Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004 Consequences of LHDI for three-dimensional collisionless reconnection through thin current sheets J. Büchner+collaborators, at different times, were: J. Büchner+collaborators, at different times, were: J. Kuska, B. Nikutowski, I.Silin, Th.Wiegelmann J. Kuska, B. Nikutowski, I.Silin, Th.Wiegelmann all at: Max-Planck Institut für Sonnensystem- all at: Max-Planck Institut für Sonnensystem- forschung in Katlenburg-Lindau, Germany forschung in Katlenburg-Lindau, Germany (for „Solar System Research“ starting 1.7.2004 after (for „Solar System Research“ starting 1.7.2004 after being „for Aeronomy“ the last 40 years) being „for Aeronomy“ the last 40 years)
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Consequences of LHDI for three-dimensional collisionless reconnection through thin current sheets. J. Büchner+collaborators, at different times, were: J. Kuska, B. Nikutowski, I.Silin, Th.Wiegelmann all at: Max-Planck Institut für Sonnensystem-forschung in Katlenburg-Lindau, Germany - PowerPoint PPT Presentation
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Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Consequences of LHDI for three-dimensional collisionless reconnection through thin current sheets
J. Büchner+collaborators, at different times, J. Büchner+collaborators, at different times, were: were:
J. Kuska, B. Nikutowski, I.Silin, Th.Wiegelmann J. Kuska, B. Nikutowski, I.Silin, Th.Wiegelmann
all at: Max-Planck Institut für Sonnensystem-all at: Max-Planck Institut für Sonnensystem-forschung in Katlenburg-Lindau, Germany forschung in Katlenburg-Lindau, Germany
(for „Solar System Research“ starting 1.7.2004 (for „Solar System Research“ starting 1.7.2004 after being „for Aeronomy“ the last 40 years)after being „for Aeronomy“ the last 40 years)
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Topics• Gradient and current-driven plasma instabilities in
current sheets • Initiation of 3D collisionless reconnection (PIC->Vlasov-
simulation approach) in / through– anti-parallel magnetic fields– creation / annihilation of helicity density– non-anti-parallel, finite guide magnetic field case– asymmetric (magnetopause) current sheet case
• „Anomalous resistivity“ approach to introduce kinetic results into large scale MHD
• EUV Bright Points (BP): MHD modeling of the dynamic evolution (photospheric flows) + anomalous transport=> Null point <or> finite B <or> QSL reconnection ???
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
3D current sheet instabilities• 1970th: quasi/linear theory: LHD-instability at the edges
(Drake, Huba, Davidson, Winske, Tanaka & Sato ... )• 1996: 3D PIC simulations showed: global (kink/sausage)
mode current sheet instabilities can initiate reconnection
(Pritchett et al.; Zhu & Winglee; Büchner & Kuska 1996)• 1998...now: New theory - and simulation results about
current-driven and drift instabilities at sheet center
- XBP are formed inside diffuse clouds, which grow at 1 km/s up to 20 Mm and then form a bright core 3 Mm wide, they last, typically, 8 h
Vaiana, 1970: rockets; Golub et al. 1974-77: Skylab More recently: SOHO and TRACE observations
-Later (Soho...) : also many EUV BP investigated
-> BP are assumed to be prime candidates for reconnection: they well correlate with separated photospheric dipolar (opposite polarity) photospheric magnetic fluxes
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Soho-MDI and EIT: EUV BP
MDI line-of sight magnetic
field
( 40” x 40”)
EIT (195 A) same field of
view
17-18.10.1996 (M. Madjarska et al., 2003)
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Reconnection models for BP
- Due to the B separation in the photosphere -> Reconnection between bipoles
assumed to take place in the corona, -> magnetohydrostatic models, e.g.
- Converging flux model Priest, Parnell, Martin & Gollup, 1994- Separator Reconnection in MCC
Longcope, 1998
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
But: dynamical footpoint motion:
-> currents are driven into the chromosphere/corona
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Model, starting with extrapolated B-fields ...
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
... and footpoint motion (here after 1:39 ...and density-heightUT 18.10.96): profile (VAL):
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Density Evolution -> t=128
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Parallel electric fields and parallel currents at t=128
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Transition region parallel electric fields
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Transition region reconnection
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Reconnection due to resistivity switched on enhanced current (velocity)
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Not at a null, but between two nulls (separator through 35,20,5 ?)
<- Iso-surfaces of a smalltotal magnetic field, henceembedding the nulls
Magnetic Reconnection Theory, Newton Institute Cambridge, August 20, 2004
Further work planned on:• Current sheet instabilities for more
realistic current and field models and their consequences for reconnection
• resulting anomalous transport as an approach toward quantifying the coupling between MHD and kinetic scales for solar and magnetospheric applications
• Reconnection at neutral points vs. separator reconnection vs. quasi-separatrix layer - reconnection in the course of the dynamically evolving „magnetic carpet“ („tectonics“)