Presentation on theme: "Space Group Department of Physics Umeå University Staff: Kjell Rönnmark, prof. Patrik Norqvist, lektor Maria Hamrin, lektor Annie Reiniusson, doktorand."— Presentation transcript:
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 Tracking down the (auroral) generator and load regions Maria Hamrin, Octav Marghitu (MPI-Garching & Bucharest), … Method development, GALS Maria Hamrin, Kjell Rönnmark, Jörgen Vedin. Numerical simulations of auroral flux tubes Jörgen Vedin, Kjell Rönnmark. Small scale density gradients, Freja Annie Reiniusson, Gabriella Stenberg, Patrik Norqvist, Kjell Rönnmark, … Small scale density gradients, Cluster Patrik Norqvist, Gabriella Stenberg, … Bonus project 1: Cluster passage of reconnection separatrices Maria Hamrin, Gabriella Stenberg, … 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) Earlier study on auroral generator (Cluster + FAST). Now: Cluster plasma sheet crossings, fall 2001. E·J signatures → concentrated loads and generators found (CLR, CGR). CLR more common. Often close to the neutral sheet. CGR often in PSBL. Good agreement with simulations (Birn & Hesse 2005). Many future prospects…
GALS: Gradient Analysis by Least Squares Method for reconstructing the (B-) field and its gradients at an arbitrary point in space-time by using multi- spacecraft observations. Current density from Ampere’s law. Not very sensitive to the s/c configuration. Comparable or better than the Curlometer. Hamrin, Uppsala, May 2006 L=100km W=20km
Reasonable measures of quality. Hamrin, Uppsala, May 2006
Numerical simulations of auroral flux tubes Numerical model: auroral current circuit. Electrons both modeled as fluid and individual particles (→temperature). Driving mechanism: applied generator in the equatorial magnetotail → Alfvén waves propagating towards the ionosphere. Electrons are strongly heated (parallel and perpendicularly) in the acceleration region. The model explains how field- aligned potential drops of several kV are supported by gradients in the electron temperature (pressure). Hamrin, Uppsala, May 2006
Small scale density gradients, Freja + Cluster Previous studies: increased E in lower hybrid cavities. Now: increased E and B is found on irregular small scale density gradients. More electrostatic waves (E/B bigger) on sharp gradients. Dens Grad Dens ΣSEΣSE SESE SBSB ΣSBΣSB Cluster data confirms this.
Bonus projects Bonus project 1: Cluster passage of the separatrices of a distant reconnection site. Bonus project 2: Calibration of IMA, Mars Express.. Hamrin, Uppsala, May 2006
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