Variation of geomagnetic responses to the solar wind input · Variation of geomagnetic responses to...

Kiruna Sweden

M. Yamauchi Kiruna, Sweden 1

Variation of geomagnetic responses to the solar wind input:

Long-term change, Half-year increase during declining phases,

and 2009 specialty at fixed latitudes

M.YamauchiandB.OlsthoornIRF,Kiruna,Sweden

Acknowledgement:Dst,Kp,AL,SYM/ASY,PCandsunspotnumbers(RI)areprovidedbyWorldDataCenterforGeomagneMsm,KyotoUniversity,Japan,GFZ,Adolf-Schmidt-ObservatoryNiemegk,Germany,andtheRoyalObservatoryofBelgium,Brussels.Includingtheseindices,alldataareobtainedfromNASA-GSFC/SPDFthroughOMNIWeb(hUp://omniweb.gsfc.nasa.gov/ow.html).

Kiruna Sweden


Motivation

(1) Longterm(50years)changeinAEresponsetosolarwindcondi@on(hourlyvalue),whichcannotbeexplainedbydifferenceinrecenthistoryofac@vity(solarcyclephase).

(2) Studyof2009singularitysuggestedla@tudinal-shiKofionosphericcurrent.

(3) Auroraloca@onduringgrowthphaseseemstomovednorthaKer2006.

(4) Magne@cNorthPoleisquicklyactuallymovingnorth,thatmightshiKthe“substan@al”AEla@tude

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Implication to Space Weather Forecast

(1)forLongTrend

Possibility1:DuetoshiKoftheauroralovalloca@on⇒ High-riskla@tudeforhazardousgroundcurrentsmaychangePossibility2:Actualchangeintheenergycouplingefficiency⇒ Predic@onmustberenewedeverysolarcycle

(2)forSolarCyclePhaseDifference

Thesepossiblecauses(1&2)couldalsobealsophase-dependent⇒ Riskofhazardcanalsobephase-dependent

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Consequence of shift of

auroral latitude

SYM, ASY AL, AU PC

aurorainside AE station

no change in ASY-D

�D��QRPLQDO�ORFDWLRQ��DXURUD�a�¨%�

(b) equatoward shift

larger ASY-Dno change in AU, AL

(c) equatoward expansion

Location of active aurora

larger PCsmaller ALno change in AU

no change in PC

SYM, ASY AL, AU PC

SYM, ASY AL, AU PC

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AEcannotbeusedforSun-Earthcouplingefficiency?

Shift of auroral latitude ⇒

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AEcannotbeusedforSun-Earthcouplingefficiency?AEcanbeusedtomonitortheauroralloca@onbycombiningwithASY_DandPC

⇒ High-risklaMtudeforhazardousgroundcurrentmaychange

Shift of auroral latitude ⇒

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Method • Using 5-min NASA/OMNI solar wind data, we calculate

ε' = (4π/µ0)·VBtan2sin4(θC/2), and dΦ/dt = (V2

SW·Btan·sin4(θc/2))2/3

• Obtain average AE, PC, and SYM/ASY for given ε’ and dΦ/dt

• Travel time the spacecraft to the Earth is considered.

• Different “integrated inputs” (5-60 min before) are compared ⇒ the correlation is best for 60 min average.

• Average the result every 3-month to separate "equinox” and solstice.

• Compare with 3-months variation of ε’ and dΦ/dt to remove anomaly due to “pre-condition” difference.

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Why not

• Why not examine meridian chain (IMAGE, Greenland etc)? ⇒ 1. Future work.

2. We want to show that indices are useful for this purpose. • Why not to use ”wide latitudinal-range” indices such as ap? ⇒ 1. Purpose is different.

2. We want to show that AE is useful for this purpose.

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AL [n

T]-10

-20-30-50

-100

-300Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

2009 minimum

Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

RI

200

100

0

Sunspot Numbers (RI, 3-month averaged)

10-30 W/km2 3-10 W/km2 < 3 W/km2 30-100 W/km2

Akasofu ¡' vs AL (equinox)

(1)  Enhancementof~0.5-yearduringdecliningphase?(2)  Long-termdecreasingtrendwith2009minimum?

