Presentation on theme: "ISSI - 2. Solar Wind Interaction Q1: Scope of the applicability of different modelling approach Q2: Adequacy in reflecting important physics Q3: How important."— Presentation transcript:
Electron temperature variation Ion pileup region @ comet Halley. Collisional roto- vibrational excitation of water molecules. Electron cooling. Reduced electron recombination dissociation rate. Haeberli et al. (1995 )
Electron temperature variation Ion pileup region @ comet Halley. Collisional roto- vibrational excitation of water molecules. Electron cooling. Reduced electron recombination dissociation rate.
Ion-pileup region @ 1 AU Critical distance (r c ) for the ion pile-up region. Neutral gas density: n c ~ 3x10 6 H 2 O cm -3 at 1 AU. What about 67P? r c ~ Q ½ r c ~ 3000 km/10 ~ 300 km for Q ~ 2x10 27 H 2 O/s. Bockelee-Morvan et al. (2004 )
Ion-pileup region @ 3.25 AU For Q ~ 3x10 24 H 2 O s -1, r c ~ 15 km. Rosetta s/c will probably be in and out of the Hot electron zone/ion-pileup region. c/w p = 250 km Motschmann and Kuehrt (2006)
Ionospheric structures Ion kinetic effect: For magnetic field B ~ 10 nT and flow velocity ~ 5 km s -1, Ω ~ 0.052 rad s -1. and gyroradius R g ~ 100 km. No clear ionospheric boundary. Large variability in ionospheric structure (IMF direction dependence).
Can 67P ionosphere standoff solar wind at rendez-vous? Lorentz force = neutral gas drag force @ ionospheric boundary (Ip and Axford, 1982). At max. magnetic field, dB/dR ~ 0, R max ~ 1.1x10 -22 (Q 3/4 /a 1/2 /B max ) km
Sizing the cometary ionsphere… Q ~ 3x10 24 H 2 O s -1 and B max ~ 50 nT (max?), R max ~ km (for cold and hot electrons)! No magnetic field – free cavity. R max ~ 90 km @ perihelion, for Q ~ 3x10 27 H 2 O s -1.
Energetic pickup ions in the inner coma Eviatar et al. (1989)
Additional physics to be considered Nucleus surface and dust coma could be subject to strong sputtering effect by energetic ions during quiet solar wind condition. Much more so during solar events. Effect of enhanced ionization by X-ray/EUV emission in solar flares. How about outbursts from the nucleus?
Neutral Coma Q4: Scope of the applicability of different modeling approach Q5: Adequacy in reflecting important physics Q6: How to obatin a consistent picture of the neutral coma
Neutral gas coma The surface outgassing pattern is controlled by composition and thermal inertia distributions.