Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov–Gerasimenko during the intermediate activity period

Aims. Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods. We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results. On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions. Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov–Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

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The root of a comet tail: Rosetta ion observations at comet 67P/Churyumov–Gerasimenko

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832842 ◽

2018 ◽

Vol 616 ◽

pp. A21 ◽

Cited By ~ 10

Author(s):

E. Behar ◽

H. Nilsson ◽

P. Henri ◽

L. Berčič ◽

G. Nicolaou ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Electric Field ◽

Outer Region ◽

Field Measurements ◽

Night Side ◽

Combined Action ◽

Single Night ◽

Inner Region ◽

Comet 67P

Context. The first 1000 km of the ion tail of comet 67P/Churyumov–Gerasimenko were explored by the European Rosetta spacecraft, 2.7 au away from the Sun. Aims. We characterised the dynamics of both the solar wind and the cometary ions on the night-side of the comet’s atmosphere. Methods. We analysed in situ ion and magnetic field measurements and compared the data to a semi-analytical model. Results. The cometary ions are observed flowing close to radially away from the nucleus during the entire excursion. The solar wind is deflected by its interaction with the new-born cometary ions. Two concentric regions appear, an inner region dominated by the expanding cometary ions and an outer region dominated by the solar wind particles. Conclusions. The single night-side excursion operated by Rosetta revealed that the near radial flow of the cometary ions can be explained by the combined action of three different electric field components, resulting from the ion motion, the electron pressure gradients, and the magnetic field draping. The observed solar wind deflection is governed mostly by the motional electric field −uion × B.

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Plasma diagnostics by laser spectroscopic electric field measurement

Pure and Applied Chemistry ◽

10.1351/pac200577020345 ◽

2005 ◽

Vol 77 (2) ◽

pp. 345-358 ◽

Cited By ~ 12

Author(s):

U. Czarnetzki ◽

D. Luggenhölscher ◽

V. A. Kadetov ◽

H. F. Döbele

Keyword(s):

Electric Field ◽

Density Distribution ◽

Field Measurements ◽

Distribution Functions ◽

Plasma Parameters ◽

Ion Density ◽

Versatile Tool ◽

Low Temperature Plasmas ◽

Energy Distribution Functions ◽

Laser Spectroscopic

Laser spectroscopic electric field measurements have the potential to become a versatile tool for the diagnostics of low-temperature plasmas. From the spatially and temporally resolved field distribution in the sheath close to electrodes or surfaces in general, a broad range of important plasma parameters can be inferred directly: electron temperature; ion density distribution; displacement-, ion-, electron-diffusion current density; and the sheath potential. Indirectly, the electron and ion energy distribution functions and information on the ion dynamics in the sheath can also be obtained. Finally, measurements in the quasi-neutral bulk can also reveal even the plasma density distribution with high spatial and temporal resolution. The basic concepts for analysis of the field data are introduced and demonstrated by examples in hydrogen discharges.

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Whistler waves observed by Solar Orbiter during its first orbit

10.5194/egusphere-egu21-15195 ◽

2021 ◽

Author(s):

Matthieu Kretschmar ◽

Thomas Chust ◽

Daniel Graham ◽

Volodya Krasnosekskikh ◽

Lucas Colomban ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Electromagnetic Waves ◽

Heliocentric Distance ◽

Plasma Waves ◽

Distribution Functions ◽

The Sun ◽

Whistler Waves ◽

Velocity Distribution Functions ◽

The Waves

<p>Plasma waves can play an important role in the evolution of the solar wind and the&#160;particle&#160;velocity distribution functions in particular. We analyzed the electromagnetic waves&#160;observed above a few Hz by the Radio Plasma Waves (RPW) instrument suite onboard Solar Orbiter, during its first orbit,&#160;which covered a distance&#160;from the Sun between 1 AU and 0.5&#160;AU. &#160;We identified the majority of the detected waves as whistler waves with frequency around &#160;0.1 f_ce and right handed&#160;circular&#160;polarisation. We found these waves to be mostly&#160;aligned or anti aligned with the&#160;ambient&#160;magnetic field, and rarely oblique. We also present and discuss their direction of propagation and the variation of the waves' properties with&#160;heliocentric distance.</p>

