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 Solar wind charge exchange in cometary atmospheres

2019 ◽  
Vol 630 ◽  
pp. A35 ◽  
Author(s):  
Cyril Simon Wedlund ◽  
Dennis Bodewits ◽  
Markku Alho ◽  
Ronnie Hoekstra ◽  
Etienne Behar ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Cross Sections ◽  
Local Heating ◽  
Single Electron ◽  
Analytical Models ◽  
Neutral Atmosphere ◽  
Ionization Cross ◽  
Ionization Cross Sections ◽  
K 12

Context. Solar wind charge-changing reactions are of paramount importance to the physico-chemistry of the atmosphere of a comet, mass-loading the solar wind through an effective conversion of fast light solar wind ions into slow heavy cometary ions. Aims. To understand these processes and place them in the context of a solar wind plasma interacting with a neutral atmosphere, numerical or analytical models are necessary. Inputs of these models, such as collision cross sections and chemistry, are crucial. Methods. Book-keeping and fitting of experimentally measured charge-changing and ionization cross sections of hydrogen and helium particles in a water gas are discussed, with emphasis on the low-energy/low-velocity range that is characteristic of solar wind bulk speeds (<20 keV u−1/2000 km s−1). Results. We provide polynomial fits for cross sections of charge-changing and ionization reactions, and list the experimental needs for future studies. To take into account the energy distribution of the solar wind, we calculated Maxwellian-averaged cross sections and fitted them with bivariate polynomials for solar wind temperatures ranging from 105 to 106 K (12–130 eV). Conclusions. Single- and double-electron captures by He2+ dominate at typical solar wind speeds. Correspondingly, single-electron capture by H+ and single-electron loss by H− dominate at these speeds, resulting in the production of energetic neutral atoms (ENAs). Ionization cross sections all peak at energies above 20 keV and are expected to play a moderate role in the total ion production. However, the effect of solar wind Maxwellian temperatures is found to be maximum for cross sections peaking at higher energies, suggesting that local heating at shock structures in cometary and planetary environments may favor processes previously thought to be negligible. This study is the first part in a series of three on charge exchange and ionization processes at comets, with a specific application to comet 67P/Churyumov-Gerasimenko and the Rosetta mission.

scholarly journals Asymmetric multifractal model for solar wind intermittent turbulence

2008 ◽  
Vol 15 (4) ◽  
pp. 615-620 ◽  
Author(s):  
A. Szczepaniak ◽  
W. M. Macek
Keyword(s):  
Solar Wind ◽  
Solar Maximum ◽  
Solar Wind Plasma ◽  
Intermittent Turbulence ◽  
Proposed Model ◽  
Scaling Parameters ◽  
Generalized Dimensions ◽  
Multifractal Nature ◽  
Turbulent Cascade

Abstract. We consider nonuniform energy transfer rate for solar wind turbulence depending on the solar cycle activity. To achieve this purpose we determine the generalized dimensions and singularity spectra for the experimental data of the solar wind measured in situ by Advanced Composition Explorer spacecraft during solar maximum (2001) and minimum (2006) at 1 AU. By determining the asymmetric singularity spectra we confirm the multifractal nature of different states of the solar wind. Moreover, for explanation of this asymmetry we propose a generalization of the usual so-called p-model, which involves eddies of different sizes for the turbulent cascade. Naturally, this generalization takes into account two different scaling parameters for sizes of eddies and one probability measure parameter, describing how the energy is transferred to smaller eddies. We show that the proposed model properly describes multifractality of the solar wind plasma.

Statistical relations between in-situ measured Bz component and thermospheric density variations

2021 ◽  
Author(s):  
Sofia Kroisz ◽  
Lukas Drescher ◽  
Manuela Temmer ◽  
Sandro Krauss ◽  
Barbara Süsser-Rechberger ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Satellite Orbit ◽  
Solar Wind Plasma ◽  
Statistical Investigation ◽  
Neutral Density ◽  
Special Focus ◽  
Short Term

&lt;p&gt;Through advanced statistical investigation and evaluation of solar wind plasma and magnetic field data, we investigate the statistical relation between the magnetic field B&lt;sub&gt;z&lt;/sub&gt; component, measured at L1, and Earth&amp;#8217;s thermospheric neutral density. We will present preliminary results of the time series analyzes using in-situ plasma and magnetic field measurements from different spacecraft in near Earth space (e.g., ACE, Wind, DSCOVR) and relate those to derived thermospheric densities from various satellites (e.g., GRACE, CHAMP). The long and short term variations and dependencies in the solar wind data are related to variations in the neutral density of the thermosphere and geomagnetic indices. Special focus is put on the specific signatures that stem from coronal mass ejections and stream or corotating interaction regions.&amp;#160; The results are used to develop a novel short-term forecasting model called SODA (Satellite Orbit DecAy). This is a joint study between TU Graz and University of Graz funded by the FFG Austria (project &amp;#8220;SWEETS&amp;#8221;).&lt;/p&gt;

