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Donald V. Reames - One of the best experts on this subject based on the ideXlab platform.
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Solar Energetic Particles - Solar Energetic Particles
Lecture Notes in Physics, 2020Co-Authors: Donald V. ReamesAbstract:This concise primer introduces the non-specialist reader to the physics of Solar Energetic Particles (SEP) and systematically reviews the evidence for the two main mechanisms which lead to the so-called impulsive and gradual SEP events. More specifically, the timing of the onsets, the longitude distributions, the high-energy spectral shapes, the correlations with other Solar phenomena (e.g. coronal mass ejections), as well as the all-important elemental and isotopic abundances of SEPs are investigated. Impulsive SEP events are related to magnetic reconnection in Solar flares and jets. The concept of shock acceleration by scattering on self-amplified Alfvén waves is introduced, as is the evidence of reacceleration of impulsive-SEP material in the seed population accessed by the shocks in gradual events. The text then develops processes of transport of ions out to an observer. Finally, a new technique to determine the source plasma temperature in both impulsive and gradual events is demonstrated. Last but not least the role of SEP events as a radiation hazard in space is mentioned and a short discussion of the nature of the main particle telescope designs that have contributed to most of the SEP measurements is given
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virtues of including hydrogen in the patterns of element abundances in Solar Energetic Particles
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: Donald V. ReamesAbstract:We revisit a multi-spacecraft study of the element abundances of Solar Energetic Particles (SEPs) in the 23 January 2012 event, where the power-law pattern of enhancements versus the mass-to-charge ratio A/Q for the elements C through Fe was partly disrupted by a break near Mg, which turned out to be an unfortunate distraction. In the current article we find that extending that least-squares fits for C - Fe down to H at A/Q = 1 lends much more credence to the power laws, even though H itself was not included in the fits. We also investigate the extent of an adiabatically invariant "reservoir" of magnetically-trapped Particles behind the shock wave in this event.
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Four Distinct Pathways to the Element Abundances in Solar Energetic Particles
Space Science Reviews, 2020Co-Authors: Donald V. ReamesAbstract:Based upon recent evidence from abundance patterns of chemical elements in Solar Energetic Particles (SEPs), and, ironically, the belated inclusion of H and He, we can distinguish four basic SEP populations: (1) SEP1—pure “impulsive” SEPs are produced by magnetic reconnection in Solar jets showing steep power-law enhancements of 1 ≤ Z ≤ 56 $1\leq Z \leq 56$ ions versus charge-to-mass ratio A / Q $A/Q$ from a ≈ 3 $\approx 3$ MK plasma. (2) SEP2—ambient ions, mostly protons, plus SEP1 ions reaccelerated by the shock wave driven by the narrow coronal mass ejection (CME) from the same jet. (3) SEP3—a “gradual” SEP event is produced when a moderately fast, wide CME-driven shock wave barely accelerates ambient protons while preferentially accelerating accumulated remnant SEP1 ions from an active region fed by multiple jets. (4) SEP4—a gradual SEP event is produced when a very fast, wide CME-driven shock wave is completely dominated by ambient coronal seed population of 0.8–1.8 MK plasma usually producing a full power law vs. A / Q $A/Q$ for 1 ≤ Z ≤ 56 $1\leq Z \leq 56$ ions. We begin with element abundances in the photosphere that are fractionated during transport up to the corona based upon their first ionization potential (FIP); this important “FIP effect” for SEPs provides our reference abundances and is different for SEPs from that for the Solar wind. We then show evidence for each of the processes of acceleration, reacceleration, and transport that conspire to produce the four abundances patterns we distinguish.
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Abundances, Ionization States, Temperatures, and FIP in Solar Energetic Particles
Space Science Reviews, 2018Co-Authors: Donald V. ReamesAbstract:The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of Energetic Particles. The early surprise in Solar Energetic Particles (SEPs) was 1000-fold enhancements in He 3 / 4 He ${}^{3}\mbox{He}/{}^{4}\mbox{He}$ from resonant wave-particle interactions in the small “impulsive” SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio A / Q $A/Q$ , rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in Solar jets. In contrast, in the largest SEP events, the “gradual” events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of Solar coronal abundances, but A / Q $A/Q$ -dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states Q $Q$ show coronal temperatures of 1–2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of Q $Q$ are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of A / Q $A/Q$ , we can use abundances to deduce the probable Q $Q$ -values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs and from the slow Solar wind as a function of the first ionization potential (FIP) of the elements, remaining differences are for the elements C, P, and S. The theory of the fractionation of ions by Alfvén waves shows that C, P, and S are suppressed because of wave resonances during chromospheric transport on closed magnetic loops but not on open magnetic fields that supply the Solar wind. Shock waves can accelerate ions from closed coronal loops that easily escape as SEPs, while the Solar wind must emerge on open fields.
