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This manual describes the necessary procedures for assuring continuous lightning sferics data collection at Marshall Space Flight Center. The phase linear interferometer experiment is under evaluation as a candidate RF sensor to support the space based optical lightning mapper system.

A rocket-borne payload, carrying both vertical and horizontal magnetic dipole antennas and receiving instrumentation, was flown from Wallops Island, Virginia, to observe the Transverse Electric (TE) and Transverse Magnetic (TM) polarization components of individual sferics at 30 kHz. During the 2-1/2 min flight to apogee at 96 km, 293 individual sferics were observed. Upon applying corrections for difference in azimuthal antenna patterns, it was concluded that the TM noise fields were larger than the TE fields by about 15 dB near the ground, and approximately equal at 60 km. (Author)

Recording VLF from up on the mountain.

Electromagnetic pulse signals from certain classes of nuclear events, in terms of burst and distance, have features which afford a means of recognition. Similar features are also observed in atmospherics, but these have a smaller normalized source function amplitude. An experiment was conducted to investigate the feasibility of measuring the distance to nearby sferics using azimuth and amplitude data observed at two sites separated by a few kilometers. Knowledge of the distance to the source and the observed amplitude would permit calculation of the normalized source function amplitude which might be used as a discriminant. Data were also collected on the frequency of simultaneous (within equipment and propagation delay) observation at both sites, of signals exceeding 10 V/m amplitude 10 V/m/microsec rate of rise which persisted for one microsecond or less. Transients from lightning would not be expected to meet these criteria over propagation distances of more than a few kilometers.

Journal of Research of the National Bureau of Standards

Distributions were developed for 1972 in the Eastern Hemisphere of thunderstorm days (january, April, July, and October), the incidence of lightning discharge (january and April), and the areal concentration of lightning discharge (yearly). These analyses were based on a review of sferics data. Charts of thunderstorm days differed significantly from mean charts of the World Meteorological Organization (WMO), especially over the oceans, North Africa, Arabia, the Mediterranean Sea, and Southeast China. These areas of sparse data in the WMO compilation have been covered in this investigation. The tentative, first estimate of the distribution of lightning discharges over a large area of Earth differed significantly from the distribution of thunderstorm days for April and July, but the two distributions were similar for January and October. Centers of relatively high occurrence of lightning discharge on a yearly basis were located over South Africa, the Mediterranean Sea, Arabia, Southeast China, Southeast Asia, and Australia. The occurrence of lightning discharge was shown to follow Sun northward from January to the maximum poleward thrust in July. The occurrence of lightning discharge receded equatorward from July to the end of fall in December. The most reliable planetary-scale estimate of the average incidence of lightning discharge was 0.000042 per km per sec for the Northern Hemisphere (0-179E) in January 1972 and 0.000030 per km per sec for April 1972.

The described AFCRC experimental 'hyperbolic direction finder' consists of an array of sferic receivers in the New England area, connected by wide-band data links so that microsecond differences in pulse arrival time can be measured. The hyperbolic directions can be determined from the time differences. In a series of coordinated runs, individual sferics originating in western Europe were observed by both the New England net and the sferics net of the British Meteorological Office. The BMO furnished the geographic coordinates of the lightning strokes so that measurements of position could be compared. Tabulated results for 150 sferics show an average absolute deviation from the mean of only 31 nautical miles.

The described AFCRC experimental 'hyperbolic direction finder' consists of an array of sferic receivers in the New England area, connected by wide-band data links so that microsecond differences in pulse arrival time can be measured. The hyperbolic directions can be determined from the time differences. In a series of coordinated runs, individual sferics originating in western Europe were observed by both the New England net and the sferics net of the British Meteorological Office. The BMO furnished the geographic coordinates of the lightning strokes so that measurements of position could be compared. Tabulated results for 150 sferics show an average absolute deviation from the mean of only 31 nautical miles.