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Numerical simulation of ion reflection by lunar crustal magnetic fields

10.5194/egusphere-egu2020-18137 ◽

2020 ◽

Author(s):

Andrey Divin ◽

Jan Deca ◽

Charles Lue ◽

Roman Beliaev

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Large Scale ◽

Field Measurements ◽

Distribution Functions ◽

Three Dimensions ◽

Lunar Crust ◽

Ion Distribution ◽

Particle In Cell ◽

Reflection Model

<p>We investigate the dynamics of solar wind - Moon interaction by means of large-scale Particle-in-Cell (PIC) simulations in this study. Implicit moment PIC method and open boundaries are implemented in the code (iPIC3D) allowing to use large-scale domains in three dimensions. Even though the Moon has no global dipolar magnetic field, satellite magnetic field measurements at low-altitude (8-80 km) orbits discovered the presence of patches of intense remanent magnetization of the lunar crust. In order to simulate the scattering effect of the lunar remanent magnetic field we implemented an empirical proton reflection model based on low-attitude survey by the Chandrayaan-1 spacecraft [Lue, 2011]. In this study we focus on the day side effects only and thus do not resolve wake and limb effects. Reflected ions are found to create an energized population of particles in the solar wind and are responsible for sub-ion scale instabilities over the strongest anomalies with non-Maxwellian ion distribution functions.</p>

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Size of a plasma cloud matters

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833199 ◽

2018 ◽

Vol 616 ◽

pp. A50 ◽

Cited By ~ 13

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.

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Average cometary ion flow pattern in the vicinity of comet 67P from moment data

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2613 ◽

2020 ◽

Vol 498 (4) ◽

pp. 5263-5272

Author(s):

Hans Nilsson ◽

Hayley Williamson ◽

Sofia Bergman ◽

Gabriella Stenberg Wieser ◽

Martin Wieser ◽

...

Keyword(s):

Solar Wind ◽

Electric Field ◽

Mass Loading ◽

Ion Flow ◽

Average Flow ◽

Full Resolution ◽

Spacecraft Potential ◽

Electric Field Direction ◽

Before And After ◽

Comet 67P

ABSTRACT Average flow patterns of ions around comet 67P detected by the RPC-ICA instrument onboard Rosetta are presented both as a time series and as a spatial distribution of the average flow in the plane perpendicular to the comet – Sun direction (Y–Z plane in the coordinate systems used). Cometary ions in the energy range up to 60 eV flow radially away from the nucleus in the Y–Z plane, irrespective of the direction of the magnetic field, throughout the mission. These ions may however be strongly affected by the spacecraft potential, the uncertainty due to this is briefly discussed. Inside the solar wind ion cavity and in the periods just before and after, the cometary pick up ions moving antisunward are deflected against the inferred solar wind electric field direction. This is opposite to what is observed for lower levels of mass-loading. These pick up ions are behaving in a similar way to the solar wind ions and are deflected due to mass-loading. A spatial asymmetry can be seen in the observations of deflected pick up ions, with motion against the electric field primarily within a radius of 200 km of the nucleus and also in the negative electric field hemisphere. Cometary ions observed by RPC-ICA typically move in the antisunward direction throughout the mission. These are average patterns, full-resolution data show very much variability.

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Mass-loading, pile-up, and mirror-mode waves at comet 67P/Churyumov-Gerasimenko

Annales Geophysicae ◽

10.5194/angeo-34-1-2016 ◽

2016 ◽

Vol 34 (1) ◽

pp. 1-15 ◽

Cited By ~ 30

Author(s):

