No collective neutrino flavor conversions during the supernova accretion phase

The large neutrino fluxes emitted with a distinct flavor hierarchy from core-collapse supernovae (SNe) during the post-bounce accretion phase, offer the best opportunity to detect effects from neutrino flavor oscillations. We perform a dedicated study of the SN neutrino flavor evolution during the accretion phase, using results from recent neutrino radiation hydrodynamics simulations. In contrast to what expected in the presence of only neutrino-neutrino interactions, we find that the multi-angle effects associated with the dense ordinary matter suppress collective oscillations. This is related to the high matter densities during the accretion phase in core-collapse SNe of massive iron-core progenitors. The matter suppression implies that neutrino oscillations will start outside the neutrino transport region and therefore will have a negligible impact on the neutrino heating and the explosion dynamics. Furthermore, the possible detection of the next galactic SN neutrino signal from the accretion phase, based on the usual Mikheyev- Smirnov-Wolfenstein effect in the SN mantle and Earth matter effects, can reveal the neutrino mass hierarchy in the case that the mixing angle $\theta_{13}$ is not very small.Comment: (4 pages, 4 eps figures, v2 revised version. Discussion clarified. Matches the version published on PRL

Stability analysis of collective neutrino oscillations in the supernova accretion phase with realistic energy and angle distributions

We revisit our previous results on the matter suppression of self-induced neutrino flavor conversions during a supernova (SN) accretion phase, performing a linearized stability analysis of the neutrino equations of motion, in the presence of realistic SN density profiles. In our previous numerical study, we used a simplified model based on an isotropic neutrino emission with a single typical energy. Here, we take into account realistic neutrino energy and angle distributions. We find that multi-energy effects have a sub-leading impact in the flavor stability of the SN neutrino fluxes with respect to our previous single-energy results. Conversely, realistic forward-peaked neutrino angular distributions would enhance the matter suppression of the self-induced oscillations with respect to an isotropic neutrino emission. As a result, in our models for iron-core SNe, collective flavor conversions have a negligible impact on the characterization of the observable neutrino signal during the accretion phase. Instead, for a low-mass O-Ne-Mg core SN model, with lower matter density profile and less forward-peaked angular distributions, collective conversions are possible also at early times.Comment: v2: 8 pages, 3 eps figures. Revised version. Minor changes. References updated. Matches the version published on PR

Spatial and depth‐dependent variations in magma volume addition and addition rates to continental arcs: Application to global CO_2 fluxes since 750 Ma

Magma transfer from the mantle to the crust in arcs is an important step in the global cycling of elements and volatiles from Earth's interior to the atmosphere. Arc intrusive rocks dominate the total magma mass budget over extrusive rocks. However, their total volume and rate of addition is still poorly constrained, especially in continental arcs. We present lateral (forearc to backarc) and depth‐dependent (volcanics to deep crust) magma volume additions and arc‐wide magma addition rates (MARs) calculated from three continental arc crustal sections preserving magma flare‐up periods. We observe an increase in volume addition with depth and less magma added in the forearc (~15%) and backarc (~10% to 30%) compared to the main arc. Crustal‐wide MARs for each section are remarkably similar and around 0.7–0.9 km^3/km^2/Ma. MARs can be used to estimate CO_2 fluxes from continental arcs. With initial magma CO_2 contents of 1.5 wt.%, global continental arc lengths, and MARs, we calculate changes in C (Mt/year) released from continental arcs since 750 Ma. Calculated present‐day global C fluxes are similar to values constrained by other methods. Throughout the Phanerozoic, assuming equal durations of flare‐up and lull magmatism, calculated continental CO_2 flux rates vary between 4 and 18 Mt C/year with highest values in the Mesozoic. These fluxes are considered minima since the intake of mantle and/or crustal carbon is not considered. Magmatic episodicity in continental arcs and changes in arc thickness and width are critical to consider when calculating MARs through time

Analysis of matter suppression in collective neutrino oscillations during the supernova accretion phase