          * Auroral Chorus V: Sferics Anthology & Radio DX -- 1989 to 2021 * This page contains ongoing natural ELF-VLF radio field-recordings and also other "DX" radio recordings in mono and stereo between 1989 to throughout 2021, by Stephen P. McGreevy - N6NKS. All of the ELF-VLF recordings pertain to lightning "atmospherics" or "sferics" as lightning is a huge part of natural ELF-VLF radio emissions in the AudioBand. Many of the radio-DX recordings 2015 to 2020 also contain lightning-impulse "static" in them as well:  (lightning-stroke energy is very "broadband" - i.e. from "DC  to Light").   Our planet Earth is alive with this vast amount of natural-electricity in the form of lightning stroke/strike electromagnetic emissions and these can also be considered "primordial radio emissions."   Every lightning bolt within 3,000 miles or about 5,000 km of the VLF receiver creates a pop or a crackle in a VLF receiver's audio output, especially at these AUDIO-frequency radio-waves. Because lightning storms produce vast amounts of radio energy at VLF frequencies, the World-Wide Lightning Location Network (wwlln.net) employs VLF receivers to direction-find and map lightning strokes via the very VLF signals presented herein. The majority of natural VLF radio audio files on this page are in STEREO employing my WR-9STL dual-loop receiver. In the stereo (dual-loop/orthogonally-oriented) natural VLF radio recordings on this page, you can hear the directionality of the two VLF-loop antennas and the stereo-effects because of the differing directions that all of the lightning "sferics" are originating from - whether cloud-to-cloud lightning (sometimes creating multi-burst lightning strings), to clear pops of ground strikes. Maybe many of the lightning bolts making a sferic also launch Sprites toward the ionosphere! I am fascinated by lightning and associated electromagnetic-emissions of lightning (and they spawn whistlers occasionally, too) as much as the other sounds of Earth's natural-VLF-radio phenomena such as whistlers and dawn-chorus. Lightning static - also called "atmospherics" or "sferics" - can be interesting to listen to, and I am undertaking the project of stereophonic recording of lightning sferics with a dual, cross-azimuth loop-antenna receiving system. The sounds of sferics in stereo are quite beautiful! A particularly beautiful stereo tweek/whistler recording is the 33 minute track/23 August 2012/0745UT file (recorded in Inyo County, California) to the right or downloadable links below. What causes the "ringyness" or "pingyness" of lightning atmospherics/sferics (at nighttime) is caused by the lowest layers of the ionosphere and Earth's surface and also Ocean surfaces forming a kind-of "waveguide" that enhances the approximately 1.7 kHz (+/- 200 Hz) audio-frequencies of these electromagnetic signals. They are called "Tweeks." (They are not EQ signals as some have assumed). Tweeks can always sound pretty and enjoyable when other VLF emissions from up farther within the Magnetosphere fail to occur. Like raindrops on a rooftop, the sounds of Tweeks can be soothing to some. Whistlers are precipitated by lightning strokes as you will hear in all of these amazing and beautiful recordings. Enjoy! In March 2015 I uploaded several tracks that contain compilation-edits of various natural VLF radio field-recording expeditions to locations in Canada and Alaska within the auroral-zone (where aurora are most frequently visible). Auroral-zone locations of Earth can be considered "VLF hot-spots." ----- Update October 2016: I have uploaded several California-desert medium-wave DX files (in addition to other interesting MF-HF DXing files) of STEREO broadband MW/AM band DX made either via 2 independent wire antennas or 2 orthogonal/cross-azimuth 7-turn deltoid-loops - the audio-sounds of this MW/AM diversity-reception is amazing! This new receiver is based upon two TA7642 AM radio ICs. (bandwidth of each receiver channel occupies 3 to 4 BCB channels (i.e. about 40-50 kHz wide). See enclosed photos on this page - links to the right. SpM 07 October 2016. ----- Stephen P. McGreevy - N6NKS - Updated 06 November 2017 -- ADDITIONS: A few chosen compilations of other field-recordings of awesome VLF sounds from much higher geo-magnetic latitude locations (northern Alberta, Canada June 1996) have been added to this album here at Internet Archives. In you listen to the Alberta June 1996 recordings, you will likely notice that many of the quite bizzarre natural radio sounds are initiated by the pop and crash of lightning strokes. SpM

The results of two methods of obtaining timely and accurate severe weather presentations in the cockpit are detailed. The first method described is a course up display of uplinked weather radar data. This involves the construction of a demonstrator that will show the feasibility of producing a course up display in the cockpit of the NASA simulator at Langley. A set of software algorithms was designed that could easily be implemented, along with data tapes generated to provide the cockpit simulation. The second method described involves the uplinking of sferic data from a ground based 3M-Ryan Stormscope. The technique involves transfer of the data on the CRT of the Stormscope to a remote CRT. This sferic uplink and display could also be included in an implementation on the NASA cockpit simulator, allowing evaluation of pilot responses based on real Stormscope data.

The Fermi Gamma-ray Burst Monitor (GBM) has been detecting TGFs with increasing sensitivity over the past two years, owing to changes in flight software that have lowered its threshold for triggering and, recently, allowed a search for TGFs weaker than those which would cause an onboard trigger. Associations between TGFs detected in the first 18 months of operation and sferics detected using the World Wide Lightning Location Network (WWLLN) show that TGF peaks and lightning discharges are simultaneous to within tens of microseconds, and that GBM triggered on TGFs that occurred up to a distance of 300 km from the sub-spacecraft position. In the work presented here, we look for associations between TGFs detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and WWLLN sferics over the same 18 months, and we compare the match rate and detection horizon of the two instruments. We also look for associations between WWLLN sferics and more recent GBM TGFs, both triggered events and weaker TGFs uncovered in our untriggered search. We discuss whether in this new mode, GBM is detecting TGFs that are more distant from the sub-spacecraft point than 300 km, or whether the weaker TGFs are instead indicative of a luminosity distribution, either because the weaker ones originate deeper in the atmosphere or because they are intrinsically dimmer.

The Fermi Gamma-ray Burst Monitor (GBM) has been detecting TGFs with increasing sensitivity over the past two years, owing to changes in flight software that have lowered its threshold for triggering and, recently, allowed a search for TGFs weaker than those which would cause an onboard trigger. Associations between TGFs detected in the first 18 months of operation and sferics detected using the World Wide Lightning Location Network (WWLLN) show that TGF peaks and lightning discharges are simultaneous to within tens of microseconds, and that GBM triggered on TGFs that occurred up to a distance of 300 km from the sub-spacecraft position. In the work presented here, we look for associations between TGFs detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and WWLLN sferics over the same 18 months, and we compare the match rate and detection horizon of the two instruments. We also look for associations between WWLLN sferics and more recent GBM TGFs, both triggered events and weaker TGFs uncovered in our untriggered search. We discuss whether in this new mode, GBM is detecting TGFs that are more distant from the sub-spacecraft point than 300 km, or whether the weaker TGFs are instead indicative of a luminosity distribution, either because the weaker ones originate deeper in the atmosphere or because they are intrinsically dimmer.

The properties of sferics (the electric and magnetic fields generated by electrified clouds and lightning flashes) are briefly surveyed; the source disturbance and the influence of propagation being examined. Methods of observing sferics and their meteorological implications are discussed. It is concluded that close observations of electrostatic and radiation fields are very informative, respectively, upon the charge distribution and spark processes in a cloud; that ground-level sferics stations can accurately locate the positions of individual lightning flashes and furnish valuable knowledge on the properties of the discharges; but that satellite measurements only provide general information on the level of thundery activity over large geographical regions.