Sunspot plume observations in the EUV

Doyle, J. G.; Madjarska, M. S.

doi:10.1051/0004-6361:20031057

Cited by 13 publications

(12 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The derived density in the sunspot plume here is consistent with those derived by Doyle et al (1985) and Doyle & Madjarska (2003). In Doyle et al (1985), the authors used the ratio of O v 760 Å/630 Å obtained by the S-055 EUV spectrometer onboard Skylab and derived a density of log(N e /cm −3 ) = 10.…”

Section: Electron Densitiessupporting

confidence: 85%

“…This hypothesis seems to be supported by the observational result of Brosius (2005), in which a significantly higher density (log(N e /cm −3 ) = 9.8, compared to log(N e /cm −3 ) = 8.9 in the plume, in an upflow region outside the sunspot was observed by CDS. Doyle & Madjarska (2003) also measured higher densities (with log(N e /cm −3 ) ranging from 10.20 to 10.45) in nearby quiet regions (their QS 1 might be a plage region) than in the plume (log(N e /cm −3 ) ∼ 9.9), and suggested that the gas pressure difference might be sufficient to drive siphon flows from outside the spot into the umbra. Our measured densities in different regions also seem to support this idea.…”

Section: Electron Densitiesmentioning

confidence: 95%

See 1 more Smart Citation

Solar transition region above sunspots

Curdt

Teriaca

Landi

et al. 2009

A&A

View full text Add to dashboard Cite

Aims. We study the transition region (TR) properties above sunspots and the surrounding plage regions, by analyzing several sunspot reference spectra obtained by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument in March 1999 and November 2006. Methods. We compare the SUMER spectra observed in the umbra, penumbra, plage, and sunspot plume regions. The hydrogen Lyman line profiles averaged in each of the four regions are presented. For the sunspot observed in 2006, the electron densities, differential emission measure (DEM), and filling factors of the TR plasma in the four regions are also investigated.Results. The self-reversals of the hydrogen Lyman line profiles are almost absent in sunspots at different locations (at heliocentric angles of up to 49 • ) on the solar disk. In the sunspot plume, the Lyman lines are also not reversed, whilst the lower Lyman line profiles observed in the plage region are obviously reversed, a phenomenon found also in the normal quiet Sun. The TR densities of the umbra and plume are similar and one order of magnitude lower than those of the plage and penumbra. The DEM curve of the sunspot plume exhibits a peak centered at log(T/K) ∼ 5.45, which exceeds the DEM of other regions by one to two orders of magnitude at these temperatures. We also find that more than 100 lines, which are very weak or not observed anywhere else on the Sun, are well observed by SUMER in the sunspot, especially in the sunspot plume. Conclusions. We suggest that the TR above sunspots is higher and probably more extended, and that the opacity of the hydrogen lines is much lower above sunspots, compared to the TR above plage regions. Our result indicates that the enhanced TR emission of the sunspot plume is probably caused by a large filling factor. The strongly enhanced emission at TR temperatures and the reduced continuum ensure that many normally weak TR lines are clearly distinctive in the spectra of sunspot plumes.

show abstract

Section: Electron Densitiessupporting

confidence: 85%

Section: Electron Densitiesmentioning

confidence: 95%

Solar transition region above sunspots

Curdt

Teriaca

Landi

et al. 2009

A&A

View full text Add to dashboard Cite

show abstract

“…A model that is consistent with the data involves nested flux tubes with a wide range of properties, including density, temperature, and flow speed. Evidence in support of this comes from extreme-UV observations, which show variable flow speeds of several tens of km s À1 and density contrasts of up to 2 ( Doyle & Madjarska 2003;Brosius 2005). Siphon flows along closed flux tubes in the corona are driven by significantly different properties near the footpoint and by different heating and cooling rates within the flux tube.…”

Section: Discussionmentioning

confidence: 94%

Depolarization of Radio Bursts Due to Reflection off Sharp Boundaries in the Solar Corona

Melrose

2006

ApJ

View full text Add to dashboard Cite

Depolarization of solar radio bursts requires reflection off boundary layers no thicker than about a wavelength (a few meters at most) between regions with large density ratios. The implied inhomogeneities suggest that the corona is much more highly and sharply structured than can be resolved from observations at other wavelengths. A simplified version of magnetoionic theory is used to derive a depolarization coefficient; the effect of the magnetic field is ignored in treating the dispersion, but taken into account in treating the (circular) polarization. Plots of the depolarization coefficient are used to infer conditions under which effective depolarization occurs, and it is concluded that favorable conditions require total internal reflection. For type I sources away from the central meridian, effective depolarization requires reflection off an overdense structure with a density ratio % 10. For type III bursts, a density ratio % 2 suffices, with at least two reflections off walls of ducts at %20 to the radial.

show abstract

“…Sunspot plumes are generally located above sunspots and have downflows of 20-30 km s −1 (Maltby et al 1999;Brynildsen et al 2001;Brosius 2005). They flow from outside the sunspots toward the umbrae due to gas pressure difference (Doyle & Madjarska 2003). In addition, it has been reported that plumes are identified in EUV lines formed at TR temperatures of 5.2 ≤ log T (K)≤ 5.9 (Brosius 2005).…”

Section: Discussionmentioning

confidence: 99%

Oscillatory Response of the Solar Chromosphere to a Strong Downflow Event Above a Sunspot

Kwak

Chae

Song

et al. 2016

ApJL

View full text Add to dashboard Cite

We report three-minute oscillations in the solar chromosphere driven by a strong downflow event in a sunspot. We used the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope and the Interface Region Imaging Spectrograph (IRIS). The strong downflow event is identified in the chromospheric and transition region lines above the sunspot umbra. After the event, oscillations occur at the same region. The amplitude of the Doppler velocity oscillations is 2 km s −1 , and gradually decreases with time. In addition, the period of the oscillations gradually increases from 2.7 minutes to 3.3 minutes. In the IRIS 1330 slit-jaw images, we identify a transient brightening near the footpoint of the downflow detected in the Hα+0.5Å image. The characteristics of the downflowing material are consistent with those of sunspot plumes. Based on our findings, we suggest that the gravitationally stratified atmosphere came to oscillate with three minute period in response to the impulsive downflow event as was theoretically investigated by Chae & Goode (2015).

show abstract

Sunspot plume observations in the EUV

Cited by 13 publications

References 13 publications

Solar transition region above sunspots

Solar transition region above sunspots

Depolarization of Radio Bursts Due to Reflection off Sharp Boundaries in the Solar Corona

Oscillatory Response of the Solar Chromosphere to a Strong Downflow Event Above a Sunspot

Contact Info

Product

Resources

About