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AbstractIn recent years, there has been a growing body of direct experimental evidence demonstrating electromagnetic ion cyclotron (EMIC) waves driving energetic electron precipitation (EEP) at unexpectedly low, sub‐MeV energies—as low as only a few hundred keV. EMIC‐wave driven scattering at these energies has important ramifications for our understanding of not only radiation belt electron dynamics, but also the importance of EMIC‐driven EEP to the chemical balance of the Earth's atmosphere. In this study, we use three experimentally derived EMIC‐driven EEP flux spectra to investigate the impact of this precipitation on trapped radiation belt fluxes. In doing so, we resolve an apparent contradiction with earlier results derived from trapped electron flux populations that suggested EMIC waves only caused significant scattering at ultrarelativistic energies. We show that strong sub‐MeV EEP measurements are not necessarily mutually exclusive with a strongly relativistic‐only trapped flux response, as the sub‐MEV peak precipitation is comparatively much smaller than the trapped population at those energies. Using a further six EEP spectra, we also demonstrate that EMIC‐driven EEP can generate significant ionization of the Earth's atmosphere above 40 km, leading to the loss of mesospheric ozone. We find poor correlation between EMIC‐driven EEP fluxes and geomagnetic activity proxies, such that EMIC‐driven EEP is likely to be poorly specified in the forcing factors of modern coupled‐climate models.

Pangeo[1] is a community-driven effort for open-source big data initially focused on the Earth System Sciences. One of its primary goals is to enable scientists in analyzing petascale datasets both on classical high-performance computing (HPC) and on public cloud infrastructure. In only a few years, Pangeo has grown into a very productive community collaborating on the development of open-source analysis tools for science. It provides a set of example deployments based on open-source Scientific Python packages like Jupyter[2], Dask[3], and Xarray[4] that bring together scientists and developer with their actual use-cases. In this paper, we first describe Pangeo ecosystem and community. We then present its impact on the work of scientists from CNES on the HPC deployment there. We conclude with a future outlook for Pangeo in this agency and beyond.

The Brassicaceae include several major crop plants and numerous important model species in comparative evolutionary research such as Arabidopsis, Brassica, Boechera, Thellungiella, and Arabis species. As any evolutionary hypothesis needs to be placed in a temporal context, reliably dated major splits within the evolution of Brassicaceae are essential. We present a comprehensive time-calibrated framework with important divergence time estimates based on whole-chloroplast sequence data for 29 Brassicaceae species. Diversification of the Brassicaceae crown group started at the Eocene-to-Oligocene transition. Subsequent major evolutionary splits are dated to ∼20 million years ago, coinciding with the Oligocene-to-Miocene transition, with increasing drought and aridity and transient glaciation events. The age of the Arabidopsis thaliana crown group is 6 million years ago, at the Miocene and Pliocene border. The overall species richness of the family is well explained by high levels of neopolyploidy (43% in total), but this trend is neither directly associated with an increase in genome size nor is there a general lineage-specific constraint. Our results highlight polyploidization as an important source for generating new evolutionary lineages adapted to changing environments. We conclude that species radiation, paralleled by high levels of neopolyploidization, follows genome size decrease, stabilization, and genetic diploidization.

In this paper, the authors introduce an algorithm for locating sound-producing fish in a small rectangular tank that can be used, e.g., in behavioral bioacoustical studies to determine which fish in a group is sound-producing. The technique consists of locating a single sound source in the tank using signals gathered by four hydrophones placed in the tank together with a group of fish under study. The localization algorithm used in this paper is based on a ratio of two spectra ratios: the spectra ratio between the sound pressure measured by hydrophones at two locations and the spectra ratio between the theoretical Green's functions at the same locations. The results are compared to a localization based on image processing technique and with video recordings acquired synchronously with the acoustic recordings.

Peatlands store substantial amounts of carbon and are vulnerable to climate change. We present a modified version of the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface model for simulating the hydrology, surface energy, and CO2 fluxes of peatlands on daily to annual timescales. The model includes a separate soil tile in each 0.5° grid cell, defined from a global peatland map and identified with peat-specific soil hydraulic properties. Runoff from non-peat vegetation within a grid cell containing a fraction of peat is routed to this peat soil tile, which maintains shallow water tables. The water table position separates oxic from anoxic decomposition. The model was evaluated against eddy-covariance (EC) observations from 30 northern peatland sites, with the maximum rate of carboxylation (Vcmax) being optimized at each site. Regarding short-term day-to-day variations, the model performance was good for gross primary production (GPP) (r2 = 0.76; Nash–Sutcliffe modeling efficiency, MEF = 0.76) and ecosystem respiration (ER, r2 = 0.78, MEF = 0.75), with lesser accuracy for latent heat fluxes (LE, r2 = 0.42, MEF = 0.14) and and net ecosystem CO2 exchange (NEE, r2 = 0.38, MEF = 0.26). Seasonal variations in GPP, ER, NEE, and energy fluxes on monthly scales showed moderate to high r2 values (0.57–0.86). For spatial across-site gradients of annual mean GPP, ER, NEE, and LE, r2 values of 0.93, 0.89, 0.27, and 0.71 were achieved, respectively. Water table (WT) variation was not well predicted (r2 cmax and latitude (temperature), which better reflects the spatial gradients of annual NEE than using an average Vcmax value. Source at https://doi.org/10.5194/gmd-11-497-2018.

