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Statistical studies of an effective sunspot number
Author(s) -
Secan J. A.,
Wilkinson P. J.
Publication year - 1997
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/97rs01350
Subject(s) - sunspot number , sunspot , ionosphere , space weather , critical frequency , meteorology , earth's magnetic field , environmental science , mathematics , solar cycle , physics , computer science , solar wind , geophysics , magnetic field , quantum mechanics
Two decades ago, the U.S. Air Force Air Weather Service space forecasting group began generating what was termed an effective sunspot number (SSN e ) by fitting a model of the critical frequency of the F 2 layer (ƒ o F 2 ) to observedƒ o F 2 values. Initially a preprocessing step in a larger analysis package, this parameter has taken on a life of its own and is now used in various applications for both forecasts and specification of the globalƒ o F 2 field. This paper describes the various ways in which this parameter is calculated, investigates the behavior of this parameter over solar cycle 21 (1976 through 1986), and compares it with other solar‐ionospheric indices, including R 12 , IF 2 , IG , and the Ionospheric Prediction Service (IPS) T index.