Low Frequency Waves in and around Energy Conversion Regions in the Plasma Sheet

D. Constantinescu (1,2)
O. Marghitu (2)
M. Hamrin (3)
K.-H. Glassmeier (1)

1. Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig, Braunschweig, Niedersachsen, Germany. 
2. Institute for Space Sciences, Bucharest, Romania.
3. Faculty of Science and Technology, Umeå University, Umeå, Sweden. 

Regions in the Plasma Sheet (PS) where the energy is converted between the
electromagnetic field and the plasma particles can be identified using the sign
of the scalar product between the electric field and the current density.
Positive sign indicates transfer from the field to the particles  (Concentrated
Load Region - CLR) while negative sign indicates the reverse process
(Concentrated Generator Region - CGR).These regions may play an important role
in the Plasma Sheet (PS) dynamics and in the energy exchange between the tail
and the inner magnetosphere. 

Here we use the Cluster FGM magnetic field data to study the low frequency waves
associated with several ECR's encountered during a PS crossing in July 2003. The
close to regular shape of the tetrahedron and the small distances between the
spacecraft allowed the use of the source locator technique to determine the
waves propagation directions and the proximity of the wave sources for several
selected intervals inside and outside the ECR's. We found that the waves were
propagating orthogonal to the magnetic field both inside and outside the ECR's.
Outside the ECR's the waves always came from large distances and propagate
close to parallel with the XY plane. In contrast, the waves detected within
CLR's always came from close sources. Inside CGR's both close and distant
sources were found.