Speaker
Dr
Donald Ngobeni
(Vaal University of Technology)
Description
It is well known that particle drift motions are suppressed by diffusive scattering as established by direct numerical simulations. The effect of constant scattering on the drift velocities of charged particles has always been included in numerical modulation models provided that the weak scattering drift velocity is scaled down in magnitude, although in an empirical manner as comparisons between drift models and observations required. What has not yet been established is the spatial dependence of the scattering parameter (ωτ), with ω the gyro-frequency and τ some time scale defined by scattering. What is currently known about the spatial and rigidity dependence of ωτ is used to illustrate and discuss its effect on the drift coefficient in the modulation of cosmic ray Carbon in the heliosphere. This is done with a well-established numerical model which includes all four major modulation processes, the solar wind termination shock (TS) and the heliosheath. We estimate that a reasonable range in the magnitude of ωτ is 0 ≤ ωτ ≤ 5, applicable to modulation studies inside and outside the TS. Furthermore, it is found that the considered different scenarios for ωτ cause significant modifications to the weak scattering drift coefficient and as such on the subsequent computed differential intensities in both solar magnetic polarity cycles. Scenarios of ωτ with strong decreases over the heliospheric polar regions seem unlikely for the modulation of galactic cosmic rays in the upstream region of the TS.
| Registration number following "ICRC2015-I/" | 71 |
|---|---|
| Collaboration | -- not specified -- |
Author
Dr
Donald Ngobeni
(Vaal University of Technology)
Co-author
Prof.
Marius Potgieter
(Centers for Space Research, North-West university)
