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.

2

A

= k

q(a,

f) (B

V) (

n V

2 )1/3 ~

B V

2

3

4

IH

V =

sum

of u

nsig

ned

diffe

renc

es b

etw

een

7 ho

urly

mea

ns c

ente

red

at m

idni

ght

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)

12

Po

lar C

ap C

urre

nt S

heet

13

Kin

gua

Fjor

d 18

82-1

883

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