Windsock memory conditioned ram pressure effect: forced magnetic reconnection

1. Windsock memory conditioned ram pressure effect: forced magneticreconnection Z.Vörös (1), M.L. Khodachenko (1), G. Facskó (2) Space Research Institute, Austrian Acad. Sci., Graz, Austria (zoltan.voeroes@oeaw.ac.at) (2) Finnish Meteorological Inst., Helsinki, Finland Acknowledgements: P. Janhunen, and M. Palmroth(FMI) ARTEMIS, CLUSTER, WIND, Greenland and Canadian geomag network 7.6. 2013, PATH science meeting, IWF GRAZbeck et al., 2011

2. Outline • Windsock motion & forced magnetic reconnection in the Earth‘s magnetotail • External forcing on exoplanet magnetospheres

3. old SW flow direction new SW flow direction dynamic pressure becomes important here dynamic pressure is important here ..... less important here Strong boundary disturbance: wavelength > radius of the tail (Schindler & Birn 1993) FAC energ.particles auroral sign. ground-based sign. Sergeev et al. 2008, Borovsky, 2012 HYPOTHESIS: Windsock motion + Memory + changing SW flow direction = magnetopause disturbance  forced tail response?? Plasmoid Bursty flow Interaction region Forced reconnection Vörös et al. In prep.

4. SW monitor (WIND) magnetosheath monitor (Cluster-1) tail monitor (ARTEMIS) ground based observations Vörös et al. 2013 P1 (THB) P2 (THC) Cluster-1 V~ - 400 km/s Reconnection <V> ~ 0 km/s TAIL Plasmoid Northward IMF, By<0 • is the angle between radial direction (Sun-Earth) and SW speed vector Are windsock associated boundary disturbances strong enough to force reconnection in the tail?

5. GUMICS-4 global MHD simulations of the large-scale motions of the tail -60RE X-Y plane THB THC ION DENSITY 7o WINDSOCK MEMORY: The magnetotail reacts to the solar wind flow directional changes with a time delay of 10 min – ~ 1 hour

6. THE EFFECT OF RAM PRESSURE PULSE GUMICS-4 snapshots

7. FORCED RECONNECTION SIGNATURES Tailward moving plasmoid Geomagnetic signatures of BBF By=0 Z Earth X Y Bx Bz

8. CONCLUSIONS - 1 • Signatures of strong SW/boundary distrubances • ~ 18 hours long windsock interval • Initially northward oriented IMF • (no dayside-nightside flux transfer) • Increased and structured dynamic pressure • during windsock • Signatures of forced reconnection (no flux transfer) • Tailward propagating plasmoids • Auroral streamer/ ground based effects A new scenario: Windsock memory conditioned ram pressure effect: forced magnetic reconnection

9. Magnetodisk dominated hot Jupiter‘s magnetosphere 2D axisymmetric MHD = magnetic dipole + expanding plasma Khodachenko et al. 2012 Antonov et al. 2013 rotation, gravity = 0 fixed pressure and plasma beta • Dead zone: plasma locked in a strong dipole-like • magnetic field • Wind zone: beyond the Alfvenic surface the escaping • plasma stretches the original dipole field • Magnetodisk formation: • thermal expansion of planetary plasma via stellar • radiation • centrifugal acceleration of plasma and release at • the Alfvenic surface • Self-consistent (MHD) evolution to • thin current sheet • kinetic description is needed • External forcing (e.g. forced reconn.) • stellar wind magnetosphere • - magnetodisk interaction • Detectability  auroral activity

10. EXTERNAL FORCING Close-in giant planet • CME associated atmospheric erosion • (Khodachenko et al., 2007) •  In the solar system CME-planet interactions • occur rarely. •  Close-in exoplanets, due to geometric factors, • can interact with CMEs much more frequently • (Khodachenko et al., 2006) • The effective speed: veff Cohen et al., 2011 CME , is the stellar wind speed Windsock memory conditioned ram pressure depends on variations of is determined by the source regions on a star. CME-magnetosphere interactions can also depend on windsock memory effects. The magnetotail is oriented almost perpendicular to the direction of propagation of CME

11. CONCLUSIONS - 2 • Windsock memory effect can be important for • understanding: • Forced reconnection (e.g. at magnetodisks) • Stellar wind-magnetosphere, CME-magnetosphere • interactions