Photospheric Observations of Surface and Body Modes in Solar Magnetic Pores

Zhang

Monthly Notices of the Royal Astronomical Society

et al. 2019

Temporal variation of the solar coronal rotation appears to be very complex and its relevances to the eleven-year solar activity cycle are still unclear. Using the modified coronal index for the time interval from 1939 January 1 to 2019 May 31, the systematic regularities of the solar coronal rotation are investigated. Our main findings are as follows: (1) from a global point of view, the synodic coronal rotation period with a value of 27.5 days is the only significant period at the periodic scales shorter than 64 days; (2) the coronal rotation period exhibit an obviously decreasing trend during the considered time interval, implying the solar corona accelerates its global rotation rate in the long run; (3) there exist significant periods of 3.25, 6.13, 9.53, and 11.13 years in the period length of the coronal rotation, providing an evidence that the coronal rotation should be connected with the quasi-biennial oscillation, the eleven-year solar cycle, and the 22-year Hale cycle (or the magnetic activity reversal); and (4) the phase relationship between the coronal rotation period and the solar magnetic activity is not only time-dependent but also frequency-dependent. For a small range around the 11-year cycle band, there is a systematic trend in the phase, and the small mismatch in this band brings out the phase to drift. The possible mechanism for the above analysis results is discussed.

Section: Phase Relationship Between Coronal Rotation and Solar Activitymentioning

confidence: 99%

Systematic regularity of solar coronal rotation during the time interval 1939–2019

Zhang

Monthly Notices of the Royal Astronomical Society

et al. 2019

Phil. Trans. R. Soc. A.

“…A large variety of different magnetohydrodynamic (MHD) wave modes are theoretically predicted, and indeed observed, in solar magnetic structures ranging from large sunspots extending over several Mm, down to very small magnetic elements at the limit of spatial resolution on current solar telescopes [1][2][3][4][5][6][7][8][9][10]. Magnetic fields connect different heights in the solar atmosphere, thus MHD waves propagating along them [11] can play a major role in supplying the energy budget to the upper layers of the solar atmosphere [12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Spectropolarimetric fluctuations in a sunspot chromosphere

Stangalini

Baker

Valori

et al. 2020

Self Cite

The instrumental advances made in this new era of 4 m class solar telescopes with unmatched spectropolarimetric accuracy and sensitivity will enable the study of chromospheric magnetic fields and their dynamics with unprecedented detail. In this regard, spectropolarimetric diagnostics can provide invaluable insight into magneto-hydrodynamic (MHD) wave processes. MHD waves and, in particular, Alfvénic fluctuations associated with particular wave modes were recently recognized as important mechanisms not only for the heating of the outer layers of the Sun’s atmosphere and the acceleration of the solar wind, but also for the elemental abundance anomaly observed in the corona of the Sun and other Sun-like stars (also known as first ionization potential) effect. Here, we take advantage of state-of-the-art and unique spectropolarimetric Interferometric BIdimensional Spectrometer observations to investigate the relation between intensity and circular polarization (CP) fluctuations in a sunspot chromosphere. Our results show a clear link between the intensity and CP fluctuations in a patch which corresponds to a narrow range of magnetic field inclinations. This suggests the presence of Alfvénic perturbations in the sunspot. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

Phil. Trans. R. Soc. A.

“…This can add complexity in the interpretation of sausage modes when the cross section of the oscillator may vary periodically and with height [45][46][47]. The natural evolution of smallscale magnetic elements such as magnetic bright points (MBPs; [30,32]) can further complicate the interpretation of wave signals in spectropolarimetric data as fluctuations can result from the natural evolution of these features as opposed to the propagation of waves.…”

Section: Introductionmentioning

confidence: 99%

On the effect of oscillatory phenomena on Stokes inversion results

Keys

Steiner

Vigeesh

2020

Self Cite

Stokes inversion codes are crucial in returning properties of the solar atmosphere, such as temperature and magnetic field strength. However, the success of such algorithms to return reliable values can be hindered by the presence of oscillatory phenomena within magnetic wave guides. Returning accurate parameters is crucial to both magnetohydrodynamics (MHD) studies and solar physics in general. Here, we employ a simulation featuring propagating MHD waves within a flux tube with a known driver and atmospheric parameters. We invert the Stokes profiles for the 6301 Å and 6302 Å line pair emergent from the simulations using the well-known Stokes Inversions from Response functions code to see if the atmospheric parameters can be returned for typical spatial resolutions at ground-based observatories. The inversions return synthetic spectra comparable to the original input spectra, even with asymmetries introduced in the spectra from wave propagation in the atmosphere. The output models from the inversions match closely to the simulations in temperature, line-of-sight magnetic field and line-of-sight velocity within typical formation heights of the inverted lines. Deviations from the simulations are seen away from these height regions. The inversions results are less accurate during passage of the waves within the line formation region. The original wave period could be recovered from the atmosphere output by the inversions, with empirical mode decomposition performing better than the wavelet approach in this task. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.