Cosmic Rays in Interplanetary Magnetic Fields

Топтыгин, И. Н.

doi:10.1007/978-94-009-5257-7

Cited by 198 publications

(197 citation statements)

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“…This is not critical for high-energy CR particles with velocities v CR or sound speeds c CR = dP CR /dρ CR much greater than the solar wind velocity U. These particles, just like galactic and anomalous cosmic rays, undergoing scattering at statistically distributed, magnetic inhomogeneities quasi-frozen into the supersonically expanding solar wind, thus in fact react isentropically and adiabatically (see also Toptygin 1985). This is different for low-energy, "subsonic" ions.…”

Section: Comparison With Adiabatic Coolingmentioning

confidence: 99%

Pick-up ion transport under conservation of particle invariants: how important are velocity diffusion and cooling processes?

Fahr

Fichtner

2011

A&A

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Context. The phase space transport of pick-up ions (PUIs) in the heliosphere has been studied for the cases that these particles are experiencing a second-order Fermi process, i.e. velocity diffusion, a convection with the solar wind, and adiabatic or "magnetic" cooling, i.e. cooling connected with the conservation of the magnetic moment. Aims. The study aims at a quantification of the process of "magnetic cooling" that has recently been introduced as a modification of adiabatic cooling in the presence of frozen-in magnetic fields. Methods. The isotropic PUI velocity distributions are obtained as numerical solutions of a Fokker-Planck phase space transport equation. Results. It is demonstrated that this newly discussed process is, like adiabatic energy changes, not limited to cooling but can also, depending on the shape of the distribution function, result in heating. For pure cooling with negligible velocity diffusion a v −5 velocity power law is found for magnetic cooling, thus confirming earlier analytical results. For non-negligible second-order Fermi acceleration, the tails of the distribution functions exhibit different shapes, which in special cases are also close to the prominent v −5 behaviour, which is often found in observations. Conclusions. The existence of an exact v −5 power law of PUI distribution functions can be confirmed for insignificant velocity diffusion and its approximate validity for specific choices of the velocity dependence of the diffusion coefficient.

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Section: Comparison With Adiabatic Coolingmentioning

confidence: 99%

Pick-up ion transport under conservation of particle invariants: how important are velocity diffusion and cooling processes?

Fahr

Fichtner

2011

A&A

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“…This phenomenon was originally described as transit-time damping (see Fisk 1976;Toptygin 1983;Fichtner et al 1996;le Roux & Fichtner 1999;Chalov et al 1997;Chalov 2005). Fisk & Gloeckler (2006, 2007 attempted to describe the appearance of energetic ion tails with the help of the phasespace transport equation derived by Parker (1965) as a stationary quasi-equilibrium state of a plasma interacting with compressive turbulence in thermally isolated systems.…”

Section: Introductionmentioning

confidence: 99%

“…These ion invariants cannot only profitably be used to describe the change in the dynamical properties of ions at their passage during the solar wind termination shock (see Fahr & Siewert 2010b), but are also applicable to any travelling bulk velocity jumps, when transit times τ t = ΔL/ΔU are much shorter than spatial diffusion times τ dif 3L 2 U /vΛ (see Toptygin 1983;Chalov et al 1997). Hereby ΔL is the extent of the transition region from one to the other bulk velocity, i.e.…”

Section: Introductionmentioning

confidence: 99%

Isotropic ion distribution functions triggered by consecutive solar wind bulk velocity jumps: a new equilibrium state

Fahr

Siewert

2011

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Context. Throughout the heliosphere, ion power spectra have been found in observations to exhibit suprathermal tails that follow power laws. Ion power-law spectra, though having a broad range of spectral indices 4.4 ≤ γ v ≤ 6.6, perhaps favourably seem to have velocity power indices of γ v (−5), a phenomenon that can more or less ubiquitously be found in heliospheric space plasmas. This is probably indicative of an as yet unidentified quasi-equilibrium state of collisionless space plasmas. Aims. We develop the idea that these forms of ion spectra could be produced by a continuous back-and forth-shuffling of wind convected ions in consecutive jumps from fast to slow, and vice-versa, bulk velocity regimes. Methods. The appearance of a quasi-equilibrium state due to this shuffling and re-shuffling, as we show, naturally results in ion distribution functions that are superpositions of a series of weighted Maxwellians resulting into power laws beyond a critical velocity border. Spectral intensities thereby anticorrelate with bulk velocities, but power indices depend only slightly on bulk velocity. Results. The fully developed equilibrium state is shown here, however, to be characterized by a power law with power index γ v = (−3), instead of 4.4 ≤ γ v ≤ 6.6. These latter states, which generally show up in observations, thus may characterize an off-equilibrium state as we discuss in this paper.

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“…In front of the CME bow shock, in its upstream region, the accelerated protons may excite MHD waves to form a turbulent sheath. Within the turbulent sheath, with its fluctuating magnetic field components, the energetic particle scattering mean free path, λ, is small and the diffusive shock acceleration of the particles is rapid (e.g., Toptygin 1985). Behind the bow shock, the shock downstream region is also turbulent.…”

Section: Introductionmentioning

confidence: 99%

Observation of a solar energetic particle event behind previous coronal mass ejection

Al-Sawad

Saloniemi

Laitinen

et al. 2009

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On 2001 October 19-21 the Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and HeliosphericObservatory (SOHO) observed two gradual solar energetic particle (SEP) events separated by 15 h, in association with two X1.6/2B solar flares and halo coronal mass ejections (CMEs). The observational data suggest that the second acceleration of ∼10−100 MeV protons occurred behind the first CME and the previous CME was not an obstacle for new particles to directly reach 1 AU. The proton flux anisotropy data support the idea that the particle production significantly declined in about 10 h after the shock wave started, while the prolonged temporal profile of the solar energetic particle event was due to a slow transport of previously accelerated particles in the interplanetary space. These observations call into question the view that in all gradual events high-energy particles are continuously produced at a CME bow shock as it travels from near the Sun to beyond 1 AU.

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Cosmic Rays in Interplanetary Magnetic Fields

Cited by 198 publications

References 0 publications

Pick-up ion transport under conservation of particle invariants: how important are velocity diffusion and cooling processes?

Pick-up ion transport under conservation of particle invariants: how important are velocity diffusion and cooling processes?

Isotropic ion distribution functions triggered by consecutive solar wind bulk velocity jumps: a new equilibrium state

Observation of a solar energetic particle event behind previous coronal mass ejection

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