Auroral-related mid-infrared emission on Jupiter
from IRTF-TEXES, Cassini-CIRS
Jupiter Aurora Workshop
1
1
2
3
4
James Sinclair ,Glenn Orton , Thomas Greathouse , Leigh Fletcher , Patrick Irwin , Yasumasa Kasaba
1Jet
Propulsion Laboratory, California Institute of Technology, 2Southwest Research Institude, 3University of
Leicester, 4Atmospheric, Oceanic & Planetary Physics, University of Oxford, 5Tohoku University
5
Support of Juno in the mid-infrared
Using spacecraft (Cassini, Voyager) and ground-based imaging/spectroscopy in the
thermal infrared to derive meteorological parameters in support of Juno.
Tropospheric variability (Orton et al., 2015, DPS)
Auroral-related emission
Jupiter at 8.7-μm and 10.30-μm from SubaruCOMICS in 2011
NH3 gas at 490 mbar
NH3 ice
Retrieved NH3 gas and NH3 ice parameters in the
0.2 - 0.5 bar levels
North (top) and south (bottom)
polar projections of Jupiter at 7.8μm (Jan 2017).
Aurora-related mid-infrared emission
• Analysing mid-infrared auroral emission using both ground-based and spacecraft
spectroscopy.
spacecraft: Voyager-IRIS (R = 250), Cassini-CIRS (R = 66-4000), no
telluric contamination.
-
ground-based: IRTF-TEXES (R = 65000-85000), higher spectral
resolution (which sounds larger altitude range).
Observations from Cassini-CIRS (2000)
Observations from IRTF-TEXES (Dec 2014)
-
130
125
125
180
120
System III longititude
130
135
60
140
145
Brightness Temperature (K)
Planetographic Latitude
Brightness temperature at 822 cm
90
80
70
60
50
40
-40
-50
-60
-70
-80
-90
360
137
-1
140
135
300
240
130
132
180
120
System III longititude
135
Planetographic Latitude
Brightness temperature at 1305 cm-1
-40
-50
-60
-70
-80
-90
360
165
135
135
60
140
Brightness Temperature (K)
90
80
70
60
50
40
C 2H 2
132
132
0
160
160
155
160
155
160
300
240
180
120
System III longititude
155
160
165
60
300
C 2H 4
160
155
-45
-60
-75
-90
360
130
CH4
160
0
160
170
Brightness Temperature (K)
105
-45
-60
-75
-90
360
300
110
60
0
115
Brightness temperature (K)
C2H2, 729.55 cm-1
C2H6, 822.32 cm-1
240
180
120
System III Longitude
60
140
170
150
160
0
-45
-60
-75
-90
360
300
130
60
140
170
150
160
CH4, 1245.22 cm-1
240
180
120
System III Longitude
60
120
150
140
240
180
120
System III Longitude
Brightness temperature (K)
C2H4, 949.35 cm-1
130
C 2H 6
90
75
60
45
Brightness temperature (K)
90
75
60
45
110
150
240
180
120
System III Longitude
90
75
60
45
145
170
160
300
100
C 2H 6
135
13
5
135
132
150
137
135
132
0
-45
-60
-75
-90
360
Planetographic Latitude
120
240
130
135
90
75
60
45
Planetographic Latitude
130
300
-1
2
125
360
H2 S(1) H S(1), 587.03 cm
125
130
135 140
Planetographic Latitude
125
Planetographic Latitude
-40
-50
-60
-70
-80
-90
C 2H 2
130
Planetographic Latitude
Planetographic Latitude
Brightness temperature at 730 cm-1
90
80
70
60
50
40
0
90
75
60
45
-45
-60
-75
-90
360
300
Brightness temperature (K)
130
CH4
240
180
120
System III Longitude
60
140
170
150
160
180
Brightness temperature (K)
0
0
Questions
2) Do auroral processes affect the
concentrations of C2H2, C2H4, C2H6?
3)Does the auroral-related mid-infrared
emission vary with (time) solar cycle?
