Solar Active Region emergence and flare productivity

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Solar Active Region emergence and flare
productivity S Dalla(1),
L Fletcher(2) and NA Walton(3) (1)School of
Physics Astronomy, Univ of Manchester (2)Dept
of Physics Astronomy, Univ of Glasgow
(3)Institute of Astronomy, Univ of Cambridge
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Active Region emergence on the Sun

• Emergence of magnetic flux through the solar
  photosphere creates new Active Regions,
  identified from sunspot, magnetogram and H-alpha
  observations.
• New flux emergence has been recognised as an
  important trigger of solar activity, eg solar
  flares and coronal mass ejections.
• Our aim use VO Tools to analyse the process of
  AR emergence and probability of flaring. Look at
  a large statistical sample of Active Regions, by
  retrieving and manipulating entries in catalogues
  of regions and flares.

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Solar region catalogues

• USAF/Mt Wilson catalogue of sunspot regions (24
  years of data, starting 1981) - a log of all
  observations of each region from multiple solar
  observatories. Magnetic classification included.
• NOAA Solar Region Summary (1986 onwards) lists
  all regions observed each day. (via EGSO/SEC)

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AstroGrid workflows

• We used AstroGrid workflows to (1)
  retrieve region catalogues and identify new
  regions (2) study the location of
  emergence with respect to pre-existing regions
  and (3) querying catalogues of flares to
  establish flare productivity.
• Visualisation of results using Topcat.
  
  

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Identifying newly emerged (NE) regions

• Location of first observation of all regions on
  the solar disk (6862 regions)

Old regions
NE
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Results Visibility of new AR emergence

• 3212 were identified as new regions that emerged
  while in view from Earth.
• We find a strong asymmetry in the location of
  emergence of these new regions as viewed from
  Earth.
• Eg 825 regions in bin E60-E40, 177 in W40-W60
  (4.71)
• Does not vary with change in solar magnetic
  polarity
• 
  

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Paired / isolated regions

• Workflow retrieves positions of all regions for
  each day and calculates distance of a new region
  to pre-existing ones
• Paired / isolated

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Magnetic complexity of new/old regions

• We analysed the time history of magnetic
  classification of a region and extracted the
  maximum complexity reached.
• Newly emerged region are considerably simpler
  than older regions.

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Flare productivity

• GOES Soft-X-Ray flare catalogue includes the
  NOAA region number (nar) where an association of
  a flare to an Active Region could be made. (via
  EGSO/SEC).
• Consider medium/large flares (gt C1.0)
• Half of regions do not produce any flares. There
  is a strong dependence of flare productivity on
  magnetic complexity of the region (Sammis et al
  2000).

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Productivity of paired/isolated

• Newly emerged regions have low flare
  productivity. If they are paired, a flare will
  more likely take place in the companion region.
• No clear indication that being paired makes a
  region or its companion more flare productive,
  for cutoff angle 12.

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Conclusions

• There is a strong asymmetry in the location of
  emergence of new regions as inferred from entries
  in the USAF/Mt Wilson catalogue this effect does
  not vary with changing solar magnetic polarity.
• If asymmetry is confirmed as a real
  observational effect, it impacts many detailed
  studies of region emergence.
• 2. Emergence of a region within 12 of a
  pre-existing one does not appear to significantly
  increase the probability of flaring of the new
  region, nor of the companion region.

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