Slope of Magnetic Field-Density Relation as An Indicator of Magnetic Dominance
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| Format: | Preprint |
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2024
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| _version_ | 1866915006824579072 |
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| author | Zhao, Mengke Li, Guang-Xing Qiu, Keping |
| author_facet | Zhao, Mengke Li, Guang-Xing Qiu, Keping |
| contents | The electromagnetic field is a fundamental force in nature that regulates the formation of stars in the universe. Despite decades of efforts, a reliable assessment of the importance of the magnetic fields in star formation relations remains missing. In star-formation research, our acknowledgment of the importance of magnetic field is best summarized by the Cruther+ 2010 B-rho relation. The relation is either interpreted as proof of the importance of a magnetic field in the collapse, or the result of self-similar collapse where the role of the magnetic is secondary to gravity. Using simulations, we find a fundamental relation, ${\cal M}_{\rm A}$-k$_{B-ρ}$(slope of $B-ρ$ relation) relation. This fundamental B-$ρ$-slope relation enables one to measure the Alfvénic Mach number, a direct indicator of the importance of the magnetic field, using the distribution of data in the B-$ρ$ plane. It allows us to drive the following empirical $B-ρ$ relation \begin{equation}
\frac{B}{B_c} = {\rm exp}\left(\left(\fracγ{\cal K}\right)^{-1}\left( \fracρ{ρ_c}\right)^\fracγ{\cal K}\right)\nonumber, \end{equation} which offers an excellent fit to the Cruther et al. data, where we assume ${\cal M}_{\rm A}-ρ$ relation. The foundational ${\cal M}_{\rm A}-{\rm k}_{B-ρ}$ relation provides an independent way to measure the importance of magnetic field against the kinematic motion using multiple magnetic field measurements. Our approach offers a new interpretation of Cruther+2010, where a gradual decrease in the importance of B at higher densities is implied. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2409_02786 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Slope of Magnetic Field-Density Relation as An Indicator of Magnetic Dominance Zhao, Mengke Li, Guang-Xing Qiu, Keping Astrophysics of Galaxies Computational Physics Plasma Physics The electromagnetic field is a fundamental force in nature that regulates the formation of stars in the universe. Despite decades of efforts, a reliable assessment of the importance of the magnetic fields in star formation relations remains missing. In star-formation research, our acknowledgment of the importance of magnetic field is best summarized by the Cruther+ 2010 B-rho relation. The relation is either interpreted as proof of the importance of a magnetic field in the collapse, or the result of self-similar collapse where the role of the magnetic is secondary to gravity. Using simulations, we find a fundamental relation, ${\cal M}_{\rm A}$-k$_{B-ρ}$(slope of $B-ρ$ relation) relation. This fundamental B-$ρ$-slope relation enables one to measure the Alfvénic Mach number, a direct indicator of the importance of the magnetic field, using the distribution of data in the B-$ρ$ plane. It allows us to drive the following empirical $B-ρ$ relation \begin{equation} \frac{B}{B_c} = {\rm exp}\left(\left(\fracγ{\cal K}\right)^{-1}\left( \fracρ{ρ_c}\right)^\fracγ{\cal K}\right)\nonumber, \end{equation} which offers an excellent fit to the Cruther et al. data, where we assume ${\cal M}_{\rm A}-ρ$ relation. The foundational ${\cal M}_{\rm A}-{\rm k}_{B-ρ}$ relation provides an independent way to measure the importance of magnetic field against the kinematic motion using multiple magnetic field measurements. Our approach offers a new interpretation of Cruther+2010, where a gradual decrease in the importance of B at higher densities is implied. |
| title | Slope of Magnetic Field-Density Relation as An Indicator of Magnetic Dominance |
| topic | Astrophysics of Galaxies Computational Physics Plasma Physics |
| url | https://arxiv.org/abs/2409.02786 |