The correlation between the irradiance (as measured by the Active Cavity Radiometer Irradiance Monitor and the Earth Radiation Budget) as corrected for sunspot flux deficit (which is responsible for most of the variance of the uncorrected signal) and both the 205 nm flux (as measured by Nimbus 7) and a photometric facular index is discussed. The computer program which simulates two-dimensional convection in a compressible, stratified medium is described. Equipment which was acquired to perform high precision, white-light observations of sunspot areas, and procedures were tested. Analysis of observations of large scale convective heat inhomogeneities which were obtained in May 1985 was begun

Petro, L. D.

English

NASA Technical Reports Server

n(NASA-CR-176797) A N : I N V E S T I G A T I O N OF THE N86-26047 *
E N E R G Y B A L A N C E OF SOLAR A C T I V E EEGIONS USING
THE A C R I M I R B A D I A N C E . I A T A Semiannual
Progress Report/ May - Oct. 1S65 Unclas
CAtmospheric_and EnvironmentalL Eejsearch) G3/93 _43212_ '•;
An Investigation of the Energy Balance of o
Solar Active Regions Using the
ACRIM Irradiance Data
Larry D. Petro
Atmospheric and Environmental Research, Inc.
840 Memorial Drive
Cambridge, MA 02139
J
October 1985
Semi-Annual Progress Report for Period
May 1985 through October 1985
Contract No. NASW-4062
Prepared for :
National Aeronautics and Space Administration
Solar Maximum Mission Guest Investigator Program
https://ntrs.nasa.gov/search.jsp?R=19860018575 2020-03-20T14:19:59+00:00Z
TABLE OF CONTENTS
Page
1. INTRODUCTION 2
2. WORK COMPLETED DURING THE REPORTING PERIOD 2
2.1 Influence of Faculae on Solar Irradiance 2
2.2 Model of the Influence of Sunspots on Solar Irradiance 3
2.3 Observations of the Influence of Sunspots on Solar Irradiance 4
2.4 Observations of Large-Scale Heat-Flow Inhomogeneities 5
3. PLANS FOR WORK DURING THE FINAL CONTRACT PHASE 6
3.1 Influence of Faculae on Solar Irradiance 6
3.2 Model of the Influence of Sunspots on Solar Irradiance 6
3.3 Observations of the Influence of Sunspots on Solar Irradiance 7
3.4 Observations of Large-Scale Heat-Flow Inhomogeneities 7
1. INTRODUCTION
This report fulfills the required submission of a semi-annual progress
report under NASA contract NASW-4062, "An Investigation of the Energy Balance
of Solar Active Regions Using the ACRIM Irradiance Data". During the
reporting period Dr. Larry Petro replaced Dr. Peter Foukal as principal
investigator for the contract as a result of Dr. Foukal's leaving his position
at A.E.R., Inc. As approved in a letter from the Contracting Officer on
September 4, 1985, a portion of the work to be carried out under NASW-4062
has been subcontracted to Cambridge Research and Instrumentation, Inc., which
is Dr. Foukal's present place of employment. All work described in this
progress report has been carried out in consultation with Dr. Foukal.
2. WORK COMPLETED DURING THE REPORTING PERIOD
2.1 Influence of Faculae on Solar Irradiance
A paper entitled "The Influence of Faculae on Total .Solar Irradiance and
Luminosity" was completed by Dr. Foukal and collaborator Dr. Judith Lean
and will be published in the April 15, 1986 issue of the Astrophysical
Journal. That work presents a correlation detected between the irradiance
(as measured by both ACRIM and ERB) as corrected for sunspot flux deficit
(which is responsible for most of the variance of the uncorrected signal) and
both the 205-nm flux .(as measured by Nimbus-7) and a photometric facular
index. This suggests that faculae contribute significantly to the total
solar flux. These cross-correlations, as well as the cross-correlation with
the correction itself, are shown in Figure 1. It can be seen that both
facular indicators (2295 an& pf) provide 25 per cent larger correlation at
zero lag than does the sunspot correction and these indicators have non-zero
positive-lag cross-correlation, whereas the sunspot correction function has no
positive-lag correlation, thereby supporting facular emission as the cause of
