Satellite observations of the sun over almost 5 yrs show that principally two UV active longitudes have persisted over a significant portion of this observational period. A comparison between the position of solar magnetic sector boundaries and UV enhancements of the sun seems to show, at least during the year 1969, that the UV maxima tend to occur near the times when a solar sector boundary is near central meridian. An estimate of the magnitude of the variable UV solar energy input into the atmosphere resulting from the rotation of active solar longitudes is that for wavelengths less than 175 nm and down to H Lyman-alpha it exceeds the annual variation, whereas at longer wavelengths it is less

Heath, D. F.

Wilcox, J. M.

English

A description is given of the relationship observed between enhancements in the far ultraviolet solar irradiance and the position of the solar magnetic sector boundaries. The ultraviolet observations were made with the monitor of ultraviolet solar energy (MUSE) experiments which were launched aboard Nimbus 3 in April 1969 and Nimbus 4 April 1970. A comparison between the positions of solar magnetic sector boundaries and ultraviolet enchancements of the sun seems to show, at least during the year of 1969, that the ultraviolet maxima tend to occur near the times when a solar sector boundary is near the central meridian. An estimate of the magnitude of the variable ultraviolet solar energy input into the atmosphere resulting from the rotation of active solar longitudes is that for wavelengths less that 175 nm and down to H Lyman alpha it exceeds the annual variation whereas at longer wavelengths it is less. The total observed peak to peak variation in the ultraviolet irradiance from 120 to 300 nm over a solar rotation is typically at least 230 ergs/sq cm sec