The usual description of self-induced neutrino flavor conversions in core collapse supernovae (SNe) is based on the dominance of the neutrino density n_nu over the net electron density n_e. However, this condition is not met during the post-bounce accretion phase, when the dense matter in a SN is piled up above the neutrinosphere. As recently pointed-out, a dominant matter term in the anisotropic SN environment would dephase the flavor evolution for neutrinos traveling on different trajectories, challenging the occurrence of the collective behavior in the dense neutrino gas. Using the results from recent long term simulations of core-collapse SN explosions, based on three flavor Boltzmann neutrino transport in spherical symmetry, we find that both the situations of complete matter suppression (when n_e >> n_nu) and matter-induced decoherence (when n_e \gtrsim n_nu) of flavor conversions are realized during the accretion phase. The matter suppression at high densities prevents any possible impact of the neutrino oscillations on the neutrino heating and hence on the dynamics of the explosion. Furthermore, it changes the interpretation of the Earth matter effect on the SN neutrino signal during the accretion phase, allowing the possibility of the neutrino mass hierarchy discrimination at not too small values of the leptonic mixing angle \theta_{13} (i.e. \sin^2{\theta}_{13} \gtrsim 10^{-3}).Comment: Revised version (15 pages, 13 eps figures) published on Physical Review D. Discussion enlarged, references update

Extreme enrichment in atmospheric 15N15N.

Molecular nitrogen (N2) comprises three-quarters of Earth's atmosphere and significant portions of other planetary atmospheres. We report a 19 per mil (‰) excess of 15N15N in air relative to a random distribution of nitrogen isotopes, an enrichment that is 10 times larger than what isotopic equilibration in the atmosphere allows. Biological experiments show that the main sources and sinks of N2 yield much smaller proportions of 15N15N in N2. Electrical discharge experiments, however, establish 15N15N excesses of up to +23‰. We argue that 15N15N accumulates in the atmosphere because of gas-phase chemistry in the thermosphere (>100 km altitude) on time scales comparable to those of biological cycling. The atmospheric 15N15N excess therefore reflects a planetary-scale balance of biogeochemical and atmospheric nitrogen chemistry, one that may also exist on other planets

Probing the neutrino mass hierarchy with the rise time of a supernova burst

The rise time of a Galactic supernova (SN) bar-nue lightcurve, observable at a high-statistics experiment such as the IceCube Cherenkov detector, can provide a diagnostic tool for the neutrino mass hierarchy at "large" 1-3 leptonic mixing angle theta_13. Thanks to the combination of matter suppression of collective effects at early postbounce times on one hand and the presence of the ordinary Mikheyev-Smirnov-Wolfenstein effect in the outer layers of the SN on the other hand, a sufficiently fast rise time on O(100) ms scale is indicative of an inverted mass hierarchy. We investigate results from an extensive set of stellar core-collapse simulations, providing a first exploration of the astrophysical robustness of these features. We find that for all the models analyzed (sharing the same weak interaction microphysics) the rise times for the same hierarchy are similar not only qualitatively, but also quantitatively, with the signals for the two classes of hierarchies significantly separated. We show via Monte Carlo simulations that the two cases should be distinguishable at IceCube for SNe at a typical Galactic distance 99% of the times. Finally, a preliminary survey seems to show that the faster rise time for inverted hierarchy as compared to normal hierarchy is a qualitatively robust feature predicted by several simulation groups. Since the viability of this signature ultimately depends on the quantitative assessment of theoretical/numerical uncertainties, our results motivate an extensive campaign of comparison of different code predictions at early accretion times with implementation of microphysics of comparable sophistication, including effects such like nucleon recoils in weak interactions.Comment: 17 pages, 5 figures, unchanged but for minor reference update, matches published versio

Spatial and depth‐dependent variations in magma volume addition and addition rates to continental arcs: Application to global CO_2 fluxes since 750 Ma

Magma transfer from the mantle to the crust in arcs is an important step in the global cycling of elements and volatiles from Earth's interior to the atmosphere. Arc intrusive rocks dominate the total magma mass budget over extrusive rocks. However, their total volume and rate of addition is still poorly constrained, especially in continental arcs. We present lateral (forearc to backarc) and depth‐dependent (volcanics to deep crust) magma volume additions and arc‐wide magma addition rates (MARs) calculated from three continental arc crustal sections preserving magma flare‐up periods. We observe an increase in volume addition with depth and less magma added in the forearc (~15%) and backarc (~10% to 30%) compared to the main arc. Crustal‐wide MARs for each section are remarkably similar and around 0.7–0.9 km^3/km^2/Ma. MARs can be used to estimate CO_2 fluxes from continental arcs. With initial magma CO_2 contents of 1.5 wt.%, global continental arc lengths, and MARs, we calculate changes in C (Mt/year) released from continental arcs since 750 Ma. Calculated present‐day global C fluxes are similar to values constrained by other methods. Throughout the Phanerozoic, assuming equal durations of flare‐up and lull magmatism, calculated continental CO_2 flux rates vary between 4 and 18 Mt C/year with highest values in the Mesozoic. These fluxes are considered minima since the intake of mantle and/or crustal carbon is not considered. Magmatic episodicity in continental arcs and changes in arc thickness and width are critical to consider when calculating MARs through time

Magma Mixing at OlDoinyo Lengai: A Mineralogical and Trace Element Analysis of the 2007-8 Eruption.

