Cut-off features in interplanetary solar radio type IV emission. (arXiv:1906.07534v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pohjolainen_S/0/1/0/all/0/1">Silja Pohjolainen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sheshvan_N/0/1/0/all/0/1">Nasrin Talebpour Sheshvan</a>
Solar radio type IV bursts can sometimes show directivity, so that no burst
is observed when the source region in located far from the solar disk center.
This has recently been verified also from space observations, at decameter
wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is
unclear whether the directivity is caused by the emission mechanism, by reduced
radio wave formation toward certain directions, or by absorption/blocking of
radio waves along the line of sight. We present here observations of three type
IV burst events that occurred on 23, 25, and 29 July 2004, and originated from
the same active region. The source location of the first event was near the
solar disk center and in the third event near the west limb. Our analysis shows
that in the last two events the type IV bursts experienced partial cut-offs in
their emission, that coincided with the appearance of shock-related type II
bursts. The type II bursts were formed at the flanks and leading fronts of
propagating coronal mass ejections (CMEs). These events support the suggestion
of absorption toward directions where the type II shock regions are located.
Solar radio type IV bursts can sometimes show directivity, so that no burst
is observed when the source region in located far from the solar disk center.
This has recently been verified also from space observations, at decameter
wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is
unclear whether the directivity is caused by the emission mechanism, by reduced
radio wave formation toward certain directions, or by absorption/blocking of
radio waves along the line of sight. We present here observations of three type
IV burst events that occurred on 23, 25, and 29 July 2004, and originated from
the same active region. The source location of the first event was near the
solar disk center and in the third event near the west limb. Our analysis shows
that in the last two events the type IV bursts experienced partial cut-offs in
their emission, that coincided with the appearance of shock-related type II
bursts. The type II bursts were formed at the flanks and leading fronts of
propagating coronal mass ejections (CMEs). These events support the suggestion
of absorption toward directions where the type II shock regions are located.
http://arxiv.org/icons/sfx.gif
