Influence of Earth-directed Coronal Mass Ejections on the Sun’s Shadow Observed by the Tibet-III Air Shower Array

Amenomori, M.; Bi, X. J.; Chen, D.; Chen, T. L.; Chen, W. Y.; Cui, S. W.; Danzengluobu,; Ding, L. K.; Feng, C.; Feng, Z.; Gou, Q. B.; Guo, Y. Q.; He, H. H.; He, Ze; Hibino, K.; Hotta, N.; Hu, Haibing; Huang, J.; Jia, H. Y.; Jiang, L.; Kajino, F.; Kasahara, K.; Katayose, Y.; Kato, C.; Kawata, K.; Kozai, M.; Labaciren,; Le, G. M.; Li, A. F.; Li, H. J.; Li, W. J.; Liu, C.; Liu, J. S.; Liu, M. Y.; Lü, H.; Meng, X. R.; Miyazaki, Tetsuya; Munakata, K.; Nakajima, T.; Nakamura, Yuya; Nanjo, H.; Nakamura, Masaki; Niwa, T.; Ohnishi, M.; Ohta, I.; Ozawa, S.; Qian, X. L.; Qu, X. B.; Saito, Takao; Saito, T.; Sakata, M.; Sako, T. K.; Shao, J.; Shibata, M.; Shirai, T.; Sugimoto, H.; Takita, M.; Tan, Y. H.; Tateyama, N.; Torii, Shoji; Tsuchiya, H.; Udo, S.; Wang, H.; Wu, H. R.; Xue, L.; Yamamoto, Y.; Yamauchi, K.; Yang, Zhongwei; Yuan, A. F.; Zhai, L. M.; Zhang, H. M.; Zhang, J. L.; Zhang, X. Y.; Zhang, Y.; Zhang, Yi; Zhang, Ying; Zhaxisangzhu,; Zhou, X. X.

doi:10.3847/1538-4357/aac2e6

Cited by 9 publications

(7 citation statements)

References 33 publications

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Section: Discussionmentioning

confidence: 99%

“…Studies as we present here, without including detector effects, are still desirable, as this is the best way to find effects that arise from the magnetic field. The influence of coronal mass ejections (CMEs) on the cosmic-ray Sun shadow seen by different experiments is also something that can be studied, as has been shown in [43]. Toward a complete model of transport and interaction Furthermore, adding particle interactions in the solar corona and in the Earth's atmosphere to the simulations will be another step that would increase our understanding of the phenomenon of cosmic-ray shadowing.…”

Section: Discussionmentioning

confidence: 99%

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Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

Tjus

Desiati

Döpper

et al. 2020

A&A

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The cosmic-ray Sun shadow, which is caused by high-energy charged cosmic rays being blocked and deflected by the Sun and its magnetic field, has been observed by various experiments such as Argo-YBJ, HAWC, Tibet, and IceCube. Most notably, the shadow's size and depth was recently shown to correlate with the 11-year solar cycle. The interpretation of such measurements, which help to bridge the gap between solar physics and high-energy particle astrophysics, requires a solid theoretical understanding of cosmic-ray propagation in the coronal magnetic field. It is the aim of this paper to establish theoretical predictions for the cosmic-ray Sun shadow in order to identify observables that can be used to study this link in more detail.To determine the cosmic-ray Sun shadow, we numerically compute trajectories of charged cosmic rays in the energy range of 5 to 316 TeV for five different mass numbers. We present and analyse the resulting shadow images for protons and iron, as well as for typically measured cosmic-ray compositions. We confirm the observationally established correlation between the magnitude of the shadowing effect and both the mean sunspot number and the polarity of the magnetic field during the solar cycle. We also show that during low solar activity, the Sun's shadow behaves similarly to that of a dipole, for which we find a non-monotonous dependence on energy. In particular, the shadow can become significantly more pronounced than the geometrical disk expected for a totally unmagnetized Sun. For times of high solar activity, we instead predict the shadow to depend monotonously on energy, and to be generally weaker than the geometrical shadow for all tested energies. These effects should become visible in energy-resolved measurements of the Sun shadow, and may in the future become an independent measure for the level of disorder in the solar magnetic field.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

