Acceleration of interstellar pickup ions in the disturbed solar wind observed on Ulysses

Gloeckler, G.; Geiss, J.; Roelof, E. C.; Fisk, L. A.; Ipavich, F. M.; Ogilvie, K. W.; Lanzerotti, L. J.; Steiger, R. von; Wilken, B.

doi:10.1029/94ja01509

Cited by 244 publications

(195 citation statements)

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“…There is also strong observational evidence for a suprathermal seed source, due to the presence of ions in CIRs that are extremely rare in the bulk solar wind. The first such ion detected in CIRs was singly ionized He, which at 1 AU consists of 10%-20% of the total He (Hilchenbach et al 1999;Chotoo et al 2000;Möbius et al 2002), and at several AU He + dominates the CIR He abundance (Gloeckler et al 1994). During individual CIR events at 1 AU the He + abundance increases with time during the event, presumably due to improving the magnetic connection between 1 AU and increasingly efficient portions of the distant shock (Morris et al 2001).…”

Section: Abundances and Seed Populationmentioning

confidence: 99%

“…It has long been known that there are significant differences between the heavy-ion composition of CIRs and other heliospheric energetic particle populations, such as shock-accelerated or solar energetic particles (SEPs). Furthermore, the presence of singly ionized energetic He in CIRs makes it clear that the seed population was not simply solar wind, since solar wind He + is extremely rare (e.g., Gloeckler et al 1994;Chotoo et al 2000;Möbius et al 2002). Using high-resolution spectrometers on the Advanced Composition Explorer (ACE ) spacecraft, we have surveyed CIR events over the recent solar cycle, measuring the energy spectra and composition with much higher accuracy than previously possible.…”

Section: Introductionmentioning

confidence: 99%

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Abundances and Energy Spectra of Corotating Interaction Region Heavy Ions Observed during Solar Cycle 23

Mason

Leske

Desai

et al. 2008

ApJ

103

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Using instruments on the ACE spacecraft, we surveyed the heavy-ion spectra and composition over the range HeFe for 41 corotating interaction regions (CIRs) during 1998-2007. Below $1 MeV nucleon À1 the spectra are power laws in kinetic energy nucleon À1 with an average spectral index of 2:51 AE 0:10, rolling over above $1 MeV nucleon À1 to power-law spectra with an average index of 4:47 AE 0:17. The spectral shapes for different species are similar, leading to relative abundances that are constant over our energy range, even though the intensities cover up to 8 orders of magnitude. Relative to oxygen, the measured abundances at 385 keV nucleon À1 for 4 He, C, N, Ne, Mg, Si, S, Ca, and Fe are 273 AE 72, 0:760 AE 0:023, 0:143 AE 0:005, 0:206 AE 0:009, 0:148 AE 0:006, 0:095 AE 0:005, 0:028 AE 0:002, 0:007 AE 0:001, and 0:088 AE 0:007, respectively. Except for an overabundance of 4 He and Ne, the abundances are quite close to that of the fast solar wind. We have found 3 He/ 4 He ratios to be enhanced over solar wind values in $40% of the CIRs. The Fe/O ratio in individual CIRs is observed to vary over a factor of $10 and is strongly correlated with the solar wind Fe/O ratio measured 2-4 days preceding each CIR. Taken together with previous studies showing the presence of pickup He + in CIRs, the observational data provide evidence that CIR energetic particles are accelerated out of a suprathermal ion pool that includes heated solar wind ions, pickup ions, and remnant suprathermals from impulsive solar energetic particle events.

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Section: Abundances and Seed Populationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Abundances and Energy Spectra of Corotating Interaction Region Heavy Ions Observed during Solar Cycle 23

Mason

Leske

Desai

et al. 2008

ApJ

103

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“…Especially, shocks or compression regions like Stream Interaction Regions (SIRs) with a high level of turbulence (cf. Gloeckler et al 1994;Schwadron et al 1996) can efficiently accelerate PUIs above their injection speed. In turn, this means that the He + cutoff shape and location may be significantly altered by the increased abundance of accelerated PUIs, which would contradict the assumption that the PUI cutoff VDF is comparable at all ecliptic longitudes.…”

Section: Acceleration Sitesmentioning

confidence: 99%

Challenges in the determination of the interstellar flow longitude from the pickup ion cutoff

