A Novel Technique to Infer Ionic Charge States of Solar Energetic Particles

Sollitt, L. S.; Stone, E. C.; Mewaldt, R. A.; Cohen, C. M. S.; Cummings, A. C.; Leske, R. A.; Wiedenbeck, M. E.; Rosenvinge, T. T. von

doi:10.1086/587121

Cited by 11 publications

(15 citation statements)

References 28 publications

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“…These results may be compared with the high energy Q(Fe) results from SAMPEX/MAST [6] shown in Figure 1 as well as with ACE/SIS results [10]. The Q(Fe)=15.3±2.6 value measured by ACE/SIS for the 8 March 2012 event places it in the category of low Q(Fe) events.…”

Section: Resultsmentioning

confidence: 71%

“…(Note that in Equation 1, τ C does not specifically refer to the carbon time decay constant but rather to a low energy constant. We retain this labeling for consistency with Sollitt et al [10]. )…”

Section: Inferred Ionic Charge States By Time Decay Measurementsmentioning

confidence: 78%

“…The method this analysis employs has been described in detail along with its derivation by Sollitt et al [10], in conjunction with its application to ACE/SIS data. We have continued employing this method both to ACE data as well as to STEREO data [11].…”

Section: Inferred Ionic Charge States By Time Decay Measurementsmentioning

confidence: 99%

“…passage of shocks distorting smoothly decaying profiles), the method is inapplicable for that event. The fits are described by Sollitt et al [10] as maximum likelihood fits, but for this paper, high intensity events were selected for which least-squares fitting of the time decay profiles was sufficiently accurate.…”

Section: Inferred Ionic Charge States By Time Decay Measurementsmentioning

confidence: 99%

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Inferred Ionic Charge States for Solar Energetic Particle Events from 2012-2015 with ACE and STEREO

Labrador¹,

Sollitt²,

Cohen³

et al. 2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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Mean ionic charge states for SEP events can reflect source temperatures, stripping during acceleration and transport, and the composition of source material.Multi-spacecraft measurements of mean ionic charge states for single SEP events can also demonstrate longitudinal dependence depending on seed particle composition or acceleration conditions. in previous studies, we calculated inferred high-energy ionic charge states for SEP events. The analysis method fits the energy dependence of decay times for each element in SEP events, combined with charge-to-mass ratios relative to a calibration element, and derives mean charge state estimates for elements from O to Fe. Previously, we applied the method using ACE and STEREO data to SEP events through the beginning of 2012, in order to elucidate evidence on seed populations or longitudinal variations with charge state for single SEP events, with varying results. In this paper, we continue applying the method to new SEP events from 2012 to 2015 in the ACE and STEREO data. With the three spacecraft widely spread apart during this time period, there are fewer single SEP events with multi-spacecraft data, but the wide spacing allows more SEP candidate events to be considered, separately, than would be available with just a single spacecraft. Our new results for two SEP events continue to be consistent with observed correlation between Q(Fe) and Fe/O in previous events.

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Section: Resultsmentioning

confidence: 71%

Section: Inferred Ionic Charge States By Time Decay Measurementsmentioning

confidence: 78%

Section: Inferred Ionic Charge States By Time Decay Measurementsmentioning

confidence: 99%

Section: Inferred Ionic Charge States By Time Decay Measurementsmentioning

confidence: 99%

See 2 more Smart Citations

Inferred Ionic Charge States for Solar Energetic Particle Events from 2012-2015 with ACE and STEREO

Labrador¹,

Sollitt²,

Cohen³

et al. 2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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“…This would result in energy and species independent decay time constants as seen in Figure 5. In cases where the scattering free-escape outer boundary is closer to the observer, then particle speed and mean free path can lead to decay time constants that vary with both energy and species (Sollitt et al, 2003;Sollitt, 2004), in contrast to the behavior shown in Figure 5. By probing the properties of these particle populations at widely varying longitudes, these contrasting models can be tested.…”

Section: Large Solar Particle Eventsmentioning

confidence: 97%

The Suprathermal Ion Telescope (SIT) for the IMPACT/SEP Investigation

et al.

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The Solar-Terrestrial Relations Observatory (STEREO) mission addresses critical problems of the physics of explosive disturbances in the solar corona, and their propagation and interactions in the interplanetary medium between the Sun and Earth. The InSitu-Measurements of Particles and CME Transients (IMPACT) investigation observes the consequences of these disturbances and other transients at 1 AU. The generation of energetic particles is a fundamentally important feature of shock-associated Coronal Mass Ejections (CMEs) and other transients in the interplanetary medium. Multiple sensors within the IM-PACT suite measure the particle population from energies just above the solar wind up to hundreds of MeV/nucleon. This paper describes a portion of the IMPACT Solar Energetic Particles (SEP) package, the Suprathermal Ion Telescope (SIT) which identifies the heavy ion composition from the suprathermal through the energetic particle range (∼few 10 s of keV/nucleon to several MeV/nucleon). SIT will trace and identify processes that energize low energy ions, and characterize their transport in the interplanetary medium. SIT is a timeof-flight mass spectrometer with high sensitivity designed to derive detailed multi-species particle spectra with a cadence of 60 s, thereby enabling detailed studies of shock-accelerated and other energetic particle populations observed at 1 AU.

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Gradual SEP Events

Reames

2021

Solar Energetic Particles

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Gradual solar energetic-particle (SEP) events are “big proton events” and are usually much more “gradual” in their decay than in their onset. As their intensities increase, particles streaming away from the shock amplify Alfvén waves that scatter subsequent particles, increasing their acceleration, eventually limiting ion flow at the “streaming limit.” Waves generated by higher-speed protons running ahead can also throttle the flow of lower-energy ions, flattening spectra and altering abundances in the biggest SEP events. Thus, we find that the A/Q-dependence of scattering causes element-abundance patterns varying in space and time, which define source-plasma temperatures T, since the pattern of Q values of the ions depends upon temperature. Differences in T explain much of the variation of element abundances in gradual SEP events. In nearly 70% of gradual events, SEPs are shock-accelerated from ambient coronal plasma of ~0.8–1.6 MK, while 24% of the events involve material with T ≈ 2–4 MK re-accelerated from residual impulsive-suprathermal ions with pre-enhanced abundances. This source-plasma temperature can occasionally vary with solar longitude across the face of a shock. Non-thermal variations in ion abundances in gradual SEP events reaccelerated from the 2–4 MK impulsive source plasma are reduced, relative to those in the original impulsive SEPs, probably because the accelerating shock waves sample a pool of ions from multiple jet sources. Late in gradual events, SEPs become magnetically trapped in a reservoir behind the CME where spectra are uniform in space and decrease adiabatically in time as the magnetic bottle containing them slowly expands. Finally, we find variations of the He/O abundance ratio in the source plasma of different events.

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A Novel Technique to Infer Ionic Charge States of Solar Energetic Particles

Cited by 11 publications

References 28 publications

Inferred Ionic Charge States for Solar Energetic Particle Events from 2012-2015 with ACE and STEREO

Inferred Ionic Charge States for Solar Energetic Particle Events from 2012-2015 with ACE and STEREO

The Suprathermal Ion Telescope (SIT) for the IMPACT/SEP Investigation

Gradual SEP Events

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