This paper presents a study of millihertz magnetic pulsations seen in the magnetosphere and on the Earth under quiet space weather conditions. We found that these fluctuations appear in the magnetosphere as soon as disturbances with the same frequency vanish in the solar wind. The results of this work show the possibility of a substorm developing under absolutely quiet external conditions and allow us to assume that these pulsations represent a substorm preparatory phase.

We present a study of ultralow-frequency waves in the ionosphere and on the ground. These waves are very slow (their periods are about several minutes). They are registered on the ground as geomagnetic pulsations. No simple dependence exists between geomagnetic and ionospheric pulsations. Here we study not only selected pulsations with very high amplitudes but also usual pulsations and try to answer the question, which pulsation parameters are favorable for modulation of the ionosphere?

We present a study of ultra-low-frequency waves in the ionosphere and on the ground (geomagnetic pulsations). They can influence particle flux in the magnetosphere, which modify the ionosphere. However, there is no simple dependence between geomagnetic and ionospheric pulsations. We study not only selected pulsations with very high amplitudes but also usual pulsations and try to answer the question, which pulsations' parameters are favorable for modulation of the ionosphere.

A substorm is a dramatic phenomenon in the near-Earth space that is visualized as an aurora. Mostly substorms are caused by changes in the solar wind, but some of them can develop without any evident trigger. Such substorms together with undisturbed days were investigated using magnetometer and photometer data from Svalbard. Substorm precursors, i.e., specific features in 1–4 mHz geomagnetic and auroral luminosity pulsations, have been found at high geomagnetic latitudes.