Abstract:Our Sun not only emits heat and light which sustains life on Earth, but charged particles escape from its hot corona to become the gusty, ever-present solar wind. Space plasma physics is the study of how this 'space weather' interacts with the Earth's magnetic field and with other planetary environments. It is a discipline which can use both large and small space missions to examine the effects of the Sun on the Earth. In this talk we will introduce the field and some of the outstanding questions, and look at present and future space missions which are planned to answer the questions. We will particularly discuss the role of small satellites in possible future projects in this area.