SYMMETRY OF THE<i>IBEX</i>RIBBON OF ENHANCED ENERGETIC NEUTRAL ATOM (ENA) FLUX

Funsten, H. O.; Bzowski, M.; Cai, D. Michael; Dayeh, M. A.; Demajistre, R.; Frisch, P. C.; Heerikhuisen, J.; Higdon, Dave; Janzen, P. H.; Larsen, B.; Livadiotis, G.; McComas, D. J.; Möbius, E.; Reese, C. Shane; Roelof, E. C.; Reisenfeld, D. B.; Schwadron, N. A.; Zirnstein, E. J.

doi:10.1088/0004-637x/799/1/68

Cited by 21 publications

(21 citation statements)

References 51 publications

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“…Nevertheless, in all cases, our results appear to be symmetric about the B−V plane. This suggests that, besides the possible influence of the latitudinal asymmetry of the SW, the hydrodynamic interaction of the SW with the LISM, centered on the trajectory of the heliosphere through the interstellar gas, is an important ordering process for the ribbon flux, as also found by Funsten et al (2015).…”

Section: Spatial Asymmetry In Simulated Ribbon Intensitysupporting

confidence: 58%

“…For the case of fast SW, we see an enhancement in flux above 1.74 keV. Because the SW speeds are uniform in latitude at the inner boundary, there is generally no bimodal structure seen in the simulated ENA intensity, even at high energies (Funsten et al 2015). This can be seen by comparing to the separated IBEX ribbon flux in Fig.…”

Section: All-sky Maps Of Ribbon Fluxmentioning

confidence: 77%

“…The ribbon at 1.74 keV is an interesting case, as it reaches a maximum between the cases of slow and fast SW, and its evolution over time may be more complicated. The ribbon symmetry at 1.74 keV appears to be a transitional energy between unimodal and bimodal flux distributions (Funsten et al 2015, Fig. 7) and is additional evidence of a mixture of structures and/or processes.…”

Section: All-sky Maps Of Ribbon Fluxmentioning

confidence: 93%

“…The distribution of ENA flux around the circular ribbon appears symmetric with unimodal symmetry at ∼1 keV and bimodal symmetry at higher energies (Funsten et al 2015). The IBEX ribbon is presumably ordered by the interstellar magnetic field; a comparison of the ribbon structure to global magneto-hydrodynamic (MHD) models of the heliosphere showed that the ribbon flux approximately aligns with directions satisfying B · r = 0 (Schwadron et al 2009a), where B is the local interstellar medium (LISM) magnetic field that is draped around the heliopause, and r is the radial line-of-sight view from the inner heliosphere and thus of IBEX.…”

Section: Introductionmentioning

confidence: 92%

“…Figure 3 can be directly compared to Fig. 9 of Funsten et al (2015), who analyzed the symmetry of the IBEX ribbon; however, note that Funsten et al plot the IBEX ribbon flux and location as a function of angle from the ribbon symmetry axis, which lies within ∼40…”

Section: Spatial Asymmetry In Simulated Ribbon Intensitymentioning

confidence: 99%

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Effects of solar wind speed on the secondary energetic neutral source of the Interstellar Boundary Explorer ribbon

Zirnstein

Funsten

Heerikhuisen

et al. 2016

A&A

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The Interstellar Boundary EXplorer (IBEX) ribbon is an intense energetic neutral atom (ENA) emission feature encircling the sky, spanning energies ≤0.5-6 keV. The ribbon may be produced by the "secondary ENA" mechanism, where ENAs emitted from a source plasma population inside the heliosphere propagate outside the heliopause, undergo two charge-exchange events, and become secondary ENAs that may be directed back toward Earth and detected by IBEX. In this scenario, the source plasma population is governed by the interaction of the solar wind (SW) with the interstellar medium and is thus sensitive to the global SW properties. Moreover, this scenario predicts that the distance to the source of secondary ENAs depends on the ENA energy and SW speed, which in turn may affect the shape of the ribbon. In this paper, we use a computational model of the heliosphere with simplified SW boundary conditions to analyze the influence of ENA energy and SW speed, independent of time and latitude, on the global spatial and geometric properties of the ribbon. We find a strong dependence of the simulated ribbon energy spectrum and spatial symmetry on SW speed and ENA energy, and only a slight dependence on ribbon geometry. Our results suggest a significant number of primary ENAs from the inner heliosheath may contribute to the pickup ion source population outside the heliopause, depending on the ENA energy and SW speed. The lack of variation in the simulated ribbon center as a function of ENA energy and SW speed, in contrast to the observations, implies that the asymmetry of the SW plays an important role in determining the position of the ribbon. Comparisons to the IBEX data also signify the ribbon's dependence on the properties of the local interstellar medium, particularly the interstellar magnetic field.

