Studies of electromagnetic ion cyclotron waves using AMPTE/CCE and dynamics explorer

The overall objective of this research is to investigate the generation and propagation of electromagnetic ion cyclotron (EMIC) waves in the frequency range from 0.2 to 5 Hz (Pc 1 frequency band). Data used in this research were acquired by the AMPTE/CCE, DE-1, and DE-2 satellites. One of the primary questions addressed in this research is the role which EMIC waves have on the transfer of energy from the equatorial magnetosphere to the ionosphere. The primary result from this research is that some fraction of EMIC waves, generated in the equatorial magnetosphere, are Landau damped in the ionosphere and are therefore a heat source for ionospheric electrons. This result as well as other results are summarized below

Studies of electromagnetic ion cyclotron waves using AMPTE/CCE and Dynamics Explorer

The principal activity during the past six months has involved the analysis of ion cyclotron waves recorded from DE-2 using the magnetic field experiment and electric field experiment. The results of this study have been published in the Geophysical Research Letters (GRL). The primary finding of this paper is that ion cyclotron waves were found to heat electrons, as observed in the DE-2 Langmuir probe data, through a Landau damping process. A second activity, which was started during the last six months, involves the study of large amplitude approximately one Hz electric and magnetic field oscillations recorded in the nightside auroral zone at substorm onset. Work is under way to determine the properties of these waves and investigate any association these waves may have with the substorm initiation process. A third activity under way involves a comprehensive study of ion cyclotron waves recorded at ionospheric altitudes by DE-2. This study will be an extension of the work reported in the GRL paper and will involve a larger sampling of wave events. This paper will focus on wave properties at ionospheric altitudes. A fourth activity involves a more in-depth analysis of the acceleration mechanisms and the resulting electron distributions based on the observations presented in the GRL paper

Small Scattered Fragments Do Not a Dwarf Make: Biological and Archaeological Data Indicate that Prehistoric Inhabitants of Palau Were Normal Sized

Current archaeological evidence from Palau in western Micronesia indicates that the archipelago was settled around 3000–3300 BP by normal sized populations; contrary to recent claims, they did not succumb to insular dwarfism

Comparison of Measured High-Latitude F-Region Ion Composition Climatology Variability with Models

Satellite measurements of the global F-region ion composition morphology, due to orbit-to-orbit variations in space and time, are most effectively examined statistically, taking into consideration the ranges of variability in the data. Simple averages of the measurements do not clearly delineate narrow and time varying features such as density troughs/holes, sharp ionospheric layers, or even auroral region enhancements of electron temperature/molecular ion concentrations. These in fact are the most prominent features seen along individual satellite passes and are features which have prominent climatological variations To explore how well current ionosphere models fare with reality at middle and high latitudes, the entire ensemble of available solar minimum satellite ion composition measurements (predominantly from Atmosphere Explorer C and D) are sorted into spatial, temporal and magnetic/solar activity indices bins. Ion concentrations obtained from multiple runs of the International Reference Ionosphere (IRI) and the Utah State University Time Dependent Ionosphere model (TDIM), sorted into bins similar to those used for the satellite data sets are compared to the measurements. As currently configured the IRI model does not make a good match with the middle and high latitude topside ionosphere ion composition measurements. The TDIM is a better match to the measurements but does not reproduce the deepest high latitude ionospheric troughs and auroral-cusp molecular ion enhancements

Where were the northern elephant seals? Holocene archaeology and biogeography of \u3cem\u3eMirounga angustirostris\u3c/em\u3e

Driven to the brink of extinction during the nineteenth century commercial fur and oil trade, northern elephant seal (NES, Mirounga angustirostris) populations now exceed 100 000 animals in the northeast Pacific from Alaska to Baja California. Because little is known about the biogeography and ecology of NES prior to the mid-nineteenth century, we synthesize and analyze the occurrence of NES remains in North American archaeological sites. Comparing these archaeological data with modern biogeographical, genetic, and behavioral data, we provide a trans-Holocene perspective on NES distribution and abundance. Compared with other pinnipeds, NES bones are relatively rare throughout the Holocene, even in California where they currently breed in large numbers. Low numbers of NES north of California match contemporary NES distribution, but extremely low occurrences in California suggest their abundance in this area was very different during the Holocene than today. We propose four hypotheses to explain this discrepancy, concluding that ancient human settlement and other activities may have displaced NES from many of their preferred modern habitats during much of the Holocene