Showing papers in "Annales Geophysicae in 1987"

An auroral model for the NCAR thermospheric general circulation model (TGCM)

Abstract: A model of high latitude auroral processes has been developed for use in the NCAR TGCM. The ion drift pattern associated with magnetospheric convection is specified by the empirical model of Heelis et al. (1982) considering offset geographic and geomagnetic poles. An analytic prescription of particle precipitation in the auroral oval is developed that enables rapid numerical evaluation of auroral ionization rates and global aurora power input. An analytic expression has been derived for the total ionization rate and an ion chemical scheme is used to calculate the electron density enhancements and ion density distributions caused by auroral particle precipitation. The results of TGCM runs with and without auroral particle precipitation show the importance of auroral ionization in determining the dynamic structure of the winter hemisphere lower thermosphere.

Thermospheric neutral wind signatures dependent on the east-west component of the interplanetary magnetic field for Northern and Southern Hemispheres as measured from Dynamics Explorer-2

Abstract: DE-2 neutral-wind measurements obtained between November and January 1981-1982 and 1982-1983 were analyzed to investigate the effect of the sign of the IMF By component on neutral thermosphere dynamics at F-region altitudes. Maps of the mean neutral circulation for the northern (winter) and southern (summer) polar regions were derived for By positive and negative using polar geomagnetic coordinates. The mean neutral winds demonstrate clear By-dependent neutral wind signatures in both hemispheres.

Two hundred years of auroral activity (1780-1979)

Abstract: Methode de compilation des series d'observation, traitement des lacunes. Pour les periodes ou il n'y a pas de donnees sur l'activite geomagnetique on utilise les donnees de l'activite solaire

Response of the auroral oval precipitation and magnetospheric convection to changes in the interplanetary magnetic field

Abstract: High-latitude observations on January 18, 1984 during the first GISMOS campaign are examined. An intense substorm occurred after a long period of quiescent geomagnetic activity when the IMF decreased gradually over a 2-hour period from +5 to -8 nT. This present study investigates how the auroral precipitation boundary, the energy flux, and the convection respond to this change from quiet to active conditions.

Ionospheric electrodynamics over Saint-Santin and Millstone Hill during 26-28 June 1984

Abstract: Ion drift measurements were carried out using the incoherent scatter radars at Saint-Santin and Millstone Hill during the June 26-28, 1984 Global Thermospheric Mapping Study campaign. The electric field results from both stations for June 26 indicate a pattern characteristic of quiet geomagnetic conditions, consistent between the two stations, in contrast to the results for the geomagnetically disturbed day of June 28 which exhibit large electric fields that differ significantly at the two stations. The meridional neutral winds derived from the ion-drift component parallel to the magnetic field at the two stations under the same model assumptions agree well, and show strong southward winds at night, weaker in the daytime, and large oscillations during magnetic disturbances.

A kinetic model of parallel electric field in the magnetosphere.

Abstract: Le modele propose de distribution du potentiel electrique le long des lignes du champ magnetique tient compte de l'energie et de la distribution en angle d'attaque des particules chargees ainsi que de l'absence de particule dans le cone de perte. On compare les solutions obtenues pour un cone de perte evanescent et un cone de perte de dimension finie