Interaction of the solar wind with comets: a Rosetta perspective

Glaßmeier, Karl‐Heinz

doi:10.1098/rsta.2016.0256

Cited by 51 publications

(49 citation statements)

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“…We show two more examples of cometary waves and wave power spectra taken from the recent European Space Agency/NASA Rosetta spacecraft encounter with comet Churyumov‐Gerasimenko (comet “C.‐G.”). Figure (top) shows the large‐amplitude (~20 nT peak‐to‐peak in an ~40 nT magnetic field) “singing comet” waves (Richter et al, , ) which are not generated by ion pickup but presumably by a cross‐current (modified ion Weibel) instability (Glassmeier, ). Although the waves appear to be a discrete mode, there is also a high‐frequency wave portion above the pump frequency.…”

Section: Resultsmentioning

confidence: 99%

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A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

et al. 2018

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Solar wind turbulence within high‐speed streams is reviewed from the point of view of embedded single nonlinear Alfvén wave cycles, discontinuities, magnetic decreases (MDs), and shocks. For comparison and guidance, cometary plasma turbulence is also briefly reviewed. It is demonstrated that cometary nonlinear magnetosonic waves phase‐steepen, with a right‐hand circular polarized foreshortened front and an elongated, compressive trailing edge. The former part is a form of “wave breaking” and the latter that of “period doubling.” Interplanetary nonlinear Alfvén waves, which are arc polarized, have a ~180° foreshortened front and with an elongated trailing edge. Alfvén waves have polarizations different from those of cometary magnetosonic waves, indicating that helicity is a durable feature of plasma turbulence. Interplanetary Alfvén waves are noted to be spherical waves, suggesting the possibility of additional local generation. They kinetically dissipate, forming MDs, indicating that the solar wind is partially “compressive” and static. The ~2 MeV protons can nonresonantly interact with MDs leading to rapid cross‐field (~5.5% Bohm) diffusion. The possibility of local (~1 AU) generation of Alfvén waves may make it difficult to forecast High‐Intensity, Long‐Duration AE Activity and relativistic magnetospheric electrons with great accuracy. The future Solar Orbiter and Solar Probe Plus missions should be able to not only test these ideas but to also extend our knowledge of plasma turbulence evolution.

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Section: Resultsmentioning

confidence: 99%

“…We note that these waves have a power spectrum of ~ f −1.9 from 2 × 10 1 to 5 ×10 2 mHz. Adapted from Glassmeier ().…”

Section: Resultsmentioning

confidence: 99%

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

et al. 2018

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“…The interaction of an active comet with the solar wind is an interesting physical process in the context of mass-loaded space plasmas (e.g., Szegö et al 2000;Coates & Jones 2009;Glassmeier 2017). Previous studies concentrate on interaction scenarios where the activity is steady.…”

Section: Introductionmentioning

confidence: 99%

Impact of a cometary outburst on its ionosphere

Hajra¹,

Henri²,

Vallières³

et al. 2017

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We present a detailed study of the cometary ionospheric response to a cometary brightness outburst using in situ measurements for the first time. The comet 67P/Churyumov-Gerasimenko (67P) at a heliocentric distance of 2.4 AU from the Sun, exhibited an outburst at ∼1000 UT on 19 February 2016, characterized by an increase in the coma surface brightness of two orders of magnitude. The Rosetta spacecraft monitored the plasma environment of 67P from a distance of 30 km, orbiting with a relative speed of ∼0.2 m s −1 . The onset of the outburst was preceded by pre-outburst decreases in neutral gas density at Rosetta, in local plasma density, and in negative spacecraft potential at ∼0950 UT. In response to the outburst, the neutral density increased by a factor of ∼1.8 and the local plasma density increased by a factor of ∼3, driving the spacecraft potential more negative. The energetic electrons (tens of eV) exhibited decreases in the flux of factors of ∼2 to 9, depending on the energy of the electrons. The local magnetic field exhibited a slight increase in amplitude (∼5 nT) and an abrupt rotation (∼36.4• ) in response to the outburst. A weakening of 10-100 mHz magnetic field fluctuations was also noted during the outburst, suggesting alteration of the origin of the wave activity by the outburst. The plasma and magnetic field effects lasted for about 4 h, from ∼1000 UT to 1400 UT. The plasma densities are compared with an ionospheric model. This shows that while photoionization is the main source of electrons, electron-impact ionization and a reduction in the ion outflow velocity need to be accounted for in order to explain the plasma density enhancement near the outburst peak.

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“…At weak comets, early phase implanted ions are important (Stage 1, section 3 above -see [25,8,3,7]). The mass loading associated with these slows the plasma enough that eventually a bow shock forms.…”

Section: Pickup Ions Dominate the Comet-sw Interactionmentioning

confidence: 99%

Pickup Particle Acceleration at Comets, Moons and Magnetospheres

Coates

2017

J. Phys.: Conf. Ser.

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Abstract. Ionisation of neutrals plays a key role in the plasma interactions of comets and moons, and in magnetospheres. Following ionisation, ions and electrons are 'picked up' in the plasma flow, initially accelerating along the electric field and then gyrating around the magnetic field. For an ion with mass m (amu) this leads to an acceleration of up to 4m times the energy of the flowing plasma. Further scattering in pitch angle and energy may increase the acceleration further. Here, we illustrate the process at work with relevant plasma measurements from comets including Rosetta's comet 67P, from Titan and near Enceladus and Rhea.

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Interaction of the solar wind with comets: a Rosetta perspective

Cited by 51 publications

References 61 publications

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

Impact of a cometary outburst on its ionosphere

Pickup Particle Acceleration at Comets, Moons and Magnetospheres

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