Abstract:NASA's Parker Solar Probe mission continues to travel closer to the Sun than any prior human-made object, with an expected closest approach of <10 solar radii (<0.046 au) by 2024. On board, the Integrated Science Investigation of the Sun instrument suite makes unprecedented in situ measurements of energetic particles in the near-Sun environment. The current low level of solar activity offers a prime opportunity to measure cosmic rays closer to the Sun than ever before. We present the first observations of anom… Show more
“…For example, Rankin et al. ( 2021 ) reported a helium radial intensity gradient of in the to energy range, vs. in the inner heliosphere under similar solar cycle conditions (see their Table 1). They also determined the gradient’s magnitude for specific discrete energy intervals, as shown in Fig.…”
Section: Observations Of Anomalous Cosmic Rays Inside Of 1 Aumentioning
confidence: 97%
“…Figure adapted from Rankin et al. ( 2021 ) (Helium) and Rankin et al (in press) (Oxygen) Fig. 11 Radial gradients of PSP/ISOIS helium as a function of energy.…”
Section: Observations Of Anomalous Cosmic Rays Inside Of 1 Aumentioning
confidence: 99%
“…The first studies of cosmic rays on Parker Solar Probe were conducted by Rankin et al. ( 2021 ) and Rankin et al. ( 2022 ) who analyzed ACR helium and oxygen into 0.17 and 0.096 AU, respectively, using measurements made by the EPI-Hi sensor of the ISOIS instrument suite (McComas et al.…”
Section: Observations Of Anomalous Cosmic Rays Inside Of 1 Aumentioning
We present a review of Anomalous Cosmic Rays (ACRs), including the history of their discovery and recent insights into their acceleration and transport in the heliosphere. We focus on a few selected topics including a discussion of mechanisms of their acceleration, escape from the heliosphere, their effects on the dynamics of the heliosheath, transport in the inner heliosphere, and their solar cycle dependence. A discussion concerning their name is also presented towards the end of the review. We note that much is known about ACRs and perhaps the term Anomalous Cosmic Ray is not particularly descriptive to a non specialist. We suggest that the more-general term: “Heliospheric Energetic Particles”, which is more descriptive, for which ACRs and other energetic particle species of heliospheric origin are subsets, might be more appropriate.
“…For example, Rankin et al. ( 2021 ) reported a helium radial intensity gradient of in the to energy range, vs. in the inner heliosphere under similar solar cycle conditions (see their Table 1). They also determined the gradient’s magnitude for specific discrete energy intervals, as shown in Fig.…”
Section: Observations Of Anomalous Cosmic Rays Inside Of 1 Aumentioning
confidence: 97%
“…Figure adapted from Rankin et al. ( 2021 ) (Helium) and Rankin et al (in press) (Oxygen) Fig. 11 Radial gradients of PSP/ISOIS helium as a function of energy.…”
Section: Observations Of Anomalous Cosmic Rays Inside Of 1 Aumentioning
confidence: 99%
“…The first studies of cosmic rays on Parker Solar Probe were conducted by Rankin et al. ( 2021 ) and Rankin et al. ( 2022 ) who analyzed ACR helium and oxygen into 0.17 and 0.096 AU, respectively, using measurements made by the EPI-Hi sensor of the ISOIS instrument suite (McComas et al.…”
Section: Observations Of Anomalous Cosmic Rays Inside Of 1 Aumentioning
We present a review of Anomalous Cosmic Rays (ACRs), including the history of their discovery and recent insights into their acceleration and transport in the heliosphere. We focus on a few selected topics including a discussion of mechanisms of their acceleration, escape from the heliosphere, their effects on the dynamics of the heliosheath, transport in the inner heliosphere, and their solar cycle dependence. A discussion concerning their name is also presented towards the end of the review. We note that much is known about ACRs and perhaps the term Anomalous Cosmic Ray is not particularly descriptive to a non specialist. We suggest that the more-general term: “Heliospheric Energetic Particles”, which is more descriptive, for which ACRs and other energetic particle species of heliospheric origin are subsets, might be more appropriate.
“…It is reported that the observed GCR radial intensity gradients are much smaller than that of ACRs, which is probably due to the difference between their charge states (e.g., Cummings et al 1987;Leske et al 2005). Based on the recent observations from Parker Solar Probe, Rankin et al (2021) have studied the radial gradient of ACRs in to ∼36 solar radii (0.166 au) and reported that the radial gradients of ACR helium at energies of ∼4 to ∼45 MeV nuc −1 are larger than previous observations made further out in the heliosphere.…”
Section: Introductionmentioning
confidence: 96%
“…Energetic particles commonly observed in the heliosphere are composed of solar energetic particles (SEPs, also known as solar cosmic rays, with energies of a few keV up to several GeV, Fu et al 2019), Galactic cosmic rays (GCRs, with energies of tens of MeV nuc −1 up to 10 14 MeV nuc −1 , Heilbronn 2021), and anomalous cosmic rays (ACRs, with energies of ∼5-50 MeV nuc −1 , Rankin et al 2021).…”
Using quiet-time measurements of element oxygen within the energy range 7.3-237.9MeV nuc −1 from the ACE spacecraft at 1 au, we compare the energy spectra and intensities of anomalous and Galactic cosmic rays (ACRs and GCRs, respectively) during 1997-2020. Our analysis shows that the transition from ACR-dominated spectrum to GCR-dominated spectrum occurs at energies ∼15 to ∼35 MeV nuc −1 , and the transition energy E t is found to be well anticorrelated with varying solar activity. This is the first study of ACR-GCR transition energy dependence on the solar cycle variation. At energies below E t , the index of the power-law ACR-dominated spectrum (γ 1 ) ranges from -2.0 to -0.5, whereas the GCR-dominated spectrum has a power-law index (γ 2 ) changing from 0.3 to 0.8 at energies ranging from E t to 237.9 MeV nuc −1 . Both γ 1 and γ 2 are positively correlated with solar activity. In addition, during the solar cycle 24/25 minimum period, the peak GCR intensity observed by ACE spacecraft is about 8% above its 2009 value, setting a new record since the space age, while the peak ACR intensity is almost similar to that of the previous two solar cycles with the same pattern of solar magnetic polarity, indicating a different modulation mechanism between ACRs and GCRs.
Modelling the transport of cosmic rays (CRs) in the heliosphere represents a global challenge in the field of heliophysics, in that such a study, if it were to be performed from first principles, requires the careful modelling of both large scale heliospheric plasma quantities (such as the global structure of the heliosphere, or the heliospheric magnetic field) and small scale plasma quantities (such as various turbulence-related quantities). Here, recent advances in our understanding of the transport of galactic cosmic rays are reviewed, with an emphasis on new developments pertaining to their transport coefficients, with a special emphasis on novel theoretical and numerical simulation results, as well as the CR transport studies that employ them. Furthermore, brief reviews are given of recent progress in CR focused transport modelling, as well as the modelling of non-diffusive CR transport.
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