Galactic Cosmic Rays Throughout the Heliosphere and in the Very Local Interstellar Medium

Rankin, J. S.; Bindi, V.; Bykov, A. M.; Cummings, A. C.; Torre, S. Della; Florinski, V.; Heber, B.; Potgieter, M. S.; Stone, E. C.; Zhang, Ming

doi:10.1007/s11214-022-00912-4

Cited by 22 publications

(9 citation statements)

References 249 publications

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“…In general, measurements by the two Voyagers reveal that the VLISM immediately surrounding the heliosphere is strongly influenced by the Sun and heliospheric processes. Such processes manifest through a variety of propagating transient phenomena measured locally at each spacecraft, including: cosmic-ray intensity enhancements (Gurnett et al 2015(Gurnett et al , 2021bRankin et al 2019bRankin et al , 2020; electron plasma oscillations (Gurnett et al 2013(Gurnett et al , 2021aGurnett & Kurth 2019;Ocker et al 2021); weak, laminar shocks and "pressure front" waves (Burlaga & Ness 2016;Kim et al 2017;Richardson et al 2017;Burlaga et al 2019b;Burlaga et al 2021, Burlaga et al 2022; and long-duration, pitchangle dependent episodes of cosmic-ray intensity depletion, commonly referred to as "cosmic ray anisotropies" (Krimigis et al 2013;Rankin et al 2019bRankin et al , 2020Nikoukar et al 2022;Rankin et al 2022). The perturbations in the magnetic field seen in Figures 1 and 2 are characterized by sudden enhancements, followed by gradual decays, which deviate from nominal values; those with cosmic ray and electron plasma precursors are typically classified as shocks ("sh"), while those without such events are often referred to as waves, or pressure fronts ("pf").…”

Section: Observations and Simulationmentioning

confidence: 99%

Unified Picture of the Local Interstellar Magnetic Field from Voyager and IBEX

Rankin

McComas

Zirnstein

et al. 2023

ApJL

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Prior to the Voyagers’ heliopause crossings, models and the community expected the magnetic field to show major rotations across the boundary. Surprisingly, the field showed no significant change in direction from the heliospheric Parker Spiral at either Voyager location. Meanwhile, a major result from the IBEX mission is the derived magnitude and direction of the interstellar field far from the Sun (∼1000 au) beyond the influence of the heliosphere. Using a self-consistent model fit to IBEX ribbon data, Zirnstein et al. reported that this “pristine” local interstellar magnetic field has a magnitude of 0.293 nT and direction of 227° in ecliptic longitude and 34.°6 in ecliptic latitude. These values differ by 27% (51%) and 44° (12°) from what Voyager 1 (2) currently observes (as of ∼2022.75). While differences are to be expected as the field undrapes away from the heliosphere, the global structure of the draping across hundreds of astronimcal units has not been reconciled. This leads to several questions: How are these distinct sets of observations reconcilable? What is the interstellar magnetic field’s large-scale structure? How far out would a future mission need to go to sample the unperturbed field? Here, we show that if realistic errors are included for the difficult-to-calibrate radial field component, the measured transverse field is consistent with that predicted by IBEX, allowing us to answer these questions through a unified picture of the behavior of the local interstellar magnetic field from its draping around the heliopause to its unfolding into the pristine interstellar medium.

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Section: Observations and Simulationmentioning

confidence: 99%

Unified Picture of the Local Interstellar Magnetic Field from Voyager and IBEX

Rankin

McComas

Zirnstein

et al. 2023

ApJL

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“…The goal is to use IceCube and HAWC observatories in concert and ensure that proper models of the heliosphere are developed to study CR particles propagation in the ISM. Future experiments such as SWGO in the southern hemisphere and LHAASO in the northern hemisphere, will guarantee the availability of high quality CR data to perform this study in the next decade 112 .…”

Section: Discussionmentioning

confidence: 99%

Using TeV Cosmic Rays to probe the Heliosphere's Boundary with the Local Interstellar Medium