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https://ntrs.nasa.gov/search.jsp?R=19740019198 2020-03-23T07:14:12+00:00Z
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of this document contact:
Technical Information Division, Code 250 --
Goddard Space Flight €enter
-Greenbelt, Marylanid 20771."-
(Telephne 3-824488)-
I-°
A POSSIBLE CORRELATION BETWEEN MAXIMA OF THE FAR
ULTRAVIOLET SOLAR IRRADIANCE AND CENTRAL MERIDIAN PASSAGES
OF SOLAR MAGNETIC SECTOR BOUNDARIES
O
BY
Donald F. Heath
Goddard Space Flight Center
Greenbelt, Maryland
and
John M. Wilcox
Stanford University
Stanford, California
I
I
The question of the possible existence of a causal relationship
between solar activity and meteorological phenomena has been the
subject of many investigations. Recently there have been a series
of papers reporting a connection between passages of solar magnetic
field sector boundaries past the earth and certain meteorological
phenomena. That work with ample references to past work has been
reported in detail by Wilcox (1974) as a part of the proceedings of
the "Symposium on Possible Relationships Between Solar Activity and
Meteorological Phenomena."
It is the purpose of this work to describe the relationship
which has been observed between enhancements in the far ultraviolet
solar irradiance and the position of the solar magnetic sector
boundaries. The ultraviolet observations have been made with the
Monitor of Ultraviolet Solar Energy (MUSE) experiments which were
launched aboard Nimbuis3 in April 1969 and Nimbus 4 in April 1970.
The Nimbus 4 experiment is still operating. A summary of the circum-
stances of observed and well defined sector boundaries is contained
in the work by Wilcox (1974).
The MUSE experiment has been described in detail by Heath (1973)
and it consists of five broad band photometers which respond to
solar radiation from.1ll5 nm to 300 nm. Since the instrument was
flown on the sun-synchronous Nimbus 3 and 4 satellites it has been
possible to observe the intrinsic variability of the sun as an
ultraviolet variable star. The persistent regions of solar
1
variability that are related to the rotation of long-lived active
regions are shown in figure 1. Each point gives the solar
longitude of the central meridian for the day number when the
ultraviolet solar irradiance (principally - H Lyman alpha) was
observed to be a maximum. The different symbols simply indicate
the different active regions by virtue of their clustering about
preferred solar longitudes. The nature of these curves is outside
the scope of this paper and it used only to illustrate the fact
that there are two very long lived regions of ultraviolet activity
which were separated by about 1800 in solar longitude in 1969.
Figure 2 shows the polarity of the interplanetary magnetic
field as observed by spacecraft orbiting the earth (Wilcox and
Colburn, 1972). The grey shaded area represents field directed
away'from the sun and the black indicates field directed toward
the sun. The days on which the ultraviolet solar irradiance
peaked during a solar rotation are indicated by the same symbols
that were used in Figure 1.
Since there is a delay of about 4 1/2 days between the time
a sector boundary is at central meridian on the sun and the time
at which the solar wind carries it past the carth, (Wilcox, 1968)
the sector boundaries shown in Figure 2 should be shifted back-
ward by about 4 1/2 days to give the time at which they were near
central meridian on the sun. When this is done one notes that the
ultraviolet peaks marked with Icl arz vry lse LO the time
when an away - toward boundary was near central meridian, and the
2
ultraviolet peaks marked with X's are very close to the time
when a toward - away boundary was near central meridian.
This relation is quantitatively displayed in Figure 3, which
shows a histogram of the time in days of the ultraviolet peaks
with respect to the time at which a sector boundary was near
central meridian. A clustering of the ultraviolet peaks near the
sector boundaries is evident. We reserve judgement on the small
difference between away - toward and toward - away boundaries
until more observations have been analysed.
Typical increases in the solar ultraviolet above the minimum
during a solar rotation which were observed with the MUSE experi-
ment in 1969 were typically: 25% at H Lyman alpha, 5% at 175 nm,