300
Monthly-Averaged Sunspot Number
1) What mechanism yields the high
temperatures in the neutral atmosphere in
auroral regions?
Voyager
Cassini
IRTF-TEXES
200
100
0
1980
1990
2000
Year
2010
To address these questions:
-
Perform retrieval analysis of Cassini-CIRS and IRTF-TEXES spectra.
-
Retrievals of the vertical profiles of temperature, C2H2, C2H6 performed
using Nemesis (Irwin et al., 2008), an radiative transfer inversion code.
2020
Temperature results
Cassini-CIRS (Δν = 2.5 cm-1, 2000)
170
170
-40
-50
-60
-70 160
-80
-90
360
160
300
170
160
240
180
120
System III longititude
60
0
180
-40 170
-50 160
-60
-70
170
-80
-90
360
300
155
160
60
165
Planetographic Latitude
Planetographic Latitude
0
170
175
90
80
70
60
50
40
0
17
-40
-50
-60
-70
-80
-90
360
Temperature (K)
170
170
-40
-50 170
-60
-70
-80
-90
360
180
170
190 180
170
300
185
240
180
120
System III longititude
190
195
60
200
160
160
150
300
240
180
120
System III longititude
60
0
90
80
70
60
50
40
170
160
160
-40
-50
-60
-70
-80
-90
360
160
160
300
Temperature at 0.1 mbar
170
0
150
17
180
240
180
120
System III longititude
0
17
0
300
60
0
0
17
170
170
240
180
120
System III longititude
0
170
170
170
170
180
170
18
170
170
170
19
-40
-50
-60
-70
-80
-90
360
170
160
Temperature at 0.01 mbar
180
170
0
17
170
170
Temperature at 0.1 mbar
90
80
70
60
50
40
190
170
Temperature at 0.98 mbar
Planetographic Latitude
170
Planetographic Latitude
170
Temperature at 4.7 mbar
90
80
70
60
50
40
0
90
80
70
60
50
40
-40
-50
-60
-70
-80
-90
360
160
160
300
140
240
180
120
System III longititude
145
150
160
240
180
120
System III longititude
60
0
Temperature at 0.01 mbar
Planetographic Latitude
170
170
90
80
70
60
50
40
Planetographic Latitude
Temperature at 0.98 mbar
Planetographic Latitude
Planetographic Latitude
Temperature at 4.7 mbar
90
80
70
60
50
40
IRTF-TEXES (Δν = 0.0015 cm-1, 2014)
60
155
0
90
80
70
60
50
40
160
17
0
160
-40
-50
-60
-70
-80
-90
360
160
160
160
160
160
170
300
165
240
180
120
System III longititude
170
175
160
60
180
Temperature (K)
• No auroral-related stratospheric heating at pressures of 4.7 mbar or higher (Flasar
et al., 2004).
• Auroral-related heating at pressures from ~1 mbar to ~10 μbar (at least over range
in pressures sounded in the mid-infrared).
• Larger enhancements in temperature at 10-μbar and 0.98-mbar level, less at 0.1
mbar.
0
Temperature results
10−5
70oN, 180oW + 20
o
o
100 70 N, 60 W
Pressure (mbar)
10−4
80
60
40
20
1240
1260
1280 1300 1320 1340
Wavenumber (cm−1)
1360
1380
10−1
100
120
140
160
180
200
Temperature (K)
220
240
160
180
200
Temperature (K)
220
240
220
240
(Δν=0.5 cm-1)
Cassini−CIRS (∆ν = 0.25 cm−1, North)
10−5
150 COMPSIT−NA + 60
COMPSIT−NQ
10−4
100
50
10−3
10−2
10−1
100
101
1240
1260
1280 1300 1320 1340
Wavenumber (cm−1)
1360
102
100
1380
120
140
(Δν=0.5 cm-1)
Cassini−CIRS (∆ν = 0.25 cm−1, South)
10−5
120 COMPSIT−SA + 50
10−4
COMPSIT−SQ
100
Pressure (mbar)
Radiance (nW cm−2 sr−1 cm)
10−2
102
100
0
0
• Temperature minima at 0.1
mbar where there is less
altitudinal sensitivity in the
spectra?
