SERSIO: Svalbard EISCAT Rocket Study of Ion Outflows

Abstract

[1] 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/cm 3 ) 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.

Auroral ion outflow: low altitude energization

“…We see both in this example, and in the dayside example of Frederick-Frost et al (2007) that soft electron precipitation appears as the trigger for this process. With the SIERRA data we can see the details of both the electron precipitation and the ion upflow, as well as an indirect observation of the higher altitude transverse ion acceleration process, through the ions which do not escape but precipitate back down past the payload.…”

“…The SCIFER and AMICIST Bonnell et al, 1996) experiments observed the low altitude signatures of broadband ELF (BBELF) transverse ion heating subsequently quantified by higher-altitude Freja (Andre et al, 1998;Knudsen et al, 1998a, b;Wahlund et al, 1998) and FAST observations (Lynch et al, 2002;Strangeway et al, 2005). This paper reporting SIERRA rocket observations on the nightside and Frederick-Frost et al (2007) reporting SERSIO rocket observations on the dayside both describe even lower altitude signatures: the initiation of ion heating and upflow that may seed wave particle interactions at higher altitudes.…”

“…Both Type 1 St. Maurice et al, 1976) and Type 2 (Frederick-Frost et al, 2007;Lynch et al, 1996) cases have been studied with sounding rockets, though there is a bias towards precipitation-driven events as the precipitation activity is often the trigger for calling the rocket launch.…”

Sounding rocket study of two sequential auroral poleward boundary intensifications

“…detector [Frederick-Frost et al, 2007]. Figure 10 also illustrates the different widths of the field-aligned population which corresponds to the ionospheric electron temperature.…”

Particle precipitation during NEIAL events: simultaneous ground based nighttime observations at Svalbard

“…More recently, Lunde et al (2007) suggested that the electron precipitation energy flux, the characteristic energy and harder precipitation could be of importance in the process of generating NEIALs. Frederick-Frost et al (2007) suggest that NEIALs and Broad Band Extremely Low Frequency (BBELF, <5 kHz) waves are indicative of the same phenomenon, in which case the parametric decay of Langmuir waves is not a likely explanation.…”