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Isotopic abundances in comets are key to understanding the history and origin of material in the Solar System. Deuterium-to-hydrogen (D/H) ratios in water are available for several comets. However, no long-term studies of the D/H ratio in water of a comet during its passage around the Sun have been reported. Linear alkanes are important organic molecules, which have been found on several Solar System bodies, including comets. To date, only upper limits of isotopic ratios for D/H and 13C/12C in linear alkanes are available. The aim of this work is a detailed analysis of the D/H ratio in water during the whole Rosetta mission. In addition, a first determination of the D/H and 13C/12C ratios in the first four linear alkanes in the coma of 67P/Churyumov-Gerasimenko is provided. We analysed in situ measurements from the Rosetta/ROSINA Double Focusing Mass Spectrometer (DFMS). The D/H ratio from HDO/H2O and the 16O/17O ratio from H216O/H217O did not change during 67P's passage around the Sun between 2014 and 2016. All D/H ratio measurements were compatible, within 1$\sigma$, with the mean value of $5.01\times10^{-4}$ and its relative variation of 2.0%. This suggests that the D/H ratio in 67P's coma is independent of heliocentric distance, level of cometary activity, as well as spacecraft location with respect to the nucleus. Additionally, the 16O/17O ratio could be determined with a higher accuracy than previously possible, yielding a value of 2347 with a relative variation of 2.3%. For the alkanes, the D/H ratio is between 4.1 and 4.8 times higher than in H2O, while the 13C/12C ratio is compatible, within uncertainties, with data for other Solar System objects. The relatively high D/H ratio in alkanes is in line with other cometary organic molecules and suggests that these organics may be inherited from the presolar molecular cloud from which the Solar System formed., Comment: Accepted for publication in A&A

We examine the circulation of heavy ions of planetary origin within Mercury’s magnetosphere. Using single particle trajectory calculations, we focus on the dynamics of sodium ions, one of the main species that are ejected from the planet’s surface. The numerical simulations reveal a significant population in the near-Mercury environment in the nightside sector, with energetic (several keV) Na + densities that reach several tenths cm-3 at planetary perihelion. At aphelion, a lesser (by about one order of magnitude) density contribution is obtained, due to weaker photon flux and solar wind flux. The numerical simulations also display several features of interest that follow from the small spatial scales of Mercury’s magnetosphere. First, in contrast to the situation prevailing at Earth, ions in the magnetospheric lobes are found to be relatively energetic (a few hundreds of eV), despite the low-energy character of the exospheric source. This results from enhanced centrifugal acceleration during E × B transport over the polar cap. Second, the large Larmor radii in the mid-tail result in the loss of most Na + into the dusk flank at radial distances greater than a few planetary radii. Because gyroradii are comparable to, or larger than, the magnetic field variation length scale, the Na + motion is also found to be non-adiabatic throughout most of Mercury’s equatorial magnetosphere, leading to chaotic scattering into the loss cone or meandering (Speiser-type) motion in the near-tail. As a direct consequence, a localized region of energetic Na + precipitation develops at the planet’s surface. In this region which extends over a wide range of longitudes at mid-latitudes ( ~ 30°–40°), one may expect additional sputtering of planetary material.Key words. Magnetospheric physics (planetary magnetospheres) – Space plasma physics (charged particle motion and acceleration; numerical simulation studies)

International audience; The knowledge about sulphur isotopic fractionation in volatile cometary species is limited as only measurements in five comets have been done and only for 34S/32S. The lack of information about the fractionation of 33S/32S makes it impossible to compare them with what is known from refractories. We present results of 34S/32S and for the first time 33S/32S isotopic ratio in H2S, OCS, and CS2 in the coma of comet 67P/Churyumov-Gerasimenko. Observations used for this study were performed with Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer during October 2014 and May 2016. Bulk isotopic 33S/32S and 34S/32S ratio derived from these three species yield δ33S = (-302 ± 29)‰ and δ34S = (-41 ± 17)‰ respectively. The observed isotopic fractionation is significantly different from the solar system standard (V-CDT) and all other reported values for solar system objects, except other comets. Furthermore we show that neither mass dependent nor mass-independent fractionation due to photo dissociation as it has been observed in recent laboratory studies can be the cause of the significant depletion compared to solar system standard. In addition, we conclude that there seems to be an intrinsic difference in sulphur isotopic fractionation in cometary volatiles and refractories while the difference between molecules is most likely due to different chemical pathways. The significant fractionation of sulphur isotopes together with a high D2O/HDO vs. HDO/H2O and non-solar isotopic ratio for xenon (Marty 2017) as well as for Si (Marty 2017) point towards a non-homogeneously mixed protosolar nebula.

