General Seminar : Dr. Chris Davies
Abstract: The magnetic fields of Earth, Mercury and Mars each display unique characteristics that reflect processes in their deep interiors. Earth’s field has existed for at least 3.5 billion years; at present it is strong and dominantly dipolar. By contrast, the present field of Mercury is about 100 times weaker than Earth’s while the global magnetic field of Mars apparently decayed around 4 billion years ago. These fields owe their existence to a dynamo process operating in their host’s liquid iron core, and the differences in observed field behaviour in part reflect the power that is available to convert the kinetic energy of convective fluid motion into magnetic energy. Another important effect arises if the upper core becomes stably stratified; these regions do not participate in the dynamo process and act to filter the field that we ultimately observe. In this talk I will discuss how stratified regions in the cores of Earth, Mercury and Mars could have developed and evolved over the last 4.5 billion years, and how they may influence the magnetic fields we observe today.
Abstract
The magnetic fields of Earth, Mercury and Mars each display unique characteristics that reflect processes in their deep interiors. Earth’s field has existed for at least 3.5 billion years; at present it is strong and dominantly dipolar. By contrast, the present field of Mercury is about 100 times weaker than Earth’s while the global magnetic field of Mars apparently decayed around 4 billion years ago. These fields owe their existence to a dynamo process operating in their host’s liquid iron core, and the differences in observed field behaviour in part reflect the power that is available to convert the kinetic energy of convective fluid motion into magnetic energy. Another important effect arises if the upper core becomes stably stratified; these regions do not participate in the dynamo process and act to filter the field that we ultimately observe. In this talk I will discuss how stratified regions in the cores of Earth, Mercury and Mars could have developed and evolved over the last 4.5 billion years, and how they may influence the magnetic fields we observe today.