Licentiate seminar
 
Alessandro Retino`
Department of Astronomy and Space Physics, Uppsala University
Swedish Institute of Space Physics, Uppsala
 
 
"Magnetic reconnection at the Earth's magnetopause: Cluster spacecraft observations at different 
scales"
 
Time: 10:15, October 12
Place: Room 80109, The Ångström Laboratory, Uppsala
 
 
Abstract:
 
Magnetic reconnection is an universal process that changes the
topology of the magnetic field and converts electromagnetic energy
into particles energy. The best laboratory to study in-situ
magnetic reconnection is the Earth's magnetopause, the boundary
that separates magnetic field and plasma of solar wind origin from
the terrestrial ones. At the magnetopause magnetic reconnection
enables the interconnection between the interplanetary magnetic
field and the Earth's magnetic field thus allowing the transport
of mass, momentum and energy from the solar wind into the Earth's
magnetosphere. Reconnection is fast initiated in a microscopic
region, the so-called diffusion region, where plasma and magnetic
field are decoupled but affects very large volumes in space for a
long time. Therefore it is a key point to study magnetic
reconnection at different spatial and temporal scales.
The European Space Agency cornerstone Cluster mission is the first
multispacecraft magnetospheric mission that allows an in-situ
study of magnetic reconnection at different scales thanks to
three-dimensional measurements at changeable spacecraft separation.
In this thesis we present Cluster spacecraft observations of
magnetic reconnection at the dayside magnetopause. At large
temporal (several hours) and spatial (several Earth's radii)
scales we show that magnetic reconnection is continuous in time
for about 4 hours and that it best agrees with the component
merging model. At scales smaller than an ion gyroradius we
concentrate on observations close to the X-line and we study the
microphysics of reconnection. We show that a separatrix region
several ion inertial lengths wide can be identified
between the magnetic separatrix, i.e. the magnetic field lines
connected to the X-line, and the reconnection jet on the
magnetospheric side of the magnetopause. The separatrix region is
highly structured down to Debye length scales, even
though the X-line can be up to several tenths of ion lenghts
away.