Heavily‐hydrated lithic clasts in CH chondrites and the related,metal‐rich chondrites Queen Alexandra Range 94411 and Hammadah al Hamra 237

Abstract— Fine‐grained, heavily‐hydrated lithic clasts in the metal‐rich (CB) chondrites Queen Alexandra Range (QUE) 94411 and Hammadah al Hamra 237 and CH chondrites, such as Patuxent Range (PAT) 91546 and Allan Hills (ALH) 85085, are mineralogically similar suggesting genetic relationship between these meteorites. These clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite, prismatic sulfides (pentlandite and pyrrhotite), and Fe‐Mn‐Mg‐bearing Ca‐carbonates set in a phyllosilicate‐rich matrix. Two types of phyllosilicates were identified: serpentine, with basal spacing of ?0.73 nm, and saponite, with basal spacings of about 1.1–1.2 nm. Chondrules and FeNi‐metal grains in CB and CH chondrites are believed to have formed at high temperature (>1300 K) by condensation in a solar nebula region that experienced complete vaporization. The absence of aqueous alteration of chondrules and metal grains in CB and CH chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the CH and CB parent bodies. The hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and FeNi‐metal grains after these high‐temperature components had been transported from their hot formation region to a much colder region of the solar nebula.     

Bemerkungen zu chemischen Gesteinsanalysen

Ohne ZusammenfassungMit 2 Textabbildungen.     

On the Sudden Depression of Radio Emission From Plasma Above a Fast-Moving Sunspot

We present a very rare case of unexpected depression of radio emission above a sunspot using solar observations from RATAN-600. The sunspot had a very high proper motion on the solar surface. The depression lasted for 5 days without significant changes in area or magnitude of magnetic field of the associated sunspot. The observations show that the depression cannot be explained by the absorption of the emission during its propagation through the overlying magnetosphere of the AR or through the cold and opaque matter of a prominence. The theoretical interpretation of the phenomenon is based on the hypothesis that the motion of the sunspot on the photosphere leads to the significant expanding of the magnetic loop originated at this sunspot. The extension of the twisted magnetic rope results in the loss of equilibrium of the system: the closed magnetic structure (the twisted magnetic loop) seems destined to transform into an open one. The only mechanism of plasma heating which would be `switched off' in such a non-equilibrium configuration is that based on the quasi-static topological relaxation of a force-free magnetic field towards a configuration of minimum energy. Relaxation of magnetic fields does not occur in a non-equilibrium state. As a consequence, the energy release in the twisted magnetic rope and the temperature of the plasma of the local radio source have to fall down abruptly. Thus, the discussed phenomenon argues in favor of the relaxation model of plasma heating.     

Discovery of ions with nuclear charge Z ≧ 9 stably trapped in the earth's radiation belts

We report observations of MeV heavy ions made with Explorer 45 in the earth's radiation belts during the 7-month period June–December 1972 when four major magnetic storms occurred. Significant fluxes of ions heavier than fluorine (i.e. with nuclear charge Z ? 9) were observed stably trapped in the interior of the radiation belts at L ～ 2–4. These energetic very heavy ions, were found to appear suddenly during the August 1972 magnetic storm period and their fluxes decayed during the following months on time scales typically several tens of days. Simultaneously, strong increases in the geomagnetically trapped MeV helium and CNO ion fluxes were observed, and the post-injection flux decay of these ions was found to be slower than that of the Z ? 9 ions. The relative enhancements in trapped fluxes during the storm increased with increasing ion mass and/or increasing ion energy.     

Observations of the Ca xix resonance line during the impulsive phase of solar flares

Numerical simulations of flaring coronal loops, based on the assumption of an electron beam energy input, show that material is ablated from the chromosphere at approximately the local sound speed, thus giving rise to an overall blueshift in the spectrum of the soft X-ray Ca xix resonance line of up to 5 mÅ. In this paper we critically examine the observational evidence for the existence of this blueshift. From an exhaustive analysis of seven limb flares and nine disk flares, we find no indication of Ca xix blueshifts in excess of about 1 mÅ. This conclusion may present serious problems for the electron beam hypothesis: possible reasons for the apparent discrepancy between theory and observations are discussed.