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Simultaneous convection measurements by EDI on Cluster and SuperDARN radars. by M. F örster 1 , P. Puhl-Quinn 1 , H. Vaith 1 , G. Paschmann 1 , J. Baker 2 , R. Greenwald 2 , J.M. Quinn 3 , and R.B.Torbert 3

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Simultaneous convection measurements by edi on cluster and superdarn radars

Simultaneous convection measurements by EDI on Cluster and SuperDARN radars

by

M. Förster 1, P. Puhl-Quinn1, H. Vaith1, G. Paschmann1,

J. Baker2, R. Greenwald2, J.M. Quinn3, and R.B.Torbert3

1 - Max-Planck-Institut für extraterrestrische Physik, Garching, Germany

2 - JohnsHopkins University, Laurel, Maryland, USA

3 - University of New Hampshire, Durham, NH, USA

Abstract

The Electron Drift Instrument (EDI) instrument measures the drift velocity of artificially injected electron beams transverse to the magnetic field from which the electric field vector can be deduced. The comparison with ground-based coherent radars of the Super Dual Auroral Radar Network (SuperDARN) is of high scientific interest for the study of magnetospheric convection and its connection with dynamical coupling processes near the ionospheric footpoints. The comparison must rely on correct mapping procedures by use of relevant geomagnetic field models and on the assumption of equipotentiality along a given magnetic field line. The comparisons show a remarkable good agreement of the electric drift vectors measured by EDI onboard the Cluster satellites and the ground-based observations by SuperDARN while the deviations in magnitude and/or direction are of interest in their own right.

STAMMS conference, Orléans, France, 12-16 May 2003 Session S1


Superdarn and cluster 3
SuperDARN and Cluster-3 SuperDARN radars

 - Cluster-3’s footpoint

SD drift vector (magenta)

Mapped EDI drift (green)


Suppositions
Suppositions SuperDARN radars

Accurate magnetic field line mapping by use of relevant

geomagnetic field models (e.g., the Tsyganenko Model T01_01)

Assumption of equipotentiality along a given magnetic field line

Quasi-static conditions, temporal variations negligible

STAMMS conference, Orléans, France, 12-16 May 2003 Session S1


Faraday s law

SuperDARN radars0

0

Faraday’s Law

Bm , Em

d rm Vm



Bi , Ei

d ri  Vi

STAMMS conference, Orléans, France, 12-16 May 2003 Session S1



Simultaneous convection measurements by edi on cluster and superdarn radars

Auroral currents SuperDARN radars

… cusp


Simultaneous convection measurements by edi on cluster and superdarn radars

CANOPUS SuperDARN radarsground-based

magnetometer measurements

(Bx components)

557 nm MSP keogramm 

Fort Smith magnetometer 

and the riometer voltage 


Superdarn and cluster 31
SuperDARN and Cluster-3 SuperDARN radars

 - Cluster’s footpoints

S-DARN drift vector (magenta)

Mapped EDI drift (C1,C2,C3)


Simultaneous convection measurements by edi on cluster and superdarn radars

Conclusions SuperDARN radars

The Electron Drift Instrument (EDI) allows reliable measurements of the electric drift vector in most parts of the magnetosphere, i. e., also in regions of very low plasma density and small (~ 0.1mV/m) electric field magnitudes.

The comparison must rely on correct mapping procedures by use of relevant geomagnetic field models (e.g., the Tsyganenko model T01_01) and on the assumption of equipotentiality along a given magnetic field line.

The comparisions made so far show a remarkable good agreement ofthe electric drift vectors measured by EDI onboard the Cluster satellites and the ground-based observations by SuperDARN during undisturbed conditions, while deviations in magnitude and/or direction are of interest in their own right.

Such deviations occur obviously in regions of field-aligned currents (FACs), as above the auroral zones, where the mapping might fail and the presence of field-aligned potential differences prevents the straightforward comparison.

An other type of deviations occurs during magnetospheric reconfigurations due to rapidly changing solar wind conditions and are due to induction electric fields.

 Acknowledgements to the ACE (SWEPAM, MAG), WIND (MFI, Plasma), and Cluster FGM teams.

STAMMS conference, Orléans, France, 12-16 May 2003 Session S1


Simultaneous convection measurements by edi on cluster and superdarn radars

Fin SuperDARN radars


Simultaneous convection measurements by edi on cluster and superdarn radars

Auroral currents SuperDARN radars

04:55 UT … cusp


Simultaneous convection measurements by edi on cluster and superdarn radars

SuperDARN and Cluster-3 SuperDARN radars

 - Cluster-3’s footpoint

SD drift vector (magenta)

Mapped EDI drift (green)