Sol88
Philosopher
- Joined
- Mar 23, 2009
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Originally Posted by Sol88 View Post
Cold and warm electrons at comet 67P
The 3rd post in a row irrelevant to your delusion that comets are rocks, Sol88!
Ok, let's play the devils advocate from the mainstream point of view.
LINKComets follow their elongated paths within a weak electrical field centered
on the Sun. In approaching the Sun, a charge imbalance develops between
the nucleus and the higher voltage and charge density near the Sun. Growing
electrical stresses initiate discharges and the formation of a glowing plasma
sheath, appearing as the coma and tail
Would not electrons of a high density and low electron temperature be EXPECTED?
As in
LINKFigure 6 of that study, which used spherically symmetric outgassing, shows a relatively consistently varying density in the innermost coma, out to some 30-50 km, where the expanding plasma breaks up into filaments or "spikes" of thickness less than 10 km, possibly down to the simulation grid resolution of 2.2 km.
also telling, just from the abstract, is the pulsing.
ABSTRACT Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. We present in situ measurements of plasma density, electron temperature and spacecraft potential by the Rosetta Langmuir probe instrument, LAP. Data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5--10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order -10 V. The warm (5--10 eV) electron population is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.
Could almost call that a discharge! from the comet to the solar wind?
!