Observations of Turbulence near Interplanetary Travelling Shocks

Kallenbach, R.; Bamert, K.; Hilchenbach, M.; Smith, C. W.

doi:10.1063/1.2032685

Cited by 3 publications

(8 citation statements)

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“…The transport of energetic particles injected by a second CME-driven shock into that region is then affected by both (1) the scattering processes undergone by the particles in the enhanced turbulence medium left behind the first CME-driven shock [e.g., Kallenbach et al, 2005;Vainio, 2009], and (2) the processes of magnetic trapping, mirroring and reflection that magnetic field compressions and discontinuities produce [Vandas et al, 1996;Hudson, 1965]. In order to efficiently confine energetic particles injected from close to the Sun by the second shock into the downstream region of the first CMEdriven shock, scattering processes are necessary in order to re-arrange the pitch-angle distribution of the particles and thus be mirrored back to the second CME-driven shock.…”

Section: Introductionmentioning

confidence: 99%

Intense solar near‐relativistic electron events at 0.3 AU

Lario

Roelof

et al. 2013

JGR Space Physics

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[1] We study the two most intense electron events observed by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft during the rising phase of solar cycle 24. Both events occurred during intense periods of solar activity when sequences of coronal mass ejections (CMEs) emanated from the Sun. The first event occurred on 4 June 2011, when two successive CMEs, spaced by 15 h, were released from the same active region. A possible interpretation for this event is that the first CME, located beyond MESSENGER's heliocentric distance (R = 0.33 AU) at the time of the second CME, acted as a magnetic barrier for solar energetic particles (SEPs) accelerated during the second CME. Elevated electron intensities at MESSENGER resulted from particle confinement between the two CME-driven shocks. This scenario is consistent with that proposed by Kallenrode and Cliver [2001a] to explain intense SEP events. The second event, observed by MESSENGER at R = 0.31 AU on 7 March 2012, belonged to a series of events generated by a single active region. A fast (>1500 km s À1 ) CME occurred 45 h before the onset of the main electron event. That implies that the prior CME-driven shock was at such a distance that particle reflection from behind that shock might have not been sufficient to account for the initial onset of sunward-directed electrons at MESSENGER, and additional mirroring and/or scattering processes closer to MESSENGER were necessary. Elevated intensities in this event are consistent with strong injection of SEPs from close to the Sun and particle reflection at some point in interplanetary space.

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Section: Introductionmentioning

confidence: 99%

Intense solar near‐relativistic electron events at 0.3 AU

Lario

Roelof

et al. 2013

JGR Space Physics

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“…Protons with the velocity of the bulk solar wind, however, have a low probability to be reflected at the cross-shock potential (e.g. Lee et al, 1996;Kallenbach et al, 2005a), while a much larger fraction of pick-up protons of interstellar origin are reflected at a quasi-perpendicular shock. These pick-up ions have a shell-like velocity distribution (Vasyliunas and Siscoe, 1976), where the shell is centered at the solar wind bulk velocity and has a radius of approximately solar wind bulk speed.…”

Section: Magnetic Micro-structurementioning

confidence: 99%

“…According to Kallenbach et al (2005a), the transmission of ions of mass-per-charge ratio R = A/Q of population (3) through the shock (excluding the effect of the conservation of the magnetic moment) is…”

Section: What Determines the Composition Of Anomalous Cosmic Rays?mentioning

confidence: 99%

“…7. The modeled factor of 40 of increase in the Alfvénic turbulence level is based on observationally supported models on the transmission of Alfvén waves through shocks (McKenzie and Westphal, 1969;Vainio and Schlickeiser, 1999;Kallenbach et al, 2005b), which predict a factor of 4 increase in wave power spectral density at a quasiperpendicular shock, and on an estimate of the Alfvén wave amplification factor (Lee, 1983;Bamert et al, 2004) due to anisotropic suprathermal ion flux observed upstream of the termination shock (Decker et al, 2008). However, turbulence generation by shock-generated wave-unstable conditions has to be considered as well Siewert, 2007, 2009).…”

Section: Evolution Of Turbulence With Heliocentric Distancementioning

confidence: 99%

“…4.1). Details of the model are described in Kallenbach et al (2005a); Kallenbach et al (2006). Here, we only give a brief overview.…”

Section: Evolution Of Suprathermal Ion Flux With Heliocentric Distancementioning

confidence: 99%

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Acceleration of the anomalous component of cosmic rays revisited

Kallenbach

Bamert

Hilchenbach

2009

Astrophys. Space Sci. Trans.

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In the years 2004 and 2007, the instruments onboard the Voyager 1 and 2 spacecraft delivered unprecedented data on the structure of the solar wind termination shock. This shock has been assumed to be responsible for the acceleration of the anomalous component of cosmic rays from a pickup ion seed population derived from the interstellar neutral gas penetrating the heliosphere. In expectation of the Voyager observations near the termination shock and in the heliosheath region, detailed models have been developed on the acceleration mechanism for the anomalous cosmic rays and on the structure of the termination shock. Here, an overview on the models on injection mechanisms into first-order Fermi acceleration, stochastic acceleration in the supersonic and subsonic solar wind, shock mediation by suprathermal ions, and on shock reformation by ions reflected at the shock is given. Comparing the results of these models to the Voyager observations, we try to synthesize an updated picture on the acceleration process of the anomalous cosmic rays.

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Particle acceleration at perpendicular shock waves: Model and observations

et al. 2006

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[1] On the basis of a recently developed nonlinear guiding center theory for the perpendicular spatial diffusion coefficient k ? used to describe the transport of energetic particles, we construct a model for diffusive particle acceleration at highly perpendicular shocks, i.e., shocks whose upstream magnetic field is almost orthogonal to the shock normal. We use k ? to investigate energetic particle anisotropy and injection energy at shocks of all obliquities, finding that at 1 AU, for example, parallel and perpendicular shocks can inject protons with equal facility. It is only at highly perpendicular shocks that very high injection energies are necessary. Similar results hold for the termination shock. Furthermore, the inclusion of self-consistent wave excitation at quasiparallel shocks in evaluating the particle acceleration timescale ensures that it is significantly smaller than that for highly perpendicular shocks at low to intermediate energies and comparable at high energies. Thus higher proton energies are achieved at quasiparallel rather than highly perpendicular interplanetary shocks within 1 AU. However, both injection energy and the acceleration timescale at highly perpendicular shocks are sensitive to assumptions about the ratio of the two-dimensional (2-D) correlation length scale to the slab correlation length scale l 2D /l k . Model proton spectra and intensity profiles accelerated by a highly perpendicular interplanetary shock are compared to an identical but parallel interplanetary shock, revealing important distinctions. Finally, we present observations of highly perpendicular interplanetary shocks that show that the absence of upstream wave activity does not inhibit particle acceleration at a perpendicular shock. The accelerated particle distributions closely resemble those expected of diffusive shock acceleration, and observed at oblique shocks, an example of which is shown.

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Observations of Turbulence near Interplanetary Travelling Shocks

Abstract: The observations on magnetic field fluctuations and suprathermal ion spectra near the shocks driven by the coronal mass ejections during the time periods of the Bastille Day 2000 event and the Halloween 2003 events are summarized.

Cited by 3 publications

References 4 publications

Intense solar near‐relativistic electron events at 0.3 AU

Intense solar near‐relativistic electron events at 0.3 AU

Acceleration of the anomalous component of cosmic rays revisited

Particle acceleration at perpendicular shock waves: Model and observations

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