Three spacecraft observations of solar wind discontinuities

Observations of solar wind magnetic field discontinuities using 3 spacecraft allow their orientations to be estimated. During 5 days when Geotail, Wind and IMP 8 were between 6 × 104 and 4 × 105 km apart, 35 events identified using the Tsurutani‐Smith method were detected in all 3 magnetic field data sets. Normals estimated from inter‐spacecraft timings showed that very few were unambiguous rotational discontinuities, with 77% likely to be tangential, with < 20% of the magnetic field at the discontinuity threading the normal plane. However, previous single spacecraft studies using minimum variance suggest that most discontinuities are rotational. Minimum variance analysis resulted in many normal estimates lying far from the timing‐derived normals. While some of this discrepancy is likely to be due to random errors in minimum variance vectors, there appears to be a class of events with small field magnitude changes where the minimum variance directions and discontinuity normals are approximately perpendicular, probably due to surface waves on the discontinuities

Ionospheric photoelectrons at Venus: Initial observations by ASPERA-4

Abstract We report the detection of electrons due to photo-ionization of atomic oxygen and carbon dioxide in the Venus atmosphere by solar helium 30.4 nm photons. The detection was by the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) Electron Spectrometer (ELS) on the Venus Express (VEx) European Space Agency (ESA) mission. Characteristic peaks in energy for such photoelectrons have been predicted by Venus atmosphere/ionosphere models. The ELS energy resolution (DE/E$7%) means that these are the first detailed measurements of such electrons. Considerations of ion production and transport in the atmosphere of Venus suggest that the observed photoelectron peaks are due primarily to ionization of atomic oxygen.

Neural correlates of intelligence and general knowledge obtained by magnetic resonance imaging

Für die vorliegende Dissertation wurde mittels Magnetresonanztomographie untersucht, inwiefern interindividuelle Unterschiede bei Intelligenz und Allgemeinwissen auf Unterschiede in den strukturellen und funktionellen Eigenschaften des Gehirns zurückgeführt werden können. Im Rahmen der ersten Studie konnte gezeigt werden, dass das Allgemeinwissen eines Individuums mit einem graphentheoretischen Maß der strukturellen Hirnkonnektivität assoziiert ist. In der zweiten Studie konnte mittels "Neurite Orientation Dispersion and Density Imaging" nachgewiesen werden, dass die fluide Intelligenz eines Individuums negativ mit der Dendritendichte und -verästelung im Kortex korreliert ist. Für die dritte Studie wurde die Assoziation zwischen fluider Intelligenz und funktioneller Hirnkonnektivität im Ruhezustand untersucht. Hierbei zeigte sich, dass relevante funktionelle Verbindungen in erster Linie durch Hirnregionen konstituiert werden, die Teil der "Parieto-Frontal Integration Theory" sind

Formation of a collisionless shock wave in a multi-component plasma

We discuss the theory of the formation of a quasi-transverse collisionless shock wave in a multi-component plasma. We show that in a plasma with a significant admixture of cold heavy ions, a specific MHD mode can be excited. This mode plays the same role for the collisionless shock formation as a quasi-transverse fast magnetosonic wave in a plasma with one sort of ions. As a result of this mode excitation, the solar wind velocity threshold for the formation of a collisionless shock becomes significantly less than in the case of a plasma with only light ions. We derive a nonlinear differential equation which describes a shock wave when perturbations become strong enough. Based on our theoretical results, we argue that upstream of the magnetic pile-up region of Mars or Venus, an additional shock wave may be formed