Solar Wind-Comet Exosphere Interaction. 2. Could the Single-Fluid Gas-Dynamic Model be Applicable to the Rosetta Mission

2012 ◽  
Vol 42 (1) ◽  
pp. 71-90 ◽  
Author(s):  
M. Kartalev ◽  
P. Dobreva ◽  
V. Keremidarska ◽  
M. Dryer
Keyword(s):  
Solar Wind ◽  
Dynamic Model ◽  
Point Of View ◽  
Gas Dynamic ◽  
Rosetta Mission ◽  
Gasdynamic Model ◽  
Comet 67P

Solar Wind-Comet Exosphere Interaction. 2. Could the Single-Fluid Gas-Dynamic Model be Applicable to the Rosetta Mission The capabilities of a single fluid gasdynamic model of solar wind-comet exosphere interaction, presented in the accompanying (Keremidarska et al.) [23], are discussed from the point of view of its potential implementation in interpreting data, expected to be obtained by ROSETTA mission instruments in plasma environments of the comet 67P/Churyumov-Gerasimenko. As an exapmle, some model's predictions of the structure and parameters' distribution in the inner coma of P/Halley are presented and compared with Giotto measurements. Special attention is paid to a possible non-traditional interpretation of the magnetic cavity boundasry, registered by Giotto magnetometer. Possible model's applications are discussed for each of the main expected stages in the evolution of the comet 76P/CG environments during ROSETTA rendezvous with 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>

Three-component gas-dynamic model of the interaction of the solar wind with the interstellar medium

1983 ◽  
Vol 17 (5) ◽  
pp. 754-759 ◽  
Author(s):  
V. B. Baranov ◽  
M. K. Ermakov ◽  
M. G. Lebedev
Keyword(s):  
Solar Wind ◽  
Interstellar Medium ◽  
Dynamic Model ◽  
Gas Dynamic

Comparison of gas dynamic model with steady solar wind flow around Venus

1982 ◽  
Vol 87 (A12) ◽  
pp. 10363 ◽  
Author(s):  
J. D. Mihalov ◽  
J. R. Spreiter ◽  
S. S. Stahara
Keyword(s):  
Solar Wind ◽  
Dynamic Model ◽  
Wind Flow ◽  
Gas Dynamic ◽  
Solar Wind Flow

Energy and momentum flux around comet 67P throughout the Rosetta mission

2020 ◽  
Author(s):  
Hans Nilsson ◽  
Hayley Williamson ◽  
Gabriella Stenberg Wieser ◽  
Ingo Richter ◽  
Charlotte Götz
Keyword(s):  
Solar Wind ◽  
Energy Flux ◽  
Momentum Flux ◽  
Population Based ◽  
Ion Fluxes ◽  
Relative Contribution ◽  
Rosetta Mission ◽  
Order Of Magnitude ◽  
Energy And Momentum ◽  
Comet 67P

<p>We calculate the momentum and energy flux of ions measured by the Ion Composition Analyzer (ICA) on the Rosetta mission at comet 67P/Churyumov-Gerasimenko. We find that the total ion energy and momentum flux stay roughly constant over the mission, but the relative contribution of solar wind ions and cometary ions changes drastically depending on the spacecraft position in the ionosphere and distance from the comet to the sun. We also see that the magnetic pressure, calculated from the magnetic field measured by the Rosetta magnetometer, is on the order of the total ion momentum flux and roughly corresponds with the cometary ion momentum flux. Near both the beginning and end of the mission, solar wind momentum and energy flux are roughly two orders of magnitude larger than the corresponding heavy cometary ion fluxes. When the spacecraft enters the solar wind ion cavity near the comet’s periapsis, the solar wind energy and momentum flux drop drastically, mainly due to reduced density. Meanwhile, the cometary energy flux increases to be roughly equal to the solar wind flux earlier in the mission and the cometary momentum flux as measured by ICA becomes roughly an order of magnitude higher than previous and later solar wind fluxes. We also examine the changes in flux on two excursions, one on the dayside and one on the nightside of the comet, and see that during the nightside excursion, the cometary ion fluxes drop off roughly with the square of the distance from the comet. During the dayside excursion the flux was approximately constant, indicating that the excursion distance was small compared to the region where the observed ions were produced. ICA does not measure the lowest energy ions, so we also discuss the energy and momentum of the full ion population based on density estimates from the LAP and MIP instruments.</p>

