The formation of the plasmapause: Dynamical

simulations

V. Pierrard

Belgian Institute for Space Aeronomy

J. Lemaire (Plasmapause mechanism)

J. Cabrera (IMAGE observations)

F. Darrouzet (CLUSTER observations)

Mechanism of plasma instability Kp increases E increases in the morning sector

The convection velocity increasesErosion of the plasmasphere in the post-midnight sector

Formation of a plume

Lemaire and Gringauz,The Earth’s plasmasphere, Cambridge University Press, 1998.

Input: KpE5D equatorial electric field (McIlwain, 1986)

Empirical model determined from observations of ATS5 and ATS6

Dynamical simulationsPierrard and Lemaire, Geophys. Res. Lett., 31, 5, 2004.

9 June 2001

8h00

9 June 2001

16h00

23h00

10 June 2001 7h00

18 June 2001 13h00 -14h00- 15h00- 16h00

18 June 2001 18h0020h00

June 25, 2000, 21h00 BETWEEN SUBSTORMS

June 26, 2000, 16h00 SUBSTORM

May 24, 2000, 9h00 STORM

May 2, 2001, 18h00 VERY QUIET

Kp – L relation * Numerical simulations for constant Kp

-- Linear relation from Carpenter and Anderson [1992]

+ EUV/IMAGE Kp decrease

+ EUV/IMAGE

Kp increase

MLT=20:00, Kpmax=3, small separation distance (~150km)

Plume observed in the inbound pass at the same time

08:30 UT20:10 MLT CLUSTER

07 May 2002

06

12

24

18

08:32 UT20:10 MLT

7.7-8.1 RE

WHISPER: Waves of High frequency and

Sounder for Probing of Electron density by Relaxation

07 May 2002: Simulation, EUV and CLUSTER

Equatorial projection ofEUV image at 08:31 UT:Plume close to the sameMLT sector (23-24)

Simulations based on the instability mechanism

Use the Kp dependent electric field model E5D

Shoulders and plumes are associated to particular Kp evolutions.

The position of the plasmapause depends on Kp and its evolution with time.

Comparisons with IMAGE give similar structures in the same LT sector.

Conclusions