Results 221 to 230 of about 689,548 (248)

Nighttime equatorial Pi 2 micropulsations

Journal of Geophysical Research, 1969
The analysis of nighttime Pi 2 micropulsations recorded at Colombo, over an uninterrupted period of one year from October 17, 1964, to October 16, 1965, indicates that (1) Pi 2 events are most prominent, especially about midnight, during the equinoxes; (2) the rate of occurrence of Pi 2 events increases almost linearly with Kp up to a Kp level of at ...
M. L. T. Kannangara, P. C. B. Fernando
openaire   +1 more source

Statistical study of the polarisation of Pi 2 micropulsations

Journal of Atmospheric and Terrestrial Physics, 1973
The polarisation, properties of Pi 2 micropulsations are studied at certain 'low', 'middle', and 'high' latitude sites, and it is shown that left-hand polarised signals predominate at the low and high latitudes, whilst neither sense of polarisation is preferred at the middle latitude.
Doobov A.L., Mainstone J.S.
openaire   +3 more sources

Pi 2 pulsations and the westward traveling surge

Journal of Geophysical Research: Space Physics, 1986
A model is developed that relates the poleward leaps of the westward traveling surge (WTS) and the generation of Pi 2 pulsations. The feedback instability developed by Sato and coworkers is combined with the dynamic surge model of Rothwell et al. (1984).
Paul L. Rothwell, Michael B. Silevitch, Lars P. Block   +2 more
openaire   +1 more source

A transient‐response theory of Pi 2 pulsations

Journal of Geophysical Research: Space Physics, 1985
The cause of Pi 2 pulsations at substorm onset can be understood in terms of the transient ionospheric response to an enhanced convection in the plasma sheet. A two‐dimensional model is presented to demonstrate how the transient ionospheric response can lead to damped oscillations similar to the Pi 2 pulsations observed at substorm onset.
W. Sun, J. R. Kan
openaire   +1 more source

The Perimeter and Area of Reduced Spherical Polygons of Thickness $$\pi /2$$

Results in Mathematics, 2020
The authors focus on the following conjectures on perimeter and area of reduced spherical polygons, formulated by \textit{M. Lassak} [Colloq. Math. 138, No. 2, 205--216 (2015; Zbl 1316.52017)]: \begin{itemize} \item[``(1)] The perimeter of every reduced spherical polygon is less than or equal to that of the regular spherical triangle of the same ...
Yanxun Chang, Cen Liu, Zhanjun Su
openaire   +1 more source

A transient response model of Pi 2 pulsations

Journal of Geophysical Research: Space Physics, 1982
A transient response model of Pi 2 pulsations due to an enhanced convection in the plasma sheet is presented. A nonlinear Alfvén wave is launched by the enhanced convection electric field. The reflection coefficient at the ionosphere is derived by matching the field‐aligned current of the Alfvén wave to the field‐aligned current from the divergence of ...
Joseph R. Kan, David U. Longenecker, John V. Olson   +2 more
openaire   +1 more source

Vier Mal $$ \frac{{\pi^{2} }}{6} $$

2018
Die Summe der Reziproken der Quadratzahlen konvergiert, wenn auch nur sehr langsam, wie wir sehen werden, und sie ergibt einen interessanten Wert.
Martin Aigner, Günter M. Ziegler
openaire   +1 more source

A Raspberry Pi 2-based stereo camera depth meter

2017 Fifteenth IAPR International Conference on Machine Vision Applications (MVA), 2017
The Raspberry Pi single-board computer is a low cost, light weight system with small power requirements. It is an attractive embedded computer vision solution for many applications, including that of UAVs. Here, we focus on the Raspberry Pi 2 and demonstrate that, with the addition of a multiplexer and two camera modules, it is able to execute a full ...
James Cooper, Mihailo Azhar, Trevor Gee, Wannes van der Mark, Patrice Delmas, Georgy L. Gimel'farb   +5 more
openaire   +1 more source

Right triangular dihedral f-tilings of the sphere: (a, b, pi/2) and (c, c, pi/2)

2015
The classification of all dihedral f-tilings of the Riemannian sphere S2, whose prototiles are two right triangles with at least one isosceles, is given. The combinatorial structure and the symmetry group of each tiling is also achieved.
Avelino, Catarina Pina, Santos, Altino
openaire   +1 more source

Related investigations of pi 2 micropulsations

2011
Related investigations of irregular, nighttime, type Pi 2 micropulsations were undertaken with regards to the source and occurrence of these geomagnetic fluctuations. In particular, the local times of Pi 2's recorded by a global network of stations, during 1964, were determined.
openaire   +1 more source