A tool for improved space weather predictions:the CME expansion speed.

Max-Planck-Institut für AeronomieKatlenburg-LindauGermany

Instituto Nacional de Pesquisas EspaciaisSao Jose dos Campos - SPBrazil

A. Dal Lago, R. Schwenn

Sept. , 2001

Space Weather

Geophysical Research Letters / 15 July 1998

Space Weather

Shock

Space Weather

-100

-50

0

Dst

(n

T)

0,00,10,20,30,4 static pressure

plus. rel. dyn. pressure

300

400

500

600

21201918

Oct., 1995

P (

nP

a)

V (

km/s

)N

(cm

-3)

T (

K)

Bz

(nT

)B

(n

T)

0204060

01x1052x1053x1054x1055x105

-20-10

01020

0

10

20

30

CLOUD

Shock

Sun:EIT / CME

Earth:geomagnetic storm

L1:shock - sheath - magnetic cloud

Coronal Mass Ejections - CME

Limb

Halo

LASCO C2 LASCO C3EIT 195 LASCO C2 LASCO C3EIT 195

Coronal Mass Ejections - CME

Limb CME

Halo CME

LASCO C2 LASCO C3

Acceleration/Deceleration of CMEsSept. 28, 1997

LASCO C2

Acceleration/Deceleration of CMEsSept. 28, 1997

LASCO C3

Acceleration/Deceleration of CMEsS85W

Acceleration/Deceleration of CMEsJuly 25, 1999

S85W

S75ES85E S70W S55W

LASCO C3

Halo CMEs from Jan. 1997 to Apr. 2001

Halo CMEs seen at the suntotal full partial

Front side 157 81 76Back side 41* 26* 15*Limb 23 4 19Not clear** 59 4 55total 280 115 165

* not all included** no (no unique) disk information available

Halo CMEs and Interplanetary association

Sun:EIT / CME

Earth:geomagnetic storm

L1:shock - sheath - magnetic cloud

Halo CME and Interplanetary associationtotal Clear IP

association*Possible IPassociation**

No IPassociation

full 81 50 27 4Front sidepartial 76 42 15 19full 4 3 0 1Limbpartial 19 7 6 6

totals 180 102 48 30* unique and clear CME-Interplanetary association** CME-Interplanetary association is not unique or not sure, but not discarded

Interplanetary signatures and CME association

Sun:EIT / CME

Earth:geomagnetic storm

L1:shock - sheath - magnetic cloud

Interplanetary signatures and its possible causestotal Clear

associationwith CME

Possibleassociationwith CME

Associationwith CIR

No association

Cloud or blob 35 15 19 0 1shock 148 87 47 2 12other 6 - - 6 -

Halo CMEs and geomagnetic storms

Sun:EIT / CME

Earth:geomagnetic storm

L1:shock - sheath - magnetic cloud

Intensity of the storm (Dst) total Caused by CIR Related to CMEs Not related-50 > Dst > -100 nT 84 6 74 4-100 > Dst > -200 nT 32 2 29 1 (Oct 28th 2000)Dst < -200 nT 8 0 8 0

CME expansion speed

Vexp

Vexp VexpVrad

Vpr Vpr

LASCO C3 LASCO C3 LASCO C3

Vexp

Vrad

Limb CMEs

57 events from 1997 to 2001Criterion: EIT 195 activity closeto the limb (maximum 30 deg.).

0 500 1000 1500 2000200

400

600

800

1000

1200

1400

1600

1800

2000 less than 40 deg. between 40 and 80 deg. more than 80 deg.

