Comparison of Blinkers and Explosive Events

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Comparison of Blinkers and Explosive Events

• Danielle Bewsher
• (dbewsher_at_esa.nascom.nasa.gov)
• ESA Space Science Dept, NASA/GSFC, USA
• Davina Innes
• Max-Planck-Institute fur Aeronomie, Lindau,
  Germany
• Clare Parnell
• University of St Andrews, St Andrews, Scotland

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Introduction - Blinkers

• Small bright intensity enhancements
• Seen in EUV lines, e.g. O V, O IV (SOHO/CDS), He
  II (SOHO/EIT)
• Discovered by eye using SOHO/CDS (Harrison, 1997
  Harrison et al., 1999)
• More recently automated identification methods
  developed (Brkovic, Solanki and Rüedi, 2001
  Bewsher, Parnell and Harrison, 2002)
• Events found throughout
• Quiet Sun (Bewsher, Parnell and Harrison, 2002)
• Active Region (Parnell, Bewsher and Harrison,
  2002)
• Believed to be enhancements in density or filling
  factor, not temperature
• Preferentially occur above large or strong
  magnetic fragments
• Doppler and non-thermal velocities are
  preferentially more red-shifted and greater than
  normal transition region plasma

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Introduction Explosive Events

• Broadened and/or shifted line profiles
• Observed in EUV lines
• Discovered with HRTS (Brueckner and Bartoe,
  1983), more recently observed with SOHO/SUMER
• Found in Quiet Sun, Active Regions and Coronal
  Holes
• Believed to be caused by magnetic reconnection
  (Innes et al., 1997) during cancellation of
  photospheric field with emerging flux (Dere et
  al., 1991) or dissipating AR flux (Porter Dere,
  1991)
• Occur above regions of mixed polarity field near
  magnetic neutral lines (Chae, Yun Poland, 1998)

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Blinker Explosive Event I SUMER CDS images

• Explosive Event (S1) at top of SUMER single slit
  image
• 3 Blinkers (C1, C2, C3) observed at top of CDS
  raster along SUMER slit
• ? - midpoint of blinkers
• Dashed line position of SUMER slit
• Only example of co-spatial and co-temporal
  blinker and explosive event

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Blinker Explosive Event II -SUMER CDS
lightcurves

• Solid lines show lightcurve of SUMER region S1
  and blinker C2
• Dashed line shows the lightcurve of the CDS
  region that refers directly to the SUMER region
  S1
• Times t1, t2 and t3 refer to the time before, the
  time of and the time after the CDS raster shown
  on the previous slide
• - mark start and end of blinker
• Evidence of blinker seen in SUMER lightcurve?

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Blinker Explosive Event III SUMER CDS line
profiles

• Times t1, t2 and t3 refer to the time before, the
  time of and the time after the CDS raster shown
  previously
• Explosive Event can be seen clearly in the SUMER
  line profile as line shift and enhanced wings
• Blinker can be seen in CDS line profile as
  increase in line amplitude
• No evidence of explosive event in CDS line profile

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Blinker Explosive Event IV More CDS
lightcurves line profiles
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Blinker no Explosive Event I SUMER CDS
images

• 2 brightenings (S2, S3) seen in SUMER single slit
  image, but no explosive events
• 2 blinkers (C4, C5) lie along SUMER slit in CDS
  raster
• ? - midpoint of blinkers
• Dashed line position of SUMER slit
• 2 examples out of ten where blinkers are present
  and explosive events are not

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Blinker no Explosive Event II SUMER CDS
lightcurves

• Solid lines show SUMER region S2 and lightcurve
  of blinker C4
• Dashed line shows lightcurve of CDS pixels that
  directly refer to the SUMER region S2
• - mark start and end of blinker
• Times t1, t2 and t3 refer to the time before,
  time of, and the time after the CDS raster shown
  on the previous slide
• Evidence of blinker in SUMER lightcurve?

