McGreevy ground-based VLF recordings

Web-crawler search words: VLF, ELF, natural radio, aurora, magnetosphere, plasma, University of Iowa, whistler, dawn chorus, INSPIRE.

Aurora over northern Manitoba, Canada on 23 August 1996. Photo by Stephen P. McGreevy

"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 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. Please check out the 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-4B E-Field VLF receiver and 10' (3 meter) vertical antenna. Tape recorder used to create the original recordings was a Marantz PMD 212 3-head professional cassette recorder. 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 spacecraft (see links at bottom of page). Those data recordings lack the ever-present lightning static present when listening with ground-based receivers.

The antenna and front-end circuit of the WR-4B whistler receiver temporarily attaches to my van's rear doors, and the control box containing audio filters, audio level control, headphone amplifier, and recording jacks is located inside the vehicle. This allows for very convenient recording under many weather conditions. I also recorded some of these Natural Radio recordings using my hand-held WR-3E E-field 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 to un-compress the .ZIP files. This page updated July 1996.

ABWT001.ZIP, 488478 bytes

ABWT001.WAV, 156 sec., 1727030 bytes

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).

(Partial) spectrogram of the above 02 June 1996 - 1030 UT Alberta recording

CHORUS.ZIP, 761982 bytes

ALB_CHOR.WAV, 42 sec., 463052 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.

BC_CHOR.WAV, 678020 bytes

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.

ORECHORS.WAV, 34 sec., 374860 bytes

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.

VLF1.ZIP, 291226 bytes

HUGH_WHI.WAV, 7.5 sec., 82724 bytes

Huge whistler (very strong), moderate diffusion recorded 17 Sept. 1993 20 mi. west of Wendover, NV at around 6:30 am PDT (1330 UTC).

LOUD_WHI.WAV, 8.5 sec., 93748 bytes

Another strong whistler, same location as above within 10 minutes of the other one. Initiating sferic "tweek" clearly obvious!

LOUDWHI2.WAV, 9 sec., 99260 bytes

VERY LOUD Mod. diffusion whistler with weak diffuse echo accompanied by triggered emissions at time of whistler.

PURENVWH.WAV, 19.5 sec., 215012 bytes

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.

WHIS4194.WAV, 12.5 sec., 137844 bytes

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.

VLF2.ZIP, 561528 bytes

NVWH_HQ.WAV, 11 sec., 463094 bytes

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.

ORECHORS.WAV, 34 sec., 374860 bytes

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.

VLF3.ZIP, 424245 bytes

2WHIS494.WAV, 30.5 sec., 336276 bytes

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.

AB_CHOR2.WAV, 62 sec., 683532 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 more quickly. Taped 26 Sept. 1993 at 1110 UTC.

VLF4.ZIP, 1384286 bytes

SKAUCHOR.WAV 347300 bytes

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.

NDWVTONS.WAV 132332 bytes

(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").

PUWHICA.WAV 143356 bytes

(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.

PUWHS2.WAV 170916 bytes

15 sec.) Another recording taken from Mike's "INTRO TO NATURAL RADIO" cassette. Series of nice, loud pure whistlers.

WHEPKWHI.WAV 485100 bytes

(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.

SOFTWHIS.WAV 784364 bytes

(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.

PURE0891.WAV 638508 bytes

(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!

CA_CHOR.WAV 352812 bytes

(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.

AK_VLF1.ZIP, 915624 bytes

AKAUCHO.WAV 1008740 bytes, 92 seconds

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.

KENAIWHI.WAV 678020 bytes, 61 seconds

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.

KENAIWH2.WAV 678020 bytes, 63 seconds

09 September 1995, 0930 UTC. Continuation of the Periodic-Emissions recording above.

GRAM23.ZIP, 33333 bytes

You can download SPECTROGRAM 2.3, a freeware Spectrogram program written by R. S. Horne. This spectrogram program plots frequency- versus-time of digital audio recordings. A sound card is required, as this program will not play WAV files using the Windows 3.1x PC-Speaker Driver (as will Sound Recorder). Contains two files: GRAM23.EXE and README.TXT. Lets you save the spectrogram display to a *.bmp file for viewing with Paint Brush. You can also Paste screen prints of the maximized Spectrogram 2.3 window into Word 6.0 or other graphics capable word-processors. Version 2.3 has been improved over version 2.2, allowing for unlimited-length files and also improved bitmap image creation.

Natural ELF/VLF Radio emissions such as these occur in the 0.1 to 11 kHz radio spectrum--essentially, they are audio-frequency radio waves! 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 listen in the Nevada and Oregon high-desert and Great Basin Area, as well as Western 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.

And be sure to check out Stephen's own Natural VLF Radio Home Page!

More Ground-based VLF recordings and associated spectrograms from the S. P. McGreevy SOLAR-MINUMUM VLF RECORDING EXPEDITION to Manitoba, Canada at: http://www.triax.com/vlfradio/sndbites.htm

Another interesting ground-based observation program is the NASA INSPIRE project.

Stanford University's STAR LAB also studies VLF emissions.

Also check out the University of Alaska Fairbanks Geophysical Institute's excellent Home Page and UAF's Poker Flat Research Range Page

Special THANKS to the University of Iowa and the Plasma Wave Group for sponsoring this Ground-based ELF/VLF radio recordings presentation!