2. Importance of polar fields
to predict future solar activity
2
N
S
N
S
N
S
Cause
Weak
polar field
Result
Less number
of sunspots
2
130 rotations in 11 year
▽Ω-dynamo
3. Reversal of high-latitude (>55 deg) field
Sunspot number
1.0
0.0
-1.0 North
South
Average high-latitude field Wilcox
西暦
西暦
Polar fields reverses
at around solar maximum
3
4. Joy’s law and
reversal of poloidal field
N
N
S
S
Diffusion
Meridional flow
Tilt of sunspot pair
due to Colioris force
Results in reversal
5. Polar observations from ground
N55 degree
S55 degree
Polar field= single pixel observations above latitude of 55 degree.
SOHO
5
W:plus
B:minus
10. Current
understanding
Hinode result
Polar
magnetic
fields
Extended weak
fields (lower
energy state)
Sunspot-like kG
patches (higher
energy state)
Polar field
reversal
Reverses at
around solar max.
(2013 May)
North reverses at
around 2012 May
South stable
Poloidal
fields
Bipolar Quadruple
Summary of Hinode observations
10
32. 対流と弱い磁場があれば強い磁場ができる
という割と普遍的なプロセス
Parker (1978); Hasan (1985), Hasan et al. (2003), Bunte, Hasan,Kalkofen, (1983)
G4004
2
1
8
2
2
»»
»
up r
r u
p
B
Be
kG21
8
2
-»
=+
B
PBP ei p
Magnetic
Flux tube
Solar
surface
Granular
flow
Downflow
Inside flux tube
32
32
Sub-equipartition磁場 Super-equipartition磁場
磁場による対流
熱入力の遮断
冷却と下降流
の発生
圧力平衡に
より磁場が強まる
44. ローカルダイナモによる
宇宙磁場の生成
• Equi-partition field due to local dynamo OK!
– n=10^-3 cm^-3
– v=3x10^5 m/s
– T=100eV (10^6K)
• Maximum turnover time OK!
– r/v=3x10^23cm/3x10^7cm/s=10^16s<<4x10^17s
(宇宙年齢)
– 最大セルサイズをとったので実際はもっと短い
G!1028
8
6
2
-
·==
=
nkTB
nkT
B
p
p
44