摘要:

The equations Ed= ½NJ² + const for demagnetizing energy and Hd= −NJ for average internal demagnetizing field (J is magnetization; N is demagnetizing factor, assumed constant) are central to multidomain (MD) theories of thermoremanence (TRM) and hysteresis. Theoretical calculations reported here, based on Rhodes and Rowlands' (1954) equations for Edof an MD cube, test the variation of N with the number n of domains and with domain wall displacement x. For n even, Ed(x) − Ed(0) is nearly proportional to x² or J², so that N is practically constant (to ≈ 20% if n = 2, ≈ 10% if n = 4 and ≈ 5% if n = 8) for 0 ≤ J ≤ Js. This result reaffirms the validity of traditional MD rock magnetic theories. However, if n is small, N is significantly less than 4 π/3 (the single‐domain or n → ∞ value); N ≈ 2 for n = 2 and (4π/3 − N) decreases as 1/n, so that N → 4π/3 when n = 8 or 10. Grains with n odd possess a spontaneous remanence even in the absence of wall pinning that is substantial (Jr≈ 0.1 Js) for n = 3 but decreases rapidly for larger n. This spontaneous remanence is a possible source of so‐called pseudo‐single‐doma

ISSN:0094-8276    

DOI:10.1029/GL010i001p00079

年代:1983

数据来源: WILEY

摘要:

The measured magnetic anisotropy and porosity of various chondrites are found to be inversely correlated when they are considered by class of chondrites (E, H and L + LL). For chondrites with similar porosities, the anisotropies for H and E chondrites are smaller than for L and LL chondrites, which have lower metal contents. The anisotropy and porosity are not dependent on the metamorphic grade of chondrites. K‐Ar ages of strongly anisotropic and/or less porous chondrites are younger than those of less anisotropic and/or more porous chondrites. These observations suggest that impacts which reset the K‐Ar ages produced the anisotropy and reduced the porosity of chondri

ISSN:0094-8276    

DOI:10.1029/GL010i001p00083

年代:1983

数据来源: WILEY

摘要:

An electron microscope study of the olivine to spinel transformation in Ni2SiO4has revealed the nature of the defect structures in the transforming olivine immediately ahead of the migrating olivine‐spinel interphase boundary. The residual olivine has a high density of [100] and [001]Burger's‐vector dislocations (1 to 5 × 109cm−2). No stacking faults or dissociated dislocations are observed in the residual olivine, although a significant number (∼108cm−2) of [010] dislocations are activated by the extreme synthesis conditions (52 kbar, 1100° C). This result may have important applications in the study of paleo‐deformation of olivine. The mechanism of the transformation in the fine‐ground sample appears to be a nucleation and growth process with no evidence to support a marten

ISSN:0094-8276    

DOI:10.1029/GL010i001p00087

年代:1983

数据来源: WILEY

摘要:

Six‐coordinated Si in stishovite yields a sharp29Si MASNMR signal at −191.3 ±0.2 ppm from TMS, well‐removed from the characteristic signal associated with tetrahedral coordination in quartz, cristobalite, and other, less crystalline siliceous

ISSN:0094-8276    

DOI:10.1029/GL010i001p00091

年代:1983

数据来源: WILEY

摘要:

Cazenave and Dominh compare the topography in a portion of the rolling plains province of Venus with a measure of the corresponding gravity perturbations, the residual acceleration of the Pioneer Venus Orbiter. They ignore substantial geometric factors and make unsubstantiated geophysical assumptions to draw conclusions which we consider logically invalid and numerically implausible.

ISSN:0094-8276    

DOI:10.1029/GL010i001p00093

年代:1983

数据来源: WILEY

摘要:

When the electrochemical concentration cell (ECC) ozonesonde exhibits a background current at the time of balloon launch, the measured cell current must be corrected to obtain the actual ozone response. We have found a pressure dependent factor in the background current that originates in a convective mass transport parameter. For atmospheric pressures greater than 100 mb, the mass transport parameter is constant, but at pressures less than 100 mb it declines logarithmically with pressure. We suggest that the background current correction is directly correlated to the mass transport parameter pressure dependence. Compared to a constant background current, the presently used background current correction based on the oxygen partial pressure leads to an overestimate of the integrated ozone value in the troposphere for the ECC ozonesonde data.

ISSN:0094-8276    

DOI:10.1029/GL010i001p00097

年代:1983

数据来源: WILEY

摘要:

To determine the scattering properties of microcracks created by water injection in hot dry rock a method for analyzing trajectory ellipsoids of seismic particle motions has been applied. Lengths and directions of three principal axes of trajectory ellipsoids were calculated, and a distribution of the shape of these ellipsoids suggests existence of a strong scattering region around the injection point. This strong scattering has an anisotropic property presumably due to microcrack orientation in the original rock.

ISSN:0094-8276    

DOI:10.1029/GL010i001p00101

年代:1983

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL010i001p00105

年代:1983

数据来源: WILEY