Atmospheric noise is

radio noise In radio reception, radio noise (commonly referred to as radio static) is unwanted random radio frequency electrical signals, fluctuating voltages, always present in a radio receiver in addition to the desired radio signal. Radio noise is a comb ...

, or "static", caused by natural atmospheric processes, primarily

lightning Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on ...

discharges in

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...

s. On a worldwide scale, there are about 40 lightning flashes per second, or lightning discharges per day.

Lightning

Atmospheric noise is radio noise caused by natural atmospheric processes, primarily

discharges in

s. 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. The sum of all these lightning flashes results in atmospheric noise. It can be easily heard with any

AM radio AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmi ...

or SSB receiver tuned to an unused frequency. The heard static is a combination of

white noise In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used with this or similar meanings in many scientific and technical disciplines, i ...

(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 Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave ...

and

low frequency Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre waves. LF radio waves ...

, atmospheric noise often dominates, while at

high frequency High frequency (HF) is the ITU designation for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one ...

, man-made noise dominates in urban areas.

History

Early investigation and study

In 1925,

AT&T Bell Laboratories Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, Murray Hill, New Jersey, the compa ...

started investigating the sources of noise in its transatlantic radio telephone service. 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: # The first (and strongest) source was local thunderstorms. # The second source was weaker noise from more distant thunderstorms. # The third source was a still weaker hiss that turned out to be galactic noise from the center of the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

. Jansky's research made him the "father of

radio astronomy Radio astronomy is a subfield of astronomy that studies Astronomical object, celestial objects using radio waves. It started in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observat ...

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

Later survey data

From 1960s to 1980s, a worldwide effort was made to measure the atmospheric noise and variations. Results have been documented in CCIR Report 322. ; first CCIR Report 322 was 1963
revised first ed.
second is . CCIR 322 provided seasonal world maps showing the expected values of the atmospheric noise figure at 1 MHz during four hour blocks of the day. Another set of charts relates the at 1 MHz to other frequencies. CCIR Report 322 has been superseded by publication of ITU R-RE-P.372.

Random number generation

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 Determinism is the metaphysical view that all events within the universe (or multiverse) can occur only in one possible way. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping mo ...

, true random number generators (TRNGs) can derive randomness from

physical phenomena Physical may refer to: *Physical examination In a physical examination, medical examination, clinical examination, or medical checkup, a medical practitioner examines a patient for any possible medical signs or symptoms of a Disease, medical co ...

. RANDOM.ORG leverages atmospheric noise to generate truly random numbers. It captures atmospheric noise using radios and translates the variations in the

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...

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.

Applications

Cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

: True random numbers are essential for generating secure encryption keys. *

Statistical sampling In this statistics, quality assurance, and survey methodology, sampling is the selection of a subset or a statistical sample (termed sample for short) of individuals from within a statistical population to estimate characteristics of the whole ...

: Ensures

unbiased Bias is a disproportionate weight ''in favor of'' or ''against'' an idea or thing, usually in a way that is inaccurate, closed-minded, prejudicial, or unfair. Biases can be innate or learned. People may develop biases for or against an individ ...

sampling in surveys and experiments. *

Simulations A simulation is an imitative representation of a process or system that could exist in the real world. In this broad sense, simulation can often be used interchangeably with model. Sometimes a clear distinction between the two terms is made, in ...

: Used in Monte Carlo simulations to model complex systems and processes.

Predictability

One challenges in using atmospheric noise for random number generation is the

nature of the

universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...

. Some argue that if we could perfectly understand and measure all the factors influencing atmospheric noise, it might become predictable. However, the

complexity Complexity characterizes the behavior of a system or model whose components interact in multiple ways and follow local rules, leading to non-linearity, randomness, collective dynamics, hierarchy, and emergence. The term is generally used to c ...

of weather systems and the difficulty in measuring variables like the

position Position often refers to: * Position (geometry), the spatial location (rather than orientation) of an entity * Position, a job or occupation Position may also refer to: Games and recreation * Position (poker), location relative to the dealer * ...

and

velocity Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...

of every

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

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.

References

{{Noise Noise (electronics)