scholarly journals Charge exchange in cometary coma: Discovery of H− ions in the solar wind close to comet 67P/Churyumov-Gerasimenko

2015 ◽  
Vol 42 (13) ◽  
pp. 5125-5131 ◽  
Author(s):  
J. L. Burch ◽  
T. E. Cravens ◽  
K. Llera ◽  
R. Goldstein ◽  
P. Mokashi ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Cometary Coma ◽  
Comet 67P

scholarly journals Solar wind charge exchange in cometary atmospheres

2019 ◽  
Vol 630 ◽  
pp. A37 ◽  
Author(s):  
Cyril Simon Wedlund ◽  
Etienne Behar ◽  
Hans Nilsson ◽  
Markku Alho ◽  
Esa Kallio ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Cross Sections ◽  
Extreme Ultraviolet ◽  
Solar Wind Plasma ◽  
Analytical Models ◽  
Sharp Drop ◽  
Solar Wind Charge Exchange ◽  
Comet 67P

Context. Solar wind charge-changing reactions are of paramount importance to the physico-chemistry of the atmosphere of a comet. The ESA/Rosetta mission to comet 67P/Churyumov-Gerasimenko (67P) provides a unique opportunity to study charge-changing processes in situ. Aims. To understand the role of these reactions in the evolution of the solar wind plasma and interpret the complex in situ measurements made by Rosetta, numerical or analytical models are necessary. Methods. We used an extended analytical formalism describing solar wind charge-changing processes at comets along solar wind streamlines. The model is driven by solar wind ion measurements from the Rosetta Plasma Consortium-Ion Composition Analyser (RPC-ICA) and neutral density observations from the Rosetta Spectrometer for Ion and Neutral Analysis-Comet Pressure Sensor (ROSINA-COPS), as well as by charge-changing cross sections of hydrogen and helium particles in a water gas. Results. A mission-wide overview of charge-changing efficiencies at comet 67P is presented. Electron capture cross sections dominate and favor the production of He and H energetic neutral atoms (ENAs), with fluxes expected to rival those of H+ and He2+ ions. Conclusions. Neutral outgassing rates are retrieved from local RPC-ICA flux measurements and match ROSINA estimates very well throughout the mission. From the model, we find that solar wind charge exchange is unable to fully explain the magnitude of the sharp drop in solar wind ion fluxes observed by Rosetta for heliocentric distances below 2.5 AU. This is likely because the model does not take the relative ion dynamics into account and to a lesser extent because it ignores the formation of bow-shock-like structures upstream of the nucleus. This work also shows that the ionization by solar extreme-ultraviolet radiation and energetic electrons dominates the source of cometary ions, although solar wind contributions may be significant during isolated events.

scholarly journals Solar wind charge exchange in cometary atmospheres

2019 ◽  
Vol 630 ◽  
pp. A36 ◽  
Author(s):  
Cyril Simon Wedlund ◽  
Etienne Behar ◽  
Esa Kallio ◽  
Hans Nilsson ◽  
Markku Alho ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Solar Wind Speed ◽  
Analytical Models ◽  
Ion Temperature ◽  
Mass Load ◽  
Rosetta Mission ◽  
Solar Wind Charge Exchange ◽  
Comet 67P

