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991.
Observations of radio emission at 3.3 mm wavelength associated with magnetic fields in active regions are reported. Results of more than 200 regions during the years 1967–1968 show a strong correlation between peak enhanced millimeter emission, total flux of the longitudinal component of photospheric magnetic fields and the number of flares produced during transit of active regions. For magnetic flux greater than 1021 maxwells flares will occur and for flux of 1023 maxwells the sum of the H flare importance numbers is about 40. The peak millimeter enhancement increases with magnetic flux for regions which subsequently flared. Estimates of the magnetic energy available and the correlation with flare production indicate that the photospheric fields and probably chromospheric currents are responsible for the observed pre-flare heating and provide the energy of flares.This work was supported in part by NASA Contract No. NAS2-7868 and in part by Company funds of The Aerospace Corporation. 相似文献
992.
Solar flares and magnetospheric substorms are discussed in the context of a general theory of impulsive flux transfer events (IFTE). IFTE theory, derived from laboratory observations in the Double Inverse Pinch Device (DIPD), provides a quantitative extension of neutral sheet theories to include nonsteady field line reconnection. Current flow along the reconnection line increases with magnetic flux storage. When flux build-up exceeds the level corresponding to a critical limit on the current, instabilities induce a sudden transition in the mode of conduction. The resulting IFTE, indifferent to the specific modes and instabilities involved, is the more energetic, the lower the initial resistivity. It is the more violent, the greater the resulting resistivity increase and the faster its growth. Violent events can develop very large voltage transients along the reconnection line. Persistent build-up promoting conditions produce relaxation oscillations in the quantity of flux and energy stored (build-up-IFTE cycles). It is difficult to avoid the conclusion: flares and substorms are examples of IFTE. 相似文献
993.
Preliminary results of polarization measurements at three solar flares of July 5 and 6, 1974, are given. The measurements were performed at h 15 keV with Thomson-scattering polarimeter on the Intercosmos 11 satellite.At the decay phase of the flare on July 5 we obtained P = 3.4–5.0%, which did not exclude some contribution from non-thermal processes. At the flares of July 6 we found P =1.0–1.9% and P = 0.1–2.0%, respectively: neither value exceeds the level of statistical fluctuations.Presented at XVIII COSPAR Meeting (VARNA, May–June 1975), contribution III.B.2.9. 相似文献
994.
Slitless spectrograms obtained during the eclipse of 10 June 1972 have been analyzed to determine the height distribution of the D3 He line intensity.For undisturbed regions the maximum of D3 line intensity is confirmed to exist at about 1700km above the limb. Besides the above mentioned maximum, in plages a considerable intensity may be observed at low heights (h < 1000 km).An analysis of these observations for h > 1000 km has been carried out within the low temperature mechanism of triplet helium emission taking into account the helium ionization by XUV radiation. The density dependence of the 23
S level population at different XUV flux values has been calculated. Our observations give N
e 2 × 1010 cm–3 in the chromosphere at h = 2000 km. The probable coincidence of the H and He emission small filaments in the middle chromosphere is discussed. 相似文献
995.
Daniel Benest 《Celestial Mechanics and Dynamical Astronomy》1976,13(2):203-215
Numerical explorations of the restricted problem have shown that for stable large nonperiodic retrograde satellite orbits, the motion can be decomposed into a fast reference motion and a slow libration aroundB
2 We study here this libration in the circular plane Hill's case, for which the reference motion is elliptic. We establish the equations of motion for the coordinates of the centre of this ellipse. We find two integrals of motion: the first is the semi-major axis of the ellipse; the second is essentially Jacobi's integral, translated into the new coordinates. We give a formula for the period of the libration and we find its limiting value for small libration amplitudes. A numerical verification gives very good agreement for all these results. 相似文献
996.
The peralkaline Kaffo albite—riebeckite granite is an albitised, low-temperature intrusion in Liruei Complex, one of the oldest of the ring-complexes in the Younger Granite province of Nigeria. Analyses of borehole samples from different parts of the intrusion show it to be compositionally heterogeneous, especially in respect of Si, Al, Na, K and F distribution and this, in part, can be correlated with the variable degree of albitisation. Isotopically the granite is a normal plutonic type with δ18 O values of , and albitisation does not seem to have been accompanied by exchange of isotopes between albitising fluid and the granite. Co-existing riebeckitic-arfvedsonite and aegirine pairs from borehole samples show extreme enrichment in Na and Fe; the amphibole also shows considerable substitution of Fe by Ti, Zn and Mn, and of OH by F. Isotopically the amphibole and pyroxene are different from others, having low, variable δ18 O values (+5.3–+6.4 and , respectively), and the fractionation value Δ Px — Am is always large, negative and constant (—). The low δ18 O values are considered to be due to special features of the crystal chemistry of the alkali amphiboles and pyroxenes, and the spread of each set of values may be due to sub-solidus isotope exchange between the minerals and albitising fluid. 相似文献
997.
The characteristic rocks of the Upper Palaeozoic greenstonesof S.W. England are intrusive dolerites and extrusive basicpillow lavas with minor intermediate volcanics and ultrabasics(picrites). Pyroclastics are represented by keratophyric andbasic tuffs. The intrusive greenstones show varying degrees of alteration(spilitization) from a primary ilmenite-plagioclase-clinopyroxene?olivineassemblage to a hydrous low-grade spilite (or meta-dolerite)assemblage composed of variable proportions of albite, chlorite,epidote, calcite, and amphibole. Based on the distribution of elements little affected by secondaryprocesses (Ti, P, Y, Nb, and Zn), the intrusive greenstonescontain representatives of both the alkali olivine basalt andtholeiitic basalt magma series. Magmatic differentiation isgenerally minimal with the Devonian alkali basalt greenstonesbeing principally basaltic, while some of the Carboniferousalkali basalt greenstones tend towards mugearitic compositions.No intrusive acid differentiates have yet been reported. Apart from differences of magma type and minor differentiation,low-grade alteration or spilitization has alsogoverned the geochemical variation seen in the greenstones.Spilitization caused (a) local redistribution of principallyCa (forming epidote-rich and calcite-rich patches) and Mg (formingchlorite-rich patches), together with their respective coherenttrace elements, and (b) the variable, but often limited, lossof Ca, Sr, K, Rb, and Ba from many bodies, together with a gainin Na and H2O. Progressive hydration, however, caused a decreasein the oxidation ratioa feature found to be common inmany spilitic suites and mainly governed by the relative distributionof chlorite versus epidote. 相似文献
998.
Grains ejected from stars at velocities of 107 cm s–1 and/or grains accelerated by the pressure of starlight in the intercloud medium to velocities in the range 2×106–107 cm s–1 are slowed to velocities of about 2×105 cm s–1 in a typical interstellar cloud. The interaction of fast grains with gas atoms as they are slowed in clouds could provide (a) the dominant heat source for interstellar clouds; (b) sites for molecule formation; and (c) a mechanism of providing a pressure balance between clouds and the intercloud medium.Paper presented at the Symposium on Solid State Astrophysics, held at the University College, Cardiff, Wales, between 9–12 July, 1974. 相似文献
999.
1000.