Result / overview of “AL response”

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Dueto“pre-condi@on”difference?

CauseoflaMtudinalshibofAurora

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< 30 W/km2 < 10 W/km2 < 3 W/km2

< 100 W/km2 < 300 W/km2

Occurrence frequency of different solar wind input

(a) Akasofu ¡' (3-month average of 5-min values)

(b) Newell d\/dt (3-month average of 5-min values)

100%

80%

60%

40%

20%

0%

< 4.5 V2/3s-2/3

< 100 V2/3s-2/3 < 45 V2/3s-2/3 < 21 V2/3s-2/3 < 10 V2/3s-2/3

Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

100%

80%

60%

40%

20%

0%

freq

uen

cy

freq

uen

cy

The singular period does not match with the declining phase peak of solar wind input

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Dueto“pre-condi@on”difference? Notrelatedto“pre-condi@on”(mostlikely)

CauseoflaMtudinalshibofAurora

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Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

200

100

50

3020

AU [n

T]2009 minimum(a) AU (around equinoxes)

1980 1984 1988 1992 1996 2000 2004 2008 2012 20162

1

0.5

0.30.2

2009 minimum

PC in

dex

d\/dt=21-45 [V2/3s-2/3] d\/dt=4.5-10 [V2/3s-2/3]

(b) PC (around equinoxes)

@ higher latitude (similar)

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2009 minimum3020

10AS

Y-D

[nT] (c) ASY-D (around equinoxes)

-2-3

SY

M-H

[nT]

(d) SYM-H (around equinoxes)1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

-5

-10

-30 2009 minimum

d\/dt=21-45 [V2/3s-2/3] d\/dt=4.5-10 [V2/3s-2/3]

@ lower latitude (different)

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Valid range of ε’ and dΦ/dt ? 0

-200

-400

-600

-800

4x105

2x105

0 sam

ples

AL (5

-min

value

s) [n

T]

10 102 103

AL responses to solar wind input at different solar cycle phases(SW input: 1 hr average of 5-min ¡' & d\/dt values, with 1 hr delay)modified Akasofu’s ¡'Akasofu

4x105

2x105

0 sam

ples

Newell’s flux d\/dtNewell 0

-200

-400

-600

-800

10 102 103 10 102

1.6

1.4

1.2

1.0

0.8ratio

(AL ph

ase/A

L all)

¡' [W/km2] d\/dt [(V/s)2/3]

1.6

1.4

1.2

1.0

0.8

(b) (a)

(d) (c)

(f) (e)

post maximuminclining-maximum late decliningsingular period

AL values AL values

relative AL values

AL (5

-min

value

s) [n

T]ra

tio (A

L phas

e/AL all

) relative AL values

10 102 103

# of samples # of samples10 102

10 102

ε’ dΦ/dt

(1) Phase difference

•  divide into 4 phases

•  take relative

values against average

Result: 50% more

•  weak-moderate conditions

•  not storm time

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Result: PC/AU are similar SYM-H is unclear, ASY-D not at all

(a)

1.4

1.2

1.0

0.8

(c)

rati

o o

f A

SY

-D

relative ASY-D values

1.6

1.4

1.2

1.0

0.8

(b)

rati

o o

f A

U

relative AU values

post maximuminclining-maximum

1.6

1.4

1.2

1.0

0.8

rati

o o

f P

C

relative PC values

d\/dt [(V/s)2/3]

1.4

1.2

1.0

0.8

(d)

rati

o o

f S

YM

-H

relative SYM-H values

Indices (relative changes) vs Newell’s flux d\/dt

10 102

10 102 10 102

10 102

d\/dt [(V/s)2/3]

post maximum

inclining-maximum

late declining

singular period

@ higher/lower latitudes

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•  divide into different cylcles (#21 and #24 are not complete, though) •  take relative values against average

