Diagnostics and constraints for relativistic electron and ion acceleration in solar flares

1. Diagnostics and constraints for relativistic electron and ion acceleration in solar flares N. Vilmer LESIA –Observatoire de Paris Ascona_June 7-11 2005

2. X/ -ray spectrum Thermal components T= 2 10 7 K T= 4 10 7 K Electron bremsstrahlung Ultrarelativistic Electron Bremsstrahlung -ray lines (ions > 3 MeV/nuc) SMM/GRS Phebus/Granat Observations GAMMA1 GRO GONG Pion decay radiation (ions > 100 MeV/nuc) sometimes with neutrons RHESSI Energy range

3. -ray and neutron event on 03/06/82 • (from Chupp et al, 1987): -Time extended neutron production at the Sun (~ 600s) • First GeV protons accelerated in t <16s at the beginning of the flare • Neutron Emissivity at the Sun: 7.4 1031 E–2.4 Neutrons/MeV/sr for 100<E<2000 MeV • - Spectral slope in agreement with the one deduced from neutron decay proton measurements

4. 24 May solar flare: GOES X9.3, N36 W76 One of the largest neutron event: N>100 MeV= 3.5 1030 n sr-1 Impulsive phase 75 MeV (2nd peak) Extended phase, duration > 8 minutes: High-energy  -rays  100 MeV Pion-decay radiation from 2nd peak of the impulsive phase -ray and neutron event on 24/05/90

5. -ray and neutron event on 24/05/90 From Talon et al., 1993 Debrunner et al 1997 High Energy -rays Solar neutrons PHEBUS/GRANAT observations Deduced solar neutron production time profile (i.e. pion time profile) NM CLIMAX observations of solar neutrons and prediction for a time extended neutron production Spectral evolution of high-energy -rays

6. Background subtracted count spectra From PHEBUS/GRANAT Full line: one of the best fits with electron and pion contributions Dotted line: electron contribution -ray lines Background subtracted count spectrum From 300 keV to 100 MeV Full line: one of the best fits with one electron bremsstrahlung component & pion contribution Dotted line: electron component Electron bremsstrahlung component: Ae= 1 10 5 = 2 Eroll= 40 MeV Proton component: =2 Ntot= 8 1031 Emax= 750 MeV Vilmer et al, 2003

7. Proton spectra and numbers from pion decay radiation and -ray line radiation and neutron observations? • Do we have a single energetic ion population from a few MeV/nuc to a few GeV/nuc

8. Ion spectrum with =2 from a few Mev to Emax : no compatibility • Ion spectrum with =3 from a few Mev to Emax : only with Emax = 750 MeV BUT GeV neutron production!! • Ion spectrum with =4 from a few Mev to Emax : OK if Emax > 2 GeV for spectra 1 to 3 BUT not enough pion production for spectrum 4!! • No single shape of energetic ions from MeV to GeV • Evidence of spectral breaks? Other forms of accelerated energetic spectra? • Also found for other events (e.g. Kocharov) • (see some of the simulations of particle acceleration by Dauphin et al)

9. X/ -ray spectrum Thermal components T= 2 10 7 K T= 4 10 7 K Electron bremsstrahlung Ultrarelativistic Electron Bremsstrahlung -ray lines (ions > 3 MeV/nuc) Phebus/Granat observations Pion decay radiation (ions > 100 MeV/nuc) sometimes with neutrons RHESSI Energy range

10. Bremsstrahlung and Synchrotron Emitting Electrons (I) • Simple relationship between the spectral indexes of cm-mm and HXR/GR producing electrons • Spectral index  from X-ray obs Thick target production from electrons • Electron flux: F(E,t) x from X-ray obs • Simple relationship between electron flux in the X-ray source and instantaneous number of electrons in the gyrosynchrotron emitting source (r) F(E,t) ~ N(E,t)/T(E) with T(E) escape time r ~ x =  + 1 • Gyrosynchrotron Note also: obs ~ L2 B Higher frequencies from higher energy electrons

11. Bremsstrahlung and Synchrotron Emitting Electrons (II) • Mm-wave emission (86 GHz) produced by high energy electrons (1 MeV) with a flatter spectrum than 100 keV X-ray spectrum (e.g. Kundu et al, 1994, White, 1999) • Early in the flare: production of relativistic electrons on short time scales • 2 components of electron populations or result of acceleration process?

