07/11/2007

ESSW4, Brussels 1

Coupling between magnetospheric and auroral ionospheric scales during space

weather events

M. ECHIM (1,2), M. ROTH(1) and J. DE KEYSER(1) (1) Belgian Institute for Space Aeronomy, Brussels, Belgium (2) Institute for Space Sciences, Bucharest, Romania

07/11/2007

ESSW4, Brussels 2

Outline of the talk

• Auroral activity and space weather events • Dayside auroral arcs and coupling to magnetospheric

boundary layers and SW properties• Tangential discontinuities with sheared flows as auroral

generators; typical scales• Current continuity in the ionosphere; feedback effects• Quasi-static coupling model: numerical results• Conclusions, future research

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Auroral activity and space weather events

Image courtesy of LESIA, Meudon, Paris

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Auroral activity and space weather events

Close to solar maximum (May 1998)

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Auroral activity and space weather events

At solar minimum (September 2007)

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Dayside auroral arcs and coupling to magnetospheric boundary layers and SW

properties

Credit: sci.esa.int/cluster

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Dayside auroral arcs and coupling to magnetospheric boundary layers and SW

properties

Newell et al., 2004

Moen et al., 1994

Vo and Murphree, 2001

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ESSW4, Brussels 9

Tangential discontinuities with sheared flows as auroral generators

Planar surface in the y-z plane

Variations along the xm coordinate normal to the TD plane.

E along the x-axis, B along the z-axis, a,V and J along the y-axis

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Tangential discontinuities with sheared flows as auroral generators

•piecewise Maxwellian VDFs (Roth et al., 1996) •analytical moments of the VDF •Φm and a computed numerically from the Maxwell’s equations •The model can describe simultaneous shears in B and V flow•Convergent electric field

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ESSW4, Brussels 11

Current continuity in the ionosphere; feedback effects

•Current continuity in the ionosphere:

mhos)}sJm({106.15.0 2/11-2-2 p

•Ionospheric feedback:

)(),(IIi

ip

ip

imii xx

Ix

xj

•Self-consistent m; ad-hoc models in previous studies (Lyons, 1980, 1981)

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Quasi-static coupling model: numerical results

07/11/2007

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Quasi-static coupling model: numerical results – effects of LLBL/SW speed

mhos)}sJm({106.15.0 2/11-2-2 p

•Solid line : non-uniform P with P0=0.5 S•Dashed line : non-uniform P with P0=5.0 S•Dotted line : uniform P=P0=5.0 S

and feedback

07/11/2007

ESSW4, Brussels 14

Quasi-static coupling model: numerical results – effects of LLBL/SW density

mhos)}sJm({106.15.0 2/11-2-2 p

•Solid line : non-uniform P with P0=0.5 S•Dashed line : non-uniform P with P0=5.0 S•Dotted line : uniform P=P0=5.0 S

and feedback

07/11/2007

ESSW4, Brussels 15

Quasi-static coupling model: numerical results – effects of e- temperature

mhos)}sJm({106.15.0 2/11-2-2 p

•Solid line : non-uniform P with P0=0.5 S•Dashed line : non-uniform P with P0=5.0 S•Dotted line : uniform P=P0=5.0 S

and feedback

07/11/2007

ESSW4, Brussels 16

Summary, Conclusions

•Larger SW/LLBL velocity larger shear more power

Increased luminosity of the auroral arc

•Larger SW/LLBL density thinner auroral structures

•Ionospheric feedback Larger potential differenceenergy flux

•Low P0 thinner structuressmaller energy flux