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Solar Energetic Particle Events: An Overview. Christina Cohen Caltech. 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

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Presentation Transcript
overview of the overview
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
space weather sep events

Space Weather Intensity Spectra Composition Predictions Questions

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 sep events1

Space Weather Intensity Spectra Composition Predictions Questions

Space Weather & SEP Events

MDI

EIT

LASCO

LASCO

GOES/XRAY

ACE

ULEIS-SIS

slide6

Space Weather Intensity Spectra Composition Predictions Questions

EPAM

LASCO CME time-height profile

<4 Rs

slide7

Space Weather Intensity Spectra Composition Predictions Questions

Wind/WAVES

characteristics intensity variability1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityVariability

Oxygen

  • Varies with everything
    • event
    • time
    • species

Protons

characteristics intensity peak limitations

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityPeak Limitations
  • streaming limit Reames & Ng 1998
    • proton-generated turbulence limits intensities
characteristics intensity peak limitations1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityPeak Limitations
  • streaming limit Reames & Ng 1998
    • proton-generated turbulence limits intensities
    • All bets offat ESP events
characteristics intensity rise time

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityRise Time
  • rise time - generally depends on longitude relative to flare
    • Fast=western
    • Slow=eastern

Cane et al. 1988

characteristics intensity rise time1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityRise Time
  • rise time - generally depends on longitude relative to flare
    • Fast=western
    • Slow=eastern
  • Jan 20, 2005
    • faster than most
    • W61

>100 MeV

characteristics intensity rise time2

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityRise Time
  • rise time - generally depends on longitude relative to flare
    • Fast=western
    • Slow=eastern
  • Jan 20, 2005
    • faster than most
    • W61
    • >100 MeV fluencein first few hours was greater than any other event since1976
characteristics intensity theoretical understanding

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityTheoretical Understanding
  • CME-driven shocks
    • strong shocks - Fermi acceleration

Lee 2005

characteristics intensity theoretical understanding1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - IntensityTheoretical Understanding

Zank et al. 2001

  • CME-driven shocks
    • strong shocks
      • central meridian (nose of shock) gives largest increase

4 of the top 6 events of 1997-2004

characteristics spectra variability

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - SpectraVariability
  • most large events show roll-off

Oxygen

characteristics spectra variability1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - SpectraVariability
  • most large events show roll-off
  • power law events - problem at high energy
characteristics spectra variability2

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - SpectraVariability
  • most large events show roll-off
  • power law events - problem at high energy
characteristics spectra theoretical understanding

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - SpectraTheoretical Understanding
  • Power law determined by shock strength
  • Roll-off determined by escape,species dependent

Li et al. 2005

CNO

Lee 2005

H

Fe

Kinetic energy (MeV/n)

characteristics composition variability1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - CompositionVariability
  • mostly protons
  • heavy ions still important
    • not predictable from proton measurements

H

O

Fe

characteristics composition variability2

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - CompositionVariability
  • mostly protons
  • heavy ions still important
    • not predictable from proton measurements
    • very variable
characteristics composition variability3

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - CompositionVariability
  • mostly protons
  • heavy ions still important
    • not predictable from proton measurements
    • very variable
    • dependent on energy
characteristics composition theoretical understanding1

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - CompositionTheoretical Understanding
  • Shock acceleration
    • Variations dependon Q/M
    • seed population (not SW)
characteristics composition theoretical understanding2

Space Weather Intensity Spectra Composition Predictions Questions

Characteristics - CompositionTheoretical Understanding
  • Shock acceleration
    • Variations dependon Q/M
    • seed population (not SW)
    • flare suprathermals for high Fe events??

Still don’t know how to generate

element-dependent power law slopes

Tylka et al. 2005

current predictive capability

Space Weather Intensity Spectra Composition Predictions Questions

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
current predictive capability1

Space Weather Intensity Spectra Composition Predictions Questions

Current Predictive Capability
  • Current Techniques
    • 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

current predictive capability2

Space Weather Intensity Spectra Composition Predictions Questions

Current Predictive Capability
  • Current Techniques
    • shock arrival
    • ESP L1 detection
      • 30-60 minutes warning
current questions for study

Space Weather Intensity Spectra Composition Predictions Questions

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