<sup>3</sup>He-rich Solar Energetic Particles in Helical Jets on the Sun

Bučík, R.; Innes, D. E.; Mason, G. M.; Wiedenbeck, M. E.; Gómez‐Herrero, R.; Nitta, N.

doi:10.3847/1538-4357/aa9d8f

Cited by 49 publications

(44 citation statements)

References 74 publications

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“…They are electron-rich and show higher charge states (Klecker et al 1984) and dramatic enhancements of the 3 He/ 4 He ratio with respect to the coronal values, as well as enrichments in Fe and other heavy elements (Reames et al 1994;Mason 2007;Reames 2018). Impulsive events appear in association with type III radio bursts and often with solar flares, narrow CMEs, and extreme-ultraviolet (EUV) jets (Kahler et al 2001;Nitta et al 2006;Bučík et al 2018). Recent observations suggest that EUV coronal waves may also affect the injection of 3 He-rich SEPs into interplanetary space during some 3 He-rich events (Bučík et al 2015(Bučík et al , 2016.…”

Section: Science Objectives Of the Energetic Particle Detectormentioning

confidence: 99%

The Energetic Particle Detector

Rodrı́guez-Pacheco

Wimmer‐Schweingruber

Mason

et al. 2020

A&A

118

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After decades of observations of solar energetic particles (SEP) from space-based observatories, relevant questions on particle injection, transport, and acceleration remain open. To address these scientific topics, accurate measurements of the particle properties in the inner heliosphere are needed. In this paper we describe the Energetic Particle Detector (EPD), an instrument suite that is part of the scientific payload aboard the Solar Orbiter mission. Solar Orbiter will approach the Sun as close as 0.28 au and will provide extra-ecliptic measurements beyond ∼ 30 • heliographic latitude during the later stages of the mission. The EPD will measure electrons, protons, and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of megaelectronvolts/nucleons. For this purpose, EPD is composed of four units: the SupraThermal Electrons and Protons (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the High-Energy Telescope (HET) plus the Instrument Control Unit (ICU) that serves as power and data interface with the spacecraft. The low-energy population of electrons and ions will be covered by STEP and EPT, while the high-energy range will be measured by HET. Elemental and isotopic ion composition measurements will be performed by SIS and HET, allowing full particle identification from a few kiloelectronvolts up to several hundreds of megaelectronvolts/nucleons. Angular information will be provided by the separate look directions from different sensor heads, on the ecliptic plane along the Parker spiral magnetic field both forward and backwards, and out of the ecliptic plane observing both northern and southern hemispheres. The unparalleled observations of EPD will provide key insights into long-open and crucial questions about the processes that govern energetic particles in the inner heliosphere.

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Section: Science Objectives Of the Energetic Particle Detectormentioning

confidence: 99%

The Energetic Particle Detector

Rodrı́guez-Pacheco

Wimmer‐Schweingruber

Mason

et al. 2020

A&A

118

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“…The residue from many jets collects in large regions for substantial periods so that 3 Herich, Fe-rich background levels are often seen (Desai et al, 2003;Bučík et al, 2014Bučík et al, , 2015Bučík et al, , 2018aBučík et al, , 2018bChen et al, 2015). Having distinguished differences in the CMEs associated with impulsive and gradual SEP events, we now turn to differences in CMEs that favor different ion seed populations for shock acceleration in gradual SEP events.…”

Section: Comparing Cmesmentioning

confidence: 99%

“…Reames, 1988Reames, , 1995bReames, , 1999Reames, , 2013Reames, , 2015Reames, , 2017aGosling, 1993). In the small "impulsive" SEP events, where acceleration has been traced to sites of magnetic reconnection in solar jets (Kahler, Reames, and Sheeley, 2001;Bučík et al, 2018aBučík et al, , 2018b, element abundances are enhanced as a power-law in mass-to-charge ratio A/Q, increasing by a factor of ≈1000 across the periodic table from H and He to Au and Pb (Reames and Ng, 2004;Reames, Cliver, and Kahler, 2014a) probably because of the reconnection physics (e.g. Drake et al, 2009). In contrast, in the large "gradual" SEP events (Lee, Mewaldt, and Giacalone, 2012;Desai and Giacalone, 2016), shock waves, driven by fast, wide coronal mass ejections (CMEs; Kahler et al, 1984;Lee, 1983Lee, , 2005Zank, Rice, and Wu, 2000;Cliver, Kahler, and Reames, 2004;Gopalswamy et al, 2012), mostly sample ambient coronal material.…”

