In this paper we follow the Galactic enrichment of three easily observed light n-capture elements -Sr, Y, and Zr. Input stellar yields have been first separated into their respective main and weak s-process components, and r-process component. The s-process yields from Asymptotic Giant Branch (AGB) stars of low to intermediate mass are computed, exploring a wide range of efficiencies of the major neutron source, 13 C, and covering both disk and halo metallicities. AGB stars have been shown to reproduce the main s-component in the solar system, i.e., the s-process isotopic distribution of all heavy isotopes with atomic mass number A > 90, with a minor contribution to the light s-process isotopes up to A ∼ 90. The concurrent weak s-process, which accounts for the major fraction of the light s-process isotopes in the solar system and occurs in massive stars by the operation of the 22 Ne neutron source, is discussed in detail. Neither the main s-, nor the weak s-components are shown to contribute significantly to the neutron capture element abundances observed in unevolved halo stars. Knowing the sprocess distribution at the epoch of the solar system formation, we first employed the r-process residuals method to infer the isotopic distribution of the r-process. We assumed a primary r-process production in the Galaxy from moderately massive Type II supernovae that best reproduces the observational Galactic trend of metallicity versus Eu, an almost pure r-process element. We present a detailed analysis of a large published database of spectroscopic observations of Sr, Y, Zr, Ba, and Eu for Galactic stars at various metallicities, showing that the observed trends versus metallicity can be understood in light of a multiplicity of stellar neutron-capture components. Spectroscopic observations of the Sr, Y, and Zr to Ba and Eu abundance ratios versus metallicity provide useful diagnostics of the types of neutron-capture processes forming Sr, Y and Zr. In particular, the observed [Sr,Y,Zr/Ba,Eu] ratio is clearly not flat at low metallicities, as we would expect if Ba, Eu and Sr, Y, Zr all had the same r-process nucleosynthetic origin. We discuss our chemical evolution predictions, taking into account the interplay between different processes to produce Sr-Y-Zr. Making use of the very r-process-rich and very metal-poor stars like CS 22892-052 and CS 31082-001, we find hints, and discuss the possibility of a primary process in low-metallicity massive stars, different from the 'classical s-process' and from the 'classical rprocess', that we tentatively define LEPP (Lighter Element Primary Process). This allows us to revise the estimates of the r-process contributions to the solar Sr, Y and Zr abundances, as well as of the contribution to the s-only isotopes 86,87 Sr and 96 Mo.

The paper reviews recent advances in studies of electric discharges in the stratosphere and mesosphere above thunderstorms, and their effects on the atmosphere. The primary focus is on the sprite discharge occurring in the mesosphere, which is the most commonly observed high altitude discharge by imaging cameras from the ground, but effects on the upper atmosphere by electromagnetic radiation from lightning are also considered. During the past few years, co-ordinated observations over Southern Europe have been made of a wide range of parameters related to sprites and their causative thunderstorms. Observations have been complemented by the modelling of processes ranging from the electric discharge to perturbations of trace gas concentrations in the upper atmosphere. Observations point to significant energy deposition by sprites in the neutral atmosphere as observed by infrasound waves detected at up to 1000 km distance, whereas elves and lightning have been shown significantly to affect ionization and heating of the lower ionosphere/mesosphere. Studies of the thunderstorm systems powering high altitude discharges show the important role of intracloud (IC) lightning in sprite generation as seen by the first simultaneous observations of IC activity, sprite activity and broadband, electromagnetic radiation in the VLF range. Simulations of sprite ignition suggest that, under certain conditions, energetic electrons in the runaway regime are generated in streamer discharges. Such electrons may be the source of X-and Gamma-rays observed in lightning, thunderstorms and the so-called Terrestrial Gamma-ray Flashes (TGFs) observed from space over thunderstorm regions. Model estimates of sprite perturbations to the global atmospheric electric circuit, trace gas concentrations and atmospheric dynamics suggest significant local perturbations, and possibly significant meso-scale effects, but negligible global effects.

At 2336:56 UTC on 12 December 2009, a bright gigantic jet (GJ) was recorded by an observer in Italy. Forty‐nine additional sprites, elves, halos and two cases of upward lightning were observed that night. The location of the GJ corresponded to a distinct cloud top (−34°C) west of Ajaccio, Corsica. The GJ reached approximately 91 km altitude, with a “trailing jet” reaching 49–59 km, matching with earlier reported GJs. The duration was short at 120–160 ms. This is the first documented GJ which emerged from a maritime winter thunderstorm only 6.5 km tall, showing high cloud tops are not required for initiation of GJs. In the presence of strong vertical wind shear, the meteorological situation was different from typical outbreaks of fall and winter thunderstorms in the Mediterranean. During the trailing jet phase of the GJ, a sprite with halo triggered by a nearby cloud‐to‐ground lightning flash occurred at a relatively low altitude (<72 km). At the same time, the trailing jet and beads were reilluminated. Electromagnetic waveforms from Hungary, Poland, and the USA revealed this GJ is the first reported to transfer negative charge (approximately 136 C) from the ionosphere to the positively charged origins in the cloud (i.e., a positive cloud‐to‐ionosphere discharge, +CI), with a large total charge moment change of 11600 C km and a maximum current of 3.3 kA. Early VLF transmitter amplitude perturbations detected concurrently with the GJ confirm the production of large conductivity changes due to electron density enhancements in the D‐region of the ionosphere.

