Density and magnetic field signatures of interplanetary 1/f noise

Abstract

We investigate the occurrence of 1/f noise in the interplanetary density and the magnetic field at varying heliocentric latitudes. The characteristic spectral amplitudes can be found in Ulysses density and magnetic data in the expected frequency ranges at all available latitudes, ranging from the ecliptic plane to more than 80°. Average spectra indicate a latitudinal variation, with a 1/f density signal becoming more pronounced in higher latitude bands. Azimuthal spectral analysis of solar magnetogram data using the SOHO Michelson Doppler Interferometer also shows 1/f noise in the photospheric magnetic field, most clearly at high latitude. Accordingly, we discuss possibilities that the 1/f signal arises at varying altitudes, possibly surviving coronal dynamics. This raises questions that may be addressed in future studies using spectroscopic, white light, and radio scintillation data. © 2007. The American Astronomical Society. All rights reserved.