Abstract
We examine the production of energetic neutral atoms (ENAs) in solar flares and coronal mass ejection (CME)-driven shocks and their subsequent propagation to 1 au. Time profiles and fluence ...spectra of solar ENAs at 1 au are computed for two scenarios: (1) ENAs are produced downstream at CME-driven shocks, and (2) ENAs are produced at large-scale post-flare loops in solar flares. Both the time profiles and fluence spectra for these two scenarios are vastly different. Our calculations indicate that we can use solar ENAs as a new probe to examine the underlying acceleration process of solar energetic particles (SEPs) and to differentiate the two acceleration sites: large loops in solar flares and downstream of CME-driven shocks, in large SEP events.
Abstract
We report on the annual variation of quiet-time suprathermal ion composition for C through Fe using Advanced Composition Explorer (ACE)/Ultra-Low Energy Isotope Spectrometer data over the ...energy range 0.3–1.28 MeV nuc
−1
from 1998 through 2019, covering solar cycle 23's rising phase through Solar Cycle 24's declining phase. Our findings are: (1) quiet-time suprathermal abundances resemble CIR-associated particles during solar minima; (2) quiet-time suprathermals are M/Q fractionated in a manner that is consistent with M/Q fractionation in large gradual solar energetic particle events (GSEP) during solar maxima; and (3) variability within the quiet-time suprathermal pool increases as a function of M/Q and is consistent with the analogous variability in GSEP events. From these observations, we infer that quiet-time suprathermal ions are remnants of CIRs in solar minima and GSEP events in solar maxima. Coincident with these results, we also unexpectedly show that S behaves like a low FIP ion in the suprathermal regime, and is therefore drawn from low FIP solar sources.
Abstract
We investigate 16 solar energetic electron (SEE) events measured by WIND/3DP with a double-power-law spectrum and the associated western hard X-ray (HXR) flares measured by RHESSI with good ...count statistics, from 2002 February to 2016 December. In all the 16 cases, the presence of an SEE power-law spectrum extending down to ≤5 keV at 1 au implies that the SEE source would be high in the corona, at a heliocentric distance of ≥1.3 solar radii, while the footpoint or footpoint-like emissions shown in HXR images suggest that the observed HXRs are likely produced mainly by HXR-producing electrons via thick-target bremsstrahlung processes very low in the corona. We find that for all the 16 cases, the estimated power-law spectral index of HXR-producing electrons is no less than the observed high-energy spectral index of SEEs, and it shows a positive correlation with the high-energy spectral index of SEEs. In addition, the estimated number of SEEs is only ∼10
−4
–10
−2
of the estimated number of HXR-producing electrons at energies above 30 keV, but with a positive correlation between the two numbers. These results suggest that in these cases, SEEs are likely formed by upward-traveling electrons from an acceleration source high in the corona, while their downward-traveling counterparts may undergo a secondary acceleration before producing HXRs via thick-target bremsstrahlung processes. In addition, the associated
3
He/
4
He ratio is positively correlated with the observed high-energy spectral index of SEEs, indicating a possible relation of the
3
He ion acceleration with high-energy SEEs.
Abstract
We report on the annual variation of quiet-time suprathermal heavy ion spectral indices for C through Fe in the energy range 0.3–1.28 MeV nuc
−1
during Solar Cycle 23's rising phase through ...Solar Cycle 24's declining phase. These Advanced Composition Explorer/Ultra-Low Energy Isotope Spectrometer measurements cover 1998–2019. We show that the average quiet-time suprathermal spectral index across species is
γ
= 2.5 ± 0.3. Such observations may imply that quiet-time suprathermals are the result of a superposition of various underlying acceleration and transport processes that accelerate suprathermal ions. As such, they may be remnants of particles from discrete events like large and impulsive solar energetic particle events along with corotating interaction regions that have decayed in intensity.
