space plasma waves
radiation and health
As a university academic, I have two main functions: to undertake teaching and perform research. Doing research involves spending lots of time writing grant proposals, supervising students, developing and operating equipment to record data, analysing that data, presenting the results at conferences, writing journal papers, and of course, thinking about the significance of what we have found.
Research is like a detective story: we use whatever clues are available to try and sort out the truth of nature. To do this it is often necessary to think creatively about how to tease out new information.
My research interests are in near-Earth space physics. This arose because as a kid I was interested in rockets, satellites and technology, and pursued these interests throughout my science degree. By 'near-Earth space' we mean the region of space where satellites orbit, and is dominated by the Earth's magnetic field.
One of the joys about physics is the logic and interconnectedness of all of nature. So, to study near-Earth space physics, you actually need to know something about the sun and the solar cycle, the solar wind and the interplanetary medium, how plasma instabilities arise and propagate, the formation and nature of the Earth's magnetic field, the ionosphere and the atmospheric layers, and the geologic structure beneath your recording instruments. In addition, we use complicated computer-based data analysis techniques (that find applications in areas such as diagnostic medicine), and mathematical modelling of what we believe is happening in nature. We test the model predictions against observations and thus refine the models.
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The sun emits particles (mostly protons, electrons, and some heavier ions) that stream out at around 500 km/sec. This is called the solar wind. It carries with it an interplanetary magnetic field (IMF). Because charged particles don't like to move across magnetic field lines, when solar wind particles encounter the Earth's magnetic field, they stream around it. This results in the formation of a bullet-shaped region called the magnetosphere inside which the Earth's magnetic field and particles are confined.
The interaction between the solar wind, the IMF, the Earth's magnetic field, and magnetospheric particles, causes a variety of space plasma waves. These waves involve variations in magnetic field strength that tranport energy through space just as variations in air pressure transmit sound energy.
There is an enormous variety of these waves. The properties that vary are the amplitude of the magnetic field variation, the wave period or frequency, the orientation of the wave vector (ie. whether the main power is in the north-south, east-west or vertical directions), the phase as seen at spaced locations (and hence the propagation velocity), how continuous or transitory the wave appears, and its frequency content (whether harmonics or other more complex components are present). In fact, there are lots of different mechanisms that may generate plasma waves, and these mechanisms, and the properties of the medium through which the wave propagates, affect the above parameters.
Space plasma waves are interesting to study because:
Our society has become totally dependent on modern technology, including radio and TV networks, mobile phone networks, data transmission via cable, satellites, electric power distribution, and minerals exploration. All of these services are vulnerable to space weather effects.