First Frequency-Time-Resolved Imaging Spectroscopy Observations of Solar Radio Spikes. (arXiv:2108.06191v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Clarkson_D/0/1/0/all/0/1">Daniel L. Clarkson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kontar_E/0/1/0/all/0/1">Eduard P. Kontar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gordovskyy_M/0/1/0/all/0/1">Mykola Gordovskyy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chrysaphi_N/0/1/0/all/0/1">Nicolina Chrysaphi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vilmer_N/0/1/0/all/0/1">Nicole Vilmer</a>
Solar radio spikes are short duration and narrow bandwidth fine structures in
dynamic spectra observed from GHz to tens of MHz range. Their very short
duration and narrow frequency bandwidth are indicative of sub-second
small-scale energy release in the solar corona, yet their origin is not
understood. Using the LOw Frequency ARray (LOFAR), we present spatially,
frequency and time resolved observations of individual radio spikes associated
with a coronal mass ejection (CME). Individual radio spike imaging demonstrates
that the observed area is increasing in time and the centroid positions of the
individual spikes move superluminally parallel to the solar limb. Comparison of
spike characteristics with that of individual Type IIIb striae observed in the
same event show similarities in duration, bandwidth, drift rate, polarization
and observed area, as well the spike and striae motion in the image plane
suggesting fundamental plasma emission with the spike emission region on the
order of ${sim}:10^8$ cm, with brightness temperature as high as $10^{13}$ K.
The observed spatial, spectral, and temporal properties of the individual spike
bursts are also suggesting the radiation responsible for spikes escapes through
anisotropic density turbulence in closed loop structures with scattering
preferentially along the guiding magnetic field oriented parallel to the limb
in the scattering region. The dominance of scattering on the observed time
profile suggests the energy release time is likely to be shorter than what is
often assumed. The observations also imply that the density turbulence
anisotropy along closed magnetic field lines is higher than along open field
lines.
Solar radio spikes are short duration and narrow bandwidth fine structures in
dynamic spectra observed from GHz to tens of MHz range. Their very short
duration and narrow frequency bandwidth are indicative of sub-second
small-scale energy release in the solar corona, yet their origin is not
understood. Using the LOw Frequency ARray (LOFAR), we present spatially,
frequency and time resolved observations of individual radio spikes associated
with a coronal mass ejection (CME). Individual radio spike imaging demonstrates
that the observed area is increasing in time and the centroid positions of the
individual spikes move superluminally parallel to the solar limb. Comparison of
spike characteristics with that of individual Type IIIb striae observed in the
same event show similarities in duration, bandwidth, drift rate, polarization
and observed area, as well the spike and striae motion in the image plane
suggesting fundamental plasma emission with the spike emission region on the
order of ${sim}:10^8$ cm, with brightness temperature as high as $10^{13}$ K.
The observed spatial, spectral, and temporal properties of the individual spike
bursts are also suggesting the radiation responsible for spikes escapes through
anisotropic density turbulence in closed loop structures with scattering
preferentially along the guiding magnetic field oriented parallel to the limb
in the scattering region. The dominance of scattering on the observed time
profile suggests the energy release time is likely to be shorter than what is
often assumed. The observations also imply that the density turbulence
anisotropy along closed magnetic field lines is higher than along open field
lines.
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