High-energy particles at and from the Sun – electromagnetic signatures related to SEPs
Karl-Ludwig Klein [email protected],
(F-92195 Meudon)
Univ P&M Curie, Paris Diderot
Collaborators in Meudon: S. Masson (now GSFC), R. Miteva, G. Trottet High-energy particles at and from the Sun Outline
• In situ measurements vs radiative signatures; scenarios of acceleration, overview over EM emission processes
• FERMI observations of solar flares
• SEP events and coronal activity – associations – statistical studies
• Transport modelling of energetic particles compared with radio observations Energetic particles at and from the Sun
In situ measurements vs radiative signatures; scenarios of acceleration High-energy particles at and from the Sun Scenarios of particle acceleration
• “Flare acceleration”: particles • Radiative signatures of accelerated accelerated in complex particles in the solar atmosphere: magnetic configurations in the • HXR: bremsstrahlung by e- (dense corona (particles radiating γR, ambient medium -> chromosphere) HXR, radio; particles escaping • γR: idem + lines (1-7 MeV) from the along open flux tubes towards impact of accelerated nucleons onto IP space). the ambient atmosphere (dense ambient medium -> chromosphere) • Microwaves (mm-cm-λ, sometimes m-λ) through gyro-synchrotron emission of electrons (>100 keV) • dm-m-λ radio through collective
processes at ν=νpe or 2νpe. • Extension to decam-km-λ when electrons in IP space
after K.-L. Klein., Sol Orbiter Workshop, Athens, ESA-SP Nuclear lines
e- bremsstrahlung Pion decay photons
• HXR-gamma-ray spectrum of a solar flare (Phebus/ GRANAT, court. G. Trottet, N. Vilmer) Solar radio and HXR bursts Particle acceleration region
• A set of complementary observations of EM emissions from flare-accelerated Vilmer electrons : et al. 2002
– Hard X-rays (hν > 20 keV): energy spectra and imaging Solar
– Radio emission : spectra and imaging from ground (400 GHz > 5 min Phys
ν > 20 MHz) 210, 261
– Radio emission : spectra from space (ν < 14 MHz) Solar radio and HXR bursts Particle acceleration region
Vilmer et al. 2002 Solar Phys
Particle acceleration region in a reconnecting coronal current sheet. Electric fields : - reconnection inflow - turbulence - termination shock (outflow/ambient plasma) Solar radio bursts Classification (dm-m-waves
Type III (e beams) Wind/WAVES • At dm-m-λ radio waves:
715, 468 – Electron beams rising from the low ApJ corona to IP space (type III; r ≈ 1.1 R¤ Type II -1 AU) 2010 (shock wave) – Shock waves in the corona and IP Nançay DA space
Haggerty
Type IV– Confined electron populations as (trapped e) tracers of CMEs (type IV)
ARTEMI , Hoang, Wang, , Hoang, Wang, S Pick
, Nançay RH Kerdraon
Solar Radio Monitoring at Nançay 8 Solar radio bursts Classification (dm-m-waves
Type III (e beams) Wind/WAVES • At ≥ dm-λ waves: emission at ν~νpe~√ne 715, 468
ApJ – Propagating exciter in a quasi-static Type II atmosphere or expanding loops (CME): 2010 (shock wave) shock
Nançay DA Haggerty e beam trapped e Type IV (trapped e)
ARTEMI
, Hoang, Wang, , Hoang, Wang, S – Characteristic shapes of the radio burst spectra:
Pick III II , Nançay RH [MHz]
Kerdraon IV Frequency Solar Radio Monitoring at Nançay 9 Time (altitude) Solar radio bursts Classification (dm-m-waves)
Type III (e beams) Wind/WAVES • 2007 May 19: SEP event (STEREO) • Why does this poorly connected solar 715, 468 activity (EUV: W05°) emit SEPs ApJ detected at Earth (Parker spiral Type II W38°) ? 2010 (shock wave)
Nançay DA • Radio imaging (NRH): because the
Haggerty energetic electrons (particles in general ?) are released well westward of the parent AR (shock and open flux Flaringtube AR geometry) ! Type II ARTEMI
, Hoang, Wang, , Hoang, Wang, S Pick
, Nançay RH Kerdraon
Type III STEREO + NRH 10 High-energy particles at and from the Sun Interacting vs escaping particles
• Extreme particle energies inferred from γR and measured in escaping SEP are comparable: – tens of MeV for e- – hundreds to thousands of MeV for p
