CIRs: Acceleration and transport to high latitudes

1. 2006 Shine Workshop, Zermatt Utah, August 2006 CIRs: Acceleration and transport to high latitudes József Kóta & Joe Giacalone w/ thanks to J.R. Jokipii The University of Arizona, Tucson, AZ 85721-0092 kota@lpl.arizona.edu

3. - Outline - • CIR accelerated particles appear as recurrent low-energy events • 1st polar pass of Ulysses: CIR events at high latitudes, where no similar variation in Vsw and/or B present. • Simulations for GCR and low energies • Energy loss and modulation for low-energy particles • Illustrative examples • Compressive acceleration • Summary/Conclusions

4. Ulysses observations • Recurrent variations in V & B • Corresponding dips in GCR • Enhancements at low energies – continue to be present to highest latitudes

5. Transport to high latitudes

6. Interpretation • Fisk field • Cross-field transport (Kóta & Jokipii, 1995,1999). - Parker’s equation - accelerated population wherever divV<0 - cross-field transport κ┴/κ║≈ 0.02-0.05 + Also explains why electrons lag behind ion events

7. Recurrent particle events at high latitudes: Simulation Low-energy ion/electrons Note delay for electrons Simulated Vsw, B, & GCR fluxes

8. electrons ions

9. Cooling along spiral field • Charged particles lose energy even if they move along the spiral field. • Reason curvature drift. More effective at tight spiral (no loss for radial B) dp/dt ~ p Δlnp ~ t VxB field Curvature drift against VxB electric field

10. Cooling: Numerical Examples • Parker spiral field at latitude 30o • Input: power law spectrum at 15 AU • Fokker-Planck equation for focused transport - Scatterfree: Dμ = 0 - Hemispherical (λ=inf.) - Diffusive: Dμ= w*(1-μ2)/2λ

11. Field-aligned Transport Skilling (1970), Ruffolo 1995), Isenberg (1997) Kóta & Jokipii (1997): Fokker-Planck equation: Coefficients: Net compression divided into parallel and perpendicular components parallel perpendicular inertial d/dt(ln B) Frozen in !!! d/dt (ln n/B)

12. Math • Transport coefficients for corotating field: Conservation

13. `Modulation’ for scatterfree propagation Scatterfree (Dμ=0, λ=inf.) Hemispherical (λ=inf.) Dashed: input at 15AU 15 AU 10 AU 5 AU 1 AU Note discontinuity at 15 AU

14. Scattering included Fluxes at different radial distances 1AU fluxes for different λ-s λ(AU) = 1.5, 3.5, 7.5, inf. 1, 5, 10, 15 AU

15. Compressive acceleration • Mason et al (2002) observed energetic particles that must had been accelerated at < 1 AU where shock had not yet been formed • Giacalone et al (2002) interpreted this in terms of compressive diffusion acceleration. Acceleration occurs wherever plasma is compressed (dn/dt > 0). It can be effective if VΔx/κxx < 1

19. Summary -- CIRs • CIR accelerated particles can reach high latitudes via cross field diffusion • Particles lose energy while moving along (curved) field lines even in scatterfree case • Compression acceleration may occur before shock is formed Zermatt/Matterhorn