Sophie Musset , Eduard Kontar , Nicole Vilmer - · PDF fileSophie Musset1, Eduard Kontar2,...

Click here to load reader

  • date post

    15-Aug-2018
  • Category

    Documents

  • view

    220
  • download

    0

Embed Size (px)

Transcript of Sophie Musset , Eduard Kontar , Nicole Vilmer - · PDF fileSophie Musset1, Eduard Kontar2,...

  • Sophie Musset1, Eduard Kontar2, Nicole Vilmer1

    15th RHESSI Workshop, 26-30 July 2016, Graz

    1 LESIA, Observatoire de Paris 2 School of Physics and Astronomy, University of Glasgow

  • 1. RHESSI Imaging Spectroscopy: a new tool to study electron

    transport during solar flares

    2. The 2004 May 21 solar flare

    3. The diffusive transport model (Kontar et al, 2014)

    4. Comparison between observations and model predictions

    5. Conclusions

    1

  • Battaglia & Benz (2006)

    2

  • Battaglia & Benz (2006)

    Photon spectral index

    2

    Need additional

    mechanism to

    collisional transport

    2

  • Battaglia & Benz (2006)

    Simoes & Kontar (2013)

    Photon spectral index

    2

    Need additional

    mechanism to

    collisional transport

    2

  • Battaglia & Benz (2006)

    Simoes & Kontar (2013)

    Photon spectral index

    2

    Electron spectral index

    < 0 Ratio of electron rate

    > 1

    Need additional

    mechanism to

    collisional transport

    2

    Need additional

    mechanism to

    collisional transport

  • Radio observations : Kuznetsov & Kontar (2015)

    3

  • Radio observations : Kuznetsov & Kontar (2015)

    Spatial distribution of the density of

    energetic electrons with E > 60 keV

    = 2.1

    3

  • X-ray imaging spectroscopy

    Musset et al, in prep

    12-25 keV

    25-50 keV

    50-100 keV

    4

    Thick target

    Thin target Thick target

  • X-ray imaging spectroscopy

    Musset et al, in prep

    5

  • X-ray imaging spectroscopy

    Musset et al, in prep

    = 4.2 0.2

    = 0.12 0.03 1035 s1

    = 4.4 0.2

    = 5.2 0.4

    = 0.06 0.02 1035 s1

    12-25 keV

    25-50 keV

    50-100 keV

    6

    Thick target

    Electron spectral index: Electron rate above 25 keV:

    Thin target

    Electron spectral

    index: Integrated electron

    mean flux spectrum

    above 0=25 keV

    0 =

    0

    0 = 0.46 0.08 1055

    21

  • X-ray imaging spectroscopy

    Musset et al, in prep

    = 4.2 0.2

    = 0.12 0.03 1035 s1

    = 4.4 0.2

    = 5.2 0.4

    = 0.06 0.02 1035 s1

    12-25 keV

    25-50 keV

    50-100 keV

    6

    Thick target

    Electron spectral index: Electron rate above 25 keV:

    Thin target

    Electron spectral

    index: Integrated electron

    mean flux spectrum

    above 0=25 keV

    0 =

    0

    0 = 0.46 0.08 1055

    21

    Distance between the footpoints and the looptop source: ~17 and ~15 108 cm Length of the loop ~ 3.2 109 cm

  • X-ray imaging spectroscopy

    Musset et al, in prep

    7

    = = ()

    0

    0

    =

  • X-ray imaging spectroscopy

    Musset et al, in prep

    7

    = = ()

    0

    0

    =

    = 9.6 108

    = 1.5 1026 3

    = = 1.2 0.2 1011 3

    = 0.4 0.2 1035 s1

    = 2.2

  • Spatial distribution of electrons

    at 25 keV

    Electron mean spectra

    in the different parts of the loop

    Looptop source

    Footpoints

    8

  • =

    ()

    ()

    Energetic electron density above Emin cm-3

    Energetic electron density

    above 25 keV

    9

  • =

    ()

    ()

    Energetic electron density above Emin cm-3

    Energetic electron density

    above 25 keV

    Energetic electron density

    above 60 keV

    From radio (Kuznetsov

    & Kontar 2015)

    From

    X-rays

    9

  • Energetic electron density above Emin cm-3

    = ()

    ()

    Energetic electron density

    above 25 keV

    Energetic electron density

    above 60 keV

    From radio (Kuznetsov

    & Kontar 2015)

    From

    X-rays

    Distribution deduced from gyrosynchrotron emission is more peaked than

    the distribution deduced from X-rays

    ,25

    ,25 ~1.6 3.8

    ,60

    ,60 ~7.7 9

    9

  • 1

    ()

    =

    + 0()

    Diffusion Collisions Source

    Kontar et al (2014)

    ()

