Effect of adiabatic deceleration on the focused transport of solar cosmic rays

Ruffolo, D.

doi:10.1086/175489

Cited by 200 publications

(190 citation statements)

References 22 publications

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“…In all the selected events, however, the inferred solar ion injections show a clear delay after the electron injections, even for ions and electrons with the same velocity. If solar energetic ions suffer energy loss due to adiabatic cooling during propagation in the IPM (Ruffolo 1995;Kocharov et al 1998), they would have traveled faster than that the observed ion energies indicate, and their solar release would become even later. Hence, in these events, the derived particle injections likely reflect the solar acceleration of low-energy electrons, of high-energy electrons, and of ions that occur at different times.…”

Section: Summary and Discussionmentioning

confidence: 94%

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The injection of ten electron/³He-rich SEP events

Wang¹,

Krucker

Mason

et al. 2016

A&A

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We have derived the particle injections at the Sun for ten good electron/ 3 He-rich solar energetic particle (SEP) events, using a 1.2 AU particle path length (suggested by analysis of the velocity dispersion). The inferred solar injections of high-energy (∼10 to 300 keV) electrons and of ∼MeV/nucleon ions (carbon and heavier) start with a delay of 17 ± 3 min and 75 ± 14 min, respectively, after the injection of low-energy (∼0.4 to 9 keV) electrons. The injection duration (averaged over energy) ranges from ∼200 to 550 min for ions, from ∼90 to 160 min for low-energy electrons, and from ∼10 to 30 min for high-energy electrons. Most of the selected events have no reported Hα flares or GOES SXR bursts, but all have type III radio bursts that typically start after the onset of a low-energy electron injection. All nine events with SOHO/LASCO coverage have a relatively fast (>570 km s −1 ), mostly narrow ( 30 • ), west-limb coronal mass ejection (CME) that launches near the start of the low-energy electron injection, and reaches an average altitude of ∼1.0 and 4.7 R S , respectively, at the start of the high-energy electron injection and of the ion injection. The electron energy spectra show a continuous power law extending across the transition from low to high energies, suggesting that the low-energy electron injection may provide seed electrons for the delayed high-energy electron acceleration. The delayed ion injections and high ionization states may suggest an ion acceleration along the lower altitude flanks, rather than at the nose of the CMEs.

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Section: Summary and Discussionmentioning

confidence: 94%

“…3a), although these ions and electrons have the same velocity (∼0.060c). If ions suffer energy loss due to adiabatic cooling during their propagation in the IPM, they would have traveled faster than that the observed ion energy indicates and thus, their release at the Sun would have been even later (Ruffolo 1995;Kocharov et al 1998).…”

Section: Observationsmentioning

confidence: 92%

The injection of ten electron/³He-rich SEP events

Wang¹,

Krucker

Mason

et al. 2016

A&A

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“…The transport model solves the focused transport equation (Roelof, 1969;Ruffolo, 1995), including the effects of particle streaming along the magnetic field lines, adiabatic focusing by the diverging magnetic field (Roelof, 1969), interplanetary scattering by magnetic fluctuations frozen into the solar wind (Jokipii, 1966;Dröge, 2003), convection with scattering fluctuations, and adiabatic deceleration resulting from the interplay of scattering and focusing (Ruffolo, 1995;Kocharov et al, 1998). Intensities for the Sun (STEREO A orange-dotted, STEREO B gray-dotted) and Antisun (STEREO A orange-dashed, STEREO B gray-dashed) fields of view are also displayed for both spacecraft in these two panels.…”

Section: Modelingmentioning

confidence: 99%

Interplanetary transport of solar near-relativistic electrons on 2014 August 1 over a narrow range of heliolongitudes

