RESONANT ELECTRON SCATTERING BY WHISTLER-MODE CHORUS WAVES IS ONE OF THE MAIN DRIVERS OF ELECTRON PRECIPITATION INTO EARTH S ATMOSPHERE. THE PRECIPITATION AND THE SUBSEQUENT ELECTRON ACCELERATION IN THE AURORA REGION SIGNIFICANTLY CONTRIBUTE TO THE IONOSPHERIC HEATING AND OUTFLOW AND THUS TO THE MAGNETOSPHERE-IONOSPHERE COUPLING. ELECTRON SCATTERING BY WHISTLER WAVES MODULATED BY ULTRALOW- FREQUENCY (ULF) WAVES CAN LEAD TO VARIATIONS IN THE ELECTRON PRECIPITATION AND TO THE FORMATION OF A PULSATING AURORA. THE QUASILINEAR THEORY GIVES A CORRECT ORDER OF MAGNITUDE ESTIMATES OF THE AVERAGE PRECIPITATING ELECTRON FLUXES. HOWEVER NON-STATIONARY (LOCALIZED IN TIME) ULF WAVES SIGNIFICANTLY ALTER (MODULATE) THE ELECTRON RESONANT INTERACTION WITH HIGH AMPLITUDE WHISTLER WAVES AND THE MECHANISM OF SUCH MODULATION REMAINS POORLY UNDERSTOOD. THE MAIN DIFFICULTY COMES FROM THE TWO-PRONGED IMPACT OF ULF WAVES: THEY MODULATE THE WHISTLER WAVES AND AT THE SAME TIME DIRECTLY AFFECT ELECTRON DISTRIBUTION FUNCTIONS. THEREFORE A COMPLETE MODELLING OF ELECTRON SCATTERING IN THE PRESENCE OF ULF WAVES REQUIRES A CONSIDERATION BOTH ELECTRON AND WHISTLER WAVE RESPONSE TO ULF WAVES. THE MAIN GOAL OF THIS PROJECT IS TO INVESTIGATE THE COMBINED EFFECT OF ULF AND MODULATED HIGH AMPLITUDE WHISTLER WAVES ON THE ELECTRON PRECIPITATION. PARAMETRIZATION AND MODELLING OF ELECTRON RESONANT SCATTERING BY MODULATED WHISTLER WAVES REQUIRE A DETAILED INFORMATION ABOUT THE WAVES AND BACKGROUND PLASMA CHARACTERISTICS. WE WILL USE THEMIS SPACECRAFT AND VAN ALLEN PROBES MEASUREMENTS IN RADIATION BELTS TO COLLECT STATISTICS OF ULF WAVES AND MODULATED WHISTLER WAVES OBSERVED AT DIFFERENT LOCAL TIMES AND RADIAL DISTANCES. WE WILL USE MEASURED ULF WAVE CHARACTERISTICS AND ELECTRON DISTRIBUTION FUNCTIONS TO RECONSTRUCT THE ELECTRON DISTRIBUTION MODULATION BY ULF WAVES. IT WILL BE PERFORMED WITHIN THE FRAMEWORK OF THE ADIABATIC THEORY BECAUSE THE ULF WAVES ARE MUCH SLOWER THAN ELECTRONS. NEXT WE WILL USE MEASURED CHARACTERISTICS OF MODULATED WHISTLER WAVES TO DEVELOP A MODEL OF THE ELECTRON RESONANT SCATTERING THAT WILL INCLUDE NONLINEAR EFFECTS OF ELECTRON PHASE BUNCHING BY VERY INTENSE WHISTLER WAVES. COMBINING SPACECRAFT OBSERVATIONS ELECTRON SCATTERING MODELLING AND A RECONSTRUCTION OF ELECTRON DISTRIBUTION MODULATION WE WILL PURSUE THREE PROJECT OBJECTIVES: (1) QUANTIFY THE ROLE OF NONLINEAR ELECTRON SCATTERING DURING MODULATION EVENTS IN THE ELECTRON TRANSPORT INTO THE LOSS CONE; (2) EXPLORE THE DEPENDENCE OF THE ELECTRON FLUX INTO THE LOSS CONE ON CHARACTERISTICS OF ULF WAVES MODULATING WHISTLER INTENSITY AND ELECTRON DISTRIBUTION FUNCTION; (3) DETERMINE THE BACKGROUND PLASMA AND MAGNETIC FIELD PARAMETERS THAT ARE MOST IMPORTANT FOR THE DESCRIPTION OF THE ELECTRON PRECIPITATION DURING MODULATION EVENTS. ACCOMPLISHING THESE OBJECTIVES WILL ALLOW US TO PARAMETRIZE THE ELECTRON TRANSPORT INTO THE LOSS CONE IN MODULATION EVENTS AS A FUNCTION OF GEOMAGNETIC CONDITIONS SPATIAL LOCATION AND ULF WAVE CHARACTERISTICS. THE PROPOSED PROJECT WILL IMPROVE OUR UNDERSTANDING OF THE EQUATORIAL WAVE-PARTICLE INTERACTION WHICH LEADS TO A MODULATED PRECIPITATION AND A PULSATING AURORA. WE WILL TAKE INTO ACCOUNT THE EFFECTS OF ULF MODULATION BOTH ON WHISTLER WAVES AND ELECTRON DISTRIBUTION FUNCTION AND THUS WILL DEFINE THE ROLE OF ULF WAVES AS A DRIVER FOR MODULATED PRECIPITATION. THIS INVESTIGATION WILL ALSO PROVIDE THE FIRST THEORETICAL DESCRIPTION OF NON-DIFFUSIVE EFFECTS (NONLINEAR SCATTERING) OF ELECTRON RESONANT INTERACTION WITH MODULATED WHISTLER WAVES AND WILL QUANTIFY THE IMPORTANCE OF THESE EFFECTS FOR ELECTRON PRECIPITATION. THEREFORE OUR PROPOSAL CONTRIBUTES TO TWO OF THE FOUR SCIENTIFIC OBJECTIVES OF THE HELIOPHYSICS DECADAL SURVEY NAMELY DETERMINING THE DYNAMICS AND COUPLING OF EARTH S MAGNETOSPHERE IONOSPHERE AND ATMOSPHERE AND DISCOVERING AND CHARACTERIZING FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE.