Simulating gamma-ray production from cosmic rays interacting with the solar atmosphere in the presence of coronal magnetic fields

Li, Zhe; Ng, Kenny C. Y.; Chen, Songzhan; Nan, Yuncheng; He, Huihai

doi:10.48550/arxiv.2009.03888

Cited by 9 publications

(14 citation statements)

References 57 publications

(102 reference statements)

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“…Notably the fall and rise of the solar disk γ-ray flux is symmetric around the solar maximum, with no evidence of a deviation based on the polarity of the heliospheric magnetic field. This trend matches previous observational data [20], but runs contrary to modeling efforts aimed at understanding solar γ-ray emission [18].…”

Section: Discussionsupporting

confidence: 81%

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First Observations of Solar Disk Gamma Rays over a Full Solar Cycle

Linden¹,

Beacom²,

Peter³

et al. 2020

Preprint

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The solar disk is among the brightest γ-ray sources in the sky. It is also among the most mysterious. No existing model fully explains the luminosity, spectrum, time variability, and morphology of its emission. We perform the first analysis of solar-disk γ-rays over a full 11-year solar cycle, utilizing a powerful new method to differentiate solar signals from astrophysical backgrounds. We produce: (i) a robustly measured spectrum from 100 MeV to 100 GeV, reaching a precision of several percent in the 1-10 GeV range, (ii) new results on the anti-correlation between solar activity and γ-ray emission, (iii) strong constraints on short-timescale variability, ranging from hours to years, and (iv) new detections of the equatorial and polar morphologies of high-energy γ-rays. Intriguingly, we find no significant energy dependence in the time variability of solar-disk emission, indicating that strong magnetic-field effects close to the solar surface, rather than modulation throughout the heliosphere, must primarily control the flux and morphology of solar-disk emission.

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Section: Discussionsupporting

confidence: 81%

“…Detailed simulations of cosmic-ray interactions within the solar atmosphere (including, e.g., solar composition, secondary production, coronal magnetic fields, etc.) have recently been completed by several groups [17,18].…”

Section: Introductionmentioning

confidence: 99%

First Observations of Solar Disk Gamma Rays over a Full Solar Cycle

Linden¹,

Beacom²,

Peter³

et al. 2020

Preprint

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“…The HAWC observatory recently reported a gamma-ray signal from the quiet Sun around 1 TeV and most of it correlates with the solar minimum data 98 . These are the disk component produced by CR hadrons interacting with the solar surface [99][100][101][102][103][104][105][106][107] and the spatially extended Inverse-Compton (IC) component produced by CR electrons and positrons on the solar photons 108,109 . The flux of both gamma-ray components is expected to change over the solar cycle due to the modulation of the CRs in the heliosphere, and it is expected to be anti-correlated with the solar activity.…”

Section: Cr Anisotropy and Magnetic Field Turbulence In The Ismmentioning

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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“…Before its detection [42], the disk emission was briefly mentioned by [25] in 1989, while in 1991 the work in [48] contains the first calculation of the gamma-ray emission from pion-decay by CR proton cascades in the solar atmosphere, and in 1997 an upper limit with EGRET data was obtained by [51]. Further studies of this component followed also recently both from the theoretical point of view [11,20,26,31,35,40] and from the observational one ( [2,9,10,32,33,39,50,52]). Regarding the solar gamma-ray leptonic component, in 2006 we [41] predicted the existence of an extended inverse Compton (IC) emission from scattering by Galactic CR electrons and positrons (all-electrons thereafter) on solar photons.…”

Section: Introductionmentioning

confidence: 99%

StellarICS: Inverse Compton Emission from the Quiet Sun and Stars from keV to TeV

Orlando,

Strong

2020

Preprint

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The study of the quiet Sun in gamma rays started over a decade ago, and rapidly gained a wide interest. Gamma rays from the quiet Sun are produced by Galactic cosmic rays (CRs) interacting with its surface (disk component) and with its photon field (spatially extended inverse-Compton component, IC). The latter component is maximum close to the Sun and it is above the background even at large angular distances, extending over the whole sky. First detected with EGRET, it is studied now with Fermi-LAT with high statistical significance.Observations of the IC component allow us to obtain information on CR electrons and positrons close to the Sun and in the heliosphere for the various periods of solar activity and polarity. They allow to learn about CR interactions and propagation close to stars, in the heliosphere and on the solar surface, and to understand the Sun itself, its environment, and its activity. Analyses of solar observations are usually model-driven. Hence advances in model calculations and constraints from precise CR measurements are timely and needed.Here we present our StellarICS code to compute the gamma-ray IC emission from the Sun and also from single stars. The code is publicly available and it is extensively used by the scientific community to analyze Fermi-LAT data. It has been used by the Fermi-LAT collaboration to produce the solar models released with the FSSC Fermi Tools. Our modeling provides the basis for analyzing and interpreting high-energy data of the Sun and of stars.After presenting examples of updated solar IC models in the Fermi-LAT energy range that account for the various CR measurements, we extend the models to keV, MeV, and TeV energies for predictions for future possible telescopes such as AMEGO, GECCO, e-ASTROGAM, HAWC, LHAASO, SWGO, and present X-ray telescopes. We also present predictions for some of the closest and most luminous stars.

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Simulating gamma-ray production from cosmic rays interacting with the solar atmosphere in the presence of coronal magnetic fields

Cited by 9 publications

References 57 publications

First Observations of Solar Disk Gamma Rays over a Full Solar Cycle

First Observations of Solar Disk Gamma Rays over a Full Solar Cycle

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

StellarICS: Inverse Compton Emission from the Quiet Sun and Stars from keV to TeV

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