12. Electron-Dominated Events • First observed with SMM (Rieger et al, 1993) • Short duration (s to 10 s) high energy (> 10 MeV) bremsstrahlung emission • No detectable GRL flux • Photon spectrum > 1 MeV (X-1.5—2.0) • For 2 PHEBUS events • if Wi>1MeV/nuc  We>20 keV • No detectable GRL above continuum • Weak GRL flares? Vilmer et al (1999) BATSE PHEBUS

13. Bremsstrahlung and Synchrotron Emitting Electrons (III): Electron « broken » energy spectra • Many evidence from HXR/GR observations that hardening of electron spectra above a few hundred keV (i.e. electron dominated disk event but also GRL events) • Evolution of the break energy in the course of the event • Relation between mm/cm emitting electrons and electrons above Eb PHEBUS& Bern Trottet et al (1998)

14. Trottet, Vilmer et al. 1998 Bern and PHEBUS/GRANAT observations

15. Trottet, Vilmer et al. 1998 •  = radio spectral index • Peak c - from HXR/GR  = 4.1 for E<Eb  = 1.5 for E>Eb • observed •  = 1.5 Peak d - from HXR/GR  = 2.7 for E<Eb  = 1.2 for E>Eb • observed  = 1.3

16. Bremsstrahlung and Synchrotron Emitting Electrons (IV): Production of submm emissions by ultrarelativistic electrons? First detection at 212 GHz Now also at 405 GHZ (Kaufman et al, 2002,2004) Gyrosynchrotron emission From power law energy distribution with = 2.7 Corresponding to a mid size electron-dominated event above > 100 kev (no observations) From Trottet, Raulin, Kaufman et al, 2002

17. Bremsstrahlung and Synchrotron Emitting Electrons (V): Production of submm emissions by ultrarelativistic electrons? II Rise? spectre III Radio emitting electron spectra harder than the X-ray observed one Consistent with = 2.3 in II and = 3.5 in III and B=500G But electrons of energies around 10 MeV needed Breaks? (from Lüthi et al, 2004) To be further investigated with flares also observed above a few MeV

18. 3 November 2003 event <α> = -1.2 (centimétrique)  δ = -2.7 (électrons) From Dauphin et al, 2005 =1.22-0.9 (Dulk et March, 1982) Analyse spectrale X/centimétrique 09:49:10-09:50:00 09:58:10-09:58:40 09:57:40-09:58:00 09:58:40-09:59:50 09:57:00-09:57:30 <α>2eme phase= -1.2

19. Hypothèse: électrons rayonnent dans les X en cible épaisse (Brown, 1971) + propagation libre entre sources X et centimétrique: γ=δ+1(photons)= -1.7 Analyse spectrale de RHESSI  Indice spectral des photons = -1.6 Rear detectors (2 and 7 excluded) no pulse pile up correction  Binning code 12  1 keV 3 to 60 keV 2 keV to 120 keV 5 keV to 250 keV 10 keV to 2250 keV 50 keV 2250 keV to 7200 keV 200 keV 7.2 MeV to 17 MeV + special binning around 511 keV and 2.2 MeV line 2003/11/03 09:58:49.999 2003/11/03 10:01:29.999 4.00969 3.26291 581.398 1.61146 1.4129 0 Flux total observé Flux du bruit de fond raie du bruit de fond Population d’électrons énergétique émettant le rayonnement X > 500 keV compatible avec le rayonnement centimétrique Fit reproduisant le mieux le flux total – le flux du bruit de fond -1.6

20. November 4, 2003 flare spectra SST OVSA Itapetinga A new component Starting from 200 GHz? In relationship with High frequency radiations Kaufmann et al, 2004)

21. Observations Of high energy radiation By SONG/CORONAS Myagkova et al, 2004

22. 2003 October 28 Also for the 28 October flare See Trottet et al Koronas Trottet et al. 2005 in prep.