Solar wind coupling to and predictability of ground magnetic fields and their time derivatives

Abstract

[1] A spatial and dynamic study of solar wind driving of high-latitude ground magnetic fields and their time derivatives is given. Nonlinear, data-derived basis functions are used to determine the optimal solar wind driven dynamic coupling function at high-latitude locations. The method does not assume a solar wind driving function a priori so that an unbiased determination of the relative influence of different driving processes can be made. Using this method, the locations where high-latitude models capture signatures of different driving processes, such as reconnection and the Kelvin-Helmholtz instability, are revealed for both the amplitude of the field and its time derivative. The time rate of change of the field is a disturbance measure related to geomagnetically induced currents. For the amplitude of the ground magnetic field the primary driver is reconnection; the time rate of change of the field has signatures of both reconnection driving in the nightside sector and Kelvin-Helmholtz driving in the prenoon sector. The independent influence of the solar wind ion density and azimuthal component of the magnetic field in driving magnetic field fluctuations is found to be small at auroral-zone latitudes. The data-derived coupling functions are also used to estimate the expected prediction error of a general class of models that specify the ground magnetic field or its time derivative given solar wind plasma measurements. Prediction efficiencies as small as zero and as large as 0.7 for both the amplitude of the field and its time derivative are possible. The prediction efficiency is highly dependent on spatial location and the direction of field being predicted.

Climatology of rapid geomagnetic variations at high latitudes over two solar cycles

“…Weigel et al (2003) studied separately different solar wind parameters to estimate how much influence they have on explaining variations of the northward magnetic field and its time derivative (X and dX/dt) in the region of IMAGE magnetometers. They found that the process that drives X is different from that which drives dX/dt.…”

Relation between substorm characteristics and rapid temporal variations of the ground magnetic field

“…The surface grid could be quite sparse (of a 100-km scale), but it would be critical to predict dB/dt accurately, especially concerning the largest values. Weigel et al (2003) has attempted to forecast the 30-min average absolute magnitude of dB/dt directly from solar wind observations. The highest prediction efficiencies achieved are about 0.7.…”

Editorial retraction: “Estimation of ground magnetic field variations using solar wind parameters and magnetic indices,” by Claire M. Delides

“…The combination of solar wind velocity, v x with the IMF as v x B z has received some attention. For example, Weigel et al [2003] showed a significant correspondence between the ground north-south magnetic field variation at auroral latitudes with v x B z and demonstrated that this depended on magnetometer location.…”