3 research outputs found
Solar-Cycle Variation of quiet-Sun Magnetism and Surface Gravity Oscillation Mode
The origin of the quiet Sun magnetism is under debate. Investigating the
solar cycle variation observationally in more detail can give us clues about
how to resolve the controversies. We investigate the solar cycle variation of
the most magnetically quiet regions and their surface gravity oscillation
(-) mode integrated energy (). We use 12 years of HMI data and apply a
stringent selection criteria, based on spatial and temporal quietness, to avoid
any influence of active regions (ARs). We develop an automated high-throughput
pipeline to go through all available magnetogram data and to compute for
the selected quiet regions. We observe a clear solar cycle dependence of the
magnetic field strength in the most quiet regions containing several
supergranular cells. For patch sizes smaller than a supergranular cell, no
significant cycle dependence is detected. The at the supergranular scale
is not constant over time. During the late ascending phase of Cycle 24 (SC24,
2011-2012), it is roughly constant, but starts diminishing in 2013, as the
maximum of SC24 is approached. This trend continues until mid-2017, when hints
of strengthening at higher southern latitudes are seen. Slow strengthening
continues, stronger at higher latitudes than at the equatorial regions, but
never returns back to the values seen in 2011-2012. Also, the
strengthening trend continues past the solar minimum, to the years when SC25 is
already clearly ascending. Hence the behavior is not in phase with the
solar cycle. The anticorrelation of with the solar cycle in gross terms
is expected, but the phase shift of several years indicates a connection to the
poloidal large-scale magnetic field component rather than the toroidal one.
Calibrating AR signals with the QS does not reveal significant
enhancement of the -mode prior to AR emergence.Comment: 10 pages, 11 figures, submitted to Astronomy & Astrophysic
Magnetic fields inferred by Solar Orbiter: A comparison between SO/PHI-HRT and SDO/HMI
Context. The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager on board the Solar Orbiter spacecraft (SO/PHI) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) both infer the photospheric magnetic field from polarised light images. SO/PHI is the first magnetograph to move out of the Sun–Earth line and will provide unprecedented access to the Sun’s poles. This provides excellent opportunities for new research wherein the magnetic field maps from both instruments are used simultaneously.
Aims. We aim to compare the magnetic field maps from these two instruments and discuss any possible differences between them.
Methods. We used data from both instruments obtained during Solar Orbiter’s inferior conjunction on 7 March 2022. The HRT data were additionally treated for geometric distortion and degraded to the same resolution as HMI. The HMI data were re-projected to correct for the 3° separation between the two observatories.
Results. SO/PHI-HRT and HMI produce remarkably similar line-of-sight magnetograms, with a slope coefficient of 0.97, an offset below 1 G, and a Pearson correlation coefficient of 0.97. However, SO/PHI-HRT infers weaker line-of-sight fields for the strongest fields. As for the vector magnetic field, SO/PHI-HRT was compared to both the 720-second and 90-second HMI vector magnetic field: SO/PHI-HRT has a closer alignment with the 90-second HMI vector. In the weak signal regime (< 600 G), SO/PHI-HRT measures stronger and more horizontal fields than HMI, very likely due to the greater noise in the SO/PHI-HRT data. In the strong field regime (≳600 G), HRT infers lower field strengths but with similar inclinations (a slope of 0.92) and azimuths (a slope of 1.02). The slope values are from the comparison with the HMI 90-second vector. Possible reasons for the differences found between SO/PHI-HRT and HMI magnetic field parameters are discussed.Sección Deptal. de Óptica (Óptica)Fac. de Óptica y OptometríaTRUEBMWi - Bundesministerium für Wirtschaft und Energie (Alemania)AEI/MCIN/10.13039/501100011033Ministerio de ciencia e innovación de EspañaInstituto Astrofísico de Andalucía (España)Agencia Estatal de Investigación (España)Fondo Europeo de Desarrollo Regional (Fondos FEDER)Centre national d'études spatiales (CNES) (Francia)CSIC (Centro Superior de Investigaciones Científicas) (España)pu
Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere
This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere