Combined ∼10 eV to ∼344 MeV Particle Spectra and Pressures in the Heliosheath along the Voyager 2 Trajectory

Dialynas, K.; Galli, André; Dayeh, M. A.; Cummings, A. C.; Decker, R. B.; Fuselier, S. A.; Gkioulidou, M.; Roussos, E.; Krimigis, S. M.; Mitchell, D. G.; Richardson, J. D.; Opher, M.

doi:10.3847/2041-8213/abcaaa

Cited by 34 publications

(61 citation statements)

References 92 publications

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“…Beyond 350 AU at low latitudes, the ISM flows between the two lobes in the BU model, which leads to the lower thermal pressure and higher magnetic pressure in the tail. Both models have total pressures which agree with Voyager observations (Rankin et al 2019;Dialynas et al 2020).…”

Section: Interstellar Medium Propertiessupporting

confidence: 81%

The development of a split-tail heliosphere and the role of non-ideal processes: a comparison of the BU and Moscow models

Kornbleuth,

Opher,

Baliukin

et al. 2021

Preprint

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Global models of the heliosphere are critical tools used in the interpretation of heliospheric observations. There are several three-dimensional magnetohydrodynamic (MHD) heliospheric models that rely on different strategies and assumptions. Until now only one paper has compared global heliosphere models, but without magnetic field effects. We compare the results of two different MHD models, the BU and Moscow models. Both models use identical boundary conditions to compare how different numerical approaches and physical assumptions contribute to the heliospheric solution. Based on the different numerical treatments of discontinuities, the BU model allows for the presence of magnetic reconnection, while the Moscow model does not. Both models predict collimation of the solar outflow in the heliosheath by the solar magnetic field and produce a split-tail where the solar magnetic field confines the charged solar particles into distinct north and south columns that become lobes. In the BU model, the ISM flows between the two lobes at large distances due to MHD instabilities and reconnection. Reconnection in the BU model at the port flank affects the draping of the interstellar magnetic field in the immediate vicinity of the heliopause. Different draping in the models cause different ISM pressures, yielding different heliosheath thicknesses and boundary locations, with the largest effects at high latitudes. The BU model heliosheath is 15% thinner and the heliopause is 7% more inwards at the north pole relative to the Moscow model. These differences in the two plasma solutions may manifest themselves in energetic neutral atom measurements of the heliosphere.

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Section: Interstellar Medium Propertiessupporting

confidence: 81%

The development of a split-tail heliosphere and the role of non-ideal processes: a comparison of the BU and Moscow models

Kornbleuth,

Opher,

Baliukin

et al. 2021

Preprint

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“…The findings of [68] are supported by more recent studies, such as [72,73], but also posed a challenging question: given their surprisingly similar time profiles, why was the cosmic ray disturbance isotropic in the heliosheath but highly anisotropic in the VLISM? An interesting solution was put forth by [74], who simulated the perturbation of cosmic-rays by GMIRs in the heliosheath and employed a Vlasov-Fokker-Planck equation to allow for the transport of particles having significant anisotropy.…”

Section: Pos(icrc2021)032supporting

confidence: 67%

Nearly a Decade of Cosmic Ray Observations in the Very Local Interstellar Medium

Rankin¹

2022

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

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In 2012, the centennial year of the discovery of cosmic rays, Voyager 1 crossed the heliopause and began making the very first in-situ measurements of the surrounding interstellar medium. Joined by Voyager 2 in 2018, these twin spacecraft continue to provide critical data of cosmic rays in a surprising, previouslyunexplored plasma regime. Here, we highlight some of the discoveries and insights that have emerged from nearly a decade of cosmic ray observations in the very local interstellar medium, addressing topics such as: i) the behavior of cosmic rays at the heliopause boundary, ii) the characteristics of the low-energy spectrum (down to a few MeV/nuc), iii) the discovery of a time-varying, species-dependent anisotropy, and iv) their relationship to solar-transients that pass through the heliosphere and transmit pressure waves into the VLISM.

