1. Occurrence and properties of substorms associated with pseudobreakups Anita Kullen Space & Plasma Physics, EES

2. 2Sept 8, 2010 Alfven Lab Seminar, EES, KTH Publications about pseudobreakups 1. Kullen, A., and T. Karlsson, On the relation between solar wind, pseudobreakups and substorms, J. Geophys. Res., 2004. 2. Kullen, A., S. Ohtani, and T. Karlsson, Geomagnetic signatures of auroral substorms preceeded by pseudobreakups, J. Geophys. Res., 2009. 3. Kullen, A., T. Karlsson, J. A. Cumnock, and T. Sundberg, Occurrence and properties of substorms associated with pseudobreakups, J. Geophys. Res., in press, 2010.

3. 3Sept 8, 2010 Alfven Lab Seminar, EES, KTH Pseudobreakup types Isolated pseudobreakups Growth-Phase Pseudobreakups Recovery Pseudobreakups

4. 4Sept 8, 2010 Alfven Lab Seminar, EES, KTH Key Issue  How do substorms that are preceded by growth-phase pseudobreakups differ from substorms without pseudobreakups ? solar wind conditions energy transfer to magnetosphere response of the polar cap response of the auroral zone response of the near-earth tail

5. 5Sept 8, 2010 Alfven Lab Seminar, EES, KTH Near-Earth tail signatures Near-Earth tail signatures

6. 6Sept 8, 2010 Alfven Lab Seminar, EES, KTH Magnetotail dipolarization during substorms [W. Baumjohan and R.A. Treumann, Basic Space Plasma Physics, 1996] Stretched tail B-field Dipolarized tail B-field BhBh BhBh NENL versus TCD model What develops first, Near-Earth Neutral Line or tail current disruption ? Tail current disruption Near-Earth Neutral Line

7. 7Sept 8, 2010 Alfven Lab Seminar, EES, KTH Substorm signatures in the near-Earth tail Subtraction of the magnetosphere model T89 B-field for quiet times from GOES data Pseudobreakup Substorm GOES magnetic field data

8. 8Sept 8, 2010 Alfven Lab Seminar, EES, KTH Signatures of 10 substorms preceded by pseudobreakups IMF Bz AE index Tail Bh – Model Bh

9. 9Sept 8, 2010 Alfven Lab Seminar, EES, KTH Mapping of GOES tail position to the auroral oval Mapping of GOES tail position to the auroral oval

10. 10Sept 8, 2010 Alfven Lab Seminar, EES, KTH No delay of dipolarization: GOES maps to onset position

11. 11Sept 8, 2010 Alfven Lab Seminar, EES, KTH No dipolarization seen: GOES is always equatorward of oval

12. 12Sept 8, 2010 Alfven Lab Seminar, EES, KTH Reason for delayed dipolarization: Dawn- or duskward substorm expansion

13. 13Sept 8, 2010 Alfven Lab Seminar, EES, KTH Reason for delayed dipolarization: Equatorward oval expansion after onset

14. 14Sept 8, 2010 Alfven Lab Seminar, EES, KTH Dipolarization delay versus GOES mapped position in the oval Date GOES - main onset DistanceDipolarizationDelay GOES mapped position at substorm onset Propagation speed of dipolarization region Dec 6, 98 -0.04 MLT 29 mn Equatorward of onset 0.11 deg/min equatorward Dec 14, 98 -0.19 MLT 22 mn Equatorward of onset 0.10 deg/min equatorward Dec 3, 98 0.61 MLT 25 mn Equatorward of onset 0.08 deg/min equatorward Feb 24, 99 -0.80 MLT 26 mn Poleward of onset unclear (bad UVI image) unclear (bad UVI image) Jan 15, 99 -0.82 MLT 31 mn Equatorward of onset 0.08 deg/min equatorward Feb 25, 99 0.82 MLT 2 mn Nearly at onset 0.55 MLT/min duskward Jan 7b, 99 1.78 MLT - GOES always equatorward No dipolarization Dec 28, 98 -2.23 MLT 8 mn Dawnward of onset 0.33 MLT/min dawnward Dec 23, 98 -2.38 MLT 17 mn Dawnward of onset 0.10 MLT/min dawnward Jan 7a, 99 2.7 MLT 11 mn Duskward of onset 0.24 MLT/min duskward

15. 15Sept 8, 2010 Alfven Lab Seminar, EES, KTH Expansion of the tail dipolarization region Previous work shows, the magnetic field dipolarisation starts locally [Ohtani et al., 1991] and spreads azimuthally [Nagai, 1982; Liou et al., 2002], and radially outward [Jacquey et al. 1991; Ohtani et al., 1992] as well as inward [Ohtani, 1998]. onset tail onset Propagation speed of tail dipolarization region:  Azimuthal propagation speed: 0.22 MLT/min (Liou et al. [2002] found 0.37 MLT/min)  Earthward propagation speed: 0.09 deg/min (Liou et al. [2002] found 0.84 deg/min)

