The genetic history of admixture across inner Eurasia

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record.Data Availability. Genome-wide sequence data of two Botai individuals (BAM format) are available at the European Nucleotide Archive under the accession number PRJEB31152 (ERP113669). Eigenstrat format array genotype data of 763 present-day individuals and 1240K pulldown genotype data of two ancient Botai individuals are available at the Edmond data repository of the Max Planck Society (https://edmond.mpdl.mpg.de/imeji/collection/Aoh9c69DscnxSNjm?q=).The indigenous populations of inner Eurasia, a huge geographic region covering the central Eurasian steppe and the northern Eurasian taiga and tundra, harbor tremendous diversity in their genes, cultures and languages. In this study, we report novel genome-wide data for 763 individuals from Armenia, Georgia, Kazakhstan, Moldova, Mongolia, Russia, Tajikistan, Ukraine, and Uzbekistan. We furthermore report additional damage-reduced genome-wide data of two previously published individuals from the Eneolithic Botai culture in Kazakhstan (~5,400 BP). We find that present-day inner Eurasian populations are structured into three distinct admixture clines stretching between various western and eastern Eurasian ancestries, mirroring geography. The Botai and more recent ancient genomes from Siberia show a decrease in contribution from so-called “ancient North Eurasian” ancestry over time, detectable only in the northern-most “forest-tundra” cline. The intermediate “steppe-forest” cline descends from the Late Bronze Age steppe ancestries, while the “southern steppe” cline further to the South shows a strong West/South Asian influence. Ancient genomes suggest a northward spread of the southern steppe cline in Central Asia during the first millennium BC. Finally, the genetic structure of Caucasus populations highlights a role of the Caucasus Mountains as a barrier to gene flow and suggests a post-Neolithic gene flow into North Caucasus populations from the steppe.Max Planck SocietyEuropean Research Council (ERC)Russian Foundation for Basic Research (RFBR)Russian Scientific FundNational Science FoundationU.S. National Institutes of HealthAllen Discovery CenterUniversity of OstravaCzech Ministry of EducationXiamen UniversityFundamental Research Funds for the Central UniversitiesMES R

The Far Ultra-Violet Imager on the Icon Mission

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far Ultra- Violet (FUV) imager is a Czerny–Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft

Swarm equatorial electric field chain: First results

International audienceThe eastward equatorial electric field (EEF) in the E region ionosphere drives many important phenomena at low latitudes. We developed a method of estimating the EEF from magnetometer measurements of near-polar orbiting satellites as they cross the magnetic equator, by recovering a clean signal of the equatorial electrojet current and modeling the observed current to determine the electric field present during the satellite pass. This algorithm is now implemented as an official Level-2 Swarm product. Here we present first results of EEF estimates from nearly a year of Swarm data. We find excellent agreement with independent measurements from the ground-based coherent scatter radar at Jicamarca, Peru, as well as horizontal field measurements from the West African Magnetometer Network magnetic observatory chain. We also calculate longitudinal gradients of EEF measurements made by the A and C lower satellite pair and find gradients up to about 0.05 mV/m/deg with significant longitudinal variability

Neutral Ion Coupling Explorer satellite measurements of thermospheric composition, winds and temperatures.

A new Small Explorer mission, the Neutral Ion Coupling Explorer (NICE) mission, was selected for study by NASA to specifically address neutral ion coupling in the Earth's atmosphere. The main goal of NICE is to study neutral-ion coupling at low latitudes where the densest plasma in geospace is created and where a number of remarkable interactions between the plasma and neutral gas occur even in the relative absence of high-latitude forcing. NICE will study this region from a ~24 degree inclination 550 km circular orbit, residing entirely on closed magnetic field lines. The relatively fast precession of low-inclination orbit is favorable for frequent sampling of all local times for the determination of tidal structures. It is now widely recognized that the neutral thermosphere has a strong influence on the ionosphere and that Earth's ionosphere at quiet times is actually tidally dominated. The NICE concept is unique in simultaneously providing measurements of the parameters relevant to ion production and motion across the entire altitude range of the low-latitude ionosphere. The science payload consists of 3 remote sensing instruments viewing the atmospheric limb (1) a dual Doppler Fabry-Perot Interferometer (FP), scanning in altitude to measure neutral wind vector and temperature altitude profiles in the E- and F-regions, (2) a Far Ultraviolet (FUV) imager to measure daytime neutral composition and image the nighttime F-layer intensity distributions, and (3) an Extreme Ultraviolet (EUV) altitude profiler to retrieve daytime F-layer properties. In addition, an Ion Velocity Meter (IVM) measures the in-situ ion drifts. NICE will take advantage of an elegant choice of orbit and instrument viewing geometries to make coordinated and complementary observations at all local times, with optimal conjunction of measurements occurring near the equator. The observations are accompanied by a suite of advanced numerical models and analysis techniques