SOHO/EPHIN Observations of the November 1, 2004 Solar Energetic Particle Event

1. SOHO/EPHIN Observations of the November 1, 2004 Solar Energetic Particle Event Raúl Gómez Herrero IDTRAP Meeting IEAP CAU Kiel, 3-4 August 2006

2. Electron Proton and Helium Instrument (EPHIN) onboard Solar and Heliospheric Observatory (SOHO) Instrumentation EPHIN SOHO/EPHIN Observations of the November 1, 2004 SEP Event 1/12

3. Electron Proton and Helium Instrument (EPHIN) onboard Solar and Heliospheric Observatory (SOHO) Instrumentation • Working since December 1995 • Time resolution ~1 min • Nominal geometric factor 5.14 cm2·sr • Energy range: • Electrons 0.25-10.4 MeV • H and He isotopes 4.3-53.0 MeV/n • Scientific data: • Counting rates (12 coincidence channels) • PHA (energy deposit) • A and B detector segmentation allows 2H and 3He discrimination SOHO/EPHIN Observations of the November 1, 2004 SEP Event 1/12

4. LASCO coronagraphs observed four CMEs during Nov.1, 2004 Nov 1, 2004 Coronal Mass Ejection • The fastest CME appeared in C2 field of view at 6:05 UT • Central position angle: 266º • Angular width: 146º • Speed: 925 km/s (linear fit) • Acceleration: -29.7 m/s2 • Estimated onset (1R): 05:37-05:47 UT • First EIT observation at 5:48 UT SOHO/EPHIN Observations of the November 1, 2004 SEP Event 2/12

5. First EIT Obs First C2 Obs • No X-ray flare observed between 5:40 and 6:10 UT Nov 1, 2004 Coronal Mass Ejection • Type III radio bursts observed by WIND/WAVES at 5:42 and 5:51UT The attenuation at frequencies > 2 MHz is consistent with the hypothesis of a source region occulted behind the limb SOHO/EPHIN Observations of the November 1, 2004 SEP Event 3/12

6. No X-ray flare observed between 5:40 and 6:10 UT Nov 1, 2004 Coronal Mass Ejection • Type III radio bursts observed by WIND/WAVES at 5:42 and 5:51UT SGD reports a group of type III bursts between 5:50-6:00 UT but careful examination of Culgoora and Learmonth spectrograms reveals a type II burst indicative of a shock wave propagating in the corona Heights from 2-fold Newkirk model (1st / 2nd harmonic) 100 MHz  1.36 / 1.68 RSun 35 MHz  1.91 / 2.60 RSun First EIT obs The attenuation at frequencies > 2 MHz is consistent with the hypothesis of a source region occulted behind the limb SOHO/EPHIN Observations of the November 1, 2004 SEP Event 3/12

7. 0688 (later) • Radio observations, the lack of X-ray flare and EIT images point to a backside source Nov 1, 2004 Coronal Mass Ejection • Four candidate AR behind the limb. (10684,10685,10682 and 10688) • Best candidate: NOAA AR 10684 (aprox. location: S04W124) • SOHO/MDI and SOHO/SWAN farside imaging do not offer concluding information SOHO/EPHIN Observations of the November 1, 2004 SEP Event 4/12

8. Energetic particle flux increases observed in all the EPHIN channels • Evidence of proton acceleration up to ~100 MeV. • Ion fluxes show clear velocity dispersion • Rise times (onset to max) ~30 min for electrons and  1 h for ions • e-folding decay times between 4 h for 3-10 MeV electrons and 9 h for 4-8 MeV protons. SEP Event - Temporal Profiles SOHO/EPHIN Observations of the November 1, 2004 SEP Event 5/12

9. ~3 MeV electron increase starts at 6:05 UT ± 2 min • ~53 MeV proton increase starts at 6:33 UT  5 min • Velocity dispersion analysis of PHA proton data provides a solar release time of 05:56 (6:04 UT including 8 min e.m. delay) • Particle injection began before the CME reached 4R from the Sun center • Estimated electron and proton injection times are simultaneous within ~10 minutes uncertainties(e- injection: ~ 6:00 UT) SEP Event - Particle Onset SOHO/EPHIN Observations of the November 1, 2004 SEP Event 6/12