Context. Solar wind charge-changing reactions are of paramount importance to the physico-chemistry of the atmosphere of a comet because they mass-load the solar wind through an effective conversion of fast, light solar wind ions into slow, heavy cometary ions. The ESA/Rosetta mission to comet 67P/Churyumov-Gerasimenko (67P) provided a unique opportunity to study charge-changing processes in situ. Aims. To understand the role of charge-changing reactions in the evolution of the solar wind plasma and to interpret the complex in situ measurements made by Rosetta, numerical or analytical models are necessary. Methods. An extended analytical formalism describing solar wind charge-changing processes at comets along solar wind streamlines is presented. It is based on a thorough book-keeping of available charge-changing cross sections of hydrogen and helium particles in a water gas. Results. After presenting a general 1D solution of charge exchange at comets, we study the theoretical dependence of charge-state distributions of (He2+, He+, He0) and (H+, H0, H−) on solar wind parameters at comet 67P. We show that double charge exchange for the He2+−H2O system plays an important role below a solar wind bulk speed of 200 km s−1, resulting in the production of He energetic neutral atoms, whereas stripping reactions can in general be neglected. Retrievals of outgassing rates and solar wind upstream fluxes from local Rosetta measurements deep in the coma are discussed. Solar wind ion temperature effects at 400 km s−1 solar wind speed are well contained during the Rosetta mission. Conclusions. As the comet approaches perihelion, the model predicts a sharp decrease of solar wind ion fluxes by almost one order of magnitude at the location of Rosetta, forming in effect a solar wind ion cavity. This study is the second part of a series of three on solar wind charge-exchange and ionization processes at comets, with a specific application to comet 67P and the Rosetta mission.

scholarly journals The charge-exchange induced coupling between plasma-gas counterflows in the heliosheath

2003 ◽  
Vol 21 (6) ◽  
pp. 1289-1294 ◽  
Author(s):  
H. J. Fahr
Keyword(s):  
Solar Wind ◽  
Critical Point ◽  
Charge Exchange ◽  
Plasma Temperature ◽  
Exchange Term ◽  
Momentum Exchange ◽  
Plasma Bubble ◽  
Friction Forces ◽  
Sonic Point ◽  
Interplanetary Physics

Abstract. Many hydrodynamic models have been presented which give similar views of the interaction of the solar wind plasma bubble with the counterstreaming partially ionized interstellar medium. In the more recent of these models it is taken into account that the solar and interstellar hydrodynamic flows of neutral atoms and protons are coupled by mass-, momentum-, and energy-exchange terms due to charge exchange processes. We shall reinvestigate the theoretical basis of this coupling here by use of a simplified description of the heliospheric interface and describe the main physics of the H-atom penetration through the more or less standing well-known plasma wall ahead of the heliopause. Thereby we can show that the type of charge exchange coupling terms used in up-to-now hydrodynamic treatments unavoidably leads to an O-type critical point at the sonic point of the H-atom flow, thus not allowing for a continuation of the integration of the hydrodynamic set of differential equations. The remedy for this problem is given by a more accurate formulation of the momentum exchange term for quasi-and sub-sonic H-atom flows. With a refined momentum exchange term derived from basic kinetic Boltzmann principles, we instead arrive at a characteristic equation with an X-type critical point, allowing for a continuous solution from supersonic to subsonic flow conditions. This necessitates that the often treated problem of the propagation of inter-stellar H-atoms through the heliosheath has to be solved using these newly derived, differently effective plasma – gas friction forces. Substantially different results are to be expected from this context for the filtration efficiency of the heliospheric interface.Key words. Interplanetary physics (heliopause and solar wind termination; interstellar gas) – Ionosphere (plasma temperature and density)

scholarly journals Plasma properties of suprathermal electrons near comet 67P/Churyumov-Gerasimenko with Rosetta

2019 ◽  
Vol 630 ◽  
pp. A42 ◽  
Author(s):  
M. Myllys ◽  
P. Henri ◽  
M. Galand ◽  
K. L. Heritier ◽  
N. Gilet ◽  
...  
Keyword(s):  
Solar Wind ◽  
Heliocentric Distance ◽  
Radial Distance ◽  
Hot Electron ◽  
Plasma Properties ◽  
Measured Velocity ◽  
Electron Population ◽  
Suprathermal Electrons ◽  
Comet 67P ◽  
Cometary Activity

