Oscillations In The Line-of-Sight Magnetic Field Strength In A Pore Observed By The GREGOR Infrared Spectrograph (GRIS). (arXiv:2107.10183v1 [astro-ph.SR])

Oscillations In The Line-of-Sight Magnetic Field Strength In A Pore Observed By The GREGOR Infrared Spectrograph (GRIS). (arXiv:2107.10183v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Nelson_C/0/1/0/all/0/1">C. J. Nelson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Campbell_R/0/1/0/all/0/1">R. J. Campbell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mathioudakis_M/0/1/0/all/0/1">M. Mathioudakis</a>

Numerous magnetohydrodynamic oscillations have been reported within solar
pores over the past decades, including in line-of-sight (LOS) velocities,
intensities, and magnetic field strengths. Our aim is to identify whether
high-amplitude oscillations in the LOS magnetic field strength can be detected
within a pore located in Active Region 12748 and to investigate which physical
mechanisms could be responsible for them. A solar pore was observed on the 1st
September 2019 using the GREGOR Infrared Spectrograph for around one hour.
Full-Stokes vectors were sampled in a 37 A window containing the Fe I 15648.52
A line (effective Lande g-factor of 3). The LOS magnetic field strength is
inferred using the strong-field approximation. The Stokes Inversion based on
Response functions code is used to gain a more complete understanding the
properties of the solar atmosphere at the locations of these oscillations.
Oscillations of more than 100 G are observed in the LOS magnetic field in the
period window 600-1272 s at three localised (>1″^2) regions. These oscillations
have coherence across individual regions indicating that jitter cannot account
for their occurrence. Longer-period amplitude variations, amplitudes over 200
G, are also detected but these have periods outside of the cone-of-influence.
Numerical inversions confirm both oscillations in the LOS magnetic field
strength at optical depths of around log-tau_5000=-0.5 (potentially caused by
compression) and other effects (e.g., changes in the optical depth or the
inclination of the field) may account for these changes. The oscillations in
the separations of the Stokes-V lobes of the 15648.52 A line appear to be solar
in nature. Future work will be required to understand whether these are truly
oscillations in the magnetic field strength at a specific depth in the solar
atmosphere or whether other effects are responsible for these signatures.

Numerous magnetohydrodynamic oscillations have been reported within solar
pores over the past decades, including in line-of-sight (LOS) velocities,
intensities, and magnetic field strengths. Our aim is to identify whether
high-amplitude oscillations in the LOS magnetic field strength can be detected
within a pore located in Active Region 12748 and to investigate which physical
mechanisms could be responsible for them. A solar pore was observed on the 1st
September 2019 using the GREGOR Infrared Spectrograph for around one hour.
Full-Stokes vectors were sampled in a 37 A window containing the Fe I 15648.52
A line (effective Lande g-factor of 3). The LOS magnetic field strength is
inferred using the strong-field approximation. The Stokes Inversion based on
Response functions code is used to gain a more complete understanding the
properties of the solar atmosphere at the locations of these oscillations.
Oscillations of more than 100 G are observed in the LOS magnetic field in the
period window 600-1272 s at three localised (>1″^2) regions. These oscillations
have coherence across individual regions indicating that jitter cannot account
for their occurrence. Longer-period amplitude variations, amplitudes over 200
G, are also detected but these have periods outside of the cone-of-influence.
Numerical inversions confirm both oscillations in the LOS magnetic field
strength at optical depths of around log-tau_5000=-0.5 (potentially caused by
compression) and other effects (e.g., changes in the optical depth or the
inclination of the field) may account for these changes. The oscillations in
the separations of the Stokes-V lobes of the 15648.52 A line appear to be solar
in nature. Future work will be required to understand whether these are truly
oscillations in the magnetic field strength at a specific depth in the solar
atmosphere or whether other effects are responsible for these signatures.

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