Ingen bildrubrik

Hamrin, M., Norqvist, P., Marghitu, O., et al.

e-mail: hamrin@space.umu.seDepartment of Physics, Ume University, Sweden

Nordic Cluster Meeting, Uppsala, August 2011Hamrin, Nordic Cluster Meeting, 2011 Cluster observations of energy conversion regions in the plasma sheet1 Our previously published papers on plasma sheet (PS) energy conversion.

Recently we have obtained experimental evidence of the relation between PS energy conversion andthe energy input at the magnetopausethe energy flow towards the ionosphere

Work in progress

Now Im looking for advice from you!

Splinter? - Background - Hamrin, Nordic Cluster Meeting, 20112 ~20 years ago, the view on PS transport processes changed by the discovery of BBFs [Baumjohann et al., JGR, 1990; Angelopoulos et al., JGR, 1992].

PS plays a fundamental role for the energy conversion and transport processes in the Earths magnetosphere (Msp).

Primary energy source: Solar wind kinetic energy, transferred into the Msp by means of reconnection [Paschmann et al., Nature, 1979].

Tail reconnection releases energy stored in the tail magnetic field. Magnetic energy converted to kinetic energy (BBFs).

Energy is transported away as Poynting flux and particle flux. Possibly recurring conversions in the PS between electromagnetic energy and kinetic energy (plasma bulk and thermal) forms [Hamrin et al., JGR, 2011].

Some energy dissipated in the auroral ionosphere [Hamrin et al., Ann Geophys, 2006, Hamrin et al., Ann Geo, JGR, 2011].

Appealing to explore the structure of the PS energy conversion and transport in relation to the SW energy input and auroral dissipation! - Introduction: The Plasma sheet - Hamrin, Nordic Cluster Meeting, 20113 Poyntings theorem:

Energy of bulk motion:

Plasma acc./decel. by Lorenz force, JB

Study EJ in the PS with Cluster! (JB)v= (-vB)J=EJEJ0 (load)MechanicalenergyElectromag.energy

- TOOLs - Power densityHamrin, Nordic Cluster Meeting, 20114 J=B from FGM

=Esc/n from CIS -vB

Reference frame of irreversible energy dissipation: neutral wind system GSE (GSM)

We study clearly identifiable regions of energy conversion: ECR= Energy Conversion Region: CLR = Concentrated Load Region CGR = Concentrated Generator Region

Automatic ECR database: 2001, 2002, 2004, 15-20RE. 428/127 CLRs/CGRs from 220 Cluster PS passages (2730h)

EJEJ - Cluster observations - Hamrin, Nordic Cluster Meeting, 201151. Concentrated regions (time, space) of energy conversionConsistent with high level of fine structure in PS

2. CLRs are stronger and more frequent than CGRs Consistent with PS on the average behaving as a load

3. CLRs/CGRs preferring locations towards CPS/PSBL (high/low ) Consistent with MHD simulation [Birn and Hesse, Ann Geo, 2005]

4. ECR life time and (cross-tail) scale size = 1-10 min and a few REConsistent with BBF scale size [Nakamura et al., Adv Space Res, 2005; Walsh et al., Ann Geo, 2009], MHD simulation [Birn and Hesse, Ann Geo, 2005] and BBF duration [Juusola et al., JGR, 2009]

5. Energy conversion increases with the geomagnetic activity (AE, Kp)

6. Correlated with auroral activity (AE and event investigations)

Consistent picture of the PS energy conversion! - (statistically) Observed ECR characteristics - Hamrin, Nordic Cluster Meeting, 20116Now heading towards the new results linking the PS energy conversion to

1. SW input into the Msp

2. transport of energy to the ionosphere(BBFs, Poynting flux)

- New stuff - Hamrin, Nordic Cluster Meeting, 20117 Dayside reconnection (SW energy input) is favorable towards southward IMF Bz

ECRs are more common after periods of stable southward IMF

Expected but now we have verification!

More significant result for CLRs. Perhaps because of differences between the spatial distributions of CLRs and CGRs with respect to the Cluster orbit (?)

- (1.) ECR VS. SW input - Hamrin, Nordic Cluster Meeting, 2011

#ECRs#ECRsBz(T-20min)0Bz(T-20min)>0Bz(T-20min)0 than Vx0, towards EarthSx