E-Print Archive

There are 3914 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Height distribution of the power of 3-min oscillations over sunspots  

Nikolai Kobanov   Submitted: 2011-12-05 23:47

Context. The height structure of 3-min oscillations over sunspots is studiedin the context of the recently discovered effect of height inversion: over theumbra, the spatial location of the maximum of chromospheric 3-min oscillationpower corresponds to the relative decrease in the power of photosphericoscillations. Aims. We investigate whether the height inversion of the power of3-min oscillations is a common feature of the spatial structure of theoscillations for the majority of sunspots. Methods. Spectrogram sequences ofHα 6563{AA} and FeI 6569{AA} over sunspots, acquired with very highcadency (about 2 s or better) are obtained. The distribution of the oscillationpower of the line-of-sight velocity signal is studied by using methods ofwavelet frequency filtration and Fourier analysis. Results. The effect of theheight inversion is found in 9 of 11 analyzed active regions. Theinterpretation of this effect is possibly connected to both the decrease in thelevel of photosphere in sunspot umbrae and the magnetic field topology.

Authors: N. I. Kobanov, D. Y. Kolobov, S. A. Chupin and V. M. Nakariakov
Projects: None

Publication Status: Published, A&A, 525, A41 (2011), DOI:10.1051/0004-6361/200913533
Last Modified: 2011-12-07 12:13
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Oscillations in the Solar Faculae. III. The Phase Relations between Chromospheric and Photospheric LOS Velocities  

Nikolai Kobanov   Submitted: 2011-11-29 18:25

An analysis of line-of-sight velocity oscillation in nine solar faculae wasundertaken with the aim of studying of phase relations between chromosphere (Hei 10830 Å line) and photosphere (Si i 10827 A line) five-minute oscillations.We found that time lag of the chromospheric signal relative to photospheric onevaries from -12 to 100 seconds and is about 50 seconds on average.We assumethat the small observed lag can have three possible explanations: i)convergence of formation levels of He i 10830 Å and Si i 10827 A in faculae;ii) significant increase of five-minute oscillation propagation velocity abovefaculae; iii) simultaneous presence of standing and travelling waves.

Authors: N.I.Kobanov, A.S.Kustov, S.A.Chupin, V.A.Pulyaev
Projects: None

Publication Status: In press, Solar Phys (2011) 273:39?49
Last Modified: 2011-11-30 08:15
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Spatial Distribution of Oscillations in Faculae  

Nikolai Kobanov   Submitted: 2011-11-29 18:17

We found that oscillations of LOS velocity in Hα are different forvarious parts of faculae regions. Power spectra show that the contribution oflow-frequency modes (1.2 - 2 mHz) increase at the network boundaries. Three andfive- minute periods dominate inside cells. The spectra of photosphere andchromosphere LOS velocity oscillations differ for most faculae. On the otherhand, we detected several cases where propagating oscillations in faculae weremanifest with a five-minute period. Their initiation point on spatial-temporaldiagrams coincided with the local maximum of the longitudinal magnetic field.

Authors: N.I.Kobanov, V.A.Pulyaev
Projects: None

Publication Status: Published, Solar Phys (2011) 268: 329?334, DOI: 10.1007/s11207-010-9581-9
Last Modified: 2011-11-30 08:16
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Traveling Waves in the Sunspot Chromosphere: Problems and Puzzles of Experiments;  

Nikolai Kobanov   Submitted: 2008-06-06 03:20

The problems of observations and interpretation of wave processes observed in sunspot chromosphere are discussed. We show that frequency filtration provides effective method to reveal travelling waves which finally affects the objectivity of estimation of parameters under nvestigation. The measured magnitudes of horizontal phase velocity are 40-70 km s-1 in umbra, and 30-70 km s-1 in penumbra. The altitude inversion of spatial location of three-minute oscillation power was found by analysis of observations with high cadence. It should be noticed that the pattern of umbral travelling wave is not constant and is often transformed to the pattern of standing wave.

Authors: N.I. Kobanov, D.Y. Kolobov, and S.A. Chupin
Projects: None

Publication Status: published
Last Modified: 2008-09-23 21:00
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Nikolai Kobanov   Submitted: 2008-02-07 05:27

We present the results of investigations into chromospheric velocity oscillations in sunspots, carried out at the Sayan Solar Observatory. It is shown that the "chevron" structures in the halftone diagrams demonstrate wavetrain properties. Such structures are indicators of a propagating wave process and they are typical of many sunspots. In the authors? opinion, three-minute umbral oscillations are not the source of running penumbral waves (RPW). It is very likely that umbral oscillations and RPW initially propagate along different magnetic field lines. We explain the decrease in RPW propagation velocity and frequency in the outer penumbra, as compared with the inner, by the combined action of different frequency modes. To better reveal the properties of these modes frequency filtering was used. Our measurements of the RPW (five-minute mode) wavelength and RPW propagation velocity in different sunspots vary from 12'' to 30'' and from 28 to 60 ? 70 km s-1 correspondingly.

