A semi-analytical foreshock model for energetic storm particle events inside 1 AU

Vainio, R.; Pönni, Arttu; Battarbee, Markus; Koskinen, H.; Afanasiev, Alexandr; Laitinen, Timo

doi:10.1051/swsc/2014005

Cited by 33 publications

(56 citation statements)

References 28 publications

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“…Within the estimated uncertainties, the powerlaw exponent a in 15 out of 27 SEP events lies between ∼0.75-2.75 and is comparable to the range of values obtained by Cohen et al (2005), as shown by the yellow shaded region. Also, a varies between ∼−0.33-3.9, which is roughly consistent with the typical range of ∼0.5-7 proposed recently by Schwadron et al (2015b); in this model a<1 implies a weak dependence of // l on the ionʼs Q/M ratio, while a>1 indicates that // l depends strongly on Q/M (also see Li et al 2009;Battarbee et al 2011Battarbee et al , 2013Vainio et al 2014). We note that η in 27 events lies between −1.87 and 2.33; η in 15 events lies within the range ∼0.7-1.2 reported by Cohen et al (2005).…”

Section: Properties Of Near-sun Cme Shocks and Turbulence Conditionssupporting

confidence: 88%

Spectral Properties of Large Gradual Solar Energetic Particle Events. Ii. Systematic Q/M Dependence of Heavy Ion Spectral Breaks

Desai

Mason

Dayeh

et al. 2016

ApJ

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We fit ∼0.1-500 MeV nucleon −1 H-Fe spectra in 46 large solar energetic particle (SEP) events with the double power-law Band function to obtain a normalization constant, low-and high-energy parameters γ a and γ b , and break energy E B , and derive the low-energy spectral slope γ 1 . We find that: (1) γ a , γ 1 , and γ b are species-independent and the spectra steepen with increasing energy; (2) E B decreases systematically with decreasing Q/M scaling as (Q/M) α ; (3) α varies between ∼0.2-3 and is well correlated with the ∼0.16-0.23 MeV nucleon −1 Fe/O; (4) in most events, α < 1.4, γ b -γ a > 3, and O E B increases with γ b -γ a ; and (5) in many extreme events (associated with faster coronal mass ejections (CMEs) and GLEs), Fe/O and 3 He/ 4 He ratios are enriched, α 1.4, γ b -γ a < 3, and E B decreases with γ b -γ a . The species-independence of γ a , γ 1 , and γ b and the Q/M dependence of E B within an event and the α values suggest that double power-law SEP spectra occur due to diffusive acceleration by near-Sun CME shocks rather than scattering in interplanetary turbulence. Using γ 1 , we infer that the average compression ratio for 33 near-Sun CME shocks is 2.49±0.08. In most events, the Q/M dependence of E B is consistent with the equal diffusion coefficient condition and the variability in α is driven by differences in the near-shock wave intensity spectra, which are flatter than the Kolmogorov turbulence spectrum but weaker than the spectra for extreme events. In contrast, in extreme events, enhanced wave power enables faster CME shocks to accelerate impulsive suprathermal ions more efficiently than ambient coronal ions.

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Section: Properties Of Near-sun Cme Shocks and Turbulence Conditionssupporting

confidence: 88%

Spectral Properties of Large Gradual Solar Energetic Particle Events. Ii. Systematic Q/M Dependence of Heavy Ion Spectral Breaks

Desai

Mason

Dayeh

et al. 2016

ApJ

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“…Consequently, the applied numerical acceleration models contain several parameters, some of which can only be determined in an ad-hoc manner. As an example of such an approach, Vainio et al (2014) performed Monte Carlo simulations in their state-ofthe-art semi-analytical foreshock model from about 6 to 60 solar radii. More similar studies together with data comparison are called for to gain better understanding of the ICME shock acceleration.…”

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

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356

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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“…Further development has been pointed towards a completely self-consistent dynamic modelling of particle acceleration (for the results, see e.g. Vainio & Laitinen 2007Ng & Reames 2008;Battarbee et al 2011;Vainio et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Self-consistent Monte Carlo simulations of proton acceleration in coronal shocks: Effect of anisotropic pitch-angle scattering of particles

Afanasiev

Battarbee

Vainio

2015

A&A

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Context. Solar energetic particles observed in association with coronal mass ejections (CMEs) are produced by the CME-driven shock waves. The acceleration of particles is considered to be due to diffusive shock acceleration (DSA). Aims. We aim at a better understanding of DSA in the case of quasi-parallel shocks, in which self-generated turbulence in the shock vicinity plays a key role. Methods. We have developed and applied a new Monte Carlo simulation code for acceleration of protons in parallel coronal shocks. The code performs a self-consistent calculation of resonant interactions of particles with Alfvén waves based on the quasi-linear theory. In contrast to the existing Monte Carlo codes of DSA, the new code features the full quasi-linear resonance condition of particle pitch-angle scattering. This allows us to take anisotropy of particle pitch-angle scattering into account, while the older codes implement an approximate resonance condition leading to isotropic scattering. We performed simulations with the new code and with an old code, applying the same initial and boundary conditions, and have compared the results provided by both codes with each other, and with the predictions of the steady-state theory. Results. We have found that anisotropic pitch-angle scattering leads to less efficient acceleration of particles than isotropic. However, extrapolations to particle injection rates higher than those we were able to use suggest the capability of DSA to produce relativistic particles. The particle and wave distributions in the foreshock as well as their time evolution, provided by our new simulation code, are significantly different from the previous results and from the steady-state theory. Specifically, the mean free path in the simulations with the new code is increasing with energy, in contrast to the theoretical result.

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A semi-analytical foreshock model for energetic storm particle events inside 1 AU

Cited by 33 publications

References 28 publications

Spectral Properties of Large Gradual Solar Energetic Particle Events. Ii. Systematic Q/M Dependence of Heavy Ion Spectral Breaks

Spectral Properties of Large Gradual Solar Energetic Particle Events. Ii. Systematic Q/M Dependence of Heavy Ion Spectral Breaks

Coronal mass ejections and their sheath regions in interplanetary space

Self-consistent Monte Carlo simulations of proton acceleration in coronal shocks: Effect of anisotropic pitch-angle scattering of particles

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