10. Event averaged abundances (DOYs 306.3-307.7): • 4He/1H (5-25 MeV/n) = (2.0 ± 0.1)·10-3 • 3He/4He (5-25 MeV/n) = 0.06 ± 0.02 • Low 4He/1H ratio in the usual range for gradual (proton-rich) shock-associated events • Moderate 3He enrichment can be explained by 3He-rich seed population from October 30-31 SEP events (3He/4He ≥ 0.1) associated to multiple flares, type II bursts and middle speed CMEs from AR 10691(N12-13W19-36) SEP Event - Composition SOHO/EPHIN Observations of the November 1, 2004 SEP Event 7/12

11. Simple power law spectral indices reveal hard energy spectra: • (1H) ~2 (4He) ~2.4 • Rounded spectra are better fitted using power law modulated by a exponential: A·(E2 + 2mpc2E) -  ·exp(-E/E0), accordingly with diffusive shock acceleration theory of Ellison and Ramaty, 1985 SEP Event - Energy Spectra SOHO/EPHIN Observations of the November 1, 2004 SEP Event 8/12

12. 1H and 4He spectra become invariant early in the event ~Nov 1, 12:00 UT (CME height ~30 R) and remains nearly unchanged until the end of the event. This spectral invariance is commonly observed during the decay phase of gradual events (Reames et al. 1997) • Isotopic composition remains also nearly invariant • Spectral invariance is also observed during the previous event  possible IP structures providing magnetic bottle for particle trapping SEP Event – Composition and Spectral Evolution SOHO/EPHIN Observations of the November 1, 2004 SEP Event 9/12

13. Vsw = 420-350 km/s • No IP shock transit • There is no evidence of ICME or magnetic cloud signature, but the low temperature and smooth magnetic field region observed by ACE instruments between 306.75 and 308.25 could be related to solar ejecta corresponding to the 690 km/s halo CME observed by LASCO on October 30 16:54 UT SEP Event - IMF and Solar Wind SOHO/EPHIN Observations of the November 1, 2004 SEP Event 10/12

14. Interplanetary medium is already filled by ICMEs ejected during the previous days, especially from AR 10691 on October 30 and 31. • Previous CMEs can provide magnetic connection with the eastern (quasi-parallel) flank of a shock driven by Nov 1 CME CMEs Possible Scenarios for Particle Transport • This kind of guiding could also occur close to the Sun • Alternative scenarios: • Coronal shock wave intercepting magnetic footpoint (e.g. Cliver et al. 2005) • Cross-field transport(e.g. Cane and Erickson, 2002) SOHO/EPHIN Observations of the November 1, 2004 SEP Event 11/12

15. Heliospheric tomography from interplanetary scintillation data seems to support the hypothesis of a previous CME… (?) Possible Scenarios for Particle Transport SOHO/EPHIN Observations of the November 1, 2004 SEP Event 11/12

16. SEP Event observed by EPHIN on November 1, 2004 is associated to a 925 km/s CME, type III, and type II radio emission • The source active region is located at the backside of the Sun, probably in NOAA 10684, more than 30 degrees behind the West limb • Particle fluxes show prompt onset and particle injection began before the CME reached 4 R • The low 4He/1H~ 0.002 ratio is in the usual range for gradual events, while the moderate 3He enhancement can be explained by the existence of 3He-rich remnant population from previous impulsive events CONCLUSIONS SOHO/EPHIN Observations of the November 1, 2004 SEP Event 12/12

17. Ion energy spectra are hard ( ~ 2-2.5), and become nearly invariant early in the event • Type II burst points the existence of a coronal shock wave. This shock could intercept observer magnetic footpoint at the beginning of the event. However, the spectral invariance and long duration profiles seem to indicate a sustained magnetic connection between the observer and the source • IP medium is distorted by previously ejected CMEs. This CMEs can provide magnetic connection to the Nov 1 event source region and a magnetic bottle causing spectral invariance. However, IMF and SW data at 1 AU do not show clear evidence of ICME transit CONCLUSIONS SOHO/EPHIN Observations of the November 1, 2004 SEP Event 12/12

19. ACE SWEPAM ACE SWEPAM Bidirectional electrons? SOHO/EPHIN Observations of the November 1, 2004 SEP Event 19/12

20. LASCO LASCO SOHO/EPHIN Observations of the November 1, 2004 SEP Event Seminar 02/05/2006 20/12

21. AAA LASCO SOHO/EPHIN Observations of the November 1, 2004 SEP Event Seminar 02/05/2006 21/12

22. ETC SOHO/EPHIN Observations of the November 1, 2004 SEP Event Seminar 02/05/2006 22/12