29.08.0157 limb events from 1997 to 2001 (not all!)

linear fit: Vr = 0.87919973 * VexpR = 0.85581399 ; SD = 132.94159

expansion speed (km/s)

radi

al s

peed

(km

/s)

Halo CMEs

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

140

front side halos limb CMEs

10.09.200194 measured points, 102 total, unique CME-IP association

trav

el ti

me

(h)

halo expansion speed (km/s)

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

14095 events, 102 total, unique CME-IP association

trav

el t

ime

(h)

halo front speed (km/s)

Frontal speed x travel time Expansion speed x travel time

Vexp

VprVfr

Halo CMEs

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

140

94 measured points, 102 total, unique CME-IP associationcurve fit: t = -22.75*ln(Vexp) + 220.8R = -0.62 ; SD = 14.61

limb events

03.09.2001

trav

el t

ime

(h)

halo expansion speed (km/s)0 500 1000 1500 2000 2500 3000 3500

0

20

40

60

80

100

120

140

95 events, 102 total, unique CME-IP associationcurve fit: t = -17.85*ln(Vfr) + 181.71R = -0.47 ; SD = 16.21

trav

el t

ime

(h)

halo front speed (km/s)

Frontal speed x travel time Expansion speed x travel time

Vexp

VprVfr

Full halos only

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

140 full halos only travel time at constant speed fitted curve dv/vt = -A*v

03.09.2001

53 measured points, 54 total, unique full halo-IP associationcurve fit: t = -22.85*ln(Vexp)+220.2R = -0.65, SD = 13.0

trav

el ti

me

(h)

halo expansion speed (km/s)

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

140 full halos only travel time at constant speed fitted curve dv/vt = -A*v

03.09.2001

53 measured points, 54 total, unique full halo-IP associationcurve fit: t = -22.85*ln(Vexp)+220.2R = -0.65, SD = 13.0

trav

el t

ime

(h)

halo expansion speed (km/s)

Ago. 25th 2001

Ago. 25th 2001

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

140 full halos only travel time at constant speed fitted curve dv/vt = -A*v

03.09.2001

53 measured points, 54 total, unique full halo-IP associationcurve fit: t = -22.85*ln(Vexp)+220.2R = -0.65, SD = 13.0

tra

vel t

ime

(h)

halo expansion speed (km/s)

Ago. 25th 2001

LASCO C2 LASCO C3EIT 195

Solwind CMEs and Helios 1

Solwind coronagraph

Helios 1+ 32 degr.

Period: 1979 - 198256 events - 45 where Vcme and Vip were possible to be obtained.

0 500 1000 1500 2000 2500 3000 35000

20

40

60

80

100

120

140

94 measured points, 102 total, unique CME-IP associationcurve fit: t = -22.75*ln(Vexp) + 220.8R = -0.62 ; SD = 14.61

limb events Helios CMEs

05.09.2001

trav

el ti

me

(h)

halo expansion speed (km/s)

Solwind and Helios 1

Vexp

Vcme

Helios1

•Solwind: Vcme Vexp•Solwind + Helios: travel time - avg. propagation speed - travel time to 1 AU

1 AU

Expansion speed x shock speed at 1AU

0 500 1000 1500 2000 2500 3000 3500

300

400

500

600

700

800

900

1000

80 measured points, 88 total, unique halo-shock association

03.09.2001

sh

ock

sp

ee

d (

km/s

)

halo expansion speed (km/s)

200 400 600 800 1000 1200 1400 1600200

300

400

500

600

700

800

900

1000

1100

limb events

88 measured points, ?? total, unique halo-shock associationlin fit: Vsh = 0.43*Vpr + 254.97R = 0.67, SD = 106.02 03.09.2001

shoc

k sp

eed

(km

/s)

propagation speed (km/s)

Propagation speed x shock speed at 1AU

Conclusions

• Limb CMEs show a linear relation between Vexp and Vrad• There is a good correlation found between the expansion speed (Vexp) of halo CMEs and the travel time to 1 AU.• The halo expansion speed (Vexp) can now be used to predict thetravel time of CMEs.• There is still substantial uncertainty, indicating that processes occurring during the “trip” of the CMEs from the sun to 1 AU may play an important whole.• 4 out of 81 full front side halo CMEs never reachead the earth - false alarms!• 12 out of 146 transient IP shocks were not related to any CME - prediction missed!• 1 out of 30 intense storms and 4 out of 78 moderate stormswere not related to any CME - storm prediction missed!• All very intense (Dst<-200 nT) were related to halo CMEs.