Behavior and effects of phosphorus in the system Na2O−K2O−Al2O3−SiO2−P2O5−H2O at 200 MPa(H2O)

The addition of phosphorus to H₂O-saturated and initially subaluminous haplogranitic (Qz–Ab–Or) compositions at 200 MPa(H₂O) promotes expansion of the liquidus field of quartz, a marked decrease of the solidus temperature, increased solubility limits of H₂O in melt at low phosphorus concentrations, and fractionation of melt out of the haplogranite plane (projected along an Or₂₈ isopleth) toward a peralkaline, silica-poor but quartz-saturated minimum composition. The partition coefficient for P₂O₅ between aqueous vapor and melt with an ASI (aluminum saturation index, mol Al/[mol Na+K])=1 is negligible (0.06), and consequently so are the effects of phosphorus on other melt-vapor relations involving major components. Phosphorus becomes more soluble in vapor, however, as the concentration of a NaPO₃ component increases via the fractionation of melt by crystallization of quartz and feldspar. The experimental results here corroborate existing concepts regarding the interaction of phosphorus with alkali aluminosilicate melt: phosphorus has an affinity for alkalis and Al, but not Si. Phosphorus is incorporated into alkali feldspars by the exchange component AlPSi_-2. For subaluminous compositions (ASI=1), the distribution coefficient of phosphorus between alkali feldspar and melt, D[P]Af/m, is 0.3. This value increases to D[P]Af/m=1.0 at a melt ASI value of 1.3. The increase in D[P]Af/m with ASI is expected from the fact that excess Al promotes the AlPSi_-2 exchange. With this experimental data, the P₂O₅ content of feldspars and whole rocks can reveal important facets of crystallization and phosphorus geochemistry in subaluminous to peraluminous granitic systems.     

Solar Radio Bursts Associated with Standing Shock Waves

Geomagnetism and Aeronomy - A number of phenomena with radio bursts in the decimeter and centimeter wavelength ranges similar to type-II bursts in the meter range have been considered. In all...     

Multi-scale temporal features of the 14 July 2000 meter- wavelength dynamic radio spectrum compared with TRACE data

The 14 July 2000 (`Bastille Day') eruptive and geoeffective flare event was observed by the digital IZMIRAN radio spectrograph in the frequency range of 25–270 MHz. This instrument allowed the analysis of various features of the dynamic radio spectrum and their comparison with other observational data, in particular with development of a spectacular EUV post-eruption arcade recorded aboard the Transition Region and Coronal Explorer (TRACE). (1) A compressed multi-hour radio spectrum shows that the event caused a conspicuous weakening of the pre-existing noise storm. This phenomenon was perhaps caused by interaction of a large halo coronal mass ejection (CME), recorded by the the Large Angle and Spectroscopic Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO), with emitting coronal structures. (2) Several type II bands are present at the initial and maximum phases of the flare event. The frequency drifts of the clearest bands correspond to the estimated shock wave speed of 1100–2300 km s⁻¹ that is comparable with the CME speed observed in the sky plane. (3) Significant broadband enhancements of the metric radio emission took place around of 10:24–10:27 UT coinciding with sharp development of the EUV arcade in the northeast direction. It appears to correspond to the intensification of the electron acceleration in a process of post-eruption loop formation. (4) The high-resolution radio spectrum revealed a superposition of numerous type III-like bursts and/or pulsations with a time scale ranging from a few seconds to several tens of seconds. These features can be attributed particularly to successive formation of new loops of the arcade and corresponding temporal fragmentation of the electron acceleration in the course of the post-eruption reconnection. In summary, the analysis demonstrates the correspondence between the multi-scale temporal features of the metric radio emission and such phenomena as the CME and post-eruption EUV arcade. Some spectra, images, and movies illustrating the event are presented also on the accompanying CD-ROM. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014224004946     

Propagation of interplanetary shock waves by observations of type II solar radio bursts on IMP-6

A new interpretation of the low frequency type II solar radio bursts of 30 June 1971, and 7–8 August 1972 observed with IMP-6 satellite (Malitson et al., 1973a,b) is suggested. The analysis is carried out for two models of the electron density distribution in the interplanetary medium taking into account that N ~ 3.5 cm^?3 at a distance of 1 a.u. It is assumed that the frequency of the radio emission corresponds to the average electron density behind the shock front which exceeds the undisturbed electron density by the factor of 3. The radio data indicate essential deceleration of the shock waves during propagation from the Sun up to 1 a.u. The characteristics of the shock waves obtained from the type II bursts agree with the results of the in situ observations.     

