On the Sources Above the Neutral Line of Radial Magnetic Fields

in Solar Active Regions

V. M. Bogod St. Petersburg branch of Special Astrophysical Observatory, Russia

A. G. Stupishin, L. V. Yasnov Radio Physics Research Institute, St. Petersburg University, Russia

PS-type NLS peculiarities:Sizes – 10”… 30”Brightness Temperatures – up to 10 MK (at wavelengths 3…4 cm)High spectral indices at short wavelengthsLow or medium polarization degree

Neutral Line Sources (NLS) – stable, bright, compact sources in microwaves, placed over the neutral line of photosphere magnetic field of active region.

Kundu, M. R. , Alissandrakis, C.E., Solar Phys., 1984, 94, 249

Alissandrakis, C. E., Gel'frejkh, G. B., Borovik, V. N., Korzhavin, A. N., Bogod, V. M., Nindos, A., Kundu, M. R., Astronomy and Astrophysics, 1993, 270, 509.

Alissandrakis C. E., Kundu, M. R. Astroph. J., 1982 , 253, L49

Akhmedov, Sh. B., Borovik, V.N., Gelfreikh, G.B., Bogod, V.M., Korzhavin, A.N., Petrov, Z.E., Dikij, V.N., Lang, K.R., and Willson, R.F., Astroph. J., 1986, 301, 460.

Uralov A.M., Grechnev V.V., Rudenko G.V., Rudenko I.G., Nakajima H. Solar Phys. 2008, V. 249. P. 315.

Observations: WSRT, VLA, RATAN-600, NoRH

Halo-type NLS:Sizes – all active region

RATAN-600 characteristics:frequency range: 0.75 … 18.2 GHz112 frequencies in R and L polarizationmax. angular resolution: 2 arcsecbrightness temperature limit: 5 10∙ -5 K

Ta,V

-411" -81"-329" -246" -163"

400A

B

C

D

sun: 2007/05/18: 4.86[cm]

Ta,I

2000

Source A

Source B Source C

Source D

-411" -81"-329" -246" -163"

MDI Magnetogram 18- May-2007 19:08:00

NLS

sun: 2007/05/18: 4.86[cm]

Ta,I

Ta,V

-411" -81"-329" -246" -163"

400

2000

Source A

Source B

NLS

Source C

A

B

C

D

Source D

10956

A, D – low polarization, related to plagesC, B – cyclotron sources, high polarizationNLS – no polarization, above neutral line

6 8 10 12 140,1

1

10

Flux

, sfu

Frequency, GHz

B-source NLS-source C-source

2007/05/18 NOAA 10956

6 8 10 12 14

10

20

30

40

50

60

70

2007/05/18 NOAA 10956

NLS source

Θ, a

rcse

cFrequency, GHz

θobs

θact

10956

δNLS=3 … 4

6 8 10 12 14 16

-246

-244

-242

-240

-238

-236

-234

2007/05/18 NOAA 10956 Az-24

Pos(

")

Frq (GHz)

Pos(B+C)/2Pos(R+L)/2

6 8 10 12 14 16-244

-242

-240

-238

-236

-234

-232

-230

Pos(

")

Frq(GHz)

Pos(B+C)/2Pos(R+L)/2

2007/05/18 NOAA 10956 Az+24

6 8 10 12 14

-10

-8

-6

-4

-2

0

2

DifP

os(")

Frq(GHz)

2007/05/18 NOAA 10956 Az+24

Pos(B+C)/2-Pos(R+L)/2 Az+24 Az-24

Size: 20”…30” in 6…14 GHz

NLS between cyclotronsources, in the top ofmagnetic field lines

11358

B (NLS) – stable

4 6 8 10 12 14 16 18-0,7

-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

0,1

2011.11.28 NOAA 11358

Ta(V

)/Ta(

I)

Frq (GHz)

Source B

Source C

Source D

4 6 8 10 12 14 16 180,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2011.11.28 NOAA 11358 I

Flux

(sfu

)

Frq (GHz)

δNLS= 0.7

SU N _ A +29:2003/10/31 06:57:19.000

04.93c m

05.26c m

06.52c m

07.03c m

07.59c m T a , V7000 K

-327" 972"-2" 322" 647"

W

0 2 4 6 8 10 12 14 16 180

2

4

6

8

10

12 2003.10.31 NOAA 10486

Ante

nna

tem

pera

ture

, 10

K

Frequency, GHz

4

Intensity, I(b)

0 2 4 6 8 10 12 14 16 18

Frequency, (GHz)

2003/10/31 NOAA 10466VPolarization V

0,0

Ant

enna

tem

pera

ture

, 10

K4

0,5

-0,5

-1,0

1,0

-1,5

-2,0

(a)10486

6

5

4

4.0 5.0 6.0 7.0

Frequency, GHz

Ant

enna

tem

pera

ture

, 10

K4

3

LHRH

Change sign of polarization at 5.7 GHz:ordinary mode emission

10486

-1017" 1012"-2"

Ta

-1017" 1012"-2" -1018" 1013"-2" -1016" 1011"-2" -1017" 1012"-2" -1018" 1013"-2"

E W-1016" 1011"-2"

4.32cm

4.62cm

4.93cm

5.26cm

6.52cm

7.03cm

7.59cm

26.10.2003 28.10.200327.10.2003 29.10.2003 30.10.2003 31.10.2003 1.11.2003

26.10.2003

CS

486

27.10.2003

CS490

491489

486

28.10.2003

CS

486

490491

489

29.10.2003

491

489486

490CS

30.10.2003

491 10489486

490

CS

31.10.2003

486

489

491

490

CS

1.11.2003

486489

492

491CS489

Zheleznyakov, V. V., Zlotnik, E. Ya. 1980: Astronomical Journal (R), 57, 778:Emission of such narrow region because of hot loops or hot current sheets.Estimation of ordinary mode emission region size:

