Programme by Session

The northern and southern magnetospheric cusps contain recently opened magnetic flux, with footpoints typically confined to a region about 1 degree wide in magnetic latitude and 2-3 hours wide in magnetic local time (MLT), near noon and just poleward of the last closed field line on the Earth’s dayside. Magnetic reconnection at the magnetopause allows solar wind entry and particle precipitation on cusp field lines. Statistical studies suggest that the mid-altitude cusps vary in width, magnetic latitude and MLT in response to the Interplanetary Magnetic Field (IMF) and solar wind dynamic pressure. When IMF Bz is southward, the cusp moves lower in latitude. Under northward IMF the By component controls the cusp position in MLT, and its influence is less clear for southward IMF. Solar wind dynamic pressure increases cause widening in MLT.

In the early years after their launch, the Cluster spacecraft visited the northern high-altitude cusp, making crossings at roughly steady MLT and changing latitude, but over time this became impossible due to natural orbital evolution. Recently the Cluster orbit has evolved to allow the spacecraft to traverse across the northern exterior cusp at a roughly steady latitude and changing MLT. Using this new opportunity, we are examining a set of events during the Cluster cusp crossing of the 2017/8 winter season for high-altitude measurements in conjunction with ground-based radar coverage, including a subset with dedicated EISCAT radar observations. We will introduce these set of events and present an initial case study.