Comic ray flux anisotropies caused by astrospheres

Scherer, K.; Strauss, R. D.; Ferreira, S. E. S.; Fichtner, H.

doi:10.1016/j.astropartphys.2016.06.003

Cited by 6 publications

(7 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The discussion given above shows that λ Cephei-like astrospheres with magnetic fields have a complicated structure, indicating that studies of cosmic-ray propagation within and through such a structure require further investigations (Scherer et al 2015b(Scherer et al , 2016a.…”

Section: Flow Propertiesmentioning

confidence: 99%

“…We have now improved the modeling by including both a Parker-like stellar wind magnetic field at the inner boundary and an interstellar magnetic field beyond the AP. While a few aspects, including a comparison to observations of astrospheres around cool stars (such as the Sun), can be found in Scherer et al (2016a), here we continue the discussion using an MHD model of λ Cephei and compare it with heliospherelike astrospheres and a wind bubble.…”

mentioning

confidence: 98%

See 1 more Smart Citation

MHD-shock structures of astrospheres: λ Cephei -like astrospheres

Scherer

Baalmann

Fichtner

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The interpretation of recent observations of bow shocks around O-stars and the creation of corresponding models require a detailed understanding of the associated (magneto-)hydrodynamic structures. We base our study on three-dimensional numerical (magneto-)hydrodynamical models, which are analyzed using the dynamically relevant parameters, in particular, the (magneto)sonic Mach numbers. The analytic Rankine-Hugoniot relation for HD and MHD are compared with those obtained by the numerical model. In that context we also show that the only distance which can be approximately determined is that of the termination shock, if it is a hydrodynamical shock. For MHD shocks the stagnation point does not, in general, lie on the inflow line, which is the line parallel to the inflow vector and passing through the star. Thus an estimate via the Bernoulli equation as in the HD case is, in general, not possible. We also show that in O-star astrospheres, distinct regions exist in which the fast, slow, Alfvénic, and sonic Mach numbers become lower than one, implying sub-slow magnetosonic as well as sub-fast and sub-sonic flows. Nevertheless, the analytic MHD Rankine Hugoniot relations can be used for further studies of turbulence and cosmic ray modulation.

show abstract

Section: Flow Propertiesmentioning

confidence: 99%

mentioning

confidence: 98%

MHD-shock structures of astrospheres: λ Cephei -like astrospheres

Scherer

Baalmann

Fichtner

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Scattering processes with stochastic magnetic instabilities produce perturbations in the arrival directions within the scattering mean free path. Such perturbations may be observed as stochastic localized excess or deficit regions (Giacinti and Sigl, 2012;Biermann et al, 2013;Ahlers, 2014;Ahlers and Mertsch, 2015;Ló pez-Barquero et al, 2016a;Harding et al, 2016;Scherer et al, 2016).…”

Section: Anisotropy Of Local Cosmic Raysmentioning

confidence: 99%

Astrophysical neutrinos and cosmic rays observed by IceCube

Aartsen¹,

Ackermann²,

Adams³

et al. 2018

Advances in Space Research

View full text Add to dashboard Cite

The core mission of the IceCube neutrino observatory is to study the origin and propagation of cosmic rays. IceCube, with its surface component IceTop, observes multiple signatures to accomplish this mission. Most important are the astrophysical neutrinos that are produced in interactions of cosmic rays, close to their sources and in interstellar space. IceCube is the first instrument that measures the properties of this astrophysical neutrino flux and constrains its origin. In addition, the spectrum, composition, and anisotropy of the local cosmic-ray flux are obtained from measurements of atmospheric muons and showers. Here we provide an overview of recent findings from the analysis of IceCube data, and their implications to our understanding of cosmic rays.

show abstract

“…λ Cephei is the brightest runaway O star in the sky (Scherer et al 2016b), and therefore is the object most likely to have the most visible astrosphere. The astrosphere of λ Cephei has been proposed as a sink for cosmic rays (Scherer et al 2015), which has been examined further by Scherer et al (2016c).…”

Section: Introductionmentioning

confidence: 99%

Skymaps of observables of three-dimensional magnetohydrodynamic astrosphere models

Baalmann

Scherer

Fichtner

et al. 2020

A&A

Self Cite

View full text Add to dashboard Cite

Context. Three-dimensional models of astrospheres have recently become of interest. However, comparisons between these models and observations are non-trivial because of the two-dimensional nature of observations. Aims. By projecting selected physical values of three-dimensional models of astrospheres onto the surface of a sphere that is centred on a virtual all-sky observer, these models can be compared to observational data in different observables: the column density, bremsstrahlung flux, rotation measure, Hα flux, and synchrotron or cyclotron flux. Methods. Projections were calculated by rotating and moving the astrosphere model to the desired position and orientation and by then computing the value of a given patch on the sphere by a modified line-of-sight integration. Contributions to the selected observable made by all model cells that are connected to the patch by the line of sight in question were taken into account.Results. When the model produces a bow shock, a distinct parabolic structure produced by the outer astrosheath can be seen in every observable of the projection, the exact shape depending on the orientations of the line of sight and the stellar motion. Of all four examined astrosphere models, only that of λ Cephei shows fluxes that are higher than current observational thresholds. This is due to the strong stellar wind and interstellar inflow of the λ Cephei model.

show abstract

Comic ray flux anisotropies caused by astrospheres

Cited by 6 publications

References 44 publications

MHD-shock structures of astrospheres: λ Cephei -like astrospheres

MHD-shock structures of astrospheres: λ Cephei -like astrospheres

Astrophysical neutrinos and cosmic rays observed by IceCube

Skymaps of observables of three-dimensional magnetohydrodynamic astrosphere models

Contact Info

Product

Resources

About