The K -index quantifies disturbances in the horizontal component of Earth's magnetic field with an integer in the range 0–9 with 1 being calm and 5 or more indicating a geomagnetic storm . It is derived from the maximum fluctuations of horizontal components observed on a magnetometer during a three-hour interval. The label K comes from the German word Kennziffer meaning " characteristic digit ". The K -index was introduced by Julius Bartels in 1939.
9-445: 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
18-411: 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
27-419: 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
36-558: 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,
45-410: 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
54-435: 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
63-525: 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- Too Many Requests If you report this error to the Wikimedia System Administrators, please include
72-409: 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
81-700: 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
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