Radiation transport of heliospheric Lyman-<i>α</i> from combined Cassini and Voyager data sets

Pryor, W. R.; Gangopadhyay, P.; Sandel, B. R.; Forrester, T.; Quémerais, Éric; Möbius, E.; Esposito, L. W.; Stewart, Ian; McClintock, W. E.; Jouchoux, A.; Colwell, Joshua; Izmodenov, Vladislav; Malama, Yu. G.; Tobiska, W. Kent; Shemansky, D. E.; Ajello, J. M.; Hansen, C. J.; Bzowski, M.

doi:10.1051/0004-6361:20078862

Cited by 42 publications

(38 citation statements)

References 45 publications

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“…The data points at larger distances better differentiate between the possible TS H densities since the slowdown becomes greater and difference between the model predictions greater. Other papers in this issue find values for the LIC H at the TS of 0.12 cm −3 (Bzowski et al 2007) and 0.085 cm −3 (Pryor et al 2008). The lower value is consistent with these results; the higher value would predict a slowdown roughly 30 km s −1 greater than observed.…”

Section: Discussion and Summarysupporting

confidence: 72%

Determining the LIC H density from the solar wind slowdown

Richardson

Liu

Wang

et al. 2008

A&A

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Context. The ionized solar wind interacts directly with the interstellar neutrals which flow into the heliosphere. These neutrals are ionized, mainly by charge exchange, then accelerated to the solar wind speed with the momentum and energy removed from the bulk flow of the solar wind. Thus, by measuring the solar wind slowdown, one can estimate the interstellar neutral density. Aims. In July 2005, Ulysses at 5 AU and Voyager 2 near 80 AU were at the same heliolatitude. We use this alignment to determine the solar wind speed decrease between these two spacecraft. Methods. Ulysses data are used as input to a 1-D MHD model which includes the effects of pickup ions. We removed a section of data contaminated by an ICME directed toward Voyager 2. Results. Comparison of the Voyager 2 speeds with the model results shows that the solar wind speed decreased by 67 km s −1 between Ulysses and Voyager 2, consistent with an interstellar neutral density at the termination shock of 0.09 cm −3 .

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Section: Discussion and Summarysupporting

confidence: 72%

Determining the LIC H density from the solar wind slowdown

Richardson

Liu

Wang

et al. 2008

A&A

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“…This method of estimating L was used by different authors (Czechowski et al 2006a(Czechowski et al , 2008Hsieh et al 2010;Krimigis et al 2009Krimigis et al , 2010. The values in Table 2 were obtained by fitting the H HSTOF ENA data using J ENA = J ion σ cx,H L eff n H with J ion (E) equal to the Z ≥ 1 ion flux measured by Voyager 1 (L eff (V1)) or Voyager 2 (L eff (V2)) and taking n H = 0.1 cm −3 (Bzowski et al 2008;Richardson et al 2008b;Pryor et al 2008). Figure 13 shows the model prediction for the effective thickness L eff and the actual thickness L as a function of direction (in the ecliptic plane, at the angle θ from the inflow direction).…”

Section: Discussionmentioning

confidence: 99%

HSTOF ENA observations and energetic ion distributions in the heliosheath

Czechowski

Hilchenbach

Hsieh

2012

A&A

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Context. Launched in 1996, HSTOF on board SOHO was the first instrument to detect the energetic neutral atoms (ENA) from the heliosheath. After mid 2003, the field of view of HSTOF was restricted to the flank sectors of the heliosheath, in which region the energetic ion distributions are still unknown. Interpretation of these data requires understanding of the energetic ion transport in the inner heliosheath. Aims. We update the HSTOF ENA hydrogen and helium spectra by adding the results from the recent (2006−2010) measurements. We calculate the energetic ion distributions in a numerical model of the heliosheath and use them as a basis for interpreting the HSTOF ENA observations, in particular those of the flank sectors. Methods. The hydrogen and helium ENA spectra were derived from the HSTOF observations of two 90 • -wide ecliptic longitude sectors around the crosswind directions. The energetic ion distributions in the heliosheath were calculated in a simple model of the heliosphere, assuming that the main acceleration occurs at the termination shock. The effects of different processes (charge-exchange loss, adiabatic acceleration, parallel diffusion and escape across the boundary) were determined with different assumptions about the boundary conditions and the transport parameters. The resulting ion distributions were used to calculate the ENA fluxes, which can be compared with the observations by HSTOF and other instruments. Results. The energetic ion density in the flank sectors of the heliosphere is lower than in the forward (upwind) sector. As a result, the contribution of the flanks of the heliosheath to the production of ENA is not directly proportional to the thickness of the heliosheath, but instead is comparable to the contribution of the forward sector, which agrees with the HSTOF data. The HSTOF ENA flux intensity is nevertheless significantly lower than the model calculations. Near the heliopause there appears a region of low energetic ion density caused by the charge-exchange and the escape losses.

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“…The contribution from the IPM between Earth and Jupiter is relatively small with roughly 200-400 R (Rayleigh, 1 R=10 6 /4π photons/cm 2 /s/sr) (e.g., Pryor et al 2008), whereas the H geocorona brightness can get as high as 30 kiloRayleigh (kR) on the dayside. During a portion of each observing orbit and hence each exposure, HST is on the Earth's dayside and the data is strongly contaminated by geocoronal emissions.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

DETECTION OF A HYDROGEN CORONA IN HST Lyα IMAGES OF EUROPA IN TRANSIT OF JUPITER

Roth

Retherford

Ivchenko

et al. 2017

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We report far-ultraviolet observations of Europa in transit of Jupiter obtained with the Space Telescope Imaging Spectrograph of the Hubble Space Telescope on six occasions between 2014 December and 2015 March. Absorption of Jupiter's bright hydrogen Lyα dayglow is detected in a region several moon radii above the limb in all observations. The observed extended absorption provides the first detection of an atomic hydrogen corona around Europa. Molecular constituents in Europa's global sputtered atmosphere are shown to be optically thin to Lyα. The observations are consistent with a radially escaping H corona with maximum densities at the surface in the range of (1.5-2.2)×10 3 cm −3 , confirming the abundances predicted by Monte Carlo simulations. In addition, we search for anomalies around the limb of Europa from absorption by localized high H 2 O abundances from active plumes. No significant local absorption features are detected. We find that an H 2 O plume with line-of-sight column density in the order of 10 16 cm −2 , as inferred by Roth et al. would not be detectable based on the statistical fluctuations of the transit measurements, and hence is not excluded or further constrained. The presence of plumes with line-of-sight column densities of >2×10 17 cm −2 can be excluded at a 3-σ level during five of our six observations.

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Radiation transport of heliospheric Lyman-α from combined Cassini and Voyager data sets

Cited by 42 publications

References 45 publications

Determining the LIC H density from the solar wind slowdown

Determining the LIC H density from the solar wind slowdown

HSTOF ENA observations and energetic ion distributions in the heliosheath

DETECTION OF A HYDROGEN CORONA IN HST Lyα IMAGES OF EUROPA IN TRANSIT OF JUPITER

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