Abstract. Major geomagnetic storms are caused by unusually intense solar wind
southward magnetic fields that impinge upon the Earth's magnetosphere
(Dungey, 1961). How can we predict the occurrence of future interplanetary
events? Do we currently know enough of the underlying physics and do we have
sufficient observations of solar wind phenomena that will impinge upon the
Earth's magnetosphere? We view this as the most important challenge in space
weather. We discuss the case for magnetic clouds (MCs), interplanetary
sheaths upstream of interplanetary coronal mass ejections (ICMEs),
corotating interaction regions (CIRs) and solar wind high-speed streams
(HSSs). The sheath- and CIR-related magnetic storms will be difficult to
predict and will require better knowledge of the slow solar wind and
modeling to solve. For interplanetary space weather, there are challenges
for understanding the fluences and spectra of solar energetic particles
(SEPs). This will require better knowledge of interplanetary shock
properties as they propagate and evolve going from the Sun to 1 AU (and
beyond), the upstream slow solar wind and energetic “seed” particles.
Dayside aurora, triggering of nightside substorms, and formation of new
radiation belts can all be caused by shock and interplanetary ram pressure
impingements onto the Earth's magnetosphere. The acceleration and loss of
relativistic magnetospheric “killer” electrons and prompt penetrating
electric fields in terms of causing positive and negative ionospheric storms
are reasonably well understood, but refinements are still needed. The
forecasting of extreme events (extreme shocks, extreme solar energetic
particle events, and extreme geomagnetic storms (Carrington events or
greater)) are also discussed. Energetic particle precipitation into the
atmosphere and ozone destruction are briefly discussed. For many of the
studies, the Parker Solar Probe, Solar Orbiter, Magnetospheric Multiscale
Mission (MMS), Arase, and SWARM data will be useful.
Chasing Down the Slow Solar Wind