Abstract. We present results of a detailed chemical analysis performed on 23 main-sequence turnoff stars having −3.4 ≤ [Fe/H] ≤ −2.2, a sample selected to be highly homogeneous in T eff and log(g). We investigate the efficiency of mixing in the early Galaxy by means of the [Mg/Fe] ratio, and find that all values lie within a total range of 0.2 dex, with a standard deviation about the mean of 0.06 dex, consistent with measurement errors. This implies there is little or no intrinsic scatter in the early ISM, as suggested also by the most recent results from high-quality VLT observations. These results are in contrast with inhomogeneous Galactic chemical evolution (iGCE) models adopting present supernova (SN) II yields, which predict a peakto-peak scatter in [Mg/Fe] as high as 1 dex at very low metallicity, with a corresponding standard deviation of about 0.4 dex. We propose that cooling and mixing timescales should be investigated in iGCE models to account for the apparent disagreement with present observations. The contrast between the constancy and small dispersion of [Mg/Fe] reported here and the quite different behaviour of [Ba/Fe] indicates, according to this interpretation, that Mg and Ba are predominantly synthesised in different progenitor mass ranges.

Abstract. Transient luminous events, such as red sprites, occur in the middle atmosphere in the electric field above thunderstorms. We here address the question whether these processes may be a significant source of odd nitrogen and affect ozone or other important trace species. A well-established coupled ion-neutral chemical model has been extended for this purpose and applied together with estimated rates of ionisation, excitation and dissociation based on spectroscopic ratios from ISUAL on FORMOSAT-2. This approach is used to estimate the NO x and ozone changes for two type cases.The NO x enhancements are at most one order of magnitude in the streamers, which means a production of at most 10 mol per event, or (given a global rate of occurrence of three events per minute) some 150-1500 kg per day. The present study therefore indicates that sprites are insignificant as a global source of NO x . Local effects on ozone are also negligible, but the local enhancement of NO x may be significant, up to 5 times the minimum background at 70 km in extraordinary cases.

Abstract. We present observations of the 2010-2011 Arctic winter stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. Limb sounding infrared measurements were taken by MIPAS during the Northern polar winter and into the subsequent spring, giving a continuous vertically resolved view of the Arctic dynamics, chemistry and polar stratospheric clouds (PSCs). We adopted a 2-D tomographic retrieval approach to account for the strong horizontal inhomogeneity of the atmosphere present under vortex conditions, self-consistently comparing 2011 to the 2-D analysis of [2003][2004][2005][2006][2007][2008][2009][2010]. Unlike most Arctic winters, 2011 was characterized by a strong stratospheric vortex lasting until early April. Lower stratospheric temperatures persistently remained below the threshold for PSC formation, extending the PSC season up to midMarch, resulting in significant chlorine activation leading to ozone destruction. On 3 January 2011, PSCs were detected up to 30.5 ± 0.9 km altitude, representing the highest PSCs ever reported in the Arctic. Through inspection of MIPAS spectra, 83 % of PSCs were identified as supercooled ternary solution (STS) or STS mixed with nitric acid trihydrate (NAT), 17 % formed mostly by NAT particles, and only two cases by ice. In the lower stratosphere at potential temperature 450 K, vortex average ozone showed a daily depletion rate reaching 100 ppbv day −1 . In early April at 18 km altitude, 10 % of vortex measurements displayed total depletion of ozone, and vortex average values dropped to 0.6 ppmv. This corresponds to a chemical loss from early winter greater than 80 %. Ozone loss was accompanied by activation of ClO, associated depletion of its reservoir ClONO 2 , and significant denitrification, which further delayed the recovery of ozone in spring. Once the PSC season halted, ClO was reconverted primarily into ClONO 2 . Compared to MIPAS observed [2003][2004][2005][2006][2007][2008][2009][2010] Arctic average values, the 2010-2011 vortex in late winter had 15 K lower temperatures, 40 % lower HNO 3 and 50 % lower ozone, reaching the largest ozone depletion ever observed in the Arctic. The overall picture of this Arctic winter was remarkably closer to conditions typically found in the Antarctic vortex than ever observed before.

Quantifying rates of climate change in mountain regions is of considerable interest, not least because mountains are viewed as climate “hotspots” where change can anticipate or amplify what is occurring elsewhere. Accelerating mountain climate change has extensive environmental impacts, including depletion of snow/ice reserves, critical for the world's water supply. Whilst the concept of elevation‐dependent warming (EDW), whereby warming rates are stratified by elevation, is widely accepted, no consistent EDW profile at the global scale has been identified. Past assessments have also neglected elevation‐dependent changes in precipitation. In this comprehensive analysis, both in situ station temperature and precipitation data from mountain regions, and global gridded data sets (observations, reanalyses, and model hindcasts) are employed to examine the elevation dependency of temperature and precipitation changes since 1900. In situ observations in paired studies (using adjacent stations) show a tendency toward enhanced warming at higher elevations. However, when all mountain/lowland studies are pooled into two groups, no systematic difference in high versus low elevation group warming rates is found. Precipitation changes based on station data are inconsistent with no systematic contrast between mountain and lowland precipitation trends. Gridded data sets (CRU, GISTEMP, GPCC, ERA5, and CMIP5) show increased warming rates at higher elevations in some regions, but on a global scale there is no universal amplification of warming in mountains. Increases in mountain precipitation are weaker than for low elevations worldwide, meaning reduced elevation‐dependency of precipitation, especially in midlatitudes. Agreement on elevation‐dependent changes between gridded data sets is weak for temperature but stronger for precipitation.

[1] Subionospheric VLF recordings are investigated in relation with intense cloud-to-ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long-recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short-lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long-lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ± CG lightning peak currents of typically > 250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within~250 km from the great circle path of a VLF transmitter-receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents ≥~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ± CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long-going VLF research of lightning effects in the lower ionosphere.Citation: Haldoupis, C., M. Cohen, E. Arnone, B. Cotts, and S. Dietrich (2013), The VLF fingerprint of elves:Step-like and long-recovery early VLF perturbations caused by powerful ±CG lightning EM pulses,