Coronal Rotation at Solar Minimum from UV Observations

Giordano, S.; Mancuso, Salvatore

doi:10.1086/591923

Cited by 42 publications

(74 citation statements)

References 41 publications

(55 reference statements)

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“…Giordano & Mancuso (2008) supported the view that the observed discrepancy between the LASCO C1 and C2 observations of the rotation rates in the inner and outer corona was not an artifact caused by the different sensitivity (or systematic errors) of the two LASCO telescopes, but a real feature. Their analysis, however, was limited to a one-year period, while the radial dependence of the equatorial coronal rotation rate, as well as the coronal rotation rate itself at a selected height, might vary considerably along the solar cycle.…”

Section: Introductionsupporting

confidence: 60%

“…Averaging over this latitude range allows one to increase the statistics without affecting the determination of the equatorial coronal rotation rate at each height because of the small latitudinal variation around the equatorial area (e.g., Giordano & Mancuso 2008). The projected areas of these regions are shown in Fig.…”

Section: Observations and Data Analysismentioning

confidence: 99%

“…Recently, time-series observations of the coronal O vi 1032 Å spectral line intensity provided by the UltraViolet Coronagraph Spectrometer (UVCS/SOHO; Kohl et al 1995) telescope onboard SOHO have been analyzed by Giordano & Mancuso (2008) and Mancuso & Giordano (2011) to study the differential rotation of the solar corona during the minimum and maximum phase of activity of solar cycle 23. Giordano & Mancuso (2008) supported the view that the observed discrepancy between the LASCO C1 and C2 observations of the rotation rates in the inner and outer corona was not an artifact caused by the different sensitivity (or systematic errors) of the two LASCO telescopes, but a real feature.…”

Section: Introductionmentioning

confidence: 99%

“…In the present work, which follows the two previous studies of Giordano & Mancuso (2008) and Mancuso & Giordano (2011) on the rotation of the ultraviolet solar corona, we will extend the periodicity analysis to cover almost a full solar cycle, from the minimum of 1996 to the late descending phase of activity in 2006, and an interval of heights ranging from 1.6 to 3.0 R . In contrast to the previous two works, however, we will restrict our analysis to the equatorial region, where the rotation rates are best established, data from higher altitudes are also available, and problems caused by projection effects (e.g., Roša et al 1998), which might be present at higher latitudes and thus affect our analysis, are avoided.…”

Section: Introductionmentioning

confidence: 99%

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Coronal equatorial rotation during solar cycle 23: radial variation and connections with helioseismology

Mancuso

Giordano

2012

A&A

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Time-series observations of the O vi 1032 Å spectral line intensity provided by the UltraViolet Coronagraph Spectrometer (UVCS) telescope aboard the Solar and Heliospheric Observatory (SOHO) spacecraft have been analyzed to establish the rotational characteristics of the equatorial solar corona as a function of height and time during solar cycle 23. Overall, the coronal rotation period is observed to vary considerably from 1996 to 2006, with episodes of sudden acceleration and deceleration. On average, the rotation period in the equatorial corona tends to increase radially by ∼0.2 days/R from 1.6 to 3.0 R . An anticorrelation throughout the solar cycle is observed between the radial gradients in the inner corona ( < ∼ 2.2 R ), where the magnetic pressure dominates and the plasma is more rigidly connected, and the outer corona ( > ∼ 2.4 R ), where the field lines open up. Around the equator, the extended corona is found to rotate faster than the underlying photosphere, but its rotation rate is comparable to that estimated within the subphotospheric layers in the outer 5% of the Sun. Moreover, a striking significant positive correlation (r = 0.629 at the 0.99 R level) has been discovered between the variations in the residual rotation rates of the coronal and subphotospheric equatorial plasma, at least down to 0.95 R . This correlation suggests that the observed variations in the coronal rotation rate reflect the dynamic changes inferred within the near-surface shear layer, where the tracer structures responsible for the observed coronal emission are thus most probably anchored. These results raise the possibility that the plasma in the upper layers of the solar convection zone, at least around the equator, may be tightly connected to the plasma in the extended corona and that the deeper layers in the Sun might thus directly influence the dynamic evolution of the solar wind.

