space group department of physics umeå university
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/1.jpg)
Space Group
Department of PhysicsUmeå UniversityStaff:
Kjell Rönnmark, prof.Patrik Norqvist, lektorMaria Hamrin, lektor
Annie Reiniusson, doktorandJörgen Vedin, doktorand
Niklas Melander, exjobbare
![Page 2: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/2.jpg)
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 tubesJörgen Vedin, Kjell Rönnmark.
Small scale density gradients, FrejaAnnie Reiniusson, Gabriella Stenberg, Patrik Norqvist, Kjell Rönnmark, …
Small scale density gradients, Cluster Patrik Norqvist, Gabriella Stenberg, …
Bonus project 1: Cluster passage of reconnection separatricesMaria Hamrin, Gabriella Stenberg, …
Bonus project 2: Calibration of IMA, Mars ExpressNiklas Melander, Maria Hamrin, Patrik Norqvist, Rickard Lundin, …
Hamrin, Uppsala, May 2006
![Page 3: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/3.jpg)
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…
![Page 4: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/4.jpg)
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=100kmW=20km
![Page 5: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/5.jpg)
Reasonable measures of quality.
Hamrin, Uppsala, May 2006
![Page 6: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/6.jpg)
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
![Page 7: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/7.jpg)
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
ΣSE
SE
SB
ΣSB
Cluster data confirms this.
![Page 8: Space Group Department of Physics Umeå University](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56813621550346895d9d96b7/html5/thumbnails/8.jpg)
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