Magnetic field power spectra and magnetic radial diffusion coefficients using CRRES magnetometer data

We used the fluxgate magnetometer data from Combined Release and Radiation Effects Satellite (CRRES) to estimate the power spectral density (PSD) of the compressional component of the geomagnetic field in the ∼1 mHz to ∼8 mHz range. We conclude that magnetic wave power is generally higher in the noon sector for quiet times with no significant difference between the dawn, dusk, and the midnight sectors. However, during high Kp activity, the noon sector is not necessarily dominant anymore. The magnetic PSDs have a very distinct dependence on Kp. In addition, the PSDs appear to have a weak dependence on McIlwain parameter L with power slightly increasing as L increases. The magnetic wave PSDs are used along with the Fei et al. (2006) formulation to compute DLLB[CRRES] as a function of L and Kp. The L dependence of DLLB[CRRES] is systematically studied and is shown to depend on Kp. More significantly, we conclude that DLLEis the dominant term driving radial diffusion, typically exceeding DLLB by 1–2 orders of magnitude. Key Points Electric diffusion coefficients are dominant over the magnetic coefficients ULF wave power is not uniform in azimuth as assumed by theoretical formulations L dependence of the diffusion coefficients depends heavily on Kp