11-year solar cycle influence on OH (3-1) nightglow observed by OSIRIS

In the mesosphere, the vibrationally excited hydroxyl layer is sensitive to changes in incoming solar flux. An enhanced photodissociation of molecular oxygen will lead to more atomic oxygen production, thus we expect the OH layer emission rate to be positively with the Lyman-α flux and the emission height to be negatively correlated. The Optical Spectrograph and InfraRed Imager System (OSIRIS) has recorded the Meinel band centred at 1.53 μm from 2001 to 2015. In this study, we show how the 11-year solar cycle signature manifests itself in this data set, in terms of OH zenith emission rate and emission height. As expected, the emission height is negatively correlated with the Lyman-α flux at all latitudes. The zenith emission rate is positively correlated with the Lyman-α flux at most latitudes except near the equator. By the means of a time dependent photochemical model, we show that the changing local time sampling of the Odin satellite was the cause of the observed distortion of the solar cycle signature near the equator

Trend and variability in ozone in the tropical lower stratosphere over 2.5 solar cycles observed by SAGE II and OSIRIS

We have extended the satellite-based ozone anomaly time series to the present (December 2012) by merging SAGE II (Stratospheric Aerosol and Gas Experiment II) with OSIRIS (Optical Spectrograph and Infrared Imager System) and correcting for the small bias (~0.5%) between them, determined using their temporal overlap of 4 years. Analysis of the merged data set (1984–2012) shows a statistically significant negative trend at all altitudes in the 18–25 km range, including a trend of (−4.6 ± 2.6)% decade⁻¹ at 19.5 km where the relative standard error is a minimum. We are also able to replicate previously reported decadal trends in the tropical lower-stratospheric ozone anomaly based on SAGE II observations. Uncertainties are smaller on the merged trend than the SAGE II trend at all altitudes. Underlying strong fluctuations in ozone anomaly due to El Niño–Southern Oscillation (ENSO), the altitude-dependent quasi-biennial oscillation, and tropopause pressure need to be taken into account to reduce trend uncertainties and, in the case of ENSO, to accurately determine the linear trend just above the tropopause. We also compare the observed ozone trend with a calculated trend that uses information on tropical upwelling and its temporal trend from model simulations, tropopause pressure trend information derived from reanalysis data, and vertical profiles from SAGE II and OSIRIS to determine the vertical gradient of ozone and its trend. We show that the observed trend agrees with the calculated trend and that the magnitude of the calculated trend is dominated by increased tropical upwelling, with minor but increasing contribution from the vertical ozone gradient trend as the tropical tropopause is approached. Improvements are suggested for future regression modelling efforts which could reduce trend uncertainties and biases in trend magnitudes, thereby allowing accurate trend detection to extend below 18 km

Electrically driven optical interferometry with spins in silicon carbide

Interfacing solid-state defect electron spins to other quantum systems is an ongoing challenge. The ground-state spin's weak coupling to its environment bestows excellent coherence properties, but also limits desired drive fields. The excited-state orbitals of these electrons, however, can exhibit stronger coupling to phononic and electric fields. Here, we demonstrate electrically driven coherent quantum interference in the optical transition of single, basally oriented divacancies in commercially available 4H silicon carbide. By applying microwave frequency electric fields, we coherently drive the divacancy's excited-state orbitals and induce Landau-Zener-Stuckelberg interference fringes in the resonant optical absorption spectrum. Additionally, we find remarkably coherent optical and spin subsystems enabled by the basal divacancy's symmetry. These properties establish divacancies as strong candidates for quantum communication and hybrid system applications, where simultaneous control over optical and spin degrees of freedom is paramount.Comment: 17 pages, 4 figure

Validation of 525 nm and 1020 nm aerosol extinction profiles derived from ACE imager data: comparisons with GOMOS, SAGE II, SAGE III, POAM III, and OSIRIS

International audienceThe Canadian ACE (Atmospheric Chemistry Experiment) mission is dedicated to the retrieval of a large number of atmospheric trace gas species using the solar occultation technique in the infrared and UV/visible spectral domain. However, two additional solar disk imagers (at 525 nm and 1020 nm) were added for a number of reasons, including the retrieval of aerosol and cloud products. In this paper, we present the first validation results for these imager aerosol/cloud optical extinction coefficient profiles, by intercomparison with profiles derived from measurements performed by 3 solar occultation instruments (SAGE II, SAGE III, POAM III), one stellar occultation instrument (GOMOS) and one limb sounder (OSIRIS). The results indicate that the ACE imager profiles are of good quality in the upper troposphere/lower stratosphere, although the aerosol extinction for the visible channel at 525 nm contains a significant negative bias at higher altitudes, while the profiles are systematically too high at 1020 nm. Both problems are probably related to ACE imager instrumental issues