Section: Introductionmentioning

confidence: 99%

Excess H, Suppressed He, and the Abundances of Elements in Solar Energetic Particles

Reames

2019

Sol Phys

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Recent studies of the abundances of H and He relative to those of heavier ions in solar energetic particle (SEP) events suggest new features in the underlying physics.Impulsive SEP events, defined by uniquely large enhancements of Fe/O, emerge from magnetic reconnection in solar jets. In small, "pure," shock-free, impulsive SEP events, protons with mass-to-charge ratio A/Q = 1 fit the power-law dependence of element abundance enhancements versus A/Q extrapolated from the heavier elements 6 ≤ Z ≤ 56.Sometimes these events have order-of-magnitude suppressions of He, even though H fits with heavier elements, perhaps because of the slower ionization of He during a rapid rise of plasma from the chromosphere. In larger impulsive SEP events, He fits, but there are large proton excesses relative to the power-law fit of Z > 2 ions, probably because associated coronal mass ejections (CMEs) drive shock waves fast enough to reaccelerate the impulsive SEPs but also to sample protons from the ambient solar plasma. In contrast, gradual SEP events are accelerated by wide, fast CME-driven shock waves, but those with smaller, weaker shocks, perhaps quasi-perpendicular, favor impulsive suprathermal residue left by many previous jets, again supplemented with excess protons from ambient coronal plasma. In the larger, more common gradual SEP events, faster, stronger shock waves sample the ambient coronal plasma more deeply, overwhelming any impulsive-ion component, so that proton abundances again fit the same power-law distribution as all other elements. Thus, studies of the power-law behavior in A/Q of SEP element abundances give compelling new information on the varying physics of SEP acceleration and properties of the underlying corona.

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“…Further complicating the behavior, power-law enhancements of elements, also 1000-fold, between He and the heavy elements up to Pb (Reames, 2000(Reames, , 2017aMason et al, 2004;Reames and Ng, 2004;Reames, Cliver, and Kahler, 2014a) were found and were better explained by particle-in-cell simulations of magnetic reconnection (Drake et al, 2009), which produce the power-law dependence on A/Q from rigidity dependence during acceleration. Impulsive SEP events are associated with narrow coronal mass ejections (CMEs) related to solar jets (Kahler, Reames, and Sheeley, 2001;Bučík et al, 2018) driven by magnetic reconnection involving open field lines.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen and the Abundances of Elements in Gradual Solar Energetic-Particle Events

Reames

2019

Sol Phys

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Despite its dominance, hydrogen has been largely ignored in studies of the abundance patterns of the chemical elements in gradual solar energetic-particle (SEP) events; those neglected abundances show a surprising new pattern of behavior. Abundance enhancements of elements with 2 ≤ Z ≤ 56, relative to coronal abundances, show a power-law dependence, versus their average mass-to-charge ratio A/Q, that varies from event to event and with time during events. The ion charge states Q depend upon the source plasma temperature T. For most gradual SEP events, shock waves have accelerated ambient coronal material with T < 2 MK with decreasing power-laws in A/Q. In this case, the proton abundances agree rather well with the power-law fits extrapolated from elements with Z ≥ 6 at A/Q > 2 down to hydrogen at A/Q = 1. Thus the abundances of the elements with Z ≥ 6 fairly accurately predict the observed abundance of H, at a similar velocity, in most SEP events. However, for those gradual SEP events where ion enhancements follow positive powers of A/Q, especially those with T > 2 MK where shock waves have reaccelerated residual suprathermal ions from previous impulsive SEP events, proton abundances commonly exceed the extrapolated expectation, usually by a factor of order ten. This is a new and unexpected pattern of behavior that is unique to the abundances of protons and may be related to the need for more streaming protons to produce sufficient waves for scattering and acceleration of more heavy ions at the shock.

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³He-rich Solar Energetic Particles in Helical Jets on the Sun

Cited by 49 publications

References 74 publications

The Energetic Particle Detector

The Energetic Particle Detector

Excess H, Suppressed He, and the Abundances of Elements in Solar Energetic Particles

Hydrogen and the Abundances of Elements in Gradual Solar Energetic-Particle Events

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3He-rich Solar Energetic Particles in Helical Jets on the Sun

Cited by 49 publications

References 74 publications

The Energetic Particle Detector

The Energetic Particle Detector

Excess H, Suppressed He, and the Abundances of Elements in Solar Energetic Particles

Hydrogen and the Abundances of Elements in Gradual Solar Energetic-Particle Events

Contact Info

Product

Resources

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³He-rich Solar Energetic Particles in Helical Jets on the Sun