Response time of the high-latitude dayside ionosphere to sudden changes in the north-south component of the IMF     

H. Todd  S.W.H. Cowley  M. Lockwood  D.M. Willis  H. Lühr 《Planetary and Space Science》1988,36(12):1415-1428

The time scale of the response of the high-latitude dayside ionospheric flow to changes in the North-South component of the interplanetary magnetic field (IMF) has been investigated by examining the time delays between corresponding sudden changes. Approximately 40 h of simultaneous IMF and ionospheric flow data have been examined, obtained by the AMPTE-UKS and -IRM spacecraft and the EISCAT “Polar” experiment, respectively, in which 20 corresponding sudden changes have been identified. Ten of these changes were associated with southward turnings of the IMF, and 10 with northward turnings. It has been found that the corresponding flow changes occurred simultaneously over the whole of the “Polar” field-of-view, extending more than 2° in invariant latitude, and that the ionospheric response delay following northward turnings is the same as that following southward turnings, though the form of the response is different in the two cases. The shortest response time, 5.5 ± 3.2 min, is found in the early- to mid-afternoon sector, increasing to 9.5 ± 3.0 min in the mid-morning sector, and to 9.5 ± 3.1 min near to dusk. These times represent the delays in the appearance of perturbed flows in the “Polar” field-of-view following the arrival of IMF changes at the subsolar magnetopause. Overall, the results agree very well with those derived by Etemadi et al. (1988, Planet. Space Sci. 36, 471) from a general cross-correlation analysis of the IMF B_z and “Polar” beam-swinging vector flow data.  相似文献   

Ionospheric measurements of relative coronal brightness during the total solar eclipses of 11 August, 1999 and 9 July, 1945     

C. J. Davis  M. Lockwood  S. A. Bell  J. A. Smith  E. M. Clarke 《Annales Geophysicae》2000,18(2):182-190

Swept-frequency (1/10 MHz) ionosonde measurements were made at Helston, Cornwall (50°06N, 5°18W) during the total solar eclipse on August 11, 1999. Soundings were made every three minutes. We present a method for estimating the percentage of the ionising solar radiation which remains unobscured at any time during the eclipse by comparing the variation of the ionospheric E-layer with the behaviour of the layer during a control day. Application to the ionosonde date for 11 August, 1999, shows that the flux of solar ionising radiation fell to a minimum of 25±2% of the value before and after the eclipse. For comparison, the same technique was also applied to measurements made during the total solar eclipse of 9 July, 1945, at Sörmjöle (63°68N, 20°20E) and yielded a corresponding minimum of 16 ± 2%. Therefore the method can detect variations in the fraction of solar emissions that originate from the unobscured corona and chromosphere. We discuss the differences between these two eclipses in terms of the nature of the eclipse, short-term fluctuations, the sunspot cycle and the recently-discovered long-term change in the coronal magnetic field.  相似文献   

A numerical simulation of the effects of changing vegetation type on surface hydroclimatology     

Piers J. Sellers  John G. Lockwood 《Climatic change》1981,3(2):121-136

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THE RELATIONSHIP BETWEEN SOLAR FLARE GAMMA-RAY EMISSION AND NEUTRON PRODUCTION     

Lockwood  J. A.  Debrunner  H.  Ryan  J. M. 《Solar physics》1997,173(1):151-176

We have examined six solar neutron events measured by satellite instruments and/or neutron monitors (NM) to understand the relationship between the intensity–time profiles of the -ray lines, the pion-related -rays, and the neutron production. In all six events the solar neutron production was clearly time-extended. We find that neutron emission as detected by NMs most closely follows the emission of pion-related -rays, whereas lower energy neutron production may follow that of nuclear -ray line emissions. Although this distinction is not unexpected, it is safe to say that the 2.223 MeV -ray line from neutron capture on hydrogen is a poor measure of the neutron production at energies >200 MeV. During the three events on 1982, June 3, 1990, May 24 and 1991, June 4 solar neutrons with energies greater than 200 MeV were recorded by NMs. The NM increases on 1982, June 3 and 1990, May 24 can be modeled using the time profile of the pion-related -rays. For the 1991, June 4 event the NM signal was small but lasted for 60 min and the high-energy -ray data available to us are insufficient to conclude unambiguously that the high-energy neutron production followed the pion-related -rays. In the other three events on 1991, June 9, 11, and 15 solar neutrons with energies 10–100 MeV were observed by the COMPTEL -ray instrument on the Compton Gamma Ray Observatory. The duration of the low-energy neutron production on 1991, June 9 corresponded clearly to the high-energy and not to the low-energy -ray emission.  相似文献   

