Two-point observations of low-frequency waves at 67P/Churyumov-Gerasimenko during the descent of PHILAE: comparison of RPCMAG and ROMAP

Richter, Ingo; Auster, H. U.; Berghofer, G.; Carr, C.; Cupido, E.; Fornaçon, K.‐H.; Goetz, Charlotte; Heinisch, Philip; Koenders, C.; Stoll, B.; Tsurutani, B. T.; Vallat, C.; Volwerk, M.; Glaßmeier, Karl‐Heinz

doi:10.5194/angeo-34-609-2016

Cited by 36 publications

(40 citation statements)

References 25 publications

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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%

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%

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

et al. 2018

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“…The low-frequency (∼40 mHz) "singing comet waves" at 67P were first detected in August 2014 when Rosetta arrived at 67P (Richter et al 2015). More recently, Richter et al (2016) reported detection of singing comet waves from August 2014 until March 2015, when the heliocentric distance of 67P from the Sun varied from 3.6 to 2.0 AU. The waves are shown to be quasi-harmonic, large-amplitude (δB/B ∼ 1), low-frequency, and compressional in nature.…”

Section: Disappearance Of the Singing Comet Wavesmentioning

confidence: 99%

“…Prominent features are the increase in Bo and the rotation in the field direction. Detailed analyses of the magnetic field indicate the disappearance of low-frequency waves (tens of mHz), usually observed in the close plasma environment of the comet (Richter et al 2015(Richter et al , 2016Koenders et al 2016;Meier et al 2016), at the time of the outburst (see Sects. 2.3 and 2.4).…”

Section: Observationsmentioning

confidence: 99%

“…7. Small yellow and green regions within the frequency range of ∼10-100 mHz in the frequency spectrum indicate magnetic "singing comet waves" (Richter et al 2015(Richter et al , 2016Koenders et al 2016;Meier et al 2016). These singing comet waves disappear or become weakened between ∼1000 and 1300 UT, as shown by the reduced wave amplitudes shown in the right panels.…”

Section: Wave Characteristics During the Cometary Outburstmentioning

confidence: 99%

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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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“…Given that our model assuming an electric field wave works out quantitatively and there are mechanisms that could drive this wave, we conclude that waves are indeed shaping the IPS ion distribution in Pluto's wake. Comet 67P/Churyumov-Gerasimenko has been referred to as "the singing comet" (Glassmeier, 2017;Meier et al, 2016;Richter et al, 2016) thanks to its ULF waves for which we now also find evidence at "singing Pluto. "…”

Section: Discussionmentioning

confidence: 63%

Pluto's Interaction With Energetic Heliospheric Ions

et al. 2019

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Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190RP distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow‐frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

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Two-point observations of low-frequency waves at 67P/Churyumov-Gerasimenko during the descent of PHILAE: comparison of RPCMAG and ROMAP

Cited by 36 publications

References 25 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

Pluto's Interaction With Energetic Heliospheric Ions

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