Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

Domain state of Ti-rich titanomagnetites deduced from domain structure observations and susceptibility measurements

Domain structure observations and measurements of the temperature dependence of susceptibility on synthetic and natural titanomagnetites are reported. At room temperature Ti-rich titanomagnetite particles (x ≈ 0.6) of MD grain size normally develop a very complicated domain structure. The experimental results of our investigations, in addition to simple theoretical calculations, indicate that internal stress is the dominant cause of the observed anomalous domain patterns. Part of the results have already been published by Appel and Soffel (1984). The paper presented here, however, is a far more extended summary of the actual state of our research.           ARK: https://n2t.net/ark:/88439/y026104 Permalink: https://geophysicsjournal.com/article/212 &nbsp

Palaeomagnetism of Upper Cretaceous volcanics and Nubian sandstones of Wadi Natash, SE Egypt and implications for the polar wander path for Africa in the Mesozoic

Eighteen sites (342 samples) from Upper Cretaceous Wadi Natash volcanics (24.5° N, 34.5° E) yield a mean direction of magnetization D = 345.4°, I = 16.7° with α95 = 8.5°, k = 21.4, N = 15 after AF cleaning resulting in a pole at 69.3° N, 258° E with A95 = 5.8° All sites have normal polarity consistent with their age and the magnetic stratigraphy in the Cretaceous. From 5 sites (85 samples) from Upper Cretaceous Nubian sandstone at Wadi Natasha mean direction D = 358.1°, I = 32.0° with α95 = 8.7°, k = 143 (mixed polarity) was obtained after thermal demagnetization. Combined with previous investigations on Nubian sandstone at other locations in Southern Egypt (Schult et al. 1978) this yields a pole at 81.8° N, 223° E with A95 = 3.3°, N = 23. 9 sites from Eocene Baharia iron ores (27.5° N, 29.0° E) yield a mean direction D = 188.0°, I = –43.6° and α95 = 6.4°, k = 65 with a pole at 83.5° N, 139° E and A95 = 7° In addition the palaeomagnetism of some Tertiary basaltic rocks in Northern Egypt was studied. The polar wander path for Africa in Mesozoic time is presented showing more mobility than in earlier papers. For appropriate reconstructions of South America with respect to Africa the polar wander paths of both continents are substantially in agreement.           ARK: https://n2t.net/ark:/88439/y010555 Permalink: https://geophysicsjournal.com/article/252 &nbsp

Archaeomagnetic study of medieval fireplaces at Mannheim-Wallstadt and ovens from Herrenchiemsee (Southern Germany) and the problem of magnetic refraction

Ten fireplaces from Mannheim-Wallstadt (MW) and four ovens from Herrenchiemsee (HC) were studied with regard to their archaeomagnetic properties. The ages of the medieval structures were only poorly known and an age dating was intended with the help of the standard curves for the declination and inclination of the geomagnetic field of the past 2000 years, as set up by Thellier (1981) for France. The stability of the NRM was tested with Thellier's test. Of the ten MW fireplaces, only one passed the test, whereas of the four ovens of HC, all passed the test but one of them had to be excluded because of secondary displacements within the structure. The MW fireplace could be dated to 670-700 A.D., in agreement with other archaeological age determinations for the fireplaces. The ovens from HC yielded an age between 1100 and 1170 A.D. The ovens showed the effect of magnetic refraction. Model calculations carried out on circular ring structures require a susceptibility of the oven material of the order of 0.5 SI units to explain the observed effect. The presently observed mean susceptibility at room temperature is only around 5 x 10-3 SI units. However, heating of the material at 550° C for 2 h in a reducing environment was able to increase the susceptibility by a factor of 20. This effect is explained by the reduction of secondary iron oxides and hydroxides to magnetite. Another increase by a factor of about 1.5 is obtained from the Hopkinson effect (increase of susceptibility with temperature) at the blocking temperature of magnetite. Combining all effects, it is possible to attain values for the susceptibility at the blocking temperature of magnetite as high as 0.2 SI units, which is the order of magnitude required for the explanation of the observed effect of magnetic refraction. This effect demands that special considerations be made during archaeomagnetic sampling from archaeological ovens or kilns.           ARK: https://n2t.net/ark:/88439/y016135 Permalink: https://geophysicsjournal.com/article/117 &nbsp