The climatic conditions in the Arctic, and observations of the wind-induced drift of ice made in connexion with Fridtjof Nansen’s Fram expedition, led to the discovery 100 years ago by Vilhelm Bjerknes’ pupil, V.W. Ekman, of the importance of the Earth’s rotation in limiting the depth of the wind-induced shear current in the ocean. This essay commemorates the centenary of Ekman’s seminal paper,...

We consider a random walk on the discrete cylinder (Z/NZ)×Z, d ≥ 3 with drift N in the Z-direction and investigate the large N -behavior of the disconnection time T disc N , defined as the first time when the trajectory of the random walk disconnects the cylinder into two infinite components. We prove that, as long as the drift exponent α is strictly greater than 1, the asymptotic behavior of T...

Recent results regarding subpulse-drift in pulsar B0943+10 have led to the identification of a stable system of sub-beams circulating around the magnetic axis of the star. Here, we present single-pulse analysis of pulsar B0834+06 at 35 MHz, using observations from the Gauribidanur Radio Telescope. Certain signatures in the fluctuation spectra and correlations allow estimation of the circulation...

The drift velocity of an auroral arc is compared with the component of F-region plasma velocity in the same direction for ten cases where the arc is seen to move steadily equatorward for several minutes without any major change in appearance or orientation. In most cases the two velocities are close, but on two occasions the drift velocity of the arc is much higher than the plasma velocity. Fro...

We consider a random walk on the discrete cylinder (Z/NZ)d×Z, d ≥ 3 with drift N−dα in the Z-direction and investigate the large N -behavior of the disconnection time T disc N , defined as the first time when the trajectory of the random walk disconnects the cylinder into two infinite components. We prove that, as long as the drift exponent α is strictly greater than 1, the asymptotic behavior ...

The mean electromotive force is considered in a differentially rotating fluid taking into account stretching of the turbulent magnetic field. Calculations are performed by making use of the second order correlation approximation. Nonuniformity of the angular velocity leads to specific drift processes in the azimuthal direction. Due to this drift the magnetic field can rotate with a somewhat dif...

Neurons in area MT/V5 of the macaque visual cortex encode visual motion. Some cells are selective for the motion of oriented features (component direction-selective, CDS); others respond to the true direction of complex patterns (pattern-direction selective, PDS). There is a continuum of selectivity in MT, with CDS cells at one extreme and PDS cells at the other; we compute a pattern index that...

Tearing mode stability analysis in the presence of circulating energetic ions (CEI) is studied in the reversed field pinch (RFP) magnetic configuration. In contrast to the minimal effect of precessional drift of CEI on tearing modes in tokamaks, the effect of precessional drift of CEI on tearing modes is important in the RFP. It is found that the effects of CEI on tearing modes in RFP depend on...

An outline of the analysisof thestochastic dynamics of the blind adaptation of deckion fcedbadr equalizers (DFEs) operating on noiselm, binary commuuication channels is presented. The general mech.anism whereby the blind adaptation is flawed in the sense that thae Bdst attraction points in parmeter space which lead to unequalLed systems is detined and c l d e d with an exnmple. This bchaviour i...

The discovery of speed-modulated grid, head direction, and conjunctive grid x head direction cells in the medial entorhinal cortex has led to the hypothesis that path integration, the updating of one's spatial representation based on movement, may be carried out within this region. This hypothesis has been formalized by many computational models, including a class known as attractor network mod...