Rapport quadriennal 1995-1998

The aim of our paper is to show the importance of geomagnetic data to the knowledge of the main geomagnetic field and its secular variation, and also of the temporal, in order to survey the Earth's environment. Firstly, we recall the results obtained on the high-resolution secular variation of the geomagnetic field in two sites situated in Western Europe (London and Paris) over the last four centuries. The declination data are remarkably well correlated between the two sites and can be used to construct a more complete and accurate synthetic series, in which many gaps or times with scattered or uncertain data can be amended. The built declination synthetic series is believed to be valid for much Western Europe, and information about the secular variation in this area are obtained. But, to characterise the geomagnetic field, the spatial variations are also important. To monitor the field variations, an international program has been developed since 1988. Under the INTERMAGNET program, high quality data from a global network of geomagnetic observatories are sent in near real time via satellite and computer links to world-wide collection and disseminatin points called "Geomagnetic Information Nodes" or GINs. All INTERMAGNET observatories operate with the same common specifications (resolution, filtering, sampling rate, data formats etc.) Today, the INTERMAGNET observatories data-sets of 1.0 minute values with good baselines are available within minutes and hours from about 60 observatories. Another INTERMAGNET goal is to fill out the global geomagnetic observatory distribution. In fact, a recent study specified the minimum number of equally spaced observatories needed to do a degree and order 10 spherical harmonic model of the main field. The model required a minimum of 92 observatories on about a 2,000 km spacing. Eight sites would require ocean bottom observatories... (D'après résumé d'auteur

A new southern high-latitude index

We have developed and examined a new regional geomagnetic index AES-80, defined similarly to the classical auroral electrojet AE index, using data from five Antarctic stations located at corrected geomagnetic latitudes about 80 °S. Because only sparse ground-based information can be derived from auroral latitudes in the Southern Hemisphere, and because no index comparable to AE can be constructed from locations in the south, the possibility of using AES-80 as a measure of high latitudes and polar cap activity is investigated. As a global average activity level indicator, it is found that in general AES-80 gives results rather similar to the classical AE index. However AES-80 provides a more robust measure of the occurrence of high-latitude geomagnetic activity.Key words. Magnetospheric physics (auroral phenomena; polar cap phenomena)

Les rapports des campagnes a la mer MD 61 / GEOPHYCIR a bord du 'Marion-Dufresne' 26 mars-28 avril 1989

Available at INIST (FR), Document Supply Service, under shelf-number : 22526, issue : a.1994 n.02 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Entertainment as a Creature Comfort: Self-Control and Selection of Challenging Media

A between-subjects experiment examined selective exposure to films in an imagined self-control scenario, and if exposure would be systematically related to perceptions of the film content as challenging, enjoyable, and a should versus a want choice. Across 3 measures of selective exposure—using open-ended choice, closed-ended choice, and prospective ratings—participants in the depletion condition were less likely to select films that were cognitively challenging, affectively challenging, or a should choice. In contrast to nondepleted participants, depleted participants were more likely to select films they expected being fun, suspenseful, and less appreciated. These results provide support for the proposition that users’ momentary self-control capacity and their perception of challenge provided by content predict media choice