    =

    3 : mean free path

    Strong pitch angle scattering due to small scale magnetic fluctuations

    diffusive transport of energetic electrons

    10

  • 1

    ()

    =

    + 0()

    Diffusion Collisions Source

    Kontar et al (2014)

    , =

    0

    0

    4 2 2 + 22exp

    2

    4 2 2 + 22

    ()

    =

    3 : mean free path

    Suppose constant

    10

    2

  • 1

    ()

    =

    + 0()

    Diffusion Collisions Source

    Kontar et al (2014)

    , =

    4 2 2 + 22exp

    2

    4 2 2 + 22

    ()

    =

    3 : mean free path

    density of the medium size of the acceleration region /0 injected electron spectrum

    Acceleration region

    Suppose constant

    10

  • 1

    ()

    =

    + 0()

    Diffusion Collisions Source

    Kontar et al (2014)

    , =

    4 2 2 + 22exp

    2

    4 2 2 + 22

    ()

    =

    3 : mean free path

    Spatial distribution of electrons at 20 keV

    collisional

    = 109cm

    = 108cm

    = 107cm

    10

  • 1

    ()

    =

    + 0()

    Diffusion Collisions Source

    Kontar et al (2014)

    , =

    4 2 2 + 22exp

    2

    4 2 2 + 22

    ()

    =

    3 : mean free path

    Spatial distribution of electrons at 20 keV Looptop and footpoint spectra

    collisional

    = 109cm

    = 108cm

    = 107cm

    = 109cm

    = 108cm

    = 107cm

    looptop

    footpoint

  • Mean free path Size of acceleration region ~ 3.2 109 cm Length of the loop

    Spatial distribution at 25 keV Coronal and footpoint spectra

    = 1.2 0.2 1011 3; = 109 ; = 3 108

    = 3 1010 3; = 3 108 ; = 3 108

    11

  • Spatial distribution of energetic electron density

    with energy > 25 keV

    = 1.2 0.2 1011 3 ; = 3 108

    = 3 1010 3 ; = 3 108

    = 109 = 3 108

    12

  • Spatial distribution of energetic electron density

    with energy > 25 keV

    = 1.2 0.2 1011 3 ; = 3 108

    = 3 1010 3 ; = 3 108

    = 109 = 3 108

    12

    The diffusive transport model

    (Kontar et al. 2014) is

    consistent with the X-ray

    observations (spectral and

    spatial distribution).

    What about the radio

    observations of Kuznetsov and

    Kontar (2015) ?

  • Spatial distribution of energetic electron density

    with energy > 25 keV with energy > 60 keV

    = 1.2 0.2 1011 3 ; = 3 108

    = 3 1010 3 ; = 3 108

    = 109 = 3 108

    = 6 107 = 2 107

    7

    The distribution is more

    peaked: need a smaller

  • Trapping can be caused by magnetic

    field convergence.

    The trapped fraction of particles is

    And in the case of isotropic pitch-

    angle distribution,

    Where 0 is the loss cone angle

    With = the magnetic ratio. (Simoes & Kontar 2013)

    = 1

    = cos (0)

    0 = sin1 ( 1/)

    13

  • Trapping can be caused by magnetic

    field convergence.

    The trapped fraction of particles is

    And in the case of isotropic pitch-

    angle distribution,

    Where 0 is the loss cone angle

    With = the magnetic ratio. (Simoes & Kontar 2013)

    = 1

    = cos (0)

    0 = sin1 ( 1/)

    = . = .

    13

  • Magnetic field strength along the

    loop (Kuznetsov & Kontar 2015)

    Trapping can be caused by magnetic

    field convergence.

    The trapped fraction of particles is

    And in the case of isotropic pitch-

    angle distribution,

    Where 0 is the loss cone angle

    With = the magnetic ratio. (Simoes & Kontar 2013)

    = 1

    = cos (0)

    0 = sin1 ( 1/)

    = . = .

    . < < .

    13

  • Magnetic field strength along the

    loop (Kuznetsov & Kontar 2015)

    Trapping can be caused by magnetic

    field convergence.

    The trapped fraction of particles is

    And in the case of isotropic pitch-

    angle distribution,

    Where 0 is the loss cone angle

    With = the magnetic ratio. (Simoes & Kontar 2013)

    = 1

    = cos (0)

    0 = sin1 ( 1/)

    = . = .

    . < < .

    But how to explain the spectral

    hardening in the footpoints?

  • Imaging spectroscopy is used to study the spatial distribution of electrons and

    the comparison of spectral distribution in different parts of the loop

    Diffusive transport model (Kontar et al 2014) can explain the X-ray observations

    Diffusive transport model can also explain the gyrosynchrotron observations,

    but with a smaller mean free path

    Mean free path is energy dependant

    First comparison between radio and X-ray observations to probe energetic

    electrons tra