Creation of large temperature anisotropies in a laboratory plasma

Abstract

Ion temperature anisotropy in an expanding magnetized plasma is investigated using laser induced fluorescence. Parallel and perpendicular ion velocity distribution functions (IVDFs) were measured simultaneously with high spatial resolution in the expanding plasma. Large ion temperature anisotropies (T⊥i/T∥i∼10) are observed in a conical region at the periphery of the expanding plasma plume. A simple 2D Boris stepper model that incorporates the measured electric field structure is able to reproduce the gross features of the measured perpendicular IVDFs. A Nyquist stability analysis of the measured IVDFs suggests that multiple instabilities with k⊥ρi∼1 and k||ρi∼0.2 are likely to be excited in these plasmas.

Spontaneous Magnetic Fluctuations and Collisionless Regulation of Turbulence in the Earth's Magnetotail

“…The event probability patterns shown in Fig. 1(top) for each species are consistent with observations in the magnetosheath by the CLUSTER (Gary et al 2005), AMPTE (Phan et al 1994;Anderson et al 1994), and MMS missions (Maruca et al 2018); as well as in the solar wind (Gary et al 2001a;Hellinger et al 2006;Štverák et al 2008;Adrian et al 2016;Huang et al 2020), computer simulations (Gary et al 2001b;Yoon & Seough 2012), and laboratory experiments (Scime et al 2015(Scime et al , 2000Beatty et al 2020) A key difference with most of these works is that the particle energy distributions for ions and electrons in the plasma sheet are better fitted by Kappa distributions (Espinoza et al 2018;Eyelade et al 2021), and that the ion temperature anisotropy is restricted to values 0.4 ≤ A i ≤ 2; whereas in the solar wind the ion velocity distributions are mostly Maxwellians with temperature anisotropies in the range 0.1 ≤ A i ≤ 7. On the other hand, the electron anisotropy distribution in the plasma sheet, as shown in Fig.…”

Modification of the fusion energy gain factor in magnetic confinement fusion due to plasma temperature anisotropy

“…where s = a, b. Transform the velocity space (v a , v b ) to (v r , v c ), which can be proved that the transformation obeys Jacobian determinant to remain the integral form of equation (1), where v c is the velocity of center-of-mass (COM) frame of the fusing particles. We define the plasma temperature anisotropy ratio δ = T ⊥ /T and average temperature T = (2T ⊥ + T )/3 to simplify the distribution function as,…”

“…Magnetized plasma, both in astrophysical medium or that created in laboratories, generally presents an anisotropy in ion temperature [1], which can be interpreted in the microscopic way by an anisotropic ion velocity distribution function (IVDF). Temperature anisotropy exists ubiquitously in many astrophysical plasmas such as solar winds [2,3], stellar surface plasmas [4,5], the medium of galaxy clusters [6], and direction of the beam is heated primarily, and the temperature anisotropy ratio is determined by the angle between the beam direction and the magnetic field [10,11].…”

Dispersion relation and instability for an anisotropic nonuniform flowing plasma

“…The off-diagonal elements can be ignored when a plasma is not too far from bi-Maxwellian or Maxwellian. The anisotropic diagonal pressure can be established by the background magnetic or electric field [11,30,34], anisotropic heating [35,36], and expansion or compression of a plasma [37,38]. When the distribution function is far from the bi-Maxwellian so that the off-diagonal elements are non-negligible compared to the diagonal elements, one has to take into account the viscosity tensor π a = m a…”

“…However, the waves in a nonuniform plasma can be unstable [2][3][4][5], and the stability can be modified by a finite flow or an anisotropic pressure [6][7][8]. An anisotropy effect should be taken into account for a strongly magnetized plasma [9][10][11].…”