Alfvén Eigen-modes, Turbulent Transport and Storms in near-Earth Space
Event details
| Date | 06.07.2015 |
| Hour | 14:00 |
| Speaker |
Prof. C.C. Chaston (with acknowledgement to NASA’s Van Allen Probes and THEMIS mission teams) (Space Sciences Laboratory University of California, Berkeley, CA 94720, USA and School of Physics, University of Sydney, NSW 2006, Australia) |
| Location |
PPB 019
|
| Category | Conferences - Seminars |
The impact of explosive mass ejections from the Sun on the Earth drive major disturbances of our near space environment called Geomagnetic Storms. These storms present a significant hazard to ground and space based infrastructure vital to our present day way of life. From the bombardment of spacecraft by energetic particles to the induction of catastrophic currents in power-lines, geomagnetic storms can lead to the loss of vital communication links and power distribution networks with debilitating effect. Despite more than 50 years of study however predicting the evolution and geo-effectiveness of an individual storm remains problematic – this is due to the complexity of the particle acceleration process and because the manner through which large scale electric currents and fields are generated and structured during storms is not well understood. A new two spacecraft plasma physics mission to Earth’s inner magnetosphere has allowed the discovery of very large amplitude broadband electromagnetic fluctuations that are invariably present during the main phase of geomagnetic storms. In this presentation I describe the properties of these variations and show how they correspond to the accumulation of energy in kinetic scale Alfvén Eigen-modes of the geomagnetic field. It is shown how these modes are driven by impulsive plasma injections due to magnetic reconnection in Earth’s geomagnetic tail. It is shown how these modes act to ‘pump-up’ ion energy density in Earth’s inner magnetosphere during storms. It is shown from observations how this process may distort the geomagnetic field and thereby alter the drift paths of all plasmas populating the near-Earth space environment including those of the radiation belts. This global effect may account for certain enigmatic features of the storm-time magnetosphere. This new discovery introduces physics not often considered in the magnetospheric context but is perhaps well known in tokamaks. Some relevant comparisons will be made.
Practical information
- Informed public
- Free
Organizer
- Prof. P. Ricci
Contact
- Prof. P. Ricci