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BEGIN:VEVENT
DTSTAMP:20260511T115407Z
UID:https://www.mps.mpg.de/events/12582/7840830
DTSTART:20180125T100000Z
DTEND:20180125T110000Z
CLASS:PUBLIC
CREATED:20180119T133337Z
DESCRIPTION: Sunspots are the longest known manifestation of solar activity
  and their magnetic nature has been known for more than a century. Despite
  this\, the boundary between umbrae and penumbrae\, the two fundamental su
 nspot regions\, has hitherto been solely defined by an intensity threshold
 . We now unveil the empirical law of the magnetic nature of the umbra-penu
 mbra boundary in stable sunspots: an invariant vertical component of the m
 agnetic field. We study the magnetic nature of umbra-penumbra boundaries i
 n sunspots of different sizes\, morphology\, evolutionary stage\, and phas
 e of the solar cycle. We use a sample of 88 scans of Hinode/SOT spectropol
 arimeter to infer the magnetic field properties at the umbral boundaries. 
 We define these boundaries by an intensity threshold and perform a statist
 ically analysis of the magnetic field properties at these boundaries. We s
 tatistically prove that the umbra-penumbra boundary in stable sunspots is 
 characterised by an invariant value of the vertical component of the magne
 tic field: The vertical component of the magnetic field strength does not 
 depend on the umbra size\, its morphology\, and phase of the solar cycle. 
 With statistical Bayesian inference\, we find that the vertical component 
 of the magnetic field strength is\, with 99\\% likelihood\, in the range o
 f 1849-1885 G with the most probable value of 1867 G. In contrast\, the ma
 gnetic field strength and inclination averaged along individual boundaries
  are found to be dependent on the umbral size: The larger the umbra\, the 
 stronger and more horizontal the magnetic field at its boundary is.\nVortr
 agende(r): Jan Jurčák 
LAST-MODIFIED:20260220T073826Z
LOCATION:Astronomical Institute of the Czech Academy of Sciences (broadcast
 ed at MPS)\, Raum: Aquila + Bootes
ORGANIZER;CN=Andreas Lagg:mailto:
SUMMARY:ESPOS: ESP Online Seminar: The Magnetic Nature of the Umbra-Penumbr
 a Boundary in Sunspots (J. Jurčák)
URL;VALUE=URI:https://www.mps.mpg.de/events/12582/7840830
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