Scope 35: Scales and global change: Spatial and temporal variability in biospheric and geospheric process edited by T. Rosswall,R. G. Woodmansee,P. G. and Risser,Chichester, John wiley, 1988. No. of pages: 355. Price: £50. ISBN 0-471-91828-8     

J. G. Lockwood 《地球表面变化过程与地形》1990,15(4):383-383

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EISCAT observations of unusual flows in the morning sector associated with weak substorm activity     

N. J. Fox  M. Lockwood  S. W. H. Cowley  M. P. Freeman  E. Friis-Christensen  D. K. Milling  M. Pinnock  G. D. Reeves 《Annales Geophysicae》1994,12(6):541-553

A discussion is given of plasma flows in the dawn and nightside high-latitude ionospheric regions during substorms occurring on a contracted auroral oval, as observed using the EISCAT CP-4-A experiment. Supporting data from the PACE radar, Greenland magnetometer chain, SAMNET magnetometers and geostationary satellites are compared to the EISCAT observations. On 4 October 1989 a weak substorm with initial expansion phase onset signatures at 0030 UT, resulted in the convection reversal boundary observed by EISCAT (at \sim0415 MLT) contracting rapidly poleward, causing a band of elevated ionospheric ion temperatures and a localised plasma density depletion. This polar cap contraction event is shown to be associated with various substorm signatures; Pi2 pulsations at mid-latitudes, magnetic bays in the midnight sector and particle injections at geosynchronous orbit. A similar event was observed on the following day around 0230 UT (\sim0515 MLT) with the unusual and significant difference that two convection reversals were observed, both contracting poleward. We show that this feature is not an ionospheric signature of two active reconnection neutral lines as predicted by the near-Earth neutral model before the plasmoid is “pinched off”, and present two alternative explanations in terms of (1) viscous and lobe circulation cells and (2) polar cap contraction during northward IMF. The voltage associated with the anti-sunward flow between the reversals reaches a maximum of 13 kV during the substorm expansion phase. This suggests it to be associated with the polar cap contraction and caused by the reconnection of open flux in the geomagnetic tail which has mimicked “viscous-like” momentum transfer across the magnetopause.  相似文献   

The potential for catastrophic dam failure at Lake Nyos maar,Cameroon     

J. P. Lockwood  J. E. Costa  M. L. Tuttle  J. Nni  S. G. Tebor 《Bulletin of Volcanology》1988,50(5):340-349

The upper 40 m of Lake Nyos is bounded on the north by a narrow dam of poorly consolidated pyroclastic rocks, emplaced during the eruptive formation of the Lake Nyos maar a few hundred years ago. This 50-m-wide natural dam is structurally weak and is being eroded at an uncertain, but geologically alarming, rate. The eventual failure of the dam could cause a major flood (estimated peak discharge, 17000 m³/s) that would have a tragic impact on downstream areas as far as Nigeria, 108 km away. This serious hazard could be eliminated by lowering the lake level, either by controlled removal of the dam or by construction of a 680-m-long drainage tunnel about 65 m below the present lake surface. Either strategy would also lessen the lethal effects of future massive CO₂ gas releases, such as the one that occurred in August 1986.  相似文献   

Study of groundwater and soil moisture movement by applying nuclear,physical and chemical methods,H. Moser,W. Rauert,G. Morgenschweis,and H. Zojer internation hydrological programme,Unesco, Paris, 1986     

J. G. Lockwood 《地球表面变化过程与地形》1989,14(4):361-361

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Large-scale fields and flows in the magnetosphere-ionosphere system     

M. Lockwood 《Surveys in Geophysics》1995,16(3):389-441

Advances in our understanding of the large-scale electric and magnetic fields in the coupled magnetosphere-ionosphere system are reviewed. The literature appearing in the period January 1991–June 1993 is sorted into 8 general areas of study. The phenomenon of substorms receives the most attention in this literature, with the location of onset being the single most discussed issue. However, if the magnetic topology in substorm phases was widely debated, less attention was paid to the relationship of convection to the substorm cycle. A significantly new consensus view of substorm expansion and recovery phases emerged, which was termed the Kiruna Conjecture after the conference at which it gained widespread acceptance. The second largest area of interest was dayside transient events, both near the magnetopause and the ionosphere. It became apparent that these phenomena include at least two classes of events, probably due to transient reconnection bursts and sudden solar wind dynamic pressure changes. The contribution of both types of event to convection is controversial. The realisation that induction effects decouple electric fields in the magnetosphere and ionosphere, on time scales shorter than several substorm cycles, calls for broadening of the range of measurement techniques in both the ionosphere and at the magnetopause. Several new techniques were introduced including ionospheric observations which yield reconnection rate as a function of time. The magnetospheric and ionospheric behaviour due to various quasi-steady interplanetary conditions was studied using magnetic cloud events. For northward IMF conditions, reverse convection in the polar cap was found to be predominantly a summer hemisphere phenomenon and even for extremely rare prolonged southward IMF conditions, the magnetosphere was observed to oscillate through various substorm cycles rather than forming a steady-state convection bay.Reporter view, presented to Commission III of the International Association of Geomagnetism and Aeronomy at 7th IAGA Scientific Assembly, Buenos Aires, Argentina, August 1993.  相似文献   

