investigation of the source region of ionospheric oxygen outflow in the cusp using multi-spacecraft...

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  • Slide 1
  • Investigation of the source region of ionospheric oxygen outflow in the cusp using multi-spacecraft observations by CIS onboard Cluster COSPAR, 2002, Houston, Texas, Paper D3.1-0048-02
  • Slide 2
  • Authors Y.V. Bogdanova (1), B. Klecker (1), G. Paschmann (1), E. Georgescu (1), M.I. Kubyshkina (2), L. M. Kistler (3), C. Mouikis (3), E. Moebius (3), H. Reme (4), J.M. Bosqued (4), I. Dandouras (4), J.A. Sauvaud (4), N. Cornilleau-Wehrlin (5), H. Laakso (6), A. Korth (7), M.B. Bavassano-Cattaneo (8), T. Phan (9), C. Carlson (9), G. Parks (9), J.P. McFadden (9), M. McCarthy (10), R. Lundin (11) (1) Max-Planck Institute for Extraterrestrial Physics, Garching, Germany (2) St.Petersburg State University, St.Petersburg, Russia (3) Space Science Center, University of New Hampshire, Durham, NH, USA (4) C.E.S.R.., Toulouse, France (5) C.E.T.P., Velizy, France (6) ESA, ESTEC, Noordwijk, Netherlands (7) Max-Planck Institute for Aeronomie, Kaltenburg-Lindau, Germany (8) I.F.S.I., Rome, Italy (9) University of California, Berkeley, CA, USA (10) University of Washington, Seattle, WA, USA (11) Swedish Institute of Space Physics, Kiruna, Sweden 2
  • Slide 3
  • Abstract Beams of singly ionized oxygen with very narrow energy distributions originating in the dayside cusp region are observed frequently in the cusp and polar cap regions by the CODIF sensor of the CIS instrument onboard Cluster. During summer nad fall of 2001 the high separation distances of ~1 Re between the spacecraft provided a good opportunity to estimate the size and location of the source of the outgoing O + ions. Statistical study based on 10 events shows that the source region is located near the equatorward edge of the cusp region. Using Tsyganenko T96 magnetospheric magnetic field model we have estimated the size of the acceleration region at the ionosphere level (100 km): latitudinal size is around 1,5 deg and longitudinal size is around 10 deg. Inside the source region Cluster observations at 5-6 Re show high transverse heating of the O + population. This process is colocated with the sharp enhancement of the low-frequency wave fields measured by STAFF and EFW instruments. We conclude that oxygen ions outflow is caused by resonant heating by broadband extra low frequency (BBELF) wave fields at altitudes of 5-6 Re and below. 3
  • Slide 4
  • Introduction Oxygen outflow from the cusp/cleft region, one of the main sources of the magnetospheric oxygen population, was discovered two decades ago by Lockwood (Lockwood et al., 1985) and Moore (Moore et al, 1986), who used data from Dynamic Explorer-1 (DE-1) satellite and named this outflow as cleft ion fountain or upwelling ions. This type of the O + outflow was extensively studied (see reviews Andre and Yau, 1997; Yau and Andre, 1997; Moore et al., 1999) and some common features of this outflow are well-known but still need additional investigation : 1. The origin of the upward moving ions is inside the cusp/cleft region ( Dubouloz et al., 1998; Bouhram et al., 2002 and references therein) or near the equatorward edge of the cusp/cleft (Mats et al., 1990). 2. Oxygen outflowing population originates from a narrow (