Quiet Sun and Active Region Studies by Nobeyama Radioheliograph

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Quiet Sun and Active Region Studies by Nobeyama
Radioheliograph

• Kiyoto SHIBASAKI
• Nobeyama Solar Radio Observatory
• NAO/NINS

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Characteristics of NoRH for QS and AR studies

• Full disk imaging capability
• Uniform data set for one solar cycle
• Polarization measurement at 17 GHz
• High temporal resolution and long (8hrs)
  continuous data (spectral analysis of
  oscillations)
• Limited angular resolution
• Ambiguity of weak (several hundreds K) features

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Research subjects

• QS
• Polar brightening
• Coronal hole brightening
• AR
• Magnetic field
• Gyro-resonance, B(polarization degree),
  B?(polarization reversal)
• Sunspot
• Umbral oscillation (thermometer)
• Weak activities
• Xbp / transient brightenings
• Small and frequent brightening above dsunspots

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Published papers

• QS
• Coronal hole (Gopalswamy, 99, Krissinel et al,
  00, Yoshiike et al., 00)
• Polar region (Shibasaki, 98, Nindos et al, 99)
• Large structure (Chertok, 01)
• Global solar activity (Gelfreikh et al., 02,
  Gelfreikh et al., 02)
• Limb brightening (Selhorst et al., 03, Selhorst
  et al, 04)
• AR
• S-component (Shibasaki et al., 94)
• Polarization reversal (Ryabov et al., 99)
• Umbral oscillation (Gelfreikh et al., 99,
  Shibasaki, 01)
• AR evolution (Lara et al., 98, Kundu et al., 01)
• Current sheet (Uralov et al., 00)
• AR magnetic field (Zhang et al., 02)
• Sunspot atmosphere (Yu et al., 02)
• Weak Activities
• X-bp (Kundu et al. 94, Gopalswamy et al., 96,
  Maksimov et al., 01)
• Transient brightening (White et al., 94)
• Small bursts above delta spot (Shibasaki, 96)
• X-ray jets (Kundu et al., 97, Kundu et al., 99)

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Emission mechanisms

• Thermal f-f emission
• Tb T (t1)
• Tb Tt?EM/vT (t1)
• Thermal gyro-resonance emission
• Tb Tt?NTS (t1)
• Ndensity, T temperature, S harmonic number
• at 17 GHz S 3, B 2000 Gauss, purely
  polarized

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Quiet Sun and solar cycle

• Large structures
• Limb brightening studies of fine structure in
  the chromosphere
• Polar brightening studies of atmosphere in the
  polar region (anti-correlation with sunspot
  number) limb brightening polar coronal hole
• Coronal hole brightening/dimming studies of
  lower atmosphere in the coronal hole

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Radio Synoptic Chart
Heliographic Latitude
Carrington Longitude
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Radio Butterfly Diagram
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Active regions

• Diffuse component
• f-f emission from hot and dense plasma
  (Estimation of Emission measure)
• magnetic field strength from circular
  polarization degree
• Compact component
• Magnetic field structure of sunspots
  (multi-wavelength)
• Sunspot oscillation 3-minutes oscillation/
  upward traveling sound wave / temperature
  measurement / solar cycle dependence

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Gyro-resonance emission

• Sunspot associated emission
• At 17 GHz, 2nd harmonics 3000 Gauss
• 3rd harmonics 2000 Gauss
• Thin iso-Gauss layer (Vth/C) LB
• High degree of circular polarization (100 )
• Umbral oscillation
• 3 min. oscillation of gyroresonance emission
• Absorption of 5 min. oscillation
• Mechanism upward propagating sound wave
  generated at temperature minimum plateau region
  (lower cutoff frequency)
• Diagnostic tool of sunspot temperature
• Solar cycle variation of sunspot temperature

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Umbral Oscillation
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(No Transcript)
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17GHz
Sound wave
Gyroresonance layer (2000 Gauss)
Temperature minimum
penumbra
umbra
F (g/4p)v(?µ/RT) 6 mHz 4,000 K g
gravity, ?5/3, µ1.5, Rgas constant,
Ttemperature
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Solar Cycle Variation
(19921994)11 Year
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Relation to solar cycle phase

• Activity cycle phase(?)and frequency
• F-3 (?) 5.58(1 0.07 ?)
• 5.58 0.39?
• ? (year 1996.) / 11.
• 0 ??? 1?5.58 ?F-3 ?5.97
• Activity cycle and sunspot temperature
• T3(?) (12/F-3)2
• 4.62 (1 0.14?)
• 4.62 0.65 ?
• 4.62 ? T3 ? 3.97(Sunspot cooling toward minimum
  650 K)

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Sunspot seismology

• Windowed Fourier spectral analysis shows
• Frequency modulation of hours appearance of
  g-mode oscillation through the flux tube ?
• High spectral resolution reveals spectral fine
  structures
• Frequency difference in different location in
  umbra sunspots consist of many elements
  (spaghetti model)