Can the Einstein-de Sitter model adequately describe the Universe at any epoch?

The characteristics of Friedmann model universes containing decoupled matter and radiation are investigated to establish the range in redshift over which the frequently assumed Einstein-de Sitter approximation is valid. This approximation is found to have decidedly doubtful value for small, yet entirely plausible, values of the material density parameter.     

Collisional heating by nonthermal electrons in a tapered magnetic loop

We examine the behavior of non-thermal electrons injected into a tapered magnetic loop, under the action of both Coulomb collisional and magnetic field gradient forces. An approximate analytic formula for the heating rate as a function of distance along the loop is developed, and found to be in good agreement with exact numerical solutions of the relevant equations. Such a formula is useful as a source term in many situations, such as hydrodynamic simulations of atmospheric response to flare energy input.Presidential Young Investigator.     

Temperature variability over the past millennium inferred from Northwestern Alaska tree rings

We describe a new tree-ring width data set of 14 white spruce chronologies for the Seward Peninsula (SP), Alaska, based on living and subfossil wood dating from 1358 to 2001 AD. A composite chronology derived from these data correlates positively and significantly with summer temperatures at Nome from 1910 to 1970, after which there is some loss of positive temperature response. There is inferred cooling during periods within the Little Ice Age (LIA) from the early to middle 1600s and late 1700s to middle 1800s; and warming from the middle 1600s to early 1700s. We also present a larger composite data set covering 978–2001 AD, utilizing the SP ring-width data in combination with archaeological wood measurements and other recent collections from northwestern Alaska. The Regional Curve Standardization (RCS) method was employed to maximize potential low-frequency information in this data set. The RCS chronology shows intervals of persistent above-average growth around the time of the Medieval Warm Period (MWP) early in the millennium, which are comparable to growth levels in recent centuries. There is a more sustained cold interval during the LIA inferred from the RCS record as compared to the SP ring-width series. The chronologies correlate significantly with Bering and Chukchi Sea sea surface temperatures and with the Pacific Decadal Oscillation index. These atmosphere–ocean linkages probably account for the differences between these records and large-scale reconstructions of Arctic and Northern Hemisphere temperatures based largely on continental interior proxy data.     

Seafarer's gaze: Queen Street business and Auckland's archipelago, 1908

Abstract:  In 1908 Auckland City was the commercial hub for a small and remote provincial economy and cannot have supported more than modest, locally orientated enterprises. This paper argues that such a view is conditioned by a 'landlubber's gaze'. By envisaging a seafarer alighting on the City's wharves from a 1908 steamship to encounter the city's commercial heart, it demonstrates that Queen Street opened to a maritime world where Auckland enterprises enjoyed extensive networks and markets. Indeed, Auckland's 'floating world' rivalled its 'residential world'. Such an approach may force us to recast Auckland Province in archipelago and network terms.