Solar minimum streamer densities and temperatures using Whole Sun Month coordinated data sets

Gibson, S. E.; Fludra, A.; Bagenal, F.; Biesecker, D. A.; Zanna, G. Del; Bromage, B. J. I.

doi:10.1029/98ja02681

Cited by 147 publications

(195 citation statements)

References 26 publications

Supporting

Mentioning

171

Contrasting

Order By: Relevance

“…It is worth noting that the quiescent streamer reported by Uzzo et al (2006) was at a similar latitude to the one investigated here and was observed in April 2003 while the solar activity was still decreasing. Conversely, the equatorial streamers of Gibson et al (1999) and Strachan et al (2002), the equatorial and mid-latitude active region streamers of Parenti et al (2000) and the depleted-core equatorial streamer of Frazin et al (2003) were observed during a minimum phase of the solar activity. The results presented by Ventura et al (2005) concern a collection of streamer observations performed at different latitudes in 1997 and 2000, hence near solar minimum and maximum respectively.…”

Section: Discussionmentioning

confidence: 99%

“…This can reasonably apply to our case, because the wind velocity may be considered as a minor term in force balance. Actually, the radial outflow velocities determined in this study reach values of about 100 km s −1 at heights around 5 R , while the thermal velocities of electrons corresponding to the temperatures found in the examined streamer are significantly higher than this value everywhere (see also the discussion in Gibson et al 1999). The computations were carried out using both the density profile deduced from LASCO C2 pB data inversion and the one giving the best fit of the O vi observations.…”

Section: Diagnostics Of Physical Parametersmentioning

confidence: 99%

“…Once the electron density had been derived, we deduced the electron temperature (T e ) profile along the central region of the streamer according to the method described by Gibson et al (1999), which calculates temperatures from radial power-law fits to the combined density data set, assuming that the streamer plasma is in radial hydrostatic equilibrium. This implies that there are no significant dynamic forces and that thermal pressure is balanced by gravity.…”

Section: Diagnostics Of Physical Parametersmentioning

confidence: 99%

See 2 more Smart Citations

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Spadaro

Susino

Ventura

et al. 2007

A&A

View full text Add to dashboard Cite

Context. Investigating the physical properties of solar coronal streamers is important for understanding their role in the global magnetic structure of the extended solar atmosphere, as well as in the generation of the slow solar wind. Aims. We hope to contribute as completely as possible to the ongoing SOHO instruments campaign devoted to the study of the physical characteristics of coronal streamers at various heliocentric distances. Results. Electron densities and temperatures, H i and O vi kinetic temperatures, and outflow velocities were derived from the line intensities and widths, as well as from the O vi line intensity ratio in the 1.6−5 R range of heights, limited to the central region of the streamer. To our knowledge, the H i outflow velocities obtained in this work are the first ones determined inside a streamer structure. They are significantly lower than those of the O vi ions. This, together with the O vi kinetic temperatures that are much higher than the H i ones, suggest that the absorption of Alfvén waves at the ion cyclotron frequency might also occur inside streamers. Methods. We analyzed ultraviolet H iConclusions. In comparison with other streamers described in the literature, the structure examined in this work generally exhibits lower electron density and neutral hydrogen kinetic temperature. Conversely, the O vi kinetic temperature and outflow velocity radial profiles are consistent with the results for the other examined streamers.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Diagnostics Of Physical Parametersmentioning

confidence: 99%

Section: Diagnostics Of Physical Parametersmentioning

confidence: 99%

See 1 more Smart Citation

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Spadaro

Susino

Ventura

et al. 2007

A&A

View full text Add to dashboard Cite

show abstract

“…To estimate the real coronal density distribution we make use of two different density radial profiles n e,cor available in the literature, representing two different extremes of electron density values. In particular, we set as input for our calculations either the coronal hole density distribution modeled by Cranmer et al (1999) or the streamer density profile at solar minimum derived by Gibson et al (1999), respectively given by …”

