The present study investigates, via linear theory, how striations (treated as perturbations) created in a plasma cloud centered at 200 km will penetrate into the background inhomogeneous (real) ionosphere as a function of wavelength, integrated Pedersen conductivity ratio of the cloud to ionosphere (Z,ø/23,'), and ambient ionospheric conditions. The study is posed as an eigenvalue problem which while determining the potential variation (eigenmode) along magnetic field lines, self-consistently solves for the growth rate (eigenvalue) in the coupled cloud-inhomogeneous ionosphere system. Perturbed particle densities, fluxes parallel to the magnetic field B, and electrostatic potential are presented as a function of altitude. The results show the importance of the image transport parameter (kL•v,/Wc,)(1 + 'P,2/00C,2) -1 (where k is the wave number transverse to B, L• is the transverse dimension of the cloud, and v, ahd OOc, are the ionospheric ion-neutral collision frequency and ion cyclotron frequency, respectively) in determining the magnitude of imaging and aspect angle of striations with respect to B (i.e., striations take on a parallel component of wave number). Perturbations penetrate further down in the presence of the plasma cloud than was indicated in simple previous studies which neglected image transport and considered the perturbation mapping from one region of the ionosphere to another. Our results show that clouds with smaller conductivity ratios produce image striations further down into the background E region ionosphere with a more uniform coupling as a function of wavelength. It is further shown that there is a slight dependence of the E region coupling of the perturbations on the level of solar activity (solar maximum or minimum conditions) and also that this E region coupling shows a slight dependence on the extent of F region coupling above the cloud. Finally, with a fully self-consistent treatment of F region coupling, the growth rates show negligible short-wavelength damping due to ionospheric coupling for the 23•,b/23d = 4 case. [Farley, 1959[Farley, , 1960Spreiter and Briggs, 1961] that for transverse wavelengths of >• 1 km the magnetic field lines act as equipotenfials, i.e., shorter-wavelength electric field perturbations do not couple effectively from one region of the ionosphere to another. Most ideas about the potential variation along magnetic field lines, as a function of transverse wavelength, are based on these earlier works. Moreover, the multilevel two-dimensional theoretical and numerical simulation studies of barium clouds coupled to the background ionosphere [Lloyd and Haerendel, 1973; Goldman et al., 1974; Scannapieco et al., 1974] have assumed that the electric fields at the cloud level and the background ionosphere are the same. That is, the electric fields have only transverse spatial dependence in the two dimensions perpendicular to the magnetic field and no variation along the magnetic field lines. Estimates of striation behavior, based on linear theory and including coupl...
We discuss the physics and numerical implementation of the radiation transport routine used in the CHAHTB VMD code. It is a one-dimensional 'Cartesian, cylindrical, and spherical symmetry), muitigroupj diffusion approximation. Tests and applications will be discussed as well.
While the Black Lives Matter protests in Portland, Oregon have been largely portrayed in the media as destructive, violent, chaotic, and without focus, many participants experienced something entirely different. This article shares one white person’s experience in a number of racial justice gatherings and protests in Portland from June until August 2020, on the ground and on the “front lines” – in the spirit of and with a focus on social justice, community, and caring, and through a partnership studies (partnerism) lens.
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