Crystallization of the Little Three layered pegmatite-aplite dike, Ramona District, California

Subhorizontally layered pegmatite-aplite bodies are characterized by fine-grained, sodic to granitic aplite that is usually juxtaposed abruptly above by much coarser-grained, commonly graphic potassic pegmatite. Although well studied, there currently is little concensus as to how such dikes form. The Little Three dike near Ramona, California, is representative of such zoned bodies in this and other regions, and contains discontinuous miarolitic pockets near the base of the graphic pegmatite zone. Tourmaline, garnet, biotite, and muscovite show no changes in major- or minor-element compositions indicative of progressive magmatic fractionation until the immediate vicinity of the main miarolitic zone, where they record abrupt and extreme enrichments in Li, F, and Mn. There is no correlation of chemical changes in the dike with the appearance of small miarolitic vugs well below the main miarolitic zone, nor is there any indication that the aplite, graphic pegmatite, or miarolitic pockets represent separate magma injections. The chemistries of tourmaline, garnet, and micas, however, preclude conventional models of Rayleigh fractionation or traditional zone refining. Textural features and modeled cooling histories indicate that the dike cooled quickly and might have solidified partially or totally to glass before crystallization commenced. Geothermometry based on the compositions of coexisting plagioclase and homogeneous, nonperthitic K-feldspar indicates inward crystallization of the dike, from ∼400–435 °C at the margins to ∼350–390 °C within 20–30 cm of the pocket horizon, then a sharp decrease to 240–275 °C in the pockets where K-feldspar is perthitic. We interpret the feldspar geothermometry (except perhaps in the miarolitic cavities) to reflect the temperatures at crystallization fronts that advanced into the pegmatite, first from the foot wall and eventually joined by a similar front downward from the hanging wall. Crystallization down from the hanging wall may have commenced after ∼70–80% of the foot wall aplite had crystallized. The very abrupt increases of Li, Mn, and F in tourmaline and garnet near the miarolitic zone appear to be explained best by the process of constitutional zone refining, in which a fluxed crystallization front sweeps an incompatible element-enriched boundary layer through a solid or semi-solid. After these two highly fluxed boundary layers merged near the main miarolitic zone, compositional evolution could have proceeded by crystal-melt fractionation. Received: 24 March 1998 / Accepted: 10 March 1999     

On a possible mechanism of zebra-pattern generation in solar radio emission

A mechanism is proposed for the generation of zebra-patterns in solar radio bursts due to the excitation of nonlinear ion-sound waves in a nonisothermal plasma and their scattering on fast particles. The appearance of the ion sound at the fundamental frequency can take place in the interaction of two opposing Alfvén or whistler waves. The presence of quasi-equidistant stripes in electro-magnetic radiation is ultimately determined by weak ion-sound dispersion resulting in the formation of higher harmonics.     

14 July 2000, a near-global coronal event and its association with energetic electron events detected in the interplanetary medium

