Tearing-mediated Alfvénic Turbulence in a Relativistic Plasma

Journal Article · Wed Jan 29 00:00:00 EST 2025 · The Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/ada28a· OSTI ID:2507366

Boldyrev, Stanislav ^[1]; Loureiro, Nuno F. ^[2]

---

1. Univ. of Wisconsin, Madison, WI (United States); Space Science Institute, Boulder, CO (United States)
2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

In astrophysical relativistic plasmas, Alfvénic turbulence exists across a wide range of scales. Similar to a nonrelativistic case, this turbulence can be influenced by the tearing instability. We argue that in an ultrarelativistic pair plasma the tearing effects become significant at the critical scale given by $${a}_{t}\sim {d}_{\mathrm{rel}}{\left({L}_{\perp }/{d}_{\mathrm{rel}}\right)}^{n/(4+5n)}$$, where L_⊥ represents the outer scale of the turbulence and d_rel the relativistic electron inertial scale. Here n = 1 corresponds to the Harris magnetic configurations, while n = 2 applies to localized (non-Harris) magnetic profiles of turbulence-generated current sheets. Below the critical scale, the energy spectrum of magnetic fluctuations steepens to W(k)dk ∝ k^-(7n+2)/3ndk. However, this happens only when $$\tilde{\sigma }\ll {\left({L}_{\perp }/{d}_{\mathrm{rel}}\right)}^{(2+4n)/(4+5n)}$$, where $$\tilde{\sigma }$$ is the magnetization parameter based on the magnetic fluctuations. If the opposite inequality holds, the Alfvénic cascade is instead affected by charge starvation at scales below $${a}_{\mathrm{ch}}\sim {d}_{\mathrm{rel}}{\left({d}_{\mathrm{rel}}/{L}_{\perp }\right)}^{1/3}{\tilde{\sigma }}^{2/3}$$, and the energy spectrum becomes steeper than W(k)dk ∝ k^-3dk. When d_rel is replaced by its nonrelativistic equivalent, our results agree with the nonrelativistic analysis of N. F. Loureiro & S. Boldyrev (2018). In the Harris case n = 1, they agree with the recent relativistic studies by I. Demidov & Y. Lyubarsky.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: FG02-91ER54109; SC0024362
• OSTI ID: 2507366
• Alternate ID(s): OSTI ID: 2557565
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 979; ISSN 0004-637X
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
magnetic fields
plasma astrophysics