High‐Speed Solar Wind Streams: A Call for Key Research

The arrival of high‐speed solar wind streams (HSSs) at the Earth's magnetopause drives particle and wave phenomena that are distinct from the phenomena caused by other solar wind structures. Although HSS events do not generally produce a particularly strong ring current (the current caused by ions and electrons drifting around the Earth), they do produce storm levels of other magnetospheric phenomena (enhanced convection, heating, precipitation, relativistic electron energization, and so forth) that can persist for an extended time period (e.g., many days). These events contrast with interplanetary coronal mass ejection (ICME) events, where more transient driving (e.g., 1 day) is the norm. As such, the energy input to the magnetosphere during HSS events is comparable to, or may exceed, the energy input to the magnetosphere during ICME events.