correlation with the corrected radiances rather than error in the correction.
Further measurements demonstrate that faculae and sunspots make approximately
equal, but opposite sense, contributions to the total irradiance on an active
region time-scale during the spot-maximum year 1980. Arguments are presented .
that these two contributions are independent, and therefore facular emission
is not simply reradiated sunspot-blocked flux.
_ a) ACRIM -P, vs - P,
o-HM
-0.5
1
L- b) ACRIM -P, vs 205 nm
-0.5
1
-0.5
'i l i i I l i l i i i i l i i i i
i i i. .1 i l l l l l i i i l l l 11
l l l i i l l i I I l l I i l l l
- c) ACRIM -P, vs P,
i i i i i i
I I I I I I I I I I I I I I I I I
1 I I t I t
-72 72
-Lag (day) +Lag (day)
Fig. 1. Cross-correlation functions (solid lines) of sunspot
compensated radiance (denoted ACRIM - Pg) vs.
(a) - PS, (b) 205 nm flux, and (c) Pf. The dashed
line in (a) gives the autocorrelation function of
ACRIM - Ps.
2.2 Model of the Influence of Sunspots on Solar Irradiance
A consultant under the contract, Dr. Eric Graham, has provided
a computer program which simulates two-dimensional convection in a
compressible, statified medium. This has been successfully run at A.E.R.
by Dr. Wei-Hwan Chiang on a Cromemco CS-1, MC68000-based, microcomputer. A
velocity field previously calculated by Dr. Graham with an earlier version
of the code (J. Fluid Mech. (1975), 70, 689) was reproduced in a verifica-
tion run on the microcomputer which required 15 CPU-hours and employed a
9 cell by 16 cell grid for the finite difference scheme. This run attained
a convective steady state, as demonstrated by the evolution of the Nusselt
number shown in Figure 2. The final state consists of two counter-rotating
convection cells as shown in Figure 3.
oc
O O Q O
to
13
Z
n
LJ
U.
o
O O o O
0.0B 0.2B 0.HB
TIME
0.60 0.80
Fig. 2. Evolution of the Nusselt Number during a numerical
simulation, using a microcomputer, of two-dimen-
sional convection in a compressible, stratified
medium. The computer code was provided by Dr. E.
Graham.
«
+
f
\
^__ _ -T _ *^_
^ — . ^ >
x - — ^
 V
^ , . \ t
. ^ - X /\
__,»
^~
^
N
\
\
t
f
/•
• \
\
t
r
ti
s , . _ ___ ^
/ ^ -
 N
! . ;r : : :J
^ \ s ^ _ ^ ; •f J
\ s^,,^  ^^^ ^ >
-~~~ ^ ^
Fig. 3. Velocity field of the steady-state convection for
the case illustrated in Figure 2. The grid is 9
cells by 16 cells.
2.3 Observations of the Influence of Sunspots on Solar Irradiance
Equipment has been acquired by Dr. Foukal to perform high-precision,
white-light observations of sunspot areas, and procedures were tested during
the reporting period, but as yet no measurements have been obtained. These
observations were seriously impeded by the lack of sunspots during this time
of solar-cycle minimum. Careful comparison of the Questar 3.5 inch aperture
and the Unitron 4.0 inch aperture telescopes demonstrated that the Unitron
telescope had lower scattered light (a desirable feature for accurate sunspot
area measurements), and it was therefore purchased. A 35-mm camera and an
evaporated-chromium neutral-density filter are also employed, the latter
allowing the full-aperture resolution (1.2 arc-seconds) to be utilized while
achieving proper exposure.
-An attempt to extract sunspot areas from measurements of film negatives
with a computerized P.D.S. microdensitometer at American Science and
Engineering was deemed unsuccessful due to the large amount of computer
post-processing required. It has therefore been decided to employ a simple
measurement procedure which consists of first locating the spots with respect
to a heliographic grid and then graphically measuring the spot area from
calibrated enlargements of the original photographic negatives.
Improved CCD observations of sunspot bright rings have been obtained
in a cooperative arrangement with the National Solar Observatory at Sacra-
mento Peak. These new observations include better photometric correction
calibration scenes which should provide greater photometric accuracy.
