On the variability of Lyman-alpha with solar activity

Plum,. Printed

Spm SC,. Vol. 29. No. in Great Britain

8. pp. 907-914,

0032-0633/R,

19x1

/OSOYO7-OXSO2.00/0 Pcrgamon pre\s

I rd.

SHORT PAPER

ON

THE

VARIABILITY

OF

Lucien INSTITUT

LYMAN-ALPHA 1

BOSSY

ROYAL

and

WITH

Marcel

METEOROLOGIQUE, 1180

Received

ACTIVITY 2

NICOLET

3,

BRUSSELS,

SOLAR

avenue

Circulaire

Belgium

20

June

1981

ABSTRACT After

taking

sensitivity,

of

the

a critical

alpha, between

the

=

limitations

in

values

deduced

ce

for

a perfectly

re

has

been

The

sible is

for

same 150 in

order nm;

as

the

hence

numbers solar

usually

it

of

3

for

of

all

study

appropriate

to

of

Also

Institut

G.

Also

External

Geophysics,

of

the

of

on

the

nray be

of

the

of

are

much

can

be

made

the by

Lyman-alpha

rlnlversity University,

involving

than

better

of

Louvain,

Brussels.

co2 the

than

detail

and,

Since

those

a more of

and

2' of

less

in

study

of

0 is

activity.

to

in

respon1945)

of

than

the

Vidal-Yadjar

difficulties

the

atmosphe-

is

radiation

greater

to

the

wavelenqths

subject

made

that

(Nicolet,

solar

-1

D = 0.25.

of

characteristics

level

Lyman-alpha

Catholic Brussels

its

set

mean

radiation

this at

-2

relation

25%; the irradian-1 -2 cm set .

processes of

the

Lyman-

deviation

chemistry

radiation

examine

clearly

cm

ionosphere

intensity

solar

Reference

photons

this

in

the

cm:

i!?struments

fact,

the

available

irradiance

Lemaitre,

the

of

10.7

a standard

in

In

Lyman-alpha

data

illustrates the

nm)

The

dependence

irradiance

for

10

photodissociation

other

value

x

at 11

or

for

an

D region

1981).

the

flux

of

years.

the

strong

irradiance

+ accuracy of _ 11 photons + 0.5) x 10 -

(2.5

mesospheric (Nicolet,

solar

solar

and

(121.567

the

calibration,

expression

(F - 65)

have

several

of

analysis. the

is

Lyman-alpha

observations

critical of

expression Sun

radiations,

This absolute

is

its

observations

2

that

particular,

other

the

the

calibration

this

the

following

+ 0.011

absolute

quiet

H20

and

in

measure

the

R = 0.91

of

in

10

11

to

to

the

formation

especially

used

leads

x

changes

coefficient

recognised the

the

irradiance

2.5

from

role

important

and

instruments

Lyman-alpha

a correlation

The

account

analysis

I(Lyman-alpha) with

into

collected

(1977).

arriving

at

than

although,

25%

an

Louvain-la-Nerve.

908

ShortPaper

for + -

short-term

5%.

tion of

Thus of

the

the

the

1955

se

and x

10

in

in

of

activity.

irradiance

in

apart

the

OSO-1

decreased

ge

during

the

there The

of

of

solution

the is

Hinteregger

important

The

quence,

in

that

have

all

rockets

between

by

made

the

corrections of of

data

the the

be

an

which

(Tousey,

from

made

The 1963

provides

use,

chan-

and

satellite

of

be

no

1975. AE-E

Hinteregger, to

obtain

a The

Lyman-alpha.

instrument

can

neglected.

was

attempt

irradiance measuring

observations

observations

in

For

instrument

in

to

ac-

the

years.

there

authors in

assess

the

not

solar

calibration

of

1974

variations of

to

of

was

from

the

trying

that

made

; Vidal-Madjar

a number

1972,

about

increa-

observations

cycles

sensitivity to

an

absolute

of

observations

value

cannot

the

over

received

such

of

il-year

from to

clearly

instrument

differences

the

time

poses

using

rockets

explained

only

introduction

; Cook

et

another

a

by

into

al.,

the

1980)

approach

to

the

problem.