,/2/ HLx - Magnetic field scale,cmLH910 ,1.0/

cmx 7105

10904

Halo-type NLS

-5 8 7 " -2 6 5 "-5 0 6 " -4 2 6 " -3 4 5 "

su n : 2 0 0 6 /0 8 /1 3 : 4 .3 2 [cm ]

T a ,I

2 0 0 0

Source A

Source B

Source C

10904

6 8 10 12 14 160,0

0 ,5

1 ,0

1 ,5

2 ,0

2 ,5

3 ,0

3 ,5

4 ,0

4 ,5

5 ,0

5 ,5

Flu

x, s

fu

F requency, GHz

2006.08.12 I

Source A

Source B

Source C

5 6 7 8 9 10 11 12 13 14 15 163,5

4,0

4,5

5,0

5,5

6,0

6,5 2006.08.12 I

Lo

g T

b, K

Frequency, GHz

Sourc e A

Sourc e B

Sourc e C

6 8 10 12 14 16

0

5

10

15

20

25

30

35

40

45

50

55

2006 .08 .12 I

So

urc

e s

ize

, arc

sec

F requency, G Hz

Source A

Source A (c lean)

Source C (c lean)

Source C

6 8 10 12 14 16115

120

125

130

135

140

145

150

2006 .08 .12 I

So

urc

e s

ize

, arc

sec

F requency, G Hz

Source B

Source B (c lean)

10904

6 8 10 12 14 16

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

Flu

x, s

.f.u

.

F requency, G Hz

2006 .08 .13 10904 I

Sourc e A

Sourc e B

Sourc e C

6 8 10 12 14 163,5

4,0

4,5

5,0

5,5

6,0

6,5

7,0 2006 .08 .13 10904 I

Lo

g T

b, K

F requency, G Hz

Source A

Source B

Source C

6 8 10 12 14 16

15

20

25

30

35

40

45

50

55

60

65

70

2006.08.13 10904 I

Sou

rce

size

, arc

sec

F requency, GHz

Source A

Source C

Source C (c lean)

Source A (c lean)

6 8 10 12 14 1680

90

100

110

120

130

140 2006 .08 .13 10904 I

So

urc

e s

ize

, arc

sec

F requency, G Hz

Source B

Source B (c lean)

6 8 10 12 14 16

-480

-460

-440

-420

-400

-380

-360

-340

2006.08.1310904 I

Pos

ition

, arc

sec

Frequency, GHz

Pos A

Pos B

Pos C

6 8 10 12 14 16

60

80

100

120

140

2006.08.1310904 I

Pos

ition

, arc

sec

Frequency, GHz

Pos C-A

Pos C-B

Pos B-A

6 8 10 12 14 16

40

50

60

70

80

90

100

110

2006.08.12 I

Po

siti

on

, arc

sec

Frequency, GHz

Pos C-A

Pos C-B

Pos B-A

6 8 10 12 14 16

-630

-610

-590

-570

-550

-530

2006.08.12I

Pos

ition

, arc

sec

Frequency, GHz

Pos A

Pos B

Pos C

10904

Angle of emission, teta

5Br

ight

ness

tem

pera

ture

, 10

K

17 GHz

2 GHz

20 40 60 80

0.2

0.4

0.6

0.8

1.0

17 GHz

2 GHz

Angle of emission, teta

Deg

ree o

f Pol

ariza

tion,

%

0.0

0.4

0.6

0.8

1.0

0.2

20 40 60 80

KTB610

3910 cmne cmLb

910

GB 2023

GB 238

2/)( oeB TTT )/()( oeoe TTTTV

))exp(1( bee LTT ))exp(1( boo LTT H 3

Low polarization, same size at different wavelengths, Flux decreases with frequency increases – mechanism of generation?

Cyclotron mechanism in quasi-transversal field at the top of magnetic loop

Fulfilled in the angle range 60o … 85o

Deg

ree

of p

olar

izat

ion,

%

Frequency, GHz7 8 9 10 11

1.0

0.5

0.5

1.0

0.0

Frequency, GHz6 7 8 9 10 11

0.5

0.6

0.7

Inte

nsity

, 10

W m

Hz

28

2

9102.0 y8

0 109R8104a

3110 102 cmN

cmhch8105.0

cmhc8100.1

KTch410KTc

610

5aT

GsB 9000 GsBth 1500

322 /1),(

dyh

ByhB th

2

222

00 exp(1

a

hyRTTT a

cc

cchchc

cchchc

chch

hhT

hhhhh

hhThhT

hhT

hT

,

,)()(

,

)(0

Bsff

,exp(1)()(

,105

exp105

exp

,105

exp

)(

2

222

02

330

30

a

hyRxNhNhN

hhT

hh

T

hN

hhT

hN

hN

aq

ac

a

ch

a

ach

q

Tor model of magnetic field

Several NLSs was observed in wide range of wavelengths. It allowed to estimate spectral indices of such kind of sources δNLS = 3 … 4 and maybe lower in some cases.

NLS placed at the top of magnetic loop.

Low polarization can be explained by cyclotron mechanism (thermal electrons) in the regions with angle between magnetic field and line of sight 60o … 85o.

Non-thermal electrons – possible not (sources are stable in few days, whilethermalization of electron distribution – tens of minutes).

Some spectral details (sudden change of polarization sign) can be explained by propagation through the hot areas (with typical sizes about 5 10∙ 7 cm).

Conclusions