Real time monitoring of global magnetic activity : the APEST index

Clarke, Ellen. 2001 Real time monitoring of global magnetic activity : the APEST index. [Poster] In: ESTEC SWW 2001, Noordwijk, The Netherlands, 17-19 December 2001. (Unpublished)

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Real and near real time global geomagnetic activity indices play an important role in Space Weather projects. Knowledge of the most recent activity levels and the current level is a very useful tool in forecasting. The well established and much used 3-hourly planetary index (ap) and the daily planetary index (Ap), which are provided by the International Service of Geomagnetic Indices (ISGI) of the International Association of Geomagnetism and Aeronomy (IAGA), are directly related to the 3-hourly Kp index. By using a network of mid-latitude magnetic observatories for their production, these indices were designed to measure the irregular disturbances of the geomagnetic field caused by solar particle radiation. The definitive Ap values are made available twice per month as soon after the 15th and the last day of the month as possible. A time delay is inevitable because of the need for a high quality homogenous data set. However the process is not sufficiently responsive to the needs of the space weather community, where small discrepancies in the data are less important than their timely availability. Estimates of the ap and Ap indices, called apest and Apest respectively, are routinely derived and continuously updated by the British Geological Survey (BGS) and are available on-line in real time. This paper describes the derivation process of these indices, which has been designed to match that of the definitive indices as closely as possible. In order to do this estimates are derived using data from as many of the official Kp magnetic observatories as possible. The data are collected from various locations making use of INTERMAGNET data as far as possible. Estimates of the local 3-hourly K-indices are made for each observatory, the derivation for which depends on the type of data available. These are then used to calculate ap est and Ap est , by using the same method as that for the definitive indices. A review of how well Ap est corresponds to definitive Ap with respect to the time of availability on-line is presented. Similar estimated planetary indices (3-hourly Kp and daily Ap) are available in near real time from the Space Environment Center (SEC). These estimates are derived using data from magnetic observatories in North America. Comparisons have been carried out to show the benefits of having a wider global coverage, when attempting to produce a global index.

Item Type: Publication - Conference Item (Poster)
Programmes: BGS Programmes > Seismology and Geomagnetism
NORA Subject Terms: Earth Sciences
Date made live: 26 Nov 2012 13:31 +0 (UTC)

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