Crossing the Termination Shock into the Heliosheath: Magnetic Fields

Burlaga, L. F.; Ness, N. F.; Acuña, M. H.; Lepping, R. P.; Connerney, J. E. P.; Stone, E. C.; McDonald, F. B.

doi:10.1126/science.1117542

Cited by 220 publications

(168 citation statements)

References 24 publications

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“…(5). These choices of s(θ) are in accordance with the compression ratio observations made by V1 and V2, ranging from s = 3 ± 1 (Burlaga et al 2005) to s = 2.4 (Richardson et al 2008). This transition is again shown in the top panel of Fig.…”

Section: The Modulation Modelsupporting

confidence: 59%

Modelling anomalous cosmic ray oxygen in the heliosheath

Strauss

Potgieter

Ferreira

et al. 2010

A&A

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This paper discusses a numerical modulation model to describe anomalous cosmic ray acceleration and transport in the heliosheath, the portion of the heliosphere between the termination shock and the heliopause. The model is based on the well known Parker transport equation and includes, in addition to diffusive shock acceleration at the solar wind termination shock, momentum diffusion (Fermi II, stochastic acceleration) and adiabatic heating occurring in the heliosheath together with both a latitude dependent compression ratio and injection efficiency as inferred from hydrodynamic heliospheric models. The model is applied to the study of anomalous cosmic ray oxygen, with the resulting intensities compared to recent Voyager 1 spacecraft observations in the heliosheath.Comparison shows that the model is able to very satisfactorily reproduce these observations, which includes a modulated spectral form at the termination shock and subsequent unfolding into the heliosheath. It is concluded that a combination of momentum diffusion and adiabatic heating, under certain realistic assumption of the solar wind speed in the heliosheath, form a viable re-acceleration mechanism, or continuous acceleration process, to explain the very contentious anomalous cosmic ray observations in the heliosheath.

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Section: The Modulation Modelsupporting

confidence: 59%

Modelling anomalous cosmic ray oxygen in the heliosheath

Strauss

Potgieter

Ferreira

et al. 2010

A&A

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“…The bulk speed V in the heliosheath [Richardson and Wang, 2010], observed by the plasma instrument on V2 [Bridge et al, 1977], has been twice as high as that observed by Voyager 1 (V1) when it crossed TS in December, 2004 [Stone et al, 2005;Gurnett and Kurth, 2005;Decker et al, 2005;Burlaga et al, 2005a]. These high speeds were observed from the last crossing of the TS in September 1, 2007September 1, (2007 to 2009.7.…”

Section: Introductionmentioning

confidence: 64%

Observations of the magnetic field and plasma in the heliosheath by Voyager 2 from 2007.7 to 2009.4

Burlaga¹,

Ness

Wang

et al. 2010

J. Geophys. Res.

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[1] The density and temperature profiles of the plasma measured by Voyager 2 (V2) behind the termination shock changed abruptly near 2008.6 from relatively large average values and large fluctuations during 2007.7 to 2008.6 (interval A) to relatively low average values and very small-amplitude fluctuations during 2008.6 to 2009.4 (interval B). This paper shows that the change in the magnetic field strength B(t) was less abrupt than the plasma changes, and the fluctuations of the magnetic field strength in interval B were of moderate amplitude, with indications of a quasiperiodic structure in part of the interval. The magnetic field was directed away from the sun (positive polarity) ∼ 78% ± 5% of the time in both interval A and interval B, changing in an irregular way from positive to negative polarities throughout the interval. The polarity distribution indicates that the minimum latitudinal extent of the heliospheric current sheet (HCS) was near V2 throughout the interval, consistent with the extrapolated minimum latitudes of the HCS computed from solar magnetic field observations. Thus, V2 was observing magnetic fields from the southern polar coronal hole most of the time. The distribution of B was lognormal in interval A and Gaussian interval B.

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“…[2] The 23 September issue of Science documented the Voyager 1 spacecraft's recent and remarkable crossing of the heliospheric Termination Shock (TS) [Stone et al, 2005;Decker et al, 2005;Gurnett and Kurth, 2005;Burlaga et al, 2005], the innermost structure in our heliosphere's interaction with the local interstellar medium. The TS marks the boundary where the Sun's supermagnetosonically expanding solar wind abruptly slows to become sub-magnetosonic flow.…”

Section: Introductionmentioning

confidence: 99%

“…[4] On 16 December 2004, the Voyager 1 spacecraft crossed the termination shock at a heliocentric distance of $94 AU, directly measuring the expected compression of magnetic field [Burlaga et al, 2005] inferring strong slowing of the solar wind [Decker et al, 2005], and observing the end of upstream plasma oscillations [Gurnett and Kurth, 2005]. The shock was also a steady source of lower energy energetic protons [Stone et al, 2005] and the lowest energy electrons and ions exhibited roughly ten-fold increases across the shock, with smaller increases at higher energies [Decker et al, 2005].…”

Section: Introductionmentioning

confidence: 99%

An explanation of the Voyager paradox: Particle acceleration at a blunt termination shock

McComas¹,

Schwadron²

2006

Geophysical Research Letters

143

119

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[1] Voyager 1 recently crossed the termination shock at the edge of our heliosphere. In contrast to the expectations of essentially all prior models, however, Voyager 1 did not observe the source of Anomalous Cosmic Rays (ACRs) as had been widely anticipated. We show here that the dearth of higher energy particles near the nose of the heliosphere is a natural consequence of the magnetic geometry in the region ahead of a flattened shock. Particle energization happens primarily back along the flanks of the shock where the injection energy is lower and where the magnetic field has had progressively longer connection times to accelerate particles. In addition to explaining the most baffling aspects of the Voyager 1 observations, this paradigm makes explicit predictions about what should be observed when Voyager 2 reaches the termination shock, significantly further back from its nose.

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Crossing the Termination Shock into the Heliosheath: Magnetic Fields

Cited by 220 publications

References 24 publications

Modelling anomalous cosmic ray oxygen in the heliosheath

Modelling anomalous cosmic ray oxygen in the heliosheath

Observations of the magnetic field and plasma in the heliosheath by Voyager 2 from 2007.7 to 2009.4

An explanation of the Voyager paradox: Particle acceleration at a blunt termination shock

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