January 18, 2013, 12:00 pm - 1:00 pm
January 18, 2013, 12:00 pm - 1:00 pm, Heliophysics Director's Seminar
Asymmetric collisionless magnetic reconnection
Nicolas Aunai, NPP
Collisionless reconnection is a major phenomenon in the universe regarding plasma transport, acceleration and heating. A very strong synergy between theoretical, numerical and observational investigations has led to tremendous progress in the last two decades in our understanding of the key mechanisms controlling reconnection. Most of our knowledge however comes from the modeling of reconnection occurring in symmetric current sheets, which, strictly speaking, are an exception. Indeed, most current sheets separate plasmas of different origins and thus with possibly very different properties. One of the most relevant example being the Earth magnetopause, which separates the shocked solar wind plasma from the tenuous and hotter magnetospheric one. In the wait of the upcoming NASA Magnetospheric MultiScale Mission, understanding the so-called asymmetric magnetic reconnection and predict its observational signatures has become a challenge. In this presentation I will show some of the new and unexpected effects that have discovered over the last year regarding asymmetric reconnection.
Effect of steady convection on the radiation belts
Jenni Kissinger, NPP
The van Allen radiation belts around Earth contain energetic particles that can damage satellites or pose a threat to astronauts. The size and energy of the outer belt can vary greatly, and it tends to increase during magnetic storms. However, even under similar solar wind conditions, not all storms result in radiation belt enhancements, and the full reasons for this remain unknown. It is thought that the role of so-called 'seed' particles is important in determining if a particular storm shows an increase in the radiation belts. These particles are energized in the outer parts of the magnetosphere then transported close to the radiation belts where they are subsequently accelerated further by as yet unknown processes to relativistic energies. These seed particles can be created and transported in two different manners: through short-duration, impulsive events called substorms, and longer, more constant events called steady magnetospheric convection (SMC). Using multiple years of satellite data from GOES and Sampex, we find that magnetic storms with these steady events are more likely to increase the radiation belts than storms without. We suggest that SMC events, which are longer than substorms and can last for hours, bring in a larger population of “seed” electrons that can then be accelerated. The recently launched NASA Van Allen probes mission provides an opportunity to further explore how the highly variable outer belt reacts to substorms and SMC. Determining how different magnetotail responses affect the radiation belts during magnetic storms will assist in space weather forecasting.
Modeling extreme space weather for geomagnetically induced current applications
Chigomezyo M. Ngwira, CUA
Geomagnetically induced currents (GIC) flowing in man-made ground technological systems are a direct manifestation of adverse space weather. Today there is great concern over possible severe societal consequences of GIC effects. This has accelerated recent interest in extreme geomagnetic storm impacts on high-voltage power transmission systems. As a result, extreme geomagnetic event characterization is of fundamental importance for quantifying the technological impacts and societal consequences of extreme space weather. In the last two decades, significant progress has been made towards the modeling of space weather events. Global 3-D MHD models have been at the forefront of this transition and have played a critical role in advancing our understanding of these events. However, the modeling of extreme space weather events is still a major challenge even for existing MHD models. We apply a global 3-D MHD model with specially refined components to simulate space weather events with ``very extreme'' (Carrington-type event) solar wind input conditions driving the magnetosphere. Furthermore, we report on the response of the magnetosphere-ionosphere system to such extreme driving conditions. This extreme solar wind model is designed for application to the modeling of very large ground induced geoelectric fields, which drive large GIC in earth conductors such as power transmission systems.