and 1% at 295 nm. In terms of the equivalent width of the photo-
meter channels this would correspond to increases above the minimum
during a solar rotation of: 1.6 ergs/cm 2 sec at H Lyman alpha,
1.0 erg/cm 2 sec at 175 nm and 230 ergs/c 2 sec. at 295 nm, In other
words typically variations per solar rotation are greater than thp
annual variation below 175 nm and less than above 175 nm. This
representative increase associated with the solar rotation of
ultraviolet active regions should be considered when considering
possible physical causes to explain the observed correlations
between passages of the solar magnetic sector boundaries past the
earth and meteorological phenomena.
In summary, satellite observations of the sun over almost five
years have shown that principally two ultraviolet active longitudes
3
have persisted over a significant portion of this observational
period, A comparison between the positions of solar magnetic
sector boundaries and ultraviolet enhancements of the sun seems
to show, at least during the year of 1969, that the ultraviolet
maxima tend to occur near the times when a solar sector boundary is
near central meridian. An estimate of the magnitude of the
variable ultraviolet solar energy input into the atmosphere
resulting from the rotation of active solar longitudes is that for
wavelengths less than 175 m and down to H Lyman alpha it
exceeds the annual variation whereas at longer wavelengths it is less.
The total observed peak to peak variation in the ultraviolet
irradiance from 120 to 300 nm over a solar rotation is typically
at least 230 ergs/cm2 sec.
4
References
Heath, D. F., 1973: "Space Observations of the Variability of
Solar Irradiance in the Near and Far Ultraviolet", J. Geophys.
Res., 78, 2779-2792.
Wilcox, J. M., 1968: "The Interplanetary Magnetic Field. Solar
Origin and Terrestrial Effects", Space Science Revs., 8, 258-
328.
Wilcox, J. M. and Colburn, D.S., 1972: "Interplanetary Sector
Structure at Solar Maximum", J. Geophys. Res., 77, 751-756.
Wilcox, J. M., 1974: "Solar Activity and the Weather", Proceedings
Symposium on Possible Relationships Between Solar Activity and
Meteorlogical Phenomena, Goddard Space Flight Center, Nov. 7-8,
1973, Greenbelt, Maryland
5
Figure Captions
Figure 1: Carrington solar longitude of the central meridian on
days of observed UV maximums in irradiance. The different
symbols represent regions on the basics of groupings in
longitude.
Figure 2: Representation of the sectors of the large scale solar
photospheric magnetic field which is carried radially outward
by the solar wind as it sweeps by the earth. The dotted or
grey regions are for the away field and the black regions are
for the towards field. Times of solar ultraviolet enhance-
ments are indicated with the same symbols used in figure 1.
The sector boundaries were near central meridian on the sun
about 4 1/2 days before the times shown in the figure at which
the boundaries were observed by spacecraft orbiting the earth.
Figure 3: Histogram of the time delay in days between an observed
ultraviolet solar enhancement (UV max) and a corresponding
central meridian passage of the solar magnetic field sector
boundary.
6
360 o
0 0 0z
300 - o 
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z ~200
0<0
< OO
o -
Xx
n u 100- xx -
0 X I I I I I I
100 300 100 300 100 300 100 300 100 300
UV MAXIMUM (DAY NO.)
1969 1970 1971 1972 1973
969
JAN 1 3
JAN 4 5 10 15 20 25 30 JAN
I I I I I I I I I I I I I I I I I _ I I I I
JAN 31 1 5 10 15 20 25 26 FEB
I I I I I I I I I I I I I I I I l I I I I I I I I
FEB 27 28 5 10 15 20 25 MCH
I ! 1 1 1 I I I I I I I I I II I I _L _ __ _ L I__ _I ,! I 1 • •
MCH 26 30 1 5 10 15 20 21 APR
L I I I I l I , i L I I ~I 1_ I I I
APR 22 25 30 5 10 15 18 MAN
MAY 19 20 25 30 1 5 10 14 JUN
JUN 15 a 20 25 30 10 11 JUL
I I I I I I I I I I I I I J_1 J.L.L__I I I I I
JUL 12 15 20 25 30 1 5 7 AUC
I I I I I I I I . i I _ I I I I! I I I
AUG 8 10 15 20 25 30 1 SEP
I I I I I I I , , I i I I I ! .L ! __J., , I I II I I I
3
SEP 4 5 10 15 20 25 - 30 SEP
I I I I ! ! I I I I LJ I I I ILJ L J1J1.Lj
OCT 1 5 20 25 27 OCT
I I I I I I I I I I I I I I I l
OCT 28 311 5 10 15 20 23 NO
NOV 24 25 30 1 4 5 10 5 DEC
II.I.I l1..111
DEC 21 25 3i
I I I I I I I I I I L I
5
AWAY-TOWARD
5
TOWARD-AWAY
0 I I
1969
5
COMPOSITE
-4 -2 0 +2
DAYS FROM CENTRAL MERIDIAN
OF SECTOR BOUNDARY