Authors: N. I. Kobanov, D. Y. Kolobov and D. V. Makarchik
Projects: None

Publication Status: Solar Physics, 2006, V.238, 231-244
Last Modified: 2008-02-07 07:47
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Nikolai Kobanov   Submitted: 2008-02-07 05:27

We present the results of investigations into chromospheric velocity oscillations in sunspots, carried out at the Sayan Solar Observatory. It is shown that the ''chevron'' structures in the halftone diagrams demonstrate wavetrain properties. Such structures are indicators of a propagating wave process and they are typical of many sunspots. In the authors' opinion, three-minute umbral oscillations are not the source of running penumbral waves (RPW). It is very likely that umbral oscillations and RPW initially propagate along different magnetic field lines. We explain the decrease in RPW propagation velocity and frequency in the outer penumbra, as compared with the inner, by the combined action of different frequency modes. To better reveal the properties of these modes frequency filtering was used. Our measurements of the RPW (five-minute mode) wavelength and RPW propagation velocity in different sunspots vary from 12'' to 30'' and from 28 to 60-70 km s-1 correspondingly.

Authors: N. I. Kobanov, D. Y. Kolobov and D. V. Makarchik
Projects:

Publication Status: Solar Physics, 2006, V.238, 231-244
Last Modified: 2008-02-07 09:30
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Nikolai Kobanov   Submitted: 2008-02-07 05:18

The differences between physical conditions in solar faculae and those in sunspots and quiet photosphere (increased temperature and different topology of magnetic field) suggest that oscillation characteristics in facula areas also have different properties. The analysis of 28 time sets of simultaneous spectropolarimetric observations in facula photosphere (FeI 6569A, 8538A) and chromosphere (Hα , CaII 8542A) yields the following results. The amplitude of five-minute oscillations of line-of-sight (LOS) velocity decreases by 20-40 percent in facula photosphere. There are only some cases revealing the inverse effect. The amplitude of four-five minute LOS velocity oscillations increases significantly in the chromosphere above faculae, and power spectra fairly often show pronounced peaks in a frequency range of 1.3-2.5 mHz. Evidence of propagating oscillations can be seen from space-time diagrams. We have found oscillations of the longitudinal magnetic field (1.5-2 mHz and 5.2 mHz) inside faculae.

Authors: N. I. Kobanov and V. A. Pulyaev
Projects: None

Publication Status: Solar Physics, V.246, 273-279, 2007
Last Modified: 2008-02-07 07:47
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Nikolai Kobanov   Submitted: 2008-02-07 05:17

Episodic observations of coronal holes were carried out simultaneously in several spectral lines during the 2002-2005 observational seasons. An analysis of eighteen time series is used to obtain the amplitude?spectral properties of oscillatory wave motions of the solar plasma at the bases of coronal holes. It is found that the amplitudes of the 5-min and 3-min line-of-sight velocity oscillations increase in coronal holes. Low-frequency (1?2 mHz) oscillations are concentrated at the boundaries of the chromospheric network, while the 3-mHz and 5-mHz oscillations dominate in the network cells. Clear indications of propagating waves have been found at the bases of coronal holes. The 3 mHz phase velocities are 45?5 km s-1 and 80x100 km s-1 for the equatorial and polar coronal holes, respectively.

Authors: N. I. Kobanov and A. A. Sklyar
Projects: None

Publication Status: Astronomy Reports, 2007, Vol. 51, No. 9, pp. 773?779.
Last Modified: 2008-02-07 05:17
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Nikolai Kobanov   Submitted: 2008-02-07 05:17

Episodic observations of coronal holes were carried out simultaneously in several spectral lines during the 2002-2005 observational seasons. An analysis of eighteen time series is used to obtain the amplitude-spectral properties of oscillatory wave motions of the solar plasma at the bases of coronal holes. It is found that the amplitudes of the 5-min and 3-min line-of-sight velocity oscillations increase in coronal holes. Low-frequency (1-2 mHz) oscillations are concentrated at the boundaries of the chromospheric network, while the 3-mHz and 5-mHz oscillations dominate in the network cells. Clear indications of propagating waves have been found at the bases of coronal holes. The 3 mHz phase velocities are 45±5 km s-1 and 80-100 km s-1 for the equatorial and polar coronal holes, respectively.

Authors: N. I. Kobanov and A. A. Sklyar
Projects:

Publication Status: Astronomy Reports, 2007, Vol. 51, No. 9, pp. 773-779.
Last Modified: 2008-02-08 07:36
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Height distribution of the power of 3-min oscillations over sunspots
Oscillations in the Solar Faculae. III. The Phase Relations between Chromospheric and Photospheric LOS Velocities
Spatial Distribution of Oscillations in Faculae
Traveling Waves in the Sunspot Chromosphere: Problems and Puzzles of Experiments;
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University