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“…The resulting spectra from the model are softer (harder) than the observed ones in the 0.52-8 keV energy range (beyond ∼8 keV), i.e., the ratio between the measurements and the model within that energy range is increasing (decreasing). The overall best comparison between the model and the measurements occurs for >18 keV, which is not surprising considering that (i) the PUIs from the hybrid simulation that we use (Giacalone et al 2021) agree well with the ∼28 keV measurements from LECP in V2, and (ii) the conversions of the in situ ∼28 to 540 keV LECP ions to ENAs (Dialynas et al 2020) result in ENA spectra that retain power-law slopes similar to those of the measured 5.2-55 keV ENA spectra from Cassini/INCA (Krimigis et al 2009;Dialynas et al 2020).…”

Section: Comparison Of Modeled and Observed Ena Spectramentioning

confidence: 57%

“…Spectral agreements between Cassini/ INCA ENA measurements and the Voyager ion measurements suggest that the source of ENA emissions at energies above 5.2 keV are most likely produced by charge-exchange interactions inside the HS (Dialynas et al 2013(Dialynas et al , 2017. Therefore, understanding the PUI distribution downstream of the TS is essential to study the pressure balance and acceleration mechanisms inside the HS (Dialynas et al 2019(Dialynas et al , 2020. This understanding is needed to determine the emission of ENAs from the HS because these ENAs are used to remotely sense the boundaries of our heliosphere and its interaction with the VLISM.…”

Section: Introductionmentioning

confidence: 99%

On the Energization of Pickup Ions Downstream of the Heliospheric Termination Shock by Comparing 0.52–55 keV Observed Energetic Neutral Atom Spectra to Ones Inferred from Proton Hybrid Simulations

Gkioulidou

Opher

Kornbleuth

et al. 2022

ApJL

Self Cite

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We present an unprecedented comparison of ∼0.52–55 keV energetic neutral atom (ENA) heliosheath measurements, remotely sensed by the Interstellar Boundary Explorer (IBEX) mission and the Ion and Neutral Camera (INCA) on the Cassini mission, with modeled ENAs inferred from interstellar pickup protons that have been accelerated at the termination shock, using hybrid simulations, to assess the pickup ion energetics within the heliosheath. This is the first study to use hybrid simulations that are able to accurately model the acceleration of ions to tens of keV energies, which is essential in order to model ENA fluxes in the heliosheath, covering the full energy range observed by IBEX and CASSINI/INCA. The observed ENA intensities are an average value over the time period from 2009 to the end of 2012, along the Voyager 2 (V2) trajectory. The hybrid simulations upstream of the termination shock, where V2 crossed, are constrained by observations. We report an energy-dependent discrepancy between observed and simulated ENA fluxes, with the observed ENA fluxes being persistently higher than the simulated ones. Our analysis reveals that the termination shock may not accelerate pickup ions to sufficient energies to account for the observed ENA fluxes. We, thus, suggest that the further acceleration of these pickup ions is most likely occurring within the heliosheath, via additional physical processes like turbulence or magnetic reconnection. However, the redistribution of energy inside the heliosheath remains an open question.

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Combined ∼10 eV to ∼344 MeV Particle Spectra and Pressures in the Heliosheath along the Voyager 2 Trajectory

Cited by 34 publications

References 92 publications

The development of a split-tail heliosphere and the role of non-ideal processes: a comparison of the BU and Moscow models

The development of a split-tail heliosphere and the role of non-ideal processes: a comparison of the BU and Moscow models

Nearly a Decade of Cosmic Ray Observations in the Very Local Interstellar Medium

On the Energization of Pickup Ions Downstream of the Heliospheric Termination Shock by Comparing 0.52–55 keV Observed Energetic Neutral Atom Spectra to Ones Inferred from Proton Hybrid Simulations

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