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Blinker no Explosive Event III SUMER CDS
line profiles

• Times t1, t2 and t3, refer to the time before,
  the time of and the time after the CDS raster
  shown previously
• Intensity enhancements seen in both SUMER and CDS
  line profiles at different times
• No evidence of significant line shift or
  broadening in either SUMER or CDS line profiles

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Blinker no Explosive Event IV SUMER CDS
lightcurves

• Solid lines show SUMER region S3 and lightcurve
  of blinker C5
• Dashed line shows lightcurve of CDS pixels that
  directly refer to the SUMER region S3
• - mark start and end of blinker
• Times t1, t2 and t3 refer to the time before,
  time of, and the time after the CDS raster shown
  on the previous slide
• Evidence of blinker in SUMER lightcurve?

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Blinker no Explosive Event V SUMER CDS line
profiles

• Times t1, t2 and t3, refer to the time before,
  the time of and the time after the CDS raster
  shown previously
• Small changes in intesity as blinker reaches the
  end of its lifetime
• SUMER lightcurve and line profile shows an
  increase in intensity at time t2, which is not
  visible in CDS
• No evidence of significant line shift or
  broadening seen in the SUMER or CDS line profiles

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Explosive Event no Blinker I SUMER CDS
images

• Explosive event, S4, seen at top of SUMER single
  slit image
• No blinker seen at corresponding position, C6, in
  CDS raster
• ? - midpoint of blinkers
• Dashed line position of SUMER slit
• One of seven examples where an explosive event is
  observed but no associated blinkers are seen

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Explosive Event no Blinker II SUMER CDS
lightcurves

• Solid lines show SUMER region S3 and lightcurve
  of blinker C5
• Dashed line shows lightcurve of CDS pixels that
  directly refer to the SUMER region S3
• Times t1, t2 and t3 refer to the time before,
  time of, and the time after the CDS raster shown
  on the previous slide
• Intensity enhancement seen in SUMER but the CDS
  lightcurve does not meet the criteria for a
  blinker

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Explosive Event no Blinker III SUMER CDS
line profiles

• Times t1, t2 and t3, refer to the time before,
  the time of and the time after the CDS raster
  shown previously
• Explosive event can be seen as enhancement in
  both red and blue wings of SUMER profiles
• No evidence of explosive event in CDS line
  profiles

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Discussion

• Only one co-incident and co-spatial blinker and
  explosive event
• What are the chances that a blinker and an
  explosive event could randomly occur together?
• Evidence of blinkers seen in SUMER lightcurves
• Would they meet the same criteria for identifying
  blinkers?
• Would one event or many smaller/shorter lived
  events be found?
• No evidence of explosive events (significant line
  shifts or broadenings) in CDS blinker line
  profiles
• Would we expect to see them given the resolution
  of CDS?
• Would we see significant shifts/broadenings in
  the individual pixels that make up the blinker?
• Is the same mechanism responsible for both
  blinkers and explosive event?
• What is causing the 3 different scenarios
  (blinker only, explosive event only, and both
  blinker and explosive event) to occur?

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References
Data used is courtesy of SOHO/CDS and SOHO/SUMER
consortiums. SOHO is a project of international
cooperation between ESA and NASA

• Bewsher, D., Parnell, C.E., Harrison, R.A.
  2002, Solar Phys., 206, 21.
• Brkovic, A., Solanki, S., Rüedi, I. 2001, AA,
  373, 1056.
• Brueckner, G., Bartoe, J.-D. 1983, ApJ, 272,
  329.
• Chae, J., Yun, H., Poland, A. 1998, ApJ Sup,
  114, 151.
• Dere, K., Bartoe, J.-D., Brueckner, G., Ewing,
  J., Lund, P. 1991, JGR, 96, 9399.
• Harrison, R.A. 1997, Solar Phys., 175, 467.
• Harrison R.A., Lang, J., Brooks, D., Innes, D.
  1999, AA, 351, 1115.
• Innes, D., Inhester, B., Axford, W., Wilhelm, K.
  1997, Science, 386, 811.
• Innes, D. 2002, AA, 378, 1067.
• Parnell, C.E., Bewsher, D., Harrison, R.A.
  2002, Solar Phys., 206, 249.
• Porter, J., Dere, K. 1991, ApJ, 370, 775.

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Properties of Blinkers Explosive Events