Observation of ULF-waves on the sun and at the Earth’s orbit solar wind

A search for signs of possible connection between plasma velocity oscillations observed in the region of solar coronal holes and magnetic field oscillations recorded in the interplanetary medium has been done. As a basis, observations of solar oscillations in FeI 6569 Å spectral line in a coronal hole were used. Measurements were carried out at Horizontal Automated Solar Telescope of Sayan Solar Observatory. The high speed solar wind stream ejected from the coronal hole reached the Earth’s orbit approximately in 60 hours. Spectra of solar oscillations were compared with those of ultralow frequency (ULF) oscillations of the interplanetary magnetic field (IMF) in the libration point L1. The oscillations were recorded with ACE magnetometer when the leading edge of high speed stream carrying an increased activity of ULF waves reached the Earth. The spectra of solar oscillations had the sharp peak at about 3.4-3.6 mHz. The spectrum of the solar wind ULF oscillations is much more composite, as it is formed by various sources. Nevertheless, ULF oscillations of IMF had the peak close in frequency to that of solar oscillations. The analysis of spectra of ULF waves observed in the leading edges of 92 high speed streams confirmed the presence of 3- and 5-min oscillations in the total wave spectrum. As emphasized, the results can not be a proof of connection between solar oscillations and ULF waves at the Earth’s orbit but they confirm its possibility. An additional research including calculations of trajectories of IMF waves are needed.