Monitoring of auroral oval location and geomagnetic activity based on
magnetic measurements from satellites in low Earth orbit.
S. Vennerstrom Technical University of Denmark, Denmark (DTU)
SOTERIA collaboration
Auroral oval location – why bother?• Ground Induced Currents (auroral electrojets)• Communication problems• Increased radiation dose in LEO (energetic electrons)• Correlated with cut-off latitude of SEPs
NOAA - POESParticle precipitation
SSA
?
SSA Magnetic field?
2004
Current low altitude, polar orbiting, high precision magnetic field missions
Ørsted 2/SAC C2000-2004
Ørsted1999 - ?
CHAMP2000 -2010
These data can be used to derive electrojet location during passage
2004
Method –CHAMP passing the polar regionBabs (residual) (blue), Babs/Δx (red)
0 500 1000 1500 20000
100
200
300
400
500
600
4321 477.02 12.4
4322 477.09 4323 477.15 4324 477.22 4325 477.28 4326 477.35 4327 477.41 4328 477.47 4329 477.54 4330 477.60 4331 477.67 4332 477.73 4333 477.80 4334 477.86 4335 477.93 4336 477.99 4337 478.06 4338 478.12 4339 478.18 4340 478.25 4341 478.32 4342 478.38 4343 478.45 4344 478.51 4345 478.57 4346 478.64 4347 478.70 4348 478.76 4349 478.83 4350 478.89 4351 478.96
4321 477.02 11.4
4322 477.09 4323 477.15 4324 477.21 4325 477.28 4326 477.34 4327 477.41 4328 477.47 4329 477.54 4330 477.60 4331 477.67 4332 477.73 4333 477.80 4334 477.86 4335 477.93 4336 477.99 4337 478.06 4338 478.12 4339 478.19 4340 478.25 4341 478.32 4342 478.38 4343 478.45 4344 478.51 4345 478.58 4346 478.64 4347 478.70 4348 478.77 4349 478.83 4350 478.90 4351 478.97
-20 0 20
-30
-20
-10
0
10
20
3012 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
north
-20 0 20
-30
-20
-10
0
10
20
3012 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
south
Eastward and westward auroral electrojets
Northern and Southern hemisphere
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 0-1+
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 1+- 2
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 2+- 3
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 3+- 4
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 4+- 5
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 5- 6
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
12 mlt
618
70
50
Kp: 6+- 9
Electrojet position and intensity statistical Kp dependance
2004
Comparison to ABI and AL
1663 1664 1665 1666 1667 1668 1669 1670 1671 167250
60
70
80
90
Inv.
lat.
1663 1664 1665 1666 1667 1668 1669 1670 1671 16720
500
1000
1500
Daynumber 2000
-AL
(nT
)1663 1664 1665 1666 1667 1668 1669 1670 1671 1672
-200
-100
0
100
Dst
(nT
)
CHAMP
Dst
AL
latitude
2004
Comparison to AU and AL
820 825 830 835 840 845 85050
60
70
80
90
Inv.lat.
820 825 830 835 840 845 8500
500
1000
1500
-AL (
nT
)
820 825 830 835 840 845 8500
200
400
600
AU
(nT
)
CHAMP
2004
April 2002
820 825 830 835 840 845 85050
55
60
65
70
75
80
85
Inv.
Lat.
820 825 830 835 840 845 8500
5
10
15
20
Daynumber 2000
MLT
CHAMP
DMSP
820 825 830 835 840 845 85050
55
60
65
70
75
80
85
Inv.
Lat.
820 825 830 835 840 845 8500
5
10
15
20
Daynumber 2000
MLT
CHAMP
DMSP
Boundary: b2e
Boundary b2e: Maximum average energy of precipitating electrons
830 832 834 836 838 840 842 844 846 848 85055
60
65
70
75
80
85
Inv.L
at.
830 832 834 836 838 840 842 844 846 848 8500
5
10
15
20
Daynumber 2000
MLT
Comparison to acceleration boundaries (discrete aurora)
Boundary b3a and b3b: Poleward and equatorward boundary of acceleration events
Boundaries: b3a and b3b
2004
Close association even in details!
Small changes from one orbit to the next are not noise!
2004
Dst - observed from satellite
610 620 630 640 650 660 670 680 690 700 710
-400
-300
-200
-100
0
100
Julian Day 2000
Dst (
nT)
groundbased Dstsatellite Dst
0 6 12 18 240.75
0.8
0.85
0.9
0.95
MLT
corre
latio
n co
effic
ient
Summary• Satellite magnetic field intensity measurements in polar low
Earth orbit can be very useful for space weather monitoring• The latitude of the auroral electrojets is well determined by
the satellite B-field intensity data. It coincides with the b2e electron precipitation boundary (max electron energy), and the equatorward boundary of the discrete auroral precipitation.
• The magnetic data can provide a measure of electrojet intensity well correlated with AL and AU and a measure of the ring current intensity well correlated with Dst
Extras
The Swarm mission
Constellation• 3 satellites:
A+B: 2 side-by-side in low orbit, =1.5°
C: 1 in higher orbit
• A+B staying together• A+B and C Slowly drifting apart in LT
Based on Swarm we can create a European counterpart to the US auroral oval monitoring
Measurement requirements
100 200 300 400 500 600 700 800 900 1000-6
-4
-2
0
2
4
6
8
10
nT
0 200 400 600 800 1000 1200 1400 1600 1800 20000
50
100
150
200
250
11376 478.07
2.6
11377 478.14
11378 478.21
11379 478.28
11380 478.35
11381 478.42
11382 478.49
11383 478.56
11384 478.63
11385 478.70
11386 478.77
11387 478.84
11388 478.91
11389 478.98
11376 478.07
2.6
11377 478.14
11378 478.21
11379 478.28
11380 478.35
11381 478.42
11382 478.49
11383 478.56
11384 478.63
11385 478.70
11386 478.77
11387 478.84
11388 478.91Auroral electrojet location:Accuracy: 1 nT?Blå kurve: Forstyrrelse af BabsGrøn: dBabs/dlatRød: dBabs/dlat filtreret=max viserpositionen af electrojet’en
Satellite: low lat. ΔB
830 832 834 836 838 840 842 844 846 848 850-300
-200
-100
0
100Sa
tellit
e "D
st" (
nT)
830 832 834 836 838 840 842 844 846 848 8500
5
10
15
20
Daynumber 2000
MLT
(hou
rs)
Oersted
CHAMP
SACC
Dst
Automatic b2e detection fail
IMF By dependence
-20 0 20
-30
-20
-10
0
10
20
3012 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
IMF By>2, Bz<-2, north
-20 0 20
-30
-20
-10
0
10
20
3012 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
IMF By>2, Bz<-2, south
-20 0 20
-30
-20
-10
0
10
20
3012 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
IMF By<-2, Bz<-2, north
-20 0 20
-30
-20
-10
0
10
20
3012 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
12 MLT
61880
70
IMF By<-2, Bz<-2, south
Magnetic disturbances - Two approaches
• Using B-field vector-data:– Inversion of high latitude electrodynamic parameters: FAC
strength and location, polar cap potential, Joule heating– Requires continous data (CHAMP, some Ørsted events)+ E-
field or conductance (Swarm)
• Using only data on B-field intensity– Estimate location and intensity of ionospheric electrojets– Continous data from at least 3 satellites available (less
challenging for future missions)
This presentation
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