1. Winter Sun

2. Новые направления в физике больших солнечных вспышек С.И. Безродных, Л.С. Леденцов, Б.В. Сомов Отдел физики Солнца ISR, Febr 8, 2009 My friend Eric

3. ► Analytical models of magnetic reconnection ► Coronal hard X-ray (HXR) sources and particle acceleration

4. Analytical Models of Magnetic Reconnection Bezrodnykh, Vlasov, Somov, Astronomy Lett. 33, 130, 2007; Astronomy Lett., submitted, 2009; Ledentsov, Somov, Vestnik MGU, in press, 2010

5. Two classic models of reconnection Current layer by Syrovatskii: direct current (DC) and return currents (RC) inside thin current layer Petschek Flow: compact diffusion region D and 4 attached MHD slow shock waves of infinite length

6. Dissipative MHD numerical modeling Yokoyama, Shibata, ApJ, 474, L61 Magnetic obstacle

7. «Free upward» reconnection creates magnetic «island» (magnetic obstacle) Heat conduction front moves much faster than slow MHD shock wave

8. Another numerical experiment: MHD shock wave structure in supersonic reconnection Shimisu, Kondo, Ugai. 2005

15. Attempt interpretation ► A slow shock associated with reconnection is separated by a fast shock into a switch off shock (Region 2) and a slow shock (Region 3) ► The slow shocks formed around the plasmoid is studied

16. New analytical solution ► Thin current layer of the Syrovatskii type and attached discontinuous MHD flows of finite length ► A character of flows is not prescribed but determined from a self-consistent solution ► Global structure of magnetic field and local properties of the field near current layer and discontinuities Bezrodnykh, Vlasov, Somov, Astronomy Lett.

17. New model of reconnection in the presence of attached MHD discontinuities Configuration of currents: Current layer Г and 4 attached discontinuities of finite length The Riemann-Hilbert problem for Magnetic field Analytical function

18. Solution of the problem Unknown function is determined as where

19. Parameter General solution

20. Geometrical parameters of the model L – halfwidth of current layer (CL) R – length of discontinuity l – coordinate along the discontinuity

21. Magnetic field lines

22. Angles θ 1 and θ 2 as a function of l Trans-Alfvenic Shock Wave

23. New features of reconnection ► Despite the expectations that follow from the Petschek model, the attached discontinuities appear to be not the slow MHD but Trans-Alfvenic shock waves (TASW) ► This is typical for the fast reconnection with return currents inside the current layer ► TASW are non-evolutionary

24. New consequences for physics of solar flares ► Two types of transition from non- evolutionary shock waves (TASW) to evolutionary ones exist depending on geometrical parameters of reconnection region ► New possibilities to interpret results of numerical and laboratory experiments on reconnection in the dissipative MHD and collisionless plasmas

25. The current-layer rupture in a place of anomalous resistivity of plasma Токовый слой с разрывом содержит области прямого тока DC и присоединенные области обратного тока RC Магнитное поле Аналитическая функция Токовая конфигурация из распадающегося слоя Г и четырех присоединенных разрывных течений S k

26. Bezrodnykh, Vlasov, Somov, Astronomy Lett., subm., 2009 Generalized analytical model Magnetic field lines in the vicinity of a disrupted current layer with attached discontinuous MHD flows

27. Coronal HXR Sources and Particle Acceleration Bogacheev and Somov, Astronomy Lett. 33, 54, 2007; 35, 57, 2009; Somov, Astronomy Lett., 36, No. 6, 2010

28. Main phase Chromospheric ribbons limb

29. Another flare with a coronal HXR sources HXRs show 1) Footpoints 2) Sources in corona The flare skeleton

30. Magnetic reconnection interpretation 1)Release of magnetic energy 2)Accelerated electrons produce HXRs and heat plasma 3)RHESSI provides the first pieces of quantitative evidence for reconnection in flares. HXR footpoints e-e- evaporation reconnection reconnection downflow

31. Quantitative evidence of reconnection 14-16 keV 12-14 keV 10-12 keV 8-10 keV 12-14 keV 16-20 keV footpoints Sui, Holman, 2003 Temperature gradient towards the super-hot turbulent- current layer (SHTCL, Somov, 2006) temperature increase

