Annales Geophysicae

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Localized structure in the cusp and high-latitude ionosphere: a modelling study
Annales Geophysicae - Tập 17 - Trang 455-462 - 1999
H. F. Balmforth, R. J. Moffett, A. S. Rodger
The ionospheric signature of a flux transfer event (FTE) seen in EISCAT radar data has been used as the basis for a modelling study using a new numerical model of the high-latitude ionosphere developed at the University of Sheffield, UK. The evolution of structure in the high-latitude ionosphere is investigated and examined with respect to the current views of polar patch formation and development...... hiện toàn bộ
Auroral E-region electron density gradients measured with EISCAT
Annales Geophysicae - Tập 18 - Trang 1172-1181 - 2000
C. Haldoupis, K. Schlegel, G. Hussey
In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the am...... hiện toàn bộ
ULYSSES observations of energetic particle acceleration and the superposed CME and CIR events of November 1992
Annales Geophysicae - Tập 14 - Trang 400-410 - 1996
T. L. Lim, J. J. Quenby, M. K. Reuss, E. Keppler, H. Kunow, B. Heber, R. J. Forsyth
During November 1992, a series of forward and reverse shocks passed the ULYSSES spacecraft. Spectral and anisotropy measurements are reported for protons and alpha particles between 0.28 and 6 MeV observed by the Energetic Particle Composition Experiment, data recorded by the Magnetometer Experiment and the high-energy (2.7-300 MeV) proton data from the Kiel Electron Telescope. An analysis of ener...... hiện toàn bộ
Propagation and dispersion of electrostatic waves in the ionospheric E region
Annales Geophysicae - Tập 15 - Trang 878-889 - 1997
K. Iranpour, H. L. Pecseli, J. Trulsen, A. Bahnsen, F. Primdahl, K. Rinnert
Low-frequency electrostatic fluctuations in the ionospheric E region were detected by instruments on the ROSE rockets. The phase velocity and dispersion of plasma waves in the ionospheric E region are determined by band-pass filtering and cross-correlating data of the electric-field fluctuations detected by the probes on the ROSE F4 rocket. The results were confirmed by a different method of analy...... hiện toàn bộ
Ocean feature models – their use and effectiveness in ocean acoustic forecasting
Annales Geophysicae - Tập 15 - Trang 101-112 - 1997
J. Small, L. Shackleford, G. Pavey
The aim of this paper is to test the effectiveness of feature models in ocean acoustic forecasting. Feature models are simple mathematical representations of the horizontal and vertical structures of ocean features (such as fronts and eddies), and have been used primarily for assimilating new observations into forecasts and for compressing data. In this paper we describe the results of experiments...... hiện toàn bộ
Latitudinal distribution of the solar wind properties in the low- and high-pressure regimes: Wind observations
Annales Geophysicae -
Catherine Lacombe, C. S. Salem, A. Mangeney, J. L. Steinberg, M. Maksimović, J. M. Bosqued
Abstract. The solar wind properties depend on λ, the heliomagnetic latitude with respect to the heliospheric current sheet (HCS), more than on the heliographic latitude. We analyse the wind properties observed by Wind at 1 AU during about 2.5 solar rotations in 1995, a period close to the last minimum of solar activity. To determine λ, we use a model of the HCS which we fit to the magnetic...... hiện toàn bộ
Westward moving dynamic substorm features observed with the IMAGE magnetometer network and other ground-based instruments
Annales Geophysicae - Tập 16 - Trang 425-440 - 1998
H. Lühr, A. Aylward, S. C. Bucher, A. Pajunpää, K. Pajunpää, T. Holmboe, S. M. Zalewski
We present the ground signatures of dynamic substorm features with particular emphasis on the event interpretation capabilities provided by the IMAGE magnetometer network. This array covers the high latitudes from the sub-auroral to the cusp/cleft region. An isolated substorm on 11 Oct. 1993 during the late evening hours exhibited many of well-known features such as the Harang discontinuity, westw...... hiện toàn bộ
Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind
Annales Geophysicae - Tập 18 - Trang 300-315 - 2000
Y. I. Portnyagin, T. V. Solovjova
An updated empirical climatic zonally averaged prevailing wind model for the upper mesosphere/lower thermosphere (70/110 km), extending from 80°N to 80°S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude contour plots of monthly mean zonal and merid...... hiện toàn bộ
A localised co-rotating auroral absorption event observed near noon using imaging riometer and EISCAT
Annales Geophysicae - Tập 14 - Trang 1305-1316 - 1997
P. N. Collis, J. K. Hargreaves, G. P. White
An isolated region of energetic electron precipitation observed near local noon in the auroral zone has been investigated using imaging riometer (IRIS) and inco-herent-scatter radar (EISCAT) techniques. IRIS revealed that the absorption event was essentially co-rotating with the Earth for about 2 h. The spatial and temporal variations in D-region electron density seen by EISCAT were able to be int...... hiện toàn bộ
Seasonal cycle of cloud cover analyzed using Meteosat images
Annales Geophysicae - Tập 16 - Trang 331-341 - 1998
J. Massons, D. Domingo, J. Lorente
A cloud-detection method was used to retrieve cloudy pixels from Meteosat images. High spatial resolution (one pixel), monthly averaged cloud-cover distribution was obtained for a 1-year period. The seasonal cycle of cloud amount was analyzed. Cloud parameters obtained include the total cloud amount and the percentage of occurrence of clouds at three altitudes. Hourly variations of cloud cover are...... hiện toàn bộ
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