Karl-Ludwig Klein

High-energy particles at and from the Sun Count rate [s -1 ] During the largest solar events measurements by particle detectors : –e -> 100 MeV (Moses et al 1989), maybe higher –p -> several GeV (neutron monitors on ground) EM emissions / interacting particles : –Gamma-rays from e : h -> 100 MeV, E>100 MeV –Gamma-rays from pion decay : p> 300 MeV Time scales of flares : fraction of s to tens of s, evidence that acceleration time scales are that short ! Photon energy [MeV] Vilmer et al 2003 AA 412, 865 Vilmer et al 1999 AA

Particle acceleration in solar flares

Particle acceleration associated with magnetic reconnection ? A simple flare. HXR from the low atmosphere (chromosphere) - e precipitated downward to n e > cm -3, bremsstrahlung with ambient p, h <energy(e) Radio emission (type III) from outward propagating e beams, =2 pe  n e, start < 400 MHz : n e < 10 9 cm -3, energy some keV  Acceleration region in the corona, injects particles downward (chromosphere) & upward (high corona, IP space) Vilmer et al Solar Phys

Particle acceleration associated with magnetic reconnection ? A simple scenario. Particle acceleration region in a reconnecting coronal current sheet : –Fragmented energy release regions (multiple CS). –Acceleration processes : direct E, turbulence, termination shock of reconnection jet. –Huge fluxes of NT particles, rapid acceleration to relativistic energies ? Vilmer et al Solar Phys Dauphin et al AA 468, 273

Supporting evidence : energy transport from the corona to the chromosphere Time profiles : thermal response of the chromosphere (H  ), HXR &  waves from NT electrons Fast energy transport; NT particles carry major fraction of flare energy 1 min Trottet et al A&A 356, 1067

Supporting evidence : polarisation of optical line emission Linear polarisation of optical lines by the impact of NT particles (or their return current) THEMIS H , H  : excitation by particle beams (directly or through return current) Hénoux & Karlicky 2003 ; Karlicky & Hénoux 2002 ; Xu et al ApJ 631, 618 Map of linear polari- sation (colour) on top of H  intensity and mag field (contours) :

Coronal mass ejections (CMEs), flares, and the origin of large solar energetic particle events in space

High-energy particles at and from the Sun : gamma-ray analysis of a large flare Kiener et al A&A 445, 725 h >150 keV (e bremsstr.) h >500 keV (e bremsstr.) h =(7-15) MeV (e bremsstr.) h =4.4 & 6.1 MeV ( 12 C, 16 O) h =2.2 MeV (n+p-> 2 H) Count rate [s -1 ] Time [s] INTEGRAL/SPI measurements of  R line & continuum emission : evolving CONT/line ratio => e & ions accelerated together, but proportions vary during event Evolving 12 C/ 16 O line ratio : diff. target abundances at diff. times => flare may comprise time-extended (min - tens of min - hours) particle acceleration in different regions.

CME, shock waves, magnetic reconnection, and large SEP events CME and particle acceleration : shock wave, reconnection in the post-eruptive corona Numerical resistive MHD (2.5 D) model Bright emission from a “plasma sheet”, repeated plasmoid formation, in- ward and outward motion : plasmoids at O-type points, X-type points in between Riley et al ApJ 655, 591 Site(s) for SEP acceleration in the magnetically stressed post-CME corona ?

Do fast CMEs produce SEP in the absence of « flares » ? Marqué et al ApJ 642, 1222 Attempt to isolate pure CME- shock-events : –Fast (  >700 km/s) west-limb CME (SoHO) : likely to drive shock. –EUV manifestations on disk, but no metric radio emission : no evidence for particle acceleration related to a flare (3 events ). SEP from the CME shock ?

Marqué et al ApJ 642, 1222 Attempt to isolate pure CME- shock-events : –Fast (  >700 km/s) west-limb CME (SoHO) : likely to drive shock. –EUV manifestations on disk, but no metric radio emission : no evidence for particle acceleration related to a flare (3 events ). SEP from the CME shock ? –None detected at GOES. –SoHO/COSTEP & ACE/EPAM: weak (deka-MeV protons, hecto-keV electrons). Indication that CME shock alone is NOT an efficient SEP accelerator at these energies ! Do fast CMEs produce SEP in the absence of « flares » ?

Energetic particles in the corona and IP space during a large SEP event Nançay RH : synchrotron radiation of relativistic electrons (  1 MeV) in CME-related loops, while CME still occulted Energetic electrons accelerated in the aftermath of CME (post-CME current sheets ?) Maia et al 2007 ApJ 660, 874 : large SEP event of 2001 April 15

Injection time profile of the escaping electrons very similar to that of the synchrotron emitting electrons in the corona. Release starts some min after the first radiative signatures of particle acceleration in the corona (together with relativistic p; Bieber et al 2004 ApJ 601, L103 ). Hint to particle acceleration in the magnetically stressed corona in the aftermath of a CME (see also Klein et al 1999 AA 348, 271; Laitinen et al 2000 AA, 360, 729; Klein & Trottet 2001, Spa Sci Rev 95, 215). Energetic particles in the corona and IP space during a large SEP event ACE : e ( ) keV Injection time profile : Maia et al 2007 ApJ 660, 874

Open questions - outlook Assess the respective role of CME and flares in energetic particle acceleration: acceleration, transport in the corona and IP space. Investigate the high-energy limit of accelerated particle spectra in the corona and IP space. Investigate acceleration processes and seed populations by in situ measurements. The tools : –STEREO : bidirectional view on CME (longitudinal extent), shocks, SEP –SMESE : FIR,  R of HE particles & energy transport in flares, CME –Spectral imaging cm-to-m- : energetic particles, localisation of their acceleration sites (dm-, never imaged before) and their synchrotron emitting regions : FASR, CnRH(, NRH) –Solar Orbiter / Sentinels : SEP, shocks & seed populations in the inner heliosphere (to minimise distorsion of SEP profiles by IP transport) Crucial : accompanying observations (HXR, radio) of energetic particles in the solar atmosphere to ensure a close coupling between in situ and remote sensing measurements.