Hybrid Simulation and Quasi-linear Theory of Bi-Kappa Proton Instabilities

Journal Article · 06 September 2023 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/aceb5b · OSTI ID:1998837

López, R. A.  ^[1]; Yoon, P. H.  ^[2]; Viñas, A. F.  ^[3]; Lazar, M.  ^[4]

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1. University of Santiago (Chile)
2. Univ. of Maryland, College Park, MD (United States)
3. The Catholic Univ. of America, Washington, DC (United States)
4. Katholieke Univ. Leuven (Belgium); Ruhr Univ., Bochum (Germany)

The quasi-steady states of collisionless plasmas in space (e.g., in the solar wind and planetary environments) are governed by the interactions of charged particles with wave fluctuations. These interactions are responsible not only for the dissipation of plasma waves but also for their excitation. The present analysis focuses on two instabilities, mirror and electromagnetic ion cyclotron instabilities, associated with the same proton temperature anisotropy T_⊥ > T_∥ (where ⊥, ∥ are directions defined with respect to the local magnetic field vector). Theories relying on standard Maxwellian models fail to link these two instabilities (i.e., predicted thresholds) to the proton quasi-stable anisotropies measured in situ in a completely satisfactory manner. Here we revisit these instabilities by modeling protons with the generalized bi-Kappa (bi-κ power-law) distribution, and by a comparative analysis of a 2D hybrid simulation with the velocity-moment-based quasi-linear (QL) theory. It is shown that the two methods feature qualitative and, even to some extent, quantitative agreement. The reduced QL analysis based upon the assumption of a time-dependent bi-Kappa model thus becomes a valuable theoretical approach that can be incorporated into the present studies of solar wind dynamics.

• Research Organization: Univ. of Maryland, College Park, MD (United States)
• Sponsoring Organization: USDOE Office of Science (SC); USDOE
• Grant/Contract Number: SC0022963
• OSTI ID: 1998837
• Alternate ID(s): OSTI ID: 2422180
• Journal Information: The Astrophysical Journal, Vol. 954, Issue 2; ISSN 0004-637X
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English