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abundances ionization states temperatures and fip in Solar Energetic Particles
Space Science Reviews, 2018Co-Authors: Donald V. ReamesAbstract:The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of Energetic Particles. The early surprise in Solar Energetic Particles (SEPs) was 1000-fold enhancements in \({}^{3}\mbox{He}/{}^{4}\mbox{He}\) from resonant wave-particle interactions in the small “impulsive” SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio \(A/Q\), rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in Solar jets. In contrast, in the largest SEP events, the “gradual” events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of Solar coronal abundances, but \(A/Q\)-dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states \(Q\) show coronal temperatures of 1–2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of \(Q\) are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of \(A/Q\), we can use abundances to deduce the probable \(Q\)-values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs and from the slow Solar wind as a function of the first ionization potential (FIP) of the elements, remaining differences are for the elements C, P, and S. The theory of the fractionation of ions by Alfven waves shows that C, P, and S are suppressed because of wave resonances during chromospheric transport on closed magnetic loops but not on open magnetic fields that supply the Solar wind. Shock waves can accelerate ions from closed coronal loops that easily escape as SEPs, while the Solar wind must emerge on open fields.
Radoslav Bucik - One of the best experts on this subject based on the ideXlab platform.
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3 he rich Solar Energetic Particles Solar sources
Space Science Reviews, 2020Co-Authors: Radoslav BucikAbstract:3He-rich Solar Energetic Particles (SEPs), showing up to a 10,000-fold abundance enhancement of rare elements like 3He or ultra-heavy nuclei, have been a puzzle for more than 50 years. One reason for the current lack of understanding of 3He-rich SEPs is the difficulty resolving the source regions of these commonly occurring events. Since their discovery, there has been strong evidence that 3He-rich SEP production is associated with flares on the Sun. Anomalous abundances of 3He-rich SEPs have been attributed to a unique acceleration mechanism that must routinely operate at flare sites. Flares associated with 3He-rich SEPs have been often observed in jet-like forms indicating an acceleration in magnetic reconnection involving field lines open to interplanetary space. Owing to a fleet of spacecraft around the Sun, providing a greatly improved resolution of Solar imaging observations, 3He-rich SEP sources are now explored in unprecedented detail. This paper outlines the current understanding of 3He-rich SEPs, mainly focusing on their Solar sources.
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energy spectra of 3he rich Solar Energetic Particles associated with coronal waves
arXiv: Solar and Stellar Astrophysics, 2016Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, M. E. WiedenbeckAbstract:In addition to their anomalous abundances, 3He-rich Solar Energetic Particles (SEPs) show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. Solar sources of these Particles have been often associated with jets and narrow CMEs, which are the signatures of magnetic reconnection involving open field. Recent reports on new associations with large-scale EUV waves bring new insights on acceleration and transport of 3He-rich SEPs in the corona. We examined energy spectra for 32 3He-rich SEP events observed by ACE at L1 near Solar minimum in 2007-2010 and compared the spectral shapes with Solar flare signatures obtained from STEREO EUV images. We found the events with jets or brightenings tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.
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multi spacecraft observations of recurrent 3he rich Solar Energetic Particles
The Astrophysical Journal, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, U Mall, A Korth, R GomezherreroAbstract:We study the origin of {sup 3}He-rich Solar Energetic Particles (<1 MeV nucleon{sup –1}) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The {sup 3}He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE {sup 3}He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 {sup 3}He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west Solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous {sup 3}He enrichment, lacking Solar Energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) Solar regions with long-lasting conditions for {sup 3}He acceleration and (2) Solar Energetic {sup 3}He that is temporarily confined/re-accelerated inmore » interplanetary space.« less
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multi spacecraft observations of recurrent 3he rich Solar Energetic Particles
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, U Mall, A Korth, R GomezherreroAbstract:We study the origin of 3He-rich Solar Energetic Particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west Solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking Solar Energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) Solar regions with long-lasting conditions for 3He acceleration and 2) Solar Energetic 3He that is temporary confined/re-accelerated in interplanetary space.