10−3
101
Pressure (mbar)
• Temperature maxima at 10μbar (but may be an artefact
of the temperature the
apriori).
Radiance (nW cm−2 sr−1 cm)
• Temperature maxima at 1
mbar.
120
Radiance (nW cm−2 sr−1 cm)
In both CIRS and TEXES
results:
(Δν=2.5 cm-1)
Cassini−CIRS ∆ν = 2.5 cm−1
80
60
40
20
10−3
10−2
10−1
100
101
0
1240
1260
1280 1300 1320 1340
Wavenumber (cm−1)
1360
1380
102
100
120
140
160
180
200
Temperature (K)
Temperature results
H2 S(1) emission
• Temperature maxima at 10μbar (but may be an artefact
of the temperature the
apriori).
Radiance (nW cm-2 sr-1 cm)
• Temperature maxima at 1
mbar.
800
600
400
200
0
70oN, 1800W + 20
70oN, 600W
150
100
50
0
587.01
587.02 587.03 587.04
Wavenumber (cm-1)
10-4
587.05
587.06
1245.3
Temperature Retrieval
1245.6
1245.9
1246.5
Wavenumber (cm-1)
A Priori
70oN, 1800W
70oN, 600W
10-2
100
102
100
• Temperature minima at 0.1
mbar where there is less
altitudinal sensitivity in the
spectra?
CH4 emission
200
70oN, 1800W + 100
70oN, 600W
Pressure (mbar)
In both CIRS and TEXES
results:
Radiance (nW cm-2 sr-1 cm)
1000
120
140
160
Temperature (K)
180
200
1246.8
Temperature results
Test alternative temperature a priori profiles to
determine robustness
CIRS−∆ν = 2.5 cm−1 tests
10−4
Tested: - nominal (shown on red)
- an isotherm of 160 K (green)
- an isotherm of 200 K (cyan)
- nominal but with a 200 K isotherm
above the 10-μbar level (blue)
Pressure (mbar)
10−3
70°N, 180°W
10−2
10−1
1
10
102
100
120
140
160
180
Temperature (K)
200
220
CIRS−∆ν = 0.5 cm−1 (North) tests
10−4
Conclusions:
• Temperature maxima at ~1 mbar level and
temperature minima at ~0.1 mbar appears robust
regardless of initial assumptions.
Temperature maxima at ~1 mbar a result of
auroral ‘soot’ or haze particles which are
heated by sunlight.
Pressure (mbar)
70°N, 180°W
10−2
10−1
1
10
102
100
120
140
160
180
Temperature (K)
200
220
CIRS−∆ν = 0.5 cm−1 (South) tests
10−4
10−3
Pressure (mbar)
• Temperature maximum at 10-μbar was an artefact
of the nominal a priori: most likely an isotherm at
pressures lower than 10-μbar.
10−3
75°S, 60°W
10−2
10−1
1
10
102
100
120
140
160
180
Temperature (K)
200
220
Temperature results
Test alternative temperature a priori profiles to
determine robustness
10-4
Pressure (mbar)
Tested: - nominal (shown on red)
- an isotherm of 160 K (green)
- an isotherm of 200 K (cyan)
- nominal but with a 200 K isotherm
above the 10-μbar level (blue)
TEXES tests: 70oN, 180oW
Conclusions:
• Temperature maxima at ~1 mbar level and
temperature minima at ~0.1 mbar appears robust
regardless of initial assumptions.
Temperature maxima at ~1 mbar a result of
auroral ‘soot’ or haze particles which are
heated by sunlight.
10-2
10-1
1
10
102
100
120
140 160 180
Temperature (K)
200
220
TEXES tests: 75oS, 60oW
10-4
Pressure (mbar)
• Temperature maximum at 10-μbar was an artefact
of the nominal a priori: most likely an isotherm at
pressures lower than 10-μbar.
