Scanning an Interplanetary Magnetic Cloud Using High‐Energy Protons

Kocharov, L. G.; Saloniemi, O.; Torsti, J.; Kovaltsov, G. A.; Riihonen, E.

doi:10.1086/509797

Cited by 13 publications

(10 citation statements)

References 17 publications

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“…The proton flux anisotropy data reveal the long-lasting streaming of deka-MeV protons far upstream of the coronal-mass-ejectiondriven shock that still expands near the Sun. The same anisotropy measurements, as well as the interplanetary magnetic field data, indicate that the rate of pitch-angle scattering of deka-MeV protons is highly variable and may differ by an order of magnitude in two neighboring magnetic flux tubes of the solar wind (Torsti et al 2004;Kocharov et al 2007b), while an overall spread of the scattering frequency (the fitted mean free path) in different SEP events comprises at least two orders of magnitude. Figure 1 illustrates a simple model employed to study how the strong intermittence of the particle mean free path could affect the particle acceleration in a shock wave and how the accelerated particle could escape to far upstream of the shock.…”

Section: Observational and Theoretical Motivationmentioning

confidence: 61%

The Effect of Turbulence Intermittence on the Emission of Solar Energetic Particles by Coronal and Interplanetary Shocks

Kocharov

Laitinen

Vainio

2013

ApJ

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Major solar energetic particle events are associated with shock waves in solar corona and solar wind. Fast scattering of charged particles by plasma turbulence near the shock wave increases the efficiency of the particle acceleration in the shock, but prevents particles from escaping ahead of the shock. However, the turbulence energy levels in neighboring magnetic tubes of solar wind may differ from each other by more than one order of magnitude. We present the first theoretical study of accelerated particle emission from an oblique shock wave propagating through an intermittent turbulence background that consists of both highly turbulent magnetic tubes, where particles are accelerated, and quiet tubes, via which the accelerated particles can escape to the non-shocked solar wind. The modeling results imply that the presence of the fast transport channels penetrating the shock and cross-field transport of accelerated particles to those channels may play a key role in high-energy particle emission from distant shocks and can explain the prompt onset of major solar energetic particle events observed near the Earth's orbit.

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Section: Observational and Theoretical Motivationmentioning

confidence: 61%

The Effect of Turbulence Intermittence on the Emission of Solar Energetic Particles by Coronal and Interplanetary Shocks

Kocharov

Laitinen

Vainio

2013

ApJ

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“…We have applied a previous numerical model [ Kocharov et al , , ] to the analysis of the high‐energy proton distribution inferred from the neutron monitor data of 17 May 2012. The model is able to reproduce a double‐peak distribution of protons over their pitch angle, with the maxima caused by directly arriving solar particles at α ≈0° and by bounced particles at α ≈130°, assuming a large mean‐free path and a bottleneck with the magnetic ratio ≈4 at heliocentric distances from 0.9 to 1.2 AU.…”

Section: Resultsmentioning

confidence: 99%

“…We have applied a previous numerical model [Kocharov et al, 2005[Kocharov et al, , 2007 to the analysis of the high-energy proton MISHEV ET AL. distribution inferred from the neutron monitor data of 17 May 2012.…”

Section: Resultsmentioning

confidence: 99%

Analysis of the ground level enhancement on 17 May 2012 using data from the global neutron monitor network

2014

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We have analyzed the data of the world neutron monitor network for the first ground level enhancement of solar cycle 24, the ground level enhancement (GLE) on 17 May 2012. A newly computed neutron monitor yield function and an inverse method are applied to estimate the energy spectrum, anisotropy axis direction, and pitch angle distribution of the high‐energy solar particles in interplanetary space. The method includes the determination of the asymptotic viewing cones of neutron monitor stations through computations of trajectories of cosmic rays in a model magnetosphere. The cosmic ray particle trajectories are determined with the GEANT‐based MAGNETOCOSMICS code using Tsyganenko 1989 and International Geomagnetic Reference Field models. Subsequent calculation of the neutron monitor responses with the model function is carried out, that represents an initial guess of the inverse problem. Derivation of the solar energetic particle characteristics is fulfilled by fitting the data of the global neutron monitor network using the Levenberg‐Marquardt method over the nine‐dimensional parameter space. The pitch angle distribution and rigidity spectrum of high‐energy protons are obtained as function of time in the course of the GLE. The angular distribution appears quite complicated. It comprises a focused beam along the interplanetary magnetic field line from the Sun and a loss‐cone feature around the opposite direction, possibly indicative of the particle transport in interplanetary magnetic field structures associated with previous coronal mass ejections.

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“…There are numerous indications on the flux-tube texture of the solar wind at 1 AU and its effect on the SEP transport (e.g., Mazur et al 2000;Borovsly 2008;Chollet & Giacalone 2008Qin & Li 2008). An intermittence of proton scattering conditions was observed in the SEP and GLE event of 1998 May 2 (GLE 56; Kocharov et al 2007a). Figure 1 shows a pattern of the contrasting level of magnetic fluctuations in the interplanetary magnetic tubes connected to the near-Sun source of high-energy protons in the famous event of 2005 January 20 (GLE 69).…”

Section: Theoretical Motivationmentioning

confidence: 97%

Solar Interacting Protons Versus Interplanetary Protons in the Core Plus Halo Model of Diffusive Shock Acceleration and Stochastic Re-Acceleration

Kocharov

Laitinen

Vainio

et al. 2015

ApJ

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With the first observations of solar γ-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the γ-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported back to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the γ-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space.

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Scanning an Interplanetary Magnetic Cloud Using High‐Energy Protons

Cited by 13 publications

References 17 publications

The Effect of Turbulence Intermittence on the Emission of Solar Energetic Particles by Coronal and Interplanetary Shocks

The Effect of Turbulence Intermittence on the Emission of Solar Energetic Particles by Coronal and Interplanetary Shocks

Analysis of the ground level enhancement on 17 May 2012 using data from the global neutron monitor network

Solar Interacting Protons Versus Interplanetary Protons in the Core Plus Halo Model of Diffusive Shock Acceleration and Stochastic Re-Acceleration

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