Influence of Heliolatitudinal Anisotropy of Solar FUV/EUV Emissions on Lyman-alpha Helioglow: SOHO/SWAN Observations and WawHelioGlow Modeling. (arXiv:2109.08095v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Strumik_M/0/1/0/all/0/1">Marek Strumik</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bzowski_M/0/1/0/all/0/1">Maciej Bzowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kubiak_M/0/1/0/all/0/1">Marzena A. Kubiak</a>
Observations of the Sun’s surface suggest a nonuniform radiated flux as
related to the presence of bright active regions and darker coronal holes. The
variations of the FUV/EUV source radiation can be expected to affect the
Lyman-alpha backscatter glow measured by spaceborne instruments. In particular,
inferring the heliolatitudinal structure of the solar wind from helioglow
variations in the sky can be quite challenging if the heliolatitudinal
structure of the solar FUV/EUV radiation is not properly included in the
modeling of the heliospheric glow. We present results of analysis of the
heliolatitudinal structure of the solar Lyman-alpha radiation as inferred from
comparison of SOHO/SWAN satellite observations of the helioglow intensity with
modeling results obtained from the recently-developed WawHelioGlow model. We
find that in addition to time-dependent heliolatitudinal anisotropy of the
solar wind, also time-dependent heliolatitudinal variations of the intensity of
the solar Lyman-alpha and photoionizing emissions must be taken into account to
reproduce the observed helioglow modulation in the sky. We present a particular
latitudinal and temporal dependence of the solar Lyman-alpha flux obtained as a
result of our analysis. We analyze also differences between polar-equatorial
anisotropies close to the solar surface and seen by an observer located far
from the Sun. We discuss the implications of these findings for the
interpretation of heliospheric-glow observations.
Observations of the Sun’s surface suggest a nonuniform radiated flux as
related to the presence of bright active regions and darker coronal holes. The
variations of the FUV/EUV source radiation can be expected to affect the
Lyman-alpha backscatter glow measured by spaceborne instruments. In particular,
inferring the heliolatitudinal structure of the solar wind from helioglow
variations in the sky can be quite challenging if the heliolatitudinal
structure of the solar FUV/EUV radiation is not properly included in the
modeling of the heliospheric glow. We present results of analysis of the
heliolatitudinal structure of the solar Lyman-alpha radiation as inferred from
comparison of SOHO/SWAN satellite observations of the helioglow intensity with
modeling results obtained from the recently-developed WawHelioGlow model. We
find that in addition to time-dependent heliolatitudinal anisotropy of the
solar wind, also time-dependent heliolatitudinal variations of the intensity of
the solar Lyman-alpha and photoionizing emissions must be taken into account to
reproduce the observed helioglow modulation in the sky. We present a particular
latitudinal and temporal dependence of the solar Lyman-alpha flux obtained as a
result of our analysis. We analyze also differences between polar-equatorial
anisotropies close to the solar surface and seen by an observer located far
from the Sun. We discuss the implications of these findings for the
interpretation of heliospheric-glow observations.
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