Desiati¹,

Díaz-Vélez²,

Giacinti³

et al. 2022

Preprint

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The heliosphere is the magnetic structure formed by the Sun's atmosphere extending into the local interstellar medium (ISM). The heliopause, the boundary separating the heliosphere from the ISM, is a still largely unexplored region of space. Even though the Voyager spacecraft officially entered the local ISM in 2012 (V1) and 2018 (V2) and are delivering data on the outer space environment, they are just two points piercing a vast region of space at specific times. The heliospheric boundary regulates the penetration of MeV-GeV galactic cosmic rays (CR) into the inner heliosphere, where the solar system is located. Interstellar keV neutral atoms are crucial to the outer heliosphere since they can penetrate unperturbed and transfer energy into the solar wind. Missions such as NASA's Interstellar Boundary EXplorer (IBEX) and Cassini are designed to detect neutral atoms and monitor charge exchange processes at the heliospheric boundary. The heliosphere does not modulate the intensity of TeV CR particles coming from the ISM, but it does influence their arrival direction distribution. Ground-based CR observatories have provided statistically accurate maps of CR anisotropy as a function of energy over the last couple of decades. Combining such observations to produce all-sky coverage makes it possible to investigate the impact that the heliosphere has on TeV CR particles. We can numerically calculate the pristine TeV CR pitch angle distribution in the local ISM using state-of-the-art heliosphere models. Only with the heliospheric influence subtracted is it possible to use TeV CR observations to infer propagation properties and the characteristics of magnetic turbulence in the ISM. Numerical calculations of CR particle trajectories through heliospheric models, therefore, provide a complementary tool to probe into the global properties of the boundary region, such as its size, length, and the scale of the local interstellar magnetic field draping around the heliosphere. A program boosting heliospheric modeling with emphasis on the boundary region, and promoting combined CR experimental data analyses from multiple ground-based experiments, will benefit CR astrophysics and, in reverse, will provide additional data and complementary tools to explore the interaction between the heliosphere and the local ISM.

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“…FDs are usually identified as a temporary and rapid depression in the GCR intensity followed by a comparatively slower recovery phase, typically lasting for a few days. More contents about the GCR transport theory are summarized in, e.g., Kóta (2013), Engelbrecht et al (2022), and Rankin et al (2022).…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Comparison of Various Galactic Cosmic-Ray Models to the State-of-the-art Particle and Radiation Measurements

Liu,

Guo,

Wang

et al. 2024

ApJS

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Galactic cosmic rays (GCRs) are the slowly varying background energetic particles that originate outside the solar system, are modulated by the heliospheric magnetic field, and pose ongoing radiation hazards to deep space exploration missions. To assess the potential radiation risk, various models have been developed to predict the GCR flux near Earth based on propagation theories and/or empirical functions. It is essential to benchmark these models by validating against the state-of-the-art measurements. In this work, a comprehensive model–observation comparison of the energy-dependent particle flux has been performed, by combining five typical GCR models and observational data from the Cosmic Ray Isotope Spectrometer on board the Advanced Composition Explorer spacecraft at relatively lower energies and data from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics and Alpha Magnetic Spectrometer at higher energies. The analysis shows that, out of the five models investigated in this study, the optimal model, characterized by minimal relative difference or reduced chi-square divergence from measurements, depends on the particle type, energy range, and epoch of interest. Furthermore, a silicon slab is applied to compute the absorbed dose rate using conversion factors applied to GCR model outputs, and the results are compared to measurements from the Cosmic Ray Telescope for the Effects of Radiation. The comparisons in this paper have implications for the strengths and limitations of individual GCR models, advance our comprehension of the underlying GCR transport mechanisms, and also have strong application aspects for mitigating space radiation risks.

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Galactic Cosmic Rays Throughout the Heliosphere and in the Very Local Interstellar Medium

Cited by 22 publications

References 249 publications

Unified Picture of the Local Interstellar Magnetic Field from Voyager and IBEX

Unified Picture of the Local Interstellar Magnetic Field from Voyager and IBEX

Using TeV Cosmic Rays to probe the Heliosphere's Boundary with the Local Interstellar Medium

A Comprehensive Comparison of Various Galactic Cosmic-Ray Models to the State-of-the-art Particle and Radiation Measurements

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