Towards a More Complete Understanding of Large Amplitude Coherent Whistler Mode Waves Observed within and Near Solar Wind Stream Interaction Regions

Abstract:

Large amplitude (1-40 mV/m) whistler mode waves observed in the solar wind were first reported by Breneman et al. [2010]. The whistler waves were found near stream interaction regions (SIRs) and co-rotating interaction regions (CIRs), and appeared as narrowband waveforms in the frequency range 10-100 Hz (~0.1-0.5 f_ce). These observations were made possible by the presence of a high time resolution electric field waveform receiver provided by the Time Domain Sampler (TDS) instrument on the STEREO spacecraft. Six months of TDS waveform captures of 2s duration near predicted SIRs and CIRs allowed the first investigation of the characteristics of the whistler waves, such as wave packet duration, amplitude and structure.

The THEMIS mission included five spacecraft, each equipped with a full complement of particle and field detectors, including full waveform electric (EFI) and magnetic (SCM) field detectors and electrostatic analyzers (ESA) for thermal charged particles. Two of the spacecraft were successfully transitioned into lunar orbit in 2010, placing them periodically into the solar wind stream interaction region, and these two spacecraft (now called ARTEMIS) thus have extended the THEMIS mission and offer an excellent opportunity to expand on the study of whistler mode waves in this region. We will present observations of coherent large amplitude waves from both STEREO and THEMIS, along with the particles present at the time of these observations. We will carry out statistical studies of the wave packet amplitude, duration, and structure, and the particle distribution characteristics. We will discuss the characteristics of the waves and their role in driving modifications in solar wind electron distributions. Additionally, we will use the WHAMP code to investigate wave growth, given input particle distributions similar to those observed coincident with the whistlers, to see if there is some free energy source in the particles in this region that could be responsible for the generation of these waves.