Joint Physics Dept.–Inst. for Space Weather Sci. Colloquium

April 9, Thursday (** SPECIAL DAY**)

Universal Scaling Law for Particle Energization in Plasmas

Dr. Mitsuo Oka

U.C. Berkeley

(Solar Physics, Host: Inoue)

**Special Room: CKB 116

**Special Time: 1pm - 2pm with 12:45 pm teatime

**ZOOM Meeting ID for those who cannot attend in-person:

955 9399 6954

(APPROVAL by Prof Ahn REQUIRED for APPH/MTSE PhD Students to attend online)

*Password: check email or request from kenahn@njit.edu

Particles are energized - heated and accelerated to nonthermal energies - in laboratory, space, solar, and astrophysical plasmas. Although shocks and magnetic reconnection are recognized as key processes, the detailed mechanisms and the partitioning of energy between ions and electrons remain unresolved. Using coupled theoretical and observational scaling analyses, we show that a simple relation, dϵ = qVBL, captures plasma energization in a universal way, where dϵ is the particle energy gain, q the particle charge, V the bulk flow speed, B the magnetic field strength, and L a characteristic length scale of energization. Different choices of L lead to distinct predictions: the system size gives the maximum particle energies, while a kinetic scale predicts heating (temperature increase dT) in shocks and reconnection, for both ions and electrons. Our results suggest broad applicability, from solar flares to supernova remnants and planetary magnetospheres, despite some assumptions and limitations. In addition, the scaling captures the essential MHD trends while revealing systematic deviations that point to kinetic effects beyond fluid models, highlighting promising directions for theoretical and simulation studies.