10-3
10-3
10-2
10-1
1
10
102
100
120
140 160 180
Temperature (K)
200
220
Solar cycle variation?
Solar activity twice as high in 2000 (during CIRS flyby) compared to 2014 when
TEXES spectra were acquired. Is auroral-related emission higher when solar
activity is higher?
• BUT, a similar offset in radiances at 70°N,
60°W where auroral processes should have
no effect?
• Systematic offset in TEXES and CIRS
radiances
- blurring of auroral features by
diffraction/seeing.
- radiometric calibration issues?
Radiance (nW cm−2 sr−1) cm)
• CIRS radiances in CH4 emission about 2 x
brighter than TEXES at 70°N, 180°W.
100
80
Cassini−CIRS (2001)
at 70oN, 180oW
TEXES Forward model
at 70oN, 180oW
60
40
20
0
1240 1260 1280 1300 1320 1340 1360 1380
Wavenumber (cm−1)
70oN, 60oW
Radiance (nW cm−2 sr−1) cm)
• TEXES temperature results forward modelled
at same spectral resolution and emission
angle as CIRS Δν=2.5 cm-1 observations.
70oN, 180oW
50
40
Cassini−CIRS (2001)
at 70oN, 6oW
TEXES Forward model
at 70oN, 6oW
30
20
10
0
1240 1260 1280 1300 1320 1340 1360 1380
Wavenumber (cm−1)
Solar cycle variation?
70oN, 60oW
50
Cassini−CIRS (2001)
TEXES forward model
using nominal calibration
• Perform temperature retrievals (again) of
TEXES spectra at 70°N, 180°W using
adjusted calibration and compare with CIRS.
TEXES forward model
using adjusted calibration
40
Radiance (nW cm−2 sr−1) cm)
• All TEXES radiances scaled by offset in
radiance required to match TEXES and CIRS
radiances at 70°N, 60°W.
30
20
10
0
1240
• CH4 emission at 70°N, 180°W appears very
similar during periods of different solar
activity.
1260
1280
1300
1320
Wavenumber (cm−1)
1340
1360
1380
70oN, 180oW
120
Cassini-CIRS (2001)
TEXES forward model
using adjusted calibration
• Aim to confirm this using awarded TEXES
time in May 2016.
Radiance (nW cm-2 sr-1) cm)
100
80
60
40
20
0
1240
1260
1280
1300
1320
Wavenumber (cm-1)
1340
1360
1380
Conclusions
• Retrievals of the vertical temperature profile from both Cassini-CIRS and IRTFTEXES spectra indicate a maximum in temperature at the 1 mbar level in both
northern and southern auroral regions.
• This feature is considered to be a result of auroral-produced haze particles/
aerosols/‘soot’ which are heated by sunlight.
• Temperatures at pressures lower and including 10-μbar are likely isothermal due
to joule heating.
• No difference in auroral-related CH4 emission between 2014 and 2010 (where
solar activity was different).