Pan‐Spectrum Fitting Formula for Suprathermal Particles Liu, Zixuan; Wang, Linghua; Wimmer‐Schweingruber, Robert F. ...
Journal of geophysical research. Space physics,
December 2020, 2020-12-00, 20201201, Letnik:
125, Številka:
12
Journal Article
Recenzirano
Odprti dostop
We propose a pan‐spectrum fitting formula of suprathermal particles,
J=A×E−β11+EE0αβ1−β2α, where J is the particle flux (or intensity), E is the particle energy, A is the amplitude coefficient, E0 ...represents the spectral transition energy, α (>0) describes the sharpness and width of spectral transition around E0, and the power‐law index β1 (β2) gives the spectral shape before (after) the transition. This formula incorporates many commonly used spectrum functions as special cases. When α goes to infinity (zero), this spectral formulabecomes the classical double‐power‐law (logarithmic‐parabola) function. When both β2 and E0 approach infinity and α is equal to 1, this formula can be simplified to the Ellison‐Ramaty function. Under some other specific parameter conditions, this formula can be transformed to the Kappa or Maxwellian distribution. Considering the uncertainties in both particle intensity and energy, we improve the fitting method and fit this pan‐spectrum formula well to the representative energy spectra of various suprathermal particle phenomena including SEPs (electrons, protons, 3He, and heavier ions), ESPs, bow‐shocked electrons, solar wind suprathermal electrons, anomalous cosmic rays, and hard X‐rays. Therefore, this pan‐spectrum fitting formula would help us comparatively examine the properties of energy spectrum of different suprathermal particle phenomena typically with a single energy break.
Key Points
We propose a new spectrum formula that is suitable to fit the single‐break energy spectra of various suprathermal particle phenomena
We can obtain the shape and width of energy transition in particle spectrum
This fitting enables us to quantitatively compare the spectral features of different suprathermal particles
Suprathermal ion composition associated with corotating interaction regions (CIRs) exhibited a solar cycle variation during solar cycle 23 and the beginning of solar cycle 24. However, it is unclear ...if this variation would remain when considering all of solar cycle 24, or whether the variations in the CIR-associated suprathermal ion composition would change. Using 20 yr of Advanced Composition Explorer observations (1998-2018), we present a comparison of the suprathermal ion compositions for solar cycles 23 and 24. The energetic particle content for the two solar cycles is found to be remarkably similar. The observed solar cycle variations in 0.32-0.45 MeV/nuc Fe/O previously observed for solar cycle 23 was seen to be largely repeated in solar cycle 24, both in solar cycle phase and magnitude. A small enhancement in CIR-associated Fe/O during the declining phase was observed for both solar cycles. The CIR event-averaged intensities of Fe and O were also found to have a slight solar cycle dependence, with the Fe/O ratio being more closely bound to the intensity of Fe ions. Additionally, the elemental abundance versus O ratios compared to the Fe/C ratios were found to follow the same trends for both solar cycles, with high Fe/C ratio events occurring mostly during solar maximum.
