Current views on impulsive and gradual solar energetic particle events

Kallenrode, May-Britt

doi:10.1088/0954-3899/29/5/316

Cited by 128 publications

(101 citation statements)

References 142 publications

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“…Nonetheless, this ''two class'' picture has proved to be an oversimplification and does not match the diversity and wealth of the observed SEP event properties (Cane et al 2010). Furthermore, observations have indicated that there is a third category of events, the so-called hybrid or mixed events, during which both SFs and CMEdriven shocks accelerate particles that contribute to large SEP events (Kocharov & Torsti 2002;Kallenrode 2003). These hybrid or mixed events may look like gradual events but demonstrate properties of impulsive ones (Vainio et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Solar flares, coronal mass ejections and solar energetic particle event characteristics

Papaioannou

Sandberg

Anastasiadis

et al. 2016

J. Space Weather Space Clim.

128

129

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A new catalogue of 314 solar energetic particle (SEP) events extending over a large time span from 1984 to 2013 has been compiled. The properties as well as the associations of these SEP events with their parent solar sources have been thoroughly examined. The properties of the events include the proton peak integral flux and the fluence for energies above 10, 30, 60 and 100 MeV. The associated solar events were parametrized by solar flare (SF) and coronal mass ejection (CME) characteristics, as well as related radio emissions. In particular, for SFs: the soft X-ray (SXR) peak flux, the SXR fluence, the heliographic location, the rise time and the duration were exploited; for CMEs the plane-of-sky velocity as well as the angular width were utilized. For radio emissions, type III, II and IV radio bursts were identified. Furthermore, we utilized element abundances of Fe and O. We found evidence that most of the SEP events in our catalogue do not conform to a simple two-class paradigm, with the 73% of them exhibiting both type III and type II radio bursts, and that a continuum of event properties is present. Although, the so-called hybrid or mixed events are found to be present in our catalogue, it was not possible to attribute each SEP event to a mixed/hybrid sub-category. Moreover, it appears that the start of the type III burst most often precedes the maximum of the SF and thus falls within the impulsive phase of the associated SF. At the same time, type III bursts take place within %5.22 min, on average, in advance from the time of maximum of the derivative of the SXR flux (Neupert effect). We further performed a statistical analysis and a mapping of the logarithm of the proton peak flux at E > 10 MeV, on different pairs of the parent solar source characteristics. This revealed correlations in 3-D space and demonstrated that the gradual SEP events that stem from the central part of the visible solar disk constitute a significant radiation risk. The velocity of the associated CMEs, as well as the SXR peak flux and fluence, are all fairly significantly correlated to both the proton peak flux and the fluence of the SEP events in our catalogue. The strongest correlation to SEP characteristics is manifested by the CME velocity.

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Section: Introductionmentioning

confidence: 99%

Solar flares, coronal mass ejections and solar energetic particle event characteristics

Papaioannou

Sandberg

Anastasiadis

et al. 2016

J. Space Weather Space Clim.

128

129

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“…In the CME-driven shock, the proton acceleration is considered to be gradual, in which energetic particles are dominant in the initial stage, and low-energy particles arise later as the shock propagates further into the solar wind [Zank et al, 2000]. However, as various conditions and mechanisms are entangled in the proton acceleration, our physical understanding of the origin and mechanism of SPEs still remains incomplete [Kallenrode, 2003;Trottet et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

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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“…Since then, observations have indicated that there are 'hybrid' or mixed event cases, where both mechanisms appear to contribute, with one accelerating mechanism operating in the flare while the other operates at the CME-driven shock (Kallenrode 2003). Such hybrid events may result from the re-acceleration of remnant flare suprathermals by shock waves (Mason et al 1999;Desai et al 2006) or from the interaction of CMEs (Gopalswamy et al 2002).…”

Section: Fig 12mentioning

confidence: 99%

“…In fact during the September 1989 event, even an astronaut behind 10 g cm 2 of material would receive a dose of 40 mSv. The annual dose limit for a radiation worker in the United States is 20 mSv (Zeitlin et al 2013;Kerr 2013). In each solar cycle several events of this intensity occur, thus, knowledge of the spectral knee energies is essential.…”

Section: Fig 12mentioning

confidence: 99%

Solar Energetic Particles and Space Weather: Science and Applications

Malandraki

Crosby

2017

Astrophysics and Space Science Library

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This chapter provides an overview on solar energetic particles (SEPs) and their association to space weather, both from the scientific as well as from the applications perspective. A historical overview is presented on how SEPs were discovered in the 1940s and how our understanding has increased and evolved since then. Current state-of-the-art based on unique measurements obtained in the 3-dimensional heliosphere (e.g. by the Ulysses, ACE, STEREO spacecraft) and their analysis is also presented. Key open questions on SEP research expected to be answered in view of future missions that will explore the solar corona and inner heliosphere are highlighted. This is followed by an introduction to why SEPs are studied, describing the risks that SEP events pose on technology and human health. Mitigation strategies for solar radiation storms as well as examples of current SEP forecasting systems are reviewed, in context of the two novel real-time SEP forecasting tools developed within the EU H2020 HESPERIA project.

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Current views on impulsive and gradual solar energetic particle events

Cited by 128 publications

References 142 publications

Solar flares, coronal mass ejections and solar energetic particle event characteristics

Solar flares, coronal mass ejections and solar energetic particle event characteristics

Characteristics of four SPE groups with different origins and acceleration processes

Solar Energetic Particles and Space Weather: Science and Applications

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