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

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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

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0

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3012 MLT

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north

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3012 MLT

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south

Eastward and westward auroral electrojets

Northern and Southern hemisphere

12 mlt

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Kp: 0-1+

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Kp: 1+- 2

12 mlt

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Kp: 2+- 3

12 mlt

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Kp: 3+- 4

12 mlt

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Kp: 4+- 5

12 mlt

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Kp: 5- 6

12 mlt

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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

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70

80

90

Inv.lat.

820 825 830 835 840 845 8500

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1000

1500

-AL (

nT

)

820 825 830 835 840 845 8500

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AU

(nT

)

CHAMP

2004

April 2002

820 825 830 835 840 845 85050

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85

Inv.

Lat.

820 825 830 835 840 845 8500

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Daynumber 2000

MLT

CHAMP

DMSP

820 825 830 835 840 845 85050

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85

Inv.

Lat.

820 825 830 835 840 845 8500

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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

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75

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85

Inv.L

at.

830 832 834 836 838 840 842 844 846 848 8500

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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

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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

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-4

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nT

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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

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0

100Sa

tellit

e "D

st" (

nT)

830 832 834 836 838 840 842 844 846 848 8500

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Daynumber 2000

MLT

(hou

rs)

Oersted

CHAMP

SACC

Dst

Automatic b2e detection fail

IMF By dependence

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IMF By>2, Bz<-2, north

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IMF By>2, Bz<-2, south

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IMF By<-2, Bz<-2, north

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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