This paper presents EMC measurements from the ‘Planetary ion camera’ (PICAM) instrument, a part of the SERENA instrument suite aboard BepiColombo, an ESA/JAXA two spacecraft mission to the Hermean system. After a short description of the scientific goals and PICAM characteristics, we focus on results obtained by the QM and FM. For the electronics boards and the ion optics conducted emission and susceptibility are of particular interest in order to meet the instrument requirements. Relevant are interferences on the gates or high voltage electrodes, i.e. finally disturbances of the ion trajectories, they have to be avoided and considered in the design improvement of the models.

The development of deep plasma depletions in the equatorial ionosphere at time of magnetic storms is of particular interest in space and plasma physics as well as in the field of radio communications. Detailed plasma, dc electric field, and wave observations were performed by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions microsatellite through several depletions where the large Debye length may lead to significant disturbances on the measurements of dc electric fields by the double probe instrument. After an overview of the data acquired in a well-developed plasma cavity, we present a numerical simulation study that was undertaken to model the operation of the electric field probes in their actual environment. The initial results indicate that, in low-density ionospheric plasma and depending on the potential difference between the probes and the boom, non negligible errors may arise from the influence of the boom on the probe current collection.

Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface.

The PicUp3D code is a prototype of simulation software dedicated to quantitative and accurate modeling of spacecraft plasma interactions developed in the context of a European scientific and industrial network Spacecraft Plasma Interaction Network in Europe. It is based on a full three-dimensional kinetic particle-in-cell description of the electrons and the ion dynamics. The use of unstructured schemes in the spacecraft geometrical description has allowed to model successfully realistic geometries. The code is organized around an open and versatile object-oriented library and is fully written in JAVA. This paper presents the basic features and the first validation tests of PicUp3D, which are now made publicly and freely available on the Web. Developed in an open-source approach, it is believed that this code will meet the requirements of the scientific community in terms of geometric and physics accuracy especially for instrument calibration and observation analysis

Molecular oxygen produced by the decomposition of icy surfaces is ubiquitous in Saturn's magnetosphere. A model is described for the toroidal O2 atmosphere indicated by the detection of O 2 + and O+ over the main rings. The O2 ring atmosphere is produced primarily by UV photon-induced decomposition of ice on the sunlit side of the ring. Because O2 has a long lifetime and interacts frequently with the ring particles, equivalent columns of O2 exist above and below the ring plane with the scale height determined by the local ring temperature. Energetic particles also decompose ice, but estimates of their contribution over the main rings appear to be very low. In steady state, the O2 column density over the rings also depends on the relative efficiency of hydrogen to oxygen loss from the ring/atmosphere system with oxygen being recycled on the grain surfaces. Unlike the neutral density, the ion densities can differ on the sunlit and shaded sides due to differences in the ionization rate, the quenching of ions by the interaction with the ring particles, and the northward shift of the magnetic equator relative to the ring plane. Although O+ is produced with a significant excess energy, O 2 + is not. Therefore, O 2 + should mirror well below those altitudes at which ions were detected. However, scattering by ion–molecule collisions results in much larger mirror altitudes, in ion temperatures that go through a minimum over the B-ring, and in the redistribution of both molecular hydrogen and oxygen throughout the magnetosphere. The proposed model is used to describe the measured oxygen ion densities in Saturn's toroidal ring atmosphere and its hydrogen content. The oxygen ion densities over the B-ring appear to require either significant levels of UV light scattering or ion transmission through the ring plane.

