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Geomagnetic effects generated by stream interaction regions: forced reconnection in the tail

Geomagnetic effects generated by stream interaction regions: forced reconnection in the tail. Z.Vörös (1), M.L . Khodachenko (1), G . Facskó (2 ) Space Research Institute, Austrian Acad. Sci., Graz, Austria ( zoltan.voeroes@oeaw.ac.at)

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Geomagnetic effects generated by stream interaction regions: forced reconnection in the tail

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  1. Geomagnetic effects generated by stream interaction regions:forced reconnection in the tail • 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 • Project support: • P24740-N27, S11606-N16 • FP7/2007-2013 - 313038/STORM • ERC Starting Grant 200141-QuESpace. • Trailing Edges Workshop • 20 – 24 May 2013, University of Michigan, USA Sibeck et al., 2011

  2. Outline • Magnetic reconnection is a key process in lab/space/astro plasmas • Is there life beyond the Dungey model? • Magnetotail response to the directional changes and pressure pulses in the solar wind

  3. Why magnetic reconnection is a key process in the Earth‘s magnetosphere? Explains key elements of SW-magnetosphere interaction, e.g. loading-unloading, substorms Dungey cycle

  4. MAGNETIC RECONNECTION • In collisionless plasmas ion-electron scale • physics is needed to explain fast reconnection. • In the Earth‘s magnetosphere recon. can be: • - Unforced (e.g. self-evolving MHD process, • Saito et al., 2011); • - Forced • - flux transfer associated (Dungey), • - boundary disturbance driven • (Schindler & Birn, 1993), turbulence,etc.

  5. A. Flux transfer associated reconnection is very effective • when the IMF is southward. • B. How effective is magnetopause disturbance (no • flux transfer) driven reconnection? • Simulation results (Schindler & Birn, 1993) show • that • A >> B... if the spatial scale of disturbance is smaller • than the radius of the magnetotail • A < B... if the spatial scale of disturbance is comparable • ??? or larger than the radius of the magnetotail • What are the physical drivers of large-scale • magnetopause disturbances? • e.g. Solar wind flow directional changes

  6. Sergeev et al. Ann.Geophys. 2008 Magnetotail response to solar wind flow directional changes. Windsock effect: the tail axis, neutral sheet or magnetopause adapt to the new SW flow direction. The adaptation time scale 15 min - more than 0.5 h

  7.  The solar wind flow direction • changes • windsock adaptation • with memory ~ 10-30 min or more • new solar wind direction • dynamic pressure becomes • important at the nightside • magnetopause dynamic pressure is important here ........ less important here new SW flow direction

  8.  The solar wind flow direction • changes • windsock adaptation • with memory ~ 10-30 min or more • new solar wind direction • dynamic pressure becomes • important at the nightside • magnetopause dynamic pressure is important here ........ less important here HYPOTHESIS: Windsock motion + Memory + changing SW flow direction = magnetopause disturbance  forced tail response?? new SW flow direction

  9. Earth‘s motion Sunspot #

  10. SW flow direction SW flow speed Why, when & how the SW flow direction changes? Yurchyshyn et al., 2005

  11. Fast/slow SW

  12. FAST STREAMS

  13. High P ~const Trailing edge P ~ const  changes continuously • change • short ~ 1 h ~9 hours

  14. WINDSOCK EFFECTS & FORCED RESPONSE OF THE MAGNETOSPHERE Warning: Strong SW disturbances induce strong magnetospheric response and system-wide fluctuations.

  15. Are externally driven boundary distrubances strong enough to drive reconnection in the tail which is experiencing windsock motions? boundary disturbance interaction region FAC energ.particles auroral sign. ground-based sign. Plasmoid SW monitor (WIND) magnetosheath monitor (Cluster-1) tail monitor (ARTEMIS) ground based observations bursty outflow Data available from:

  16. ARTEMIS Angelopoulos & Sibeck, 2010

  17. Oct. 2010 P2 P1 Nov. Dec. WINDSOCK Jan. 2011 Febr. March Apr. May 1 day June Typical crossings

  18. GUMICS-4 global MHD simulations of the large-scale motions of the tail: GUMICS-4 code: Janhunen et al., 2012 -60RE X-Y plane THB THC ION DENSITY 7o The magnetotail reacts to the solar wind flow directional changes over a time scale of tens of minutes (Sergeev et al. 2008).

  19. Vörös et al. 2013 Large scale motionand compression of the tail P1 (THB) P2 (THC) V~ - 400 km/s <V> ~ 0 km/s TAIL • is the angle between radial direction (Sun-Earth) and SW speed • vector

  20. The absence of energetic ions (> 2 keV) indicates lobe (Grigorenko, 2012) MAGNETOTAIL LOBE Vörös, 2013 Even small flow directional changes can drive large-scale motions and flapping of the magnetotail

  21. P2 (THC) Large-scale movement of the tail Field, plasma and particle data Strahl (contrapropagating) electrons on magnetotail field lines indicate a connection of magnetotail field lines to the IMF (open field line geometry). Strahl electrons P1 (THB)

  22. P1 (THB) P2 (THB) Cluster1 Southward turning of IMF Flux transfer to the tail Reconnection & plasmoid Substorm activity Northward IMF Nonzero By Plasmoids, no substorms Flapping How to separate windsock, B_y effects, flapping and Plasmoids???

  23. TIMING • Simultaneous occurrence of: • Windsock motion of the tail • (buil-up of the electric field, • vertical-horizonthal flows, • Sergeev et al. 2008) • Increased kinetic pressure • Plasmoids GUMICS-4 snapshots

  24. PLASMOIDS EMBEDDED IN FLAPPING SHEET Z Signatures of plasmoids Are these events plasmoids? X Zong et al., 2004 Sharma et al., 2008 Flapping motion can mimic magnetic signatures of plasmoids. Is it a flapping current sheet?

  25. Signatures of flapping (Sergeev et al., 2008) Y-Z kink flapping signatures in P1&P2 data However, not each crossing is good for MVA

  26. Flapping motion speed: 150 – 300 km/s An example of double current sheet crossing seen by both P1 and P2.  similar to flappings in the mid-tail GUMICS-4 snapshot at X=-55 RE B_Y effect • P1 and P2 are close to the magnetosheath • (next page) • Down dusk propagating flapping • waves interact with the magnetosheath flow. plasma beta

  27. Discriminating between plasmoid and flapping magnetic signatures 3D hodograms

  28. There is no substorm activity associated with observed plasmoids, however, ground-based signatures of Earthward moving fast flows are observed over Canada and Greenland.

  29. CONCLUSIONS • Signatures of strong SW/boundary distrubances • ~ 18 hours long windsock interval • Initially northward oriented IMF • (no flux transfer) • B_y nonzero • Flapping current sheet • Increased and structured dynamic pressure • during windsock • Signatures of forced reconnection (no flux transfer) • Tailward propagating plasmoids • Auroral streamer/ ground based effects

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