It

in

the

to make

of

determinawith

1975

more

the

the

the

considerations

of

by 20.

of

light

reach

variation

variation

numbers

sensitivity

sensitivity

which

theoretical account

of

increases

to

and

in

tables is

may the

attributed

ensuring

1969

when

absolute

the

bring

errors,

take

the in

from

years

it

are

by

the

problem

that

year

and

and of

instruments

decrease

b,

the

made

indicate

additional

the

per

Comparisons

1980)

systematic

we

of

greater

27-day

assumed

1.7

important

problem.

Cycle

a,

decrease

analysis

of

the

discussion

1980 how

(Rottman,

made

and

kind

; Vidal-Madjar,

1960)

the

of

10%

much 1873

difficulty

is

a further

estimate

long-term

ce

by

detailed

show

the

(1975)

period

was

(Hinteregger,

which

this

measurements

al.,

to

from

sensitivity

in

major

of

precision

instruments.

the

et

there

Vidal-Yadjar

correct

analyses

various

However,

instruments,

1981)

in

the

cycle,

irradiance,

; Hinteregqer,

example,

that

the

corresponding

Quite

changes

27-day

measuring

(Woodgate

Phissamay,l980

the

of

the

the

1966, Weeks (1967) has already shown that 11 11 -2 -1 to 4 x 10 photons cm set could be

Satellites

tivity.

of

the

use

as

problems

value of

making

such

major

absolute

solar

Using and

two

sensitivity By

2.5

variations

to

author

the

adds

sunspot

that

lead

that

or

try

bring

observations

higher

the

and

of

values

incr-ease

in

densities to

the

to

this

number

thermospheric decided

note

(1979)

is

solar

for

not flux

homogeneity

21

irradian-

than

for

matched

by

corresponding

at

cm

Or,

10.7

It

temperatures.

some

ultraviolet Cycle

into

is the

for

in

this

conse-

reason

observational

data. The

of

Lyman-alpha

1980 in

analysis

four

irradiance

(Figure

the

1).

observed

series

begins

of

This values

with made

figure of

observations

the by

bringinq

satellites

illustrates

Lyman-alpha

:

and

together OSO-1

the of

and

relation 10.7

of

cm

the

AE-E

between

between flux.

observations

The

the data

1969

and

variations represent

909

Short Paper

t

. .

1

1

*

OBSERVATIONS

*

I

*

... ,

. **.

.

LYMAN-ALPHA (1969-iS8Of 200 SOLAR

Lyman-alpha between plotted as a function

corrected) 10.7 cm.

[a) Vidal-Xadjar cember (b)

and

and

December As

series

between

solar

25

1980

(un-

flux

Januari

at

1969

and

16 De-

(1980):

121

observations

between

9 October

lY75;

(1980a,

b):

260 observations

between

3 June

(1980a,

b):

529

between

3 Januari

the

values

1977

and

21

Decem-

1978;

Hinteregger

main

observations

Phissamay

II August

Hinteregger ber

Cd)

496

and

1969 Of

1972;

Vidal-Yadjar 1974

Cc)

(1975):

(10.7cm)

of

Iyradiance

I.-

FIGURE

FLUX

I

I 300

I 100

groups: Cc)

observations

1979

and

31

1980. can

be

seen,

a lower and

an

including

upper

group

of

series for

irradiance (a)

series

and (d).

can (b),

an

be

divided

intermediate

into

three

group

for

910

Short Paper

A

statistical

relations for

for

series

(a)

I = 2.44 with

of

for

series

for

and

all

four

10%

other

than

D =

solar

of

to

10.7

the cm

following

flux

(F):

11

photons standard flux

10 11

-2

set

-1

(1)

deviation

D = 0.19,

num-

F = 220;

exceeding

x

cm

220:

photons

cm -2

SE?C

-1

(2)

with

F maximum

N

x

= 789,

= 375:

IO11

photons

c,-~

set

photons

.m-2

S-SC

-1

(3)

and

the

separated

into

at

N

=

x

1Ol1

-1

(4)

1406.

