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High Resolution Imaging and EUV spectroscopy for RHESSI Microflares

High Resolution Imaging and EUV spectroscopy for RHESSI Microflares. S. Berkebile-Stoiser 1 , P. Gömöry 1,2 , J. Rybák 2 , A.M. Veronig 1 , M. Temmer 1 , P. Sütterlin 3.

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High Resolution Imaging and EUV spectroscopy for RHESSI Microflares

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  1. High Resolution Imaging and EUV spectroscopy for RHESSI Microflares S. Berkebile-Stoiser1, P. Gömöry1,2, J. Rybák2, A.M. Veronig1, M. Temmer1, P. Sütterlin3 1 IGAM/Institute forPhysics, University of Graz, Austria2 Astronomical Institute, SlovakAcademyofSciences, Slovakia3Institute for Solar Physics, The Royal Swedish Academy of Sciences, Sweden

  2. Microflare observation campaign 2006 Initiators: Jan Rybàk, Peter Gömory (AI/Slovak Academy of Sciences), Astrid Veronig, Manuela Temmer, Sigrid Stoiser, IGAM/Institute of Physics, Uni Graz Campaign Duration: June 28 – July 12, 2006 Goals:- study of the dynamics and fine structureof microflares - Energy transfer and dynamics of wavesin the chromospheric network Instruments: • Dutch Open Telescope (DOT) • Coronal Diagnostic Spectrometer (SOHO/CDS) • Extreme Violet Imaging Telescope (SOHO/EIT) • Michelson Doppler Interferometer (SOHO/MDI) • Transition Region and Coronal Explorer (TRACE) • Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) • Kanzelhöhe Solar Observatory (KSO),Hvar Observatory

  3. Data Description • Best Data Set:July 4, 2006 07:44 – 10:09 UT, Target: AR 10898 • DOT:H (656.3 nm, ± 0.35 Å), Ca II H (396.8 nm), G-Band (430.5 nm), blueandredcontinuum (432 and 651 nm)FoV: 85“ x 65“Time Cadence :< 30 sSpatial Resolution:0.2“ (speckled) • CDS:He I (58.43 nm, T ~ 4x 104 K), O III (59.96 nm, T ~ 105 K), O V (62.97 nm, T ~ 2.5x 105 K), Ne VI (56.28 nm, T ~ 4x 105), Mg IX (38.6 nm, T ~ 1 MK), Si XII (52.07 nm, T ~ 2 MK)FoV: 2“x240“, sitandstaremode; rasterseach ~5.5 hoursforco-alignmentTime cadence:15 sSpatialresolution:2“ x 1.6“ pixels • MDI:highresolutionwhitelightimagesandmagnetogramsFoV:614“ x 300“Time cadence:1 minSpatial Resolution:0.6“/pixel • TRACE:17.1 nm, ~1 MKFoV:511“ x 511“Time Cadence:< 90 sSpatial Resolution:0.5“/pixel • RHESSI: > 3 keVFoV:full diskTime cadence:~ 4 sSpatial resolution:~ down to 2“Spectral resolution:1 keV no attenuation

  4. Target AR 10898 SOHO/MDI White Light 3 RHESSI microflaresobservedby DOT and CDS (plus otherinstruments): RHESSI peaktimes: ~08:26 UT, ~08:38 UT, ~08:45 UT GOES classification:< A9/A1 with/without background

  5. Coronal appearance 08:26 UT event RHESSI 3-8 keV jet Images: TRACE 17.1 nm, T≈1 MK Contours: MDI Magnetic Field(~ 45 min earlier ) +70, +200 G −1500, −600, −200 G

  6. Coronalappearance 08:45 UT event Images: EIT 19.5 nm, T≈1.5 MK RHESSI 3-8 keV

  7. DOT – Chromospheric Response

  8. Chromosphericsignatures 08:26 UT event Hαvelocityscale: [-5,5] km s-1

  9. Chromosphericsignatures 08:38 UT event

  10. Chromosphericsignatures 08:45 UT event

  11. CDS spectrogram chromosphere T≈ 40 000 K

  12. CDS lightcurves 1st event Northern footpoint Log Intensities [ergs cm-2 s-1 sterad-1Å-1] Velocities [km s-1] Southern footpoint

  13. CDS lightcurves 2nd event Log Intensities [ergs cm-2 s-1 sterad-1Å-1] Velocities [km s-1]

  14. CDS lightcurves 3rd event Log Intensities [ergs cm-2 s-1 sterad-1Å-1] Velocities [km s-1]

  15. CDS Flows at the flare peak 08:26 UT event, southern brightening -> such two-componentprofilesareobservedatandbetweentheboth CDS brightenings

  16. Velocities He I line CDS spectrogram chromosphere

  17. CDS spectrogram corona T≈ 2 MK

  18. CDS velocities - summary • 1st event: downflows ∼10–40 km s−1 in He I, O V, Ne VI (Chromosphere, TR) • 2ndevent: upflows ∼10–50 km s−1 in He I, O V, Ne VI • 3rdevent: - southern brightening: downflows∼ 20 km s−1 inHe I and O V • noclearvelocitysignal in thecoronal Si XII line • oppositelydirected, highvelocityflowsattheflarepeaks(spatiallyunresolved) in severallines: upflows:upto80 km s−1 , downflows:upto190 km s−1 • strong downflows (supersonic) intothepenumbra in He I, O V ->consistentwithplasma in free fall

  19. Non-Thermal Electron Flux Density EnergyFluxDensity: Energyflux/ Impact Area -> determinesifevaporationis`gentle‘ or`explosive‘ Electronenergyflux -> RHESSI, Impact area-> DOT (5∙1015 – 4 ∙ 1016 cm2) Result: - highEnergyFluxDensityfound: F ≈ 1.1 - 1.4 ∙ 1010erg cm-2 s-1 - thresholdfromgentleto explosive evap.: ≈1010erg cm-2 s-1

  20. Conclusions • Imaging: • Multi-wavelengthappearanceandmagneticfieldenvironment in basicagreementwiththestandardflare model • finelystructuredbrightenings (DOT, TRACE) • DOT Ha Doppler maps:loop-shapedfibrilswithenhancedvelocitybetweenbrightening -> twistingmotions? • Timing ofthe DOT and CDS emissionfollows RHESSI X-raylightcurve

  21. Conclusions EUV Spectroscopy: - comparisonwithflaresimulations (e.g. Fisher et al. 1984): 1stevent: explosive evaporation , 2ndevent: gentleevaporation - indicationsoftwistingmotions - strong downflowsintothepenumbra-> plasma in free fall? RHESSI Spectroscopy: - evidencefor non-thermal e- - non-th. energyfluxdensityatthethresholdbetweengentleand explosive evaporation Fisher, G. H., Canfield, R. C., & McClymont, A. N. 1984, ApJ, 289, 414

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