Millennium geology projects     

Austin Lockwood 《Geology Today》1999,15(3):103-104

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New cloud activity on Uranus in 2004: First detection of a southern feature at 2.2 μm     

H.B. Hammel  I. de Pater  G.W. Lockwood 《Icarus》2005,175(1):284-288

On 4 July 2004 UT, we detected one of Uranus' southern hemispheric cloud features at K′ (2.12 μm); this is the first such detection in half a decade of adaptive optics imaging of Uranus at the Keck 10-m telescope. When we observed again on 8 July UT the feature's bright core had faded. By 9 July UT it was not seen at K′ and barely detectable at H. The detection and subsequent disappearance of the feature indicates rapid dynamical processes in the localized vertical aerosol structure.  相似文献   

Does the framing of climate policies make a difference to public support? Evidence from UK marginal constituencies     

Matthew Lockwood 《Climate Policy》2013,13(4):1097-1112

Public support for climate policies is essential to underpin their credibility, but evidence suggests that an environmental basis for that support is not strong. It has been suggested that framing climate policies in other terms, such as energy security or job creation, will build a more sustainable political basis for bold climate policies. This approach is explored using data from a survey in 157 UK marginal constituencies. Framing does make a difference to support for the expansion of renewable energy, but not to support for policies on energy efficiency and financial assistance to developing countries. The data also show key differences in levels of support for policies between different socio-demographic and voter groups.  相似文献   

Connecting atmospheric science and atmospheric models for aerocapture at Titan and the outer planets     

C.G. Justus  Vernon W. Keller  Mary Kae Lockwood 《Planetary and Space Science》2005,53(5):601-605

Many atmospheric measurement systems, such as the sounding instruments on Voyager, gather atmospheric information in the form of temperature versus pressure level. In these terms, there is considerable consistency among the mean atmospheric profiles of the outer planets Jupiter through Neptune, including Titan. On a given planet or on Titan, the range of variability of temperature versus pressure level due to seasonal, latitudinal, and diurnal variations is also not large. However, many engineering needs for atmospheric models relate not to temperature versus pressure level but atmospheric density versus geometric altitude. This need is especially true for design and analysis of aerocapture systems. Drag force available for aerocapture is directly proportional to atmospheric density. Available aerocapture “corridor width” (allowable range of atmospheric entry angle) also depends on height rate of change of atmospheric density, as characterized by density scale height. Characteristics of hydrostatics and the gas law equation mean that relatively small systematic differences in temperature versus pressure profiles can integrate at high altitudes to very large differences in density versus altitude profiles. Thus, a given periapsis density required to accomplish successful aerocapture can occur at substantially different altitudes (∼150-300 km) on the various outer planets, and significantly different density scale heights (∼20-50 km) can occur at these periapsis altitudes. This paper will illustrate these effects and discuss implications for improvements in atmospheric measurements to yield significant impact on design of aerocapture systems for future missions to Titan and the outer planets. Relatively small-scale atmospheric perturbations, such as gravity waves, tides, and other atmospheric variations can also have significant effect on design details for aerocapture guidance and control systems. This paper will discuss benefits that would result from improved understanding of Titan and outer planetary atmospheric perturbation characteristics. Details of recent engineering-level atmospheric models for Titan and Neptune will be presented, and effects of present and future levels of atmospheric uncertainty and variability characteristics will be examined.  相似文献   

Thermal ion flows in the topside auroral ionosphere and the effects of low-altitude,transverse acceleration     

M. Lockwood 《Planetary and Space Science》1982,30(6):595-609

Topside ionospheric profiles are used to study the upward field-aligned flow of thermal O⁺ at high latitudes. On the majority of the field lines outside the plasmasphere, the mean flux is approximately equal to the mean polar wind measured by spacecraft at greater altitudes. This is consistent with the theory of thermal light ion escape supported, via charge exchange, by upward O⁺ flow at lower heights. Events of larger O⁺ flow are detected at auroral latitudes and their occurrence is found to agree with that of transversely accelerated ions within the topside ionosphere and the magnetosphere. The effects of low altitude heating of O⁺ by oxygen cyclotron waves, driven by downward field-aligned currents, are considered as a possible common cause of these two types of event.  相似文献   

Fish stock assessment a manual of basic methods: J.A. Gulland FAO/Wiley Series on Food and Agriculture,Vol 1, Wiley-lnterscience,Chichester, UK, 1983, 223 pp, £15.95     

Stephen J. Lockwood 《Marine Policy》1984,8(1):68-69

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