• Estimated numbers vary widely, but ratio N(Interacting) / N(escaping) – may be <1 or >1 for protons > 30 MeV (Ramaty et al. 1993 ASR 13(9), 275) – Is always >>1 for e- > 50 keV (Ramaty et al. 1993; Krucker et al. 2007 ApJ663, L109)
• ⇒ Electrons mostly confined in the corona, interacting and escaping protons have accelerators of comparable efficiency (on average) High-energy particles at and from the Sun Interacting vs escaping particles
E>200 keV: E>50 keV: Dröge 1996, Krucker et al. AIP Conf Proc 2007 ApJ663, L109 374, 78; cf. also Ramaty et al. 1993 ASR 13(9), 275
• HXR (bremsstrahlung) emission + in situ observations: – determination of the spectral index and number of electrons. – problem: volume (IP space), interaction model (thick/thin target) • Comparison:
– Ne(escaping) << Ne(Interacting) – Correlation between spectral indices, in between pred. of thin & thick target • Close connection between acceleration processes (provided e- can escape from the flare site: `prompt’ events - see Krucker et al.) Solar energetic particles (SEPs) in IP space Interacting vs escaping electrons
• Illustration of confined electrons accelerated during a flare, escaping electrons from higher coronal sources
GOES • Possible hint: - flare-accelerated electrons (particles) RSTN 245 RSTN 610 RSTN 15400 confined – no type III burst with microwave burst 60 - Alternative accelerators: 50 40 - Shock wave (type II) with type III burst 30 Frequency [MHz] Green Bank 20 - Post-eruptive reconnection (type IV) with
WAVES type III burst 10 - Small SEP event (SoHO/ERNE, ACE/ 6 EPAM) Frequency [MHz] 2 1.0 • But flare-accelerated electrons (particles)
0.6 are not always confined (definite evidence
0.2 only in a minority of events – Miteva et al., WAVES 17:20 17:40 18:00 18:20 work in progress) Universal time on 2004 August 18 Solar energetic particles (SEPs) in IP space Interacting vs escaping electrons
• Evidence for combined contribution by both flare-related reconnection (if magnetic connection to s/c) and CME-related acceleration higher in the corona (shock, post-eruptive magnetic reconnection ?)
0.01 0.01
0.10 0.10
1.00 1.00 Frequency [MHz] Frequency [MHz] 10.00 10.00
1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 flux density flux density Normalised Normalised 0.2 0.2 0.0 10-3 10-5 -4 ] 10 ] -2 -2 10-6 10-5 10-7 -6 Flux [W m 10 Flux [W m 10-8 10-7 20:30 20:50 21:10 21:30 02:00 02:20 02:40 03:00 Universal time [hours] on 2003 Oct 29 (DOY 302) Universal time [hours] on 2000 Mar 3 (DOY 63) High-energy particles at and from the Sun Scenarios of particle acceleration
• Particle acceleration related to CMEs: Radio (II) – Magnetic reconnection related Shock to “post flare loop” formation) Radio – Turbulence in the post-eruptive B//=0 (IV) corona SXR, – Shock wave driven by the EUV outward motion of the CME HXR, – Shock wave driven by the γR … lateral expansion of the CME B//=0 (possible signature: EIT wave)
Pomoell et al. 2008 Solar Phys 253, 249 FERMI observations of solar flares FERMI observations of solar flares An impulsive event Ackermann et al. 2012 et al. 2012 Ackermann 144 ApJ 745, 100-300 π decay model keV
Pulse hν>100 keV pile-up
bremsstrahlung model
• FERMI HXR/gamma ray, M2 2010 Jun 12 • Gamma-ray emission up to 400 MeV: bremsstrahlung e≥400 MeV or pion decay radiation p>300 MeV ? • Relativistic electrons (bremsstrahlung), deka-MeV protons (nuclear lines) in a moderate flare: – Acceleraton to >100 MeV within a few seconds – Complex acceleration time history: HE delay of a few s FERMI observations of solar flares Overview first four years
• FERMI (GBM, LAT) observations of solar flares: 19 detected at hν > 100 MeV 06/2010 - 07/2012 (Ackermann et al. 2013 ApJ, subm.) • With strong and moderate (>M2, but one C!) SXR © FERMI web site bursts • Photon energy spectrum: power law with HE rollover or π0-decay photons (from p>300 MeV impacting the chromosphere) – Most likely: hadronic origin – Alternative: e- bremsstrahlung (less consistent with observed spectral evolution in long duration events, expected IC scattered photon in HXR not seen…) FERMI observations of solar flares Long duration events
