This file was recorded in northern Alberta, Canada on 13 August 2000 at
approximately 1500 UT, during my August 2000 (near solar-maximum) VLF
recording expedition into the auroral-zone region of northern Alberta,
Canada.
"Natural Radio" describes
naturally-occurring electromagnetic (radio) signals emanating from
lightning storms, aurora (The Northern and Southern Lights), and most
importantly, the Earth's magnetic-field (the Magnetosphere).
This is a presentation of Earth's
natural radio emissions that occur in the extremely-low-frequency to
very-low-frequency (ELF-VLF) radio spectrum--specifically, at AUDIO
frequencies between approximately 100 to 10,000 cycles-per second (0.1 -
10 kHz).
Unlike sound waves which are vibrations
of air molecules that our ears are sensitive to, natural radio waves as
received at ground-level are vibrations of electric and magnetic energy
(electromagnetic waves) which--though occurring at the same frequencies
as sound--cannot be listened to without an audio-frequency ELF-VLF radio
receiver to convert the natural radio signals directly into the same
sound frequencies. Another amazing realm of nature is thus ready to be
explored and observed.
Naturally-occurring VLF radio emissions
are being studied both via ground-based receiving systems as well as
orbiting spacecraft receivers such as the
POLAR spacecraft.
Much of these phenomena begin as plasma waves in Earth's magnetosphere.
Please check out the U. Iowa Plasma Wave Group links toward the bottom
of this page for much more information.
All of the following Natural Radio
recordings were recorded by Stephen P. McGreevy using the McGreevy WR-3
with 85 cm whip antenna or WR-4b E-Field VLF receiver and 10' (3 meter)
vertical antenna except for the Alberta June 1998 stereo recordings
which were made on two similar (but not exactly the same)
magnetic-field/loop antenna receiving systems developed by Stephen
Ratzlaff and Stephen McGreevy. Most of the the following files were
recorded at 8 bit, 11 kHz sampling rate.
These are examples of ELF-VLF radio
phemonena which can be heard in middle-latitudes (30-60 degrees north
geographic latitudes) by anyone with an audio-frequency ELF-VLF radio
receiver at ground level. Similar recordings to these have been made by
satellite-based receivers in Earth's orbit, such as the POLAR-PWI
spacecraft (please see links at bottom of this page). Those data
recordings lack the ever-present lightning static present when listening
with ground-based receivers.
The following files can be downloaded
either in "bulk" via the larger .ZIP extension heading over the
individual .WAV file listings, or they can be downloaded individually.
You will need PKUNZIP version 2.04g or greater to un-compress the .ZIP
files. This page updated 12 October 1998. Special thanks to the
University of Iowa Plasma Wave Group for sponsoring this presentation!
Stephen P. McGreevy
Natural Radio Audio Files Listing:
Whitemud River region, Northwestern Alberta, Canada 13 August 2000 - Near Solar-Maximum Recording Expedition to Alberta Canada
Spectacular STEREO recording of a
phenomenon called 'hooks' recorded on 13 August 2000 at approx. 1500 UT
using a cross-azimuth dual loop recording ststem. The location was 56.3
deg. north/118.1 deg. west.
HOOKS.ZIP
5.5 MB compressed file in ZIP format recorded at 22050/16 bit rate, about 1 min 20 sec. in duration.
SUMMER 1996 SOLAR-MINIMUM VLF
RECORDING EXPEDITION
to Manitoba, Canada: Grass River Provincial Park 22 Aug. - 05 Sept.:
Beautiful full-sky aurora in Manitoba, Canada on the night of 28-29 August 1996. Photo by Stephen P. McGreevy
I was located 45 miles south-east of Flin Flon, Manitoba, a
fine place for aurora watching and Natural ELF-VLF Radio monitoring
during the late summer)
August 1996 Manitoba audio files:
Recorded at
Grass River Provincial Park in central-western Manitoba, Canada on 30
August 1996 at 1652 UTC during the McGreevy Summer 1996 Solar-Minimum
ELF-VLF Recording Expedition in the auroral-oval region when aurora can
be frequently seen overhead - LONG RECORDING and ONE OF MY FAVORITE
recordings of a mesmerizing mixture of different elements of chorus.
Also a nice segment of echoing (whistler-mode) chorus trains.
30a1652.wav,
51 sec., 562268 bytes
23 August
1996 at 2228 UTC - Spectacular "nose-whistler" along with hissband and
triggered upward-rising emissions similar in sound to bird calls. This
whistler had sustained echo-trains and many of them are audible in this
recording, along with its initiating lightning static burst!
23a2228.wav,
40 sec., 442656 bytes
24 August 1996
at 1500 UTC -Strong, low-pitched whooping and hooting tonal emissions of
1 kHz or less, and very-weak background low-pitched roaring hissband.
One of my favorite segments!
24a1500.wav,
14 sec., 161140 bytes
June 1996 Alberta ELF-VLF radio phenomena audio file:
An incredible-sounding 2 1/2 minute
recording of spectacular wavering-tone periodic emissions. Wildly
varying upward and downward pitched whistling and whooping sounds.
