Stereoscopic observations of the effects of a halo CME on the solar coronal structure

Dolei, S.; Romano, P.; Spadaro, D.; Ventura, R.

doi:10.1051/0004-6361/201423449

Cited by 3 publications

(3 citation statements)

References 20 publications

(31 reference statements)

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“…We also performed the 3D reconstructions with the polarization ratio technique (first described by (Moran & Davila 2004)) that has been applied by many different authors to reconstruct solar eruptions in 3D based on single viewpoint observations. This technique is particularly interesting for halo CMEs (e.g., Dolei et al 2014;Lu et al 2017), and results from this technique were compared and validated with multiple viewpoint observations (see, e.g., Mierla et al 2010Mierla et al , 2011Feng et al 2013) and also with spectroscopic observations (Susino et al 2014). Nevertheless, before Metis, all the coronagraphic space-based data so far were acquired in the VL and using only three different angular orientations of the linear polarizer, typically separated by 60 • or 120 • .…”

Section: Reconstruction With Polarization Ratiomentioning

confidence: 99%

Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter

Бемпорад

Andretta

Susino

et al. 2022

A&A

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Context. On 2021 February 12, two subsequent eruptions occurred above the western limb of the Sun, as seen along the Sun-Earth line. The first event was a typical slow coronal mass ejection (CME), followed ∼ 7 hours later by a smaller and collimated prominence eruption, originating south of the CME, followed by a plasma blob. These events were observed not only by the SOHO and STEREO-A missions, but also by the suite of remote-sensing instruments on board Solar Orbiter. Aims. We show how data acquired by the Full Sun Imager (FSI), the Metis coronagraph, and the Heliospheric Imager (HI) from the Solar Orbiter perspective can be combined to study the eruptions and different source regions. Moreover, we show how Metis data can be analyzed to provide new information about solar eruptions. Methods. Different 3D reconstruction methods were applied to the data acquired by different spacecraft, including remote-sensing instruments on board Solar Orbiter. Images acquired by the two Metis channels in the visible light (VL) and H i Ly-α line (UV) were combined to derive physical information about the expanding plasma. The polarization ratio technique was also applied for the first time to Metis images acquired in the VL channel. Results. The two eruptions were followed in 3D from their source region to their expansion in the intermediate corona. By combining VL and UV Metis data, the formation of a post-CME current sheet (CS) was followed for the first time in the intermediate corona.The plasma temperature gradient across a post-CME blob propagating along the CS was also measured for the first time. Application of the polarization ratio technique to Metis data shows that by combining four different polarization measurements, the errors are reduced by ∼ 5 − 7%. This constrains the 3D plasma distribution better.Conclusions.

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Section: Reconstruction With Polarization Ratiomentioning

confidence: 99%

Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter

Бемпорад

Andretta

Susino

et al. 2022

A&A

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“…(1), we need to determine the streamer extent along the LOS. We were able to evaluate this length scale for the first time by using the information on the electron density, again, and developing a method similar to the one discussed by Dolei et al (2014b). We used the routine calc_cme_mass.pro available in the SolarSoftware library, which calculates the number of electrons providing the intensity in each pixel of the LASCO C2 pB images.…”

Section: Physical Parameter Estimatementioning

confidence: 99%

Visible light and ultraviolet observations of coronal structures: physical properties of an equatorial streamer and modelling of the F corona

Dolei

Spadaro

Ventura

2015

A&A

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The present work studies the characteristics of an equatorial streamer visible above the east limb of the Sun on March 2008, during the most recent minimum of solar activity. We analysed the visible light coronagraphic images of SOHO/LASCO and the ultraviolet observations in the H I Lyα spectral line obtained by SOHO/UVCS, and exploited the Doppler dimming effect of the coronal Lyα line to derive the outflow velocity profile of the scattering neutral hydrogen atoms in the streamer region. Taking advantage of the synergy between visible light and ultraviolet observations, we were able to determine all the properties of the coronal structure. In particular, the actual extent of the streamer along the line of sight has been evaluated for the first time. In so doing, the solar wind outflow velocity turned out to be the only free parameter in the theoretical modelling of the Lyα intensity. We found nearly static conditions below 3.5 R along the streamer axis, whereas the solar wind flows at velocities from 40 km s −1 to 140 km s −1 in the altitude range 2.5-5.0 R along the southern boundary of the streamer. We also derived the intensity distribution of the F coronal component in the LASCO C2 field of view, by combining total and polarized brightness data. Finally, we investigated the dependence of the Lyα resonant scattering process on the kinetic temperature of the coronal neutral hydrogen atoms and found that the value of this temperature mostly affects the scattering process at low heliocentric distances, where the solar wind flows with low velocity.

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“…Apart from radio observations above active regions, another path towards coronal polarimetry has been pursued with ground-based infrared (IR) observations measuring the Zeeman effect (Lin, Penn, and Tomczyk, 2000;Tomczyk et al, 2008). Another possibility has been opened with eclipse polarization measurements in red and green channels by Kim et al (2013b) from which these authors concluded that "the polarization excess (green-red) can be explained by the presence of neutral hydrogen in the corona" (see also Dolei et al, 2014). As mentioned by Kim et al (2013b), Poland and Munro (1976) and Mierla et al (2011) had already concluded that Hα contributed to coronagraphic images of transients and coronal mass ejections (CMEs), respectively.…”

Section: Introductionmentioning

confidence: 99%

Neutral Hydrogen and Its Emission Lines in the Solar Corona

Vial

Chane-Yook

2016

Sol Phys

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Since the Lα rocket observations of (Gabriel, Solar Phys. 21, 392, 1971), it has been realized that the hydrogen (H) lines could be observed in the corona and offer an interesting diagnostic for the temperature, density, and radial velocity of the coronal plasma. Moreover, various space missions have been proposed to measure the coronal magnetic and velocity fields through polarimetry in H lines. A necessary condition for such measurements is to benefit from a sufficient signal-to-noise ratio. The aim of this article is to evaluate the emission in three representative lines of H for three different coronal structures. The computations have been performed with a full non-local thermodynamicequilibrium (non-LTE) code and its simplified version without radiative transfer. Since all collisionnal and radiative quantities (including incident ionizing and exciting radiation) are taken into account, the ionization is treated exactly. Profiles are presented at two heights (1.05 and 1.9 solar radii, from Sun center) in the corona, and the integrated intensities are computed at heights up to five solar radii. We compare our results with previous computations and observations (e.g. Lα from UVCS) and find a rough (model-dependent) agreement. Since the Hα line is a possible candidate for ground-based polarimetry, we show that in order to detect its emission in various coronal structures, it is necessary to use a very narrow (less than 2Å wide) bandpass filter.

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Stereoscopic observations of the effects of a halo CME on the solar coronal structure

Cited by 3 publications

References 20 publications

Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter

Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter

Visible light and ultraviolet observations of coronal structures: physical properties of an equatorial streamer and modelling of the F corona

Neutral Hydrogen and Its Emission Lines in the Solar Corona

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