Source-dependent properties of the background slow solar wind encountered by Parker Solar Probe

2021 ◽  
Author(s):  
Léa Griton ◽  
Sarah Watson ◽  
Nicolas Poirier ◽  
Alexis Rouillard ◽  
Karine Issautier ◽  
...  
Keyword(s):  
Solar Wind ◽  
Extreme Ultraviolet ◽  
Plasma Heating ◽  
Coronal Holes ◽  
Slow Solar Wind ◽  
Source Surface ◽  
Field Source ◽  
Flux Tubes ◽  
Field Lines

&lt;p&gt;Different states of the slow solar wind are identified from in-situ measurements by Parker Solar Probe (PSP) inside 50 solar radii from the Sun (Encounters 1, 2, 4, 5 and 6). At such distances the wind measured at PSP has not yet undergone significant transformation related to the expansion and propagation of the wind. We focus in this study on the properties of the quiet solar wind with no magnetic switchbacks. The Slow Solar Wind (SSW) states differ by their density, flux, plasma beta and magnetic pressure. PSP's magnetic connectivity established with Potential Field Source Surface (PFSS) reconstructions, tested against extreme ultraviolet (EUV) and white-light imaging, reveals the different states under study generally correspond to transitions from streamers to equatorial coronal holes. Solar wind simulations run along these differing flux tubes reproduce the slower and denser wind measured in the streamer and the more tenuous wind measured in the coronal hole. Plasma heating is more intense at the base of the streamer field lines rooted near the boundary of the equatorial hole than those rooted closer to the center of the hole. This results in a higher wind flux driven inside the streamer than deeper inside the equatorial hole.&amp;#160;&lt;/p&gt;

The low-energy ion event on 2020 June 19 measured by Solar Orbiter

2021 ◽  
Author(s):  
Angels Aran ◽  
Daniel Pacheco ◽  
Monica Laurenza ◽  
Nicolas Wijsen ◽  
Evangelia Samara ◽  
...  
Keyword(s):  
Solar Wind ◽  
Energy Range ◽  
Extreme Ultraviolet ◽  
Solar Rotation ◽  
Complex Structure ◽  
Forbush Decrease ◽  
Solar Wind Plasma ◽  
Low Energy ◽  
The European Union ◽  
Horizon 2020

&lt;p&gt;Shortly after reaching the first perihelion, the Energetic Particle Detector (EPD) onboard Solar Orbiter measured a low-energy (&lt;1 MeV/nuc) ion event whose duration varied with the energy of the particles. The increase above pre-event intensity levels was detected early on June 19 for ions in the energy range from ~50 keV to ~1 MeV and lasted up to ~12:00 UT on June 20. In the energy range from ~10 keV to &lt; 40 keV, the ion event spanned from June 18 to 21. This latter low-energy ion intensity enhancement coincided with a two-step Forbush decrease (FD) as displayed in the EPD &gt; 17 MeV/nuc ion measurements. On the other hand, no electron increases were detected. As seen from 1 au, there is no clear evidence of solar activity from the visible disk that could be associated with the origin of this ion event. We hypothesize about the origin of this event as due to either a possible solar eruption occurring behind the visible part of the Sun or to an interplanetary spatial structure. We use interplanetary magnetic field data from the Solar Orbiter Magnetometer (MAG), solar wind electron density derived from measurements of the Solar Orbiter Radio and Plasma Waves (RPW) instrument to specify the in-situ solar wind conditions where the ion event was observed. In addition, we use solar wind plasma measurements from the Solar Orbiter Solar Wind Analyser (SWA) suite gathered during the following solar rotation, for comparison purposes. In order to seek for possible associated solar sources, we use images from the Extreme Ultraviolet Imager (EUI) instrument onboard Solar Orbiter. Together with the lack of electron observations and Type III radio bursts, the simultaneous response of the ion intensity-time profiles at various energies indicates an interplanetary source for the particles. The two-step FD shape observed during this event suggests that the first step early on June 18 was due to a transient structure, whereas the second step on June 19, together with the ~50 &amp;#8211;1000 keV/nuc ion enhancement, was due to a solar wind stream interaction region. The observation of a similar FD in the next solar rotation favours this interpretation, although a more complex structure cannot be discarded due to the lack of concurrent solar wind temperature and velocity observations.&lt;/p&gt;&lt;p&gt;Different parts of this research have received funding from the European Union&amp;#8217;s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) and grant agreement No 01004159 (SERPENTINE).&lt;/p&gt;

Solar Flux and Molecular Absorption

1999 ◽  
Author(s):  
Yuk L. Yung ◽  
William B. DeMore
Keyword(s):  
Energy Source ◽  
Solar Wind ◽  
Cross Sections ◽  
Electronic Excitation ◽  
Extreme Ultraviolet ◽  
Resonance Scattering ◽  
Planetary Atmospheres ◽  
The Sun ◽  
Atoms And Molecules ◽  
Planetary Rotation

