TY  - JOUR
A1  - Dzhanoev, Arsen R.
A1  - Sokolov, Igor M.
T1  - The effect of the junction model on the anomalous diffusion in the 3D comb structure
JF  - Chaos, solitons & fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science
N2  - The diffusion in the comb structures is a popular model of geometrically induced anomalous diffusion. In the present work we concentrate on the diffusion along the backbone in a system where sidebranches are planes, and the diffusion thereon is anomalous and described by continuous time random walks (CTRW). We show that the mean squared displacement (MSD) in the backbone of the comb behaves differently depending on whether the waiting time periods in the sidebranches are reset after the step in the backbone is done (a rejuvenating junction model), or not (a non-rejuvenating junction model). In the rejuvenating case the subdiffusion in the sidebranches only changes the prefactor in the ultra-slow (logarithmic) diffusion along the backbone, while in the non-rejuvenating case the ultraslow, logarithmic subdiffusion is changed to a much faster power-law subdiffusion (with a logarithmic correction) as it was found earlier by Iomin and Mendez [25]. Moreover, in the first case the result does not change if the diffusion in the backbone is itself anomalous, while in the second case it does. Two of the special cases of the considered models (the non-rejuvenating junction under normal diffusion in the backbone, and rejuvenating junction for the same waiting time distribution in the sidebranches and in junction points) were also investigated within the approach based on the corresponding generalized Fokker-Planck equations. (c) 2017 Elsevier Ltd. All rights reserved.
KW  - Comb model
KW  - Comb-lattice model
KW  - Cylindrical comb
KW  - Junction model
KW  - Anomalous diffusion
Y1  - 2017
U6  - https://doi.org/10.1016/j.chaos.2017.12.001
SN  - 0960-0779
SN  - 1873-2887
VL  - 106
SP  - 330
EP  - 336
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Dzhanoev, Arsen R.
A1  - Spahn, Frank
A1  - Yaroshenko, Victoriya
A1  - Lühr, Hermann
A1  - Schmidt, Jürgen
T1  - Secondary electron emission from surfaces with small structure
JF  - Physical review : B, Condensed matter and materials physics
N2  - It is found that for objects possessing small surface structures with differing radii of curvature the secondary electron emission (SEE) yield may be significantly higher than for objects with smooth surfaces of the same material. The effect is highly pronounced for surface structures of nanometer scale, often providing a more than 100% increase of the SEE yield. The results also show that the SEE yield from surfaces with structure does not show a universal dependence on the energy of the primary, incident electrons as it is found for flat surfaces in experiments. We derive conditions for the applicability of the conventional formulation of SEE using the simplifying assumption of universal dependence. Our analysis provides a basis for studying low-energy electron emission from nanometer structured surfaces under a penetrating electron beam important in many technological applications.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevB.92.125430
SN  - 1098-0121
SN  - 1550-235X
VL  - 92
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Dzhanoev, Arsen R.
A1  - Schmidt, J.
A1  - Liu, X.
A1  - Spahn, Frank
T1  - Charging of small grains in a space plasma: Application to Jovian stream particles
JF  - International psychogeriatrics
N2  - Context. Most theoretical investigations of dust charging processes in space have treated the current balance condition as independent of grain size. However, for small grains, since they are often observed in space environments, a dependence on grain size is expected owing to secondary electron emission (SEE). Here, by the term "small" we mean a particle size comparable to the typical penetration depth for given primary electron energy. The results are relevant for the dynamics of small, charged dust particles emitted by the volcanic moon Io, which forms the Jovian dust streams. Aims. We revise the theory of charging of small (submicron sized) micrometeoroids to take into account a high production of secondary electrons for small grains immersed in an isotropic flux of electrons. We apply our model to obtain an improved estimate for the charge of the dust streams leaving the Jovian system, detected by several spacecraft. Methods. We apply a continuum model to describe the penetration of primary electrons in a grain and the emission of secondary electrons along the path. Averaging over an isotropic flux of primaries, we derive a new expression for the secondary electron yield, which can be used to express the secondary electron current on a grain. Results. For the Jupiter plasma environment we derive the surface potential of grains composed of NaCl (believed to be the major constituent of Jovian dust stream particles) or silicates. For small particles, the potential depends on grain size and the secondary electron current induces a sensitivity to material properties. As a result of the small particle effect, the estimates for the charging times and for the fractional charge fluctuations of NaCl grains obtained using our general approach to SEE give results qualitatively different from the analogous estimates derived from the traditional approach to SEE. We find that for the charging environment considered in this paper field emission does not limit the charging of NaCl grains.
KW  - plasmas
KW  - planets and satellites: individual: Jupiter
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527891
SN  - 1432-0746
VL  - 591
SP  - 647
EP  - 684
PB  - EDP Sciences
CY  - Les Ulis
ER  -