Two-dimensional spatial power spectra of photospheric velocity fluctuations

Two-dimensional spatial autocorrelation functions and power spectral density distributions were obtained from high-resolution velocity spectroheliograms. Although the autocorrelation functions indicate the existence of velocity cells of size roughly 2500 to 3500 km, the power spectra fail to reveal them because the cells are not strictly spatially periodic.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43736/1/11207_2004_Article_BF00162429.pd

The Role of the Submerged Prehistoric Landscape in Ground-Truthing Models of Human Dispersal During the Last Half Million Years

Human genome analysis and research into fossil anthropogenic nuclear DNA and mitochondrial DNA are providing many new insights into hominin diffusion and migration over the past half million years. The beginning and end data on migration routes frequently imply that the migration involved crossing a present sea-channel or marginal basin, or migrating along the present continental shelf. However, there are very few attempts to correlate the models based on DNA with in situ archaeological and palaeoenvironmental data from the continental shelf or shelf marginal seas. Yet a significant number of sites are available for such correlation. Over 3000 submerged prehistoric archaeological sites on the continental shelf are known worldwide, varying in depth from the nearshore to about −100 m and ranging in age from 5000 years to >0.5 million years. Sites have been found off the coast of every continent except Antarctica. Most of the sites found so far are shallower than 10–20 m, with a few deeper than 40 m, and none are in the tropics. The submerged sites found so far exist in a very wide range of taphonomic conditions and climatic zones, confirming that sites could be found to provide empirical tests of the many different proposed migration routes. The principal exception is that no sites have yet been found between the Tropics of Cancer and Capricorn and the so-called Southern Route cannot yet be checked until the submerged landscape has been mapped in sufficient detail indicating where sites might survive and be identified. In all other geographic regions it is recommended that DNA models and seabed data are examined for consistency and mutual benefit. Further work is needed to identify submerged sites and landscapes in the tropics