Chapter I: The 2007-8 eruption at Lengai was highly explosive, reaching plinian proportions, and the anhydrous nature of the nephelinite magma at Lengai, does not explain this highly volatile behavior. The increase in volatiles in a low H2O nephelinite magma could occur from decompression melting of magma injection from a deeper source. Two distinct nephelinite compositions were identified in a mineralogical analyses of the ash erupta: a highly evolved nephelinite (OL2), with less than 3% glass from the magma chamber, as indicated by the highly peralkalinic feldspathoid: combeite (Na2Ca2Si3O9), commonly found in Lengai eruptive products (Dawson 1966, 1998), and a less evolved nephelinite magma, with up to 17% glass (ASHES) that did not contain combeite, with significantly higher Si, Al, Mg, and Mn content. Phase abundances, mineral formulas and endmember components are calculated for both assemblages. Phenocrysts encountered in both nephelinite assemblages are nepheline, augite (CPX), titanium andradite, wollastonite, apatite, and iron oxides. Magma mixing of the two nephelinites are evidenced by sudden changes in the melt chemistry in both ash sample sets. In the combeite-wollastonite-nephelinite (OL2), combeite microlites exhibit resorbtion rims indicative of mineral instability, and nepheline from this assemblage has a distinct chemical boundary withinrim, evidenced by Mg overgrowth. The wollastonite-nephelinite contains almost fully resorbed CPX, and resorbtion rims on Ti-andradite. Chemical changes resulting from a decrease of in Ca in the melt were detected in the rims of the wollastonite via electron microprobe WDS mapping. Two large CPX mineral grains with very differing composition and crystallization histories were found alongside each other in the wollastonite-nephelinite. Primary compositional differences between the two CPX grains are Ti and Mg content, the CPX mineral grain exhibiting disequilibrium features (ASH15-DISEQ) had higher total Mg (Mg content as high as 0.87 c.p.f.u., with an average of 0.72 c.p.f.u. as opposed to an average of 0.52 c.p.f.u.) and lower Ti (on average 0.00 c.p.f.u., as opposed to 0.02 c.p.f.u. in the second grain), than the zoned CPX (ASH15-EQUIL). The Ti-enriched CPX (ASH15-EQUIL) exhibits oscillatory compositional zoning, with few inclusions. The second (ASH15-DISEQ) is richer in Mg, and contains abundant inclusions, suggesting a high degree of disequilibrium. Both CPX and nepheline microlites and rims are enriched in Al, Mg and Mn, elements typically depleted in the highly peralkaline magma chamber. For both ash types the crystal size distribution is bimodal indicative of two stage cooling: an initial stage of slow cooling, with low nucleation and high growth rates producing large crystals (longest axes up to 1.5mm), followed by a stage of rapid cooling with high nucleation and low growth rates as the magma migrated to the surface. The large volume of visible interstitial glass vesicles in OL2 scoria is indicative of rapid degassing and subsequent crystallization in the magma chamber. Chapter II: Oldoinyo Lengai is the world’s only active natrocarbonatite-nephelinite mixed-magma system on earth. Recent volcanic activity and geochemical studies suggest there may be two nephelinite magmas mixing prior to the 2007-8 eruption. In this study, we present scanning electron microscope (SEM) analyses from 2006 natrocarbonatite deposits, electron microprobe (EMPA) melt analyses for the 2007-8 eruptive nephelinite deposits: combeite-wollastonite nephelinite (CWN) and wollastonite nephelinite (WN). We also present laser ablation inductively-coupled plasma mass spectrometry (LA-ICPMS) trace and rare earth element data (ppm) for a xenolith sample (consisting of CPX and apatite), melt phenocrysts (andradite, and CPX), and matrix (a non-vitrified, non-crystalline, ultrafine ash representative of the pre-eruptive melt composition). Rare earth and trace element data presented for: V, Cr, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Th, and U. In addition, mineral/matrix partition coefficients (Kds) are presented for andradite and CPX. From the total alkali vs. silicate (TAS) diagram and Harker’s diagrams two distinct melt compositions were identified. These two melt compositions are characterized by different REE and trace element abundance patterns for the melt and phenocrysts, both of which demonstrate differences of up to 3 orders of magnitude in concentration (ppm), especially in the LREE. Similarity in trace- and rare-earth-element-normalized abundance patterns for both matrix and andradite phenocryst analyses suggest they share a common source and may originate from the same parental magma. However the broad range in values suggests that the WN may be more recently evolved from the parental magma than the CWN, which demonstrates evidence of contact with natrocarbonatite in the form of resulting enrichments of HREE, Th and U. However, interaction with the natrocarbonatite was not indicated by the CPX patterns, which show significant differences in concentration (ppm; normalized to CI chondrite), in addition to a pronounced negative K anomaly and a positive Y anomaly displayed by some samples. Overlap in melt compositions is interpreted as the chemical signature of magma mixing, especially in combination with evidence of other disequilibrium features, as documented by Thomas et al (2018), such as CPX and garnet resorbtion, zoning, and the two differentmineral assemblages (CWN and WN). The data from this study support the presence of a deeper nephelinite source (WN) injecting Lengai’s primary nephelinite chamber (CWN) causing the 2007-8 eruption. A time series of seismic and eruptive events at Lengai supports the hypothesis that all explosive eruptions are triggered by injection of deeper magma (WN) which is preempted by a series of significant seismic events (ISC., 2001, Baer et al., 2008, and GVP., 2014), as supported in the most recent eruption by InSAR studies (Biggs et al 2009., 2013)

