Space physics and solar physics are active research fields. As such there are many phenomena which remain unexplained and theoretical problems which remain unsolved. Some of these will be described and/or posed to you.
This course is intended to provide an overview of these fields, focussing on phenomena and questions which are either global in nature (e.g., space weather events, solar-terrestrial coupling etc.) or which are important in more than one area of the solar system or in more than one problem. The course is intended to be interesting and to motivate people to learn more about our solar system and Earth's space environment.
A strong distinguishing characteristic for this course, and a strong motivation for performing research in space and solar physics, is that space physics (a.k.a. astrophysics of the solar system) is the only area of astrophysics where theories can be tested quantitatively with (in situ) data obtained in the region where a given phenomenon is occurring. This unique aspect is both a stength and a difficulty for space physicists: we can definitively constrain theories with data but must construct much more detailed, quantitative theories than is usual in astrophysics. Most importantly of all, we can be much surer that we understand a given phenomenon when our theories are testable to such a strong degree.
Here this strength of space physics as a field is emphasized by presenting and considering both observations and theory in an even-handed way. This will not be a predominantly theoretical course. The course will also be practical in the sense that phenomena like space weather and solar activity are becoming of increasing importance to modern life due to our society's reliance on satellites for communication and on electrical power systems, while natural phenomena like the aurora and coronal structures seen during eclipses should be understood at a basic level by more members of society. Put another way, the course is practical since it is concerned with the space environment of Earth, associated couplings between our planet and the Sun, and the local interstellar environment of our solar system.
Plasmas are often referred to as the fourth state of matter, with over of the Universe being in the plasma state. Plasmas in our solar system (e.g., in Earth's ionosphere & magnetosphere, the solar wind, and the corona) are the closest astrophysical plasmas to us. They are also amenable for in situ observations. This is important since in principle it permits us to develop a detailed, observationally-tested understanding of solar system phenomena which are thought to be ``battery powered versions of astrophysical sources''. An example is Jupiter's magnetosphere versus pulsar magnetospheres.
Another relevant point is that laboratory plasmas are usually very different to those observed in space, typically having much higher number densities, lower temperatures, and much more collisional natures (Figure 0.1).
Figure 0.1: Densities and temperatures of specific space, solar, astrophysical and
laboratory plasmas
Most space plasmas, in particular, are collisionless systems; i.e., the frequency of both nuclear collisions and scattering by electromagnetic fields is typically much less than other characteristic frequencies of space plasmas. Accordingly different plasma physics phenomena often occur in laboratory plasma devices than in space plasmas. Since space plasmas have characteristics much more similar to those inferred for most astrophysical sources, space plasmas arguably show plasma phenomena that are more intrinsic, natural, and applicable to astrophysical sources than laboratory plasma devices. Laboratory plasmas are very important in their own right, of course. Examples include semiconductor processing devices, fluorescent lights, etc.