Space Group Department of Physics Ume University Staff

Space Group Department of Physics Umeå University Staff: Kjell Rönnmark, prof. Patrik Norqvist, lektor Maria Hamrin, lektor Annie Reiniusson, doktorand Jörgen Vedin, doktorand Niklas Melander, exjobbare

Current research topics û Tracking down the (auroral) generator and load regions Maria Hamrin, Octav Marghitu (MPI-Garching & Bucharest), … û Method development, GALS Maria Hamrin, Kjell Rönnmark, Jörgen Vedin. û Numerical simulations of auroral flux tubes Jörgen Vedin, Kjell Rönnmark. û Small scale density gradients, Freja Annie Reiniusson, Gabriella Stenberg, Patrik Norqvist, Kjell Rönnmark, … û Small scale density gradients, Cluster Patrik Norqvist, Gabriella Stenberg, … û Bonus project 1: Cluster passage of reconnection separatrices Maria Hamrin, Gabriella Stenberg, … û Bonus project 2: Calibration of IMA, Mars Express Niklas Melander, Maria Hamrin, Patrik Norqvist, Rickard Lundin, … Hamrin, Uppsala, May 2006

Generator and load regions in the plasma sheet (Cluster+FAST) û Earlier study on auroral generator (Cluster + FAST). û Now: Cluster plasma sheet crossings, fall 2001. û E·J signatures → concentrated loads and generators found (CLR, CGR). û CLR more common. Often close to the neutral sheet. û CGR often in PSBL. û Good agreement with simulations (Birn & Hesse 2005). û Many future prospects…

GALS: Gradient Analysis by Least Squares L=100 km W=20 km û Method for reconstructing the (B-) field and its gradients at an arbitrary point in space-time by using multispacecraft observations. û Current density from Ampere’s law. û Not very sensitive to the s/c configuration. û Comparable or better than the Curlometer. Hamrin, Uppsala, May 2006

û Reasonable measures of quality. Hamrin, Uppsala, May 2006

Numerical simulations of auroral flux tubes û Numerical model: auroral current circuit. û Electrons both modeled as fluid and individual particles (→temperature). û Driving mechanism: applied generator in the equatorial magnetotail → Alfvén waves propagating towards the ionosphere. û Electrons are strongly heated (parallel and perpendicularly) in the acceleration region. û The model explains how fieldaligned potential drops of several k. V are supported by gradients in the electron temperature (pressure). Hamrin, Uppsala, May 2006

Small scale density gradients, Freja + Cluster û Previous studies: increased E in lower hybrid cavities. û Now: increased E and B is found on irregular small scale density gradients. û More electrostatic waves (E/B bigger) on sharp gradients. û Cluster data confirms this. Dens Grad Dens SE SB ΣSE ΣSB

Bonus projects û Bonus project 1: Cluster passage of the separatrices of a distant reconnection site. û Bonus project 2: Calibration of IMA, Mars Express. . Hamrin, Uppsala, May 2006