Small-scale heating events in the solar atmosphere

Guerreiro, Nuno; Haberreiter, M.; Hansteen, V. H.; Schmutz, W.

doi:10.1051/0004-6361/201629795

Cited by 8 publications

(3 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since then, significant progress has been made in realistic simulations of coronal heating caused by footpoint braiding (e.g., Gudiksen & Nordlund 2002;Bingert & Peter 2011;Hansteen et al 2015;Rempel 2017). Properties of small-scale heating events caused by the current dissipation in the corona have also been explored through 3D MHD simulations (e.g., Guerreiro et al 2015Guerreiro et al , 2017. However, direct possible observational evidence of braiding is sparse (Cirtain et al 2013;Huang et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Transient small-scale brightenings in the quiet solar corona: A model for campfires observed with Solar Orbiter

Chen

Przybylski

Peter

et al. 2021

A&A

View full text Add to dashboard Cite

Context. Recent observations by the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have characterized prevalent small-scale transient brightenings in the corona above the quiet Sun termed campfires. Aims. In this study we search for comparable brightenings in a numerical model and then investigate their relation to the magnetic field and the processes that drive these events. Methods. We used the MURaM code to solve the 3D radiation magnetohydrodynamic equations in a box that stretches from the upper convection zone to the corona. The model self-consistently produces a supergranular network of the magnetic field and a hot corona above this quiet Sun. For the comparison with the model, we synthesized the coronal emission as seen by EUI in its 174 Å channel, isolated the seven strongest transient brightenings, and investigated the changes of the magnetic field in and around these in detail. Results. The transients we isolated have a lifetime of about 2 min and are elongated loop-like features with lengths around 1 Mm to 4 Mm. They tend to occur at heights of about 2 Mm to 5 Mm above the photosphere, a bit offset from magnetic concentrations that mark the bright chromospheric network, and they reach temperatures of above 1 MK. As a result, they very much resemble the larger campfires found in observations. In our model most events are energized by component reconnection between bundles of field lines that interact at coronal heights. In one case, we find that untwisting a highly twisted flux rope initiates the heating. Conclusions. Based on our study, we propose that the majority of campfire events found by EUI are driven by component reconnection and our model suggests that this process significantly contributes to the heating of the corona above the quiet Sun.

show abstract

Section: Discussionmentioning

confidence: 99%

Transient small-scale brightenings in the quiet solar corona: A model for campfires observed with Solar Orbiter

Chen

Przybylski

Peter

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…Much of the research on nanoflares has concentrated on examining how an ensemble of such events can lead to observed temperature profiles in coronal loops (Klimchuk & Cargill 2001;Ishikawa et al 2017;Tripathi et al 2010; E-mail: tomin.james@students.iiserpune.ac.in Testa et al 2014). There have also been several MHD and hybrid particle/MHD simulation studies demonstrating how continually tangling coronal magnetic fields can provide potential sites for magnetic reconnection where electrons can potentially be accelerated and account for local plasma heating (Arzner & Vlahos 2004;Sharma et al 2017;Guerreiro et al 2015Guerreiro et al , 2017Knizhnik et al 2018). Electrons accelerated in such small reconnection episodes can often escape from the corona along open field lines, emitting type III radio emission and be detected in-situ by near-earth spacecraft as impulsive electron bursts (James et al 2017).…”

Section: Small Electron Acceleration/heating Events In the Coronamentioning

confidence: 99%

Energetics of small electron acceleration episodes in the solar corona from radio noise storm observations

James

Subramanian

2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Observations of radio noise storms can act as sensitive probes of nonthermal electrons produced in small acceleration events in the solar corona. We use data from noise storm episodes observed jointly by the Giant Metrewave Radio Telescope (GMRT) and the Nancay Radioheliograph (NRH) to study characteristics of the nonthermal electrons involved in the emission. We find that the electrons carry 10 21 to 10 24 erg/s, and that the energy contained in the electrons producing a representative noise storm burst ranges from 10 20 to 10 23 ergs. These results are a direct probe of the energetics involved in ubiquitous, small-scale electron acceleration episodes in the corona, and could be relevant to a nanoflare-like scenario for coronal heating.

show abstract

“…Parker (1988) introduces the term nanoflares for such events, with energies speculated to be of the order of 10 24 ergs or less, as estimated from ultraviolet fluctuations within active regions (Porter et al 1984). This triggered many theoretical studies on the role of small-scale events in coronal heating (e.g., Walsh & Ireland 2003;Klimchuk 2006;Browning et al 2008;Tajfirouze & Safari 2012;Guerreiro et al 2015Guerreiro et al , 2017).…”

mentioning

confidence: 99%

NuSTAR Detection of X-Ray Heating Events in the Quiet Sun

Kuhar

Krucker

Glesener

et al. 2018

ApJL

View full text Add to dashboard Cite

The explanation of the coronal heating problem potentially lies in the existence of nanoflares, numerous small-scale heating events occuring across the whole solar disk. In this paper, we present the first imaging spectroscopy X-ray observations of three quiet Sun flares during the NuSTAR solar campaigns on 2016 July 26 and 2017 March 21, concurrent with SDO/AIA observations. Two of the three events showed time lags of a few minutes between peak X-ray and extreme ultraviolet (EUV) emissions. Isothermal fits with rather low temperatures in the range 3.2 − 4.1 MK and emission measures of (0.6 − 15) × 10 44 cm −3 describe their spectra well, resulting in thermal energies in the range (2 − 6) × 10 26 ergs. NuSTAR spectra did not show any signs of a nonthermal or higher temperature component. However, since the estimated upper limits of (hidden) nonthermal energy are comparable to the thermal energy estimates, the lack of a nonthermal component in the observed spectra is not a constraining result. The estimated GOES classes from the fitted values of temperature and emission measure fall between 1/1000 and 1/100 A class level, making them 8 orders of magnitude fainter in soft X-ray flux than the largest solar flares.

show abstract

Small-scale heating events in the solar atmosphere

Cited by 8 publications

References 55 publications

Transient small-scale brightenings in the quiet solar corona: A model for campfires observed with Solar Orbiter

Transient small-scale brightenings in the quiet solar corona: A model for campfires observed with Solar Orbiter

Energetics of small electron acceleration episodes in the solar corona from radio noise storm observations

NuSTAR Detection of X-Ray Heating Events in the Quiet Sun

Contact Info

Product

Resources

About