scholarly journals Size of a plasma cloud matters

2018 ◽  
Vol 616 ◽  
pp. A50 ◽  
Author(s):  
H. Nilsson ◽  
H. Gunell ◽  
T. Karlsson ◽  
N. Brenning ◽  
P. Henri ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Plasma Density ◽  
Cloud Model ◽  
Parameter Range ◽  
Pickup Ions ◽  
Rosetta Mission ◽  
Comet 67P ◽  
The Magnetic Field

Context. The cometary ionosphere is immersed in fast flowing solar wind. A polarisation electric field may arise for comets much smaller than the gyroradius of pickup ions because ions and electrons respond differently to the solar wind electric field.Aims. A situation similar to that found at a low activity comet has been modelled for barium releases in the Earth’s ionosphere. We aim to use such a model and apply it to the case of comet 67P Churyumov-Gerasimenko, the target of the Rosetta mission. We aim to explain the significant tailward acceleration of cometary ions through the modelled electric field.Methods. We obtained analytical solutions for the polarisation electric field of the comet ionosphere using a simplified geometry. This geometry is applicable to the comet in the inner part of the coma as the plasma density integrated along the magnetic field line remains rather constant. We studied the range of parameters for which a significant tailward electric field is obtained and compare this with the parameter range observed.Results. Observations of the local plasma density and magnetic field strength show that the parameter range of the observations agree very well with a significant polarisation electric field shielding the inner part of the coma from the solar wind electric field.Conclusions. The same process gives rise to a tailward directed electric field with a strength of the order of 10% of the solar wind electric field. Using a simple cloud model we have shown that the polarisation electric field, which arises because of the small size of the comet ionosphere as compared to the pick up ion gyroradius, can explain the observed significant tailward acceleration of cometary ions and is consistent with the observed lack of influence of the solar wind electric field in the inner coma.

scholarly journals Interaction of the solar wind with comets: a Rosetta perspective

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160256 ◽  
Author(s):  
Karl-Heinz Glassmeier
Keyword(s):  
Solar Wind ◽  
Low Frequency ◽  
Passage Time ◽  
Interaction Region ◽  
Ulf Waves ◽  
Activity Levels ◽  
Rosetta Mission ◽  
Comet 67P ◽  
Region Plasma ◽  
Low Activity

The Rosetta mission provides an unprecedented possibility to study the interaction of comets with the solar wind. As the spacecraft accompanies comet 67P/Churyumov–Gerasimenko from its very low-activity stage through its perihelion phase, the physics of mass loading is witnessed for various activity levels of the nucleus. While observations at other comets provided snapshots of the interaction region and its various plasma boundaries, Rosetta observations allow a detailed study of the temporal evolution of the innermost cometary magnetosphere. Owing to the short passage time of the solar wind through the interaction region, plasma instabilities such as ring--beam and non-gyrotropic instabilities are of less importance during the early life of the magnetosphere. Large-amplitude ultra-low-frequency (ULF) waves, the ‘singing’ of the comet, is probably due to a modified ion Weibel instability. This instability drives a cross-field current of implanted cometary ions unstable. The initial pick-up of these ions causes a major deflection of the solar wind protons. Proton deflection, cross-field current and the instability induce a threefold structure of the innermost interaction region with the characteristic Mach cone and Whistler wings as stationary interaction signatures as well as the ULF waves representing the dynamic aspect of the interaction. This article is part of the themed issue ‘Cometary science after Rosetta’.

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>

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.

Sign in / Sign up

Export Citation Format

Share Document