WISPR Imaging of a Pristine CME. (arXiv:1912.02255v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hess_P/0/1/0/all/0/1">Phillip Hess</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rouillard_A/0/1/0/all/0/1">Alexis Rouillard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kouloumvakos_A/0/1/0/all/0/1">Athanasios Kouloumvakos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liewer_P/0/1/0/all/0/1">Paulett C. Liewer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_J/0/1/0/all/0/1">Jie Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dhakal_S/0/1/0/all/0/1">Suman Dhakal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stenborg_G/0/1/0/all/0/1">Guillermo Stenborg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Colaninno_R/0/1/0/all/0/1">Robin C. Colaninno</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howard_R/0/1/0/all/0/1">Russell A. Howard</a>

The Wide-field Imager for Solar Probe (WISPR) on board the Parker Solar Probe
(PSP) observed a CME on 2018 November 01, the first day of the initial PSP
encounter. The speed of the CME, approximately 200-300 km s$^{-1}$ in the WISPR
field of view, is typical of slow, streamer blowout CMEs. This event was also
observed by the LASCO coronagraphs. WISPR and LASCO view remarkably similar
structures that enable useful cross-comparison between the two data sets as
well as stereoscopic imaging of the CME. Analysis is extended to lower heights
by linking the white-light observations to EUV data from AIA, which reveal a
structure that erupts more than a full day earlier before the CME finally
gathers enough velocity to propagate outward. This EUV feature appears as a
brightness enhancement in cooler temperatures such as 171 AA, but as a cavity
in nominal coronal temperatures such as 193 AA. By comparing this circular,
dark feature in 193 AA to the dark, white-light cavity at the center of the
eruption in WISPR and LASCO, it can be seen that this is one coherent structure
that exists prior to the eruption in the low corona before entering the
heliosphere and likely corresponds to the core of the magnetic flux rope. It is
also believed that the relative weakness of the event contributed to the
clarity of the flux rope in WISPR, as the CME did not experience impulsive
forces or strong interaction with external structures that can lead to more
complex structural evolution.

The Wide-field Imager for Solar Probe (WISPR) on board the Parker Solar Probe
(PSP) observed a CME on 2018 November 01, the first day of the initial PSP
encounter. The speed of the CME, approximately 200-300 km s$^{-1}$ in the WISPR
field of view, is typical of slow, streamer blowout CMEs. This event was also
observed by the LASCO coronagraphs. WISPR and LASCO view remarkably similar
structures that enable useful cross-comparison between the two data sets as
well as stereoscopic imaging of the CME. Analysis is extended to lower heights
by linking the white-light observations to EUV data from AIA, which reveal a
structure that erupts more than a full day earlier before the CME finally
gathers enough velocity to propagate outward. This EUV feature appears as a
brightness enhancement in cooler temperatures such as 171 AA, but as a cavity
in nominal coronal temperatures such as 193 AA. By comparing this circular,
dark feature in 193 AA to the dark, white-light cavity at the center of the
eruption in WISPR and LASCO, it can be seen that this is one coherent structure
that exists prior to the eruption in the low corona before entering the
heliosphere and likely corresponds to the core of the magnetic flux rope. It is
also believed that the relative weakness of the event contributed to the
clarity of the flux rope in WISPR, as the CME did not experience impulsive
forces or strong interaction with external structures that can lead to more
complex structural evolution.

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