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29-445: The K -scale is a quasi-logarithmic scale derived from the maximum fluctuation R  (in units of nano teslas , nT) in the horizontal component of Earth's magnetic field observed on a magnetometer relative to a quiet day during a three-hour interval. The conversion table from maximum fluctuation to K -index varies from observatory to observatory in such a way that the historical rate of occurrence of certain levels of K are about

58-687: A non-serious fashion , in May 2010. Ian Mills, president of the Consultative Committee on Units, considered the chances of official adoption to be remote. The prefix geop and term "geopbyte" have been used in the information technology industry to refer to 10 bytes, following "brontobyte". The ascending prefixes peta ( 1000 ) and exa ( 1000 ) are based on the Greek-derived numeric prefixes "penta" (5) and "hexa" (6). The largest prefixes zetta ( 1000 ), and yotta ( 1000 ) and, similarly,

87-504: A prefix for something other than a unit of measure (as for example in words like "nanoscience"), nano refers to nanotechnology , or means "on a scale of nanometres" ( nanoscale ). X-rays have a wavelength ranging from the size of 0.01 nm to 10 nm. Human fingernails grow at approximately one nanometer per second. A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of

116-697: A second , that is, ⁠ 1 / 1 000 000 000 ⁠ of a second, or 10 seconds. The term combines the SI prefix nano- indicating a 1 billionth submultiple of an SI unit (e.g. nanogram, nanometre , etc.) and second , the primary unit of time in the SI. A nanosecond is to one second, as one second is to approximately 31.69 years. A nanosecond is equal to 1000  picoseconds or ⁠ 1 / 1000 ⁠   microsecond . Time units ranging between 10 and 10 seconds are typically expressed as tens or hundreds of nanoseconds. Unit prefix A unit prefix

145-501: A few unofficial prefixes appeared on the Internet: hepa (10 ), ento (10 ), otta (10 ), fito (10 ), nea (10 ), syto (10 ), dea (10 ), tredo (10 ), una (10 ) and revo (10 ). The Oxford professor Jeffrey K. Aronson has suggested extending beyond zetta/zepto and yotta/yocto with xenta/xenno , wekta/weko , vendeka/vendeko , and udeka/udeko , based on the idea that the "Z" and "Y" prefixes would continue backwards through

174-420: A given unit has often arisen by convenience of use and historical developments. Unit prefixes that are much larger or smaller than encountered in practice are seldom used, albeit valid combinations. In most contexts only a few, the most common, combinations are established. For example, prefixes for multiples greater than one thousand are rarely applied to the gram or metre. Some prefixes used in older versions of

203-553: A narrow set has been recognised by standards organisations. The prefixes of the metric system precede a basic unit of measure to indicate a decadic multiple and fraction of a unit. Each prefix has a unique symbol that is prepended to the unit symbol. Some of the prefixes date back to the introduction of the metric system in the 1790s, but new prefixes have been added, and some have been revised. The International Bureau of Weights and Measures has standardised twenty metric prefixes in resolutions dating from 1960 to 1991 for use with

232-518: Is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units of various sizes are commonly formed by the use of such prefixes . The prefixes of the metric system , such as kilo and milli , represent multiplication by positive or negative powers of ten. In information technology it is common to use binary prefixes , which are based on powers of two . Historically, many prefixes have been used or proposed by various sources, but only

261-437: Is formed from the first syllable of the decimal prefix with the similar value, and the syllable "bi". The symbols are the decimal symbol, always capitalised, followed by the letter "i". According to these standards, kilo , mega , giga , et seq. should only be used in the decimal sense, even when referring to data storage capacities: kilobyte and megabyte denote one thousand and one million bytes respectively (consistent with

290-411: Is not meaningful to take the average of a set of K -indices directly. Instead each K is converted back into a linear scale. The A -index is the daily average of amplitude for geomagnetic activity at a specific magnetometer station, derived from the eight (three hourly) a -indices. The A p -index is the averaged planetary A -index based on data from a set of specific K p stations. If

