Telegraph1859 or earlier – A geomagnetic storm in 1859 induced currents on long telegraph lines so high the coils at the receiving side sometimes burst into flames, or the operators received electric shocks. In other instances, the current induced by the geomagnetic storm led to diminishing of the signal, when subtracted from the battery polarity, or to overly strong and spurious signals when added to it. Operators in such cases learned to disconnect the battery and rely on the induced current as their power source. Other than Aurora, this was probably the first sensing of the effects of a geomagnetic storm. (Wouldn’t it be great to have a long antenna like that and absolutely no hum!)

1886 – Helliwell mentions that the first reports of whistlers came from a 22 km telegraph line at Sonnblick High Altitude Observatory in Austria with a telephone receiver connected. This is probably the first reception of a radio signal by humankind.

1894 – During an auroral display in the month of March, British observers connected telephone receivers to telegraph lines and were able to hear tweeks and possibly whistlers and chorus.

1899 – At his research facility in Colorado Springs, CO, Nikola Tesla reported hearing the voices of Martians as he conducted experiments on locating lightning. In a 1989 column in The Lowdown, Michael Mideke speculated that what Tesla heard might have been Natural Radio sounds. That is still indeed a very interesting speculation.

1919 – During World War I, vacuum tube amplifiers connected to widely separated ground rods were used to eavesdrop on the telephone conversations of the other side by picking up ground currents induced by the field telephones. H. Barkhausen’s paper mentioned that at certain times strange whistling sounds could be heard on these devices. Those monitoring these units would report, “You can hear the grenades fly.” Barkhausen suggested that these strange sounds might correlate with meteorological disturbances. He even considered that the amplifiers themselves might be causing the sounds, but despite extensive testing, was never able to reproduce the phenomenon in the laboratory. He finally concluded that the sounds were of unknown origin.

1925 – 1929 – T. L. Eckersley published a series of papers and postulated the existence of a dispersive medium. His observations indicated that whistlers were associated with magnetic storms. An article titled “Musical Atmospherics was published in Nature in 1935.

1930 – In another paper, Barkhausen offered two possible explanations for whistlers. The first, which is caused by a series of multiple reflections between the earth and the ionosphere, is the same method that produces tweeks. In the second, Barkhausen introduced the idea of a dispersive medium. He indicated that a remote lightning stroke, a direct current impulse that contains all frequencies, was the initiating event. He was at a loss, however, to explain the long duration and low amount of attenuation in whistlers. He concluded that more observation would be needed.

In the period from 1931 to 1951, there was almost no Natural Radio research being done. This was mostly due to WWII. It is interesting to note that until the 1950s only about 15 papers had been published regarding Natural Radio phenomena.

Research surged ahead in the ‘50s due to the end of the war and aided by the invention of the tape recorder which made the capture and detailed study of these signals possible.

1950 – Professor Robert Helliwell and his associate Jack Mallinckrodt were studying tweeks at Stanford University and heard long (1-3 s) whistlers of descending frequency mixed in with the tweeks. This began his research into whistlers and other atmospheric phenomenon.

1950s – L.R.O. Storey, in Cambridge, England, begins a serious study of the nature and origin of whistlers. Through his observations of whistlers, he formed the basis of the “magneto-ionic” theory of their origin, and also of a magnetic storm’s effect on whistlers. Storey’s research made an important contribution to the growing body of knowledge about whistlers by showing that whistlers followed the earth’s magnetic field lines.

1953 – L. R. Owen Storey publishes “Study of Whistling Atmospherics” in Phil. Trans. Roy. Soc., 1953

1953 – The Naval Research Laboratory begins studying whistlers ni 1953. The lab’s VLF expert at that time was Harold E. Dinger who made substantial contributions in the fields of radio propagation, radio interference reduction, frequency management, and geomagnetics. Dinger wrote a book in 1956, titled “Whistling Atmospherics” which was published by the NRL. The abstract of Dinger’s book summarizes what the laboratory was doing in the early 50’s:

Since 1953 NRL has been observing and recording audio-frequency atmospherics and their correlation with other geophysical phenomena. Beginning in April 1955, the diurnal variation in both whistler activity and the occurrence of “dawn chorus” has been determined. Whistler coincidence at several locations has been recorded in an attempt to prove L.R.O. Storey’s theory on the mode of propagation of these atmospherics. Many whistlers of unusual character have been spectro-analysed for the purpose of extending present theory to cover the general case. Plans have formulated for synoptic observations at a number of selected locations during the International Geophysical Year.

1955 – Emory Cook released several Natural Radio recordings on disk. One of them, Out of This World, featured sounds of whistlers, tweeks and the dawn chorus. These recordings were done in collaboration with Dr. M.G. Morgan, Thayer School of Engineering, Dartmouth College, Hanover, N.H.