The provenance of water and organic compounds on Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the deuterium-to-hydrogen (D/H) ratios in the reservoirs for comets and Earth's oceans. Here, we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard the European Space Agency's Rosetta spacecraft, which is found to be (5.3 ± 0.7) × 10(-4)—that is, approximately three times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean-like water.

We present a novel ion mass spectrometer designed to measure thermal and low-energy suprathermal ion populations of planetary and cometary environments on board a three-axis-stabilized spacecraft. It consists of three main parts: an electrostatic analyser to perform the angular and energy scans, a magnetic analyser to provide the mass separation and a position-sensitive detector in the focal plane of the magnet. The instrument has a 2 field of view divided into 16 azimuthal sectors with continuous-elevation scanning between 0 and 90°. A high-resolution cylindrical energy analyser with adjustable energy resolution allows measurement of the temperature and velocity of thermal ions and the energy spectrum of suprathermal ions. The mass range extends from 1 to 45 amu/q . Comparisons between numerical simulation and laboratory tests of a prototype are presented.

International audience; We report DEMETER observations of a truncated VLF (Very Low Frequency) saucer in the auroral ionosphere. The very unusual shape of the frequency-time spectrogram arises from the sharp disappearance of the emissions below a frequency which displays a small and regular variation along the orbit. This low frequency cutoff results from the altitude variation of the LHF (Lower Hybrid Frequency) which is higher below the satellite than at the satellite altitude.

International audience; The paper is related to specific emissions at frequency < 3 MHz observed by the low altitude satellite DEMETER in relation with the thunderstorm activity. At its altitude (similar to 700 km), the phenomena observed on the E-field and B-field spectrograms recorded by the satellite are mainly dominated by whistlers. Particular observations performed by DEMETER are reported. It concerns multiple hop whistlers and interaction between whistlers and lower hybrid noise. Two new phenomena discovered by the satellite are discussed. First, V-shaped emissions up to 20 kHz are observed at mid-latitude during night time. They are centered at the locations of intense thunderstorm activity. By comparison with VLF saucers previously observed by other satellites in the auroral zones it is hypothesized that the source region is located below the satellite and that the triggering mechanism is due to energetic electrons accelerated during sprite events. Second, emissions at frequency similar to 2 MHz are observed at the time of intense whistlers. These emissions are produced in the lower ionosphere in probable relation with Transient Luminous Events (TLEs).

SEISMOLOGY & EARTHQUAKES P11 - 06 GPS AND DEMETER/ICE SPACE OBSERVATIONS: CASE STUDY OF ADRIATIC SEISMIC EVENTS Summary E. Cristea 1 M.Y. Boudjada 1 K. Schwingenschuh 1 J.J. Berthelier 2 M. Vellante 3 P. Nenovski 4 M. Parrot 5 P. Pesec 1 H.O Rucker 1 6 M. Stachel 1 W. Voller 1 W. Magnes 1 1 Space Research Institute Austrian Academy of Sciences Graz Austria 2 Centre d'Etude des Environnements Terrestre et Planetaires Observatoire de Saint-Maur France 3 Department of Physics University of l'Aquila l’Aquila Italy 4 Geophysical Institute Sofia Bulgaria 5 Laboratoire de Physique et Chimie de l'Environnement Orleans

Research has shown that spectrometers measuring low energy ions are essential tools for investigating both the spatial extent and the physical nature of ion acceleration processes in the Earth's ionized environment. Such a device was one of a number of experiments onboard the Interball Auroral Probe (Interball AP) launched by the Russian Space Agency in 1996. Such in situ measurements are crucial for understanding the dynamics of the Earth's ionized environment and offer an excellent opportunity for analyzing fundamental plasma processes that usually can be observed only remotely. In a way similar to the solar corona, the Earth's ionosphere and low-altitude magnetosphere are affected by an expansion process. At high latitudes in the auroral and polar regions, pressure gradients and ambipolar electric fields are responsible for a so-called “polar wind” flowing out of the topside ionosphere at low energies (several eVs). In addition to this “classical” polar wind picture, other processes also lead to significant plasma ejection into the magnetosphere.

