SERSIO: Svalbard EISCAT Rocket Study of Ion Outflows

The SERSIO sounding rocket was launched from Ny-Alesund, Svalbard into an ion upflow event simultaneously observed by the EISCAT radar facility in Longyearbyen on January 22, 2004 at 0857 UT. It reached an apogee of 782 km. In situ wave data and thermal particle measurements in the cusp/cleft region clearly show core thermal ion temperature enhancements up to 0.8 eV in association with 0-4kHz broadband extremely low frequency wave activity (BBELF). The in situ observation of wave heating in the cusp/cleft region at these low altitudes (520-780 km) is a new measurement and should be included in any multi-stage model of ion energization. Wave activity in the form of naturally enhanced ion acoustic lines (NEIAL) was seen by the EISCAT radar in the same activity region. Periods of NEIAL were compared with in situ auroral electron data which show no evidence of a bump-on-tail distribution, thus our data do not support using Langmuir turbulence to explain these radar echoes. In contrast, these observations associating NEIAL with BBELF activity suggest that they may be the same phenomenon. In situ measurements also confirm the link between soft electron precipitation and thermal electron temperature enhancements in this ion upflow environment. Electron temperature enhancements can reduce instability thresholds for the current driven instabilities thought to drive BBELF activity.