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Section: Spatial Asymmetry In Simulated Ribbon Intensitysupporting

confidence: 58%

Section: All-sky Maps Of Ribbon Fluxmentioning

confidence: 77%

Section: All-sky Maps Of Ribbon Fluxmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 92%

Section: Spatial Asymmetry In Simulated Ribbon Intensitymentioning

confidence: 99%

See 3 more Smart Citations

Effects of solar wind speed on the secondary energetic neutral source of the Interstellar Boundary Explorer ribbon

Zirnstein

Funsten

Heerikhuisen

et al. 2016

A&A

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Reconstruction of Helio-Latitudinal Structure of the Solar Wind Proton Speed and Density

et al. 2015

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The modeling of the heliosphere requires continuous three-dimensional solar wind data. The in-situ out-of-ecliptic measurements are very rare, so that other methods of solar wind detection are needed. We use the remote-sensing data of the solar wind speed from observations of interplanetary scintillation (IPS) to reconstruct spatial and temporal structures of the solar wind proton speed from 1985 to 2013. We developed a method of filling the data gaps in the IPS observations to obtain continuous and homogeneous solar wind speed records. We also present a method to retrieve the solar wind density from the solar wind speed, utilizing the invariance of the solar wind dynamic pressure and energy flux with latitude. To construct the synoptic maps of the solar wind speed we use the decomposition into spherical harmonics of each of the Carrington rotation map. To fill the gaps in time we apply the singular spectrum analysis to the time series of the coefficients of spherical harmonics. We obtained helio-latitudinal profiles of the solar wind proton speed and density over almost three recent solar cycles. The accuracy in the reconstruction is, due to computational limitations, about 20 %. The proposed methods allow us to improve the spatial and temporal resolution of the model of the solar wind parameters presented in our previous paper (Sokół et al., Solar Phys. 285, 167, 2013) and give a better insight into the time variations of the solar wind structure. Additionally, the solar wind density is reconstructed more accurately and it fits better to the in-situ measurements from Ulysses.

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Evidence for an Interstellar Dust Filament in the Outer Heliosheath

Frisch

Andersson²,

Berdyugin

et al. 2015

ApJ

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A recently discovered filament of polarized starlight that traces a coherent magnetic field is shown to have several properties that are consistent with an origin in the outer heliosheath of the heliosphere: (1) The magnetic field that provides the best fit to the polarization position angles is directed toward ℓ=357.3 • , b= 17.0 • (±11.2 • ); this direction is within 6.7 • ± 11.2 • of the observed upwind direction of the flow of interstellar neutral helium gas through the heliosphere.(2) The magnetic field is ordered; the component of the variation of the polarization position angles that can be attributed to magnetic turbulence is ±9.6 • .(3) The axis of the elongated filament can be approximated by a line that defines an angle of 80 • ± 14 • with the plane that is formed by the interstellar magnetic field vector and the vector of the inflowing neutral gas (the BV plane). We propose that this polarization feature arises from aligned interstellar dust grains in the outer heliosheath where the interstellar plasma and magnetic field are deflected around the heliosphere. This interpretation suggests that the polarization is seen where stream lines of the flow and the draped interstellar magnetic field lines are approximately parallel to each other and perpendicular to the sightline. An ordered magnetic field is required so that grain alignment is not disrupted during the interaction. The filament location is consistent with dust plumes previously predicted to form around the heliosphere. The proposed outer heliosheath location of the polarizing grains can be tested with three-dimensional models that track torques on asymmetric dust grains as they propagate through the heliosheath plasma, and using these models to evaluate grain alignment and the asymmetric extinction of the grains.

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SYMMETRY OF THEIBEXRIBBON OF ENHANCED ENERGETIC NEUTRAL ATOM (ENA) FLUX

Cited by 21 publications

References 51 publications

Effects of solar wind speed on the secondary energetic neutral source of the Interstellar Boundary Explorer ribbon

Effects of solar wind speed on the secondary energetic neutral source of the Interstellar Boundary Explorer ribbon

Reconstruction of Helio-Latitudinal Structure of the Solar Wind Proton Speed and Density

Evidence for an Interstellar Dust Filament in the Outer Heliosheath

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