The Giotto space probe's neutral mass spectrometer experiment has determined the abundances and the chemical, elemental and isotopic compositions of gases and low energy ions in the coma of comet Halley. Preliminary results show water predominating, at about 80 percent by volume, with a density of 4.7 x 10 to the 7th molecules/cu cm at 1000 km and a photodestruction scale length of 39,000 km. Limits on the abundances of CO2, NH3 and CH4 relative to H2O are also obtained. An ion temperature change observation indicates a contact surface location at 47,000 + or - 200 km.

In situ measurements of flow velocity and temperature in the inner coma were obtained from ram energy spectra of molecules and ions observed by the NMS experiment onboard the Giotto probe to comet Halley. Radial flow speed was (800 ± 50) m s−1 at distances from the nucleus between 1000 km and 4000 km. Whereas ions became stagnant just outside the contact surface (located near 4500 km), the outflow of water vapour even accelerated and was above 1 km s −1 at 30000 km. Ion temperatures were around 200 K inside the contact surface where the plasma is collisionally coupled to the gas; at this boundary ion temperature rises by about 1000 K and then further increases to reach about 5000 K at 15 000 km. Gas temperature remains below 300–500 K over this range of distances. A near zero volt spacecraft potential was inferred.

A preliminary evaluation of the mass 28 amu/e signal observed in the neutral mode of the Giotto neutral gas mass spectrometer (NMS) is presented. At 1000 km from the nucleus we obtain for the CO number density n (CO)/n (H2O)≦0.07. The production rate of CO as a parent molecule directly from the nucleus is thus less than 7% of the H2O production rate. However, CO is also produced from an extended source in the inner coma (R < 20 000 km) and at 20 000 km from the nucleus we obtain for the total equivalent CO production rate 0.05≦Q (CO)/Q (H2O)≦0.15. For N2 an upper limit Q (N2)/Q (H2O)≦0.1 is derived. No parent molecule for the CO could be identified which would be in agreement with the NMS measurements. It is proposed that CO or a very short-lived parent is relased in the coma from cometary dust grains, such as the “CHON” particles.

The neutral gas mass spectrometer (NMS) on the Giotto spacecraft made neutral and ion composition measurements with a high mass resolution. From a preliminary evaluation of the ion data within the contact surface we obtain for the water in Halley an18O abundance of 18O/16O = 0.0023 ± 0.0006 and for the D/H ratio 0.610−4 ≦ D/H ≦ 4.8 10−4. The cometary 18Oabundance is within error limits identical to the terrestrial one. The D/H ratio in Halley is definitely not compatible with the D/H in gaseous hydrogen of the protosolar nebula or the Jovian and Saturnian atmospheres. It is in the range observed for hydrogen in solar system objects which acquired their hydrogen as part of volatile molecules, e.g. as ices.

International audience; The determination of the D‐region electron‐density profile may be obtained by the solution of an integral equation when the absorption at several frequencies is known. A new method based upon an iterative process is derived and is found to be more reliable than the previous methods.

International audience; Recent low energy particle measurements (Frank, 1971; Frank and Ackerson, 1972) and photometric observations (Eather and Mende, 1971) have shown that in a ring extending (for Kp≲3) from ∼78° to 85° IN Lat in the noon sector and ∼72° to 80° in the midnight sector most of the corpuscular energy input is due to soft particles: by transuroral regions we shall refer to this ring-shaped zone. Its existence was disclosed a few years ago on the basis of ionospheric observations (e.g., Nelms and Chapman, 1970) and it is. clear that the behavior of the transauroral ionosphere is essentially dominated by magnetospheric processes and magnetosphere-ionosphere coupling.

In the theory of electrostatic probes, it is usually assumed that the probe surface potential is uniform. However, nonuniformity of the surface work function produces a nonuniformity in surface potential which may modify the current collection. This effect is examined for an infinite cylinder immersed in a collisionless plasma in the limit when Debye length is much greater than probe radius, by numerically following charged-particle orbits in a Laplace potential. It is shown that only large-scale, macroscopic potential nonuniformities are important for the current collection, and that microscopic nonuniformities are smoothed over relatively short distance by the Laplace equation character of the potential.