• In some events observation of impulsive phase emission – Difficult, since Sun in Fermi FoV only ~20% of time (survey mode) – 3 events where Sun was in FERMI FoV had NO impulsive emission > 100 MeV, but a subsequent phase of long-duration emission Ajello et al. 2013 et al. 2013 Ajello ApJ , submitted
20 hrs FERMI observations of solar flares Long duration events
• Frequent occurrence of long duration events (> 1 hr, up to 20 hr) – Monotonically decaying tail (earlier Compton & GAMMA1 observations; e.g., Kanbach et al. 1993 AAS 97, 349) ; (main) source in the flaring AR – Tentative interpretation: time-extended acceleration of protons > 300 MeV in/near the flaring AR Ajello et al. 2013 et al. 2013 Ajello ApJ , submitted
FERMI + SDO 20 hrs FERMI observations of solar flares Long duration events
• Frequent occurrence of long duration events (> 1 hr) – Monotonically decaying tail (earlier Compton & GAMMA1 observations; Kanbach et al. 1993 AAS 97, 349) ; (main) source in the flaring AR – Tentative interpretation: time-extended acceleration of protons > 300 MeV in/near the flaring AR
• How are these time scales related with a flare ? – known from continuous formation of « post flare » loops – related to magnetic reconnection and/ or turbulence in the post-CME corona – proposed earlier for time-extended proton acceleration (Litvinenko & Somov 1995 Sol Phys 158, 317; Akhimov et al. 1996 Sol Phys 166, 107; Klein et al. 1999 AA 348, 271; Ryan 2000 SSR) FERMI long duration events Relationship with SEPs ?
Calibration mark • Several FERMI 0.01 events had SEP 0.10 Ajello counterpart observed 1.00 by PAMELA et al. 2013 Frequency [MHz]
10.00
1.0 • 2012 Mar 07 case: 0.8 0.6 • Type III bursts and ApJ 0.4 flux density Normalised 0.2 microwave emission ,
during the impulsive 0.0 submitted
phases of the two 10-4 ] flares -2 10-5 10-6
• No microwave or Flux [W m 10-7 type III burst during 10-8 00 02 04 06 08 10 the long > 100 MeV Mar 07 Universal time [hours] starting 2012 Mar 6 (DOY 66) decay phase • Absence of type III due to smooth particle acceleration ? Transport modelling of energetic particles compared with radio emission High-energy particles from the Sun Electron injection functions from IP transport modelling
• A more sophisticated approach than a simple timing comparison: derive the injection function of SEPs from the observation and compare with radiative signatures
• Agueda et al. (2008 ApJ 675, 1601; 2009 A&A 507, 981): – observation of electron intensity and anisotropy + focussed IP tranport – Fit using a series of impulsive electron releases – Consistent results using ACE/EPAM and Wind/3DP observations of the same event
• Agueda et al. (2014 A&A., submitted): analysis of 7 NR electron events observed in the solar wind High-energy particles from the Sun Electron injection functions from IP transport modelling
• Group 1 (4 events): – Short release episode of NR electrons (< 60 min), consistent with timing of DH III – Impulsive SXR (rise time < 20 min) – CMEs, speeds 700-1000 km/s, 2/4 events with DH type II • Group 2 (3 events): – Time-extended release of NR electrons (> 2 h), starting with (1/3) or after (2/3) the DH type III hursts – Time-extended SXR (rise time > 25 min, long decay phase) – CMEs, speeds > 1300 km/ s, 3/3 events with bright DH type II, but also type IV or long-lasting microwave emission Agueda et al. 2014 Astron. Astrophys., submitted High-energy particles from the Sun Electron injection function from IP transport modelling
• SoHO/LASCO : fast CME Maia, Gama, Mercier, Pick, Kerdraon, Karlicky • Nançay RH : gyro-synchrotron 2007 ApJ 660, 874 emission from relativistic electrons (behind CME front when bwd extrapolated; acceleration in the perturbed corona).