Ionosphere was released in 1955 and contains simultaneous Natural Radio recordings made in Hanover, NH near Dartmouth College where Professor Morgan was on staff and Washington, DC. Hanover and Washington are separated by about 415 miles or 665 km. which generates some very wide spaced stereo. I assume that this recording was done in cooperation with the Naval Research Laboratory.

1956 – Don Gleason wrote a pair of articles in the December 1956 issue of Popular Electronics that introduced readers to Natural Radio sounds. Thus, the world of Natural Radio was opened to all interested hobbyists. Don Gleason’s article, “How to Hear Whistlers” laid out the plans for a simple whistler receiver. The radio was based on a loop antenna. There was even a Carl & Jerry story about whistlers a few months later in Popular Electronics.

1957 – The International Geophysical Year (IGY) was a pivotal event for Natural Radio, with over 50 receiving stations set up worldwide. A receiving station and transmitter were set up at Siple Station in Antarctica, and thus began a very intense period of whistler and geomagnetic research,

1958 – James Van Allen discover the radiation belts that surround earth, later named the “Van Allen Belts.” This discovery confirmed L.R.O. Storey’s measurement from several years earlier.

1960 – The launching of several satellites carrying VLF receivers in the early 1960s (Allouette, IEEE-1, Injun) allowed the detailed study of whistlers in the ionosphere which greatly built on the body of knowledge from the IGY.

1965 – Robert Helliwell, a professor and researcher from Stanford University, publishes the book, “Whistlers and Related Ionspheric Phenomenon.” This book is still the “bible” for Natural Radio listeners. It presents a formal theory for whistler propagation and details much of the research done during the IGY.

1970 – By the 1970s there was explosion of research into space weather and the related Natural Radio signals, as being able to understand the phenomena was essential to keep the growing number of satellites in healthy condition.

It is impossible to list all the significant research papers and studies, but the body of knowledge grows daily, as well as our ability to predict the effects of solar activity on Earth and the associated space weather conditions. At this time also Natural Radio listening emerged as a hobby, so the events that marked the rise of the hobby and amateur observations are listed here. Please note that the amount of research and discovery in the past 30 years is immense.

1975 – The LWCA is founded and The Lowdown is published in California by W. R. McIntosh. The publication at that time was an 8 ½” x 11″ mimeographed bulletin.

1980 – Sometime in the 1980s, the GOES satellites, which sit in geostationary orbits and have a primary mission of producing weather photos of earth, began carrying sensing instruments to measure space weather.

1981 – W. R. McIntosh becomes too ill to continue publishing and Bill Oliver takes over The Lowdown and the publication assumes its present form.

1988 – The HSGS (High School Ground Station) was established by Bill Taylor of NASA; Bill Pine, a high school physics teacher; and two amateur scientists, Michael Mideke and Jim Ericson. ACTIVE/HSGS was a test bed project which involved 100 high schools making observations of transmissions from the Soviet ACTIVE satellite.

1989 – Michael Mideke coins the term “Natural Radio” and becomes the first Natural Radio Editor of The Lowdown.

1990s – The Internet. The arrival and growth of the Internet facilitated exchange of information between Natural Radio hobbyists and eventually made real time solar and geomagnetic information available to everyone. It’s hard to imagine this hobby without the instant access to GOES and ACE data as well as all the excellent articles and discussion groups on the net.

1991 – Steve McGreevey and Frank Cathell create the WR-3 handheld whistler receiver and began selling it on a casual basis.

1991 – Following the proof of concept demonstrated through HSGS, INSPIRE was formally organized and incorporated. INSPIRE is a non-profit scientific, educational corporation whose objective is to bring the excitement of observing natural and man-made radio waves in the audio region to high school students.”

1995 – SOHO, Solar & Heliospheric Observatory, was launched on December 2, 1995, for what was originally planned as a two-year mission. Ten years later, it’s still going strong. SOHO was designed to study the internal structure of the Sun, its extensive outer atmosphere and the origin of the solar wind, the stream of highly ionized gas that blows continuously outward through the Solar System.

1997 – The Advanced Composition Explorer, ACE, was launched on August 25, 1997 from the Kennedy Space Center in Florida. ACE orbits the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth. ACE performs measurements over a wide range of energy and nuclear mass, under all solar wind flow conditions and during both large and small particle events including solar flares. ACE provides near-real-time solar wind information over short time periods. When reporting space weather ACE can provide an advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and present a hazard to astronauts.

2001 – Shawn Korgan forms the VLF_Group on Yahoo. The Natural Radio VLF group is a discussion group dedicated to those who enjoy monitoring radio frequencies in the VLF radio spectrum and slightly below the VLF (very low frequency) spectrum (3-30 KHz). Mark Karney takes over ownership of the group in 2002.

2006 – Robert Helliwell’s book, Whistlers and Related Ionospheric Phenomena is re-released as a paperback, 40 years after the original publication.

2008 – Natural Radio Lab website is officially launched in January.

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