Observational Constraints on Electron Heating at Collisionless Shocks in Supernova Remnants Cara Rakowski NRL J. Martin Laming NRL Parviz Ghavamian STScI

Hα emission from the shock front Non-radiative shocks: primarily Hα emission from the immediate shock front Radiative shocks: show O III, N II, S II etc from recombination zone downstream Raymond et al. 2003, ApJ 584, 770 Cygnus Loop

Ghavamian et al. 2002, ApJ 572, 888 HH broad H  narrow H  HH HH HH Hα narrow and broad components

Ghavamian et al. 2002, ApJ 572, 888 HH broad H  narrow H  HH HH HH Hα narrow and broad components

Ghavamian et al. 2002, ApJ 572, 888 broad H  narrow H  HH HH HH Hα narrow and broad components neutral H entering the shock: excited by electrons or protons, emits narrow Hα charge exchanges with shock heated protons creating hot neutrals that emit broad Hα V FWHM, broad → T p I B /I N → σ x, σ i → T e, T p (Chevalier, Kirshner & Raymond 1980 ApJ 235, 186)

T e /T p = 0.1 T e /T p = 0.5 T e /T p = 1.0 I B /I N (v shock, T e /T p ) van Adelsberg, Heng, McCray & Raymond astro-ph/ v3 optically thick Lyman α v shock = 635 km s -1 Ghavamian et al ApJ 547, 995 electron impact excitation and ionization are peaked functions of T e decreasing charge exchange at high velocities

V FWHM,broad (T e /T p, v shock ) van Adelsberg, Heng, McCray & Raymond astro-ph/ v3 At high v shock most protons are too fast to charge exchange, limiting further broadening.

M A for 3  G 10 5 K 1cm -3 50% neutral gas (T e /T p ) 0  (1/v s 2 ) T p  v s 2 T e =constant Ghavamian, Laming & Rakowski, 2007 ApJ 654, L69 Results from Hα observations of Supernova Remnants

more sophisticated treatment of post-charge exchange distribution functions van Adelsberg, Heng, McCray & Raymond astro-ph/ v3

cosmic ray lower hybrid waves upstream rest frame vsvs k || 2 / k  2  m e /m p B v group   v s v phase 2=e p2=e p (  e,p  eB/m e,p c) L~  /v s t=  /v s 2 m e v e 2 = m e D || t D ||  Bv s 2 (E 2 ) m e v e 2  B    1/B heating independent of both v s and B! 1 ─── 2 e ─ p+p+ Ghavamian, Laming, & Rakowski 2007 Figure 2

T e /T p  v 2 shock, T e constant? Lower hybrid waves (LHW) in a cosmic ray (CR) precursor CR diffusion length scale for heating, and LHW v group  v shock allows T e independent of v shock and B. LHW growth requires some B  w.r.t shock normal. If B  generated by B-field amplification, then at M A = , LHW growth will exceed modified Alfvén wave growth. Ghavamian, Laming & Rakowski, 2007 ApJ 654, L69 (first estimates) Rakowski, Laming & Ghavamian 2008 ApJ 684, 348 (kinetic growth rate)

extra slides

DEM L71, new long-slit spectra confirm I B /I N too low in most regions to be matched by current models. We suspect H is being ionized and excited by hot electrons in the CR precursor

Growth Rate Comparison lower hybrid wave kinetic growth rate non-resonant modified Alfvén wave growth rate maximum Alfvén wave growth rate Mach number at which lower-hybrid waves grow faster than modified Alfvén waves for  shocks:

Cosmic-ray precursor non-resonant modified Alfvén waves amplify B  M A decreases near shock lower-hybrid wave growth takes over, heating the resonant electrons parallel perpendicular Figure 3

Solar Wind Shocks interplanetary bow shocks in the solar wind show a relationship closer to T e /T p  1/v. this could be explained if the cosmic rays were non- relativistic picking up an extra factor of v s /c in the diffusion coefficient. Figure 4 data from Schwartz et al 1986

Ultimate Goal: detect SEPs by their effect on thermal electrons Multi-slit instantaneous EUV/UV Spectra Mission Concept: see poster Newmark et al. SP43A-07

Ultimate Goal: detect SEPs by their effect on thermal electrons Predicting ground-level SEP events Primary mission, detect seed particles prior to CME eruption available for acceleration to high energy SEPs Simultaneously the O VI and He II lines can be modeled to determine the electron to ion temperature ratio to test for rapid electron heating indicative (under our model) of SEP generated lower-hybrid waves Chianti simulated SOCS spectra UVCS spectrum from Raymond et al 2000, sees wings from shock heated ions

DEM L71, new long-slit spectra confirm I B /I N too low in most regions to be matched by current models. We suspect H is being ionized and excited by hot electrons in the CR precursor