Solar Energetic Particle Events An Overview Christina Cohen

Solar Energetic Particle Events: An Overview Christina Cohen Caltech

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

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

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

Space Weather Intensity Spectra EPAM Composition Predictions Questions

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

Space Weather Intensity Spectra Composition Predictions Questions Wind/WAVES

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

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

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

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

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

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

Space Weather Intensity Spectra Composition Predictions Questions Characteristics - Intensity Rise Time n rise time - generally depends on longitude relative to flare n n n Fast=western Slow=eastern Jan 20, 2005 n n faster than most W 61 >100 Me. V

Space Weather Intensity Spectra Composition Predictions Characteristics - Intensity Rise Time n rise time - generally depends on longitude relative to flare n n n Fast=western Slow=eastern Jan 20, 2005 n n n faster than most W 61 >100 Me. V fluence in first few hours was greater than any other event since 1976 Questions

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

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

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

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

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

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

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

Space Weather Intensity Spectra Composition Predictions Questions Characteristics - Composition Variability mostly protons n heavy ions still important n n not predictable from proton measurements H O Fe

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

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

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

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

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

Space Weather Intensity Spectra Composition Predictions Current Predictive Capability n Tools neutron monitors n L 1 monitors (ACE RTSW) n • ESP events • peak events Solar - CMEs, Flares, Active Regions n Theoretical Understanding (models) n n But currently can’t predict SEP characteristics from solar observations Questions

Space Weather Intensity Spectra Composition Predictions Questions Current Predictive Capability n Current Techniques n shock arrival Average uncertainty in arrival time • 24 hrs in advance => 8. 9 hrs • 12 hrs in advance => 4. 6 hrs Vandegriff et al. 2005

Space Weather Intensity Spectra Composition Predictions Current Predictive Capability n Current Techniques shock arrival n ESP L 1 detection n • 30 -60 minutes warning Questions

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