Current problems in studies of magnetospheric cyclotron masers and new space project “resonance” Original Research Article

We review recent progress and discuss major problems in studies of magnetospheric phenomena related to cyclotron resonant interactions between energetic particles and waves. Particular attention is paid to long-standing and still unresolved issues such as interrelationship between noiselike and discrete emissions in cyclotron masers, the role of different wave modes in acceleration and precipitation of energetic charged particles, and energy transfer from hot to cold plasma component. Perspectives of solving these problems using a new space project RESONANCE, aimed at studies of wave-particle interactions and plasma dynamics in the inner magnetosphere, are discussed. The main goals of the RESONANCE project are as follows: (i) long-term observations of the natural phenomena in one selected magnetic flux tube (dynamics of magnetospheric cyclotron masers, ring current formation, studies of the role of the small-scale processes in the global plasma dynamics); (ii) artificial influence on the operation of magnetospheric maser (direct excitation of wave modes, modification of the flux of precipitating particles, modulation of the maser Q-factor by modification of the reflection index at the ionospheric foot-print of the selected magnetic flux tube). The unique opportunity for long-term measurements in a preselected flux tube is to be realized by using a new type of orbit (“magneto-synchronous” orbit), which ensures the interval of staying in the same flux tube up to 3 hours for studies of natural phenomena and up to 40 minutes for active experiments. Such an orbit is particularly suitable for studying the processes for which field-aligned wave propagation and particle motion are significant.