5-minute Solar Oscillations and Ion Cyclotron Waves in the Solar Wind

TL;DR

This paper investigates how 5-minute solar photospheric oscillations modulate ion cyclotron waves in the solar wind, leading to observable frequency variations on Earth, and presents evidence linking these phenomena.

Contribution

It introduces a theoretical model predicting deep frequency modulation of ion cyclotron waves by solar oscillations and provides observational evidence of this modulation in Earth's geomagnetic data.

Findings

Detection of serpentine emission with 5-minute frequency modulation

Correlation between solar oscillations and geomagnetic wave variations

Validation of the model predicting solar influence on Earth's magnetic environment

Abstract

In the present paper we study impact of the photospheric 5-minute oscillations on the ion cyclotron waves in the solar wind. We proceed from the assumption that the ion cyclotron waves in solar wind are experiencing modulation with a characteristic period of 5 minutes under the influence of Alfven waves driven by photospheric motions. The theory presented in our paper predicts a deep frequency modulation of the ion cyclotron waves. The frequency modulation is expected mainly from variations in orientation of the IMF lines. In turn, the variations in orientation are caused by the Alfven waves, propagating from the Sun. To test the theoretical predictions we have analyzed records of the ultra-low-frequency (ULF) geoelectromagnetic waves in order to find the permanent quasi-monochromatic oscillations of natural origin in the Pc1-2 frequency band (0.1-5 Hz), the carrier frequency of which varies with time in a wide range. As a result we found the so-called "serpentine emission" (SE), which was observed in Antarctic at the Vostok station near the South Geomagnetic Pole. The permanency, range of frequencies, and the deep frequency modulation of SE correspond to the qualitative properties of ion cyclotron waves in the solar wind. Clearly expressed 5-minute modulation of the carrier frequency is particularly important feature of the SE in the context of this work. We believe that we have found non-trivial manifestation of the solar 5-min oscillations on the Earth.