29Th-order harmonics in the geopotential from the orbit of ariel 1 at 29: 2 resonance

In analysing the orbit of Ariel 1 to determine upper-atmosphere winds, it was observed that the orbital inclination underwent a noticeable perturbation in November 1969 at the 29:2 resonance with the Earth's gravitational field, when the satellite track over the Earth repeats every 2 days after 29 revolutions. The variations in the inclination and eccentricity of the orbit between July 1969 and February 1970 have now been analysed, using 35 US Navy orbits, and fitted with theoretical curves to obtain lumped values of 29th-order harmonic coefficients in the geopotential.     

Intercalibration of airglow observatories with the atmosphere explorer satellite

The visible airglow photometer on the Atmosphere Explorer C Satellite has been used to compare the calibrations of a number of ground-based airglow observatories. Discrepancies between different ground stations as large as a factor of six have been revealed. Efforts to account for these discrepancies have resulted in the discovery of differences as large as a factor of 2 in the standard light sources in use at different observatories. The participation of additional observatories in the intercomparison of standard sources is solicited. The project has also led to the discovery of a source of error that can amount to another factor of 2 in the procedure used to calibrate many airglow instruments. In the course of the project detailed maps, based on satellite data, have been made of the galactic and zodiacal light background at a number of wavelengths, and a substantial source of contaminating emission has been discovered in the satellite data; the contamination appears to result from interaction of the spacecraft and the atmosphere at altitudes below 170 km.     

Comparison of electrical conductivities in the E-AND F-regions of the nocturnal ionosphere

Experimental results from Arecibo indicate that on the average the height integrated F-region Pedersen conductivity is slightly greater than the height integrated E-region Pedersen conductivity, while the height integrated Hall conductivity exceeds either of the Pedersen conductivities by a factor of about 2. However, the conductivities can differ substantially from the average values on any given night.     

Upper-atmosphere rotation rate from analysis of the orbital inclination of explorer 1

Explorer 1, 1958α, ths first U.S. artificial satellite, was launched on 1 February 1958 and remained in orbit for 12 years. In this paper theoretical curves have been fitted to the values of inclination, giving three values of the average atmospheric rotation rate at heights of 350–400 km, and latitudes 0–20°:

     

665.

The distribution of Fe and Mg between olivine and lunar basaltic liquids     

John Longhi  David Walker  James F. Hays 《Geochimica et cosmochimica acta》1978,42(10):1545-1558

We have examined the Fe and Mg distribution between coexisting olivine and lunar basaltic liquids produced by equilibrium partial melting of natural lunar samples. In agreement with the findings of Roeder and Emslie (Contrib. Mineral. Petrol. 29, 275–289) on terrestrial compositions, the logarithms of the conventional distribution coefficients, K_ol-L^Fe and K_ol-L^Fe-Mg, are nearly linear functions of inverse temperature; and the exchange coefficient, K_D = K_ol-L^Fe-Mg, is nearly independent of temperature and composition within a given magma group. There are, however, small but significant differences in conventional and exchange distribution coefficients from one magma group to another, e.g. low-Ti vs high-Ti lunar basalts. It is possible to achieve slightly greater precision for the inverse temperature functions by including terms approximating silica activity in the conventional distribution coefficients. The term ($\text{2Si}\text{O}\text{)}{}_{\mathrm{L}}$ is apparently the best simple approximation for silica activity in olivine-saturated liquids based upon data for Fe, Mg, Mn, Ca, Ti and Cr. Pressure has noticeable effects upon Fe and Mg distribution between olivine and liquid only above 5 kbar.The excellent linear correlation of the logarithms of the distribution coefficients with inverse temperature allows calculation of approximate values of $\text{Δ}\text{H}\text{?}{}^0$ for the reactions : 2MgO_L + SiO_2LaiMg₂SiO_4ol and 2FeO_L + SiO_2LaiFe₂SiO_4ol. Values obtained, approx ?26 kcal/mole, are comparable with values of the heats of fusion of forsterite and fayalite calculated by Bradley (Am. J. Sci.260, 550–554) and measured by Orr (J. Am. Chem. Soc. 75, 528–529).The exchange distribution coefficient for Fe and Mg, K_D, is sensitive to large changes in liquid chemistry. Although K_D is explicitly independent of silica activity, K_D apparently changes with silica concentration. This change is a reflection of changes in the mixing properties of Fe and Mg in liquids with different chemistry and hence structure. Regular solution theory predicts that as the mixing properties of an element in a solution change, the most radical changes in activity coefficients occur in the range of dilute concentrations. Therefore, the distribution coefficients for trace elements will also be dependent upon large changes in liquid chemistry, even if corrections for silica and other liquid component activities are applied.     

