Galactic and Anomalous Cosmic Rays in the Heliosheath József Kόta University of Arizona Tucson, AZ , USA Thanks to : J.R. Jokipii, J. Giacalone 21 st ECRS, Košice, September 2008 ● V-1 ● V-2

Motivation: where is the source ? is history repeating itself ?? ACR fluxes continued to increase beyond TS V. Hess 1912 Voyager-1 December 2004 Similar result from V-2 (2007) Source outside Shock

● Are Anomalous Cosmic Rays (ACRs) indeed accelerated at the solar wind termination shock (TS) ? Likely yes but ● Bluntness of TS counts ● Topology between Shock & Field lines counts

Heliosphere: our cosmic environment Pristine ISM Solar material Perturbed ISM TS 26 km/s ● V1

Global structure of Heliosphere GCR ACRACR SEP VLISM: partially ionized H,He 0.1/cc μG B ?

ACRs are accelerated at the solar wind Termination Shock Same Physics as SNR Diffusive Shock Acceleration: 1 st order Fermi Energy gain from crossing the shock many times ACRs SNR

LECP Low energy charged particles (Decker JHU-APL)

Voyager-1 after crossing the TS ACR fluxes continued to increase into the Heliosheath ● Temporal variaton (Florinski Zank,2006) ● Magnetic topology (McComas & Schwadron, Kόta & Jokipii) ● Combination of the two?

First Signature of Blunt Shock oVoyager-1 observed large beaming anisotropies seemingly from the sunward direction. oInterpreted in terms of multiple intersection between the Parker spiral field and the blunt TS oHint for a deformation of the shock (likely due to interstellar B).

How do we understand “anti-sunward” anisotropies? Magnetic field line may intersect the TS multiple times. V-2 V-1 Jokipii, Giacalone, and Kota 2004, Kóta and Jokipii 2004 Multiple intersection also explains the two population spectrum Displacement of the ‘nose’ helps

McComas and Schwadron (2006) Blunt Shock: acceleration at Flanks ? Short time for acceleration

Topological effects on ACR spectrum oAcceleration ineffective at the nose due to lack of time fof acceleration. oACR spectrum does not unfold at the TS oACR flux continues to increase into the heliosheath oCould have been anticipated

2-D Model: TS = Offset Circle oIn the modeling we select an offset sphere for the TS Another possibility is bullet shape (McComas & Schwadron, 2006) oNose region (V1 and V2) is similar in either case oDifferences can be expected for the tail region. Tail region turn effective for sphere and probably less effective for bullet shape. oConsider preferential injection at flanks

Blunt Shock (offset circle) perpendicular diffusion included (η=0.02) Polar contours of simulated 200keV fluxes & spectrum along the TS

2-DSimulation – Blunt shock Model: 2-D plane, TS offset circle, uniform injection at 10 keV, η=0.02 Radial variation at fixed azimuth: fluxes continue increase beyond TS V2 V1 V-2 V-1

Larger perpendicular diffusion: η=0.05 effect smaller but still there

Summary: ●V-1 ● Magnetic field lines cross the blunt TS multiple times. This explains: ● Upstream field-aligned anisotropies - away from the Sun (V-1) – TS offset helps - toward the Sun (V-2) if TS is offset ● Two-population spectrum: low energy particles are accelerated at nearby “fresh” shock. ACRs are accelerated farther away are still modulated at the TS, and continue to increase into the heliosheath. ● 2-D Shock differs from 1-D shock (topology) Think in 2 D (at least) ● Topology may be important at other shocks too. ●V-2

Motto: ● “Make everything as simple as possible, but not simpler “ “Topology counts”

Voyager-1 in the Heliosheath ● V-1 crossed the Termination Shock on December 16, 2004 Before Crossing: ● large beaming anisotropies from sunward direction ● large day-to-day variability ● ACRs still modulated – two-population!? After Crossing: ●small anisotropies ● small day-to-day variability ● ACRs still modulated ● Double power law spectra with break around few MeV/n (He:H=1:10) ● Voyager-2 crossed the TS on DOY 244, 2007

Voyager -1 & -2 reached the TS 2004/2007 Launched in 1977 B LECP CRS SW Plasma radio Interestingly in the same year as the theory of shock acceleration

Where is the Termination Shock ? E.C. Stone 2001 Very different methods all predict ~100 AU range Shock is not steady but moves in response of solar input

Uneven injection: preferential injection at flanks Injection at 10 keV, q~sin(θ)**2

Preferential injection at flanks contn’d