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

N. Vilmer

LESIA –Observatoire de Paris

Ascona_June 7-11 2005

X/ -ray spectrum

RHESSI Energy range

Pion decay radiation(ions > 100 MeV/nuc)sometimes with neutrons

Ultrarelativistic ElectronBremsstrahlung

Thermal components

Electronbremsstrahlung

-ray lines (ions > 3 MeV/nuc)

T= 2 10 7 KT= 4 10 7 K

SMM/GRSPhebus/GranatObservationsGAMMA1GROGONG

-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

-ray and neutron event on 24/05/90

• 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

From Talon et al., 1993

Debrunner et al 1997 PHEBUS/GRANAT observations

High Energy -rays

Solar neutrons

Spectral evolution of high-energy -rays

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

Background subtracted count spectraFrom PHEBUS/GRANATFull line: one of the best fits with electron and pion contributionsDotted line: electron contribution

Background subtracted count spectrumFrom 300 keV to 100 MeVFull line: one of the best fits with one electron bremsstrahlung component& pion contributionDotted line: electron componentElectron bremsstrahlung component:Ae= 1 10 5 = 2 Eroll= 40 MeVProton component:=2 Ntot= 8 1031 Emax= 750 MeV

-ray lines

Vilmer et al, 2003

• 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

• 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)

X/ -ray spectrum

RHESSI Energy range

Pion decay radiation(ions > 100 MeV/nuc)sometimes with neutrons

Ultrarelativistic ElectronBremsstrahlung

Thermal components

Electronbremsstrahlung

-ray lines (ions > 3 MeV/nuc)

T= 2 10 7 KT= 4 10 7 K

Phebus/Granatobservations

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

1.22 0.9r

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?

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 o if Wi>1MeV/nuc We>20 keV

o No detectable GRL above continuum

o Weak GRL flares?

Vilmer et al (1999)

PHEBUS

BATSE

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& BernTrottet et al (1998)

Trottet, Vilmer et al. 1998

Bern and PHEBUS/GRANATobservations

= 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

Trottet, Vilmer et al. 1998

Bremsstrahlung and Synchrotron Emitting Electrons (IV):

Production of submm emissions by ultrarelativistic electrons?

First detection at 212 GHzNow also at 405 GHZ

(Kaufman et al, 2002,2004)

From Trottet, Raulin, Kaufman et al, 2002

Gyrosynchrotron emissionFrom power law energy distribution with = 2.7Corresponding to a mid size electron-dominated

event above > 100 kev(no observations)

Bremsstrahlung and Synchrotron Emitting Electrons (V):

Production of submm emissions by ultrarelativistic electrons?

spectre

Radio emitting electron spectra harder than the X-ray observed oneConsistent with = 2.3 in II and = 3.5 in III and B=500G

But electrons of energies around 10 MeV neededBreaks?

(from Lüthi et al, 2004)To be further investigated with flares also observed above a few MeV

II

III

Rise?

Analyse spectrale X/centimétrique

<<αα> = -1.2 (centimétrique) > = -1.2 (centimétrique) δδ = -2.7 (électrons) = -2.7 (électrons)

=1.22-0.9=1.22-0.9 (Dulk et March, 1982) (Dulk et March, 1982)

09:49:10-09:50:00

09:57:00-09:57:30

09:58:10-09:58:4009:57:40-09:58:0009:58:40-09:59:50

<α>2eme phase = -1.2

3 November 2003 event

From Dauphin et al, 2005

Hypothèse: électrons rayonnent dans les X en cible épaisse (Brown, 1971) Hypothèse: électrons rayonnent dans les X en cible épaisse (Brown, 1971) + propagation libre entre sources X et centimétrique: + propagation libre entre sources X et centimétrique: γγ==δδ+1(photons)= -1.7+1(photons)= -1.7

Flux total observé

Flux du bruit de fond

Fit reproduisant le mieux le flux total – le flux du bruit de fond

-1.6

raie du bruit de fond

Analyse spectrale de RHESSI Analyse spectrale de RHESSI Indice spectral des photons = -1.6Indice spectral des photons = -1.6

Population d’électrons énergétique Population d’électrons énergétique émettant le rayonnement X > 500 émettant le rayonnement X > 500 keV compatible avec le keV compatible avec le rayonnement centimétriquerayonnement centimétrique

Rear detectors (2 and 7 excluded) no pulse pile up correction Binning code 12

 1 keV 3 to 60 keV2 keV to 120 keV5 keV to 250 keV

10 keV to 2250 keV50 keV 2250 keV to 7200 keV200 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 

November 4, 2003 flare spectra

OVSA

Itapetinga

SST

Kaufmann et al, 2004)

A new component Starting from 200 GHz?

In relationship withHigh frequency radiations

U T (hh:m m ) 04/11/2003

0

50

100

150

200 0

5

10

15

200

1

2

150-500 keV

0.5-1.3 MeV

1.3-4 MeV

0.0

0.2

0.4

SO

NG

(C

OR

ON

AS

-F)

X-r

ay

an

d g

am

ma

-ra

y e

mis

sio

n,

ph

oto

ns/

(cm

**2

s

Me

V)

4-7 MeV

0.00

0.01

0.02

7-15 MeV

0.000

0.002

0.004

26-40 MeV

0.000

0.005

0.010

0.015

60-100 MeV

0.000

0.001

0.002

100-200 MeV

19:30 19:36 19:42 19:48 19:54 20:00

Observations Of high energy radiationBy SONG/CORONASMyagkova et al, 2004

2003 October 28

Trottet et al. 2005 in prep.

Koronas

Also for the 28 October flare

See Trottet et al