AstroNotes 1980 May Vol: 19 issue 05

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ISSN 0048-8682
The newsletter Magazine of the Ottawa Centre of the RASC
Vol. 19, No. 5 $2.00 a year May, 1980
Editor.......Rolf Meier.......77 Meadowlands Dr .W... 224-1200
Addresses.....Jacqui Tapping...61 Oval Drive........684-1186
Circulation...Barry Matthews...2237 Iris St........ .225-6600
OBSERVER'S GROUP MEETING - APRIL 4
Renee Meyer and Mary Geekie
Chairman Robt Dick opened the meeting at 8:15 pm with
42 people in attendance, 7 of whom were non-members.
Robin Molson proceeded with the IRO update. Anyone
wishing to help with maintenance at IRO should contact
Robin, Ken Tapping, or Pierre Lemay.
Rob Dick reminded the group of the Halifax General
Assembly, to be held on the Dominion Day weekend. Those
members wishing to present papers at the G.A. must obtain
a supporting letter from Council. Those members wishing to
submit displays for the G.A. should contact display coordinator Rob McCallum at 729-9977. A list of categories may
be found in the February issue of the National Newsletter.
Barry Matthews informed the group that a room has
been secured at the bottom of the N.R.C. building in which
to store Ottawa Centre equipment, including the Hargreaves
donation. It is possible that a flea market will be held
to sell some specialized equipment.
Anyone wishing to help or take over hospitality is
strongly encouraged to contact Ted Bean.
The first theme talk of the evening was delivered by
Fred Brisson on the subject of solar observation to aid in
navigation. Fred observed the sun's shadow from a fixed
point at various intervals of the day and recorded the
results on fine graph paper. Fred stressed the importance
of accuracy in time and mathematical calculations.
Through his solar observations, Fred had deduced a method
of determining his terrestrial coordinates of latitude and
longitude.Ted Bean has taken over the instrumentation coordinatorship from Pierre Lemay. He is sponsoring a telescope
workshop on April 12. Anyone locating a paper bag containing various astronomical documents is asked to contact
Ted Bean.
Ken Tapping reported a call on April 4 from Walter
Turner at A.R.O. informing him of a large solar burst.
Ken, using his radio interferometer at 10.7 cm, observed
that as the flare signal increased, the W.W .V. radio
signal from Colorado decreased greatly. This was due to
the emission of soft x-rays which enhanced the ionization
level in the ionosphere and thus weakened the reflected
signal. Jim Zillinsky, using his 230-MHz receiver, did
not observe any substantial burst.
Ian C. Johnson proceeded with the evening’s final
theme talk concerning the disputes of Immanual Velikovsky' s
controversial theories eminating from the book "Worlds
in Collision". Through the years, Ian has collected
various articles and sources of information concerning
debates, discussions, and reviews pertaining to
Velikovsky's theories. Perhaps one of the most controversial theories is the concept that Venus originated as
matter ejected from Jupiter and then, through various
interactions with the earth, achieved its present near
circular orbit. Various discussions ensued this topic.
John Molson presented several interesting slides
taken from the Saguenay, St. Lawrence area. His slides
included aurora, star trails, and meteors.
Rob Dick, using his box-shaped 6-inch refractor,
observed a series of complex sunspots on M arch 15 and 30.
Rob proceeded to corelate his observations with diagrams
drawn by John Molson.
Rob also informed the group that he had received a
letter from Noman Sperling, an editor with Sky and
Telescope. The letter contained various favourable
comments concerning the February issue of Astronotes.
Thanks, Norm, for your astronomical intere st.
The meeting was adjourned at 10:17 by the chairman.
#########
There will be a telescope workshop on Saturday,
May 3, 10 am, NRC, Sussex Drive.USING THE SUM AS A REFERENCE TO FIND ONE'S LATITUDE AND
LONGITUDE
Fred Brisson
Careful observation of the sun can give to an observer
the necessary information for identifying the coordinates
at the observer's position. This position finding technique can be useful to navigators on ships on the open sea,
to aerial navigators, and to amateur astronomers.
I have delighted in doing this observing of the sun
on my living room table during the winter months, opposite
a south-facing window. My instruments included a bubble
level (to make sure the table is level), a sheet of fine
graph paper (for recording the observations), a very sharp
pencil, a short screwdriver (to cast a shadow for observing purposes), and the precise time (as broadcast by CHU).
The key point about this exercise is to determine
what is the shortest lenght of the shadow on the graph
paper, and the exact time when the shadow was at its
shortest length. Measure the length of the shadow to the
nearest 0.5 mm, and the time of the shortest shadow to the
nearest second of time.