Similar phenomena to the "Kenai Crazy Whistlers/Hooks" audio files below
but even more spectacular sounding. Well worth the download time!
Recorded in a remote location by the Whitemud River in northwestern
Alberta, Canada, about 45 miles/60 km north-west of Peace River, AB on
02 June 1996 at approx. 1030 UT (4.30 a.m. MDT).
Death Valley National Park, s.e. CALIFORNIA
Panamint Valley Whistler Shower
This recording was taped on Thursday, 12 March 1998 at 1415 UT/6.15 a.m.
PST in the northern Panamint Valley, Death Valley National Park in a
very quiet place far from any AC powerlines. There are about 100 (fairly
diffuse) whistlers per-minute occurring, of light to moderate
intensity. A closer, more pure-tone whistler is heard following a loud
lightning stroke static burst about 9 seconds into this recording.
(Local weather was clear and about 45F, minor geomagnetic storm in
progress). McGreevy WR-4b VLF receiver, 2.5m vertical whip antenna.
This
event was very RARE at 36.5 degrees north latitude between the middle
of 1996 up to recently due to the low sunspot count and a very quiet
sun. NOW, we're going to be hearing more of this event as the the
sunspot count and associated solar-flux and CME/flare-induced magnetic
storms occur. This event is not of the caliber of 'whistler storms'
heard during the most recent solar-maximum (1989 - 1991), but the fact
that this occurred is very exciting!
pvws0312.wav,15 sec.,160138 bytes
Beautiful Alberta Auroral Chorus taped
during a visible display of Aurora (Northern Lights). I was located 150
miles east of Red Deer, AB Near Consort, AB. In this segment, squawking
"chorus" is accompanied by a multitude of "sliding-tone emissions."
When these sliding- tones would be heard, the aurora would suddenly
brighten up and move quicker. Taped 26 Sept. 1993 at 1115 UTC.
Very loud Auroral Chorus taped during
rare severe magnetic storm. I was located next to Eve's River in
northern Vancouver island, BC, Canada on 21 Feb. 1994 at 1045 UT. Aurora
was visible through partial cloud cover and moonlight. This mag. storm
also nearly wiped out HF (SW) reception.
Loud Dawn Chorus and Hiss, recorded 18
Aug. 1993 in southeastern Oregon's Alvord Desert. 1430 UTC, 0730 PDT.
Major magnetic storm in progress. Magnetic field "micro-pulsations" are
very evident (slow undulations in the hiss/chorus every 3-4 sec similar
to ocean waves.
04 June 1993, 60 miles NNE of Reno,
NV, 1430 UTC, 7:30 am PDT. Weak Dawn Chorus (minor mag. storm in
progress with weak background layer of sferics plus very strong sferics
from lightning within 100 mi. of receiver. A strong, pure whistler of
slow descending rate occurs after one of these semi- local lightning
sferics.
01 April 1994, 1130 UT/0330 PST, 100
mi. north of San Francisco, CA in Mendocino Co. (Fish Rock Road 20 mi.
west of Ukiah). Clusters of nearly pure whistlers occurred all night and
were quite beautiful! This segment has two strong and two very weak
whistlers.
04 June 1993, 60 miles NNE of Reno,
NV, 1430 UTC, 7:30 am PDT. Weak Dawn Chorus (minor mag. storm in
progress with weak background layer of sferics plus very strong sferics
from lightning within 100 mi. of receiver. A strong, pure whistler of
slow descending rate occurs after one of these semi-local lightning
sferics. This segment taped at 44 kHz sampling rate.
Loud Dawn Chorus and Hiss, recorded 18
Aug. 1993 in southeastern Oregon's Alvord Desert. 1430 UTC, 0730 PDT.
Major magnetic storm in progress. Magnetic field "micro-pulsations" are
very evident (slow undulations in the hiss/chorus every 3-4 sec similar
to ocean waves.
01 April 1994, 1130 UT/0330 PST, 100
mi. north of San Francisco, CA in Mendocino Co. (Fish Rock Road 20 mi.
west of Ukiah). Clusters of nearly pure whistlers occurred all night and
were quite beautiful! This segment has many whistlers of varying
strength. I really like this segment of the tape for its nice mix of
whistlers and tweeks.
Beautiful Alberta Auroral Chorus taped
during a visible display of Aurora (Northern Lights). I was located 150
miles east of Red Deer, AB Near Consort, AB. In this segment, squawking
"chorus" is accompanied by a multitude of "sliding-tone emissions."
When these sliding- tones would be heard, the aurora would suddenly
brighten up and move more quickly. Taped 26 Sept. 1993 at 1110 UTC.
Taped 25 Sept. 1993 at
around 0930 UTC 20 km. north of Watrous, Saskatchewan parked on a dirt
road in a wheat field about 250 meters from powerlines (hence somewhat
louder powerline hum than desired). Interesting Auroral chorus and "nose
whistlers" recorded during faint auroral display. Risers, hiss, and the
peculiar whistlers are heard in this 31.5 sec. segment. Taped by Steve.