M. Volwerk ◽

I. Richter ◽

B. Tsurutani ◽

C. Götz ◽

K. Altwegg ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Dynamic Pressure ◽

Cometary Nucleus ◽

Ion Density ◽

Large Size ◽

Solar Wind Magnetic Field ◽

Mirror Mode ◽

Collisional Ionization ◽

Comet 67P

Abstract. The data from all Rosetta plasma consortium instruments and from the ROSINA COPS instrument are used to study the interaction of the solar wind with the outgassing cometary nucleus of 67P/Churyumov-Gerasimenko. During 6 and 7 June 2015, the interaction was first dominated by an increase in the solar wind dynamic pressure, caused by a higher solar wind ion density. This pressure compressed the draped magnetic field around the comet, and the increase in solar wind electrons enhanced the ionization of the outflow gas through collisional ionization. The new ions are picked up by the solar wind magnetic field, and create a ring/ring-beam distribution, which, in a high-β plasma, is unstable for mirror mode wave generation. Two different kinds of mirror modes are observed: one of small size generated by locally ionized water and one of large size generated by ionization and pick-up farther away from the comet.

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Estimating the solar wind pressure at comet 67P from Rosetta magnetic field measurements

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2018050 ◽

2019 ◽

Vol 9 ◽

pp. A3 ◽

Cited By ~ 1

Author(s):

Aniko Timar ◽

Zoltan Nemeth ◽

Karoly Szego ◽

Melinda Dósa ◽

Andrea Opitz ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Space Weather ◽

Field Measurements ◽

Wind Pressure ◽

Time Interval ◽

Pile Up ◽

Magnetic Field Measurements ◽

Solar Wind Pressure ◽

Comet 67P

Aims: The solar wind pressure is an important parameter of space weather, which plays a crucial role in the interaction of the solar wind with the planetary plasma environment. Here we investigate the possibility of determining a solar wind pressure proxy from Rosetta magnetic field data, measured deep inside the induced magnetosphere of comet 67P/Churyumov-Gerasimenko. This pressure proxy would be useful not only for other Rosetta related studies but could also serve as a new, independent input database for space weather propagation to other locations in the Solar System. Method: For the induced magnetospheres of comets the magnetic pressure in the innermost part of the pile-up region is balanced by the solar wind dynamic pressure. Recent investigations of Rosetta data have revealed that the maximum magnetic field in the pile-up region can be approximated by magnetic field measurements performed in the inner regions of the cometary magnetosphere, close to the boundary of the diamagnetic cavity, from which the external solar wind pressure can be estimated. Results: We were able to determine a solar wind pressure proxy for the time interval when the Rosetta spacecraft was located near the diamagnetic cavity boundary, between late April 2015 and January 2016. We then compared our Rosetta pressure proxy to solar wind pressure extrapolated to comet 67P from near-Earth. After the exclusion of disturbances caused by transient events, we found a strong correlation between the two datasets.

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Scattering of field-aligned beam ions upstream of Earth's bow shock

Annales Geophysicae ◽

10.5194/angeo-25-785-2007 ◽

2007 ◽

Vol 25 (3) ◽

pp. 785-799 ◽

Cited By ~ 24

Author(s):

A. Kis ◽

M. Scholer ◽

B. Klecker ◽

H. Kucharek ◽

E. A. Lucek ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Field Measurements ◽

Bow Shock ◽

Ion Distribution ◽

Parallel Side ◽

Earth’S Bow Shock ◽

High Mach ◽

The Magnetic Field

Abstract. Field-aligned beams are known to originate from the quasi-perpendicular side of the Earth's bow shock, while the diffuse ion population consists of accelerated ions at the quasi-parallel side of the bow shock. The two distinct ion populations show typical characteristics in their velocity space distributions. By using particle and magnetic field measurements from one Cluster spacecraft we present a case study when the two ion populations are observed simultaneously in the foreshock region during a high Mach number, high solar wind velocity event. We present the spatial-temporal evolution of the field-aligned beam ion distribution in front of the Earth's bow shock, focusing on the processes in the deep foreshock region, i.e. on the quasi-parallel side. Our analysis demonstrates that the scattering of field-aligned beam (FAB) ions combined with convection by the solar wind results in the presence of lower-energy, toroidal gyrating ions at positions deeper in the foreshock region which are magnetically connected to the quasi-parallel bow shock. The gyrating ions are superposed onto a higher energy diffuse ion population. It is suggested that the toroidal gyrating ion population observed deep in the foreshock region has its origins in the FAB and that its characteristics are correlated with its distance from the FAB, but is independent on distance to the bow shock along the magnetic field.

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