Spectral peculiarities of microwave solar radio bursts millimeter part

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Spectral peculiarities of microwave solar radio
bursts millimeter part
Valery NAGNIBEDA, Viktoria SMIRNOVA, Maria
LOUKITCHEVA Astronomical Institute,
Saint-Petersburg State University
(Russia) vvsvid_at_rambler.ru vnag_at_VN1014.spb.edu

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The standard model of the solar microwave burst
spectrum

• Spectral maximum lays about 5-10 Ghz.
• But
• In some events flux density rising with frequency
  to millimeter band and spectral hardening from
  about 12 Ghz is detected. (L. M. Chertok et al.
  1995 Kundu et al. 2000, Nindos 2004)

(M.Kundu, L.Vlahos, 1982)
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(I.M.Chertok et al., 1995)
Ideally, one wants to model both the observed
radio flux and structures as a function of time
(Nindos, 2004) There is no simple interpretation
those spectra peculiarities. However, the fine
correlation between standard microwave bursts
and SXR, and bursts with increased millimeter
part with HXR emission is established.
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In this work the attempt to study more detailed
the burst dynamical properties with spectrum and
time characteristics was made, paying attention
to spectrum millimeter part.

• 04 June 2007 flare data
• NoRH (17 and 34 GHz maps)
• NoRP (1, 2, 3.75, 9.4, 17, 35, 80 GHz time
  profiles)
• TRACE (171 Å, 195 Å, WL)
• SOHO (MDI Magnetograms)
• RHESSI (6-12 kev)
• Goes class M 8.9
• AR NOAA 10960

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Spots (top right) and bursts location on the SOHO
magnetograms
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Flux density dynamic spectrum for frequencies 1,
2, 3.75, 9.4, 17, 35 and 80 GHz
The noticeable frequency drift of the maximum
toward short waves is detected. It is possible to
suppose that the drift of the maximum to
high-frequencies can be related with the
millimeter emission strengthening, that reflects
the appearance of more energetic electrons at the
moments of the energy release in the source.
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Time profiles 17 (white), 35 (red), 80 GHz
(yellow). Time variations of the burst
spectrum for different spikes.
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The five general spikes were chosen to create the
spectral curves. The spectrum millimeter part is
changing with time, where the spikes appear. The
millimeter emission appearance has weak influence
on a long wavelength spectrum part, that is
possibly related with the additional injection
of high-energy electrons.
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Contours of 17 and 34 GHz radio bursts maps
superposed on the TRACE time corresponding image.
Bursts generation areas are distinctly spaced
(within the limits of 10 arcsec.)
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The contours of 17, 34 GHz and HXR 6-12 keV burst
sources were obtained from maps were synthesized
from the NoRH and RHESSI data archives for the
same moment of time. The contours are plotted on
TRACE 171 Å image. The burst source locations
were obtained for the five moments of time when
the spikes in the time profiles appear. The
maximum bright source points were plotted on the
SOHO magnetogram. The impulsive burst source
locations is misalign in different frequency
ranges.
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Conclusions

• The millimeter emission appearance has weak
  influence on a long wavelength spectrum part,
  that is possibly related with the additional
  injection of high-energy electrons.
• The impulsive burst source locations is misalign
  in different frequency ranges.