Latitude and local time dependence of ULF wave power at the magnetopause,: A Cluster-Double Star study

International audience[1] Strong ULF wave activity has been observed at magnetopause crossings over a long time. Those turbulent like waves are possibly one of the contributors to particle penetration from the solar wind to the magnetosphere through the magnetopause. Spatio Temporal Analysis of Field Fluctuations wave experiments onboard Cluster and Double Star TC1 spacecraft permit the comparison of those waves during quasi-simultaneous magnetopause crossings, some being at the same local time but at different latitude, the TC1 Double Star orbit being nearly equatorial and the Cluster orbit being polar. From a survey of the first half of year 2004 and beginning of 2005 data, 23 coordinated magnetopause crossings have been identified, out of which 11 are at the same local time, for which the wave power density has been calculated. No clear dependence in local time has been found; in particular, the wave power density is not stronger at noon in the vicinity of the subsolar point than at other local times, the morning hour data showing more dispersed values than afternoon ones. For most of the events occurring at the same local time, the wave power density measured by Double Star (at low latitude) is stronger than the one measured by the Cluster spacecraft (at much higher latitude). If those first results were to be confirmed, it could imply a predominant role of the equatorial plane in the solar wind/ magnetosphere coupling via ULF wave turbulence, with no preference for the subsolar region. Citation: Cornilleau-Wehrlin, N. (2008), Latitude and local time dependence of ULF wave power at the magnetopause: A Cluster-Double Star study