A theoretical perspective on particle acceleration by interplanetary shocks and the Solar Energetic Particle problem

Verkhoglyadova, O. P.; Zank, G. P.; Li, Gang

doi:10.1016/j.physrep.2014.10.004

Cited by 32 publications

(17 citation statements)

References 142 publications

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“…21 the energetic particle spectra rise soon after the CME release on the 5th December until the shock arrival on the 8th, indicated by the "shock peak" in the electron and lowest-energy proton fluxes. For a thorough review of the recent developments in shock acceleration theory, see Verkhoglyadova et al (2015) and references therein.…”

Section: Particle Acceleration At Icme Shocksmentioning

confidence: 99%

See 1 more Smart Citation

Coronal mass ejections and their sheath regions in interplanetary space

Kilpua

Koskinen

Pulkkinen

2017

Living Rev Sol Phys

371

360

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Interplanetary coronal mass ejections (ICMEs) are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs.

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Section: Particle Acceleration At Icme Shocksmentioning

confidence: 99%

“…The DSA scenario may look simple but practical self-consistent calculations are far from straightforward (e.g., Verkhoglyadova et al 2015, and references therein). The ambient plasma parameters and the formation of the suprathermal seed population to be accelerated can be very different from case to case.…”

Section: Particle Acceleration At Icme Shocksmentioning

confidence: 99%

Coronal mass ejections and their sheath regions in interplanetary space

Kilpua

Koskinen

Pulkkinen

2017

Living Rev Sol Phys

371

360

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“…According to DSA theory, the rate of electron acceleration and, hence, the maximum energy attained, is dependent on the shock-to-field geometry, as well as the shock strength (Jokipii 1987). The electron acceleration efficiency would be considerably lower in the quasi-parallel configuration due to the long times required to energize particles (they spend most of their time random walking in the upstream or downstream regions; Guo & Giacalone 2010;Verkhoglyadova et al 2015). Given that the shock nose becomes quasiparallel, the electron acceleration efficiency may have reduced at this point and may be an explanation of the cessation of the radio emission despite an increasing M A .…”

Section: Why Does the Type II Emission Stop?mentioning

confidence: 99%

Evolution of the Alfvén Mach number associated with a coronal mass ejection shock

Maguire

Carley

McCauley

et al. 2020

A&A

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The Sun regularly produces large-scale eruptive events, such as coronal mass ejections (CMEs) that can drive shock waves through the solar corona. Such shocks can result in electron acceleration and subsequent radio emission in the form of a type II radio burst. However, the early-phase evolution of shock properties and its relationship to type II burst evolution is still subject to investigation. Here we study the evolution of a CME-driven shock by comparing three commonly used methods of calculating the Alfvén Mach number (M A ), namely: shock geometry, a comparison of CME speed to a model of the coronal Alfvén speed, and the type II bandsplitting method. We applied the three methods to the 2017 September 2 event, focusing on the shock wave observed in extreme ultraviolet (EUV) by the Solar Ultraviolet Imager (SUVI) on board GOES-16, in white-light by the Large Angle and Spectrometric Coronagraph (LASCO) on board SOHO, and the type II radio burst observed by the Irish Low Frequency Array (I-LOFAR). We show that the three different methods of estimating shock M A yield consistent results and provide a means of relating shock property evolution to the type II emission duration. The type II radio emission emerged from near the nose of the CME when M A was in the range 1.4-2.4 at a heliocentric distance of ∼1.6 R . The emission ceased when the CME nose reached ∼2.4 R , despite an increasing Alfvén Mach number (up to 4). We suggest the radio emission cessation is due to the lack of quasi-perpendicular geometry at this altitude, which inhibits efficient electron acceleration and subsequent radio emission.

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“…Thus, enhanced scattering of SEPs by Alfvén waves is induced that enhances the efficiency of diffusive shock acceleration (DSA) of SEPs in a self-regulatory fashion at the nearly parallel shock [6,9,10]. For an excellent recent review of the current status of SEP modelling at traveling shocks, see Verkhoglyadova et al [11]. Our calculations discussed below show that, because of the highly non-uniform coronal conditions that the shock encounters, both the DSA of SEPs and self-excitation of Alfvén waves by SEPs are highly time-dependent coronal processes.…”

Section: Introductionmentioning

confidence: 99%

Acceleration of Solar Energetic Particles at a Fast Traveling Shock in Non-uniform Coronal Conditions

Roux

Arthur

2017

J. Phys.: Conf. Ser.

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Abstract. Time-dependent solar energetic particle (SEP) acceleration is investigated at a fast, nearly parallel spherical traveling shock in the strongly non-uniform corona by solving the standard focused transport equation for SEPs and transport equations for parallel propagating Alfvén waves that form a set of coupled equations. This enables the modeling of self-excitation of Alfvén waves in the inertial range by SEPs ahead of the shock and its role in enhancing the efficiency of the diffusive shock acceleration (DSA) of SEPs in a self-regulatory fashion. Preliminary results suggest that, because of the highly non-uniform coronal conditions that the shock encounters, both DSA and wave excitation are highly time-dependent processes. Thus, DSA spectra of SEPs strongly deviate from the simple power-law prediction of standard steady-state DSA theory and initially strong wave excitation weakens rapidly. Consequently, the ability of DSA to produce high energy SEPs in the corona of ~1 GeV, as observed in the strongest gradual SEP events, appears to be strongly curtailed at a fast nearly parallel shock, but further research is needed before final conclusions can be drawn. IntroductionWe report preliminary simulation results of time-dependent solar energetic particle (SEP) acceleration at a fast, nearly parallel spherical traveling shock in the corona by taking into account the strong radial dependence in background coronal plasma conditions that the shock encounters during the first hour of shock propagation. For this purpose a simple empirical coronal plasma model [1] is used as a first step. The model involves solving a set of coupled equations for SEPs and parallel propagating Alfvén waves. The standard focused transport equation is solved to simulate SEP acceleration at the traveling shock when SEPs are scattered by Alfvén waves in its vicinity [2,3], and standard transport equations for parallel propagating Alfvén waves are solved to model wave transport near the shock including self-excitation of waves in the inertial range by upstream SEPs undergoing shock acceleration [4,5,6,7,8]. Thus, enhanced scattering of SEPs by Alfvén waves is induced that enhances the efficiency of diffusive shock acceleration (DSA) of SEPs in a self-regulatory fashion at the nearly parallel shock [6,9,10]. For an excellent recent review of the current status of SEP modelling at traveling shocks, see Verkhoglyadova et al. [11]. Our calculations discussed below show that, because of the highly non-uniform coronal conditions that the shock encounters, both the DSA of SEPs and self-excitation of Alfvén waves by SEPs are highly time-dependent coronal processes. Thus, we find that the accelerated spectra of SEPs deviate strongly from the simple power-law prediction of standard

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A theoretical perspective on particle acceleration by interplanetary shocks and the Solar Energetic Particle problem

Cited by 32 publications

References 142 publications

Coronal mass ejections and their sheath regions in interplanetary space

Coronal mass ejections and their sheath regions in interplanetary space

Evolution of the Alfvén Mach number associated with a coronal mass ejection shock

Acceleration of Solar Energetic Particles at a Fast Traveling Shock in Non-uniform Coronal Conditions

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