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An abrupt increase in pressure associated with interplanetary shocks will compress the Earth's magnetic field. This leads to a sudden impulse also observed in low-latitude magnetometer records. These events are followed by heavily damped oscillations of approximately 5 min periods, depending on plasma conditions. The general features are explained by a simple model. Our results are supported by satellite and ground-based observations. The results are also important for space–weather predictions.

The solar wind interaction with Earth’s magnetic field deposits energy into the upper portion of the atmosphere at high latitudes. The coupling process that modulates the ionospheric convection and intensity of ionospheric currents leads to formation of densely ionized patches convecting across the polar cap. The ionospheric currents launch traveling ionospheric disturbances (TIDs) propagating equatorward. The polar cap patches and TIDs are then observed by networks of radars and GPS receivers.

We investigate the local time behaviour of auroral structures and emission height. Data are collected from the Fennoscandian Lapland and Svalbard latitutes from 7 identical auroral all-sky cameras over about 1 solar cycle. The typical peak emission height of the green aurora varies from 110 km on the nightside to about 118 km in the morning over Lapland but stays systematically higher over Svalbard. During fast solar wind, nightside emission heights are 5 km lower than during slow solar wind.

The solar eclipse of 5–6 January 2019 perturbed the ionospheric electron density, N, observed with the receiver at the Harbin Engineering University and 14 HF broadcasting stations ~1 000 km around. It was accompanied by ±1.5 Hz Doppler-spectrum broadening, ±0.5 Hz Doppler shift, f_D, variations, 15 min period variations in f_D caused by 1.6–2.4 % perturbations in N, and period changes of 4–5 min in f_D caused by 0.2–0.3 % disturbances in N. The decrease in N attained ~15 % (vs. modeled 16 %).