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

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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:

1 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

2 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

3 Generator and load regions in the plasma sheet (Cluster+FAST)  Earlier study on auroral generator (Cluster + FAST).  Now: Cluster plasma sheet crossings, fall  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…

4 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

5  Reasonable measures of quality. Hamrin, Uppsala, May 2006

6 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

7 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.

8 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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