Multi-spectral simultaneous diagnosis of
Saturn's aurorae throughout a planetary rotation
submitted to JGR
L. Lamy, R. Prangé, W. Pryor, J. Gustin, S. Badman,
H. Melin, T. Stallard, D. Mitchell, P. Brandt
INCA
Ion and Neutral CAmera
RPWS
Radio Plasma Wave Science
VIMS
Visual and Infrared Mapping
Spectrometer
UVIS
UltraViolet Imaging Spectrometer
This presentation :
a quicklook on the use of
UVIS observations
Multi-spectral simultaneous diagnosis of
Saturn's aurorae throughout a planetary rotation
ENA
SKR
eH 3+
INCA
Ion and Neutral CAmera
H, H2
RPWS
Radio Plasma Wave Science
VIMS
Visual and Infrared Mapping
Spectrometer
UVIS
UltraViolet Imaging Spectrometer
Summary of observations
1
2009-27 14:49:17 (5.9min)
VIMS
11
2009-027 18:20:15
2
3
2009-027 15:14:26 (65min)
2009-027 16:26:42 (8.8min)
12
13
2009-027 18:51:13
2009-027 19:05:52
2009-027 14:58:58 (8.8min)
2009-027 18:35:24
4
14
5
6
2009-027 16:42:21
2009-027 16:57:50
15
16
2009-027 19:21:11
2009-027 19:37:00
7
8
2009-027 17:12:59
2009-027 17:28:48
17
18
2009-027 19:51:49
9
10
19
20
2009-027 20:33:58 (65min)
2009-027 17:43:17
2009-027 20:09:18 (5.9min)
2009-027 20:18:18 (10min)
2009-027 17:58:26
-2
(b, IR)
XZ
Z
-1
-6
W.m .sr
8.10
X
Y
-6
4.10
21
22
23
24
25
26
27
28
29
2009-027 21:46:44 (8.8min)
2009-027 22:01:33
2009-027 22:17:12
2009-027 22:32:21
2009-027 22:48:10
2009-027 23:03:39
2009-027 23:18:18
2009-027 23:39:37
2009-027 23:54:36
30
31
32
33
34
35
36
37
38
39
2009-028 00:10:55
2009-028 00:25:14
2009-028 00:41:23
2009-028 00:56:52
2009-028 01:11:41
2009-028 01:28:10 (5.9min)
2009-028 01:37:20 (10min)
2009-028 01:52:44 (65min)
2009-028 03:04:50 (8.8min)
2009-028 03:20:49
a
INCA
b
c
d
e
VIMS
Y
0
2009-027 03:10:47-03:50:47
2009-027 11:45:47-12:15:47
UVIS
-2
-1
Log W.m .Hz
1000
-19
Z
Z
RPWS
(a, radio)
Frequency (kHz)
-20
X
Y
X
Y
-21
100
-22
-23
2009-027 14:15:47-14:45:47
2009-027 22:15:48-22:45:48
Z
Z
10
-24
DOY 2009
r sc (R S)
sc
TL sc (h:m)
27
17.9
-34.0
09:15
(a) 2009-027
16:26:07
18:11:43
a1
27.5
18.8
-24.2
09:35
a2
28.5
19.7
-6.15
10:05
28
19.4
-15.0
09:51
a3
a4
a5
a6
29
19.6
2.62
10:19
X
Y
INCA
a7
(d, ENA)
(b) 2009-027
18:19:07
20:04:43
UVIS
(c, UV)
(c) 2009-027
21:45:37
23:32:13
X
Y
2009-028 00:15:48-00:45:48
2009-028 02:15:48-02:45:48
Z
Z
1
b1
c1
b2
c2
b3
b4
c3
c4
b5
c5
b6
c6
b7
0
c7
Y
X
Y
X
S
(d) 2009-028
23:38:37
01:24:13
d1
d2
d3
d4
30
(e) 2009-028
03:04:38
03:34:22
3
e1
e2
0.3
kR FUV
(120-175nm)
d5
d6
d7
-1
Log Cnts
(cm 2.sr.s.keV)-1
2009-028 14:55:47-15:15:47
2009-028 16:15:47-16:45:47
UVIS data
- FUV channel : 112-191 nm
- 64 spatial pixels along the slit : 1x1.5 mrad FOV
- low spectral resolution : λ/Δλ ~ 60 and 32 spectral pixels
reflected light
auroral
signal
=> need for a specific processing to extract auroral emissions of H-Lya and H2 only
UVIS data
* Individual spectral processing of each spatial pixel :
Spectral brightness (kR/nm)
(a)
5
UVIS spectral pixels
10
15
20
25
30
(b)
5
UVIS spectral pixels
10
15
20
25
30