The daily food intake of 0-group plaice (Pleuronectes platessa L.) under natural conditions   总被引：1，自引：0，他引：1  

Lockwood  Stephen J. 《ICES Journal of Marine Science》1980,39(2):154-159

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The recruitment of juvenile plaice (Pleuronectes platessa L.) to their parent spawning stock     

Lockwood  Stephen J.; Lucassen  Werner 《ICES Journal of Marine Science》1984,41(3):268-275

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Low-energy charged particle ring around equator in the altitude range 400–1100 km     

R. K. Kaul  H. Razdan  J. A. Lockwood 《Astrophysics and Space Science》1977,46(1):215-223

Measurements of charged particle fluxes at energies >-13 MeV (if protons), by means of a detector system of high geometrical factor (950 cm² sr), flown on OGO-6 satellite, reveals a ring of low energy charged particles around equator with fluxes of the order of 50–70 particles (m^–2 s^–1 sr^–1), in the altitude range of 400–1100 km. The ring of charged particles exists below the inner radiation belt and is restricted to ±4° of the geomagnetic equator. Distribution of the maximum flux with geomagnetic latitude andL is presented. Comparison of the observed fluxes with earlier measurements of low energy particles, reveals a differential energy spectrum of the type KE^– with the exponent nearly equal to 2.4 to 3.  相似文献   

Ionospheric and geomagnetic responses to changes in IMF B z : a superposed epoch study     

C. J. Davis  M. N. Wild  M. Lockwood  Y. K. Tulunay 《Annales Geophysicae》1997,15(2):217-230

Superposed epoch studies have been carried out in order to determine the ionospheric response at mid-latitudes to southward turnings of the interplanetary magnetic field (IMF). This is compared with the geomagnetic response, as seen in the indices K_p, AE and Dst. The solar wind, IMF and geomagnetic data used were hourly averages from the years 1967–1989 and thus cover a full 22-year cycle in the solar magnetic field. These data were divided into subsets, determined by the magnitudes of the southward turnings and the concomitant increase in solar wind pressure. The superposed epoch studies were carried out using the time of the southward turning as time zero. The response of the mid-latitude ionosphere is studied by looking at the F-layer critical frequencies, f_oF2, from hourly soundings by the Slough ionosonde and their deviation from the monthly median values, f_oF2. For the southward turnings with a change in B_z of B_z > 11.5 nT accompanied by a solar wind dynamic pressure P exceeding 5 nPa, the F region critical frequency, f_oF2, shows a marked decrease, reaching a minimum value about 20 h after the southward turning. This recovers to pre-event values over the subsequent 24 h, on average. The Dst index shows the classic storm-time decrease to about –60 nT. Four days later, the index has still to fully recover and is at about –25 nT. Both the K_p and AE indices show rises before the southward turnings, when the IMF is strongly northward but the solar wind dynamic pressure is enhanced. The average AE index does register a clear isolated pulse (averaging 650 nT for 2 h, compared with a background peak level of near 450 nT at these times) showing enhanced energy deposition at high latitudes in substorms but, like K_p, remains somewhat enhanced for several days, even after the average IMF has returned to zero after 1 day. This AE background decays away over several days as the Dst index recovers, indicating that there is some contamination of the currents observed at the AE stations by the continuing enhanced equatorial ring current. For data averaged over all seasons, the critical frequencies are depressed at Slough by 1.3 MHz, which is close to the lower decile of the overall distribution of f_oFl values. Taking 30-day periods around summer and winter solstice, the largest depression is 1.6 and 1.2 MHz, respectively. This seasonal dependence is confirmed by a similar study for a Southern Hemisphere station, Argentine Island, giving peak depressions of 1.8 MHz and 0.5 MHz for summer and winter. For the subset of turnings where B_z > 11.5 nT and P 5 nPa, the response of the geomagnetic indices is similar but smaller, while the change in f_oF2 has all but disappeared. This confirms that the energy deposited at high latitudes, which leads to the geomagnetic and ionospheric disturbances following a southward turning of the IMF, increases with the energy density (dynamic pressure) of the solar wind flow. The magnitude of all responses are shown to depend on B_z. At Slough, the peak depression always occurs when Slough rotates into the noon sector. The largest ionospheric response is for southward turnings seen between 15–21 UT.  相似文献   

The use of a modified Gulf V plankton sampler from a small open boat     

Lockwood  Stephen J. 《ICES Journal of Marine Science》1974,35(2):171-174

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