Prospective measurement of the width of cerebrospinal fluid spaces by cranial ultrasound in neurologically healthy children aged 0-19 months

BACKGROUND Ultrasound (US) is often the first method used to look for brain or cerebrospinal fluid (CSF) space pathologies. Knowledge of normal CSF width values is essential. Most of the available US normative values were established over 20 years ago, were obtained with older equipment, and cover only part of the age spectrum that can be examined by cranial US. This prospective study aimed to determine the normative values of the widths of the subarachnoid and internal CSF spaces (craniocortical, minimal and maximal interhemispheric, interventricular, and frontal horn) for high-resolution linear US probes in neurologically healthy infants and children aged 0-19 months and assess whether subdural fluid collections can be delineated. METHODS Two radiologists measured the width of the CSF spaces with a conventional linear probe and an ultralight hockey-stick probe in neurologically healthy children not referred for cranial or spinal US. RESULTS This study included 359 neurologically healthy children (n$_{boys}$ = 178, 49.6%; n$_{girls}$ = 181, 50.4%) with a median age of 46.0 days and a range of 1-599 days. We constructed prediction plots, including the 5th, 50th, and 95th percentiles, and an interactive spreadsheet to calculate normative values for individual patients. The measurements of the two probes and the left and right sides did not differ, eliminating the need for separate normative values. No subdural fluid collection was detected. CONCLUSION Normative values for the widths of the subarachnoid space and the internal CSF spaces are useful for evaluating intracranial pathology, especially when determining whether an increase in the subarachnoid space width is abnormal

Diffuse degassing at Longonot volcano, Kenya: implications for CO2 flux in continental rifts

Magma movement, fault structures and hydrothermal systems influence volatile emissions at rift volcanoes. Longonot is a Quaternary caldera volcano located in the southern Kenyan Rift, where regional extension controls recent shallow magma ascent. Here we report the results of a soil carbon dioxide (CO2) survey in the vicinity of Longonot volcano, as well as fumarolic gas compositions and carbon isotope data. The total non-biogenic CO2 degassing is estimated at < 300 kg d− 1, and is largely controlled by crater faults and fractures close to the summit. Thus, recent volcanic structures, rather than regional tectonics, control fluid pathways and degassing. Fumarolic gases are characterised by a narrow range in carbon isotope ratios (δ13C), from − 4.7‰ to − 6.4‰ (vs. PDB) suggesting a magmatic origin with minor contributions from biogenic CO2. Comparison with other degassing measurements in the East African Rift shows that records of historical eruptions or unrest do not correspond directly to the magnitude of CO2 flux from volcanic centres, which may instead reflect the current size and characteristics of the subsurface magma reservoir. Interestingly, the integrated CO2 flux from faulted rift basins is reported to be an order of magnitude higher than that from any of the volcanic centres for which CO2 surveys have so far been reporte