Section: Estimate Of Blob Electron Densitymentioning

confidence: 99%

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

Dolei

Бемпорад

Spadaro

2014

A&A

View full text Add to dashboard Cite

In this work we study the kinematics of three small-scale (0.01 R ) blobs of chromospheric plasma falling back to the Sun after the huge eruptive event of June 7, 2011. From a study of 3D trajectories of blobs made with the Solar TErrestrial RElations Observatory (STEREO) data, we demonstrate the existence of a significant drag force acting on the blobs and calculate two drag coefficients, in the radial and tangential directions. The resulting drag coefficients C D are between 0 and 5, comparable in the two directions, making the drag force only a factor of 0.45-0.75 smaller than the gravitational force. To obtain a correct determination of electron densities in the blobs, we also demonstrate how, by combining measurements of total and polarized brightness, the Hα contribution to the white-light emission observed by the COR1 telescopes can be estimated. This component is significant for chromospheric plasma, being between 95 and 98% of the total white-light emission. Moreover, we demonstrate that the COR1 data can be employed even to estimate the Hα polarized component, which turns out to be in the order of a few percent of Hα total emission from the blobs. If the drag forces acting on small-scale blobs reported here are similar to those that play a role during the CME propagation, our results suggest that the magnetic drag should be considered even in the CME initiation modelling.

show abstract

“…Cranmer et al, 1999; Antonucci et al, 2000). The coronal electron temperature, T e , assumed in the analysis, is that derived by Gibson et al (1999) for the minimum of solar activity and varies between 1.5×10 6 K and 9.5×10 5 K in the range of distance 1.5-2.5 R ⊙ . We point out that the T e values do not influence significantly the results of the analysis of electron density and outflow velocity: by assuming the electron temperature values of coronal hole, the obtained results are within the errors shown in Figures 7 and 8 (see the following section).…”

Section: Discussionmentioning

confidence: 99%

Coronal Pseudo-Streamer and Bipolar Streamer Observed by SOHO/UVCS in March 2008

et al. 2015

View full text Add to dashboard Cite

The last solar minimum is characterized by several peculiar aspects and by the presence of a complex magnetic topology with two different kinds of coronal streamers: pseudo-streamers and bipolar streamers. Pseudo-streamers or unipolar streamer are coronal structures which separate coronal holes of the same polarity, without a current sheet in the outer corona; unlike bipolar streamer that separate coronal holes of opposite magnetic polarity. In this study, two examples of these structures have been identified in the period of Carrington rotation 2067, by applying a potential-field source-surface extrapolation of the photospheric field measurements. We present a spectroscopic analysis of a pseudo-streamer and a bipolar streamer observed in the period 12-17 March 2008 at high spectral and spatial resolution by the Ultraviolet Coronagraph Spectrometer (UVCS; Kohl et al., 1995) onboard Solar and Heliospheric Observatory (SOHO). The solar wind plasma parameters, such as kinetic temperature, electron density and outflow velocity, are inferred in the extended corona (from 1.7 to 2.1 R ⊙ ) analysing the O vi doublet and Ly α line spectra. The coronal magnetic topology is taken into account and has been extrapolated by a 3D magneto-hydrodynamic model of the global corona. The results of the analysis show some peculiarities of the pseudo-streamer physical parameters in comparison with those obtained for bipolar streamers: in particular, we have found higher kinetic temperature and higher outflow velocities of O vi ions and lower electron density values. In conclusion, we point out that pseudo-streamers produce a "hybrid" type of outflow that is intermediate between slow and fast solar wind and they are a possible source of slow/fast wind in not dipolar solar magnetic field configuration.

show abstract

Solar minimum streamer densities and temperatures using Whole Sun Month coordinated data sets

Abstract: Abstract.We

Cited by 147 publications

References 26 publications

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Physical parameters of a mid-latitude streamer during the declining phase of the solar cycle

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

Coronal Pseudo-Streamer and Bipolar Streamer Observed by SOHO/UVCS in March 2008

Contact Info

Product

Resources

About