Transient events as seen by SoHO and TRACE

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Transient events as seen by SoHO and TRACE

• M.S. Madjarska J.G. Doyle

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We will review the observational characteristics
of transient phenomena

• Spicules, EUV Bright Points, Explosive events,
  Blinkers, Network and cell brightenings
• Discuss their appearance in different
  instrument observations
• Discuss their similarities and/or differences.

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Spicules

• Secchi (1877), Beckers (1972) ,Wilhelm (2000)
  and Sterling (2000)
• Chromospheric jet-like structures (H?)
• Te 1.3 104 K and Ne 1 1011 cm-3
• Lifetime - less than 15 mins, 14 arcsec long, 2
  arcsec in diameter
• Accelerated in 30 s over 1.5 arcsec to a const
  speed of 25 km/s
• Disappear or fall back, occasionally forming an
  arch
• Associated with the magnetic elements of the
  chromospheric network
• Tend to cluster in bushes (Pikelner 1969) or
  rosettes (Uchida 1969)
• Dark mottles were associated with spicules -
  (Georgakilas et al. 2001, Zachariadis et al.
  2001, Tziotziou et al. 2003)
• H? spicules ? EUV spicules (from N II to O V)
• TR envelope of the spicules (Mariska et al. 1978,
  Withbroe 1983)

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• Budnik et al. (1998) - evaporation of spicular
  material
• Macro-spicules (1969) - cor. hole feature, length
  - 5 to 60 arcsec, width - 5 to 30 arcsec (Bohlin
  et al. 1975)
• LOS velocities 200 km/s
• Parenti et al. (2002) - Te 2 105 K, Ne 2-3
  1010 cm-3
• Macro-spicules ? Explosive events (Wilhelm 2000)

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EUV Bright Points

• 1969 - Vaiana et al. (1970)
• Skylab mission - Golub 1980, Webb 1986, Habbal
  1992
• Size - 30-40 arcsec
• Lifetime - EUV - 20 hrs (Zhang et al. 2001),
  X-ray - 8 hrs (Golub et al. 1974)
• Density - Ne (O IV) 1.9 1010, (Mg VII) 0.9 109 ,
  (Si IX) 5 108 (Del Zanna et al. 2003)
• quiet Sun and coronal holes, at the network
  junctions
• Associated with small bipolar magnetic features
  (Webb et al. 1993, Brown et al. 2001, Madjarska
  et al. 2003)
• Sheely Golub (1979) - consist of 2-3 loops,
  evolving 6 min
• Habbal (1990) - complex of small-scale loops at
  different temperatures

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• Madjarska et al. (2003)

EIT observations in Fe X II 195 Å.
Magnetic field (MDI) temporal evolution.
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S VI intensity images with overploted Left
panel magnetogram contour map, green - positive
polarity, blue - negative Right panel relative
Doppler shifts, green - 3 km/s, blue - -3 km/s,
red - 8 km/s.
Presence of small-scale ( 6 arcsec) transient
brightenings within the BP with a periodicity of
6 min. Doppler shift in the order from -10 to
10 km/s, predominantly red-shifted.
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Explosive events

• Brueckner Bartoe (1983) - high velocity events,
  from 2 104 K (C II) to 2 105 K (N V) , HRTS,
  SUMER
• Doppler shift up to 250 km s-1
• Spatial dimensions 3-4 arcsec, Lifetime 200
  s
• Network lanes Regions with weak and mixed
  polarity fluxes or on the border of regions with
  large concentration of magnetic flux
• Chromospheric origin (Madjarska Doyle 2002) and
  no evidence for presence at coronal temperatures
  (Teriaca, Madjarska Doyle 2002) (SUMER)
• Winebarger et al. (2002) - TRACE 171 Å response
  of explosive events (SUMER)?!?!

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• Increase with factor of 3 of the electron
  density during explosive events.
• Identified simultaneously in SUMER and CDS data
  (Madjarska Doyle 2003)

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Blinkers

• Harrison (1997), Harrison et al. (1999) -
  enhancements in the intensity flux of transition
  region lines (O III, O IV, O V) at the network
  junctions
• Modest appearance at coronal temperatures
• Lifetime 17 min, Area 8 ? 8 arcsec2
• Brkovic et al. (2001) - lifetime in the range
  3-110 min
• Average intensity increase of 1.5
• Occur above large or strong magnetic fragments
  with 75 where one polarity dominates (Bewsher et
  al. 2002)
• Bewsher et al. (2002), Parnell et al. (2002)
• Identified in simultaneously obtained SUMER and
  CDS data (Chae et al. 2000, Madjarska Doyle
  2003)

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• Within each blinkers, SUMER reveals the presence
  of small-scale (3-5 arcsec), short-lived (2-3
  min) bright features.
• Small increase in the emission of the blue and
  red wings
• Doppler shifts in blinkers range from -5 to 25
  km/s - predominantly red-shifted.
• Magnetic flux increase during blinker phenomena
  (BBSO).

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Network and cell brightenings

• Harra et al. (2000) - CDS
• Network - larger, 150 s and 1026.9 ergs per
  event
• Cells - 96 s and 1025.8 per event
• 1-5 CDS pixels size
• Gallagher et al. (1999) - transient brightenings
  (O V and He I/CDS)
• Duration 80 - 200 s, Size 6 000 - 10 000 km,
  LOS vel. 13 km/s
• Berghmans et al. (1998) - EIT

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Appearance in different instrument observations

• Explosive events - HRTS, SUMER, CDS, TRACE
• Blinkers - CDS, SUMER, EIT
• Bright Points - Skylab, HRTS, EIT, TRACE, Yohkoh,
  SUMER, CDS
• EUV Spicules - Skylab, EIT, TRACE, SUMER, CDS
• Network and Cell Brightenings - CDS, EIT

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Are all these phenomena closely related or even
represent the same phenomenon but given different
names depending on their characteristics as
observed at particular wavelength or by a
particular instrument?
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Similarities and Differences

• Blinkers ? Explosive events
• Blinkers ? Bright Points
• Blinkers ? Spicules and Macro-spicules
• Explosive events ? Spicules and Macrospicules
• Cell and network brightenings

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• Better and more spatial, temporal and spectral
  multi-instrument and multi-wavelength
  observations are needed!!!!