Context. The Rosetta spacecraft escorted comet 67P/Churyumov-Gerasimenko from 2014 to September 2016. The mission provided in situ observations of the cometary plasma during different phases of the cometary activity, which enabled us to better understand its evolution as a function of heliocentric distance. Aims. In this study, different electron populations, called warm and hot, observed by the Ion and Electron Sensor (IES) of the Rosetta Plasma Consortium (RPC) are investigated near the comet during the escorting phase of the Rosetta mission. Methods. The estimates for the suprathermal electron densities and temperatures were extracted using IES electron data by fitting a double-kappa function to the measured velocity distributions. The fitting results were validated using observations from other RPC instruments. We give upgraded estimates for the warm and hot population densities compared to values previously shown in literature. Results. The fitted density and temperature estimates for both electron populations seen by IES are expressed as a function of heliocentric distance to study their evolution with the cometary activity. In addition, we studied the dependence between the electron properties and cometocentric distance. Conclusions. We observed that when the neutral outgassing rate of the nucleus is high (i.e., near perihelion) the suprathermal electrons are well characterized by a double-kappa distribution. In addition, warm and hot populations show a significant dependence with the heliocentric distance. The populations become clearly denser near perihelion while their temperatures are observed to remain almost constant. Moreover, the warm electron population density is shown to be strongly dependent on the radial distance from the comet. Finally, based on our results we reject the hypothesis that hot electron population seen by IES consists of solely suprathermal (halo) solar wind electrons, while we suggest that the hot electron population mainly consists of solar wind thermal electrons that have undergone acceleration near the comet.

Ion energy and momentum flux near the cometopause of Comet 67P/Churyumov-Gerasimenko

2021 ◽  
Author(s):  
Hayley Williamson ◽  
Hans Nilsson ◽  
Anja Moslinger ◽  
Sofia Bergman ◽  
Gabriella Stenberg-Wieser
Keyword(s):  
Solar Wind ◽  
Complex Dynamics ◽  
Distribution Functions ◽  
Transitional Period ◽  
Ion Energy ◽  
Rosetta Mission ◽  
Before And After ◽  
Composition Analyzer ◽  
Energy And Momentum ◽  
Comet 67P

<p>Defined as the region where the plasma interaction region of a comet goes from being solar wind-dominated to cometary ion-dominated, the cometopause is a region of comingling plasmas and complex dynamics. The Rosetta mission orbited comet 67P/Churyumov-Gerasimenko for roughly two years. During this time, the cometopause was observed by the Ion Composition Analyzer (ICA), part of the Rosetta Plasma Consortium (RPC), before and after the spacecraft was in the solar wind ion cavity, defined as the region where no solar wind ions were measured. Data from ICA shows that solar wind and cometary ions have similar momentum and energy flux moments during this transitional period, indicating mass loading and deflection of the solar wind. We examine higher order moments and distribution functions for the solar wind and cometary species between December 2015 and March 2016. The behavior of the solar wind protons indicates that in many cases these protons are deflected in a sunward direction, while the cometary ions continue to move predominately antisunward. By studying the distribution functions of the protons during these time periods, it is possible to see a non-Maxwellian energy distribution. This can inform on the nature of the cometopause boundary and the energy transfer mechanisms at play in this region.</p>

scholarly journals Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

2018 ◽  
Vol 214 (4) ◽  
Author(s):  
David G. Sibeck ◽  
R. Allen ◽  
H. Aryan ◽  
D. Bodewits ◽  
P. Brandt ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Plasma Density ◽  
X Rays ◽  
Solar Wind Charge Exchange

OBSERVATION OF SOLAR WIND CHARGE EXCHANGE EMISSION FROM EXOSPHERIC MATERIAL IN AND OUTSIDE EARTH'S MAGNETOSHEATH 2008 SEPTEMBER 25

2009 ◽  
Vol 691 (1) ◽  
pp. 372-381 ◽  
Author(s):  
S. L. Snowden ◽  
M. R. Collier ◽  
T. Cravens ◽  
K. D. Kuntz ◽  
S. T. Lepri ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Solar Wind Charge Exchange

OBSERVATION AND MODELING OF GEOCORONAL CHARGE EXCHANGE X-RAY EMISSION DURING SOLAR WIND GUSTS

2014 ◽  
Vol 796 (1) ◽  
pp. 28 ◽  
Author(s):  
B. J. Wargelin ◽  
M. Kornbleuth ◽  
P. L. Martin ◽  
M. Juda
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
X Ray ◽  
Wind Gusts
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