The surface seiches of Lake of Lugano     

PD. Dr. K. Hutter  Dr. G. Raggio  PD. Dr. C. Bucher  Dr. G. Salvadè  Dr. F. Zamboni 《Aquatic Sciences - Research Across Boundaries》1982,44(2):455-484

A computational analysis of the periods and structure of surface seiches of the southern basin of Lake of Lugano and its experimental verification from three simultaneous water gauge recordings, mounted along the shores in Agno, Morcote and Riva S. Vitale, is given. The first five theoretical modes are calculated with a finite element code of the tidal equations; it yields the eigenperiods and co-range and co-tidal lines, which are graphically displayed and discussed in detail. Experimental verification is from recordings taken during February/March 1982. Inspection by eye allows identification of the five lowest order modes, partly including interstation phase shift. Power spectral analysis of three-time series and interstation phase difference and coherence spectra allow identification of higher order modes, probably up to order 13. Agreement between the theoretically predicted and the experimentally determined periods is excellent for all calculated modes. Computational results for the four lowest modes and their structure of the northern basin of Lake of Lugano are also presented and experimentally verified with records taken from an event in August 1979. Agreement is again excellent.  相似文献   

Physics of magnetospheric substorms: S.-I. Akasofu: Reidel Publishing Co., Dordrecht,Holland, 1977, xviii + 599. Dfl. 140. U.S. $54.00     

S.W.H. Cowley 《Planetary and Space Science》1977,25(10):989

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Equilibrium and Stability of Prominence Flux Ropes     

Bryan H. Fong  Omar A. Hurricane  Steven C. Cowley 《Solar physics》2001,201(1):93-117

Realistic models of solar prominence flux ropes are numerically constructed. The models are in 2.5 dimensions, including the effects of non-isothermal temperature, density and gravity, and pressure. Stability of the equilibria to pressure- and gravity-driven instabilities is numerically investigated, using the ballooning formalism of fusion plasma theory. The equilibrium models can become unstable to pressure- and gravity-driven modes at plasma parameters characteristic of prominences.  相似文献   

The ionospheric electric field during substorms — An interpretation based on non-uniform reconnection in the geomagnetic tail     

S. W. H. Cowley 《Astrophysics and Space Science》1973,20(2):491-497

It is suggested that changes in the electric field in the night-side auroral zone and polar cap observed during the expansion phase of a substorm are related to a change in the magnetospheric flow pattern. During the substorm growth phase the flow appears to be fairly uniform across the width of the magnetosphere (uniform electric field across the tail), while at expansion the observations are consistent with the magnetospheric potential drop in the tail falling across a narrow region near the dusk magnetopause. Such non-uniform electric fields in the tail have been predicted by recent theoretical work. A rather speculative interpretation of events during a magnetospheric substorm is presented.  相似文献   

The absence of electric fields due to particle entry into the magnetosphere     

D.B. Beard  S.W.H. Cowley 《Planetary and Space Science》1979,27(12):1523-1524

The wide-spread belief that the neutral sheet current in Earth's magnetotail creates an accumulation of charge at the boundary with the magnetosheath is erroneous. Current continuity is maintained by the magnetization current on the upper and lower surfaces of the magnetotail. Hence no electric fields arise from charge separation supposedly brought about by the flow of particles between the neutral sheet and the magnetosheath. Claims to the contrary are based on the oversight of forgetting the current on the magnetopause.  相似文献   

Wucherungen von Cyanophyceen an den Ufern des Zürichsees und deren Ursachen     

PD. Dr. E. A. Thomas 《Aquatic Sciences - Research Across Boundaries》1961,23(1):225-235

Ohne Zusammenfassung Nach einem Referat, gehalten am I. Internationalen Cyanophyceen-Symposium in Luzern, Kastanienbaum, 29.8.-3.9. 60.  相似文献   

Two-dimensional electric field measurements in the ionospheric footprint of a flux transfer event     

K. A. McWilliams  T. K. Yeoman  S. W. H. Cowley 《Annales Geophysicae》2001,18(12):1584-1598

Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the ionospheric footprint of a flux transfer event (a pulsed ionospheric flow, or PIF). Very stable and moderate interplanetary magnetic field conditions, along with a preceding prolonged period of northward interplanetary magnetic field, allow a detailed study of the spatial and the temporal evolution of the ionospheric response to magnetic reconnection. The flux tube footprint is tracked for half an hour across six hours of local time in the auroral zone, from magnetic local noon to dusk. The motion of the footprint of the newly reconnected flux tube is compared with the ionospheric convection velocity. Two primary intervals in the PIFs evolution have been determined. For the first half of its lifetime in the radar field of view the phase speed of the PIF is highly variable and the mean speed is nearly twice the ionospheric convection speed. For the final half of its lifetime the phase velocity becomes much less variable and slows down to the ionospheric convection velocity. The evolution of the flux tube in the magnetosphere has been studied using magnetic field, magnetopause and magnetosheath models. The data are consistent with an interval of azimuthally propagating magnetopause reconnection, in a manner consonant with a peeling of magnetic flux from the magnetopause, followed by an interval of anti-sunward convection of reconnected flux tubes.  相似文献   

Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field   总被引：1，自引：0，他引：1  

S. E. Milan  M. Lester  S. W. H. Cowley  M. Brittnacher 《Annales Geophysicae》2000,18(4):436-444

We investigate the dayside auroral dynamics and ionospheric convection during an interval when the interplanetary magnetic field (IMF) had predominantly a positive B_z component (northward IMF) but varying B_y. Polar UVI observations of the Northern Hemisphere auroral emission indicate the existence of a region of luminosity near local noon at latitudes poleward of the dayside auroral oval, which we interpret as the ionospheric footprint of a high-latitude reconnection site. The large field-of-view afforded by the satellite-borne imager allows an unprecedented determination of the dynamics of this region, which has not previously been possible with ground-based observations. The location of the emission in latitude and magnetic local time varies in response to changes in the orientation of the IMF; the cusp MLT and the IMF B_y component are especially well correlated, the emission being located in the pre- or post-noon sectors for B_y < 0 nT or B_y > 0 nT, respectively. Simultaneous ground-based observations of the ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar. For an interval of IMF B_y 0 nT, these convection flow measurements suggest the presence of a clockwise-rotating lobe cell contained within the pre-noon dayside polar cap, with a flow reversal closely co-located with the high-latitude luminosity region. This pattern is largely consistent with recent theoretical predictions of the convection flow during northward IMF. We believe that this represents the first direct measurement of the convection flow at the imaged location of the footprint of the high-latitude reconnection site.  相似文献   

From Small-Scale Dynamo to Isotropic MHD Turbulence     

Alexander A. Schekochihin  Steven C. Cowley  Samuel F. Taylor  Jason L. Maron  James C. McWilliams 《Astrophysics and Space Science》2004,292(1-4):141-146

We consider the problem of incompressible, forced, nonhelical, homogeneous, isotropic MHD turbulence with no mean magnetic field. This problem is essentially different from the case with externally imposed uniform mean field. There is no scale-by-scale equipartition between magnetic and kinetic energies as would be the case for the Alfvén-wave turbulence. The isotropic MHD turbulence is the end state of the turbulent dynamo which generates folded fields with small-scale direction reversals. We propose that the statistics seen in numerical simulations of isotropic MHD turbulence could be explained as a superposition of these folded fields and Alfvén-like waves that propagate along the folds.  相似文献   

Palaeomagnetic directions and pole positions — XV. Pole numbers 15/1 to 15/232     

M. W. McElhinny  J. A. Cowley 《Geophysical Journal International》1978,52(2):259-276

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