McGreevy, using the WR-4B receiver.
(12 sec.) 22 Sept. 1993,
about 1830 UTC 7 miles north of Rolla, ND and just a few miles from
Manitoba border. Very loud hissband with strange upwardly wavering tone
emissions of extreme purity--sort of like a tropical bird call! Taped by
S.P. McGreevy, using McGreevy version of Mideke RS-3 modified for
hand-held use with 1 meter whip antenna.(Also called "Periodic
Emissions").
(13 sec.) Nice, pure
whistlers and hissband, recorded by Michael Mideke using one of his many
"whistler receivers" (RS-2, RS-3, etc.) near San Simeon, CA (Baldwin
Ranch) in 1989 or 1990. Taken from his "INTRO TO NATURAL RADIO" cassette
developed for the NASA Inspire experiments in Spring 1992.
(44 sec.) I taped these
weak pure whistlers while van-camped at Wheeler Peak Campsite (Great
Basin National Park), campsite 25, on 16 Sept. 1994 with a 500 ft. wire
strung to the north-east at about 6-15 feet above the ground in the
aspen and fir trees. A lovely dawn was occurring with beautiful orange
and other colors. These whistlers and associated lightning sferics were
probably occurring from nasty t-storms pummeling Dallas, Texas and
eastern Nebraska (Omaha area). The geomagnetic indices were also rather
low (A=6-7, K=0-1, SF in the 80's). Not the most impressive recording of
whistlers but it was a very pretty moment there by that awesome
mountain! Taped via McGreevy WR-4B and longwire front-end unit.
(71 sec.) T-storms in the
Plains and Rockies were launching this multitude of very hissy
(diffuse) whistlers, taped on 13 June 1993 near Berlin, Nevada (Ghost
town) at about 1330 UTC with WR-4B and 15 foot vertical wire.
(58 sec.) An early
recording of pure whistlers taped in Marin County, CA on 16 Sept. 1991
with McGreevy BBB-2 whip ant. receiver and funky Craig 212 3-inch
reel-to-reel machine with speed variations. This was the year I really
began taping natural radio in earnest, and there was plenty to hear
during this Solar Maximum period!
(32 sec.) A Michael
Mideke recording of dawn chorus and evident mag. field micro-pulsations
(undulations in the chorus trains). Taken from his INTRO TO NATURAL
RADIO TAPE at its closing. Recorded in Cen. CA at Mike's Ranch listening
site in 1990 or 1991.
06 September
1995, 40 miles (65 km) NE of Fairbanks, Alaska. 2030 UTC during major
magnetic storm. Recorded by the Chatanika River deep in the Interior of
Alaska, this strong mid-day Auroral Chorus phenomena presented loud
hissband centered on 1 kHz; chorus trains of low barks and high chirps
centered at 1.5 and 3 kHz, and other tonal emissions above 3 kHz. This
location is within the Auroral Oval, and such phenomena is audible
during the daytime at these high geo-magnetic latitudes. Recorded using
the McGreevy WR-3E hand-held ELF/VLF receiver with 1 meter long whip
antenna into Marantz PMD-212 cassette recorder.
09 September
1995, 0930 UTC. Periodic Emissions sounding like "Crazy Whistlers" due
to their falling then abrupt rising tonal qualities and pure tones.
These were recorded near Skilak Lake on Alaska's Kenai Peninsula. Nice
aurora was also visible through the broken cloud cover. Recorded using
the McGreevy WR-3E hand-held ELF/VLF receiver with 1 meter long whip
antenna into Marantz PMD-212 cassette recorder.
You can download SPECTROGRAM 4.2, an
incredable freeware Spectrogram program written by R. S. Horne. This
spectrogram program plots frequency- versus-time of digital audio
recordings. A sound card is required. This is an update over Gram 2.3
for 32-bit operating systems (Win 95, Win 98, NT 4.0)
Naturally-occurring ELF/VLF Radio emissions
such as these occur in the 0.1 to 11 kHz radio spectrum--essentially,
they are audio-frequency radio (electromagnetic) waves as received at
ground level. Most of these emissions begin as
PLASMA WAVES
within Earth's magnetosphere. This is just a small variety of
fascinating 'sounds' to be received at these ELF/VLF frequencies. You
must be located at least 1 to 2 miles from any power-lines so their
'hum' is not received (this is why I make my recordings in the
California, Nevada and Oregon high-desert and associated Great Basin
region, as well as western and central Canada--plenty of open spaces
away from electric lines to make decent ground-based recordings and
observations.
For spacecraft observations and more information on related phenomena, see the U of Iowa
Plasma Wave Group
page.
Sounds of the Magnetosphere
at the University of Iowa Plasma Wave Group. .WAV-file Recordings from
orbit via the POLAR spacecraft. Includes text descriptions and
spectrograms of each.
Another interesting ground-based observation program is the NASA INSPIRE
project, a project to involve high school students in the study of these fascinating phenomena.
