Coronal Mass Ejections, Shocks, and Space Weather

Coronal mass ejections (CMEs) are spectacular eruptions of plasma and magnetic field from the surface of the Sun into the heliosphere. Traveling at speeds of up to 2,500 km/s and with masses ~1e16 g, they often form shocks in the solar atmosphere, and accelerate particles into interplanetary space. As such, CMEs are recognized as the most important drivers of geomagnetic disturbances and adverse space weather in the near-Earth environment. Impacting our magnetosphere with average magnetic field strengths of 13 nT and energies of ~1e25 J they can cause telecommunication and GPS errors, power grid failures, and increased radiation risks to astronauts. To date, the dynamics of CMEs and the mechanisms by which they accelerate energetic particles via shock waves remain unclear.


Structure of a CME

RSTO employs three CALLISTO radio spectrometers to gain a new insight into the fundamental physics of CMEs and CME shocks, enabling us to improve the forecasting of adverse space weather at Earth. Radio waves at low frequencies (MHz) can be used as a diagnostics of solar activity, such as solar flares and CMEs. They provide the signature of CME-driven shocks (Type II events) and electron beams escaping from the Sun along open magnetic field lines accelerated during a flare (Type III bursts). The emission of radio frequency radiation by a coronal shock or a beam of particles is a multi-stage process. Firstly, a beam of electrons is accelerated either via the shock drift acceleration (SDA) mechanism from a CME, or by acceleration during the flare. This beam is unstable to the generation of plasma oscillations which in turn combine with other plasma wave modes to generate plasma emission at the local plasma frequency and its first harmonic. Using CALLISTO, this plasma emission is recorded via dynamic spectra. The analsyis of these spectra allow for various plasma diagnostics, providing information on CMEs and electron beam velocities.


Space Weather and Telecommunications


As society becomes increasingly dependent on telecommunications and space based technologies, so our risk from adverse space weather increases dramatically. Ground based electricity grid infracstructures ar also vulnerable to increases in solar activity. A recent US National Research Council report estimated the financial cost of cancelled flights, blown power grids, and lost telecommunication satellites at over three trillion dollars. We aim to better understand the relationship between solar activity and telecommunication systems and ultimately to develop a space-weather monitoring service, ultimately leading to safer and more reliable space-based technologies, and power grid infracstructure. The TCD Solar Physics Group hosts SolarMonitor.org, which gives information on the very latest solar activity.


Space Weather Effects on Earth