Ion Density Fluctuations at the Kinetic Scale: Experimental Investigations

Friday, 19 December 2014
Zdenek Nemecek1, Jana Safrankova1, Frantisek Nemec2 and Christopher H K Chen3, (1)Charles University, Prague, Czech Republic, (2)Charles University, Prague, 180, Czech Republic, (3)Imperial College London, London, United Kingdom
It is well established that the solar wind undergoes a heating along its path through the solar system but the sources of this heating are still under debate. Among them, a gradual dissipation of large scale discontinuities toward smaller scales and, eventually, to the heat via turbulent cascades is frequently discussed.
The contribution presents the analysis of ion density variations that are measured onboard the Spektr R spacecraft with a unique time resolution of 32 ms. The analysis reveals that (1) the mean frequency spectrum of density variations in the MHD range (up to about 0.05 Hz) is steeper than usually discussed –5/3, and (2) this part is followed by a plateau that is terminated near proton kinetic scales. We study the dependence of the slopes of different parts of the frequency spectra on background plasma parameters and discuss the results in view of present theories of Alfvenic turbulence in the solar wind.