A possible correlation between maxima of the far ultraviolet solar irradiance and central meridian passages of solar magnetic sector boundaries

14537
A Possible Correlation Between Maxima of the
Far Ultraviolet Solar Irradiance and Central
Meridian Passages of Solar Magnetic
Sector Boundaries
DONALD F. HEATH
Goddard Space Flight Center
and
• JOHN M. WILCOX
Stanford University
The question of the possible existence of a
causal relationship between solar activity and
meteorological phenomena has been the subject of
many investigations. Recently there have been a
series of papers reporting a connection between
passages of solar magnetic field sector boundaries
past Earth and certain meteorological phenomena.
That work with ample references to past work
has been reported in detail by Wilcox (1975)
elsewhere in the proceedings of this symposium.
It is the purpose of this work to describe the
relationship
 (that has been observed between
enhancements in the far UV solar irradiance and
the position of the solar magnetic sector bound-
aries. The UV observations have been made with
the Monitor of Ultraviolet Solar Energy (MUSE)
experiments, which were launched aboard Nimbus
3 in April 1969 and Nimbus 4 in April 1970. The
Nimbus 4 experiment is still operating. A sum-
mary of the circumstances of observed and well-
defined sector boundaries is contained in the work
by Wilcox (1975).
The MUSE experiment has been described in
detail by Heath (1973); it consists of five broad-
band photometers that respond to solar radiation
from 115 to 300 nm. Since the instrument was
flown on the Sun-synchronous Nimbus 3 and 4
satellites, it has been possible to observe the
intrinsic variability of the Sun as a UV variable
star. The persistent regions of solar variability
that are related to the rotation of long-lived active
regions are shown in figure 1. Each point gives
the solar longitude of the central meridian for the
day number when the UV solar irradiance (prin-
cipally, H Lyman-alpha) was observed to be a
maximum. The different symbols simply indicate
the different active regions by virtue of their clus-
tering about preferred solar longitudes. The na-
ture of these curves is outside the scope of this
paper and is used only to illustrate the fact that
there are two very long lived regions of UV
activity that were separated by about 180° in
solar longitude in 1969.
Figure 2 shows the polarity of the interplane-
tary magnetic field as observed by spacecraft
orbiting Earth (Wilcox and Colburn, 1972).
Because there is a delay of about 4l/2 days be-
tween the time a sector boundary is at central
meridian on the Sun and the time at which the
solar wind carries it past Earth (Wilcox, 1968),
the sector boundaries shown in figure 2 should be
shifted backward by about 4Vi days to give the
time at which they were near central meridian on
the Sun. When this is done, one notes that the
ultraviolet peaks marked with circles are very
close to the time when an away/toward boundary
79
https://ntrs.nasa.gov/search.jsp?R=19760007449 2020-03-22T18:20:45+00:00Z
80 RELATIONSHIPS BETWEEN SOLAR ACTIVITY AND METEOROLOGICAL PHENOMENA
100 300 100 300 100 300 100 300 100 300
UV MAXIMUM (DAY NO)
1969 1970 1971 1972 1973
FIGURE 1.—Carrington solar longitude of the central
meridian on days of observed TJV maximums in irra-
diance. The different symbols represent regions on the
basis of groupings in longitude.
J A N i s
JAN 45 10 15 20 25 30 JAN
1 i I I i i i i I
JAN 3! 1 5 10
FEB 27.28 ' 5 10
MAR 26 30 ^^ 5
5 20 25 26 FEB
15 ,20 25 MAR
o 15
 x
 20 21
 APR
APR 22 25 .-,30 1 5 10 ^w15
MAY 19" 20
 n 25 30 1 5 10 v
JUNE t5 r.20 25 30 - * 10
a MAY
4 JUNE
i JULY
JULY „.
 15 AUG
30
 y 1 SEPT
SEPT 45 10 15 25
 x 30 SEPT
OCT ' QlO 15 20 2 5 * 2 7 OCT
I i i I 1 i i i I I i i 1 i i i i i i i I I 1 I i I i I
OCT 28 31 1 5
 n 10 15 20 X23 NOV
NOV 24 25 30 1 10 15 LDEC
DEC 21 25 n3i
FIGURE 2.—Representation of the sectors of the large-
scale photospheric magnetic field carried radially out-
ward by the solar wind as it sweeps by Earth. The
shaded regions represent the field directed away from
the Sun and the black regions represent the field
directed toward the Sun. The times of solar UV en-
hancements are indicated with the symbols of figure
1. The sector boundaries were near central meridian
on the Sun about 4*/2 days before the times shown in
the figure at which the boundaries were observed by
spacecraft orbiting Earth.
was near central meridian, and the UV peaks'
marked with X's" are very close to the time
when a toward/away boundary was near central
meridian. . '
This relation is quantitatively displayed in figr
ure 3, which shows a 'histogram of the time in
days of the UV peaks with respect to the time at
which a sector boundary was near central merid-
ian. A clustering of the UV peak's near the sector
boundaries is evident. We reserve judgment on
the small difference between away/toward and
