# Warm and Cold Electrons at Comet 67P

Anders Eriksson, Ilka Engelhardt, Fredrik Johansson, Elias Odelstad, Erik Vigren, Mats André, Pierre Henri, Kathleen Mandt, Thomas Broiles, Marina Galand

► To cite this version:

Anders Eriksson, Ilka Engelhardt, Fredrik Johansson, Elias Odelstad, Erik Vigren, et al. Warm and Cold Electrons at Comet 67P. 19th EGU General Assembly, Apr 2017, Vienne, Austria. pp.13936. insu-03568129

HAL Id: insu-03568129

https://insu.hal.science/insu-03568129

Submitted on 13 Feb 2022

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Warm and Cold Electrons at Comet 67P

Anders Eriksson (1), Ilka Engelhardt (1,2), Fredrik Johansson (1,2), Elias Odelstad (1,2), Erik Vigren (1), Mats André (1), Pierre Henri (3), Kathleen Mandt (4), Thomas Broiles (4), and Marina Galand (5)

(1) Swedish Institute of Space Physics, Uppsala, Sweden (anders.eriksson@irfu.se), (2) Department of Physics and Astronomy, Uppsala University, Sweden, (3) LPC2E, CNRS, Université d'Orléans, France, (4) Southwest Research Institute, San Antonio, TX, USA, (5) Department of Physics, Imperial College, London, UK

Cometary electrons are born at typical energies of order 10 eV, but can cool to the temperature of the surrounding
neutral gas (a few hundred K) by collisions. The collision rate depends on the density of the neutral gas, so outside
some cometocentric distance we may call the collisionopause or exobase the cooling is inefficient, and two popula-
tions of warm (order 10 eV) and cold (below 0.1 eV) may be expected. In situ observations by Rosetta show that the
electron flux at the position of the spacecraft was dominated by the warm population [1] throughout the mission.
On the other hand, detailed modelling of some events [2,3] show that the flow of recently ionized molecules more
or less follows the neutral gas. This is consistent with estimates based on the neutral gas density [4] suggesting
the electron collisionopause was almost always inside of the Rosetta position but the ion collisionopause was
further out at least for the months around perihelion. We present electron measurements from the instruments of
the Rosetta Plasma Consortium, compare to model calculations, and discuss the physics of this intermediate region.

[1] Odelstad et al, GRL, 42, 10126 (2015)

[2] Vigren et al., Astron. J., 152, 59 (2016)

[3] Galand et al, MNRAS, 462, S331 (2016)

[4] Mandt et al., MNRAS, 462, S9 (2016)