Open AccessA physics‐based study of the Dst ‐ AL relationship
Author(s) -
Shen Chao,
Liu Zhenxing,
Kamei Toyohisa
Publication year - 2002
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 - 10.1029/2001ja900121
Subject(s) - ring current , substorm , physics , electrojet , solar wind , particle acceleration , geomagnetic storm , function (biology) , magnetosphere , magnetic field , computational physics , earth's magnetic field , quantum mechanics , evolutionary biology , biology
Understanding the storm‐substorm relationship is an important problem in magnetospheric dynamics. In the past this question has been explored using statistical techniques and empirical relationships involving the Dst and AE / AL indices. In this research we have developed a relationship between AL and Dst based on the physics of the process. We argue that the magnetospheric electric field causes both the westward auroral electrojet and the particle injection into the ring current region. The adiabatic acceleration of ring current particles and the thermal properties of the ring current source have been included in the calculations. The injection function deduced is found to be a function of AL index and the solar wind dynamical pressure P dyn . For AL > AL 0 (∼−500 nT) the injection function is proportional to AL [ P dyn ( t − t d )] 0.33 with a time lag t d ≈ 45 min; while for large AL < AL 0 (∼−500 nT) the injection function is proportional to −| AL | 1.7 [ P dyn ( t − t d )] 0.33 . This result is consistent with previous statistical results. We also find that the ring current decay time is a function of AL . Finally, we obtain an algorithm which predicts Dst from AL and the solar wind dynamical pressure P dyn . The correlation coefficients between Dst predicted by the algorithm and the observed Dst index are 0.84 and 0.80 for the years 1998 and 1999, respectively.