Transport of and radiation production by transrelativistic and nonrelativistic particles moving through sub-Larmor-scale electromagnetic turbulence

Abstract

Plasmas with electromagnetic fields turbulent at sub-Larmor scales are a feature of a wide variety of high-energy-density environments and are essential to the description of many astrophysical and laboratory plasma phenomena. Radiation from particles, whether they are relativistic or nonrelativistic, moving through small-scale magnetic turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation. The radiation, carrying information on the statistical properties of the magnetic turbulence, is also intimately related to the particle diffusive transport. We have investigated, both theoretically and numerically, the transport of nonrelativistic and trans-relativistic particles in plasmas with high-amplitude isotropic sub-Larmor-scale magnetic turbulence, and its relation to the spectra of radiation simultaneously produced by these particles. Consequently, the diffusive and radiative properties of plasmas turbulent on sub-Larmor scales may serve as a powerful tool to diagnosis laboratory and astrophysical plasmas.

Diffusion and radiation in magnetized collisionless plasmas with small-scale Whistler turbulence

“…As for any diffusive process, the mean squared pitch angle grows linearly with time. Thus, the diffusion coefficient appears as Keenan & Medvedev (2013), Keenan et al (2015):…”

“…To properly treat the correlation length, we must introduce the two-point autocorrelation tensor of the magnetic fluctuations (Keenan et al 2015), 5) with the path and time-dependent correlation length tensor defined as:…”

“…In our previous works, we found the relation between the transport of ultrarelativistic (Keenan & Medvedev 2013) and non-relativistic/trans-relativistic (Keenan, Ford & Medvedev 2015) particles in isotropic three-dimensional small-scale (mean free) magnetic turbulence and the radiation spectra simultaneously produced by these particles. In Keenan & Medvedev (2013), we found that the radiation spectrum, in the ultrarelativistic (small deflection angle) regime, agrees with the small-angle jitter radiation prediction (Medvedev 2000(Medvedev , 2006Reville & Kirk 2010;Medvedev et al 2011;Teraki & Takahara 2011).…”

“…Furthermore, we demonstrated that the pitch-angle diffusion coefficient is directly related to, and can readily be deduced from, the spectra of the emitted radiation. These results were then generalized to non-relativistic and trans-relativistic velocities in Keenan et al (2015).…”

“…r L λ B . We introduce the gyro number, which fully characterizes the small-scale regime (Keenan et al 2015) as follows:…”