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Review of Observations of Particles From Solar Flares and Their Clues to the Structure of the IMF

Discover insights into solar flare particles and the interplanetary magnetic field's structure based on observations and models. Explore issues like velocity dispersion, particle injections, and event variations.

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Review of Observations of Particles From Solar Flares and Their Clues to the Structure of the IMF

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  1. Review of Observations of Particles From Solar Flares and Their Clues to the Structure of the IMF Joe Mazur The Aerospace Corporation Glenn Mason Johns Hopkins/APL Joe Dwyer Florida Institute of Technology Joe Giacalone & Randy Jokipii University of Arizona Ed Stone California Institute of Technology

  2. Introduction • Energetic ions from solar flares sometimes arrive at Earth with velocity dispersion that allows us to see individual particle injections from active regions at the sun. • The particle events often have drop-outs in intensity across all energies that are an effect of the structure of the interplanetary magnetic field, and not of particle release at the flare source. • This talk will briefly review the observations and their interpretation using a model magnetic field that was developed to interpret the transport of energetic particles above the ecliptic plane via meandering field lines. 2

  3. ~10 seconds Velocity dispersion is common to many acceleration sites Field-aligned beams in aurora: propagation distance ~103 km GEODESIC rocket flight data courtesy of J. Clemmons Drift echoes from substorms: propagation distance ~105 km CRRES/MICS data courtesy of J. Fennell 3

  4. Velocity dispersion in energetic particles from solar flares • Propagation distance ~108 km • Multiple particle injections from a solar active region • Particle intensity often varies by >10x during an event • Sometimes do not observe the entire injection Mason, Mazur, & Dwyer ApJ Letters 525, L133-L136,1999 4

  5. Solar flares & escaping ions • Events have been studied since the 1970’s • Enhanced in 3He (~1000x), Ne-Fe (~10x), trans-Fe (~1000x) compared to solar corona • Sometimes fully stripped up to Si • Beams of 10-100 keV electrons • Gyroresonant wave-particle interaction in a 3-5 MK plasma may account for enrichments (3He: Temerin & Roth 1992, Ne-Fe: Miller et al. 1993) M. Aschwanden, Space Sci. Rev. 101, 1-227, 2002 5

  6. Glimpses of small-scale (~1 hour) variations in solar energetic particles Anderson & Dougherty, Solar Phys. 103, 165-175, 1986. Buttighoffer, Astron. & Astrophysics 335, 295-302, 1998 6

  7. Glimpses of small-scale variations in solar energetic particles McCracken & Ness, JGR 71, pp. 3315-3318, 1966 7

  8. Ultra-Low Energy Isotope Spectrometer • 0.02-10 MeV/nucleon • Dual time-of-flight measurements for improved mass resolution • m/m ~ 0.03 8

  9. Mass 3He 9 Time

  10. A new look with ULEIS sensitivity • New views of the time-dependence of solar particle events • Low-energy threshold so an event lasts many hours • Large collecting area for low-intensity events that previous instruments would have missed 10

  11. Puzzling cases of “missing” ions Mason, Mazur, & Dwyer ApJ Letters 525, L133-L136,1999 11

  12. Time& spatial scales of events • 25 events 11/97 to 7/99 • Tallied duration of “sub-intervals” • Factored in solar wind speed to convert to a spatial size • Edges of drop-outs as sharp as ~2 minutes (~5x104 km or ~ few gyroradii of 1 MeV/n 56Fe+18) Mazur et al. ApJ Letters 532, L79-L82, 2000 12

  13. CME-related events • Events associated with large coronal mass ejections do not have drop-outs Reames et al., ApJ, 466, 1996 13

  14. Survey results Solar wind correlation length: Matthaeus, Goldstein, & King, JGR 91, 59-69, 1986 14

  15. Suprathermal electrons • Common features in ions and suprathermal electrons (<1.4 keV) (akin to electron obs. of Anderson & Dougherty 1986) • Gosling et al. (2004) showed 2 events where the ions had dropouts but the electrons did not, possibly indicating a more uniform and/or broad electron source ions electrons Gosling et al. ApJ 614, 412-419, 2004 15

  16. Simultaneous Wind/ACE observations C-Fe C-Fe • Simultaneous observations of the same flare injection on 12 August 2000: ACE & Wind spacecraft • The later arrival of empty flux tubes at Wind is consistent with solar wind convection UT 16

  17. Numerical simulations of particle transport • Model field used to study propagation of particles from corotating interaction regions to high heliographic latitudes (Giacalone 1999) • Model was based on earlier work by Jokipii & Parker (1968) and Jokipii & Kota (1989) • Random motion of field line footpoints in the photosphere over ~4x104 km, time scales of ~1 day 17

  18. The model followed the trajectories of 8 keV/n to 20 MeV/n oxygen from an impulsive flare • The particles traveled through pre-existing IMF structures • After ~1 day, ions were still present inside 1 AU and populated field lines spanning ~10º in longitude Giacalone, Jokipii, & Mazur, ApJ Lett. 532, 2000 18

  19. Simulated velocity dispersion & time-dependence with two different source sizes • Same realization of the magnetic field • Large sources (corresponding to a CME shock) generate continuous event profiles Giacalone, Jokipii, & Mazur, ApJ Lett. 532, 2000 19

  20. Closer look at dropout “edges”: iron 20

  21. Closer look at dropout “edges”: iron At 1700Z: B ~ 24 nT Vsw ~ 580 km/sec 21

  22. More examples, viewed with iron

  23. Questions • What observables in the 1 AU solar particle data might be used to establish the source of these dispersionless features (i.e. turbulence or field-line mixing from footpoint motion at the sun)? • What inner heliosphere measurements of the IMF and of the energetic particles, on Sentinels for example, would clearly establish the origin of these features? • Are the Ulysses observations of Jovian electrons as far as ~2 AU from Jupiter (McKibben et al. 2006) a valuable constraint on either the turbulence or random walk model? • What other observables in these data would be of use? (solar cycle dependence; statistics of the scale of the ‘dropout’ edges)

  24. New Capability: Advanced Composition Explorer • ACE launched in August 1997 • The ACE objective is to collect samples of matter in the solar system using large instruments • We do the collecting by letting the matter come to ACE and transmitting the results to Earth 24

  25. 3He-rich Solar Flares 3He • Discovered in late 1960s • 3He/4He ratio in solar wind ~5x10-4 • The events drew attention because 3He/4He> 0.1 without any accompanying 2H or other secondaries as one might expect from spallation in the solar atmosphere • Later found enhancements of heavy ions up to iron by factor of 5-10 as well as: • Impulsive electron events • Scatter-free propagation • Often lack of any flare association on Sun • Sometimes ions fully stripped of electrons 4He Mason et al. ApJ 574, 1039--1058, 2002 25

  26. ACE Survey of Flare Spectra • Searched for periods with clear flare velocity dispersion • Deleted events with local acceleration • Required complete observation of event (i.e. that ACE remained connected to it) for whole energy range of instrument • Cases often involved multiple injections; each event separated, and fluences calculated Mason, Dwyer, & Mazur ApJ Lett. 545, 2000 26

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