666.

Evaluation of 14th-order harmonics in the geopotential     

D.G. King-Hele  Doreen M.C. Walker  R.H. Gooding 《Planetary and Space Science》1979,27(1):1-18

The Earth's gravitational potential is now usually expressed in terms of a double series of tesseral harmonics with several hundred terms, up to order and degree at least 20. The harmonics of order 14 can be evaluated by analysing changes in satellite orbits which experience 14th-order resonance, when the track over the Earth repeats after 14 revolutions.In this paper we describe our first evaluation of individual 14th-order coefficients in the geopotential from analysis of the variations in inclination and eccentricity of satellite orbits passing through 14th-order resonance under the action of air drag. Using results from eleven satellites, we find the following values for normalized coefficients of harmonics of order 14 and degree l, C?_{l, 14} and S?_{l, 14}, for l=14, 154. 22:

Feb 1958 to mid 1960	1.5 rev/day
Mid 1960 to Dec 1967	1.2 rev/day
Jan 1968 to Mar 1970	1.3 rev/day

     

667.

Luminescence dating of the last earthquake of the Sabzevar thrust fault, NE Iran     

Morteza Fattahi  Richard T. Walker 《Quaternary Geochronology》2007,2(1-4):284-289

Iran is one of the world's most tectonically active regions, yet dating past earthquakes for neotectonic studies has been limited. One of the main reasons for this is that organic material suitable for radiocarbon dating of deformed sediments is rare. We investigate the use of infrared stimulated luminescence (IRSL) from coarse-grained feldspars to date colluvial deposits associated with the Sabzevar thrust fault in northeastern Iran. The single-aliquot regenerative (SAR) dose measurement procedure was used for this study. The current study investigates monitoring and correcting for sensitivity changes, recovering a known laboratory dose and equivalent dose estimation using three SAR IRSL methods. It is shown that SAR has recovered a given laboratory dose using a range of preheat temperatures but D_e determination of natural samples requires its own preheat plateaus for two of these SAR methods. The SAR IRSL method provided an age of 1.7±0.3 ka for colluvium, predating the last earthquake event on the Sabzevar fault. This result suggests that this fault is likely to be responsible for an earthquake that destroyed Sabzevar city in AD 1052.     

668.

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions   总被引：2，自引：0，他引：2  

G. Chisham  M. Lester  S. E. Milan  M. P. Freeman  W. A. Bristow  A. Grocott  K. A. McWilliams  J. M. Ruohoniemi  T. K. Yeoman  P. L. Dyson  R. A. Greenwald  T. Kikuchi  M. Pinnock  J. P. S. Rash  N. Sato  G. J. Sofko  J.-P. Villain  A. D. M. Walker 《Surveys in Geophysics》2007,28(1):33-109

     

669.

Seismological and field observations from the 1990 November 6 Furg (Hormozgan) earthquake: a rare case of surface rupture in the Zagros mountains of Iran     

Richard T. Walker  M. J. Andalibi  M. R. Gheitanchi  J. A. Jackson  S. Karegar  K. Priestley 《Geophysical Journal International》2005,163(2):567-579

     

670.

Shear-wave splitting around the Eifel hotspot: evidence for a mantle upwelling   总被引：1，自引：0，他引：1  

K. T. Walker  G. H. R. Bokelmann †  S. L. Klemperer  G. Bock ‡ 《Geophysical Journal International》2005,163(3):962-980

     

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$\text{l}$	109C?$\text{l,14}$	109S?l,14
-	-	-
14	?38.5 ±2.9	?7.8 ±2.2
15	4.5 ±1.1	?23.8 ±0.3
16	?22.3 ±3.6	?36.0 ±3.8
17	?15.0 ±2.6	16.8 ±1.2
18	?24.0±4.9	?3.2 ±3.7
19	?1.6 ±2.8	?7.6 ±1.0
20	8.8 ±5.8	?15.4 ±4.6
21	18.2 ±3.6	?10.6 ±1.9
22	?14.5 ±8.1	9.9 ±6.4

