Properties of Spectral Shapes of Whistler-Mode Emissions

Thursday, 18 December 2014
Eva Macusova1, Ondrej Santolik1,2, Jolene S Pickett3, Donald A Gurnett3 and Nicole Cornilleau-Wehrlin4,5, (1)Institute of Atmospheric Physics ASCR, Prague, Czech Republic, (2)Charles University, Prague, Czech Republic, (3)Univ Iowa, Iowa City, IA, United States, (4)LESIA/ Observatoire de Paris, Paris, France, (5)LPPP/CNRS - Ecole Polytechnique, Palaiseau, France
Whistler-mode emissions play an important role in wave-particle interactions occurring in the radiation belt region. Whistler mode chorus emissions consist of discrete wave packets which exhibit different spectral shapes. Rising tones (events with positive value of the frequency sweep rate) are frequently observed. Other categories of chorus spectral shapes, such as falling tones, hooks, broadband patterns, are also known. Whistler-mode emissions can additionally occur as hiss or combinations of hiss with discrete patterns.

In this study, we have analyzed more than 11 years of high-time resolution measurements provided by the Wideband Data (WBD) instrument onboard four Cluster spacecraft to identify different spectral shapes of whistler mode emissions. We determine the distribution of individual groups of chorus spectral shapes in the Earth's magnetosphere and the effect of the different geomagnetic conditions on their occurrence. We focus on average polarization and propagation properties of the different types of spectral shapes, obtained during visually identified time intervals from multicomponent measurements of the STAFF-SA instrument recorded with a time resolution of 4 seconds.