Open AccessSolar cycle variations in the storm‐substorm relationship
Author(s) -
Nakai H.,
Kamide Y.
Publication year - 1999
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/1999ja900278
Subject(s) - solar wind , physics , substorm , sunspot , solar cycle , interplanetary magnetic field , solar cycle 22 , linear regression , solar maximum , atmospheric sciences , geomagnetic storm , solar minimum , interplanetary spaceflight , wind speed , meteorology , environmental science , mathematics , magnetic field , statistics , magnetosphere , quantum mechanics
The regression coefficients of the time‐weighted AL index ( AL W ) to the Dst index are calculated for each year from 1966 to 1994. It is found that the slope of the linear regression equation varies over a period of 11 years: The coefficient a 1 in a regression equation, Dst = a 0 + a 1 AL W , is maximized near the sunspot maximum and is minimized near the sunspot minimum. The long‐term variations in the relationship between these indices and solar wind parameters are also examined. The dependence of Dst on the solar wind electric flux, B z V 2 , is nearly constant, while the values of AL for fixed values of B z V 2 are greater at the solar minimum than at the solar maximum, where B z and V denote the Z component of the interplanetary magnetic field and the solar wind speed, respectively. Possible causes that can account for these characteristics are discussed.