Particle acceleration associated with magnetic reconnection ?

1
High-energy particles at and from the Sun
2
High-energy particles at and from the Sun

• During the largest solar events
• measurements by particle detectors
• e -gt 100 MeV (Moses et al 1989), maybe higher
• p -gt several GeV (neutron monitors on ground)
• EM emissions / interacting particles
• Gamma-rays from e h? -gt 100 MeV, Egt100 MeV
• Gamma-rays from pion decay pgt 300 MeV
• Time scales of flares fraction of s to tens of
  s, evidence that acceleration time scales are
  that short !

Vilmer et al 1999 AA
Count rate s-1
Vilmer et al 2003 AA 412, 865
Photon energy MeV
3
Particle acceleration in solar flares
4
Particle acceleration associated with magnetic
reconnection ? A simple flare.

• HXR from the low atmosphere (chromosphere) - e
  precipitated downward to ne gt 1012 cm-3,
  bremsstrahlung with ambient p, h?ltenergy(e)
• Radio emission (type III) from outward
  propagating e beams, ?2?pe??ne, start lt 400 MHz
  ne lt 109 cm-3, energy some keV
• ? Acceleration region in the corona, injects
  particles downward (chromosphere) upward (high
  corona, IP space)

Vilmer et al. 2002 Solar Phys
5
Particle acceleration associated with magnetic
reconnection ? A simple scenario.
Vilmer et al. 2002 Solar Phys

• 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 ?

6
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

Trottet et al. 2000 AA 356, 1067
7
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)

Map of linear polari-sation (colour) on top of H?
intensity and mag field (contours)
Hénoux Karlicky 2003  Karlicky Hénoux
2002  Xu et al. 2005 ApJ 631, 618
8
Coronal mass ejections (CMEs), flares, and the
origin of large solar energetic particle events
in space
9
High-energy particles at and from the Sun
gamma-ray analysis of a large flare

• INTEGRAL/SPI measurements of ?R line
  continuum emission
• evolving CONT/line ratio gt e ions accelerated
  together, but proportions vary during event
• Evolving 12C/16O line ratio diff. target
  abundances at diff. times
• gt flare may comprise time-extended (min - tens
  of min - hours) particle acceleration in
  different regions.

h?gt150 keV (e bremsstr.)
h?gt500 keV (e bremsstr.)
h?(7-15) MeV (e bremsstr.)
h?4.4 6.1 MeV (12C, 16O)
h?2.2 MeV (np-gt 2H)
Time s
Kiener et al. 2006 AA 445, 725
10
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. 2007 ApJ 655, 591
Site(s) for SEP acceleration in the magnetically
stressed post-CME corona ?
11
Do fast CMEs produce SEP in the absence of
 flares  ?

• Attempt to isolate pure CME-shock-events
• Fast (?gt700 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 1996-98).
• SEP from the CME shock ?

Marqué et al. 2006 ApJ 642, 1222
12
Do fast CMEs produce SEP in the absence of
 flares  ?

• Attempt to isolate pure CME-shock-events
• Fast (?gt700 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 1996-98).
• 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 !

Marqué et al. 2006 ApJ 642, 1222
13
Energetic particles in the corona and IP space
during a large SEP event
Maia et al 2007 ApJ 660, 874 large SEP event of
2001 April 15

• 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 ?)

14
Energetic particles in the corona and IP space
during a large SEP event
ACE e (178-290) keV
Maia et al 2007 ApJ 660, 874

• 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).

15
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.