G. M. Mason - One of the best experts on this subject based on the ideXlab platform.
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energy spectra of 3he rich Solar Energetic Particles associated with coronal waves
arXiv: Solar and Stellar Astrophysics, 2016Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, M. E. WiedenbeckAbstract:In addition to their anomalous abundances, 3He-rich Solar Energetic Particles (SEPs) show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. Solar sources of these Particles have been often associated with jets and narrow CMEs, which are the signatures of magnetic reconnection involving open field. Recent reports on new associations with large-scale EUV waves bring new insights on acceleration and transport of 3He-rich SEPs in the corona. We examined energy spectra for 32 3He-rich SEP events observed by ACE at L1 near Solar minimum in 2007-2010 and compared the spectral shapes with Solar flare signatures obtained from STEREO EUV images. We found the events with jets or brightenings tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.
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multi spacecraft observations of recurrent 3he rich Solar Energetic Particles
The Astrophysical Journal, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, U Mall, A Korth, R GomezherreroAbstract:We study the origin of {sup 3}He-rich Solar Energetic Particles (<1 MeV nucleon{sup –1}) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The {sup 3}He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE {sup 3}He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 {sup 3}He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west Solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous {sup 3}He enrichment, lacking Solar Energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) Solar regions with long-lasting conditions for {sup 3}He acceleration and (2) Solar Energetic {sup 3}He that is temporarily confined/re-accelerated inmore » interplanetary space.« less
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multi spacecraft observations of recurrent 3he rich Solar Energetic Particles
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, U Mall, A Korth, R GomezherreroAbstract:We study the origin of 3He-rich Solar Energetic Particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west Solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking Solar Energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) Solar regions with long-lasting conditions for 3He acceleration and 2) Solar Energetic 3He that is temporary confined/re-accelerated in interplanetary space.
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relative distributions of fluences of 3he and 4he in Solar Energetic Particles
The Astrophysical Journal, 2009Co-Authors: Vahe Petrosian, Yan Wei Jiang, G C Ho, G. M. MasonAbstract:Solar Energetic Particles show a rich variety of spectra and relative abundances of many ionic species and their isotopes. A long-standing puzzle has been the extreme enrichments of 3He ions. The most extreme enrichments are observed in low-fluence, the so-called impulsive, events which are believed to be produced at the flare site in the Solar corona with little scattering and acceleration during transport to the Earth. In such events, 3He ions show a characteristic concave curved spectra in a log-log plot. In two earlier papers of Liu et al., we showed how such extreme enrichments and spectra can result in the model developed by Petrosian and Liu, where ions are accelerated stochastically by plasma waves or turbulence. In this paper, we address the relative distributions of the fluences of 3He and 4He ions presented by Ho et al., which show that while the distribution of 4He fluence (which we believe is a good measure of the flare strength) like many other extensive characteristics of Solar flare is fairly broad, the 3He fluence is limited to a narrow range. These characteristics introduce a strong anticorrelation between the ratio of the fluences and the 4He fluence. One of the predictions of our model presented in the 2006 paper was the presence of steep variation of the fluence ratio with the level of turbulence or the rate of acceleration. We show here that this feature of the model can reproduce the observed distribution of the fluences with very few free parameters. The primary reason for the success of the model in both fronts is because fully ionized 3He ion, with its unique charge-to-mass ratio, can resonantly interact with plasma modes not accessible to 4He and be accelerated more readily than 4He. Essentially in most flares, all background 3He ions are accelerated to few MeV/nucleon range, while this happens for 4He ions only in very strong events. A much smaller fraction of 4He ions reach such energies in weaker events.
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Solar elemental composition based on studies of Solar Energetic Particles
Space Science Reviews, 2007Co-Authors: C. M. S. Cohen, R. A. Mewaldt, R. A. Leske, A. C. Cummings, E. C. Stone, T. T. Von Rosenvinge, M. E. Wiedenbeck, G. M. MasonAbstract:Solar abundances can be derived from the composition of the Solar wind and Solar Energetic Particles (SEPs) as well as obtained through spectroscopic means. Past comparisons have suggested that all three samples agree well, when rigidity-related fractionation effects on the SEPs were accounted for. It has been known that such effects vary from one event to the next and should be addressed on an event-by-event basis. This paper examines event variability more closely, particularly in terms of energy-dependent SEP abundances. This is now possible using detailed SEP measurements spanning several decades in energy from the Ultra Low Energy Isotope Spectrometer (ULEIS) and the Solar Isotope Spectrometer (SIS) on the ACE spacecraft. We present examples of the variability of the elemental composition with energy and suggest they can be understood in terms of diffusion from the acceleration region near the interplanetary shock. By means of a spectral scaling procedure, we obtain energy-independent abundance ratios for 14 large SEP events and compare them to reported Solar wind and coronal abundances as well as to previous surveys of SEP events.
