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Solar Energetic Particle Events: An Overview Christina Cohen Caltech.

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Presentation on theme: "Solar Energetic Particle Events: An Overview Christina Cohen Caltech."— Presentation transcript:

1 Solar Energetic Particle Events: An Overview Christina Cohen Caltech

2 Overview of the Overview Space Weather and SEP events Why? Tools we can use Characteristics of interest Intensity (peak, rise time, duration) Spectra Composition Current predictive capability Current questions for study

3 Space Weather & SEP Events Why? Danger to astronauts, instruments, power grids, etc Understanding enables predictions Tools at our disposal SEPs (ions, electrons) Spacecraft (ACE, Wind, SoHO, GOES) Neutron monitors Solar CMEs (LASCO) X-ray (SXI, GOES, RHESSI) Other (MDI, EIT, TRACE...) Radio (WAVES, ground-based) Space Weather Intensity Spectra Composition Predictions Questions

4 Space Weather & SEP Events Space Weather Intensity Spectra Composition Predictions Questions LASCO EITMDI ACE ULEIS-SIS GOES/XRAY

5 Space Weather Intensity Spectra Composition Predictions Questions EPAM

6 Space Weather Intensity Spectra Composition Predictions Questions EPAM <4 R s LASCO CME time-height profile

7 Space Weather Intensity Spectra Composition Predictions Questions Wind/WAVES

8 Characteristics - Intensity Variability Varies with everything event time Space Weather Intensity Spectra Composition Predictions Questions

9 Characteristics - Intensity Variability Varies with everything event time species Space Weather Intensity Spectra Composition Predictions Questions Oxygen Protons

10 Characteristics - Intensity Peak Limitations streaming limit Reames & Ng 1998 proton-generated turbulence limits intensities Space Weather Intensity Spectra Composition Predictions Questions

11 Characteristics - Intensity Peak Limitations streaming limit Reames & Ng 1998 proton-generated turbulence limits intensities All bets off at ESP events Space Weather Intensity Spectra Composition Predictions Questions

12 Characteristics - Intensity Peak Limitations Exceptions - Jan 20, 2005 Space Weather Intensity Spectra Composition Predictions Questions

13 Cane et al. 1988 Characteristics - Intensity Rise Time rise time - generally depends on longitude relative to flare Fast=western Slow=eastern Space Weather Intensity Spectra Composition Predictions Questions

14 Characteristics - Intensity Rise Time rise time - generally depends on longitude relative to flare Fast=western Slow=eastern Jan 20, 2005 faster than most W61 Space Weather Intensity Spectra Composition Predictions Questions >100 MeV

15 Characteristics - Intensity Rise Time rise time - generally depends on longitude relative to flare Fast=western Slow=eastern Jan 20, 2005 faster than most W61 >100 MeV fluence in first few hours was greater than any other event since 1976 Space Weather Intensity Spectra Composition Predictions Questions

16 CME-driven shocks strong shocks - Fermi acceleration Space Weather Intensity Spectra Composition Predictions Questions Lee 2005 Characteristics - Intensity Theoretical Understanding

17 CME-driven shocks strong shocks central meridian (nose of shock) gives largest increase Space Weather Intensity Spectra Composition Predictions Questions Zank et al. 2001 Characteristics - Intensity Theoretical Understanding 4 of the top 6 events of 1997-2004

18 Characteristics - Spectra Variability most large events show roll-off Space Weather Intensity Spectra Composition Predictions Questions Oxygen

19 Characteristics - Spectra Variability most large events show roll-off power law events - problem at high energy Space Weather Intensity Spectra Composition Predictions Questions

20 Characteristics - Spectra Variability most large events show roll-off power law events - problem at high energy Space Weather Intensity Spectra Composition Predictions Questions

21 Characteristics - Spectra Theoretical Understanding Power law determined by shock strength Roll-off determined by escape, species dependent Space Weather Intensity Spectra Composition Predictions Questions Li et al. 2005 Lee 2005 Fe CNO H Kinetic energy (MeV/n)

22 Characteristics - Composition Variability mostly protons Space Weather Intensity Spectra Composition Predictions Questions H He Fe O C x 10

23 Characteristics - Composition Variability mostly protons heavy ions still important not predictable from proton measurements Space Weather Intensity Spectra Composition Predictions Questions HOFe

24 Characteristics - Composition Variability mostly protons heavy ions still important not predictable from proton measurements very variable Space Weather Intensity Spectra Composition Predictions Questions

25 Characteristics - Composition Variability mostly protons heavy ions still important not predictable from proton measurements very variable dependent on energy Space Weather Intensity Spectra Composition Predictions Questions

26 Characteristics - Composition Theoretical Understanding Shock acceleration Variations depend on Q/M Space Weather Intensity Spectra Composition Predictions Questions

27 Characteristics - Composition Theoretical Understanding Shock acceleration Variations depend on Q/M seed population (not SW) Space Weather Intensity Spectra Composition Predictions Questions

28 Characteristics - Composition Theoretical Understanding Shock acceleration Variations depend on Q/M seed population (not SW) flare suprathermals for high Fe events?? Space Weather Intensity Spectra Composition Predictions Questions Tylka et al. 2005 Still don’t know how to generate element-dependent power law slopes

29 Current Predictive Capability Tools neutron monitors L1 monitors (ACE RTSW) ESP events peak events Solar - CMEs, Flares, Active Regions Theoretical Understanding (models) But currently can’t predict SEP characteristics from solar observations Space Weather Intensity Spectra Composition Predictions Questions

30 Current Predictive Capability Current Techniques shock arrival Space Weather Intensity Spectra Composition Predictions Questions Average uncertainty in arrival time 24 hrs in advance => 8.9 hrs 12 hrs in advance => 4.6 hrs Vandegriff et al. 2005

31 Current Predictive Capability Current Techniques shock arrival ESP L1 detection 30-60 minutes warning Space Weather Intensity Spectra Composition Predictions Questions

32 Current Questions for Study Acceleration Details of the process Requirements Pre-conditioning Turbulence from previous events Suprathermal population (flares) Solar signatures What feature? CME brightness/speed? Flare size/duration? future missions - STEREO, Sentinels Space Weather Intensity Spectra Composition Predictions Questions

33 Space Weather & SEP Events Space Weather Intensity Spectra Composition Predictions Questions WAVES Radio


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