Inj. time profile
Radio time profile ACE/EPAM • derived e- injection function ≈ obs. time history of radio emission • Particle acc. in the magnetically ⇐ • + transport modelling (adiabatic stressed corona in the aftermath of focussing + PA scattering) a CME. High-energy particles from the Sun Relativistic proton injection function from IP transport modelling
• Isotropic diffusive transport model of the SEP event 1991 Jun 15 (Akimov et al. 1996 SP 166, 107) – Injection function = microwave time profile – Authors claim that a better fit is obtained when only the post-impulsive microwave emission is used (bottom row)
• + transport modelling (adiabatic focussing + PA scattering) Masson et al. 2009 Sol Phys 257, 305
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the Sun Sun the IP travel IP AU 1.4-1.5 Relativistic p, Relativisticp, events from
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• • • • High-energy particles from the Sun 20 Jan 2005: relativistic protons at the Sun and at 1 AU
• 2nd peak of the relativistic p profile SP et al. 2009 Masson thesis 2010 Masson 305; 257, – not related with conspicuous HXR/µ wave emission – at the time of a new m-Dm-λ type III, a drifting m-λ burst (type II = shock wave?), and broadband gyro- synchrotron emission.
• Drifting radio burst : r < 2 R0 (well below CME front) – If shock acceleration: not near the CME front – Closer examination of the radio burst: type IV (acceleration in the corona behind a CME – reconnection, turbulence in large- scale coronal structures) High-energy particles from the Sun Injection of electrons and protons observed by HELIOS
• The interpretation of time profiles of SEP intensities observed from 1 AU remains ambiguous due to a variety of coronal and IP transport effects: - Multiple acceleration sites activated nearly simultaneously - Pitch angle scattering - IMF structure (including ICMEs) • Evidence of a close connection between SEP release and HXR/radio emission from HELIOS observations at r=0.38 AU (Kallenrode & Wibberenz 1991): - Impulsive release of NR electrons with microwave and DH type III burst - Delayed release of deka-MeV protons with new HXR/microwave/DH type III burst - Variable e/p ratio closely related with coronal acceleration history Kallenrode & Wibberenz 1991 ApJ 376, 787 High-energy particles at and from the Sun Summary
• FERMI observations of solar flares: – impulsive phase and long duration emission > 100 MeV likely from pion decay – Time-extended particle acceleration in the flaring AR – No microwave counterpart (2012 Mar 07) = no signature of accompanying electron acceleration ?
• SEP events and coronal activity – No hint toward a privileged association with either flare parameters or CME speed – Evidence for a variety of situations with or without a flare contribution (depending on coronal propagation vs. confinement, magnetic connection to the observer …) – Limited power of statistical studies because of the mixing of different transport conditions in different events ?
• Transport modelling of energetic particles compared with radio observations – Close timing relationships of NR electrons and protons with radio emissions in the impulsive and/or post-impulsive phase – Ambiguous coronal counterparts to time-extended acceleration, but evidence that CME contributes not only through shock acceleration – especially at high energies. – New insight from SEP time profile analysis using observations close to the Sun.