H 3 + in Giant Planet Ionospheres Tom Stallard Tom Stallard H 3 + in Giant Planet Ionospheres R OYAL S OCIETY M EETING : C HEMISTRY, ASTRONOMY AND PHYSICS OF H 3 + Henrik Melin, Steve Miller, James O’Donoghue Stan W.H. Cowley, Sarah V. Badman, Alberto Adriani, Robert H. Brown, Kevin H. Baines

H 3 + in Giant Planet Ionospheres Tom Stallard 1.8 μm 4.2 μm Jupiter absorption Earth absorption

H 3 + in Giant Planet Ionospheres Tom Stallard H 2 + e*H e + e 2 2 H 2 + h H e

H 3 + in Giant Planet Ionospheres Tom Stallard H, H 2 H 2 = H 2 + H H 2 = H 3 + … … … H Energetic particle precipitation

H 3 + in Giant Planet Ionospheres Tom Stallard

MeasuredCalculated Jupiter940 K203 K Saturn420 K177 K Uranus800 K138 K Neptune600 K132 K Lam et al., 1997 Yelle and Miller, 2004 Temperature changes and energy inputs in Giant Planet atmospheres: what we are learning from H 3 + observations

H 3 + in Giant Planet Ionospheres Tom Stallard Uranus 1987

H 3 + in Giant Planet Ionospheres Tom Stallard Uranus 2007

H 3 + in Giant Planet Ionospheres Tom Stallard Melin et al., 2011

H 3 + in Giant Planet Ionospheres Tom Stallard Melin et al., 2011

H 3 + in Giant Planet Ionospheres Tom Stallard Jupiter

H 3 + in Giant Planet Ionospheres Tom Stallard Heating/cooling term8 September11 September Joule heating and ion drag67.0 mW m− mW m−2 Particle precipitation10.8 mW m−212.0 mW m−2 Downward conduction(−)0.3 mW m−2(−)0.4 mW m−2 E(H 3 + ) cooling(−)5.1 mW m−2(−)10.0 mW m−2 Hydrocarbon cooling(−)65.5 mW m−2(−)103.3 mW m−2 Net heating rate7.4 mW m− mW m−2 Stallard et al., 2001; 2002 Melin et al., 2005

H 3 + in Giant Planet Ionospheres Tom Stallard Heating/cooling term8 September11 September Joule heating and ion drag67.0 mW m− mW m−2 Particle precipitation10.8 mW m−212.0 mW m−2 Downward conduction(−)0.3 mW m−2(−)0.4 mW m−2 E(H 3 + ) cooling(−)5.1 mW m−2(−)10.0 mW m−2 Hydrocarbon cooling(−)65.5 mW m−2(−)103.3 mW m−2 Net heating rate7.4 mW m− mW m−2 Stallard et al., 2001; 2002 Melin et al., 2005

H 3 + in Giant Planet Ionospheres Tom Stallard Saturn ± 70 K (17 September 1999) 420 ± 70 K (2 February 2004) Melin et al., ± 50 K (10 September 2008) Melin et al., 2011

H 3 + in Giant Planet Ionospheres Tom Stallard R-branchP-branchQ-branch

H 3 + in Giant Planet Ionospheres Tom Stallard Auroral variability: Solar wind variations Variations at the planetary period Variations associated with magnetospheric conditions

H 3 + in Giant Planet Ionospheres Tom Stallard

Median Time of observation TemperatureRenormalised emission a) + b)04:35611 K (±20)0.934 c) + d)08:50611 K (±20)1.000 e) + f)13:04567 K (±20) K in 254 minutes represents a temperature change of mKs -1 cooling rate of: 7.8x10 12 W for the whole column above the homopause 3.2x10 12 W for the column above the main H 3 + emission layer

H 3 + in Giant Planet Ionospheres Tom Stallard Summary Uranus has shown long-term variability aligned with seasonal changes suggests connections with the magnetospheric structure or the deep atmosphere Jupiter has shown the importance of Joule heating and ion drag suggests heating from the lower thermosphere Saturn has shown significant variability, including significant cooling, on short timescales suggests in-situ energy exchange, through winds By understanding why different planets are affected in such different ways and the energy inputs that drive these differences, we will make significant strides into explaining why the upper atmospheres are so hot