To measure the length of the shadow, start plotting
the length of the shadow (put an "x" on the paper right
where the tip of the shadow falls) around 10:30 local
time, with the paper lined up north-south. You want the
shadow at noon to fall near the center of the paper, for
convenience. To get an accurate plot, very great care
must be taken not to move the paper the least bit while
observing between 11:00 and 13:00. Then join all the
plots with a line. This line will form a long curve.
The more plots are on the paper the better it is, although plots every 10 minutes should be enough.
If an observer also writes the exact time of each
plot on the graph paper, it is possible to determine the
exact time it was when the shadow was at its shortest
length. The easiest was, however, to find out this time
to the nearest second is to take on observation time
around 10:30 and one around 13:30. With some computation
and averaging, the exact time when the shadow observed
in the forenoon and the shadow observed in the afternoon
have exactly the same length, it is possible to obtain
the exact time when the shadow was at its shortest (see
figure).
This technique is a challenging exercise that becomes quite easy after trying several times, and helps
in understanding the relation of sun to earth.WHAT THE SUN GAVE US FOR EASTER
Rob Dick, Ken Tapping, Chip Wiest, and Jim Zillinsky
The sun, being very close to the earth, astronomically
speaking, can be observed using techniques which are not
available for other stars. Only the sun is close enough
for topographical study and for its radio and other emissions to be detected without equipment available to only
a few professional astronomers. It is therefore much
easier to draw conclusions as to what is going on, although sometimes the vast amount of data so easily available from the sun tends to frighten off, rather than encourage.
Over the period April 4-7 (the Easter period) the
sun was quite active. The most active day was April 6,
whan several flares were produced. The weather that day
was good enough for optical observations and Rob Dick
obtained some good drawings and photos. Radio observations were made by Ken Tapping and Jim Zillinsky on wavelengths of 75 cm and 130 cm respectively. At the same
time, signal strength recordings were made by Ken Tapping
and Chip Wiest of the transmission from radio station
WWV, Fort Collins, Colorado.
The optical observations show the positions and
arrangements of the sun spots and faculae. These are the
white-light aspects of solar active regions, areas of
enhanced magnetic field which extend into the corona.
Flares occur in these magnetic structures. When flares
occur, vast energies are released which were originally
stored in distortion of those magnetic fields. The removal of this vast "strain” can result in substantial
changes in the visible structure of the active region -
hence the value of the optical observations.
In the flare, electrons are accelerated to substantial fractions of the speed of light - maybe as much
as 0.6 C. These interact with the magnetic fields and
the material in the corona to produce radio waves, which
are observed by means of radio telescopes. The extensive and vast heat releases and possible further electron
acceleration results in the emission of x-rays from
sources in the corona. These enhance the levels of ionization in the earth's ionosphere, affecting the reception of distant short-wave stations - hence the WWV experiment. The flare explosion usually ejects a cloud of
material at speeds of up to 400 km/sec. This escapesfrom the sun and moves outward. If it hits the earth,
aurorae are observed.
We will now describe the various data obtained and
then attempt to do a little detective work!
The Optical Observations
The seeing on April 6 was fair with useful observations being possible for a few seconds per minute. Using
a 6-inch refractor, several white-light photographs were
taken between 10:45 and 11:00 EST.
The most significant active region on the disc was
a large group of sunspots about 7.5 arc-minutes long, with
a large spot close to the center of the disc. On
Saturday, April 5, this spot was clearly split, with the
northern spot of the pair having a fine, light line
stretching roughly east-west across it (see fig. 1).
On Sunday, this pair of spots appeared to have joined
together with 2 thin, light bridges stretching east-west
across the middle. The southern bridge had at least one
light spot at mid-span (fig. 2).
The drawings were made from the photographs, using
supplementary notes made while observing. The weight
to be placed upon the observations of the tiny spots is
doubtful; the limited resolution of the photographs only
hinted at their existence.
The Radio Observations
Both the 75-cm and the 130-cm receivers indicated a
high level of activity. The 75-cm record shoved much
more variation with time than the 130-cm record, which
indicated a high, fairly steady emission. Walter Turner
(a former member, now at Algonquin Radio Observatory)
was observing the sun at 10.7 cm. He reported several
emission peaks, the largest of which reached about
700 solar flux units. He also added that multiple
x-ray events had occurred. The activity period persisted
until late in the day, but as the sun moved out of the
part of the sky "seen" by the antennas, no further useful
data was obtained. The recording made at 75 cm is
shown in fig. 3.
