Inversions of Flaring Radio Emissions

.

Gregory D. Fleishman

Relevant Recent Discoveries

1.Pitch-angle anisotropy: - loop-top radio sources (NoRH)- variations of polarization (NoRH)- spectral variations (OVSA)

2.Dense flare environment - coronal loop HXR sources (RHESSI)- Razin effect in many radio bursts (OVSA)- resonant transition radiation in 10% of the bursts (OVSA)- cold dense flares (OVSA+ NoRH)

Implication for the radio burst modeling: take into account

1. For nonthermal electrons:- Anisotropic acceleration/injection, - Anisotropic transport effects, - Isotropisation due to collisions and wave-particle interactions,- Coronal losses of fast electrons

2.For emission generation and transport: - Free-free absorption- Razin suppression of the gyrosynchrotron emission- Source inhomogeneity- Other emission procersses (RTR, ECM…)

Simplfied model fittingSequence of fitted spectraDerived parameters vs time

Uniform, optically thin source with strong Razin-effect

24 October 2001

AR 9672

Almost No SXRs!Almost No SXRs!

1

2

3

4Images obtainedImages obtainedfor momentsfor moments1-41-4

17 GHz

35 GHz

9.4 GHz

NoRP light curves

1 2 3 4

NoRH images

17GHz

I

17GHz

V

34GHz

I

Klein’s GS approxi-mation for isotropic electron distribu-tion

10 March 2001

Exact GS formulae

4,6 4,8 5,0 5,2 5,48

10

12

14

16

18

20

22

Inte

nsity

, a.u

.

Frequency, GHz

Spikes Signal Fit

4,6 4,8 5,0 5,2 5,48

10

12

14

16

18

20

22

24

Inte

nsity, a.u

.

Frequency, GHz

Spikes Signal Fit

0,0 0,4 0,8 1,2 1,6 2,0 2,4 2,8 3,20

100

200

300

400

500

Num

ber

of s

pike

s

Bandwidth, %

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.20

100

200

300

400

500N

umbe

r of

spi

kes

Bandwidth, %

Turbulence parameter

a=2 * 10-7

202

0

a

e

CONCLUSIONSCONCLUSIONS

1.A number of recent discoveries calls for new, more detailed and sophisticated models of radio emission from solar flares.

2.Nonthermal radio emission depends not only on the magnetic field and energy distribution of fast electrons, but also on the pitch-angle anisotropy, background plasma density and temperature, source structure, and the turbulence level, thus, potentially it is a valuable source of information of the corresponding physical parameters and related processes.

3.The development of new reliable models and fitting algorithms is of primary importance and urgently needed to fully exploit the potential diagnostic capabilities of the planned project of a new solar dedicated radio instrument, Frequency Agile Solar Radiotelescope.