AbstractPulsating auroras show quasi‐periodic intensity modulations caused by the precipitation of energetic electrons of the order of tens of keV. It is expected theoretically that not only these electrons but also subrelativistic/relativistic electrons precipitate simultaneously into the ionosphere owing to whistler mode wave‐particle interactions. The height‐resolved electron density profile was observed with the European Incoherent Scatter (EISCAT) Tromsø VHF radar on 17 November 2012. Electron density enhancements were clearly identified at altitudes >68 km in association with the pulsating aurora, suggesting precipitation of electrons with a broadband energy range from ~10 keV up to at least 200 keV. The riometer and network of subionospheric radio wave observations also showed the energetic electron precipitations during this period. During this period, the footprint of the Van Allen Probe‐A satellite was very close to Tromsø and the satellite observed rising tone emissions of the lower band chorus (LBC) waves near the equatorial plane. Considering the observed LBC waves and electrons, we conducted a computer simulation of the wave‐particle interactions. This showed simultaneous precipitation of electrons at both tens of keV and a few hundred keV, which is consistent with the energy spectrum estimated by the inversion method using the EISCAT observations. This result revealed that electrons with a wide energy range simultaneously precipitate into the ionosphere in association with the pulsating aurora, providing the evidence that pulsating auroras are caused by whistler chorus waves. We suggest that scattering by propagating whistler simultaneously causes both the precipitations of subrelativistic electrons and the pulsating aurora.

Vertebrates have greatly elaborated the basic chordate body plan and evolved highly distinctive genomes that have been sculpted by two whole-genome duplications. Here we sequence the genome of the Mediterranean amphioxus (Branchiostoma lanceolatum) and characterize DNA methylation, chromatin accessibility, histone modifications and transcriptomes across multiple developmental stages and adult tissues to investigate the evolution of the regulation of the chordate genome. Comparisons with vertebrates identify an intermediate stage in the evolution of differentially methylated enhancers, and a high conservation of gene expression and its cis-regulatory logic between amphioxus and vertebrates that occurs maximally at an earlier mid-embryonic phylotypic period. We analyse regulatory evolution after whole-genome duplications, and find that—in vertebrates—over 80% of broadly expressed gene families with multiple paralogues derived from whole-genome duplications have members that restricted their ancestral expression, and underwent specialization rather than subfunctionalization. Counter-intuitively, paralogues that restricted their expression increased the complexity of their regulatory landscapes. These data pave the way for a better understanding of the regulatory principles that underlie key vertebrate innovations. © 2018, Springer Nature Limited. Acknowledgements This research was funded primarily by the European Research Council (ERC) under the European Union’s Horizon 2020 and Seventh Framework Program FP7 research and innovation programs (ERC-AdG-LS8-740041 to J.L.G.-S., ERC-StG-LS2-637591 to M.I., a Marie Sklodowska-Curie Grant (658521) to I.M. and a FP7/2007-2013-ERC-268513 to P.W.H.H.), the Spanish Ministerio de Economía y Competitividad (BFU2016-74961-P to J.L.G.-S., RYC-2016-20089 to I.M., BFU2014-55076-P and BFU2017-89201-P to M.I. and BFU2014-55738-REDT to J.L.G.-S, M.I. and J.R.M.-M), the ‘Centro de Excelencia Severo Ochoa 2013-2017’(SEV-2012-0208), the ‘Unidad de Excelencia María de Maetzu 2017-2021’(MDM-2016-0687), the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program FP7 under REA grant agreement number 607142 (DevCom) to J.L.G.-S., and the CNRS and the ANR (ANR16-CE12-0008-01) to H.E. O.B. was supported by an Australian Research Council Discovery Early Career Researcher Award (DECRA; DE140101962). We acknowledge the support of the CERCA Programme/Generalitat de Catalunya and of the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) to the EMBL partnership. Additional sources of funding for all authors are listed in Supplementary Information.