Presentation is loading. Please wait.

Presentation is loading. Please wait.

2004 Oct. Quiet Sun and Active Region Studies by Nobeyama Radioheliograph Kiyoto SHIBASAKI Nobeyama Solar Radio Observatory NAO/NINS.

Similar presentations


Presentation on theme: "2004 Oct. Quiet Sun and Active Region Studies by Nobeyama Radioheliograph Kiyoto SHIBASAKI Nobeyama Solar Radio Observatory NAO/NINS."— Presentation transcript:

1 2004 Oct. 29NBYM04@Kiyosato Quiet Sun and Active Region Studies by Nobeyama Radioheliograph Kiyoto SHIBASAKI Nobeyama Solar Radio Observatory NAO/NINS

2 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

3 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 δsunspots

4 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)

5 Emission mechanisms Thermal f-f emission –Tb = T (τ ≫1) –Tb = Tτ ∝ EM/√T ( τ ≪1) Thermal gyro-resonance emission –Tb = Tτ ∝ NT S ( τ ≪1) N:density, T: temperature, S: harmonic number at 17 GHz: S = 3, B = 2000 Gauss, purely polarized

6 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

7 Radio Synoptic Chart Carrington Longitude Heliographic Latitude

8 Radio Butterfly Diagram

9 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

10 Gyro-resonance emission Sunspot associated emission –At 17 GHz, 2 nd harmonics: 3000 Gauss 3 rd harmonics: 2000 Gauss –Thin iso-Gauss layer ~ (V th /C) * L B –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

11 Umbral Oscillation

12

13 penumbraumbra Temperature minimum Gyroresonance layer (2000 Gauss) Sound wave 17GHz F = (g/4π)√(γμ/RT) 6 mHz ~ 4,000 K g: gravity, γ=5/3, μ=1.5, R:gas constant, T:temperature

14 Solar Cycle Variation (1992 ~ 1994)+11 Year

15 Relation to solar cycle phase Activity cycle phase ( θ ) and frequency –F -3 (θ) = 5.58× ( 1 + 0.07 ×θ ) = 5.58 + 0.39×θ θ = (year – 1996.) / 11. 0 ≦ θ ≦ 1 、 5.58 ≦ F -3 ≦ 5.97 Activity cycle and sunspot temperature –T 3 (θ) = (12/F -3 ) 2 = 4.62 ×(1 – 0.14×θ) = 4.62 – 0.65 ×θ 4.62 ≧ T 3 ≧ 3.97 ( Sunspot cooling toward minimum: 650 K )

16 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)


Download ppt "2004 Oct. Quiet Sun and Active Region Studies by Nobeyama Radioheliograph Kiyoto SHIBASAKI Nobeyama Solar Radio Observatory NAO/NINS."

Similar presentations


Ads by Google