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A recent analysis has suggested that the heating of plasma loops in the solar corona depends not just on the Poynting flux but also on processes yet to be identified. This discovery reflects and refines earlier questions such as, why and…

Solar and Stellar Astrophysics · Physics 2024-08-16 P. G. Judge , N. P. M. Kuin

I propose a new paradigm for solar coronal heating viewed as a self-regulating process keeping the plasma marginally collisionless. The mechanism is based on the coupling between two effects. First, coronal density controls the plasma…

Astrophysics · Physics 2008-11-26 Dmitri A. Uzdensky

The properties expected of "hot" non-flaring plasmas due to nanoflare heating in active regions are investigated using hydrodynamic modeling tools, including a two-fluid development of the EBTEL code. Here we study a single nanoflare and…

Solar and Stellar Astrophysics · Physics 2016-09-28 W. T. Barnes , P. J. Cargill , S. J. Bradshaw

There are still debates whether particle acceleration in solar flares may occur due to interruption of electric currents flowing along magnetic loops. To contribute to this problem, we performed the first statistical study of relationships…

Solar and Stellar Astrophysics · Physics 2020-03-25 I. V. Zimovets , I. N. Sharykin , W. Q. Gan

The nature and detailed properties of the heating of the million-degree solar corona are important issues that are still largely unresolved. Nanoflare heating might be dominant in active regions and quiet Sun, although direct signatures of…

Solar flare electron acceleration is an efficient process, but its properties (mechanism, location) are not well constrained. Via hard X-ray (HXR) emission, we routinely observe energetic electrons at the Sun, and sometimes we detect…

Solar and Stellar Astrophysics · Physics 2023-10-09 Ross Pallister , Natasha L. S. Jeffrey

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a…

Solar and Stellar Astrophysics · Physics 2023-04-18 Eduard P. Kontar , A. Gordon Emslie , Galina G. Motorina , Brian R. Dennis

The standard flare model, despite its success, is limited in comprehensively explaining the various processes involving nonthermal particles. One such missing ingredient is a detailed understanding of the various processes involved during…

Solar and Stellar Astrophysics · Physics 2024-04-23 Surajit Mondal , Andrea F. Battaglia , Bin Chen , Sijie Yu

In the solar corona, magnetic reconnection occurs due to the finite resistivity of the plasma. At the same time, resistivity leads to ohmic heating. Therefore, the reconnecting current sheet should heat the surrounding plasma. This paper…

Solar and Stellar Astrophysics · Physics 2023-06-06 Anton Reva , Sergey Bogachev , Ivan Loboda , Artem Ulyanov , Alexey Kirichenko

Soft X-ray solar bursts are studied. Weak bursts with powers up to 10-8 W/m2 were detected. All the events were confirmed by GOES observations. Parameters of these microflares are determined. A physical mechanism for the low-intensity solar…

Solar and Stellar Astrophysics · Physics 2015-09-18 I. K. Mirzoeva

X-ray observations are a direct diagnostic of fast electrons produced in solar flares, energized during the energy release process and directed towards the Sun. Since the properties of accelerated electrons can be substantially changed…

Solar and Stellar Astrophysics · Physics 2015-10-28 Natasha Jeffrey , Eduard Kontar , Gordon Emslie , Nicolas Bian

The sharp magnetic discontinuities which naturally appear in solar magnetic flux tubes driven by turbulent photospheric motions are associated with intense currents. \citet{Par83} proposed that these currents can become unstable to a…

Astrophysics · Physics 2009-11-10 Kaspar Arzner , Loukas Vlahos

We study event-to-event variations in the abundance enhancements of the elements He through Pb for Fe-rich impulsive solar energetic-particle (SEP) events, and their relationship with properties of associated coronal mass ejections (CMEs)…

Solar and Stellar Astrophysics · Physics 2015-01-06 Donald V. Reames , Edward W. Cliver , Stephen W. Kahler

Most theoretical investigations of particle acceleration during solar flares cannot be applied to observations for detailed study of the time evolution. We propose a phenomenological model for turbulence evolution and stochastic particle…

Solar and Stellar Astrophysics · Physics 2009-08-10 Siming Liu , Lyndsay Fletcher

An analytical cancellation nanoflare model has recently been established to show the fundamental role that ubiquitous small-scale cancellation nanoflares play in solar atmospheric heating. Although this model is well-supported by…

Solar and Stellar Astrophysics · Physics 2025-04-24 Zehao Tang , Yuandeng Shen , Chengrui Zhou , Surui Yao , Dongxu Liu

Context. We present an analysis of a GOES M1.8 flare with excellent observational coverage in UV, EUV, and X-ray, including observations from the instruments IRIS, SDO with AIA, Hinode/EIS, Hinode/XRT, and Solar Orbiter with the…

The solar coronal heating problem is an open question since 1939. One proposed model for the transport and release of mechanical energy generated in the sub-phorospheric layers and photosphere is the nanoflare model that incorporates Ohmic…

Solar and Stellar Astrophysics · Physics 2017-07-12 Charalambos Kanella , Boris V. Gudiksen

Aims The possible influence of solar superflares on the near-Earth space radiation environment are assessed through the investigation of scaling laws between the peak proton flux and fluence of Solar Energetic Particle (SEP) events with the…

Solar and Stellar Astrophysics · Physics 2023-03-08 Athanasios Papaioannou , Konstantin Herbst , Tobias Ramm , Edward W. Cliver , David Lario , Astrid M. Veronig

Solar flares are one of the most energetic events in the solar system, their impact on Earth at ground level and its atmosphere remains under study. The repercussions of this phenomenon in our technological infrastructure includes radio…

Solar and Stellar Astrophysics · Physics 2018-08-29 V. De la Luz , E. P. Balanzario , T. Tsiftsi

We present new RHESSI upper limits in the 3-200 keV energy range for solar hard X-ray emission in the absence of flares and active regions, i.e. the quiet Sun, using data obtained between July 2005 and April 2009. These new limits,…

Solar and Stellar Astrophysics · Physics 2015-05-19 I. G. Hannah , H. S. Hudson , G. J. Hurford , R. P. Lin