Background. We previously compared the safety profile of three formulations of intravenous iron used during 1998–2000 and found higher rates of adverse drug events (ADEs) associated with the use of ...higher molecular weight iron dextran and sodium ferric gluconate complex compared with lower molecular weight iron dextran. Since that time, iron sucrose has become widely available and clinicians have gained additional experience with sodium ferric gluconate complex. Methods. We obtained data from the United States Food and Drug Administration (FDA) on ADEs attributed to the provision of four formulations of intravenous iron during 2001–2003, including higher and lower molecular weight iron dextran, sodium ferric gluconate complex and iron sucrose. We estimated the odds of intravenous iron-related ADEs using 2 × 2 tables and the χ2 test. Results. The total number of reported parenteral iron-related ADEs was 1141 among approximately 30 063 800 doses administered, yielding a rate of 3.8 × 10−5, or roughly 38 per million. Eleven individuals died in association with the ADE. Relative to lower molecular weight iron dextran, total and life-threatening ADEs were significantly more frequent among recipients of higher molecular weight iron dextran and significantly less frequent among recipients of sodium ferric gluconate complex and iron sucrose. The absolute rates of life-threatening ADEs were 0.6, 0.9, 3.3 and 11.3 per million for iron sucrose, sodium ferric gluconate complex, lower molecular weight iron dextran and higher molecular weight iron dextran, respectively. Based on differences in the average wholesale price of iron sucrose and lower molecular weight iron dextran in the US, the cost to prevent one life-threatening ADE related to the use of lower molecular weight iron dextran was estimated to be $5.0–7.8 million. The cost to prevent one lower molecular weight iron dextran-related death was estimated to be $33 million. Conclusions. The frequency of intravenous iron-related ADEs reported to the FDA has decreased, and overall, the rates are extremely low. This is the fourth report suggesting increased risks associated with the provision of higher molecular weight iron dextran. Life-threatening and other ADEs appear to be lower with the use of non-dextran iron formulations, although the cost per ADE prevented is extremely high.
We survey the statistical properties of 1191 solar electron events observed by the WIND 3DP instrument from < 1 keV to gap300 keV for a solar cycle (1995 through 2005). After taking into account ...times of high background, the corrected occurrence frequency of solar electron events versus peak flux exhibits a power-law distribution over three orders of magnitude with exponents between -1.0 and -1.6 for different years, comparable to the frequency distribution of solar proton events, microflares, and coronal mass ejections (CMEs), but significantly flatter than that of soft X-ray (SXR) flares. At 40 keV (2.8 keV), the integrated occurrence rate above ~0.29 (~330) cm super(-2) s super(-1) sr super(-1) keV super(-1) near 1 AU is ~1000 year super(-1) (~600 year super(-1)) at solar maximum and ~35 year super(-1) (~25 year super(-1)) at solar minimum, about an order of magnitude larger than the observed occurrence rate. We find these events typically extend over ~45degrees in longitude, implying the occurrence rate over the whole Sun is ~10 super(4) year super(-1) near solar maximum. The observed solar electron events have a 98.75% association with type III radio bursts, suggesting all type III bursts may be associated with a solar electron event. They have a close (~76%) association with the presence of low-energy (~0.02-2 MeV nucleon super(-1)), super(3)He-rich ( super(3)He/ super(4)He > or =, slanted 0.01) ion emissions measured by the ACE ULEIS instrument. For these electron events, only ~35% are associated with a reported GOES SXR flare, but ~60% appear to be associated with a CME, with ~50% of these CMEs being narrow. These electrons are often detected down to below 1 keV, indicating a source high in the corona.
Correction to: Solar Phys (2019) 294:33
https://doi.org/10.1007/s11207-019-1420-z
The original article has been corrected due to typesetting mistakes made in the last paragraph of section
2. ...Observations.
We investigated
3
He-rich solar energetic particle (SEP) events in the current solar cycle starting in 2009 through 2017. Both “impulsive” (flare-related)
3
He-rich and CME-related “gradual” events ...are included. In the former solar cycle, we found the number of observed
3
He-rich events correlated with solar activity. The same correlation is seen again in Cycle 24. Because of the comparatively weak activity, both the occurrence of
3
He-rich events and their intensities are significantly less than those from Cycle 23. Interestingly, we found in several of the
3
He-rich events that there is no measurable
4
He intensity increase above the instrument background. Previously, we found that there is a limit on the number of
3
He ions that can be released from the Sun in an impulsive SEP event, while there is no such limit on the
4
He ions (Ho, Roelof, and Mason in
Astrophys. J
.,
621
, L862,
2005
). In this paper, we examine several of these
3
He-rich events in detail and discuss the lack of observable
4
He intensity increases and the implications for the enhancement and acceleration mechanism of this special type of SEP events.
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