The distribution of Fe and Mg between olivine and lunar basaltic liquids

We have examined the Fe and Mg distribution between coexisting olivine and lunar basaltic liquids produced by equilibrium partial melting of natural lunar samples. In agreement with the findings of Roeder and Emslie (Contrib. Mineral. Petrol. 29, 275–289) on terrestrial compositions, the logarithms of the conventional distribution coefficients, K_ol-L^Fe and K_ol-L^Fe-Mg, are nearly linear functions of inverse temperature; and the exchange coefficient, K_D = K_ol-L^Fe-Mg, is nearly independent of temperature and composition within a given magma group. There are, however, small but significant differences in conventional and exchange distribution coefficients from one magma group to another, e.g. low-Ti vs high-Ti lunar basalts. It is possible to achieve slightly greater precision for the inverse temperature functions by including terms approximating silica activity in the conventional distribution coefficients. The term ($\text{2Si}\text{O}\text{)}{}_{\mathrm{L}}$ is apparently the best simple approximation for silica activity in olivine-saturated liquids based upon data for Fe, Mg, Mn, Ca, Ti and Cr. Pressure has noticeable effects upon Fe and Mg distribution between olivine and liquid only above 5 kbar.The excellent linear correlation of the logarithms of the distribution coefficients with inverse temperature allows calculation of approximate values of $\text{Δ}\text{H}\text{?}{}^0$ for the reactions : 2MgO_L + SiO_2LaiMg₂SiO_4ol and 2FeO_L + SiO_2LaiFe₂SiO_4ol. Values obtained, approx ?26 kcal/mole, are comparable with values of the heats of fusion of forsterite and fayalite calculated by Bradley (Am. J. Sci.260, 550–554) and measured by Orr (J. Am. Chem. Soc. 75, 528–529).The exchange distribution coefficient for Fe and Mg, K_D, is sensitive to large changes in liquid chemistry. Although K_D is explicitly independent of silica activity, K_D apparently changes with silica concentration. This change is a reflection of changes in the mixing properties of Fe and Mg in liquids with different chemistry and hence structure. Regular solution theory predicts that as the mixing properties of an element in a solution change, the most radical changes in activity coefficients occur in the range of dilute concentrations. Therefore, the distribution coefficients for trace elements will also be dependent upon large changes in liquid chemistry, even if corrections for silica and other liquid component activities are applied.     

Evaluation of 14th-order harmonics in the geopotential

The Earth's gravitational potential is now usually expressed in terms of a double series of tesseral harmonics with several hundred terms, up to order and degree at least 20. The harmonics of order 14 can be evaluated by analysing changes in satellite orbits which experience 14th-order resonance, when the track over the Earth repeats after 14 revolutions.In this paper we describe our first evaluation of individual 14th-order coefficients in the geopotential from analysis of the variations in inclination and eccentricity of satellite orbits passing through 14th-order resonance under the action of air drag. Using results from eleven satellites, we find the following values for normalized coefficients of harmonics of order 14 and degree l, C?_{l, 14} and S?_{l, 14}, for l=14, 154. 22:

Luminescence dating of the last earthquake of the Sabzevar thrust fault, NE Iran

Iran is one of the world's most tectonically active regions, yet dating past earthquakes for neotectonic studies has been limited. One of the main reasons for this is that organic material suitable for radiocarbon dating of deformed sediments is rare. We investigate the use of infrared stimulated luminescence (IRSL) from coarse-grained feldspars to date colluvial deposits associated with the Sabzevar thrust fault in northeastern Iran. The single-aliquot regenerative (SAR) dose measurement procedure was used for this study. The current study investigates monitoring and correcting for sensitivity changes, recovering a known laboratory dose and equivalent dose estimation using three SAR IRSL methods. It is shown that SAR has recovered a given laboratory dose using a range of preheat temperatures but D_e determination of natural samples requires its own preheat plateaus for two of these SAR methods. The SAR IRSL method provided an age of 1.7±0.3 ka for colluvium, predating the last earthquake event on the Sabzevar fault. This result suggests that this fault is likely to be responsible for an earthquake that destroyed Sabzevar city in AD 1052.