319-419: Is the strongest (corresponding to a K p value of 9). (900 days per cycle) (360 days per cycle) (130 days per cycle) (60 days per cycle) (4 days per cycle) The K p -index is used for the study and prediction of ionospheric propagation of high frequency radio signals. Geomagnetic storms, indicated by a K p  = 5 or higher, have no direct effect on propagation. However they disturb

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348-548: The F-layer of the ionosphere , especially at middle and high geographical latitudes, causing a so-called ionospheric storm which degrades radio propagation. The degradation mainly consists of a reduction of the maximum usable frequency (MUF) by as much as 50%. Sometimes the E-layer may be affected as well. In contrast with sudden ionospheric disturbances (SID), which affect high frequency radio paths mostly at mid and low latitudes,

377-568: The International System of Units (SI). In addition to those listed in the everyday-use table, the SI includes standardised prefixes for 10 ( peta ), 10 ( exa ), 10 ( zetta ), 10 ( yotta ), 10 ( ronna ), and 10 ( quetta ); and for 10 ( femto ), 10 ( atto ), 10 (zepto), 10 ( yocto ), 10 ( ronto ), and 10 ( quecto ). Although formerly in use, the SI disallows combining prefixes; the * microkilogram or * centimillimetre , for example, are not permitted. Prefixes corresponding to powers of one thousand are usually preferred, however, units such as

406-410: The K -indices for the day were 3, 4, 6, 5, 3, 2, 2 and 1, the daily A -index is the average of the equivalent amplitudes: The NOAA G-scale describes the significance of effects of a geomagnetic storm to the public and those affected by the space environment. It is directly derived from the K p -scale, where G1 is the weakest storm classification (corresponding to a K p value of 5) and G5

435-558: The byte . Units of information are not covered in the International System of Units. Computer professionals have historically used the same spelling, pronunciation and symbols for the binary series in the description of computer memory , although the symbol for kilo is often capitalised. For example, in citations of main memory or RAM capacity, kilobyte , megabyte and gigabyte customarily mean 1024 (2 ), 1 048 576 (2 ) and 1 073 741 824 (2 ) bytes respectively. In

464-457: The metric system , this prefix denotes a factor of 10 or 0.000 000 001 . It is frequently encountered in science and electronics for prefixing units of time and length . The prefix derives from the Greek νᾶνος (Latin nanus ), meaning "dwarf". The General Conference on Weights and Measures (CGPM) officially endorsed the usage of nano as a standard prefix in 1960. When used as

493-435: The 3 hour period are added together to determine the total maximum fluctuation. These maximum deviations may occur any time during the 3 hour period. The official planetary K p -index is derived by calculating a weighted average of K -indices from a network of 13 geomagnetic observatories at mid-latitude locations. Since these observatories do not report their data in real-time, various operations centers around

522-450: The descending prefixes zepto ( 1000 ) and yocto ( 1000 ) are derived from Latin "septem" (7) and " octo" (8) plus the initial letters "z" and "y". The initial letters "z" and "y" appear in the largest SI prefixes. They were changed because of previously proposed ascending hepto (Greek "hepta" (7)) was already in use as a numerical prefix (implying seven) and the letter "h" as both SI-accepted non-SI unit (hour) and prefix ( hecto 10 ),

551-424: The effects of ionospheric storms are more intense at high latitudes and the polar regions. [REDACTED]  This article incorporates public domain material from the United States Government [REDACTED]  This article incorporates public domain material from the United States Government Nano- Nano (symbol n ) is a unit prefix meaning one billionth . Used primarily with

580-409: The globe estimate the index based on data available from their local network of observatories. The K p -index was introduced by Bartels in 1939. The a -index is the three hourly equivalent amplitude for geomagnetic activity at a specific magnetometer station derived from the station-specific K -index. Because of the quasi-logarithmic relationship of the K -scale to magnetometer fluctuations, it

