scholarly journals RPC-MIP observations at comet 67P/Churyumov-Gerasimenko explained by a model including a sheath and two populations of electrons

2019 ◽  
Vol 630 ◽  
pp. A41 ◽  
Author(s):  
G. Wattieaux ◽  
N. Gilet ◽  
P. Henri ◽  
X. Vallières ◽  
L. Bucciantini
Keyword(s):  
Collisionless Plasma ◽  
Plasma Sheath ◽  
Sheath Thickness ◽  
Mutual Impedance ◽  
Cometary Plasma ◽  
Rosetta Mission ◽  
Impedance Probe ◽  
First Time ◽  
Two Populations ◽  
Comet 67P

The response of the mutual impedance probe RPC-MIP on board Rosetta orbiter electrostatically modeled considering an unmagnetized and collisionless plasma with two Maxwellian electron populations. A vacuum sheath surrounding the probe was considered in our model in order to take the ion sheath into account that is located around the probe, which is immersed in the cometary plasma. For the first time, the simulated results are consistent with the data collected around comet 67P/Churyumov-Gerasimenko (67P), but strong discrepancies were identified with the previous simulations that neglected the plasma sheath around the probe. We studied the influence of the sheath thickness and of the electron populations. This work helps to better understand the initially unexpected responses of the mutual impedance probe that were acquired during the Rosetta mission. It suggests that two electron populations exist in the cometary plasma of 67P.

scholarly journals Plasma characterization at comet 67P between 2 and 4 AU from the Sun with the RPC-MIP instrument

2020 ◽  
Vol 638 ◽  
pp. A124
Author(s):  
Gaëtan Wattieaux ◽  
Pierre Henri ◽  
Nicolas Gilet ◽  
Xavier Vallières ◽  
Jan Deca
Keyword(s):  
Temperature Ratio ◽  
Electron Densities ◽  
Plasma Parameters ◽  
Mutual Impedance ◽  
Rosetta Mission ◽  
Fluctuation Range ◽  
Impedance Probe ◽  
Cold Electrons ◽  
Two Populations ◽  
Comet 67P

The plasma of comet 67P/Churyumov-Gerasimenko is analyzed based on the RPC-MIP mutual impedance probe data of the Rosetta mission. Numerical simulations of the RPC-MIP instrumental response considering two populations of electrons were fit on experimental responses acquired from January to September 2016 to extract the electron densities and temperatures. A time-tracking of the plasma parameters was performed, leading to the identification of a cold and a warm population of electrons during the period of interest. The respective densities and temperatures lie in the ranges [100; 1000] cm−3 and [0.05; 0.3] eV for the cold electrons and in the ranges [50; 500] cm−3 and [2; 10] eV for the warm electrons. Warm electrons most of the time made up between 10 and 30% of the whole population, while the temperature ratio between warm and cold electrons lay mostly between 30 and 70 during the period we studied. The fluctuation range of the plasma parameters, that is, the electron densities and temperatures, appears to have remained rather constant during the last nine months of the mission. We take the limitations of the instrument that are due to the experimental noise into account in our discussion of the results.

scholarly journals Plasma source and loss at comet 67P during the Rosetta mission

2018 ◽  
Vol 618 ◽  
pp. A77 ◽  
Author(s):  
K. L. Heritier ◽  
M. Galand ◽  
P. Henri ◽  
F. L. Johansson ◽  
A. Beth ◽  
...  
Keyword(s):  
Impact Ionization ◽  
Energetic Electron ◽  
Plasma Source ◽  
Number Density ◽  
Time Period ◽  
Rosetta Mission ◽  
Impedance Probe ◽  
Photo Ionization ◽  
Comet 67P

