Termination shock particle spectral features

Cummings, A. C.; Stone, E. C.; McDonald, F. B.; Heikkila, B. C.; Lal, N.; Webber, W. R.

doi:10.1063/1.2359310

Cited by 15 publications

(8 citation statements)

References 11 publications

(17 reference statements)

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“…We find these features to be robust and not to be very sensitive to the precise values of the parameters used. Both of these downstream behaviors, the increase in intensity downstream and the features in the spectra are similar to those observed in the Voyager 1 data [11].…”

Section: An Analytic Modelsupporting

confidence: 76%

Particle Acceleration at Shocks: Effects of Spatial Variations Along the Shock Face

Jokipii¹,

Kóta²,

Li³

et al. 2008

AIP Conference Proceedings

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We consider the acceleration of charged particles and anomalous cosmic rays (ACR) at propagating shocks and especially at the heliospheric termination shock, when upstream variations cause spatial variations along the shock face, or, alternatively, if the global spatial geometry causes the shock to vary. Here we present the results a new analytic solution for the case of a shock in which the injection low-energy particles varies with position along the shock face. We find that, downstream of the shock, positive spatial gradients together with modidation-like and midtiplepower-law spectral features are naturally produced by plausible spatial variations at the shock. Similar effects also residt from large-scale or global spatial structure. These various effects show promising qualitative agreement with observations at and near the heliospheric termination shock, suggesting that they may play an important role.

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Section: An Analytic Modelsupporting

confidence: 76%

Particle Acceleration at Shocks: Effects of Spatial Variations Along the Shock Face

Jokipii¹,

Kóta²,

Li³

et al. 2008

AIP Conference Proceedings

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“…At both spacecraft the spectral peak shifts from ∼6.5 MeV/n at solar minimum to 11 MeV/n at solar maximum to 25 MeV/n immediately after the transition (Figures 3c and 3d). It remains at this higher energy at V1 but over time it gradually merges with the lower energy termination shock particle population [ Cummings et al , 2006; Hill et al , 2006]. At V2 there is no shift in the spectral peak from 2001.85 to 2006.21 despite the x25 increase in 15.5 MeV/n He + .…”

Section: Observationsmentioning

confidence: 99%

Anomalous cosmic rays in the distant heliosphere and the reversal of the Sun's magnetic polarity in Cycle 23

McDonald

Stone

Cummings

et al. 2007

Geophysical Research Letters

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[1] Beginning in early June 2001 and extending over a $3 month period the Cosmic Ray Subsystem (CRS) experiment on Voyager 1 (80.3 AU, 34°N) observed a rapid transition in the energy of the peak intensity of anomalous cosmic ray (ACR) He from $11 MeV/n to $25 MeV/n. One month later there began a similar spectral shift at Voyager 2 (64.7 AU, 24°S). When these ACR transition times are extrapolated back from the estimated location of the heliospheric termination shock (TS) to the Sun ($1 year) there is reasonable agreement with the range of times obtained for the polarity reversal of the interplanetary magnetic field (IPB) in the northern hemisphere near the Sun and the later reversal in the south. We interpret these changes in the ACR spectra as giving a global view of the interplanetary field reversal at the TS and confirmation of the important role of the TS in controlling the ACRs. Citation:

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“…3) provide additional insight on the evolution of the ACR and TSP populations. The changes in the H spectra over this period, have been discussed in detail by Cummings et al (14). The lowest energy protons experience a large increase at the TS (1,3) and by early 2006 display several different spectral slopes with increasing energy.…”

Section: Observationsmentioning

confidence: 99%

Voyager observations of galactic and anomalous cosmic rays in the helioshealth

McDonald¹,

Webber²,

Stone³

et al. 2006

AIP Conference Proceedings

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Abstract. Anomalous cosmic rays display large temporal variations at the time and location where Voyager 1 (V1) crossed the heliospheric termination shock (2004.86) (94AU, 34°N). On a short time scale (3 months) there was a large decrease produced by a series of merged interaction regions (MIR), the first of which was associated with the intense Oct./Nov. 2003 solar events. On a longer time scale there is a remarkable correlation between changes in the galactic cosmic ray (GCR) intensity and those of 10-56 MeV/n ACR He and 30-56 MeV H extending over a 4.3 year period with the GCRs exhibiting their expected behavior over this part of the 11 and 22 year solar activity and heliomagnetic cycle. The relative changes in the ACR and GCR are the same for both the short term and long term variations. The comparative V1/V2 ACR and GCR spectra in the foreshock and heliosheath indicate that at this time most of the higher energy ACRs are not being accelerated near V1 but must have their source region elsewhere -possibly near the equatorial region of the TS as was suggested in our first paper on the TS crossing (1).

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Termination shock particle spectral features

Cited by 15 publications

References 11 publications

Particle Acceleration at Shocks: Effects of Spatial Variations Along the Shock Face

Particle Acceleration at Shocks: Effects of Spatial Variations Along the Shock Face

Anomalous cosmic rays in the distant heliosphere and the reversal of the Sun's magnetic polarity in Cycle 23

Voyager observations of galactic and anomalous cosmic rays in the helioshealth

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