太陽電波の長期多波長観測と地球上層大気

太陽電波の長期多波長観測と

地球上層大気

柴崎清登

概要

• 日本における太陽電波フラックス観測

• 相対黒点数と電波フラックスの相関

• 電波放射機構と太陽大気

• 太陽活動とコロナ加熱

• Blind Source Separation法による解析

• 各Sourceの物理的意味

• 各Sourceと地球上層大気の相関

• まとめ

Solar Radio Observations in Japan

(Toyokawa / Nobeyama)

• Total flux and polarization measurements at:

– 1.0, 2.0, 3.75, 9.4, 17, 35 and 80 GHz

– longest observation is at 3.75 GHz since Nov. 1951

– Robust absolute calibration (1.0 ~ 9.4 GHz)

• Data use (open use through INTERNET)

– studies of particle accelerations in solar flares (0.1 second

data)

– index of solar activity (daily data)

– http://solar.nro.nao.ac.jp/norp/

Nobeyama Radio Polarimeters

0 50 100 150 200 250 300 350 400 450 1 A U Cor rect ed Mon thl y Mean Flu x (SFU )

Microwave Flux (1951 Nov. - 2013 June) & Sunspot Number

9.4GHz 3.75GHz 2.0GHz 1.0GHz Spot/2+200 Prepared by K. Shibasaki July 25, 2013

Correlation between 3.75GHz Flux (NBYM)

and Sunspot Number(ISN/SIDC)

Correlation Coefficient between

Sunspot Number and Microwave Flux

Frequency

(GHz)

Wavelength

（ｃｍ）

Correlation

Coefficient (r)

1.0

30

_0.962

2.0

15

_0.975

3.75

8

0.976

9.4

3.2

0.940

• ~10cm (3 GHz) fluxes show the highest correlation.

Radio Emission Mechanisms from the Sun

• Microwave (frequncy=1 ~ 10 GHz, wavelength= 30~3 cm)

– accelerated motion of electrons (classical EM theory)

• collision with ions (Coulomb force, f-f emission)

• gyration around magnetic field (Lorenz force, gyro-resonance emission, gyro-synchrotron emission)

– f-f emission

• Hot and dense plasma in the upper atmosphere (corona, transition region, chromosphere)

– gyro-resonance emission

• Thermal electrons gyration around very strong sunspot magnetic field (2nd _{or 3}rd _harmonics)

– gyro-synchrotron emission

• Non-thermal (accelerated in solar flares) electrons gyrating around active region magnetic field (higher harmonics,

Radio brightness temperature and

integrated flux

corona) the in 0.2 ere, choromosph the in (0.1 constant : f -f thermal : ) (cm t coefficien absorption : depth, optical : perature, plasma tem : angle, solid : re, temperatu brightness : h, wavelengt : constant, Boltzmann : , brightness : /Hz), (W/m density flux : , 2 1 -2 / 3 2 2 2 2                     







T f n T T k I F d d d Te T d T k Id F b B b b B 

Brightness temperatures during

solar minimum period

Frequency

（GHｚ）

Wavelength

（ｃｍ）

Flux (SFU)

Tb (K)

1.0

30

45

200,000

2.0

15

60

66,000

3.75

8

80

25,000

9.4

3.2

260

13,000

(A flat circular disk is assumed for Tb, by neglecting limb brightening.)

• Effective temperatures (Tb) are located in the Transition region.

• This is the reason why microwave fluxes are good indexes of solar activity or coronal / chromospheric heating rate.

(Transition region works as an amplifier of solar activity.)

Solar Atmosphere

Microwave emission

Causal Chain: SSN – Microwave Flux

• Sunspots are phenomena below the

temperature minimum.

• Microwave emission comes from mainly

transition region which is located above the

temperature minimum.

• Hence the causal chain is the coronal /

chromospheric heating mechanism.

• The heating rate must be proportional to

magnetic flux at the photosphere.

Solar activity and its indexes/proxies

Solar

activity

?

Hα plage area Sunspot number (Group number)

Total magnetic flux

Microwave flux

Total solar irradiance

Spectral solar irradiance

Number of flares and CMEs

Indexes / proxies Influences

Interplanetary space and Heliosphere

Solar wind Cosmic ray

Earth upper atmosphere

Magnetosphere Radiation belt Ionosphere (foF2) Stratosphere Geomagnetic activity Auroral activity Satellite drag Ph ot ospher e Cor ona / Chr omo spher e Coronal / chromospheric Heating

Coronal / Chromospheric Heating

• Not only heating, but also temperature

regulated plasma supply is required.