Hydrocarbon results
C2H2 at 1 mbar
C2H2 at 0.1 mbar
166 198
134
166
198
229
45
198
229
229
198 166
-60
166
-75
300
240
150
200
166
180
120
System III longititude
250
300
60
300
Planetographic Latitude
7
9
1 4
11 12 816
97 5
120
60
300
5
240
6
22
24
-60
3129
-75
300
240
25
24
29
31
3326
24
26
180
System III longititude
30
120
60
35
45
−45
4744
−75
300
40
90
7
99
8
8 7
9
180
System III longititude
7
8
Planetographic Latitude
7
9 8
9
C2H6 (ppmv)
8
120
9
7
60
10
0
11
60
45
-45
14
-60
14
13
13
14
14
14
14 13
-75
-90
360
300
240
10
180
System III longititude
12
C2H6 (ppmv)
120
60
14
0
75
13 1144
15
15
60
45
44
47
5041
41
180
System III longititude
40
45
90
10
9 11 1112
14
14
75
35
38
240
35
0
9
38
C2H4 (ppbv)
8
60
8
38
C2H6 at 100 µbar
7
120
38
−60
−90
360
0
47
41 44
60
7
5 5
6
7
444
5350
38
75
C2H4 (ppbv)
9
-90
360
-45
22
C2H6 at 0.1 mbar
-45
-75
45
20
5 67
7
8
9 9 8
9
10 9
180
System III longititude
6
7
C2H4 (ppbv)
9
-60
5
C2H6 at 1 mbar
7
45
240
4
6 7 7
6
90
33
33 3539 37
26 29 31
24
60
-90
360
0
90
60
300
5
7
8 7
7 6
5
C2H2 (ppmv)
180
System III longititude
10
15
75
−75
−90
360
0
7
7
8
−45
−60
6
5
8
C2H4 at 100 µbar
240
5
60
7
45
5
C2H2 (ppbv)
5
9 7
-75
120
6
C2H4 at 0.1 mbar
45
-60
180
System III longititude
3
4
4
4
3
60
C2H2 (ppbv)
75
-45
240
2
3
3 3
75
C2H4 at 1 mbar
90
5
300
2
75
-90
360
Planetographic Latitude
-75
3
3
4
333
4
4
4
3 3
3
-60
90
60
4
-45
3
3
2
3
3
45
400
2
2
60
-90
360
0
350
75
Planetographic Latitude
-45
-90
360
Planetographic Latitude
9 1
2226
Planetographic Latitude
60
Planetographic Latitude
75
C2H2 at 100 µbar
90
Planetographic Latitude
90
3
Planetographic Latitude
90
15
120
60
50
0
55
15
15
−45
−60
16
−75
−90
360
300
13
1516
240
14
180
System III longititude
15
C 2H 6
15
120
60
16
0
-40
-50
-60
-70
-80
-90
360
C2H6 at 4.7 mbar
6 .6373
28.45527
922
30.0
30.9105
Planetographic Latitude
Planetographic Latitude
C2H2 at 4.7 mbar
90
80
70
60
50
40
29.2739 22
9
30.05
910
30.
30.0
922
30.0922
300
2
30.09229.2739
240
180
120
System III longititude
27.8
29.5
31.1
60
32.7
0
90
80
70
60
50
40
-40
-50
-60
-70
-80
-90
360
4.17208
3.95854
3.53146
3.313.74500
792
3.53146
3.1
043
3.53146
3.31792
300
34.4
240
180
120
System III longititude
2.99
3.42
Acetylene (ppbv)
Planetographic Latitude
Planetographic Latitude
329.618
18
29.6
3
318.631
44
318.631307.6
240
180
120
System III longititude
308
330
352
374
60
0
90
80
70
60
50
40
-40
-50
-60
-70
-80
-90
360
396
9.2506
0
8.78470
9.259.71650 10.64
10.83
1824
060
188
0
80
0
300
7.45
240
180
120
System III longititude
8.39
9.32
10.25
11.18
Ethane (ppmv)
C2H6 at 0.1 mbar
07244
5.361
5.16
8
47
.25
atitude
atitude
478
8.3
8.318
C2H2 at 0.1 mbar
5.25
4.70
8.7847
Acetylene (ppbv)
90
80
70
60
0
C2H6 at 1.0 mbar
296.657
4
307.64318.631
318.631
-40
-50
-60
-70 329.618
-80
-90
360
300
4.27
60
Ethane (ppmv)
C2H2 at 1.0 mbar
90
80
70
60
50
40
3.84
8
3.10438
90
80
70
60
113
15.5
15.
1602
3 15.8624 16.2135
511
15.
60
0
Aurora-related mid-infrared emission
HST-STIS (Ultraviolet)
Jupiter from Subaru-COMICS in
January 2017 at 7.8-μm:
• Jupiter’s aurora also appear bright in the mid-infrared.
• Enhanced CH4 emission (temperature probe) indicates auroral
processes elevate temperatures in the neutral stratosphere.
• Enhanced emission of further hydrocarbons such as C2H2, C2H4 and
C6H6 indicates possible auroral influence on photochemistry in the
stratosphere.