Calculation of the energetic neutral atom flux from a 3D time-dependent model heliosphere

Sternal, O.; Fichtner, H.; Scherer, K.

doi:10.1051/0004-6361:20077715

Cited by 31 publications

(22 citation statements)

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“…Recent models (e.g., Izmodenov et al 2008;Washimi et al 2011;Pogorelov et al 2013) are now fully three-dimensional and use as constraints data provided by the Voyager spacecraft as they journey through the heliosheath. Particularly relevant to our work, recent efforts have gone into modeling thetime variation in the 1 auENA flux based on realistic solar cycle parameters (e.g., Fahr & Scherer 2004;Sternal et al 2008;Siewert et al 2014;Zirnstein et al 2015). See Zirnstein et al (2015) for a comprehensive summary of the theoretical body of research on the influence of the solar cycle on the heliosphere.…”

Section: J E E ( )mentioning

confidence: 99%

Tracking the Solar Cycle Through Ibex Observations of Energetic Neutral Atom Flux Variations at the Heliospheric Poles

Reisenfeld

Bzowski

Funsten

et al. 2016

ApJ

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With seven years of Interstellar Boundary Explorer (IBEX) observations, from 2009 to 2015, we can now trace the time evolution of heliospheric energetic neutral atoms (ENAs) through over half a solar cycle. At the north and south ecliptic poles, the spacecraft attitude allows for continuous coverage of the ENA flux; thus, signal from these regions has much higher statistical accuracy and time resolution than anywhere else in the sky. By comparing the solar wind dynamic pressure measured at 1 au with the heliosheath plasma pressure derived from the observed ENA fluxes, we show that the heliosheath pressure measured at the poles correlates well with the solar cycle. The analysis requires time-shifting the ENA measurements to account for the travel time out and back from the heliosheath, which allows us to estimate the scale size of the heliosphere in the polar directions. We arrive at an estimated distance to the center of the ENA source region in the north of 220 auand in the southa distance of 190 au. We also find a good correlation between the solar cycle and the ENA energy spectra at the poles. In particular, the ENA flux for the highest IBEX energy channel (4.3 keV) is quite closely correlated with the areas of the polar coronal holes, in both the north and south, consistent with the notion that polar ENAs at this energy originate from pickup ions of the very high speed wind (∼700 km s −1 ) that emanates from polar coronal holes.

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Section: J E E ( )mentioning

confidence: 99%

Tracking the Solar Cycle Through Ibex Observations of Energetic Neutral Atom Flux Variations at the Heliospheric Poles

Reisenfeld

Bzowski

Funsten

et al. 2016

ApJ

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“…Such an asymmetry could be caused by the interstellar magnetic field distorting the TS and heliopause Lallement et al 2005). Subsequent modeling efforts had grappled with the large asymmetry observed by the Voyagers (e.g., Opher et al 2007;Pogorelov et al 2007;Heerikhuisen et al 2008;Sternal et al 2008).…”

Section: Figmentioning

confidence: 99%

IBEX—Interstellar Boundary Explorer

et al. 2009

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The Interstellar Boundary Explorer (IBEX) is a small explorer mission that launched on 19 October 2008 with the sole, focused science objective to discover the global interaction between the solar wind and the interstellar medium. IBEX is designed to achieve this objective by answering four fundamental science questions: (1) What is the global strength and structure of the termination shock, (2) How are energetic protons accelerated at the termination shock, (3) What are the global properties of the solar wind flow beyond the termination shock and in the heliotail, and (4) How does the interstellar flow interact with the heliosphere beyond the heliopause? The answers to these questions rely on energyresolved images of energetic neutral atoms (ENAs), which originate beyond the termination shock, in the inner heliosheath. To make these exploratory ENA observations IBEX carries two ultra-high sensitivity ENA cameras on a simple spinning spacecraft. IBEX's very high apogee Earth orbit was achieved using a new and significantly enhanced method for launching small satellites; this orbit allows viewing of the outer heliosphere from beyond the Earth's relatively bright magnetospheric ENA emissions. The combination of full-sky imaging and energy spectral measurements of ENAs over the range from ∼10 eV to 6 keV provides the critical information to allow us to achieve our science objective and understand this global interaction for the first time. The IBEX mission was developed to provide the first global views of the Sun's interstellar boundaries, unveiling the physics of the heliosphere's interstellar interaction, providing a deeper understanding of the heliosphere and thereby astrospheres throughout the galaxy, and creating the opportunity to make even greater unanticipated discoveries.

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“…The Bonn model was used as a basis for investigating the energetic particle distributions (Scherer & Ferreira 2005;Ferreira et al 2007aFerreira et al ,b, 2008 and the production of ENA in the heliosphere (Scherer & Fahr 2003b;Fahr & Scherer 2004;Sternal et al 2008), but none of these studies considered particles in the HSTOF energy range.…”

Section: Model Of the Heliospherementioning

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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Calculation of the energetic neutral atom flux from a 3D time-dependent model heliosphere

Cited by 31 publications

References 31 publications

Tracking the Solar Cycle Through Ibex Observations of Energetic Neutral Atom Flux Variations at the Heliospheric Poles

Tracking the Solar Cycle Through Ibex Observations of Energetic Neutral Atom Flux Variations at the Heliospheric Poles

IBEX—Interstellar Boundary Explorer

HSTOF ENA observations and energetic ion distributions in the heliosheath

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