Context.The Rosetta spacecraft provided us with a unique opportunity to study comet 67P/Churyumov–Gerasimenko (67P) from a close perspective and over a 2-yr time period. Comet 67P is a weakly active comet. It was therefore unexpected to find an active and dynamic ionosphere where the cometary ions were largely dominant over the solar wind ions, even at large heliocentric distances.Aims.Our goal is to understand the different drivers of the cometary ionosphere and assess their variability over time and over the different conditions encountered by the comet during the Rosetta mission.Methods.We used a multi-instrument data-based ionospheric model to compute the total ion number density at the position of Rosetta. In-situ measurements from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the Rosetta Plasma Consortium (RPC)–Ion and Electron Sensor (IES), together with the RPC–LAngmuir Probe instrument (LAP) were used to compute the local ion total number density. The results are compared to the electron densities measured by RPC–Mutual Impedance Probe (MIP) and RPC–LAP.Results.We were able to disentangle the physical processes responsible for the formation of the cometary ions throughout the 2-yr escort phase and we evaluated their respective magnitudes. The main processes are photo-ionization and electron-impact ionization. The latter is a significant source of ionization at large heliocentric distance (>2 au) and was predominant during the last 4 months of the mission. The ionosphere was occasionally subject to singular solar events, temporarily increasing the ambient energetic electron population. Solar photons were the main ionizer near perihelion at 1.3 au from the Sun, during summer 2015.

Solar wind protons in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko

2021 ◽  
Author(s):  
Charlotte Goetz ◽  
Lucie Scharre ◽  
Cyril Simon-Wedlund ◽  
Hans Nilsson ◽  
Elias Odelstad ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Gas Production ◽  
Alpha Particles ◽  
Cometary Plasma ◽  
Plasma Environment ◽  
Rosetta Mission ◽  
Show Evidence ◽  
Solar Wind Origin ◽  
Comet 67P

<p>Against expectations, the Rosetta spacecraft was able to observe protons of solar wind origin in the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko. This study investigates these unexpected observations and gives a working hypothesis on what could be the underlying cause.</p> <p>The cometary plasma environment of a comet is shaped by two distinct plasma populations: the solar wind, consisting of protons, alpha particles, electrons and a magnetic field, and the cometary plasma, consisting of heavy ions such as water ions or carbon dioxide ions and electrons. <br />As the comet follows its orbit through the solar system, the amount of cometary ions that is produced varies significantly. This means that the plasma environment of the comet and the boundaries that form there are also dependent on the comet's heliocentric distance. </p> <p>For example, at sufficiently high gas production rates (close to the Sun) the protons from the solar wind are prevented from entering the inner coma entirely. The region where no protons (and other solar wind origin ions) can be detected is referred to as the solar wind ion cavity. <br />A second example is the diamagnetic cavity, a region very close to the nucleus of the comet, where the interplanetary magnetic field, which is carried by the solar wind electrons, cannot penetrate the densest part of the cometary plasma. </p> <p>The Rosetta mission clearly showed that the solar wind ion cavity is larger than the diamagnetic cavity at a comet such as 67P/Churyumov-Gerasimenko. However, this new study finds that in isolated incidences this order can be reversed and ions of solar wind origin (mostly protons, but also helium) can be detected inside the diamagnetic cavity. We present the observations pertaining to these events and list and discard possible mechanisms that could lead to such a configuration. Only one mechanism cannot be discarded: that of a solar wind configuration where the solar wind velocity is aligned with the magnetic field. We show evidence that fits this hypothesis as well as solar wind models in support. </p>

The cometary matter between volatiles and macromolecules

2021 ◽  
Author(s):  
Nora Hänni ◽  
Kathrin Altwegg ◽  
Daniel Müller ◽  
Boris Pestoni ◽  
Martin Rubin ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Mass Range ◽  
Degree Of Saturation ◽  
Full Data ◽  
Data Set ◽  
Insoluble Organic Matter ◽  
Rosetta Mission ◽  
Double Focusing ◽  
First Time ◽  
Comet 67P

