Date post: | 21-Dec-2015 |
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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
1
2
3
4Images obtainedImages obtainedfor momentsfor moments1-41-4
17 GHz
35 GHz
9.4 GHz
NoRP light curves
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.