Long-Period Oscillations of Sunspots by NoRH and SSRT Observations

Bakunina, I. A.; Abramov-Maximov, V. E.; Nakariakov, V. M.; Lesovoy, S. V.; Soloviev, A. A.; Tikhomirov, Yurii V.; Melnikov, V. F.; Shibasaki, Κ.; Nagovitsyn, Yu. A.; Averina, Elena L.

doi:10.1093/pasj/65.sp1.s13

Cited by 16 publications

(9 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Long-period magnetic field oscillations were detected from SOHO/MDI and ground-based data at Pulkovo Observatory by Nagovitsyna and Nagovitsyn (2002), Efremov et al (2007Efremov et al ( , 2009Efremov et al ( , 2012bEfremov et al ( , 2013, Kallunki and Riehokainen (2012), and with NoRH and SSRT instruments by AbramovMaximov et al (2013) and Bakunina et al (2013), finding periods of 30 -40, 70 -100, and 150 -200 and 800 -1300 minutes and amplitudes of about 200 G. Some of the authors suggest that these oscillations can be related to sunspot global eigen-modes as a whole. Efremov et al (2012a) have demonstrated that long-period ( = 10 -20 hours) oscillations of the magnetic field in bipolar groups are excited synchronously in the main and tail spots of a group.…”

Section: Long-period Oscillationsmentioning

confidence: 99%

Oscillations and Waves in Sunspots

Khomenko

Collados

2015

Living Rev. Sol. Phys.

157

118

View full text Add to dashboard Cite

A magnetic field modifies the properties of waves in a complex way. Significant advances have been made recently in our understanding of the physics of sunspot waves with the help of high-resolution observations, analytical theories, as well as numerical simulations. We review the current ideas in the field, providing the most coherent picture of sunspot oscillations as by present understanding. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

show abstract

Section: Long-period Oscillationsmentioning

confidence: 99%

Oscillations and Waves in Sunspots

Khomenko

Collados

2015

Living Rev. Sol. Phys.

157

118

View full text Add to dashboard Cite

show abstract

“…Yuan et al (2011) revealed the long-period waves of about 29, 53, and 75 min in the lower corona. Recently, Bakunina et al (2013) and Chorley et al (2010) reported on the long-period oscillations in radio band in sunspot magnetospheres.…”

Section: Introductionmentioning

confidence: 99%

Cut-off period for slow magnetoacoustic waves in coronal plasma structures

Afanasyev

Nakariakov

2015

A&A

View full text Add to dashboard Cite

Context. There is abundant observational evidence of longitudinal compressive waves in plasma structures of the solar corona, which are confidently interpreted in terms of slow magnetoacoustic waves. The uses of coronal slow waves in plasma diagnostics, as well as analysis of their possible contribution to coronal heating and the solar wind acceleration, require detailed theoretical modelling. Aims. We investigate the effects of obliqueness, magnetic field, and non-uniformity of the medium on the evolution of long-wavelength slow magnetoacoustic waves guided by field-aligned plasma non-uniformities, also called tube waves. Special attention is paid to the cut-off effect due to the gravity stratification of the coronal plasma. Methods. We study the behaviour of linear tube waves in a vertical untwisted straight field-aligned isothermal plasma cylinder. We apply the thin flux tube approximation, taking into account effects of stratification caused by gravity. The dispersion due to the finite radius of the flux tube is neglected. We analyse the behaviour of the cut-off period for an exponentially divergent magnetic flux tube filled in with a stratified plasma. The results obtained are compared with the known cases of the constant Alfven speed and the pure acoustic wave. Results. We derive the wave equation for tube waves and reduce it to the form of the Klein-Gordon equation with varying coefficients, which explicitly contains the cut-off frequency. The cut-off period is found to vary with height, decreasing significantly in the low-beta plasma and in the plasma with the beta of the order of unity. The depressions in the cut-off period profiles can affect the propagation of longitudinal waves along coronal plasma structures towards the higher corona and can form coronal resonators.

show abstract

“…Only pixels where periods between 600 s (the lower limit for long-period oscillations defined by Bakunina et al 2013) and 1272 s (the maximum value allowed by the cone-of-influence) are present were selected as potential candidates for study here. Overall, 233 pixels (13.3 %) display signals above the 99 % confidence level in the studied temporal range, with each of these pixels being denoted by a coloured cross on Fig.…”

Section: Wavelet Analysismentioning

confidence: 99%

“…The majority of oscillations reported in both sunspots and pores have periodicities of around 3 to 5 minutes, however, several important examples of long-period oscillations (> 10 minutes; Bakunina et al 2013) have also been identified. Freij et al (2016) observed oscillations in the areas and intensities of two pores with periods of up to 35 minutes.…”

Section: Introductionmentioning

confidence: 99%

Oscillations In The Line-of-Sight Magnetic Field Strength In A Pore Observed By The GREGOR Infrared Spectrograph (GRIS)

Nelson,

Campbell,

Mathioudakis

2021

Preprint

View full text Add to dashboard Cite

Context. 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. Aims. 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. Methods. A solar pore was observed on the 1st September 2019 using the GREGOR Infrared Spectrograph (GRIS) instrument for around one hour. Full-Stokes vectors were sampled in a 37 Å window containing the Fe i 15648.52 Å line (effective Landé g-factor of 3). The LOS magnetic field strength is inferred using the strong-field approximation (SFA). Additionally, the Stokes Inversion based on Response functions (SIR) code is used to gain a more complete understanding the physical properties of the solar atmosphere at the locations of these oscillations. Results. Oscillations of more than 100 G are observed in the LOS magnetic field in the period window between 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 logτ 5000 =−0.5 (potentially caused by compression) and other effects (e.g., changes in the optical depth or the inclination of the magnetic field) may account for these changes. Conclusions. The oscillations in the separations of the Stokes-V lobes of the 15648.52 Å 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.

show abstract

Long-Period Oscillations of Sunspots by NoRH and SSRT Observations

Cited by 16 publications

References 31 publications

Oscillations and Waves in Sunspots

Oscillations and Waves in Sunspots

Cut-off period for slow magnetoacoustic waves in coronal plasma structures

Oscillations In The Line-of-Sight Magnetic Field Strength In A Pore Observed By The GREGOR Infrared Spectrograph (GRIS)

Contact Info

Product

Resources

About