S Dalla - One of the best experts on this subject based on the ideXlab platform.
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from sun to interplanetary space what is the pathlength of Solar Energetic Particles
The Astrophysical Journal, 2019Co-Authors: T Laitinen, S DallaAbstract:Solar Energetic Particles (SEPs), accelerated during Solar eruptions, propagate in turbulent Solar wind before being observed with in situ instruments. In order to interpret their origin through comparison with remote sensing observations of the Solar eruption, we thus must deconvolve the transport effects due to the turbulent magnetic fields from the SEP observations. Recent research suggests that the SEP propagation is guided by the turbulent meandering of the magnetic fieldlines across the mean magnetic field. However, the lengthening of the distance the SEPs travel, due to the fieldline meandering, has so far not been included in SEP event analysis. This omission can cause significant errors in estimation of the release times of SEPs at the Sun. We investigate the distance traveled by the SEPs by considering them to propagate along fieldlines that meander around closed magnetic islands that are inherent in turbulent plasma. We introduce a fieldline random walk model which takes into account the physical scales associated to the magnetic islands. Our method remedies the problem of the diffusion equation resulting in unrealistically short pathlengths, and the fractal dependence of the pathlength of random walk on the length of the random-walk step. We find that the pathlength from the Sun to 1au can be below the nominal Parker spiral length for SEP events taking place at Solar longitudes 45E to 60W, whereas the western and behind-the-limb Particles can experience pathlengths longer than 2au due to fieldline meandering.
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comparing long duration gamma ray flares and high energy Solar Energetic Particles
arXiv: Space Physics, 2019Co-Authors: G A De Nolfo, James M. Ryan, E. R. Christian, S Dalla, J Giacalone, A Bruno, I G Richardson, S J Stochaj, G A BazilevskayaAbstract:Little is known about the origin of the high-energy and sustained emission from Solar Long-Duration Gamma-Ray Flares (LDGRFs), identified with the Compton Gamma Ray Observatory (CGRO), the Solar Maximum Mission (SMM), and now Fermi. Though Fermi/Large Area Space Telescope (LAT) has identified dozens of flares with LDGRF signature, the nature of this phenomenon has been a challenge to explain both due to the extreme energies and long durations. The highest-energy emission has generally been attributed to pion production from the interaction of >300 MeV protons with the ambient matter. The extended duration suggests that particle acceleration occurs over large volumes extending high in the corona, either from stochastic acceleration within large coronal loops or from back precipitation from coronal mass ejection driven shocks. It is possible to test these models by making direct comparison between the properties of the accelerated ion population producing the gamma-ray emission derived from the Fermi/LAT observations, and the characteristics of Solar Energetic Particles (SEPs) measured by the Payload for Matter-Antimatter Exploration and Light Nuclei Astrophysics (PAMELA) spacecraft in the energy range corresponding to the pion-related emission detected with Fermi. For fourteen of these events we compare the two populations -- SEPs in space and the interacting Particles at the Sun -- and discuss the implications in terms of potential sources. Our analysis shows that the two proton numbers are poorly correlated, with their ratio spanning more than five orders of magnitude, suggesting that the back precipitation of shock-acceleration Particles is unlikely the source of the LDGRF emission.
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acceleration and propagation of Solar Energetic Particles
Space Science Reviews, 2017Co-Authors: K L Klein, S DallaAbstract:Solar Energetic Particles (SEPs) are an important component of Space Weather, including radiation hazard to humans and electronic equipment, and the ionisation of the Earth’s atmosphere. We review the key observations of SEPs, our current understanding of their acceleration and transport, and discuss how this knowledge is incorporated within Space Weather forecasting tools. Mechanisms for acceleration during Solar flares and at shocks driven by Coronal Mass Ejections (CMEs) are discussed, as well as the timing relationships between signatures of Solar eruptive events and the detection of SEPs in interplanetary space. Evidence on how the parameters of SEP events are related to those of the parent Solar activity is reviewed and transport effects influencing SEP propagation to near-Earth locations are examined. Finally, the approaches to forecasting Space Weather SEP effects are discussed. We conclude that both flare and CME shock acceleration contribute to Space Weather relevant SEP populations and need to be considered within forecasting tools.
