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Transcript
Jupiter's Radio Signals
By James L. Ibaugh, AA3C
Anyone for Amateur Radio Astronomy? The first
time I heard signals from Jupiter (aka Jove), I
thought it was long distance noise from a tropical
storm. I almost ignored it, except I questioned
why I was hearing long distance storm noise but
no ham signals from the same WSW direction on
a completely dead 21MHz. The noise had a
strange structure to it, not like the normal
lightning storms I was used to hearing on HF, it
had rhythm! It was the fall of 1974 about 10PM
and I swung my Mosley Triband beam between
south and west, the noise peaked out at about 255
degrees Azimuth (AZ, True of North, not
magnetic). GEOMAGNETIC DECLINATION BY ZIP CODE
I was using a Hallicrafters SX-115 ham band only
receiver so I QSY'ed (moved down) to 14MHz
and it was just as dead as 21MHz, but there was
no strange noises on the 20 meter band. The
reason for both bands being dead was the sun
spot cycle was in it's lowest point. Low points are
good for satellite work because the ionosphere is
transparent to HF and VHF signals. Next peak
was in ~1986. It occurred to me that my receiver
may be getting a gassy tube. I then asked the
*BRIGADEAR* (XYL Shari) if I could use her
Hallicrafters SX-100 HF general coverage
receiver (500 kHz to 32 MHz) and compare the
results. I disconnected my beam coax from my
receiver TR switch and stretched it across the
room to her SWL (Short Wave Listener) station,
connected it to the SX-100's preamp and tuned in
21MHz. To my surprise the signal was stronger
on her SX-100 at S2 on the S-meter and it was
only S1 on mine! That's a 3 dB difference. Both
receivers had identical wide band low noise
+20dB gain RCA Nuvistor front end (external)
RF pre-amplifiers. Then I rationalized, maybe
the noise signal is getting stronger. Since Shari's
SX-100 was easy to tune, I QSY'ed down the HF
band to 20 MHz and when I did the noise was
S2.5 which was 1.5 dB higher. I tried 19MHz
(S2.0), 18MHz (S1.5) and at 17MHz it was even
with background noise and some QRM splatter
from a short wave broadcast station. I wrote it all
up in my combined log book/technical notebook.
I had been working on an academic paper
about deep space gamma ray bursts in my spare
time and spent many hours at the Grundy
Observatory on Franklin & Marshall College's
Baker Campus in Lancaster. On a late fall
evening I was doing some research there on
documentation of the star Constellation Canes
Venatici and star Constellation Hercules. My old
RCA colleague was there, Tony Destazio (PHD
Astronomy from U. of Hawaii) ask me if I would
like to look at Jupiter through F&M's best
telescope. I jumped at the chance. He already was
looking at Jupiter and taking photos for 15
minutes. He mentioned that Earth is the closest
to Jupiter that night then it will be for the next 12
years because Jupiter has a very elliptical orbit
around the sun. Even though Earth passes
Jupiter's solar azimuth each and every year, the
difference in orbital positions are huge. Tony
also mentioned that the Radio Astronomers are
busy studying the High Frequency signals
generated by Jupiter's magnetic fields. That took
my breath away. I managed to blurt out the
question, “What might the Azimuth of Jupiter be
right now?” It was about the same time I heard
the noise on HF bands last night. Tony pointed
to a newish nixeytube digital meter showing the
Azimuth in orange numbers, “255.37 DEGREES.
My knees went weak. The last right hand two
digits changed quickly as the scope's automatic
tracking system kept the large planet in the center
of the photographic plate. I asked, just what do
these HF radio signals sound like? He said he
never heard one. Tony then walked over to a tall
pile of Astronomical Journals and plucked one
out of the middle of the stack and glanced
through the index to find an article. He found it
and handed the journal to me and placed a
cardboard marker in the stack for it's return.
The article described the discovery of Jovian
(Jupiter's) radio signals in 1955 by scientists Dr.
Bernard Burke and Dr. Kenneth Franklin of the
Carnegie Institute in Washington D.C. They
discovered that the planet Jupiter was a strong
22 MHz source of radio waves (that is the only
frequency that they were using). Jovian radio
storms, first noticed in 1955, are beamed to Earth
by natural radio beam generator near Jupiter's
magnetic poles. Jupiter's radio beam generators
are natural, made of plasmas (ionized gases,
mostly Hydrogen) and magnetic fields. High
speed streams of magnetized plasma flowing
downward into Jupiter's polar regions emit radio
waves. "Cyclotron Maser Mechanism" as the
process is known. When this mechanism is
operating, Jupiter can “outshine” even the sun as
a radio source. These cyclotron maser generators
are powered, in part, by Jupiter's large moon Io.
Volcanoes on Io hurl electrically conducting gas
into Jupiter's magnetosphere (the region of space
controlled by Jupiter's magnetic field), where it
collects in a doughnut-shaped region, the large
"Io torus." As Io travels around Jupiter, it plows
through the torus and makes waves. These
"Alfven waves," guided by magnetic forces, carry
about 40 trillion watts of power to Jupiter's
polar regions. Spectrograph: U.of Fla. R.O.
If only 1% of the plasma's electrical current is
converted to RF power, that is 400 billion watts
of RF power between ~16 MHz to ~25 MHz!
400,000,000,000 WATTS is not exactly a peanut
whistle on the HF band in this solar system!
Jupiter's Io-controlled radio emissions are not
broadcast in all directions. The cyclotron maser
generators beam has the shape of a wide hollow
cone. If Earth is inside the cone, we hear nothing.
