Progress at IMER

In September 1970 the Natural Environment Research Council formed the new Institute for Marine Environmental Research by incorporation of the former Oceanographic Laboratory, at Edinburgh, of the Scottish Marine Biological Association. The intention was (a) to develop studies of variability in near-shore waters and estuaries, comparable with those carried out by the Edinburgh Laboratory for more than twenty years in the open ocean, (b) to integrate physical, chemical and biological studies of these ecosystems and (c) to link the field studies with related experimental investigations in the laboratory. In all of this it was intended that pollution and pollutants should be studied—not as topics in isolation—but as parts of the set of environmental variables that affect plants and animals. In particular it was intended that the programmes would give effect to the generally recognised tenet that under-standing of natural variability is an essential basis for the detection and prediction of any effects that man's impact might have on the marine environment.     

SCAP at UCL

Mike Bode and Phil Charles present the minutes of the 11th meeting of the Standing Conference of Astronomy Professors on 3 July 2001.     

The mid-latitude F region at the mesoscale: some progress at last

Almost no new theoretical work has been conducted in the area of mid-latitude F-region plasma instabilities since Perkin's (J. Geophys. Res. 78 (1973) 218) linear theory. New experimental data now suggest that the nonlinear development of mid-latitude F-region structures includes large polarization electric fields which dominate the final state. Airglow and radar data show that Σ_P is greatly depleted in some regions, which is in agreement with a polarization hypothesis. We hope these new results will inspire new simulations with some anticipation of solving this perplexing but fascinating problem.     

Tectonic erosion at trenches

Tectonic erosion of inner trench slopes of some arc systems has been suggested as a viable process. The discontinuity and truncation of structures along the coastline from Mexico to Chile demands a process by which continental crust is removed, but marine geologic and geophysical evidence indicates that accretion rather than erosion is presently occurring in those trenches. A more plausible process is the rifting of continental margins along the trend of the arc systems as an effect of oblique sucduction. This process can be observed in the Baja California region. Tectonic erosion in oceanic trenches, as the Tonga trench, is precluded by the steady growth of the inner slope area. Geologic and geophysical data from these regions implies the accretion of oceanic basement.     

Geosciences at Nice 2003

Simon Mitton reports from the joint meeting in April of the European Geophysical Society, the American Geophysical Union and The European Union of Geosciences, the largest geosciences meeting in Europe.     

Black holes at work

Andrew C Fabian reviews the role that black holes play in the evolution of the galaxies that surround them, in his 2009 Presidential Address to the Royal Astronomical Society.     

The F-layer at sunrise

It was noticed 60 years ago that at sunrise (i) the ionospheric critical frequency foF2 increases faster in winter than in summer and (ii) the increase begins at a greater solar zenith angle in winter. It was later suggested that this “seasonal sunrise anomaly” is due to a seasonal change of atomic/molecular ratio in the neutral air in the F2-layer. This paper uses the Sheffield University plasmasphere-ionosphere computational model (SUPIM) with the MSIS thermosphere model to examine the relative importance at sunrise of production, loss and diffusion processes, and the effect of neutral air winds. The results show that both (i) and (ii) can be explained in terms of neutral composition changes.     

Some unusual discrete VLF emissions observed at a low-latitude ground station at Agra

A detailed analysis of the VLF emissions data obtained during occasional whistler campaigns at the low-latitude ground station Agra (geomagnetic latitude 17°1 N, L = 1.15) has yielded some unusual discrete VLF emissions of the rising type. These include (1) emissions occurring at time intervals increasing in geommetrical progression, (2) emissions occuring simultaneously in different frequency ranges and (3) emissions observed during daytime. In the present study, the observed characteristics of these emissions are described and interpreted. It is shown that the increasing time delay between different components of the emissions match closely with the propagation time delays between different hops of a whistler of dispersion 19 s^1/2, the unusual occurrence of the emissions in two different frequency ranges approximately at the same time may possibly be linked with their generation at two different locations, and the occurrence of emissions during daytime may be due to propagation under the influence of equatorial anomaly.