Magnetic flux emergence in fast rotating stars

Fast rotating cool stars are characterised by high magnetic activity levels and frequently show dark spots up to polar latitudes. Their distinctive surface distributions of magnetic flux are investigated in the context of the solar-stellar connection by applying the solar flux eruption and surface flux transport models to stars with different rotation rates, mass, and evolutionary stage. The rise of magnetic flux tubes through the convection zone is primarily buoyancy-driven, though their evolution can be strongly affected by the Coriolis force. The poleward deflection of the tube's trajectory increases with the stellar rotation rate, which provides an explanation for magnetic flux eruption at high latitudes. The formation of proper polar spots likely requires the assistance of meridional flows both before and after the eruption of magnetic flux on the stellar surface. Since small radiative cores support the eruption of flux tubes at high latitudes, low-mass pre-main sequence stars are predicted to show high mean latitudes of flux emergence. In addition to flux eruption at high latitudes, main sequence components of close binary systems show spot distributions which are non-uniform in longitude. Yet these `preferred longitudes' of flux eruption are expected to vanish beyond a certain post-main sequence evolutionary stage.Comment: 8 pages, 12 figures, in Memorie della Societa Astronomica Italiana Vol. 78 n. 2, p. 27

Thoughts about recent education reform in India: Is there a tendency towards privatisation in elementary education?

The debate in India about the Right to Education Bill 2005 is an example for the basic question in education reform: Is education to be provided by the state or by private actors? With this bill the Government of India (GoI) suggests it\u27s programme to implement the "right to education", which has become the 86th amendment to the constitution in 2002. It guarantees free and compulsory education for all children in the age of 6-14. There is a rapid increase in private initiative in order to fill insufficient government provision of quality education. But is the state enforcing privatisation of education? The debate about the Right to Education Bill shows an ambivalent attitude of the GoI towards private schools: They are seen as a means to achieve Education for All through a reservation policy for children from low socio-economic strata on the one hand and tries to control them more in order to decrease the number of unrecognised schools. Critics of the current education policy accuse the GoI of a lack of strength to create a common school system, in their view the only way to make the constitutional right a reality. On this backdrop the article discusses statements in favour and against an increasing role of private actors in education and concludes that the noble idea of a right to education as amended to the constitution can not be fulfilled if the state does not take its primary responsibility for the provision of quality education to every child serious. (DIPF/Orig.)Die Debatte in Indien anlässlich der "Right to Education Bill 2005" ist ein Beispiel für eine Auseinandersetzung über eine grundlegende Frage der Bildungsreform: Ist es der Staat oder sind es private Akteure die für Bildung verantwortlich sind? Die neue Gesetzesvorlage skizziert das Programm zur Umsetzung des Rechts auf Bildung. Dieses Recht wurde 2002 in die Verfassung aufgenommen und garantiert jedem Kind im Alter von 6-14 Jahren frei zugängliche Bildung unter einer allgemeinen Schulpflicht. Gleichzeitig wächst die Zahl der privaten Schulen immer weiter, vor allem dort wo der Staat keine qualitativ hochwertige Bildung anbietet. Heißt das, dass der Staat sich in die Richtung einer Privatisierung der Bildung bewegt? Die Debatte zeigt, dass der indische Staat eine ambivalente Haltung gegenüber den privaten Schulen einnimmt: Auf der einen Seite werden sie als ein Weg gesehen "Education For All" zu erreichen. Das zeigt die angedachte Regelung der Reservierung von Plätzen in Privatschulen für Kinder aus ärmeren Familien. Auf der anderen Seite sieht der Entwurf eine stärkere Kontrolle über die privaten Träger vor, um die Zahl der Privatschulen, die ohne staatliche Anerkennung arbeiten, zu verringern. KritikerInnen dieser Pläne der Regierung fordern die Einführung eines allgemeinen Schulsystems zur Überwindung der Stratifikation, die durch die verschiedenen Schulen verstärkt wird. Vor diesem Hintergrund zeigt der Artikel das Für und Wider einer Aktivität von Privatschulen auf und kommt zu dem Schluss, dass die noble Idee eines "Rechts auf Bildung" nur umgesetzt werden kann, wenn der Staat seine eigentliche Verantwortung für Bildung ernst nimmt. (DIPF/Orig.

Dynamics of magnetic flux tubes in close binary stars I. Equilibrium and stability properties

Surface reconstructions of active close binary stars based on photometric and spectroscopic observations reveal non-uniform starspot distributions, which indicate the existence of preferred spot longitudes (with respect to the companion star). We consider the equilibrium and linear stability of toroidal magnetic flux tubes in close binaries to examine whether tidal effects are capable to initiate the formation of rising flux loops at preferred longitudes near the bottom of the stellar convection zone. The tidal force and the deviation of the stellar structure from spherical symmetry are treated in lowest-order perturbation theory assuming synchronised close binaries with orbital periods of a few days. The frequency, growth time, and spatial structure of linear eigenmodes are determined by a stability analysis. We find that, despite their small magnitude, tidal effects can lead to a considerable longitudinal asymmetry in the formation probability of flux loops, since the breaking of the axial symmetry due to the presence of the companion star is reinforced by the sensitive dependence of the stability properties on the stellar stratification and by resonance effects. The orientation of preferred longitudes of loop formation depends on the equilibrium configuration and the wave number of the dominating eigenmode. The change of the growth times of unstable modes with respect to the case of a single star is very small.Comment: 11 pages, 11 figures, accepted for publication in A&

On the physics behind the form factor ratio μpGEp(Q2)/GMp(Q2)\mu_p G_E^p (Q^2) / G_M^p (Q^2)

We point out that there exist two natural definitions of the nucleon magnetization densities : the density $\rho_M^K (r)$ introduced in Kelly's phenomenological analysis and theoretically more standard one $\rho_M (r)$. We can derive an explicit analytical relation between them, although Kelly's density is more useful to disentangle the physical origin of the different $Q^2$ dependence of the Sachs electric and magnetic form factors of the nucleon. We evaluate both of $\rho_M (r)$ and $\rho_M^K (r)$ as well as the charge density $\rho_{ch}(r)$ of the proton within the framework of the chiral quark soliton model, to find a noticeable qualitative difference between $\rho_{ch}(r)$ and $\rho_M^K (r)$, which is just consistent with Kelly's result obtained from the empirical information on the Sachs electric and magnetic form factors of the proton.Comment: 12 pages, 5 figures. version to appear in J. Phys. G.: Nucl. Part. Phy