H 3 + in Giant Planet Ionospheres Tom Stallard Tom Stallard H 3 + in Giant Planet Ionospheres R OYAL...

H3+ in Giant Planet Ionospheres Tom Stallard

Tom Stallard

H3+ in Giant Planet Ionospheres

Royal Society Meeting: Chemistry, astronomy and physics of H3+

Henrik Melin, Steve Miller, James O’DonoghueStan W.H. Cowley, Sarah V. Badman, Alberto Adriani, Robert H. Brown, Kevin H. Baines


1.8 μm 4.2 μm

Jupiter absorptionEarth absorption


1

11

H2 + e* H2+ + e + e

2

2 H2 + h H2+ + e


H, H2 H2 = H2+ H2

+ + H2 = H3+ … … … H3

+

1 2 3

Energetic particle precipitation


Measured Calculated

Jupiter 940 K 203 K

Saturn 420 K 177 K

Uranus 800 K 138 K

Neptune 600 K 132 K

Lam et al., 1997

Yelle and Miller, 2004

Temperature changes and energy inputs in Giant Planet

atmospheres: what we are learning from H3

+ observations


Uranus

1987


Uranus

2007


Melin et al., 2011


Jupiter


Heating/cooling term 8 September 11 September

Joule heating and ion drag 67.0 mW m−2 277.0 mW m−2

Particle precipitation 10.8 mW m−2 12.0 mW m−2

Downward conduction (−)0.3 mW m−2 (−)0.4 mW m−2

E(H3+) 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 rate 7.4 mW m−2 175.3 mW m−2

Stallard et al., 2001; 2002

Melin et al., 2005


Saturn

1

1 380 ± 70 K (17 September 1999)420 ± 70 K (2 February 2004)

Melin et al., 2007

22 440 ± 50 K (10 September 2008) Melin et al., 2011


R-branch P-branchQ-branch


Auroral variability:

•Solar wind variations•Variations at the planetary period•Variations associated with magnetospheric conditions


Median Time of observation

Temperature Renormalised emission

a) + b) 04:35 611 K (±20) 0.934c) + d) 08:50 611 K (±20) 1.000e) + f) 13:04 567 K (±20) 0.498

• 44K in 254 minutes represents a temperature change of 2.887 mKs-1

• cooling rate of:

7.8x1012 W for the whole column above the homopause

3.2x1012W for the column above the main H3

+ emission layer


SummaryUranus 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

H 3 + in Giant Planet Ionospheres Tom Stallard Tom Stallard H 3 + in Giant Planet Ionospheres R OYAL...

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