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