2013 Radiation Belts Workshop: Comprehending, Specifying and Forecasting their Dynamics

EMIC triggered emissions: Cluster observations and ray-tracing results

2 Jul 2013, 13:10

20m

Island of Santorini, Greece (http://en.wikipedia.org/wiki/Santorini)

Oral Waves, Wave-Particle Interactions and Radiation Belt Dynamics Wave, Wave-Particle Interactions and RB Dynamics

Speaker

Dr Benjamin Grison (Institute of Atmospheric Physics ASCR)

Description

EMIC triggered emissions have been reported in the inner magnetosphere at the edge of the nightside plasmapause [Pickett et al., 2010]. The generation mechanism proposed by Omura et al. [2010] is very similar to the one of the whistler chorus emissions. Corresponding simulation results agree with observations and theory [Shoji et Omura, 2011]. The main characteristics of these emissions generated in the magnetic equatorial plane region are a frequency with time dispersion and a high level of coherence. We present here a Cluster case study , on the 19th of March 2001 at 1000UT when EMIC triggered emissions are observed by the four spacecraft. At that time the fleet was close to the nightside plasmapause at a magnetic latitude of about 10-15 degrees. From single spacecraft measurements we can estimate the polarization properties of these waves by combining STAFF and FGM data: the wave vector is almost perpendicular to B and it displays a right-hand circular polarization. Adding the EFW data, we show that the Poynting vector is directed mainly toward the Earth. The fleet configuration allows us possible to confirm this sense of propagation by a multi-spacecraft analysis. The second part of this work is dedicated to ray tracing analysis. We use the spacecraft position, the wave vector orientation and the frequency of the emissions and the usual parameters for Tsyganenko models as input data for the model. From the ray tracing results we estimate the position and the size of the source region. We also compare the observed propagation velocity to the estimated one. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7–SPACE–2010–1) under grant agreement n. 284520 (MAARBLE).