Project:Understanding propagation characteristics of heavy ions to assess the contribution of solar

flares to large SEP eventsPrincipal Investigator: G. M. Mason, JHU / Applied Physics Laboratory

Co-Investigators:

C. M. S. Cohen and R. A. Mewaldt, California Institute of Technology

G. Li, University of California Berkeley

M. I .Desai, Southwest Research Institute, San Antonio

D. K. Haggerty, JHU / Applied Physics Laboratory

Collaborators:

R. A Leske, California Institute of Technology

G. Zank, University of California, Riverside

LWS Focus Team on Flares particle accelerations near the Sun and Contribution to large SEP events

JHU/Applied Physics Lab., June 10-11, 2008

From: Reames, D. V. (1995), Solar Energetic Particles: a paradigm shift, Rev. Geophys., 33, 585-589.

In all three cases the onsets agree best when H and He have the same energy/nuc. (This is perhaps different from the events shown in Mason et al. ). It suggests that the injection profiles are similar, that this profile and velocity dispersion controls the onset, and that there is little scattering at the onset of this event (at least at the >10 MeV energies shown here). The decay phases all agree better if He with ~0.5 of the H energy is used, indicating that scattering is important then and that α ﾅ 1 as inferred from the high-energy charge state data and the Fe/O shift. This suggests that there are at least some events where we can infer that scattering plays a minor role during the onset, and that we therefore have a handle on the initial injection profile. The more ragged profile at lower energies (Protons #1) also suggest that scattering is more important here. I cannot eliminate the possibility of geomagnetic influences at the lowest energy.

Rev 8/7/06

Electron beam event

7. Apr 21, 2002 01:51 S14W80 X1/1F

Gradual release from shock scenario--

This smooth arrival time in 1/v

Requires an equally smooth 1/v release from shock if there is little scattering

Sollitt thesis event

Dec 13, 2006 02:40 S05W23 X3/4B

Similarity of Fe time-intensity profile to O at 2x the kinetic energy -- • unexpected result of study is similarity of time-intensity profiles for O and Fe at different energies -- seen for both ~0.5 MeV/n and 10 MeV/n ions

• for the rise phase --

•at low energies (~0.5 MeV/nucleon) this occurs in >~ 50% of the cases

• at high energies (~ 10 MeV/nucleon) this occurs in >~ 70% of the cases

• in the decay phase occurs in >~75% of the cases

Fokker-Planck equation scenario for Fe/O ratio behavior --• for identical release profiles, time-intensity profile depends only on the particle diffusion coefficient:

• Since (A/Q) for Fe is roughly twice that for O, its diffusion coefficient will be larger than that for O if > 0. For the two diffusion coefficients to be equal for O speeds of ~1.4 that of Fe, ~ 0.5, a value seen in some other studies

• Although the IP scattering may hide much of the release information, the delayed arrival seen in almost 80% of the ion events could be due to, eg, the location of the accelerating shock (e.g. Kahler 1994)

€

κ =1

3vλ = Cv v

A

Q

⎛

⎝ ⎜

⎞

⎠ ⎟γ

Shock release scenario for Fe/O ratio behavior --• Fe escapes the shock trapping region earlier since its diffusion coefficient is larger than that for O at the same MeV/n: (is MFP near shock)

• Since (A/Q) for Fe is roughly twice that for O, its diffusion coefficient will be larger than that for same speed O if > 0.

• BUT if there is little scattering in the IPM, the Fe must be released from the shock at just the right time earlier than O such that the O will just catch up with it when the 2 particle populations cross 1 AU, e.g. 6.4 hours earlier at 0.5 MeV/n, 1.2 hrs earlier at 10 MeV/n etc.

• while possible, this does not seem likely for a broad range of energies such as observed here

€

κ =1

3vλ = Cv v

A

Q

⎛

⎝ ⎜

⎞

⎠ ⎟γ

Other properties of events with κdominated onsets --

• correlated with GOES peak proton flux• no particular correlation with longitude

Investigation strategy:

• since flare contributions expected to occur near start of event, will emphasize rise phases although modeling covers entirety of each event

• divide events into 2 groups: (a) dominated by IP scattering, (b) little or not IP scattering (may be energy dependent)

• focus on Western Hemisphere events to simplify acceleration/ transport variables

Investigation strategy:• IP scattering dominated events:

• near equality of time-intensity profiles at different energies (but same κ) requires IP scattering dominates other transport effects -- this places an upper limit on .

• rise time of time-intensity profile will set a lower limit on .

• with defined to a range of values, use anisotropy data to further constrain

• with these constraints, use model to explore 1 AU signatures of (1) flare release (2) shock acceleration only, and (3) combined flare and shock accelerated particles.

Investigation strategy:• Events with little or no IP scattering:

• identifiable since particle arrivals organized by velocity, not diffusion coefficient

• several events show this behavior for whole event (June 4, 1999; Nov. 4, 2003), especially at higher energies, in other cases for rise phse (Jan 20, 2005)

• these events give best chance of deducing source function since the IP transport is simple.

• can provide this source function to other focus team groups