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

Volwerk, M.; Richter, Ingo; Tsurutani, B. T.; Götz, Charlotte; Altwegg, Kathrin; Broiles, T. W.; Burch, J. L.; Carr, C.; Cupido, E.; Delva, M.; Dósa, Melinda; Edberg, Niklas J. T.; Eriksson, Anders; Henri, Pierre; Koenders, C.; Lebreton, Jean‐Pierre; Mandt, K.; Nilsson, Hans; Opitz, A.; Rubin, Martin; Schwingenschuh, K.; Wieser, Gabriella Stenberg; Szegö, K.; Vallat, C.; Vallières, Xavier; Glaßmeier, Karl‐Heinz

doi:10.5194/angeo-34-1-2016

Cited by 57 publications

(76 citation statements)

References 50 publications

(57 reference statements)

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“…While the ion cyclotron Mirror mode size 49.3 r 1.5 r O + mode has a higher growth rate, in the presence of heavy ions (e.g., alpha particles), the ion cyclotron growth rate will be suppressed significantly in favor of the mirror mode (Price et al, 1986). It is worth noting that similar scale size ratios have been reported for mirror mode structures formed by water group pickup ions upstream of comets (Schmid et al, 2014;Volwerk et al, 2016). It is yet to be determined whether these holes have been carried by the solar wind from smaller heliocentric distances or if they have been formed farther upstream of Mars as a result of temperature anisotropy introduced by pickup ions and then carried to the point of observation by the solar wind.…”

Section: Discussionsupporting

confidence: 53%

“…Mirror mode waves grow in high (the ratio of the plasma thermal pressure to the magnetic pressure) plasma with temperature anisotropy T ⟂ ∕T || > 1, where ⟂ and || denote directions perpendicular and parallel to the background magnetic field, respectively. As such, pickup ions are considered the main source of mirror mode wave generation in the heliosheath and in cometary environments (Burlaga et al, 2007;Glassmeier et al, 1993;Liu et al, 2007;Russell et al, 1987;Volwerk et al, 2016). Mirror mode instabilities have been frequently observed in terrestrial and planetary magnetosheaths where shock compression and field line draping cause perpendicular ion heating that provides favorable conditions for mirror mode instabilities to develop (Califano et al, 2008;Erdös & Balogh, 1996;Hubert & Harvey, 2000;Joy et al, 2006;Lucek et al, 2001;Soucek et al, 2008;Tsurutani et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Holes Upstream of the Martian Bow Shock: MAVEN Observations

et al. 2020

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Magnetic holes (MHs) are pressure-balanced structures characterized by distinct decreases in the interplanetary magnetic field strength in otherwise unperturbed solar wind. In this paper we present an analysis of MHs upstream of the Martian bow shock based on 3 months of observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Plasma properties within and around these structures as well as their shape characteristics are examined. We find an occurrence rate of around 2.1 events per day. About 51% of all events are of linear type with magnetic field rotation across the hole less than 10 • . We observe linear MHs both as isolated events and as part of a train of MHs. The proton temperature anisotropy inside MHs increases, while alpha particles remain mostly isotropic. The average electron temperature inside MHs modestly increases with increasing hole depth. The duration of linear holes at 1.5 AU shows an increase compared to durations at smaller heliocentric distances, but the structures remain asymmetrical and ellipsoid. A case study of MHs accompanied by a population of heavy pickup ions is also discussed. Plain Language SummaryThe solar wind, a supersonic flow of electrons and ions flowing radially outward from the Sun, carries a magnetic field. Magnetic holes are structures with reduced magnetic field strength that last between a few seconds to a few minutes. These structures have been observed at many places throughout the solar system. A common formation mechanism for magnetic holes is a wave mode instability that converts magnetic energy into ion thermal energy, known as the mirror mode. Mirror mode instabilities grow when the temperature of ions moving perpendicular to the magnetic field is higher than that of ions moving in the parallel direction. Mirror waves alter the magnetic field and the spatial structure of the plasma. In this paper, we use observations from the Mars Atmosphere and Volatile EvolutioN spacecraft to study magnetic holes in the space environment around Mars.

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Section: Discussionsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Magnetic Holes Upstream of the Martian Bow Shock: MAVEN Observations

et al. 2020

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“…Furthermore, 67P was found to have a plasma environment that is full of small‐scale density and magnetic field variations and where instabilities and waves are common [ Richter et al , ], complicating the interaction with the solar wind. Volwerk et al [] reported on observations of mirror‐mode waves that were generated following a compression of the plasma environment due to increased solar wind dynamic pressure. A population of suprathermal electrons (∼10–100 eV) has been observed continuously after arrival, although with significant variations in both energy and flux over time [ Clark et al , ].…”

Section: Introductionmentioning

confidence: 99%

Solar wind interaction with comet 67P: Impacts of corotating interaction regions

et al. 2016

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We present observations from the Rosetta Plasma Consortium of the effects of stormy solar wind on comet 67P/Churyumov‐Gerasimenko. Four corotating interaction regions (CIRs), where the first event has possibly merged with a coronal mass ejection, are traced from Earth via Mars (using Mars Express and Mars Atmosphere and Volatile EvolutioN mission) to comet 67P from October to December 2014. When the comet is 3.1–2.7 AU from the Sun and the neutral outgassing rate ∼1025–1026 s−1, the CIRs significantly influence the cometary plasma environment at altitudes down to 10–30 km. The ionospheric low‐energy (∼5 eV) plasma density increases significantly in all events, by a factor of >2 in events 1 and 2 but less in events 3 and 4. The spacecraft potential drops below −20 V upon impact when the flux of electrons increases. The increased density is likely caused by compression of the plasma environment, increased particle impact ionization, and possibly charge exchange processes and acceleration of mass‐loaded plasma back to the comet ionosphere. During all events, the fluxes of suprathermal (∼10–100 eV) electrons increase significantly, suggesting that the heating mechanism of these electrons is coupled to the solar wind energy input. At impact the magnetic field strength in the coma increases by a factor of 2–5 as more interplanetary magnetic field piles up around the comet. During two CIR impact events, we observe possible plasma boundaries forming, or moving past Rosetta, as the strong solar wind compresses the cometary plasma environment. We also discuss the possibility of seeing some signatures of the ionospheric response to tail disconnection events.

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“…The 40 origin and physical mechanism behind the various 41 components of the observed electron distributions is 42 unclear, but must be understood to disentangle the 43 cometary plasma dynamics. 44 …”

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confidence: 99%