On impulse excitation of the global poloidal modes in the magnetosphere

International audienceThrough the combined action of the field line curvature and finite plasma pressure in some regions of the magnetosphere (plasmapause, ring current) there can exist global poloidal Alfvén modes standing both along field lines and across magnetic shells and propagating along azimuth. In this paper we investigate the spatio-temporal structure of such waves generated by an impulsive source. In general, the mode is the sum of radial harmonics whose structure is described by Hermitian polynomials. For the usually observed second harmonic structure along the background field, frequencies of these radial harmonics are very close to each other; therefore, the generated wave is almost a monochromatic oscillation. But mixing of the harmonics with different radial structure causes the evolution of the initially poloidal wave into the toroidal one. This casts some doubts upon the interpretation of observed high-m poloidal waves as global poloidal modes

Droughts in Poland, 1951-90

One of the negative features of Poland’s climate is the periodic occurrence of atmospheric droughts. The most frequent source of this phenomenon is the occurrence of long-term (sometimes lasting several weeks) rainless periods. The occurrence of these periods is connected with the persistence of a stationary east European high that joins with the Azores anticyclone via central Europe. In such situations, with the accompanying lack or insufficiency of atmospheric precipitation, a drought begins to develop gradually. First, a soil drought appears, followed by hydrologic drought. During a hydrologic drought, a decrease in the ground water flow into surface waters is observed, among other phenomena. This results in the reduction of water flow in rivers. During such periods, a significant drop in the level of underground waters, as well as drying of some springs and small water courses, is observed. In its initial phase of development, a drought exerts its first negative effects on crops. Intensification of this phenomenon also causes disturbances in other sectors of the national economy. Droughts and their negative results do not pose the same threat to all areas of Poland, although in general the influence of droughts is stronger here than in the majority of central European countries. This situation is the result of a combination of natural and historic factors. One of the areas of interest of the Institute of Meteorology and Water Management (IMGW) is continuous monitoring and assessment of the course of meteorological and hydrological phenomena occurring in all areas of Poland. When preparing an analysis of the course of successive periods of drought spells, specialists from the IMGW branch in Poznan noticed the absence of similar studies of this phenomenon in Polish literature. In an attempt to fill this gap, they catalogued all droughts that occurred in Poland from 1951 to 1990. The research methods adopted in this study, and also the general characteristics of droughts in Poland, are summarized in this article

Pc5 waves generated by substorm injection: a case study

We analyzed the spectral-polarized characteristics of Pc5 ULF waves observed on 17 September 2000 after the 03:20:25 UT substorm onset with the satellites GOES 8 and 10 located east and west of the onset location. In the course of the event, the wave polarization changed from mixed (between toroidal and poloidal) to poloidal, and then to mixed again. The hodogram of magnetic field oscillations rotated counterclockwise at GOES 8, and clockwise at GOES 10. It is suggested that the satellites detected the waves generated by the substorm injected clouds of the charged particles drifting in the magnetosphere in the opposite azimuthal directions: GOES 8 (located east of the substorm onset) detected the wave generated by an electron cloud, and GOES 10 (west of the onset) detected the wave generated by a positive ion cloud. This interpretation is confirmed by the energetic particles data recorded by LANL satellites

Schwere Lithiumintoxikationen bei normalen Serumspiegeln

Anliegen Unser Ziel ist es, Faktoren zu identifizieren, die das Risiko einer Lithiumintoxikation trotz normaler Serumspiegel erhöhen. Methode Wir beschreiben zwei eigene Fälle und bewerten diese im Kontext der Literatur. Ergebnisse Alter, Begleiterkrankungen und psychopharmakologische Komedikation erhöhen das Risiko einer Lithiumintoxikation bei normalen Serumspiegeln. Diskussion Bei älteren, multimorbiden Patienten sollte eine engmaschige klinische Kontrolle inklusive Spiegelbestimmung und EEG erfolgen, bei klinischen Anzeichen der Intoxikation sollte auch bei unauffälligen Spiegeln ein Absetzen erwogen werden

Definition of the Alfvén mode in inhomogeneous magnetic field

The article is methodological and defines the concept of the linear Alfvén mode. There are two definitions — electrodynamic and hydrodynamic. In the former, the Alfvén mode is considered a wave with a potential transverse electric field. In the latter, waves are more often identified with the Alfvén mode, plasma motion in which is purely vortex. While these definitions are equivalent for homogeneous plasma, they are incompatible if the field line curvature is taken into account: if the transverse electric field is purely potential, the plasma speed has not only a vortex component, but also a potential one, and vice versa. The electrodynamic and hydrodynamic definitions are equivalent only if the wave electric field completely lacks a component along the binormal to the external magnetic field. However, such waves do not exist in nature