Cluster Multi-spacecraft Observations of Electrostatic Solitary Waves, VLF Saucers and Broadband Wave Bursts in the Auroral Downward Current Region

The four Cluster spacecraft have been transiting Earth’s auroral acceleration region approximately every 2.3 days since 2008. The Wideband Data (WBD) plasma wave receiver mounted on all four spacecraft obtains high time resolution waveforms in several different frequency bands which span the frequency range from 100 Hz to 577 kHz. We present WBD data obtained simultaneously on more than one Cluster spacecraft in and near the auroral downward current region in the following two frequency bands: 100 Hz to 9.5 kHz and 700 Hz to 77 kHz. These frequency bands are well suited for observing electron scale Electrostatic Solitary Waves (ESWs) and VLF saucers. We examine and analyze the ESWs for similarities on different spacecraft, and investigate the conclusion based on FAST satellite data that ESWs are observed only in conjunction with upgoing field-aligned ionosphere electrons that are intense and accelerated (10 eV-10 keV). We also analyze multi-spacecraft events in which VLF saucers are observed, and investigate the phenomenon of broadband bursts of waves at the vertex of many of these saucers. We explore the possibility that the saucers are on flux tubes carrying intense, upgoing energetic electron fluxes, similarly to ESWs observed in the absence of VLF saucers