Pacheco

Agueda

Gómez-Herrero

et al. 2017

J. Space Weather Space Clim.

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-We study two consecutive solar near-relativistic (>50 keV) electron events observed on 2014 August 1 by both STEREO spacecraft with a longitudinal separation of only about 35°. The events were unambiguously associated with a solar source location and not accompanied by type II radio bursts or coronal mass ejections. Despite their close location, the two spacecraft were embedded in different solar wind streams and the electron intensities observed by the two STEREOs showed clear differences in onset times, peak intensities and pitch-angle distributions. The apparently better connected spacecraft, STEREO B, observed a smaller and more isotropic intensity increase and a later event onset time than STEREO A. Since the interplanetary transport conditions of solar energetic particles (SEPs) have a direct influence on the characteristics of the observed temporal profiles and the particle anisotropies at the spacecraft location, our aim is to understand if the observations on 2014 August 1 could be explained by different interplanetary transport conditions along each flux tube connecting the spacecraft with the solar source. For that purpose, we use a Monte Carlo interplanetary transport model combined with an inversion procedure to fit the in-situ observations of the two near-relativistic multi-spacecraft electron events. This allows us to obtain the injection profiles at the Sun and infer the transport conditions, which are characterized by the electron radial mean free path, l r . We obtain an almost simultaneous release of electrons for both spacecraft in both events. The release is consistent with the timing and duration of the type III radio burst emission and it is larger for STEREO B, the better connected spacecraft. In addition, we obtain different transport conditions in different solar wind streams. We find that the stream in which STEREO B was embedded was more diffusive (l r = 0.1AU for Event I and l r = 0.06AU for Event II) than the stream in which STEREO A was embedded (l r = 0.31AU for Event I and l r = 0.37AU for Event II). These different transport regimes are sufficient to explain the early onset for the worse connected spacecraft, STEREO A, and the observation of larger and more anisotropic intensities.

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“…We describe the propagation of protons from a solar event by numerically solving a Fokker-Planck equation of pitch-angle transport that includes the effects of interplanetary scattering, adiabatic deceleration and solar wind convection (Roelof 1969;Ruffolo 1995;Nutaro, Riyavong, & Ruffolo 2001). We are assuming transport along the mean magnetic field, as expected when there is good magnetic connection between the source and the observer.…”

Section: Injection Near the Sun: Precision Modelingmentioning

confidence: 99%

Transport and Acceleration of Solar Energetic Particles from Coronal Mass Ejection Shocks

Ruffolo¹

2004

Proc. IAU

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Abstract. After a brief overview of solar energetic particle (SEP) emission from coronal mass ejection (CME) shocks, we turn to a discussion of their transport and acceleration. The high energy SEP are accelerated near the Sun, and because of their well-known source location, their transport can be modeled quantitatively to obtain precise information on the injection function (number of particles emitted vs. time), including a determination of the onset time to within 1 min. For certain events, transport modeling also indicates magnetic topology with mirroring or closed field loops. Important progress has also been made on the transport of low energy SEP from very strong events, which can display exhibit interesting saturation effects and compositional variations. The acceleration of SEP by CME-driven shocks in the interplanetary medium is attributed to diffusive shock acceleration, but the spectrum of SEP production is typically modeled empirically. Recent progress has largely focused on using detailed composition measurements to determine fractionation effects of shock acceleration and even to clarify the nature of the seed population. In particular, there are many indications that the seed population is suprathermal (pre-energized) and the injection problem is not relevant to acceleration at interplanetary CME-driven shocks. We argue that the finite time available for shock acceleration provides the best explanation of the high-energy rollover.

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Effect of adiabatic deceleration on the focused transport of solar cosmic rays

Cited by 200 publications

References 22 publications

The injection of ten electron/³He-rich SEP events

The injection of ten electron/³He-rich SEP events

Interplanetary transport of solar near-relativistic electrons on 2014 August 1 over a narrow range of heliolongitudes

Transport and Acceleration of Solar Energetic Particles from Coronal Mass Ejection Shocks

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Effect of adiabatic deceleration on the focused transport of solar cosmic rays

Cited by 200 publications

References 22 publications

The injection of ten electron/3He-rich SEP events

The injection of ten electron/3He-rich SEP events

Interplanetary transport of solar near-relativistic electrons on 2014 August 1 over a narrow range of heliolongitudes

Transport and Acceleration of Solar Energetic Particles from Coronal Mass Ejection Shocks

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The injection of ten electron/³He-rich SEP events

The injection of ten electron/³He-rich SEP events