Taut

Berger

Möbius

et al. 2018

A&A

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Context. The interstellar flow longitude corresponds to the Sun's direction of movement relative to the local interstellar medium. Thus, it constitutes a fundamental parameter for our understanding of the heliosphere and, in particular, its interaction with its surroundings, which is currently investigated by the Interstellar Boundary EXplorer (IBEX). One possibility to derive this parameter is based on pickup ions (PUIs) that are former neutral ions that have been ionized in the inner heliosphere. The neutrals enter the heliosphere as an interstellar wind from the direction of the Sun's movement against the partially ionized interstellar medium. PUIs carry information about the spatial variation of their neutral parent population (density and flow vector field) in their velocity distribution function. From the symmetry of the longitudinal flow velocity distribution, the interstellar flow longitude can be derived. Aims. The aim of this paper is to identify and eliminate systematic errors that are connected to this approach of measuring the interstellar flow longitude; we want to minimize any systematic influences on the result of this analysis and give a reasonable estimate for the uncertainty. Methods. We use He + data measured by the PLAsma and SupraThermal Ion Composition (PLASTIC) sensor on the Solar TErrestrial RElations Observatory Ahead (STEREO A) spacecraft. We analyze a recent approach, identify sources of systematic errors, and propose solutions to eliminate them. Furthermore, a method is introduced to estimate the error associated with this approach. Additionally, we investigate how the selection of interplanetary magnetic field angles, which is closely connected to the pickup ion velocity distribution function, affects the result for the interstellar flow longitude. Results. We find that the revised analysis used to address part of the expected systematic effects obtains significantly different results than presented in the previous study. In particular, the derived uncertainties are considerably larger. Furthermore, an unexpected systematic trend of the resulting interstellar flow longitude with the selection of interplanetary magnetic field orientation is uncovered.

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“…Thus, traditional DSA theory is not adequate to describe the acceleration process of these particles. Besides, pickup ions have been observed to be efficiently injected into the acceleration process by the forward-reverse shock pair, the bound of corotating interaction regions (CIRs; Gloeckler et al 1994;Scholer et al 1999). In CIRs, pickup ions have speeds between zero and twice the solar wind speed, and thus part of the pickup ion distribution constitutes a suprathermal particle population.…”

Section: Introductionmentioning

confidence: 99%

Acceleration of Low-Energy Ions at Parallel Shocks With a Focused Transport Model

Zuo

Zhang

Rassoul

2013

ApJ

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We present a test particle simulation on the injection and acceleration of low-energy suprathermal particles by parallel shocks with a focused transport model. The focused transport equation contains all necessary physics of shock acceleration, but avoids the limitation of diffusive shock acceleration (DSA) that requires a small pitch angle anisotropy. This simulation verifies that the particles with speeds of a fraction of to a few times the shock speed can indeed be directly injected and accelerated into the DSA regime by parallel shocks. At higher energies starting from a few times the shock speed, the energy spectrum of accelerated particles is a power law with the same spectral index as the solution of standard DSA theory, although the particles are highly anisotropic in the upstream region. The intensity, however, is different from that predicted by DSA theory, indicating a different level of injection efficiency. It is found that the shock strength, the injection speed, and the intensity of an electric cross-shock potential (CSP) jump can affect the injection efficiency of the low-energy particles. A stronger shock has a higher injection efficiency. In addition, if the speed of injected particles is above a few times the shock speed, the produced power-law spectrum is consistent with the prediction of standard DSA theory in both its intensity and spectrum index with an injection efficiency of 1. CSP can increase the injection efficiency through direct particle reflection back upstream, but it has little effect on the energetic particle acceleration once the speed of injected particles is beyond a few times the shock speed. This test particle simulation proves that the focused transport theory is an extension of DSA theory with the capability of predicting the efficiency of particle injection.

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Acceleration of interstellar pickup ions in the disturbed solar wind observed on Ulysses

Cited by 244 publications

References 18 publications

Abundances and Energy Spectra of Corotating Interaction Region Heavy Ions Observed during Solar Cycle 23

Abundances and Energy Spectra of Corotating Interaction Region Heavy Ions Observed during Solar Cycle 23

Challenges in the determination of the interstellar flow longitude from the pickup ion cutoff

Acceleration of Low-Energy Ions at Parallel Shocks With a Focused Transport Model

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