Previous observations which we obtained did not have sufficiently good
auxiliary photometric calibration that low-contrast, large-scale features
could be securely measured.
2.4 Observations of Large-Scale Heat-Flow Inhomogeneities
Dr. Chiang and Dr. Petro began the analysis of observations of large-
scale convective heat inhomogeneities which were obtained in May 1985 at the
Vacuum Telescope of the National Solar Observatory on Kitt Peak, Arizona.
These observations benefitted from the lack of sunspots, which has hindered
the observations described in Section 2.3. The original data consist of 120
monochromatic scans of the Sun, each comprising 512 by 2048 pixels. Data
compression of the original, fine-scale observations, geometric rectification,
transformation to a standard metric, and photometric correction have been
accomplished for a 5-day subset of the 16-day observation. An example of such
corrected, standard-metric intensity residuals are shown in Figure 4. The
intensity range of the grey-scale image is ±2 per cent of the intensity at
ORIGINAL PAGE- IS ©MBIML F££-J
OE POOR QUALITY
center of the disk and the pixel size is 8 arc-seconds square. Features
visible include granular noise, faculae near the limb, and the limb itself
A typical monochromatic, photometric scan of one-quarter of the
Sun (measured in latitude) which will be used to detect large-scale
heat-flow inhomogeneities
3. PLANS FOR WORK DURING THE FINAL CONTRACT PHASE
General problems anticipated during the final six months of the contract
in obtaining the goals discussed below are the absence of Dr. Chiang for
three months while he is a Visiting Scientist at National Radio Astronomy
Observatory and the possible absence of sunspots.
3.1 Influence of Faculae-on Solar Irradiance
The work described in Section 2.1 fulfills the terms of the contract and
no further work will be performed on this topic.
3.'2 Model of the Influence of Sunspots on Solar Irradiance
Dr. Graham is nearing completion of a modification of the code
described in Section 2.2 which will provide a realistic representation of
heat flow in the presence of a sunspot. As before, this code will run on the
Cromemco MC68000-based microcomputer. It is estimated that multi-CPU-day
runs will be required to attain a convective steady state with this new
model. It is planned for Dr. Graham to consult at AER during this final
phase of the project and for Drs. Foukal, Chiang, and Graham to prepare
a paper on the results obtained with the new model. The dynamical model
will provide a more secure estimate of the effect of sunspots upon the
luminosity of the Sun than provided by an eddy heat diffusion model (Foukal
et al. (1983), Ap. J., 267, 863).
6
3.3 Observations of the Influence of Sunspots on Solar Irradiance
Further observations of sunspots to provide measured sunspot areas will
be attempted by Dr. Foukal during the remaining six months of the contract.
The success of this is contingent upon the presence of sunspots which,
however, have been few in number during the past year.
The observations of sunspot bright rings described in Section 2.3 will
be analyzed during the remaining six months of the contract using existing
analysis programs at A.E.R.
3.4 Observations of Large-Scale Heat-Flow Inhomogeneities
Work to be completed during the final six months of the contract
includes the extension of the procedures described in Section 2.4 to the data
from the remaining 11 days, smoothing and co-adding of the scenes to reveal
large-scale features, and, if necessary, statistical testing for giant
convective cells. Priority is being given to this project during the time
while Dr.. Chiang is at A.E.R., before his visit at N.R.A.O. These results
will be described in a paper to be prepared by Drs. Chiang, Foukal, and
Petro.


An investigation of the energy balance of solar active regions using the ACRIM irradiance data

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server