Magnetic pressure support and accretion disk spectra

Stellar atmosphere models of ionized accretion disks have generally neglected the contribution of magnetic fields to the vertical hydrostatic support, although magnetic fields are widely believed to play a critical role in the transport of angular momentum. Simulations of magnetorotational turbulence in a vertically stratified shearing box geometry show that magnetic pressure support can be dominant in the upper layers of the disk. We present calculations of accretion disk spectra that include this magnetic pressure support, as well as a vertical dissipation profile based on simulation. Magnetic pressure support generically produces a more vertically extended disk atmosphere with a larger density scale height. This acts to harden the spectrum compared to models that neglect magnetic pressure support. We estimate the significance of this effect on disk-integrated spectra by calculating an illustrative disk model for a stellar mass black hole, assuming that similar magnetic pressure support exists at all radii.Comment: submitted to Ap

Biotechnology, Schismogenesis, and the Demise of Uncertainty

One of the most fundamental aspects of science is uncertainty. Uncertainty fuels scientists to research, experiment, and draw conclusions. Interestingly, both sides of the current “GMO-war” are alleging certainty where it simply does not exist. Through the use of a case study of Bt in India, this Article addresses the irony inherent in both the pro- and anti-GMO arguments based on science that is allegedly foolproof