Atmospheric noise

Atmospheric noise is radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms. It is mainly caused by cloud-to-ground flashes as the current is much stronger than that of cloud-to-cloud flashes.

On a worldwide scale, 3.5 million lightning flashes occur daily. That means there are about 40 lightning flashes per second.

{{cite report

|first1 = Arthur D. |last1 = Spaulding

|first2 = James S. |last2 = Washburn

|date = April 1985

|title = Atmospheric Radio Noise: Worldwide levels and other characteristics

|id = NTIA Report TR-85-173

|place = Boulder, CO

|publisher = U.S. Department of Commerce, National Telecommunications & Information Administration, Institute for Telecommunications Sciences

|series = NASA Sti/Recon Technical Report N

|volume = 86 |page= 13639

|bibcode = 1985STIN...8613639S

|url = https://its.ntia.gov/publications/details.aspx?pub=2196

}}

The sum of all these lightning flashes results in atmospheric noise. It can be easily heard with any AM radio or SSB receiver tuned to an unused frequency.

{{cite AV media

|title=Sample of atmospheric noise

|medium=audio recording

|format=MP3

|website=ycars.org

|publisher=York County Amateur Radio Society

|place=York County, PA

|url=http://www.ycars.org/EFRA/audio%20files/atmospheric%20noise.mp3

|access-date=2008-03-14 |url-status=dead

|archive-url=https://web.archive.org/web/20051218032644/http://www.ycars.org/EFRA/audio%20files/atmospheric%20noise.mp3

|archive-date=2005-12-18

}}

The heard static is a combination of white noise (cumulative of distant thunderstorms) and impulse noise (from relatively nearby thunderstorms, if any). The power-sum varies with seasons and nearness of thunderstorm centers. It can be seen as random speckles on an old analog TV set dialed to an empty channel.

Although lightning has a broad-spectrum emission, its noise power increases with decreasing frequency. Therefore, at very low frequency and low frequency, atmospheric noise often dominates, while at high frequency, man-made noise dominates in urban areas.

Image:Janksy Karl radio telescope.jpg.{{coord|38.431659|-79.816253|dim:100}}]]

In 1925, AT&T Bell Laboratories started investigating the sources of noise in its transatlantic radio telephone service.

{{cite book

|first = Simon |last = Singh |author-link = Simon Singh

|year = 2005

|title = Big Bang: The Origin of the Universe

|publisher = Harper Perennial

|isbn = 978-0-00-716221-5

}}

{{rp|style=ama|pp= 402–408}}

Then a 22 year-old researcher, K.G. Jansky undertook the task in 1928. By 1930, a radio antenna for a wavelength of 14.6 meters was constructed in Holmdel, NJ, to measure the noise in all directions. Jansky recognized three sources of radio noise:{{rp|style=ama|pp= 404–405}}

1. The first (and strongest) source was local thunderstorms.
2. The second source was weaker noise from more distant thunderstorms.
3. The third source was a still weaker hiss that turned out to be galactic noise from the center of the Milky Way.

Jansky's research made him the "father of radio astronomy".{{rp|style=ama|p= 406}}

In early 1950s, S.V.C. Aiya published a mathematical model of the cumulative effects of lightning and thunderstorms on broadcasting.

{{cite journal

|last=Aiya |first=S.V.C. |author-link=S. V. C. Aiya

|date=December 1956

|title=Noise radiation from tropical thunderstorms in the standard broadcast band

|journal=Nature

|volume=178 |issue=4544 |page=1249

|doi=10.1038/1781249a0 |doi-access=free

|bibcode=1956Natur.178.1249C |s2cid=186242557

|lang=en

}}

From 1960s to 1980s, a worldwide effort was made to measure the atmospheric noise and variations. Results have been documented in CCIR Report 322.

{{cite report

|title = Characteristics and Applications of Atmospheric Radio Noise Data

|year = 1968

|series = International Radio Consultative Committee (CCIR)

|place = Geneva, CH

|publisher = International Telecommunication Union (ITU)

|id = CCIR Report 322-3

}}; first CCIR Report 322 was 1963; [https://books.google.com/books?id=1ls2AQAAIAAJ revised first ed.]; second is {{ISBN|92-61-01741-X}}.

{{cite report

|last = Lawrence |first = D.C.

|date = June 1995

|title = Noise Variation Parameters

|department = CCIR Report 322

|place = San Diego, CA

|publisher = U.S. Naval Command, Control and Ocean Surveillance Center, RDT&E Division

|id = NRaD Technical Document 2813

|url = http://www.spawar.navy.mil/sti/publications/pubs/td/2813

|url-status = dead

|archive-url = https://web.archive.org/web/20091113023506/http://www.spawar.navy.mil/sti/publications/pubs/td/2813/

|archive-date = 2009-11-13

}}

: alt source

{{cite web

|title = DTIC ADA298722

|website = oai.dtic.mil

|url = http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA298722

|archive-url = https://web.archive.org/web/20150925131632/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA298722

|archive-date = 2015-09-25

}}

CCIR 322 provided seasonal world maps showing the expected values of the atmospheric noise figure {{mvar|F}}{{sub|a}} at 1 MHz during four hour blocks of the day. Another set of charts relates the {{mvar|F}}{{sub|a}} at 1 MHz to other frequencies. CCIR Report 322 has been superseded by publication of ITU R-RE-P.372.

{{cite report

|title = Radio Noise

|series = ITU Recommendation

|place = Geneva, CH

|publisher = International Telecommunication Union (ITU)

|id = R-RE-P.372

|url = http://www.itu.int/rec/R-REC-P.372/en

|via=ITU.int

}}

Atmospheric noise and variation is also used to generate high quality random numbers. Unlike pseudorandom number generators (PRNGs), which use algorithms and are inherently deterministic, true random number generators (TRNGs) can derive randomness from physical phenomena.

{{cite web

|last = Haahr |first = Mads

|title = Introduction to randomness and random numbers

|website = random.org

|access-date = 14 November 2011

|url = http://www.random.org/randomness/

|type = self-published

}}

RANDOM.ORG leverages atmospheric noise to generate truly random numbers. It captures atmospheric noise using radios and translates the variations in the amplitude of this noise into a stream of random numbers. Unlike PRNGs, which rely on mathematical formulas, the numbers generated through atmospheric noise are not predetermined.

• Cryptography: True random numbers are essential for generating secure encryption keys.
• Statistical sampling: Ensures unbiased sampling in surveys and experiments.
• Simulations: Used in Monte Carlo simulations to model complex systems and processes.

One challenges in using atmospheric noise for random number generation is the deterministic nature of the universe. Some argue that if we could perfectly understand and measure all the factors influencing atmospheric noise, it might become predictable. However, the complexity of weather systems and the difficulty in measuring variables like the position and velocity of every molecule make it practically impossible to predict these numbers. For this reason, even if atmospheric noise is theoretically predictable, it is practically unpredictable, making it useful for generating random numbers.

• radio atmospheric
• radio interference
• radio noise

{{reflist|25em}}

{{Noise}}

Category:Noise (electronics)