Energy Release and Particle Acceleration in Solar Flares

Nicole Vilmer

LESIA-Observatoire de Paris

VII COLAGE-Atibaia 01/04/04

Magnetic energy release in the solar corona:CME’s (see previous talks)

But ALSO EFFICIENT PARTICLE ACCELERATION

Flare Accelerated Particles

Particle acceleration (Where, How Fast? How Many? Which Ones?)

Injection in the interplanetary medium (Where? When? Relation with flare particles?)

Hard X-ray/-ray continuum (HXR/GR): ~ 10 keV-~100 Mev (up to GeV) electrons (acceleration time scales, energy spectra, number)-ray line radiation (GRL) : a few MeV/nuc-a few GeV/nuc ions (acceleration time scales, energy spectra, abundances…)High energy (~75 MeV) -ray continuum and neutrons: > 100 MeV/nuc ions (acceleration time scales, energy spectra, numbers)

Observations of several thousands of X-ray flares 30 GRL flares on 3 solar activity cycles Main scientific goal of RHESSI

Direct diagnostics of accelerated particles interacting in the solar atmosphere

RHESSI observations

SXR emissionHot plasma (a few MK )

HXR emissionBremsstrahlung from non Thermal electrons

Prompt -ray lines:Deexcitation lines from C and 0(60%) due to interactions from > Mev Protons and alphas

Neutron capture line:p on heavy ions produce neutronsNeutrons are slowed down and captured by ambient hydrogen deuterium + 2.2 MeV.

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

Energetic Ions -ray line spectroscopy ions in the 1MeV/nuc-100 MeV/nuc range

narrow deexcitation -ray line fluences ion energy spectrum

and target abundances(i.e. solar atmosphere) Broad -ray lines

abundances of accelerated ions

2.2 MeV deuterium line:capture line after thermalizationfrom neutrons from nuclear reactions

(Share & Murphy,2000)

Decimetric/metric emissionsNon thermal electrons Propagating in the coronaPlasma emissions

Cm/mm radio emissionsGyrosynchrotron emissions from>100 keV-1 MeV electronsIn the corona

HXR emissionsBremsstrahlung radiation from>10 keV- 10 MeV electronsin the chromosphere

Particle acceleration associated with solar flares in active regions

Electrons from 10 keV to GeV10 33 -10 39 électrons > 25 keV10 28 -10 34 ergs > 25 keV

Ions from 10 MeV to GeV10 30 -10 34 > 30 MeV 10 30 - 10 32 ergs > 1 MeV

From many flares observed by SMMYOHKOH-GRANAT-CGRO (withlimited spectral resolution)

1028 to 10 34 ergs released timescales from a second to tens of minutes

Principal Investigator:   Robert Lin UCB

Project Manager:   Peter Harvey UCB

 Lead System Engineer:   David CurtisUCB

Lead Co-Investigator:   Brian Dennis GSFC 

Co-Investigators:   Arnold Benz ETHZPatricia Bornmann NOAAJohn Brown U. of GlasgowRichard Canfield Montana State U.Carol CrannellGSFCGordon EmslieU. Alabama Huntsville Shinzo EnomeGordon HolmanGSFC, Code 682Hugh Hudson UCB Gordon HurfordGSFC,Code 682Takeo KosugiNAOJNorman Madden LBNLReuven RamatyGSFC, Code 661Frank van BeekDelft U.Nicole VilmerParis ObservatoryTycho von RosenvingeGSFC, Code 66Alex ZehnderPSI

         

RHESSI Characteristics Imaging

Angular resolution

Field of View

Spectroscopy Energy range Energy resolution

Fourier-transform imaging with 9 bi-grid rotating modulation collimators

2.3 to 36 depending on energy HXR 2.3 ; GRL /GR 36

Full Sun Tens of ms for basic image (near future) 2s for detailed image

3 keV to 10 MeV < 1 keV 5 keV@ 20 MeV

First RHESSI observations of a solar -ray line flare : images and spectra at high resolution (23/07/02 event)Electron & Ion interaction sites: First images at gamma-ray energiesElectron & Ion production time profiles: effects of transport in the solar atmosphere? Some preliminary observations of the gamma-ray flares in October/November 2003

Relationship between cm/mm emitting electrons and HXR/gamma-ray ones: towards higher frequencies: Evidence of flat energetic electron components above 1 MeV

23/07/2002 X4.8 GOES: RHESSI -ray line flare

Lin et al, 2003 (ApJ, October 2003)

Images:64’’ wideAt the time of flare maximum

Early phase: evidence of production of non Thermal electrons in the corona

From Lin et al, 2003

12-30 keV contours with TRACE 195 A

Thermal + steep double Law components : 5-6.5

E>20 keV > 2 10 31 ergs in this phaseMostly released in the corona(compared to total energy :10 31 ergs above 30 KeV

First impulsive peak

40 MK +2 power laws 2.5-3.5

Lin et al, 2003, Krucker et al, 2003

Second impulsive peak

Apparent movement of northern footpoint andCoronal source // ribbon ( 50 km/s) No systematic motion of southern footpointReconnection in highly sheared region?

Halpha-HXR movie

Courtesy S. Krucker)

Spectral evolution movie

Holman et al

2003

X4.8 flare : 23/07/2002 Imaging spectroscopy with RHESSI

Emslie et al, 2003

N

M x0.1

Sx0.01

Photon spectrum

Lin et al, 2003

2.2 MeV line

Nuclear Prompt lines

Electron bremsstrahlung

Electron & Ion Production Time Profiles

Spectral analysis 6 narrow linesBroken electron power lawBroad nuclear line component511 keV and 2.2 MeV lines

Share et al, 2003

Radiation from electrons

Radiation from ions(delay of ~ 10s: transportEffects)

E>2.5 MeV10 31 ergs

Smith et al, 2003

Redshift (0.1-0.8 %)larger than expectedfor a limb flareif Downward isotropic distributionif Radial B field!

SMM 5 flaresSame longitude

Broadening 0.1-2.1% FWHM

No redshift (light curve) Redshift (Heavy curve)

First gamma-ray images of a flare!

Gamma-ray line image displaced from20 ’’ from electron emission site!!! Interpretation? Hurford et al, 2003

+ TRACE post flare loop

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): 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)

Bremsstrahlung and Synchrotron Emitting Electrons (II):

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)

The Sun is an efficient particle accelerator

First observations of a solar -ray line flare with high spectral and spatial resolutions:

HXR imaging spectroscopy: variations of photon (electron) spectra from one HXR source to the other (e- transport in loops…)

HXR images: spatial distribution and movements of footpoint sources consistent with magnetic reconnection scenarios?

HXR spectroscopy: precise determination of the electron spectrum from photon spectrum at high resolution

GRL spectroscopy : measurements of redshifts emissions by ions in tilted B fields

GRL images: unexpected displacement between electron and ion interaction sites (acceleration? propagation and injection in B

fields?

Other -ray line observations in October/November ???

The Sun: an efficient particle accelerator

Bremsstrahlung and synchrotron emitting electronsRelationship between cm/mm and a few MeV electronsis it still true for ultrarelativistic electrons and for the production of submillimeter emissions??

Gamma-ray observations from 1 to 10 MeV (even > 10 MeV) with observations >100 GHz needed to conclude…