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 study the evolution of a small-scale emerging flux region (EFR) in the quiet Sun, from its emergence to its decay. We track processes and phenomena across all atmospheric layers, explore their interrelations and compare our findings with…

Solar and Stellar Astrophysics · Physics 2020-01-15 I. Kontogiannis , G. Tsiropoula , K. Tziotziou , C. Gontikakis , C. Kuckein , M. Verma , C. Denker

Light bridges, the bright structure dividing umbrae in sunspot regions, show various activity events. In Paper I, we reported on analysis of multi-wavelength observations of a light bridge in a developing active region (AR) and concluded…

Solar and Stellar Astrophysics · Physics 2015-10-07 Shin Toriumi , Mark C. M. Cheung , Yukio Katsukawa

Flare kernels are compact features located in the solar chromosphere that are the sites of rapid heating and plasma upflow during the rise phase of flares. An example is presented from a M1.1 class flare observed on 2011 February 16 07:44…

Solar and Stellar Astrophysics · Physics 2015-06-12 Peter Young , George Doschek , Harry Warren , Hiro Hara

Quasi-periodic propagating intensity disturbances (PDs) have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS…

Solar and Stellar Astrophysics · Physics 2014-04-24 Tongjiang Wang , Leon Ofman , Joseph M. Davila

Magnetic energy is required to heat the corona, the outer atmosphere of the Sun, to millions of degrees. We study the nature of the magnetic energy source that is probably responsible for the brightening of coronal loops driven by…

Solar and Stellar Astrophysics · Physics 2018-07-25 L. P. Chitta , H. Peter , S. K. Solanki

Coronal heating through the explosive release of magnetic energy remains an open problem in solar physics. Recent hydrodynamical models attempt an investigation by placing swarms of 'nanoflares' at random sites and times in modeled…

Solar and Stellar Astrophysics · Physics 2016-11-30 K. Moraitis , A. Toutountzi , H. Isliker , M. Georgoulis , L. Vlahos , G. Chintzoglou

We study the relationship between decaying active region magnetic fields, coronal holes and the global coronal magnetic structure using Global Oscillations Network Group (GONG) synoptic magnetograms, Solar Terrestrial RElations Observatory…

Solar and Stellar Astrophysics · Physics 2015-06-16 Gordon Petrie , Karl Haislmaier

We present detailed analysis of an active region coronal jet accompanying a minifilament eruption that is fully captured and well-resolved in high spatial resolution 174A coronal images from Solar Orbiters Extreme Ultraviolet Imager (EUI).…

We investigate the morphology and temporal variability of a quiet Sun network region in different solar layers. The emission in several EUV spectral lines through both raster and slot time series, recorded by EIS/Hinode is studied along…

Solar and Stellar Astrophysics · Physics 2018-03-26 Ioannis Kontogiannis , Costis Gontikakis , Georgia Tsiropoula , Kostas Tziotziou

The "middle corona" is a critical transition between the highly disparate physical regimes of the lower and outer solar corona. Nonetheless, it remains poorly understood due to the difficulty of observing this faint region (1.5-3 solar…