October 20, 2017, 1:00 pm - 2:00 pm
October 20, 2017, 1:00 pm - 2:00 pm, Heliophysics Director's Seminar, Hosted by the Space Weather Laboratory (674)
First Demonstration of a Coronal Mass Ejection Driven by Helicity Condensation
Joel Dahlin
Understanding the mechanism for generating coronal mass ejections and eruptive flares is one of the most important problems in all space science. Previous simulations of eruptions have used special assumptions, such as a particular initial condition ripe for instability and/or particular boundary conditions designed to induce eruption. We report on a simulation in which the initial state is the minimum-energy potential field, and the system is driven solely by the small-scale random motions observed for photospheric convection. The only requirement on the system is that the flows are sufficiently complex to induce pervasive and random reconnection throughout the volume, as expected for coronal heating, and a net helicity is injected into the corona, in agreement with the observed hemispheric helicity preference. We find that as a result of a turbulent-like cascade, the helicity 'condenses' onto a polarity inversion line forming a filament channel, which eventually erupts explosively. We discuss the implications of this fully self-consistent eruption simulation for understanding CMEs/flares.
Chorus and plasmaspheric hiss waves in the inner magnetosphere
Homayon Aryan
Trapped energetic radiation belt electrons represent a serious hazard to the electronic components of satellites. The impact can be severe and lead to permanent failure of individual subsystems, or even complete loss of the satellite. Unsurprisingly, the radiation belts have been the main focal point of many scientific NASA missions. The main goal is to understand this environment in detail and understand how it is affected by solar wind variability. The interaction of gyroresonant wave particles with plasmaspheric hiss and chorus waves plays a direct and crucial role in the acceleration and loss of radiation belt electrons that ultimately affect the dynamics of the radiation belts. The injection of substorm electrons leads to the excitation of intense chorus emissions that accelerate the electrons in the Earth's outer radiation belt to relativistic energies that could cause radiation damage to Earth orbiting spacecraft. We study these waves within the inner magnetosphere, how it responds to different geomagnetic activity and solar wind conditions, and how the wave models can be applied to current radiation belt models for improved simulation results.
Geomagnetically induced currents during severe geomagnetic storms
Chigomezyo Ngwira
Extreme space weather events can adversely impact operation of critical modern-day technological assets such as high-voltage electric power transmission grids. However, understanding the magnetosphere-ionosphere (M-I) couple system under extreme solar wind driving conditions is still a challenge. In particular, our knowledge of the basic processes associated with the development of complex M-I dynamic currents, which generate large induced geoelectric fields on the ground, is limited. This presentation highlights some of the past and present GIC research within the Space Weather Laboratory in the last five years. Possible future research is discussed.