<p>Small and volatile molecules are the most abundant constituents of a comet’s neutral coma. Thanks to ESA’s Rosetta mission, the neutral coma of comet 67P/Churyumov-Gerasimenko (67P hereafter) has been analyzed in great spatial and temporal detail, e.g., by Rubin et al. (2019) or by Läuter et al. (2020). However, the Double Focusing Mass Spectrometer (DFMS) – part of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA; Balsiger et al. 2007) – delivered data which contains information about the transition region between volatiles and macromolecular matter. Manual fitting of individual spectra allows to resolve pure hydrocarbon from heteroatom-bearing species also in the higher mass-range of the instrument, up to mass-to-charge (m/z) ratios of 140.</p> <p>While Altwegg et al. (2019) have reported tentative detections of some heavier species like benzoic acid or naphthalene, spectra of m/z>70 have not been investigated systematically. Here, we will present preliminary results from the first comprehensive analysis of a full data set (from m/z=12 to m/z=140) collected on August 3, 2015. On this day, the comet was close to its perihelion and the dust activity, as seen by the OSIRIS camera (Vincent et al. 2016), was high. Probably due to sublimation of molecules from ejected and heated-up dust grains, ROSINA/DFMS registered many signals above m/z=70. Due to the problem of isomerism and the lack of reference data, we chose to follow a statistical approach for our analysis. Larger species tend to expose a lower degree of saturation and the H/C ratio seems to approach that of highly unsaturated insoluble organic matter (IOM), cf., e.g., Sandford 2008. Although we cannot identify individual molecules in the complex gas mixture that makes up for the cometary coma, we are able to characterize for the first time the larger organic species that bridge the small volatiles and the macromolecular matter observed in 67P’s dust by the Rosetta secondary ion mass spectrometer COSIMA (Fray et al. 2016).</p> <p> </p> <p> </p> <p> </p> <p>Altwegg et al., 2019, Annu. Rev. Astron. Astrophys., 57, 113-55.</p> <p>Balsiger H. et al., 2007, Space Sci. Rev., 128, 745-801.</p> <p>Fray et al., 2016, Nature, 538, 72-74.</p> <p>Läuter et al., 2020, MNRAS, 498, 3, 3995-4004.</p> <p>Rubin et al., 2019, MNRAS, 489, 594-607.</p> <p>Sandford, 2008, Annu. Rev. Anal. Chem. 1, 549–78.</p> <p>Vincent et al., 2016, MNRAS, 462 (Suppl_1), 184-194.</p>

scholarly journals High Genetic Differentiation among European White Oak Species (Quercus spp.) at a Dehydrin Gene

2015 ◽  
Vol 43 (2) ◽  
pp. 582-588 ◽  
Author(s):  
Iacob CRĂCIUNESC ◽  
Barbara VORNAM ◽  
Ludger LEINEMANN ◽  
Reiner FINKELDEY ◽  
Neculae ȘOFLETEA ◽  
...  
Keyword(s):  
Genetic Differentiation ◽  
Related Species ◽  
Population Level ◽  
Quercus Petraea ◽  
White Oak ◽  
Closely Related Species ◽  
Significant Differentiation ◽  
Dehydrin Gene ◽  
First Time ◽  
Two Populations

Dehydryn genes are involved in plant response to environmental stress and may be useful to examine functional diversity in relation to adaptive variation. Recently, a dehydrin gene (DHN3) was isolated in Quercus petraea and showed little differentiation between populations of the same species in an altitudinal transect. In the present study, inter- and intraspecific differentiation patterns in closely related and interfertile oaks were investigated for the first time at the DHN3 locus. A four-oak-species stand (Quercus frainetto Ten., Q. petraea (Matt.) Liebl., Q. pubescens Willd., Q. robur L.) and two populations for each of five white oak species (Q. frainetto Ten., Q. petraea (Matt.) Liebl., Q. pubescens Willd., Q. robur L. and Q. pedunculiflora K. Koch) were analyzed. Three alleles shared by all five oak species were observed. However, only two alleles were present in each population, but with different frequencies according to the species. At population level, all interspecific pairs of populations showed significant differentiation, except for pure Q. robur and Q. pedunculiflora populations. In contrast, no significant differentiation (p > 0.05) was found among conspecific populations. The DHN3 locus proved to be very useful to differentiate Q. frainetto and Q. pubescens from Q. pedunculiflora (FST = 0.914 and 0.660, respectively) and Q. robur (FST = 0.858 and 0.633, respectively). As expected, the lowest level of differentiation was detected between the most closely related species, Q. robur and Q. pedunculiflora (FST = 0.020). Our results suggest that DHN3 can be an important genetic marker for differentiating among European white oak species.

scholarly journals First records of Brachythemis impartita in peninsular Italy (Odonata: Libellulidae)

2017 ◽  
pp. 133-136
Author(s):  
Emanuele Guido Condello ◽  
Edoardo Razzetti ◽  
Cristiano Liuzzi ◽  
Vittoria D’Agostino ◽  
Fabio Mastropasqua
Keyword(s):  
Habitat Preferences ◽  
Artificial Lake ◽  
Northward Expansion ◽  
First Time ◽  
Two Populations