• Should work also during activity minimum.

• Should work also in unipolar open magnetic

field regions (coronal holes, Solar Wind source).

• Heating rate should be proportional to

magnetic flux.

• Should work below the corona / chromosphere

長期多波長データの集約

(Blind Source Separation)

• 長期多波長のデータの中から統計的手法によって少ない成分

（source)を取り出し、その物理的意味を議論する

• 使用データ

– 豊川/野辺山の1.0, 2.0, 3.75, 9.4 GHz & カナダの2.8 GHz 波長：30, 15, 8, 3.2 & 10.7 cm – すべてのデータの揃った、1957年11月以降のデータを使用（20357日） – １AU補正をし、F10.7に×0.9の補正を施した – データギャップを埋めた

• 参考文献

– “Synoptic radio observations as proxies for upper atmosphere

modelling” by T. Dudok de Wit, S. Bruinsma, K. Shibasaki, J.

Space Weather Space Clim, Vol. 4, A06, 2014

BSSの仕組み

• すべてのデータを行列で表現 I(t,λ)：n_t×n_λの行列 n_t：データ点数(20,357)、n_λ：測定波長点数（5） V(t): n_t×n_s , S(λ): n_s×n_λ source spectrum ns ：number of sources • V(t)とS(λ)を求める(BSS) – 数少ないsource(s)で記述できるようにする 2014/03/13 IUGONET2014＠STE研 16 noise                                                  ) S( V(t) 57) number(203 data ) I(t, (5) wavelength  

The EUV Sun as the superposition of

elementary Suns (A&A 487, 2008)

Nt=2146

Nλ=1546

電波スペクトルの３つのソース

Spectral Solar Irradiance と

地球熱圏密度モデル（衛星ドラッグ）

• Drag Temperature Model DTM2012_F10 vs DTM2012_F30

まとめ

• 日本における太陽電波長期多波長観測

• 電波データと太陽活動のよい相関

• 太陽活動と彩層・コロナ加熱：太陽活動は加熱率

• Blind Source Separation法によって、太陽電波の長期

多波長データを解析して、３つのソースを同定した

• S1(短波長), S2(10cmピーク), S3(長波長)

• S3がEUV/UVとの相関がよい

• 熱圏密度のモデル（衛星のドラッグ）にはF10よりF30

が有効である（S3の有効性）

• F30（１GHｚ電波フラックス）の観測の重要性

END

Diamagnetic Force

B

magnetic moment （μ=k_BT/B）

In the presence of gradient of magnetic flux density (B), charged particles are pushed toward weak B region due to their magnetic moments (mirror force). This force is not included in MHD.

1

1























dR

dB

B

L

L

T

k

dR

dB

B

T

k

dR

dB

F

B B B B



Hot plasma flows upwards

• Condition that upward diamagnetic force

exceeds downward gravity force is:

• In the solar corona

Temperature dependent plasma upflow

1

/

2

/

₀ 0







_B B p B d u

H

L

L

g

m

T

k

F

F

0 0

2

g

m

T

k

H

p B



)

60

/

(

~

"

100

/

"

100

(

~

60

~

6 6 6 0

Mm

L

L

T

L

T

T

Mm

H

B B B









　

）

2013/11/11 ISSIws2013@Bern 24

Hot Plasma Supply in Open Field Region

1. energy supply (wave, magnetic) 2. thermalization / dissipation 3. heat conduction

?

4. evaporation / ablation

?

5. Solar Wind Coronal heating (1, 2)

Proposal of a simple mechanism

• Supply of hot plasma directly from below the photosphere, where

temperature is higher, through magnetic flux tubes due to diamagnetic force of each plasma particles contained in the tube.

– Leakage of hotter plasma inside through magnetic flux tubes.

• Integrated magnetic flux is proportional to number of flux tubes (~1,500G), hence the supply rate of hot plasma is proportional to integrated magnetic flux.

• Magnetic fields at the photosphere are concentrated as flux tubes and plasma inside tubes are isolated (dark sunspots at the photosphere where ionization degree is very low).

• This mechanism satisfies most of the requirements for coronal / chromospheric heating.