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drift induced deceleration of Solar Energetic Particles
The Astrophysical Journal, 2015Co-Authors: S Dalla, Michael Marsh, T LaitinenAbstract:We investigate the deceleration of Solar Energetic Particles (SEPs) during their propagation from the Sun through interplanetary space, in the presence of weak to strong scattering in a Parker spiral configuration, using relativistic full orbit test particle simulations. The calculations retain all three spatial variables describing Particles' trajectories, allowing us to model any transport across the magnetic field. Large energy change is shown to occur for protons, due to the combined effect of standard adiabatic deceleration and a significant contribution from particle drift in the direction opposite to that of the Solar wind electric field. The latter drift-induced deceleration is found to have a stronger effect for SEP energies than for galactic cosmic rays. The kinetic energy of protons injected at 1 MeV is found to be reduced by between 35% and 90% after four days, and for protons injected at 100 MeV by between 20% and 55%. The overall degree of deceleration is a weak function of the scattering mean free path, showing that, although adiabatic deceleration plays a role, a large contribution is due to particle drift. Current SEP transport models are found to account for drift-induced deceleration in an approximate way and their accuracy will need to be assessed in future work.
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relationship between Solar Energetic Particles and properties of flares and cmes statistical analysis of Solar cycle 23 events
Solar Physics, 2015Co-Authors: Mark Dierckxsens, S Dalla, O Malandraki, K Tziotziou, Ioanna Patsou, M S Marsh, Norma Crosby, G TsiropoulaAbstract:A statistical analysis of the relationship between Solar Energetic Particles (SEPs) and properties of Solar flares and coronal mass ejections (CMEs) is presented. SEP events during Solar Cycle 23 are selected that are associated with Solar flares originating in the visible hemisphere of the Sun and that are at least of magnitude M1. Taking into account all flares and CMEs that occurred during this period, the probability for the occurrence of an SEP event near Earth is determined. A strong rise of this probability is observed for increasing flare intensities, more western locations, higher CME speeds, and halo CMEs. The correlations between the proton peak flux and these Solar parameters are derived for a low (> 10 MeV) and high (> 60 MeV) energy range excluding any flux enhancement due to the passage of fast interplanetary shocks. The obtained correlation coefficients are 0.55±0.07 (0.63±0.06) with flare intensity, and 0.56±0.08 (0.40±0.09) with CME speed for E>10 MeV (E>60 MeV). For both energy ranges, the correlations with flare longitude and CME width are very weak or non-existent. Furthermore, the occurrence probabilities, correlation coefficients, and mean peak fluxes are derived in multi-dimensional bins combining the aforementioned Solar parameters. The correlation coefficients are also determined in different proton energy channels ranging from 5 to 200 MeV. The results show that the correlation between the proton peak flux and the CME speed decreases with energy, while the correlation with the flare intensity shows the opposite behaviour. Furthermore, the correlation with the CME speed is stronger than the correlation with the flare intensity below 15 MeV and becomes weaker above 20 MeV. When the enhancements in the flux profiles due to interplanetary shocks are not excluded, only a small but not very significant change is observed in the correlation coefficients between the proton peak flux below 7 MeV and the CME speed.
M. E. Wiedenbeck - One of the best experts on this subject based on the ideXlab platform.
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Fractionation of Solar Energetic Particles and Solar wind according to first ionization potential
Advances in Space Research, 2020Co-Authors: R. A. Mewaldt, C. M. S. Cohen, R. A. Leske, E. R. Christian, A. C. Cummings, E. C. Stone, T. T. Von Rosenvinge, M. E. WiedenbeckAbstract:Although it is well known that Solar Energetic Particles are depleted in elements with first ionization potential (FIP) greater than ∼10 eV, it is less well known that the degree of FIP fractionation varies from event to event. Similar fractionation patterns and variations are observed in the Solar wind, suggesting that these variations may have a common origin. We review evidence for the FIP-related fractionation of SEPs and compare it with FIP fractionation effects in the Solar wind at 1 AU. On the basis of several significant differences between the Solar wind and SEP compositions, we suggest that most Solar Energetic Particles are not simply an accelerated sample of the average Solar wind as observed at 1 AU; rather, Solar Particles and fast and slow Solar wind appear to be distinct samples of coronal material with distinctly different FIP-fractionation patterns.