UK Housing Market: Time Series Processes with Independent and Identically Distributed Residuals

The paper examines whether a univariate data generating process can be identified which explains the data by having residuals that are independent and identically distributed, as verified by the BDS test. The stationary first differenced natural log quarterly house price index is regressed, initially with a constant variance and then with a conditional variance. The only regression function that produces independent and identically distributed standardised residuals is a mean process based on a pure random walk format with Exponential GARCH in mean for the conditional variance. There is an indication of an asymmetric volatility feedback effect but higher frequency data is required to confirm this. There could be scope for forecasting the index but this is tempered by the reduction in the power of the BDS test if there is a non-linear conditional variance process

Purcell enhancement of a single silicon carbide color center with coherent spin control

Silicon carbide has recently been developed as a platform for optically addressable spin defects. In particular, the neutral divacancy in the 4H polytype displays an optically addressable spin-1 ground state and near-infrared optical emission. Here, we present the Purcell enhancement of a single neutral divacancy coupled to a photonic crystal cavity. We utilize a combination of nanolithographic techniques and a dopant-selective photoelectrochemical etch to produce suspended cavities with quality factors exceeding 5,000. Subsequent coupling to a single divacancy leads to a Purcell factor of ~50, which manifests as increased photoluminescence into the zero-phonon line and a shortened excited-state lifetime. Additionally, we measure coherent control of the divacancy ground state spin inside the cavity nanostructure and demonstrate extended coherence through dynamical decoupling. This spin-cavity system represents an advance towards scalable long-distance entanglement protocols using silicon carbide that require the interference of indistinguishable photons from spatially separated single qubits.Comment: 13 pages, 4 figure

Unravelling the Structure of Magnus' Pink Salt

A combination of multinuclear ultra-wideline solid-state NMR, powder X-ray diffraction (pXRD), X-ray absorption fine structure experiments, and first principles calculations of platinum magnetic shielding tensors has been employed to reveal the previously unknown crystal structure of Magnus’ pink salt (MPS), [Pt(NH3)4][PtCl4], study the isomeric Magnus’ green salt (MGS), [Pt(NH3)4][PtCl4], and examine their synthetic precursors K2PtCl4 and Pt(NH3)4Cl2·H2O. A simple synthesis of MPS is detailed which produces relatively pure product in good yield. Broad 195Pt, 14N, and 35Cl SSNMR powder patterns have been acquired using the WURST-CPMG and BRAIN-CP/WURST-CPMG pulse sequences. Experimentally measured and theoretically calculated platinum magnetic shielding tensors are shown to be very sensitive to the types and arrangements of coordinating ligands as well as intermolecular Pt–Pt metallophilic interactions. High-resolution 195Pt NMR spectra of select regions of the broad 195Pt powder patterns, in conjunction with an array of 14N and 35Cl spectra, reveal clear structural differences between all compounds. Rietveld refinements of synchrotron pXRD patterns, guided by first principles geometry optimization calculations, yield the space group, unit cell parameters, and atomic positions of MPS. The crystal structure has P-1 symmetry and resides in a pseudotetragonal unit cell with a distance of >5.5 Å between Pt sites in the square-planar Pt units. The long Pt–Pt distances and nonparallel orientation of Pt square planes prohibit metallophilic interactions within MPS. The combination of ultra-wideline NMR, pXRD, and computational methods offers much promise for future investigation and characterization of Pt-containing systems

Dynamics of electrons in the quantum Hall bubble phases

In Landau levels N > 1, the ground state of the two-dimensional electron gas (2DEG) in a perpendicular magnetic field evolves from a Wigner crystal for small filling of the partially filled Landau level, into a succession of bubble states with increasing number of guiding centers per bubble as the filling increases, to a modulated stripe state near half filling. In this work, we show that these first-order phase transitions between the bubble states lead to measurable discontinuities in several physical quantities such as the density of states and the magnetization of the 2DEG. We discuss in detail the behavior of the collective excitations of the bubble states and show that their spectra have higher-energy modes besides the pinned phonon mode. The frequencies of these modes, at small wavevector k, have a discontinuous evolution as a function of filling factor that should be measurable in, for example, microwave absorption experiments.Comment: 13 pages, 7 figures. Corrected typos in eqs. (38),(39),(40