Geomagnetism, Volume 4 focuses on the processes, methodologies, technologies, and approaches involved in geomagnetism, including electric fields, solar wind plasma, pulsations, and gravity waves. The selection first offers information on solar wind, magnetosphere, and the magnetopause of the Earth. Discussions focus on magnetopause structure and transfer processes, magnetosphere electric fields, geomagnetically trapped radiation, microstructure of the solar wind plasma, and hydro magnetic fluctuations and discontinuities. The text then examines geomagnetic tail, neutral upper atmosphere, and geomagnetic pulsations and plasma waves in the Earth's magnetosphere. Topics include plasma waves and instabilities in the magnetosphere, waves in a magneto plasma, gravity waves, atmospheric tides, balance equations for mass, momentum and energy, and absorption of solar and particle radiation. The publication takes a look at auroras and physical processes producing magnetosphere substorms and magnetic storms, including aurora theory and morphology, structure of the magnetosphere, and models of magnetosphere substorms. The selection is a valuable source of data for researchers wanting to explore geomagnetism.