Tjus

Desiati

Döpper

et al. 2020

A&A

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“…Compared to the Moon shadow observed by HAWC, the Sun shadow at low energies (∼1 TeV) is less significant due to the effect of the solar magnetic fields [64,65]. The Sun shadow is more pronounced at higher energies, at which the cosmic rays are less deflected by the coronal and interplanetary magnetic fields [71][72][73]. The evolution of the shadow size with energy is also an illustration of the angular resolution of the detector to cosmic rays, which has been modeled and verified in Refs.…”

Section: Sky Maps and Background Estimationmentioning

confidence: 97%

“…If the gamma-ray spectrum measured in the last solar minimum continues into the TeV range without a cutoff during the minimum of cycle 25, HAWC will be able to detect it with high significance. Long term monitoring from HAWC on the Sun shadow will also allow us to understand the effect of solar magnetic fields on TeV cosmic rays [71][72][73]. Finally, hadronic cosmic rays interacting in the solar atmosphere will also produce solar atmospheric neutrinos [48][49][50], which are being searched for in IceCube [82].…”

Section: B Implications and Future Workmentioning

confidence: 99%

First HAWC observations of the Sun constrain steady TeV gamma-ray emission

Albert¹,

Alfaro²,

Álvarez³

et al. 2018

Phys. Rev. D

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Steady gamma-ray emission up to at least 200 GeV has been detected from the solar disk in the Fermi-LAT data, with the brightest, hardest emission occurring during solar minimum. The likely cause is hadronic cosmic rays undergoing collisions in the Sun's atmosphere after being redirected from ingoing to outgoing in magnetic fields, though the exact mechanism is not understood. An important new test of the gamma-ray production mechanism will follow from observations at higher energies. Only the High Altitude Water Cherenkov (HAWC) Observatory has the required sensitivity

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“…In 2013, the Tibet AS-γ Collaboration compared coronal magnetic field models using the cosmic-ray Sun shadow at a median primary cosmic-ray energy of ∼10 TeV [8]. Later, they also studied the influence of solar coronal mass ejections (CMEs) on the cosmic-ray Sun shadow at energies of ∼3 TeV [9] and concluded that Earth-directed CMEs (ECMEs) affect the cosmic-ray Sun shadow at these energies. The influence of the solar magnetic field on the cosmic-ray Sun shadow has been studied by several other experiments, like Milagro, ARGO-YBJ, and HAWC, as well [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Measurements of the time-dependent cosmic-ray Sun shadow with seven years of IceCube data: Comparison with the Solar cycle and magnetic field models

Aartsen¹,

Abbasi²,

Ackermann³

et al. 2021

Phys. Rev. D

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Observations of the time-dependent cosmic-ray Sun shadow have been proven as a valuable diagnostic for the assessment of solar magnetic field models. In this paper, seven years of IceCube data are compared to solar activity and solar magnetic field models. A quantitative comparison of solar magnetic field models with IceCube data on the event rate level is performed for the first time. Additionally, a first energydependent analysis is presented and compared to recent predictions. We use seven years of IceCube data for the moon and the Sun and compare them to simulations on data rate level. The simulations are performed for the geometrical shadow hypothesis for the moon and the Sun and for a cosmic-ray propagation model governed by the solar magnetic field for the case of the Sun. We find that a linearly decreasing relationship between Sun shadow strength and solar activity is preferred over a constant relationship at the 6.4σ level. We test two commonly used models of the coronal magnetic field, both combined with a Parker spiral, by modeling cosmic-ray propagation in the solar magnetic field. Both models predict a weakening of the shadow in times of high solar activity as it is also visible in the data. We find tensions with the data on the order of 3σ for both models, assuming only statistical uncertainties. The magnetic field model CSSS fits the data slightly better than the PFSS model. This is generally consistent with what is found previously by the Tibet AS-γ Experiment; a deviation of the data from the two models is, however, not significant at this point. Regarding the energy dependence of the Sun shadow, we find indications that the shadowing effect increases with energy during times of high solar activity, in agreement with theoretical predictions.

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Influence of Earth-directed Coronal Mass Ejections on the Sun’s Shadow Observed by the Tibet-III Air Shower Array

Cited by 9 publications

References 33 publications

Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

First HAWC observations of the Sun constrain steady TeV gamma-ray emission

Measurements of the time-dependent cosmic-ray Sun shadow with seven years of IceCube data: Comparison with the Solar cycle and magnetic field models

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