16. 16Sept 8, 2010 Alfven Lab Seminar, EES, KTH Results  The dipolarization at GOES starts when bright auroral region reaches GOES mapped position. This indicates, the expansion of auroral intensification region and the expansion of the tail dipolarization region are coupled. Thus, the small azimuthal expansion of the smallest substorms indicates an only limited spread of the tail dipolarization region.  For substorms preceded by pseudobreakups, the expansion of the tail dipolarization region in azimuthal direction is as fast as expected from regular substorms. The expansion of the dipolarization region in Earthward direction is 10 times smaller than expected from regular substorms. This is probably connected to a slow Earthward motion of the inner plasma sheet boundary after onset (equatorward motion of the oval boundary).

17. 17Sept 8, 2010 Alfven Lab Seminar, EES, KTH AE index

18. 18Sept 8, 2010 Alfven Lab Seminar, EES, KTH One month AE index data with pseudobreakups overlaid

19. 19Sept 8, 2010 Alfven Lab Seminar, EES, KTH AE index Superposed epoch plots for substorms of different strengths, centered around substorm onset. (Red, yellow, green and blue correspond to strong, medium, small and very small substorms) Substorms with pseudobreakups Substorms without pseudobreakups

20. 20Sept 8, 2010 Alfven Lab Seminar, EES, KTH Solar wind conditions

21. 21Sept 8, 2010 Alfven Lab Seminar, EES, KTH IMF magnitude, solar wind velocity and density IMF magnitude sw velocitysw density

22. 22Sept 8, 2010 Alfven Lab Seminar, EES, KTH Solar wind conditions: IMF Bz Substorms with pseudobreakups Substorms without pseudobreakups Superposed epoch plots for substorms of different strengths, centered around substorm onset.

23. 23Sept 8, 2010 Alfven Lab Seminar, EES, KTH Solar wind energy transfer into the magnetosphere

24. 24Sept 8, 2010 Alfven Lab Seminar, EES, KTH Loading-unloading substorm model 1.IMF Bz turns southward 1 hour before onset. 2.During the southward IMF period open magnetic field-lines are added via dayside reconnection. 3.When ”enough” energy has been stored in the magnetosphere via addition of open magnetic flux, this energy is released via a substorm. Growing region of open magnetic flux IMF Bz t substorm Dayside reconnectionNightside reconnection Substorm onset

25. 25Sept 8, 2010 Alfven Lab Seminar, EES, KTH Solar wind merging E-field Oval size Max AE Average AE Substorms without pseudobreakups Substorms with pseudobreakups growth-phase pseudobreakups Em integrated over the last three hours before onset versus a) oval size, b) maximal AE during substorm c) average AE during substorm. Em integrated over the last southward IMF period before onset versus time. E m = vB t sin 2 (Θ/2)

26. 26Sept 8, 2010 Alfven Lab Seminar, EES, KTH Polar cap signatures

27. 27Sept 8, 2010 Alfven Lab Seminar, EES, KTH PC potential drop Substorms with pseudobreakupsSubstorms without pseudobreakups Dayside nightside high latitude PC potential drop at nightisde proportional to AL [Lockwood et al., 2009] PC potential drop at dayside proportional to Em [Lockwood et al., 2009] 12 00

28. 28Sept 8, 2010 Alfven Lab Seminar, EES, KTH AE index, PC index and Em in comparison Superposed epoch plots for AE index, solar wind merging field Em, northern and southern PC index, centered around substorm onset. PC north AE index PC south Em field Substorms without pseudobreakups Substorms with pseudobreakups Winter PC index (here PC north) proportional to AE [Janzhura et al., 2007] Summer PC index (here PC south) proportional to Em [Janzhura et al., 2007]

29. 29Sept 8, 2010 Alfven Lab Seminar, EES, KTHSummary  Solar wind conditions: Typical solar wind conditions during growth- phase pseudobreakups and subsequent substorms include low IMF magnitude and solar wind velocity, and weakly southward IMF Bz.  Energy transfer into the magnetosphere: A necessary condition for growth phase pseudobreakups to occur is that the amount of energy transferred into the magnetosphere the hours before onset has not exceeded a certain limit.  Ionospheric parameters: AE index, PC indices, and PC potential drop values are low as compared to regular substorms.  Substorm characteristics: Substorms preceded by pseudobreakups are typically weak, and appear as isolated events after hours of low geomangetic activity. growth phase pseudobreakup