The WWV Observations
The signal path between Fort Collins and Ottawa isalmost east-west and in the process of making the trip,
the signal reflects from the ionosphere. The effect of
solar activity upon the propagation of the W WV signal
(in this case 15 MHz) is extremely complex. However,
solar x-ray bursts have an immediate and distinctive
effect which is readily identifiable. Contrary to the
radio flux measurements described earlier, these observations are of a secondary nature. The signals originate
from the station WWV - a time standard station. What we
observe are effects upon the propagation of the signal to
Ottawa. Under normal conditions the signal passes
through the lower ionosphere - where part of it is absorbed - and is reflected by the upper atmosphere. Each
time it passes through the lower ionosphere, part of it is
lost.
The effect of the solar x-rays is to increase the ionization at all levels in the ionosphere by varying amounts.
However, the effect of the increases in the number of ions
in the lower atmosphere is most important here. It
drastically increses the absorption of the signal, causing
what is known as a "fade-out". In addition, because when
the x-rays cease, the lower ionosphere rapidly recovers,
the signal loss fairly faithfully follows the solar x-ray
events. On April 6, several fadeouts were observed, of
which 2 were substantial, showing that several solar
x-ray bursts had occurred.
Discussion
The various data obtained are summarized in fig.
The upper and middle traces respectively show the solar
radio emissions at 75 cm and 130 cm. The lower trace
shows the WWV signal strength data. In order to better
illustrate the correlation of the short-wave fade-outs
with the radio bursts, the signal strength has been
plotted so that it increases downward. The signal strength
changes are given in dB , ie, on the scale 40 corresponds
to the signal changing by a factor of 104 (10,000). Thus
it can be seen that the signal fades were substantial.
It is reasonable to regard the lower record to indicate
solar x-ray emission, signal increasing upwards.
Therefore data is availble for optical wavelengths
2 radio wavelengths, and - indirectly - x-ray wavelengths.
The optical observations are of objects lying in the
solar photosphere. The radio emissions originate in the
corona; the 75-cm signal originating maybe 40,000 kmabove the photosphere (assuming that they originate in
a coronal streamer) and the 130-cm emissions originating
at roughly 140 ,000 km. The x-rays would originate from
a source in the lower corona.
Putting all the data together, we can derive a guess
picture of what was going on. The x-ray bursts coincided
with the energy releases which powered the radio emission
processes. These releases gave rise to electron accleration. These electrons moved upwards, along the magneticlines of force and were trapped in the magnetic loop. In
interacting with the magnetic field, radio waves were
produced. As the 75-cm emissions originate in a lower and
therefore denser part of the corona, they would decay
more rapidly after each excitation. The longer wavelength signals, oringinating higher up in the corona, decay
more slowly. Therefore they would appear to be smoother in
character. The recordings on both wavelengths seem to be
of the type of event known as Type IV radiation.
One point of particular interest is that at about
11:50 EST, the x-ray burst which is indicated in the
WWV record was accompanied by a signal dip in the 130-cm
recording. A possible interpretation of this is thatat about 11:50, a flare occurred, producing the observed
x-rays. This enhanced the emission at 75 cm. However,
the blast disrupted the region where the 130-cm emissions
were produced. When the source recovered, the emissions
returned to their original level.
Although the radio telescopes used here were unable
to determine the position of the radio source on the sun,
we can get an indication. To radio waves at these wavelengths, the solar corona acts as a lens, tending to
focus radio emission almost radially outward. Thus to
be observable at the earth, it is likely that the radio
source be situated close to the center of the disc —
which was where that sunspot group was. We can therefore suggest that this group was where the flares
occurred. The overall scenario is shown in fig. 5.
DISPLAYS FOR THE GENERAL ASSEMBLY Rob McCallum
One particular feature of the annual RASC General
Assembly is the display competition. The displays can be
almost anything related to astronomy, for example, photos,
a piece of equipment you built, the light curve of a
variable star, or a slide show. And there are prizes for
the better entries!
Ottawa always seems to do rather well - we walk away
with at least a few awards. Two years ago at Edmonton we
cleaned up; we must have won half the awards, including
the prestigious "judges' choice". So, in an effort to uphold our reputation, I have appointed myself "Display
Coordinator" for this year's G.A. in Halifax. What this
means is that I will soon be approaching those people
whose observing activities have become known to me, either
through Astronotes or the meetings, to prepare a display
based on your work. And if I don't contact you, and you'd
like to do one, please call me. I'll look after the registration and transportation to Halifax (of the display, not
your body) if you like.
Finally, for those who would like assistance, technical help can be provided by the coordinators. I can
help with the production of the display itself. So, gang,
let's see what we can do.- 14-ASTRO n o t e s
t o
MS. ROSEMARY FREEMAN CAST
NATIONAL SECRETARY
THE ROYAL ASTRON. SOC. OF CAN.
124 MERTON STREET
TORONTO, ONTARIO M4S 2Z