SERSIO: Svalbard EISCAT Rocket Study of Ion Outflows

摘要

The SERSIO sounding rocket was launched from Ny-Alesund, Svalbard, into a type 2 ion upflow event simultaneously observed by the European Incoherent Scatter (EISCAT) radar facility in Longyearbyen on 22 January 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 0–4 kHz 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) and high densities (80,000/cm3) is an important measurement and should be included in any 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 that 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. During these comparisons, all-sky camera images were used to verify similar environmental conditions between the rocket and radar measurement volumes, while the spatial separation between the volumes was less than 500 km. In situ measurements also confirm the link between soft electron precipitation and thermal electron temperature enhancements in this ion upflow environment.