0.4
0.3
auroral
signal
0.2
reflected
light
absorption
0.1
120
140
160
Wavelength (nm)
1- Correction for
background emission
180
120
140
160
Wavelength (nm)
180
2- Correction for methane
absorption at low wavelengths
UVIS data
* Results :
Auroral H2
Auroral H-Lya
kR
(a)
original kR
over 120-175nm
kR
30
3
3
0.3
0.3
(b)
kR of non absorbed H2
over 75-175nm
(c)
0.03
kR of non absorbed
H-Lya
UV observables => adressed questions
* Full brightness of H2 and H-Lya => Sources regions, dynamics
* Full power radiated by H2 and H-Lya => Energy budget
* Auroral precipitated power => Energy budget
retrieved from the full brightness of H2 Lyman, Werner and continuum emission + canonical
conversion factor of 10kR/mW.m-2
* Energy of precipitating electrons => Energy budget
retrieved from CH4 absorption (see Gustin et al., 2013) and inferred from brightness ratios
Sources regions and dynamics
* Source regions :
1- main oval
2- polar emissions
3- equatorward
emissions
Sources regions and dynamics
-2
(a)
Frequency (kHz)
1000
-1
W.m. Hz
-19
10
-20
10
-21
10
-22
10
-23
10
-24
10
S
100
* Dynamics :
1- UV active region corotating
at the southern SKR phase
2- Individual hot spots in subcorotation
S
10
24
kR
(b)
10
18
LT (hours)
(c)
20
0
H2
visible SKR
12
LTsc
kR
S
6
3
visible SKR
2
1
0
24
0
H
-2
(d)
-1
1.5
(e)
(e)
1.0
0.5
LT (hours)
18
+
H3
0.0
12
-2 -1
cm .s. sr
6
60
0
H
27.7
27.8
27.9
28.0
DOY 2009
28.1
+
0
27.7
27.8
27.9
28.0
DOY 2009
28.1
Energy budget
-30°
-50°
* Energy of primary e- :
a1
a2
a3
a4
a5
a6
a7
b1
b2
b3
b4
b5
b6
b7
c1
c2
c3
c4
c5
c6
c7
from CH4 absorption
A
d2
d1
d3
d4
d5
d6
d7
30
kR H2
3
e2
e1
- E(e-) >10keV and <20keV
- Highest energies found along
the corotating active region
0.3
-2
1.4e16 / 6.4e19 cm
15 keV
-2
n(CH4) / n(H2) ~
-2
3.4e16 / 1.0e20 cm
<E(e-)> ~ 20 keV
4.2e16 / 1.1e20 cm
21 keV
a1
cm
cm
cm
cm
cm
a21.7e1616/ 6.5e19
a37.1e1512/ 4.3e19
a49.7e1513/ 4.8e19
a55.8e1512/ 3.9e19
a64.7e1511/ 3.5e19
a7
keV
keV
keV
keV
keV
b1
b2
b3
b4
b5
b6
c1
c2
c3
c4
c5
c6
-2
7.7e15 / 4.5e19 cm
13 keV
-2
-2
-2
-2
2.1e16 / 4.4e19 cm
13 keV
d2
d1
-2
d3
-2
1.6e16 / 5.9e19 cm
15 keV
1.1e16 / 5.0e19 cm
13 keV
d4
3
2
e1
-2
-2
cm
e21.9e1614/ 5.5e19
keV
1
Absorption
d5
d6
-2
5.5e15 / 3.2e19
11 keV
b7
c7
-2
3.2e16 / 5.7e19 cm
14 keV
-2
d7
Energy budget
b- H L
a- H Ly contribution to total H2 emission
- the brightness ratio H-Lya/H2
varies with the brightness of H2
(taken as a proxy of Pray)
- very sensitive for low
brightnesses < 10kR
=> new diagnosis of E(e-)
at energies <10keV ?
Brightness ratio
from H-Lya/H2 brightness ratios
1.0
0.4
0.8
Brightness ratio
* Energy of primary e- :
0.5
0.3
0.2
0.6
0.4
0.1
0.2
0.0
0
0.0
0
20
40
60
Brightness of total H2 emission (kR)
80
Energy budget
Precipitated power
Log Power (W)
12
H3+ power
H2+H-Lya power
10
8
6
27.0
SKR power
27.5
* First full auroral energy budget :
28.0
DOY
28.5
More details in the submitted paper
(revised version in review)
Contact : laurent.lamy@obspm.fr