32. Conclusion from Observations and Theory HXR emissions in flares can be interpreted involving a reconnecting super-hot turbulent-current layer as the source of flare energy HXR emissions in flares can be interpreted involving a reconnecting super-hot turbulent-current layer as the source of flare energy Somov B.V., Plasma Astrophysics, Part II, Reconnection and Flares, Springer, 2007 Somov B.V., Plasma Astrophysics, Part II, Reconnection and Flares, Springer, 2007 …formulae in these books

33. New Observational Fact – Downward Motion of Coronal HXR Source Sui and Holman, ApJ 596, L251, 2003; Liu and Gan, ApJ 639, L137, 2005; Ji, Huang, Wang et al., ApJ 636, L173, 2006

34. GOES and RHESSI light curves of the M7.6 flare on 24 October 2003 Joshi, Veronig, Cho et al., ApJ 706, 1435, 2009

35. Downward (~11 min, ~15 km/s) and upward (later on) motion of the coronal HXR source

37. Rainbow Reconnection ► (a) A model distribution of magnetic field in the photosphere ► (b) A vortex flow distorts the neutral line so that it takes the shape of the letter S

38. Rainbow Reconnection ► A separator X appears above the S -bend of the photospheric neutral line NL Somov B.V.: 1985, Soviet Phys. Usp. 28, 271

39. Vortex flow generates two components of the velocity field in the photoshere ► The perpendicular component of velocity drives reconnection in the corona ► The parallel component provides a shear of magnetic field above the photospheric NL x y C – central part

40. Pre-flare Energy Accumulation ► (a) An initial configuration ► (b) Converging flows induce a reconnecting current layer (RCL) in the corona ► An excess energy is stored as magnetic energy of the RCL Somov, Kosugi, Hudson et al., ApJ 579, 863, 2002

41. Reconnection an Energy Release ► Motion of the HXR footpoints due to reconnection ► Footpoint separation increases with time ► The apparent displacement is proportional to the reconnected flux

42. Pre-flare Structure with Shear ► (a) The initial configuration ► (b) The converging flows creates the RCL ► Shear flows ► Shear flows make the field lines longer, increasing the energy in magnetic field

43. Motion of HXR Footpoints ► (a) Pre-reconnection state of the magnetic field with the converging and shear flows Rapidly decreasing footpoint separation ► (b) Rapidly decreasing footpoint separation because of shear relaxation Somov, Kosugi, Hudson et al., ApJ, 579, 863, 2002

44. The rainbow reconnection model predicts two types of motions of chromospheric HXR kernels ► An increase of a distance between the ribbons, in that the HXR kernels appear, via reconnection in the RCL ► A decrease of the distance between the kernels because of the shear relaxation

45. The rainbow reconnection model explains the descending motion of the coronal HXR source during the early rise phase ► A decrease of the distance between the kernels because of the shear relaxation ► Downward motion of coronal source Somov, Astronomy Lett. 36, No. 6, 2010

46. Reconnected loops are strongly stressed by magnetic tensions to the edge of RCL Magnetic obstacle Quasi-equilibrium loops: height of a loop is proportional to the distance between its feet.

47. HXHHHX X-ray flux from a collapsing magnetic trap in energy ranges: a – 25 keV, b – 50 keV, c – 75 kev as a function of trap length Bogachev and Somov, Astronomy Lett. 33, 54, 2007

48. At the time when the collapsing trap has the maximal brightness in HXR, the height of the loop-top (LT) source in the corona is proportional to the distance between footpoint (FP) sources in the chromosphere At the time when the collapsing trap has the maximal brightness in HXR, the height of the loop-top (LT) source in the corona is proportional to the distance between footpoint (FP) sources in the chromosphere

49. Rapid decrease of FP separation dominates an increase of distance between flare ribbons FPs separate in opposite directions from PNL and from each other Somov, Astronomy Lett. 36, No. 6, 2010

50. Thanks for your attention 254 years somov@sai.msu.ru