Cosmic-Ray Acceleration and Magnetic Fields in Galaxy Clusters and Beyond: Insights from Radio Observations
Abstract
:1. Introduction
2. Large-Scale Motions in the ICM
3. Measuring Magnetic Fields and Cosmic Rays
4. The Evolution of Magnetic Fields
5. Radio Halos—Turbulent Re-Acceleration in the ICM
5.1. Pure Hadronic Model of Radio Halos
5.2. Turbulent Re-Acceleration
5.3. Mega Radio Halos
5.4. Polarisation
5.5. High Redshifts
5.6. Basics of Mini-Halos
6. Radio Relics—Shock Acceleration in the ICM
6.1. Basics of Shock Acceleration
6.2. Pre-Acceleration of Cosmic Rays
6.3. The Shocks’ Mach Numbers
6.4. Polarisation
6.5. Lowest Radio Frequencies
6.6. Shock Acceleration of Cosmic-Ray Protons
7. Beyond the Classical Radio Sources
7.1. Gently Re-Energising Tails
7.2. Remnant Sources
7.3. Odd Radio Circles
8. Beyond Clusters: Cosmic Filaments and Voids
8.1. Intercluster Bridges
8.2. Cosmic Filaments and Voids
9. Summary
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
1 | In principle, also cosmic-ray protons could be present in the Universe. However, they have never been unambiguously observed. Throughout this paper, we use cosmic-ray electrons and cosmic rays interchangeably. We state explicitly when we are talking about cosmic-ray protons. |
2 | To put this fast evolution of the field into numbers, according to the ADS abstract service, in the period 2000 to 2009, 47 papers were published that contained the word “radio relic” in the abstract. Between 2010 and 2019, this number increased to 212, and, between 2020 and 2022, already 69 such papers have been published. Similar numbers are found when searching for “radio halo”. Here, the number of papers increased from 157 (period 2000–2009) to 282 (period 2010–2019). Between 2020 and 2022, 83 such papers have been published. |
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Wittor, D. Cosmic-Ray Acceleration and Magnetic Fields in Galaxy Clusters and Beyond: Insights from Radio Observations. Universe 2023, 9, 319. https://doi.org/10.3390/universe9070319
Wittor D. Cosmic-Ray Acceleration and Magnetic Fields in Galaxy Clusters and Beyond: Insights from Radio Observations. Universe. 2023; 9(7):319. https://doi.org/10.3390/universe9070319
Chicago/Turabian StyleWittor, Denis. 2023. "Cosmic-Ray Acceleration and Magnetic Fields in Galaxy Clusters and Beyond: Insights from Radio Observations" Universe 9, no. 7: 319. https://doi.org/10.3390/universe9070319