toward/away boundaries until more observations
have been analyzed. .
Increases in the solar UV above the minimum
during a solar rotation that were observed with
the MUSE experiment in 1969 were typically
25 percent at H Lyman-alpha, 5 percent at 175
nm, and 1 .percent at 295 nm. In terms of the
equivalent width of the photometer channels, this
would correspond to increases above the mini-
mum during a solar rotation of 1.6 ergs/cm2 • s
at H Lyman-alpha, 1.0 erg/cm2 • s at 175 nm,
and 230 ergs/cm2 • s at 295 nm. In other words,
variations per solar rotation are typically greater
than the annual variation below 175 nm and less
than above 175 nm. This representative increase
associated with the solar rotation of UV active
regions should be considered when examining
possible physical causes to explain the observed
correlations between passages of the solar mag-
netic sector boundaries past Earth and meteoro-
logical phenomena.
In summary, satellite observations of the Sun
over almost 5 yr have shown that principally two
UV active longitudes have persisted over a sig-
nificant portion of this observational period. A
comparison between the position of solar mag-
netic sector boundaries and UV enhancements of
the Sun seems to show, at least during the year
1969, that the UV maxima tend to occur near
the times when a solar sector boundary is near
central meridian. An estimate of the magnitude
of the variable UV solar energy input into the
atmosphere resulting from the rotation of active
solar longitudes is that for wavelengths less, than
175 nm and down to H Lyman-alpha it exceeds
the annual variation, whereas at longer wave-
lengths it is less. The total observed peak-torpeak
variation in the UV irradiance from 120 to 300
FAR SOLAR IRRADIANCE AND SOLAR MAGNETIC SECTOR; BOUNDARIES 81
AWAY—TOWARD
Wilcox^J. M., 1968 J^e Interplanetary Magnetic
Solar Origin and Terrestrial Effects," Space Sci. Rev.,
8, pp. 258-328.
Wilcox, J. M., 1975, "Solar Activity and the Weather?'
Possible Relationships Between Solar Activity and
Meteorological Phenomena, NASA SP-366.
Wilcox, J. M., and D. S. Colburn, 1972, "Interplanetary
Sector Structure at Solar Maximum," J. Geophys. Res.,
77, pp. 751-756.
- 4 - 2 0 +2
DAYS FROM CENTRAL MERIDIAN
OF SECTOR BOUNDARY
FIGURE 3.—Histogram of the time delay in days between
an observed UV solar enhancement (UV max) and a
corresponding central meridian passage of the solar
magnetic field sector boundary.
nm over a solar rotation is typically at least
230 ergs/cm2 • s.
REFERENCES
Heath, D. F., 1973, "Space Observations of the Varia-
bility of Solar Irradiance in the Near and Far Ultra-
violet," /. Geophys. Res., 78, pp. 2779-2792.
DISCUSSION
LONDON: The Nimbus 3 observations showed, for.
some of the filtered measurements in the UV, a fairly
pronounced solar rotation period in the shorter wave UV.
Was there a similar solar rotation period in the Nimbus
4 observations? And, if the UV is related to magnetic
sector fluctuations, should there not then be a semirota-
tion period in the variation rather than a solar rotation
period? Should there not be a 14-day rather than a 27-
day period?
HEATH: The variations are similar both on'Nimbus
3 and 4 and, at times when you have the two active
regions, they are separated by about "180° in solar longi-
tude.
QUESTION: As I remember, what was shown in the
Nimbus 3 results was a full .solar rotation period in the
fluctuation, not a 14-day, but on the order of 27 days.
HEATH: Two curves in figure 1 represent the two
very long-lived active regions, and they are about 180°
apart in solar longitude, so :there is UV enhancement
essentially twice per solar rotation.
RASOOL: What were these enhancements?
HEATH:.In the case of Lyman-alpha, typical varia-
tion in 1969 was the order of enhancement of 25 percent
above the normal background during that solar rotation.
In the case of 1750 A, it was of the order of 5 to 6
percent enhancement over one solar rotation; that is, per
each active region. If there were two, you would have
two peaks of that magnitude, and, for the longest wave-
length, 2900 A, it was. .only during the very high .period
of solar activity during the spring of 1969 that we saw
an enhancement of the order of 1 percent at 2900 A.
RASOOL: How is this related to your statement about
the order of magnitude increase at 2900 A?
HEATH: If I use the same sensor that gives these
data and I compare the absolute values of the solar ra-
diance derived from the rocket .flight in 1966 at solar
minimum with the satellite data beginning in 1969 at
solar maximum and continuing into 1970, then the dif-
ference is about an order of magnitude at 2900 A and
also at 1750 A but not at Lyman-alpha.


A possible correlation between maxima of the far ultraviolet solar irradiance and central meridian passages of solar magnetic sector boundaries

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