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1
How
we
dete
rmin
e so
lar
win
d pa
ram
eter
s fo
r th
e pa
st 1
50 y
ears
.
L. S
valg
aard
Ea
sy T
oolk
it, In
c.
6927
Law
ler R
idge
, Hou
ston
, TX
770
55, U
SA.
(leif@
leif.
org)
A
bstr
act
The
sola
r w
ind
and
its e
mbe
dded
inte
rpla
neta
ry m
agne
tic f
ield
(IM
F) b
uffe
t the
Ear
th's
mag
neto
sphe
re r
esul
ting
in
cont
inuo
us g
eom
agne
tic a
ctiv
ity, w
axin
g an
d w
anin
g w
ith t
he c
hang
ing
win
d. T
he v
ery
com
plex
phe
nom
enon
of
geom
agne
tic a
ctiv
ity is
des
crib
ed b
y "g
eom
agne
tic in
dice
s". D
iffer
ent i
ndic
es re
spon
d w
ith d
iffer
ent s
ensi
tiviti
es to
di
ffere
nt p
aram
eter
s of
the
sola
r w
ind;
som
e ar
e m
ost s
ensi
tive
to c
hang
es in
the
mag
netic
fie
ld, B
; som
e ar
e m
ore
sens
itive
to th
e so
lar w
ind
spee
d, V
. By
expl
oitin
g th
ese
diffe
rent
dep
ende
ncie
s w
e ca
n de
term
ine
both
B a
nd V
and
th
eir
poss
ible
long
-term
tren
ds. I
n pa
rticu
lar
we
find
that
at a
t eac
h so
lar
min
imum
B r
etur
ns to
an
alm
ost c
onst
ant
"flo
or"
valu
e of
~4.
5 nT
, im
plyi
ng th
at th
ere
is no
secu
lar t
rend
in th
e st
reng
th o
f the
IMF.
5
10100
1000
-90
-75
-60
-45
-30
-15
015
3045
6075
90
Co
rre
cte
d G
eo
ma
gn
eti
c L
ati
tud
e
IHV (log-scale)
NS
<IH
V>
199
6-20
03
020406080
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
IHV
IHV
15N
NG
K-F
UR
-WN
G-W
IT-R
SV
-CLF
-HA
D
6
BV
o2 =
4.3
4 (
IHV
- 6
.5)
R2 =
0.7
6
0
10
0
20
0
30
0
40
0
02
04
06
08
01
00
IHV
BV
o2
Ro
tati
on
Me
an
s
050100
150
200
250 19
6519
7019
7519
8019
8519
9019
9520
0020
0
BVo2 (I
HV)
BVo2 (O
bs)
R-C
Effe
ct
7
NH P
ower
(GW
) = 0
.680
7 IH
VR2 =
0.8
582
010203040506070
020
4060
8010
0
1978
-200
6
0102030405060
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
PO
ES (G
W) N
our
cal
ibra
tion
0.68
* IH
V N
Hem
isph
eric
Pow
er In
put (
PO
ES) a
nd IH
V G
eom
agne
tic A
ctiv
ity
8
ID
V =
Ave
rage
uns
igne
d di
ffere
nce
betw
een
the
mid
nigh
t hou
rly m
eans
from
one
day
to th
e ne
xt.
024681012141618
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
10u
IDV
(H)
Yea
rly a
vera
ges
B =
0.46
IDV
+ 2.
09R2 =
0.8
7
V/10
0 =
0.03
IDV
+ 4.
14R2 =
0.0
4
B =
0.38
IDV
+ 2.
78R2 =
0.7
9
R2 = 0
.87
024681012
05
1015
20
1965
-200
6
IDV
012345678910
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
012345678910
B st
d.de
v
Cove
rage
100%
=>
B ob
sB
calc
from
IDV
B ob
s m
edia
n
9
ID
V is
clo
sely
rela
ted
to n
egat
ive
valu
es o
f Dst
: J.
Love
has
cal
cula
ted
Dst
bac
k to
190
5.
IDV
= -0
.40
Dst
(<0)
+ 2
.85
R2 = 0
.89
024681012141618
-40
-30
-20
-10
0
1905
-200
4
IDV
Dst
(<0)
Year
ly a
vera
ges
024681012141618
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
1909
IDV
IDV
cal
c. fr
om D
st(<
0)
10
024681012
1870
1890
1910
1930
1950
1970
1990
2010
B n
T
Yea
r
IMF
B in
ferre
d fro
m ID
V
B =
0.4
45 ID
V +
2.21
R2 =
0.8
9
012345678910
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
B n
T
B =
2.78
+ 0
.38
IDV
B =
3.93
- 0.
1546
(Dst
<0)
B IM
F ob
s
IMF
B in
ferr
ed fr
om ID
V an
d Ds
t
11
B =
0.28
82 s
qrt(R
z) +
4.4
856
R2 = 0
.713
9
012345678910
05
1015
B nT
sqrt(
Rz)
1872
-200
6
012345678910
1830
1840
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Infe
rred
IMF
B s
ince
183
6B
nT
Year
From
Bar
tels
u-m
easu
reIM
F B
obs
S/C
From
IDV
From
sqr
t(Rz)
14
-80
-60
-40
-20020406080100
-100
-80
-60
-40
-20
020
4060
80
BLC
CB
B
ALE
RES
THL
Vect
or V
aria
tion
of H
oriz
onta
l Com
pone
nts
1980
-200
4
15
VB
= 5
0.14
6 R
ES
R2 =
0.8
594
VB
= 5
0.59
7 TH
LR
2 = 0
.885
6
0
1000
2000
3000
4000
5000
020
4060
8010
0
Ampl
itude
(nT)
VB (k
m/s
* nT
)
1965
-200
4
0
1000
2000
3000
4000
5000
1965
1970
1975
1980
1985
1990
1995
2000
2005
VB
(km
/s *
nT
)
Ob
serv
ed
S/C
RE
S (
Re
solu
te B
ay)
TH
L (
Th
ule
)
16
012345678910
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
B fr
om ID
V
V o fr
om IH
VO
bser
ved
in s
itu
01020304050
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
BV o
cal
c. fr
om ID
V an
d IH
V
BV o
cal
c. fr
om P
olar
Cap
B
V o o
bser
ved
17
Th
e Fl
oor i
n IM
F B
02468101214
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
IMF
B In
ferr
ed fr
om ID
V-In
dex
(Rot
atio
n Av
g.)
B o
bsB
= 1
.67
IDV
0.6
nT
Floo
r
01234567 1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Sola
r Win
d Sp
eed
Infe
rred
from
IHV
and
IDV
V o 1
00 k
m/s
V o o
bsV o
= 1
.6 [(
IHV
- 5) /
IDV
0.6] 1
/2