Large gradual solar energetic particle events

Desai, M. I.; Giacalone, J.

doi:10.1007/s41116-016-0002-5

Cited by 406 publications

(348 citation statements)

References 416 publications

(632 reference statements)

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“…According to the diffusive shock acceleration theory, the slope of the SEP intensity spectrum depends only on the density compression ratio (e.g., Eq. (11) in Desai and Giacalone, 2016). Therefore, measurements of the compression ratio and its temporal evolution in the corona can go a long way in understanding SEP in situ observations in the inner heliosphere.…”

Section: Introductionmentioning

confidence: 99%

The density compression ratio of shock fronts associated with coronal mass ejections

Kwon

Vourlidas

2018

J. Space Weather Space Clim.

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-We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (∼2000 km s À1 ) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the threedimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a x 2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.

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Section: Introductionmentioning

confidence: 99%

The density compression ratio of shock fronts associated with coronal mass ejections

Kwon

Vourlidas

2018

J. Space Weather Space Clim.

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“…Solar energetic particles (SEPs) are accelerated near the Sun during explosive solar activities such as flares and coronal mass ejections (CMEs) (Reames 1999;Desai & Giacalone 2016). Large SEP events are of particular importance because they pose severe radiation hazards to astronauts and equipment in space.…”

Section: Introductionmentioning

confidence: 99%

“…In large SEP events, high-energy particles are believed to be accelerated by CME-driven shock waves (Reames 1999;Desai & Giacalone 2016). There have been a number of factors regarding CME shock properties that have been found to be important for producing large SEP events.…”

Section: Introductionmentioning

confidence: 99%

The Acceleration of High-energy Protons at Coronal Shocks: The Effect of Large-scale Streamer-like Magnetic Field Structures

Kong

Guo

Giacalone

et al. 2017

ApJ

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Recent observations have shown that coronal shocks driven by coronal mass ejections can develop and accelerate particles within several solar radii in large solar energetic particle (SEP) events. Motivated by this, we present an SEP acceleration study that including the process in which a fast shock propagates through a streamer-like magnetic field with both closed and open field lines in the low corona region. The acceleration of protons is modeled by numerically solving the Parker transport equation with spatial diffusion both along and across the magnetic field. We show that particles can be sufficiently accelerated to up to several hundred MeV within 2-3 solar radii. When the shock propagates through a streamer-like magnetic field, particles are more efficiently accelerated compared to the case with a simple radial magnetic field, mainly due to perpendicular shock geometry and the natural trapping effect of closed magnetic fields. Our results suggest that the coronal magnetic field configuration is an important factor for producing large SEP events. We further show that the coronal magnetic field configuration strongly influences the distribution of energetic particles, leading to different locations of source regions along the shock front where most high-energy particles are concentrated. This work may have strong implications for SEP observations. The upcoming Parker Solar Probe will provide in situ observations for the distribution of energetic particles in the coronal shock region, and test the results of the study.

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“…SEP transport processes are described in detail in Chap. 4 of this volume (see also Desai and Giacalone (2016) which includes a review on this topic).…”

Section: Particle Accelerationmentioning

confidence: 99%

“…Early observation of a solar energetic particle event (Reproduced from Meyer et al 1956, permission for reuse from publisher American Physical Society for both print and electronic publication) impulsive SEP events, particle populations accelerated by near-Sun CME-shocks are termed as gradual SEP events, and those associated with CME shocks observed near Earth are known as energetic storm particle (ESP) events (Desai and Giacalone 2016). The first SEP event observations extending up to GeV energies were made with ground-based ionization chambers and neutron monitors in the mid 1940s (Forbush 1946).…”

mentioning

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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Large gradual solar energetic particle events

Cited by 406 publications

References 416 publications

The density compression ratio of shock fronts associated with coronal mass ejections

The density compression ratio of shock fronts associated with coronal mass ejections

The Acceleration of High-energy Protons at Coronal Shocks: The Effect of Large-scale Streamer-like Magnetic Field Structures

Solar Energetic Particles and Space Weather: Science and Applications

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