Can solar wind viscous drag account for CME deceleration?

The forces acting on solar Coronal Mass Ejections (CMEs) in the interplanetary medium have been evaluated so far in terms of an empirical drag coefficient $C_{\rm D} \sim 1$ that quantifies the role of the aerodynamic drag experienced by a typical CME due to its interaction with the ambient solar wind. We use a microphysical prescription for viscosity in the turbulent solar wind to obtain an analytical model for the drag coefficient $C_{\rm D}$. This is the first physical characterization of the aerodynamic drag experienced by CMEs. We use this physically motivated prescription for $C_{\rm D}$ in a simple, 1D model for CME propagation to obtain velocity profiles and travel times that agree well with observations of deceleration experienced by fast CMEs.Comment: Accepted for publication in the Geophysical Research Letter

Inner region accretion flows onto black holes

We examine here the inner region accretion flows onto black holes. A variety of models are presented. We also discuss viscosity mechanisms under a variety of circumstances, for standard accretion disks onto galactic black holes and supermassive black holes and hot accretion disks. Relevant work is presented here on unified aspects of disk accretion onto supermassive black holes and the possible coupling of thick disks to beams in the inner regions. We also explore other accretion flow scenarios. We conclude that a variety of scenarios yield high temperatures in the inner flows and that viscosity is likely not higher than alpha $\sim$ 0.01.Comment: to appear in "The Neutron Star - Black Hole Connection", proceedings of NATO Advanced Study Institute, 7 - 18 June 1999, Elounda, Crete, Greec

CME dynamics using STEREO & LASCO observations: the relative importance of Lorentz forces and solar wind drag

We seek to quantify the relative contributions of Lorentz forces and aerodynamic drag on the propagation of solar coronal mass ejections (CMEs). We use Graduated Cylindrical Shell (GCS) model fits to a representative set of 38 CMEs observed with the SOHO and STEREO spacecraft. We find that the Lorentz forces generally peak between 1.65 and 2.45 Rsun for all CMEs. For fast CMEs, Lorentz forces become negligible in comparison to aerodynamic drag as early as 3.5--4 Rsun. For slow CMEs, however, they become negligible only by 12--50 Rsun. For these slow events, our results suggest that some of the magnetic flux might be expended in CME expansion or heating. In other words, not all of it contributes to directed propagation. Our results are expected to be important in building a physical model for understanding the Sun-Earth dynamics of CMEs.Comment: 21 pages, 7 figures, Accepted for publication in Topical Issue of Solar Physics- Earth-affecting solar transient

Patterns of international capital flows and their implications for economic development

Capital ; Economic development