In this book we are concerned primarily with disequilibrium chemistry, of which the sun is the principal driving force. The sun is not, however, the only source of disequilibrium chemistry in the solar system. We briefly discuss other minor energy sources such as the solar wind, starlight, precipitation of energetic particles, and lightning. Note that these sources are not independent. For example, the ultimate energy source of the magnetospheric particles is the solar wind and planetary rotation; the energy source for lightning is atmospheric winds powered by solar irradiance. Only starlight and galactic cosmic rays are completely independent of the sun. While the sun is the energy source, the atoms and molecules in the planetary atmospheres are the receivers of this energy. For atoms the interaction with radiation results in three possibilities: (a) resonance scattering, (b) absorption followed by fluorescence, and (c) ionization. lonization usually requires photons in the extreme ultraviolet. The interaction between molecules and the radiation field is more complicated. In addition to the above (including Rayleigh and Raman scattering) we can have (d) dissociation, (e) intramolecular conversion, and (f) vibrational and rotational excitation. Note that processes (a)-(e) involve electronic excitation; process (f) usually involves infrared radiation that is not energetic enough to cause electronic excitation. The last process is important for the thermal budget of the atmosphere, a subject that is not pursued in this book. Scattering and fluorescence are a source of airglow and aurorae and provide valuable tools for monitoring detailed atomic and molecular processes in the atmosphere. Processes (c) and (d) are most important for determining the chemical composition of planetary atmospheres. Interesting chemical reactions are initiated when the absorption of solar energy leads to ionization or the breaking of chemical bonds. In this chapter we provide a survey of the absorption cross sections of selected atoms and molecules. The selection is based on the likely importance of these species in planetary atmospheres.

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

scholarly journals Halo-coronal mass ejections near the 23rd solar minimum: lift-off, inner heliosphere, and in situ (1 AU) signatures

2002 ◽  
Vol 20 (7) ◽  
pp. 891-916 ◽  
Author(s):  
D. B. Berdichevsky ◽  
C. J. Farrugia ◽  
B. J. Thompson ◽  
R. P. Lepping ◽  
D. V. Reames ◽  
...  
Keyword(s):  
Solar Wind ◽  
Transit Time ◽  
Coronal Mass Ejections ◽  
Energetic Particle ◽  
Extreme Ultraviolet ◽  
Nonlinear Phenomena ◽  
Lift Off ◽  
Earth Connection ◽  
Local Speed

Abstract. The extreme ultraviolet (EUV) signatures of a solar lift-off, decametric and kilometric radio burst emissions and energetic particle (EP) inner heliospheric signatures of an interplanetary shock, and in situ identification of its driver through solar wind observations are discussed for 12 isolated halo coronal mass ejections (H-CMEs) occurring between December 1996 and 1997. For the aforementioned twelve and the one event added in the discussion, it is found that ten passed several necessary conditions for being a "Sun-Earth connection". It is found that low corona EUV and Ha chromospheric signatures indicate filament eruption as the cause of H-CME. These signatures indicate that the 12 events can be divided into two major subsets, 7 related to active regions (ARs) and 5 unrelated or related to decayed AR. In the case of events related to AR, there is indication of a faster lift-off, while a more gradual lift-off appears to characterize the second set. Inner heliospheric signatures – the presence of long lasting enhanced energetic particle flux and/or kilometric type II radio bursts – of a driven shock were identified in half of the 12 events. The in situ (1 AU) analyses using five different solar wind ejecta signatures and comparisons with the bidirectional flow of suprathermal particles and Forbush decreases result in indications of a strong solar wind ejecta signatures for 11 out of 12 cases. From the discussion of these results, combined with work by other authors for overlapping events, we conclude that good Sun-Earth connection candidates originate most likely from solar filament eruptions with at least one of its extremities located closer to the central meridian than ~ 30° E or ~ 35° W with a larger extension in latitudinal location possible. In seven of the twelve cases it appears that the encountered ejecta was driving a shock at 1 AU. Support for this interpretation is found on the approximately equal velocity of the shock and the ejecta leading-edge. These shocks were weak to moderate in strength, and a comparison of their transit time with their local speed indicated a deceleration. In contradistinction with this result on shocks, the transit time versus the local speed of the ejecta appeared either to indicate that the ejecta as a whole traveled at constant speed or underwent a small amount of acceleration. This is a result that stands for cases with and without fast stream observations at their rear end. Seven out of twelve ejecta candidate intervals were themselves interplanetary magnetic cloud (IMC) or contained a previously identified IMC. As a by-product of this study, we noticed two good ejecta candidates at 1 AU for which observation of a H-CME or CME appears to be missing.Key words. Radio science (remote sensing); Solar physics, astrophysics and astronomy (flares and mass ejections); Space plasma physics (nonlinear phenomena)

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