609-557: The hectopascal, centimetre, and centilitre, are widely used; outside the SI, the units hectare , decibel are also common. The unit prefixes are always considered to be part of the unit, so that, e.g., in exponentiation , 1 km means one square kilometre, not one thousand square metres, and 1 cm means one cubic centimetre, not one hundredth of a cubic metre. In general, prefixes are used with any metric unit, but may also be used with non-metric units. Some combinations, however, are more common than others. The choice of prefixes for

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638-453: The metric system are no longer used. The prefixes myria- , (from the Greek μύριοι , mýrioi ), double- and demi- , denoting factors of 10 000 , 2 and 1 ⁄ 2 respectively, were parts of the original metric system adopted in France in 1795, but they were not retained when the SI prefixes were agreed internationally by the 11th CGPM conference in 1960. The prefix " myrio- "

667-642: The metric system), while terms such as kibibyte , mebibyte and gibibyte , with symbols KiB, MiB and GiB, denote 2 , 2 and 2 bytes respectively. Although some of the following unofficial prefixes appear repeated on the internet, no one is in actual use. A metric prefix myria (abbreviation "my"), for 10,000, was deprecated in 1960. Before the adoption of ronna and quetta for 10 and 10 and ronto and quecto for 10 and 10 in November 2022, many personal, and sometimes facetious, proposals for additional metric prefixes were formulated. The prefix bronto , as used in

696-704: The same applied to "s" from previously proposed descending septo (i.e. SI unit "s", seconds), while "o" for octo was problematic since a symbol "o" could be confused with zero. Before the adoption of new prefixes in 2022, several personal proposals had been made for extending the series of prefixes, with ascending terms such as xenna , weka , vendeka (from Greek "ennea" (9), "deka" (10), "endeka" (11)) and descending terms such as xono , weco , vundo (from Latin "novem"/"nona" (9), "decem" (10), "undecim" (11)). Using Greek for ascending and Latin for descending would be consistent with established prefixes such as deca , hecto , kilo vs. deci , centi , milli . In 2001,

725-686: The same at all observatories. In practice this means that observatories at higher geomagnetic latitude require higher levels of fluctuation for a given K -index. For example, the corresponding R value for K = 9 is 1500  nT in Godhavn, Greenland , 300  nT in Honolulu, Hawaii and 500  nT in Kiel, Germany . The real-time K -index is determined after the end of prescribed intervals of 3 hours each: 00:00–03:00, 03:00–06:00, ..., 21:00–24:00. The maximum positive and negative deviations during

754-556: The seller. (see Orin Safier v. Western Digital Corporation and Cho v. Seagate Technology (US) Holdings, Inc. ). To protect themselves, some sellers write out the full term as " 1 000 000 ". With the aim of avoiding ambiguity the International Electrotechnical Commission (IEC) adopted new binary prefixes in 1998 ( IEC 80000-13:2008 formerly subclauses 3.8 and 3.9 of IEC 60027-2:2005 ). Each binary prefix

783-419: The specifications of hard disk drive capacities and network transmission bit rates , decimal prefixes are used. For example, a 500-gigabyte hard drive holds 500 billion bytes, and a 100-megabit-per-second Ethernet connection transfers data at 100 million bits per second. The ambiguity has led to some confusion and even lawsuits from purchasers who were expecting 2 or 2 and considered themselves shortchanged by

812-474: The term "brontobyte", has been used to represent anything from 10 to 10 bytes, most often 10 . In 2010, an online petition sought to establish hella- as the SI prefix for 10 , a movement that began on the campus of UC Davis . The prefix, which has since appeared in the San Francisco Chronicle , Daily Telegraph , Wired and some other scientific magazines, was recognised by Google , in

841-410: Was an alternative spelling variant for " myria- ", as proposed by Thomas Young . A binary prefix indicates multiplication by a power of two. The tenth power of 2 (2 ) has the value 1024 , which is close to 1000 . This has prompted the use of the metric prefixes kilo , mega , and giga to also denote the powers of 1024 which is common in information technology with the unit of digital information,

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