If Earth is outside the cone, we also hear nothing.
When Earth is in the narrow edge of the cone, we
can hear some strong radio bursts. Speaking of
hearing Old Jove's Voice, Click Here. This voice
was slowed down by a factor of 128 to get it into
human hearing range and was a type S-Burst
signal. S-Burst SLOW Graph: U.of Fla., R. O.
Here is the normal speed Type S-Burst, Click
Here. This was the sound I first heard back in
the fall of 1974* when Earth and Jupiter had a
close encounter. You may have heard old Jove in
other close passes in 1950, 1962, 1974*, 1986,
1998 or 2010. It is best heard during or close to
(with in a year or two of) a solar cycle minimum
as in 1951, 1962, 1973*, 1984, 1995 or 2006.
If you would like to see Jupiter with your own
bare naked eyes, it NOW is the third brightest
object in the sky besides the sun and the moon.
<>JUPITER's Location in PM Dec 9, 2010
<>From 40.09N 76.41W QTH, LOCAL TIME
7PM 1900HRS 191ºAZ 45ºELivation
8PM 2000HRS 210ºAZ 41ºEL
9PM 2100HRS 227ºAZ 34ºEL
10PM 2200HRS 240ºAZ 25ºEL
11PM 2300HRS 252ºAZ 14ºEL
12PM 2400HRS 262ºAZ 3.3ºEL
..0014HRS 264ºAZ 0º EL, BELOW HORIZON
<>Jan 9th, 2011 Jupiter Location in PM
5PM 1700HRS 187ºAZ 47ºEL
6PM 1800HRS 207ºAZ 44ºEL
7PM 1900HRS 225ºAZ 37ºEL
8PM 2000HRS 239ºAZ 28ºEL
9PM 2100HRS 251ºAZ 17ºEL
10PM 2200HRS 261ºAZ 6.5ºEL
10:30PM 22300HRS 266ºAZ 0ºEL
Viewing works only on clear cloudless nights.
9PM(2010)=227ºAZ and 9PM(2011)= 251ºAZ
Jupiter moved only 24ºAZimuth (17ºEL) in 30
days, less than one degree AZ per day. The 24º
AZ change is the increased distance to Jupiter
next month. The Earth moves through 360º
solar azimuth while Jupiter moves only through
30º solar azimuth per one earth year. Slow
poke. Both orbits are significantly elliptical
with Jupiter having a 12 earth year solar orbit.
Jove's size, reflectivity, and close distance to
Earth (355 million miles once every 12 years)
make it a very bright object in the sky. Earth is
now moving away from old Jove at ~14,000
miles per day (583.333MPH).
Visit the web page WWW.AMSAT.ORG for
tracking information, tools and software.
Jupiter rotates once every 10 hours and the cone
rotates with it like a lighthouse beam. To catch a
radio storm you have to know (1) when Earth
will be aligned with the edge of the cone and (2)
when Io is in the right position to pour electrical
energy into the radio storm zone. Every ten hours
there are two chances to hear Jupiter as Earth
passes both sides of the radio cone. Once you
detect the signal record the date and time, ten
hours later the same signal should be heard as
long as Jupiter is above the horizon. When
Jupiter is behind the Sun or moon it's no go for
big old Jove's signal. Jove can be heard during
day light hours and in cloudy weather.
Most HRO's do not have elevation control of
their HF beams, just point in the general azimuth.
Try it with a wire antenna. I've heard Jupiter with
a 100 foot long wire and the *Brigadear*'s R.L.
Drake SSR-1A battery powered solid state
general coverage SWL receiver (fall of 1996).
There is a government sponsored program for
schools and youth groups to build, setup and
operate their (or your) own Jupiter Radio
Observatory (not limited to Jupiter). NASA's
RADIO JOVE PROJECT.
A special Radio Astronomy receiver kit is for sale
to non-hams who do not have access to a good
HF receiver. A free informative PDF manual to
the Radio Astronomy Receiver Kit Click here.
More information about Radio Jove Project.
For the non-hams, FREE antenna PDF manual
JOVE RJ1.2 Dual Dipole Antenna Array. This
antenna manual contains a useful chart (Fig. 1.5)
“Elevation angle of Jupiter at transit, observers at
different northern latitudes from 2003 to 2013.”
It has good wire antenna information for DX'ers.
The free radio astronomy software for use with
their receiver kit or your ham receiver is available
for Windows 98/NT/2000/Xp/Vista (works AOK
on my Win7.0): RADIO-SkyPipe 2.1. FREE!
SkyPipe 2.1 works with your computer's sound
card, with or without Internet connection. Internet
connection if want to share data on line. It works
on other projects better than most of my paid
commercial scientific chart recorder programs I
have used in the lab before, like LabChart-V, etc.
Jupiter's Radio Image on 22 cm band. NASA.
Disclaimer: Even though we are approaching
the next solar sunspot peak 2012 to 2013, there
are times that the Maximum Usable Frequency
(MUF) falls well below the 16MHz to 25MHz
range of Jupiter's signal emissions. Even when
the MUF is in that range the characteristic sound
of Jovian Radio Burst Emissions may be heard
above Earth's weak radio signals and static noise.
Results may vary with each radio setup, time,
date, year and degree of patience.
This adds new meaning to the newish phrase
Radio Amateur Astronomy. From a star gazer to
a star listener. Have fun snagging Jupiter DX.
73's de AA3C. Jim A A 3 C @ A R R L . N E T