Result: decreasing trend over 4 cycles

ε’ dΦ/dt

(2) Long-term (cycle-to-cycle) trend

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Result: AU/SYM-H are similar PC similar only clycle #24, ASY-D not at all

@ higher/lower latitudes

1.2

1.0

0.8

1.2

1.0

0.8

1.4

1.2

1.0

0.8

1.4

1.2

1.0

0.8

(b)

(a)

rati

o o

f P

C

(c)

rati

o o

f A

SY

-D

(d)

rati

o o

f S

YM

-Hra

tio

of A

U

relative PC values

relative ASY-D valuesrelative SYM-H values

relative AU values

d\/dt [(V/s)2/3]

cycle #21 cycle #22 cycle #23 cycle #24

10 102 10 102

10 102 10 102

d\/dt [(V/s)2/3]

Indices (relative changes) vs Newell’s flux d\/dt

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Interpreting by latitudinal shift of quiet-time

aurora SYM, ASY AL, AU PC

aurora

SYM, ASY AL, AU PC

outside AE station

larger AU, AL, PCno change in ASY-D

(a) nominal location / solar minimun

(b) equatoward shift / singular period

SYM, ASY AL, AU PC

auroralarger ASY-Dno change in AU, AL, PC

(c) equatoward expansion / solar max.

Location of quiet-time aurora

aurora

singularperiod=returningtoAEsta@ons

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(1) For quiet to moderate solar wind input (|AL| < 400 nT activity on average), the AL, AU, and PC responses to the same solar wind input increased for about 3-12 months during 1983, 1994, 2003, and 2016, immediately-after the early declining-phase massive CME period. Some increase for SYM-H, but not for ASY-D (enhance rather post-maximum). ⇒ Consistent with equatorward shift of the quiet-time polar cap and most likely not related to the pre-condition difference. (2) AL and AU responses to the same solar wind input continuously decreased over 30 years (at least until 2009).

Futurework:(1)  Sameanalysesusingmeridianchain(IMAGE,Greenland)midnight

data?(2)  IdenMfyaurorallocaMonusingall-skycameranetwork

Summary

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End / extra slides

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Result / overview (why we take equinox)

sameresultfordΦ/dtasε'sols@ce:moreAE/SYMstaMonsinthenorthernhemisphere

AL [n

T]-10

-20-30-50

-100

-300Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

equinox

AL [n

T]

-10

-20-30-50

-100

-300Year: 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

solstice

2009 minimum

2009 minimum

< 4.5 V2/3s-2/3 21-45 V2/3s-2/3 10-21 V2/3s-2/3 4.5-10 V2/3s-2/3

Newell’s d\/dt vs AL

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Result: smaller during 2005-2014 (x ~ cycle #24) than before (Yamauchi, 2015)

Kp#24/Kp#20-23 [nPa] [µV/m]

AL#24/AL#20-23 (Dst#24-5nT)/(Dst#20-23-5nT)

d\/dtNewell (a) (c) (d)PSW Ey

-3 -2 -1 0 1 2 30 2 4 6 810 102 103 104

10% error range10% error range10% error range

[(mV/s)2/3]

Relative values of 2005-2014 to 1965-20041.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

(b)

[cm-3] 0 5 10 15 20

NP1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

10% error range

ap#24/ap#20-23

Sameforhourlyvalue(since1965)

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no change in ASY-D

(e) poleward shift

(f) equatoward expansion

Quiet-time aurora ?

aurora�G��QRPLQDO�ORFDWLRQ��DXURUD�a�¨%�inside AE station

SYM, ASY AL, AU PC

SYM, ASY AL, AU PC

smaller PC, AL, AU

SYM, ASY AL, AU PC

larger ASY-Dno change in AU, AL

no change in PC

Consequence of shift of

Quiet-time auroral latitude

singularyear=returningto(d)from(e)

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Variation of geomagnetic responses to the solar wind input · Variation of geomagnetic responses to...

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