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Energetic Particle Observations from Ulysses, STEREO, and ACE During December 2006 Solar Events

In December 2006, unique observations of energetic particles were made by the Ulysses spacecraft at high latitudes (>70ºS), coinciding with intense solar activity. This study compares these observations with previous measurements during solar maximum and simultaneous data from STEREO and ACE at 1 AU. Significant events included >50 MeV ions associated with coronal shocks and metric type-II radio bursts. The findings highlight the mechanisms of particle transport to high latitudes and provide insights into solar wind dynamics and particle acceleration during solar flares.

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Energetic Particle Observations from Ulysses, STEREO, and ACE During December 2006 Solar Events

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  1. DECEMBER 2006 SEP EVENTS: Ulysses, STEREO & ACE OBSERVATIONSOlga E. MalandrakiInstitute for Astronomy and Astrophysics, Nat. Oservat. Athens, Greece Collaborators: R. Marsden, C. Tranquille, ESTEC/ESA, The Netherlands, D. Lario, APL/JHU, USA, B. Heber, CAU, Kiel, Germany, R. A. Mewaldt, C. M. S. Cohen, SRL, Caltech, USA, L. J. Lanzerotti, NJIT, USA, R. B. Forsyth, IC, UK, H. A. Elliott, SRI, USA, A. Geranios, UOA, Greece

  2. Objective • Present unique energetic particle observations by Ulysses > 70ºS during intense solar activity in December 2006 • Compare with previous high latitude measurements obtained close to solar max • Compare with simultaneous in ecliptic observations by STEREO, ACE at 1 AU

  3. Unique Eventsof December 2006 >50 MeV ions Credit: NSO/Optical Solar Patrol Network Telescope All x-ray events associated with intense, metric type-II radio bursts, indicative of coronal shocks

  4. 5 Dec 13 Dec View from top View from side Angular separation with X9.0 flare location Ulysses footpoint : 70 deg ACE footpoint : 135 deg

  5. Velocity dispersion at Ulysses

  6. Radiation belt pass STEREO-B

  7. ULYSSES/ACE OBSERVATIONS

  8. Near-isotropic angular distributions at the onset (Ulysses)

  9. ULYSSES/STEREO-B OBSERVATIONS

  10. How do SEPs reach high latitude? • Field line connection? (Smith et al. 2001) -   Unlikely,    since Ulysses in fast wind and AR in slow wind • Accelerated by coronal shock? (Cliver et al. 1995) - Delay to ACE: 3.6 Hr (Dec 5) - Delay to Ulysses: 9.6 Hr - Coronal shock travel time: ~13 minutes • Cross field diffusion? (Zhang 2003; Dalla et al. 2003)    - possible, but no local evidence Credit: NSO/Optical Solar Patrol Network Telescope

  11. December 2006 SEP events • Unique observation of a high latitude event in the history of Ulysses mission during a period of relatively quiet and stable conditions in the heliosphere • Simple structure of the heliosphere and Ulysses in high-speed coronal hole flow exclude the possibility that low latitudes magnetic fields lines reached Ulysses • EP released when the propagating coronal waves reached high latitude magnetic field lines connected to Ulysses/ EP underwent perpendicular diffusion • Risephase of the event at STEREO & ACE in response to the X9.0 flare faster than at Ulysses  more diffusive transport to high latitudes and to 3 AU than to STEREO, ACE • ‘Reservoir effect’ observed late in the decay phase of the particle events • Malandraki et al., Astrophys. J.,704, 469,2009

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