Comparison of the Fermi and betatron acceleration efficiencies in collapsing magnetic traps

Богачев, С. А.; Сомов, Б. В.

doi:10.1134/1.2007030

Cited by 46 publications

(28 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Miller et al, 1997;Bian et al, 2014), collapsing magnetic fields (e.g. Somov and Kosugi, 1997;Karlický and Kosugi, 2004;Bogachev and Somov, 2005;Giuliani, Neukirch, and Wood, 2005) and magnetic islands (e.g. Drake et al, 2006;Oka et al, 2010;Bian and Kontar, 2013).…”

Section: Overview Of Hard X-ray Coronal Observationsmentioning

confidence: 99%

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

et al. 2017

View full text Add to dashboard Cite

We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of highenergy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modelling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for detection of these non-equilibrium phenomena in various spectral ranges.

show abstract

Section: Overview Of Hard X-ray Coronal Observationsmentioning

confidence: 99%

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

et al. 2017

View full text Add to dashboard Cite

show abstract

“…In particular, the ratio between the loop-top magnetic field strength between the end and the beginning of a collapse determines the possible energy gain (e.g., Bogachev & Somov 2005), as is obvious for the betatron acceleration, and the ratio between the footpoint and loop-top magnetic fields determines the loss cone and thereby also limits the population that gains energy through the Fermi acceleration (e.g., Eradat . In models without a guide field (e.g., Karlicky & Barta 2007;Grady & Neukirch 2009;Grady et al 2012;Borissov et al 2016), this ratio tends to be overestimated.…”

Section: Discussionmentioning

confidence: 99%

Can Substorm Particle Acceleration Be Applied to Solar Flares?

Birn

Battaglia

Fletcher

et al. 2017

ApJ

View full text Add to dashboard Cite

Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard two-ribbon flare picture in analogy to the standard magnetospheric substorm paradigm. In particular, we investigate the effects of the collapsing field ("collapsing magnetic trap") below a reconnection site, which has been demonstrated to be the major acceleration mechanism that causes energetic particle acceleration and injections observed in Earth's magnetotail associated with substorms and other impulsive events. We contrast an initially force-free, high-shear field (low beta) with low and moderate shear, finite-pressure (high-beta) arcade structures, where beta represents the ratio between gas (plasma) and magnetic pressure. We demonstrate that the energization affects large numbers of particles, but the acceleration is modest in the presence of a significant shear field. Without incorporating loss mechanisms, the effect on particles at different energies is similar, akin to adiabatic heating, and thus is not a likely mechanism to generate a power-law tail onto a (heated or not heated) Maxwellian velocity distribution.

show abstract

“…This change passes through the following stages: thermal spectrum with initial temperature T 0 → nonthermal spectrum → nonthermal spectrum with effective temperature T eff = T 0 (b m + 2)/3 (see Bogachev and Somov 2005). The effective temperature T eff characterizes the mean kinetic energy of the trapped electrons whose number, according to Eq.…”

Section: The Spectrum Of Trapped Electronsmentioning

confidence: 99%

“…Previously (Bogachev and Somov 2005), we developed a trap model in which both acceleration mechanisms were simultaneously taken into account in the collisionless approximation. The model can explain the RHESSI satellite observations that have revealed hard X-ray (HXR) sources in the solar corona whose emission is more intense than the HXR emission from the chromosphere.…”

Section: Introductionmentioning

confidence: 99%

Formation of power-law electron spectra in collapsing magnetic traps

Богачев

Сомов²

2007

Astron. Lett.

Self Cite

View full text Add to dashboard Cite

Abstract-The energy distribution of the fast electrons captured into a collapsing magnetic trap in the solar corona is calculated as a function of the trap length and diameter. It is shown that if the electrons injected into the trap have a power-law spectrum, then their spectrum remains a power-law one with the same slope throughout the acceleration process for both the Fermi and betatron acceleration mechanisms. For electrons with a thermal injection spectrum, the model predicts two types of hard X-ray sources, thermal and nonthermal. Thermal sources are formed in traps dominated by the betatron mechanism. Nonthermal sources with a power-law spectrum are formed when electrons are accelerated by the Fermi mechanism.PACS numbers : 95.10.Ce

show abstract

Comparison of the Fermi and betatron acceleration efficiencies in collapsing magnetic traps

Cited by 46 publications

References 9 publications

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Can Substorm Particle Acceleration Be Applied to Solar Flares?

Formation of power-law electron spectra in collapsing magnetic traps

Contact Info

Product

Resources

About