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Are Solar Energetic Particles an Accelerated Sample of Solar Wind
2020Co-Authors: R. A. Mewaldt, C. M. S. Cohen, R. A. Leske, E. R. Christian, A. C. Cummings, E. C. Stone, T. T. Von Rosenvinge, M. E. WiedenbeckAbstract:In the current picture of gradual Solar Energetic particle (SEP) events, the acceleration is believed to take place at a shock driven by a coronal mass ejection as it moves through the corona and out into the Solar wind. It is often assumed that the Solar wind provides the seed Particles that are accelerated and later observed at 1 AU. We compare Solar Energetic particle and Solar wind composition measurements, focusing on a comparison of the fractionation patterns with respect to first ionization potential. On the basis of several significant differences between the Solar wind and SEP compositions, we conclude that most SEPs with energies >5 MeV/nucleon are not simply an accelerated sample of Solar wind. Rather, SEPs and fast and slow Solar wind appear to be distinct samples of coronal material with significantly different fractionation patterns. This implies that Solar Energetic Particles must be accelerated within a few Solar radii of the Sun.
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energy spectra of 3he rich Solar Energetic Particles associated with coronal waves
arXiv: Solar and Stellar Astrophysics, 2016Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, M. E. WiedenbeckAbstract:In addition to their anomalous abundances, 3He-rich Solar Energetic Particles (SEPs) show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. Solar sources of these Particles have been often associated with jets and narrow CMEs, which are the signatures of magnetic reconnection involving open field. Recent reports on new associations with large-scale EUV waves bring new insights on acceleration and transport of 3He-rich SEPs in the corona. We examined energy spectra for 32 3He-rich SEP events observed by ACE at L1 near Solar minimum in 2007-2010 and compared the spectral shapes with Solar flare signatures obtained from STEREO EUV images. We found the events with jets or brightenings tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.
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STEREO Observations of Solar Energetic Particles
2011Co-Authors: Tycho Vonrosenvinge, R. A. Mewaldt, C. M. S. Cohen, R. A. Leske, E. R. Christian, E. C. Stone, M. E. WiedenbeckAbstract:We report on observations of Solar Energetic Particle (SEP) events as observed by instruments on the STEREO Ahead and Behind spacecraft and on the ACE spacecraft. We will show observations of an electron event observed by the STEREO Ahead spacecraft on June 12, 2010 located at W74 essentially simultaneously with electrons seen at STEREO Behind at E70. Some similar events observed by Helios were ascribed to fast electron propagation in longitude close to the sun. We will look for independent verification of this possibility. We will also show observations of what appears to be a single proton event with very similar time-history profiles at both of the STEREO spacecraft at a similar wide separation. This is unexpected. We will attempt to understand all of these events in terms of corresponding CME and radio burst observations.
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Solar elemental composition based on studies of Solar Energetic Particles
Space Science Reviews, 2007Co-Authors: C. M. S. Cohen, R. A. Mewaldt, R. A. Leske, A. C. Cummings, E. C. Stone, T. T. Von Rosenvinge, M. E. Wiedenbeck, G. M. MasonAbstract:Solar abundances can be derived from the composition of the Solar wind and Solar Energetic Particles (SEPs) as well as obtained through spectroscopic means. Past comparisons have suggested that all three samples agree well, when rigidity-related fractionation effects on the SEPs were accounted for. It has been known that such effects vary from one event to the next and should be addressed on an event-by-event basis. This paper examines event variability more closely, particularly in terms of energy-dependent SEP abundances. This is now possible using detailed SEP measurements spanning several decades in energy from the Ultra Low Energy Isotope Spectrometer (ULEIS) and the Solar Isotope Spectrometer (SIS) on the ACE spacecraft. We present examples of the variability of the elemental composition with energy and suggest they can be understood in terms of diffusion from the acceleration region near the interplanetary shock. By means of a spectral scaling procedure, we obtain energy-independent abundance ratios for 14 large SEP events and compare them to reported Solar wind and coronal abundances as well as to previous surveys of SEP events.