On 14 July 2000, the LASCO coronagraphs showed a very fast halo coronal mass ejection in association with the radio bursts seen shortly after 10:00 UT. Radio imaging observations by the Nançay radioheliograph (NRH) of these bursts showed a very complex event that can be regarded as global: the sources encompassed all the visible range in longitude and a huge span in latitude. Another interesting feature of the radio event is its recurrent nature: after the most intense phase shortly after 10:00 UT, two other strong outbursts are detected, one at about 12:50 UT and another at about 13:48 UT. All of these sub-events showed similar development and likely evidence for CMEs. The launch of a CME in association with the 14:00 UT sub-event is inferred from WIND/WAVES, with interplanetary type II signatures in the hectometric wavelength range at that time. These later events were not detected by LASCO due to energetic particles hitting the CCD. During the Bastille Day event, energetic particle observations measured in situ by ACE/EPAM are dominated by energetic electrons. Changes in anisotropy and energy spectrum of the ～38–350 keV electrons suggest a good correlation with the coronal radio observations. In addition to the three main radio events and particle observations, the NRH data reveal moving features in the southern hemisphere. These moving features, located at about 45 deg south and with an angular extent of about 45 deg, are illuminated by non-thermal electrons and are seen at distances up to 2.5 solar radii from the Sun center. More generally, we interpret the global and recurrent coronal activity, revealed by the radio data, as responsible for populating the interplanetary medium with energetic electrons.     

Enhancement of the sterile neutrino yield at high density and increasing neutronization of matter

The relative yields of active and sterile neutrinos in matter with a high density and different degrees of neutronization have been calculated. A significant increase in the proportion of sterile neutrinos produced in superdense matter when the degree of neutronization approaches two has been found. The results obtained can be used to calculate the neutrino fluxes for matter with a high density and different degrees of neutronization in astrophysical processes, for example, the formation of a protoneutron supernova core.     

Melt-vapor solubilities and elemental partitioning in peraluminous granite-pegmatite systems: experimental results with Macusani glass at 200 MPa

Vapor-saturated experiments at 200 MPa with peraluminous, lithophile-element-rich rhyolite obsidian from Macusani, Peru, reveal high miscibility of H₂O and silicate melt components. The H₂O content of melt at saturation (11.5+-0.5 wt.%) is almost twice that predicted by existing melt speciation models. The corresponding solubility of melt components in vapor decreases from 15 wt.% dissolved solids (750°–775° C) to 9 wt.% at 600° C. With regard to major and most minor components, macusanite melt dissolves congruently in vapor. Among the elements studied (B, P, F, Li, Rb, Cs, Be, Sr, Ba, Nb, Zr, Hf, Y, Pb, Th, U, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm), only boron has a vapor/melt partition coefficient (D[B]) consistently 1 at superliquidus temperatures (>645° C). Phosphorus and fluorine behave similarly, with D[P] and D[F]<0.5. Little or no significant vapor/melt fractionation is evident among most periodic groups (alkalis, alkaline earths, Zr/Hf, or the REE). The temperature dependence of vapor/melt partition coefficients is generally greatest for cations with charge +3 (except Nb and U); most vapor/melt partition coefficients for trace elements increase with decreasing temperature to the liquidus. Crystallization proceeds by condensation of crystalline phases from vapor; most coexisting melts are aphyric. Changes in the major element content of melt are dominated by the mineral assemblage crystallized from vapor, which includes subequal proportions of white mica, quartz, albite, and orthoclase. The volumetric proportion of (mica + or-thoclase)/albite increases slightly with decreasing T, creating a sodic, alkaline vapor. Vapor deposition of topaz (T500° C), which consumes F from melt, returns K/Na ratios of melt to near unity with the vapor-deposition of albite. The abundances of most trace elements in residual melt change little with the crystallization of major phases, but in some cases are strongly controlled by the deposition of accessory phases including apatite (T550° C), which depletes the melt in P and REE. Below the liquidus, boron increasingly favors the vapor over melt with decreasing temperatures.     

Neutrino fluxes from a core-collapse supernova in a model with three sterile neutrinos

The characteristics of the gravitational collapse of a supernova and the fluxes of active and sterile neutrinos produced during the formation of its protoneutron core have been calculated numerically. The relative yields of active and sterile neutrinos in corematter with different degrees of neutronization have been calculated for various input parameters and various initial conditions. A significant increase in the fraction of sterile neutrinos produced in superdense core matter at the resonant degree of neutronization has been confirmed. The contributions of sterile neutrinos to the collapse dynamics and the total flux of neutrinos produced during collapse have been shown to be relatively small. The total luminosity of sterile neutrinos is considerably lower than the luminosity of electron neutrinos, but their spectrum is considerably harder at high energies.