The Two Sources of Solar Energetic Particles

Reames, D. V.

doi:10.1007/s11214-013-9958-9

Cited by 441 publications

(405 citation statements)

References 203 publications

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“…The finite electric field can be a cause of this kind of accelerations. Our results well support Reames's [2013] suggestion for two different physical mechanisms for acceleration of SEPs.…”

Section: Summary and Discussionsupporting

confidence: 91%

Characteristics of four SPE groups with different origins and acceleration processes

et al. 2015

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Solar proton events (SPEs) can be categorized into four groups based on their associations with flare or CME inferred from onset timings as well as acceleration patterns using multienergy observations. In this study, we have investigated whether there are any typical characteristics of associated events and acceleration sites in each group using 42 SPEs from 1997 to 2012. We find the following: (i) if the proton acceleration starts from a lower energy, a SPE has a higher chance to be a strong event (> 5000 particle flux per unit (pfu)) even if its associated flare and/or CME are not so strong. The only difference between the SPEs associated with flare and CME is the location of the acceleration site. (ii) For the former (Group A), the sites are very low (∼ 1 Rs) and close to the western limb, while the latter (Group C) have relatively higher (mean = 6.05 Rs) and wider acceleration sites. (iii) When the proton acceleration starts from the higher energy (Group B), a SPE tends to be a relatively weak event (< 1000 pfu), although its associated CME is relatively stronger than previous groups. (iv) The SPEs categorized by the simultaneous acceleration in whole energy range within 10 min (Group D) tend to show the weakest proton flux (mean = 327 pfu) in spite of strong associated eruptions. Based on those results, we suggest that the different characteristics of SPEs are mainly due to the different conditions of magnetic connectivity and particle density, which are changed with longitude and height as well as their origin.

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“…The finite electric field can be a cause of this kind of accelerations. Our results well support Reames's [2013] suggestion for two different physical mechanisms for acceleration of SEPs.…”

Section: Summary and Discussionsupporting

confidence: 91%

Characteristics of four SPE groups with different origins and acceleration processes

et al. 2015

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“…We know from the close association of large-amplitude coronal waves with metric type II bursts (see Section 3.4.1) that shocks can be formed immediately after eruption onset in the low corona. Therefore, coronal waves could be another source of solar energetic particles (SEPs), in addition to flares and CME-driven shock waves in the outer corona and interplanetary space (for a recent review of this topic, see Reames, 2013). Coronal waves are globally propagating, hence they offer an attractive explanation for SEP events that show a wide spread of longitude.…”

Section: Acceleration Of Solar Energetic Particles (Seps)mentioning

confidence: 99%

Large-scale Globally Propagating Coronal Waves

Warmuth

2015

Living Rev. Sol. Phys.

163

140

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Large-scale, globally propagating wave-like disturbances have been observed in the solar chromosphere and by inference in the corona since the 1960s. However, detailed analysis of these phenomena has only been conducted since the late 1990s. This was prompted by the availability of high-cadence coronal imaging data from numerous spaced-based instruments, which routinely show spectacular globally propagating bright fronts. Coronal waves, as these perturbations are usually referred to, have now been observed in a wide range of spectral channels, yielding a wealth of information. Many findings have supported the "classical" interpretation of the disturbances: fast-mode MHD waves or shocks that are propagating in the solar corona. However, observations that seemed inconsistent with this picture have stimulated the development of alternative models in which "pseudo waves" are generated by magnetic reconfiguration in the framework of an expanding coronal mass ejection. This has resulted in a vigorous debate on the physical nature of these disturbances. This review focuses on demonstrating how the numerous observational findings of the last one and a half decades can be used to constrain our models of large-scale coronal waves, and how a coherent physical understanding of these disturbances is finally emerging. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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“…review by Reames, 2013); v) presumed lateral diffusion via the "birdcage model" misled the community for decades (e.g. review by Reames, 2015).…”

Section: Parameters Of Diffusive Transportmentioning

confidence: 99%

The Origin of Element Abundance Variations in Solar Energetic Particles

Reames

2016

Sol Phys

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Abundance enhancements, during acceleration and transport in both gradual and impulsive solar energetic particle (SEP) events, vary approximately as power laws in the mass-to-charge ratio [A/Q] of the ions. Since the Q-values depend upon the electron temperature of the source plasma, this has allowed a determination of this temperature from the pattern of element-abundance enhancements and a verification of the expected inverse-time dependence of the power of A/Q for diffusive transport of ions from the SEP events, with scattering mean free paths found to be between 0.2 and 1 AU. SEP events derived from plasma of different temperatures map into different regions in typical crossplots of abundances, spreading the distributions. In comparisons of SEP events with temperatures above 2 MK, impulsive events show much broader non-thermal variation of abundances than do gradual events. The extensive shock waves accelerating ions in gradual events may average over much of an active region where numerous but smaller magnetic reconnections, "nanojets", produce suprathermal seed ions, thus averaging over varying abundances, while an impulsive SEP event only samples one local region of abundance variations. Evidence for a reference He/O abundance ratio of 91, rather than 57, is also found for the hotter plasma. However, while this is similar to the solar-wind abundance of He/O, the solar-wind abundances otherwise provide an unacceptably poor reference for the SEP abundance enhancements, generating extremely large errors.

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The Two Sources of Solar Energetic Particles

Cited by 441 publications

References 203 publications

Characteristics of four SPE groups with different origins and acceleration processes

Characteristics of four SPE groups with different origins and acceleration processes

Large-scale Globally Propagating Coronal Waves

The Origin of Element Abundance Variations in Solar Energetic Particles

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