Vidal-Madjar

period

been

than

(F - 65))

(1975)

D

to

in

0.19

and

(41,

introduced

an

instrumental

Equation

illustrates

the

(l),

as

importance

drift

compared of

effects

activity.

to

flux

F not

reduces

a sufficiently

more

1 leads

= 260;

Equation

according

solar

N

1.34,

this in

them

and

10

maximum

(F - 65))

(a),

year; 1.34

Since cludes

cd),

series

per D =

and

of

D = 0.93,

R = 0.75,

with

x

(F - 65))

(1 + 0.0141

In

Figure

a function

series:

I = 2.2 with

values

(1 + 0.0063

R = 0.78,

for

in

as

R = 0.06,

= 617,

D = 0.39,

(c)

I = 3.79 with

N

(1 + 0.0045

series

data (I)

(F - 65))

coefficient

for

R = 0.79,

with

the

(b):

observations (c),

of

irradiance

(1 + 0.0037

I = 3.61

of

and

a correlation

ber

analysis

Lyman-alpha

of

about

large

10.7

cm:

180

units

levels

of

values

of

classes

65

days

number

several seven

4400

- 80,

-

=

100,

1O-22

by

100

W me2

In

to -

the

120,

Hz-l,

the

it

(1406),

activity.

corresponding 80

(1 unit

solar

covered

observations

is

possible

Figure

2,

following

120

-

to

they

group have

levels

140,

National

in-

140

-

of 160,

Research

Council,

Canada). For form

each

It(t)

It(t) where

class

defined

= I(t) the

-

20

irradiance

c, in +

50

irradiance of

the

has

solar

been

flux

The

for

that a

10%

results

for

t

of < 2000,

instrumental

in

analysis

drift,

in

cm

at

a modified

time

t: (5)

20

expressed

i.e.

10.7

- 60

; F(t)

this

expressed

at

the

units

10

10 11 -2 -1 photons cm set It(t) = 0 at I(t) = 2x10 - 60 F(t) greatest inteqer lower or equal to -20--

seen

is

the

terms

are

results

almost

of

shown of

in

photons

, and

,, F(t)

Figure

Vidal-Madjar

horizontal

cm

straiqht

2,

-2

-

-1 set 60 I

,

is

20

and

(1975) lines

it

can

the

be

corrected are

obtained.

911

ShortPaper

350

300

250

200

too * .

‘t-

50

“’

80-100

,

Is

DAYS FIGURE

On

the

various days

into seven The irradiance values of Figure t regrouped classes defined by the levels of 10.7 cm flux, and plotted as a function of days from 1 Januari 1969 (1) to 31 December 1980 (4383).

2.-

other

hand,

departures

for

t

from

the

:, 3000,

i.e.

for

horizontal.

Hinteregger's

during

periods

data, of

there

several

are

hundred

f The

Figure periods

ideal

2 into of

objective

horizontal

about

150

days,

would straight

be

to

Pines.

containing

at

transform

the

In practice, least

50

various a method

observations,

“curves" based leads

in on to

an

Short Paper

912

almost

ideal

horizontal that The

remain

of

As

were

could

results

ments as

result. that

of

can

probably

this

be

visible be

over

from

Figure

for

Figure 2 have

reduced

procedure

Lyman-alpha

seen

in

if

of

the

almost

shorter

increasing

a period

3,

11 years

from

disappeared;

time

the

departures

intervals

coherence

can,

of

therefore,

the were

the few

used.

the

measure-

be

regarded

satisfactory. The

Figure

final

1. The

result

relation

is

shown

between

in

Figure

and

I

I

1

;-It.,

,,

which

.

is

the

counterpart

is:

I

I

LYMAN _ S).

F

4,

I

(1969-1980)

ALPHA

G >I80

300 *

‘..u‘..*t..,r,

*.

160-180

250 ~.L.,\JJUMR*

. . .- a.

140-160

*

200

150

IOC

.t~.

. ..,

80-100

b

65-80

*

x

I 100

, 1000

2000

.. 3000

I 4000

DAYS FIGURE

3.-

The irradiance increase their

values of Figure homogeneity.