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Section: Introductionsupporting

confidence: 60%

Section: Observations and Data Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coronal equatorial rotation during solar cycle 23: radial variation and connections with helioseismology

Mancuso

Giordano

2012

A&A

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“…Probably the most popular method to study the kinematics of the solar surface features is a standard power spectrum analysis and its variants (just an example - Temmer et al 2004;Giordano 2008). This kind of analysis can be applied to latitude strips and in this way the differential rotation can be taken into account.…”

Section: Discussionmentioning

confidence: 99%

Solar active regions: a nonparametric statistical analysis

Pelt

Korpi

Tuominen

2010

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Context. The sunspots and other solar activity indicators tend to cluster on the surface of the Sun. These clusters very often occur at certain longitudes that persist in time. It is of general interest to find new and simple ways to characterize the observed distributions of different indicators and their behaviour in time. Aims. In the present work we use Greenwich sunspot data to evaluate the statistical but not totally coherent stability of the sunspot distribution along latitudes as well as longitudes. The aim was to obtain information on the longitudinal distribution of the underlying spot-generating mechanism rather than on the distribution and migration of sunspots or sunspot groups on the solar surface. Therefore only sunspot groups were included in the analysis, and only the time of their first appearance was used. Methods. We used a simple nonparametric approach to reveal sunspot migration patterns and their persistency. Results. Our analysis shows that regions where spots are generated tend to rotate differentially as the spots and spot groups themselves do. The spatial correlations in activity, however, tend to break down relatively fast, during 7-15 solar rotations. Conclusions. This study provides a challenge for solar dynamo models, as our results indicate that the non-axisymmetric spotgenerating mechanism experiences differential rotation (known as phase mixing in dynamo theory). The new nonparametric method introduced here, completely independent of the choice of the longitudinal distribution of sunspots, was found to be a useful tool for spatio-temporal analysis of surface features.

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UVCS/SOHO catalog of coronal mass ejections from 1996 to 2005: Spectroscopic proprieties

et al. 2013

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[1] Ultraviolet spectra of the extended solar corona have been routinely obtained by SOHO/UltraViolet Coronagraph Spectrometer (UVCS) since 1996. Sudden variations of spectral parameters are mainly due to the detection of coronal mass ejections (CMEs) crossing the instrumental slit. We present a catalog of CME ultraviolet spectra based upon a systematic search of events in the Large Angle and Spectrometric Coronagraph (LASCO) CME catalog, and we discuss their statistical properties. Our catalog includes 1059 events through the end of 2005, covering nearly a full solar cycle. It is available online at the URL http://solarweb.oato.inaf.it/UVCS_CME and embedded in the online LASCO CME catalog (http://cdaw.gsfc.nasa.gov/CME_list). The emission lines observed provide diagnostics of CME plasma parameters, such as the light-of-sight velocity, density, and temperature and allow to link the CME onset data to the extended corona white-light images. The catalog indicates whether there are clear signatures of features such as shock waves, current sheets, O VI flares, helical motions, and which part of the CME structures (front, cavity, or prominence material) are detected. The most common detected structure is the cool prominence material (in about 70% of the events). For each event, the catalog also contains movies, images, plots, and information relevant to address detailed scientific investigations. The number of events detected in UV is about one tenth of the LASCO CMEs and about one fourth of the halo events. We find that UVCS tends to detect faster, more massive, and energetic CME than LASCO, and for about 40% of the events, it has been possible to determine the plasma light-of-sight velocity.

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Coronal Rotation at Solar Minimum from UV Observations

Cited by 42 publications

References 41 publications

Coronal equatorial rotation during solar cycle 23: radial variation and connections with helioseismology

Coronal equatorial rotation during solar cycle 23: radial variation and connections with helioseismology

Solar active regions: a nonparametric statistical analysis

UVCS/SOHO catalog of coronal mass ejections from 1996 to 2005: Spectroscopic proprieties

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