Two populations of Brachythemis impartita (Karsch, 1890) are here reported in peninsular Italy. The species was found for the first time in 2015 in Calabria in the area of the Angitola artificial lake (Maierato and Monterosso Calabro municipalities) not far from the Tyrrhenian coast. In 2016 the species was also observed in southern Apulia, along the banks of two artificial lagoons in the municipality of Ugento. Information are provided that confirm the habitat preferences of the species and a northward expansion.

scholarly journals Cooling of Electrons in a Weakly Outgassing Comet

2020 ◽  
Author(s):  
Peter Stephenson ◽  
Marina Galand ◽  
Jan Deca ◽  
Pierre Henri ◽  
Gianluca Carnielli
Keyword(s):  
Solar Wind ◽  
Extreme Ultraviolet ◽  
Pure Water ◽  
Particle Model ◽  
Particle In Cell ◽  
Electron Sources ◽  
Cometary Plasma ◽  
Impedance Probe ◽  
Cold Electrons ◽  
The Impact

<p>The plasma instruments, Mutual Impedance Probe (MIP) and Langmuir Probe (LAP), part of the Rosetta Plasma Consortium (RPC), onboard the Rosetta mission to comet 67P revealed a population of cold electrons (<1eV) (Engelhardt et al., 2018; Wattieaux et al, 2020; Gilet et al., 2020). This population is primarily generated by cooling warm (~10eV) newly-born cometary electrons through collisions with the neutral coma. What is surprising is that the cold electrons were detected throughout the escort phase, even at very low outgassing rates (Q<1e26 s<sup>-1</sup>) at large heliocentric distances (>3 AU), when the coma was not thought to be dense enough to cool the electron population significantly.</p> <p> Using a collisional test particle model, we examine the behaviour of electrons in the coma of a weakly outgassing comet and the formation of a cold population through electron-neutral collisions. The model incorporates three electron sources: the solar wind, photo-electrons produced through ionisation of the cometary neutrals by extreme ultraviolet solar radiation, and secondary electrons produced through electron-impact ionisation.</p> <p>The model includes different electron-water collision processes, including elastic, excitation, and ionisation collisions.</p> <p> The electron trajectories are shaped by electric and magnetic fields, which are taken from a 3D collisionless fully-kinetic Particle-in-Cell (PIC) model of the solar wind and cometary plasma  (Deca 2017, 2019). We use a spherically symmetric coma of pure water, which gives a r<sup>-2</sup> profile in the neutral density. Throughout their lifetime, electrons undergo stochastic collisions with neutral molecules, which can degrade the electrons in energy or scatter them.</p> <p>We first validate our model with comparison to results from PIC simulations. We then demonstrate the trapping of electrons in the coma by an ambipolar electric field and the impact of this trapping on the production of cold electrons.</p>

scholarly journals A new Palaearctic species of the subgenus Lunatipula (Diptera, Tipulidae) from the West Caucasus with a survey of the caucasica species group

ZooKeys ◽  
2021 ◽  
Vol 1048 ◽  
pp. 145-175
Author(s):  
Vladimir I. Lantsov ◽  
Valentin E. Pilipenko
Keyword(s):  
New Species ◽  
Parallel Evolution ◽  
Distribution Patterns ◽  
Species Group ◽  
Palaearctic Species ◽  
The West ◽  
The Caucasus ◽  
Males And Females ◽  
First Time ◽  
Two Populations

The caucasica species group in the subgenus Lunatipula is redefined and now consists of five species native to the Caucasus. Tipula (L.) eleniyasp. nov. is described as new to science, and variations in the male terminalia in two populations are noted. Two subspecies (quadridentataquadridentata and quadridentatapaupera) are elevated to species rank. Detailed photo’s complement the descriptions of all five species (caucasica, eleniya, paupera, quadridentata, talyshensis), and data on ecology and distribution patterns are included as well as identification keys to males and females. Tipula caucasica is recorded from the West Caucasus and Tipula quadridentata is recorded from Dagestan (Russia) for the first time. Parallel evolution is traced in the male terminalia of the new species and in several non caucasica species group of Palaearctic Lunatipula.

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