2 after

modification

to

of

913

ShortPaper

CORRECTED

OESERVAT~ONS

. ; *

50

i/ :-tlo%

/

45

40

35

3c

2:

ALPHA 1980) ; &I

I =

4.-

2.55

x

10

with

R = 0.91,

lute

calibration,

irradiance the tion

lines

between

FLUX (lO,?cm)

of solar Irradiance of Lyman-alpha plotted as a function fIux at 10.7 cm as in Figure 1, but after correction for of the measuring instruments. changes in the sensitivity

11 D

cannot in

I

1 300

200 SOLAR

FIGURE

f

I

I

1 100

Figure

+ 0.011 = 0.25,

(F - 65) N

it

is

be

expressed

=

1406.

important

Lyman-alpha

and

to

10.7

10

11

photons

Because

with

4 indicating

x

of

remember an

cm

that

accuracy

departures flux

of is

the

cm

-2

se=

-1

uncertainty the

better

+ 10% __ good.

about

absolute than

show

the

values 25%,

that

the

even

abso-

of though

correla-

914

ShortPaper

ACKNOWLEDGMENT The

authors

are

grateful

to

Dr.Hans

Hinteregger

for

helpful

communi-

cations.

REFERENCES Cook,

J.W.,

solar

flux

Brueckner, in

Hinteregger, trum

and

the

August

1,

Hinteregger, its in

Inst.

The

AGARD

Geophys.

Res.,

G.R.

Rottman,

Tousey,

83,

Geophys. 21

of

Res.,

observed

Res.,

$3,

1933.

solar

EUV

fluxes

solar

irradiance

IJV irradiance

of

monitors,

ultraviolet on

No

MPm.

Sl.

a l'etude

de

No

12,

to

source

the

225,

for

Physical

in

for

the

85,

2257.

EUV

spec-

aeronomical

monitoring July

la

the

Basis

structure

31

for -

163.

of

water

vapor

of

solar

spectral

ionosphere

of

de

1 -

photodissociation June

The

Variability

press.

Conference

in

the

and

Ionosphere

l'ionosphere,

the

mesosphere,

1981.

Rocket

1972

(1963)

R.

The

(1981)

minimum,

solar

System,

Belgium,

(1981)

J.

cycle

of

Solar

Contribution

%leteor.

M.

Nicolet,

2, =

(1945)

solar

experiences on

A,

Geophys.

in

(1980)

Colorado.

(1981)

Proc.

M.

Roy.

solar

AE-E

Solar-Terrestrial

Nicolet,

J.

H.E.

J.

M.E.

- 2100

of

X,X;,

Workshop

Boulder,

variation, the

(1980b)

Proc.

1980,

1175

Representations

Research,

H.E. A.

Hoosier,

Development

(1980a)

Space

1850

Van

absorption,

H.E.

Hinteregger,

and

ultraviolet

(1979)

atmospheric

Hinteregger,

-

far

H.E.

applications,

1200

G.E.

measurements

1977,

J.

extreme

Geophys.

ultraviolet

Res.,

83,

spectrum

irradiance

in

press.

of

the

sun,

during

Space

SC.

Rev.

3.

Vidal-Madjar,

years,

Evolution

Solar

of

Phys.,

$l,

(1977)

The

solar

in ____________~_~ The Solar Output

and

Its

Vidal-Madjar, 234

(1975)

A.

consecutive

A.

the

solar

Lyman-alpha

flux

during

four

69.

spectrum Variation, -_-

at

Lyman-alpha

ed.

O.R.

1216

White,

A,

pages

Colorado

Univ. Vidal-Madjar, solar

A.

minimum,

Weeks,

L.H.

Astrophys. ____-___I_’ Woodgate, Nettleship,

and

Solar (1967)

J. B.E., R.

Proc. Roy. Sot. __-__-_._-~.-~----

Phissamay,

9.

Pliys,,

259.

66,

Lyman-alpha

147 ===’

(1980)

emission

The

from

solar

the

Lyman-alpha

sun

near

solar

flux

near

minimum,

1203.

Knight, (1973) London,

D.E., Extreme 5

222,

ilribe,

R.,

ultraviolet 291.

Sheatler, line

P.,

Bowles,

intensities

from

J.

213

ASSOC.

and

the

Sun,

-