Three-dimensional Density Structure of a Solar Coronal Streamer Observed by SOHO/LASCO and STEREO/COR2 in Quadrature

Decraemer, Bieke; Zhukov, A. N.; Doorsselaere, Tom Van

doi:10.3847/1538-4357/ab3b58

Cited by 18 publications

(16 citation statements)

References 49 publications

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“…Estimates for the density in the streamer slab can be obtained from the density models that are available for fitting to white-light images (see e.g. Decraemer et al 2019). Then the theoretical models can be used to obtain an estimate for the still unknown parameters, such as the magnetic field strength and the background solar wind speed.…”

Section: Discussionmentioning

confidence: 99%

“…One could investigate this relation more closely through reconstructing the 3D structure of the corona for each event separately (see e.g. Decraemer et al 2019) and analyzing why one can only observe the streamer wave events from specific viewing angles. The events found during the periods around the quadratures between SOHO and STEREO A/B in 2011 and between STEREO A and B in 2013 could be especially interesting for this.…”

Section: Data Surveymentioning

confidence: 99%

“…In white-light images, the narrowly outlined bright streamer stalk is actually the head-on projection of a dense plasma sheet (see e.g. Wang et al 1997;Saez et al 2007;Decraemer et al 2019). This plasma sheet envelops a current sheet, that extends outwards as the heliospheric current sheet.…”

Section: Introductionmentioning

confidence: 99%

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Properties of Streamer Wave Events Observed during the STEREO Era

Decraemer

Zhukov

Doorsselaere

2020

ApJ

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Transverse waves are sometimes observed in solar helmet streamers, typically after the passage of a coronal mass ejection (CME). The CME-driven shock wave moves the streamer sideways, and a decaying oscillation of the streamer is observed after the CME passage. Previous works generally reported observations of streamer oscillations taken from a single vantage point (typically the SOHO spacecraft). We conduct a data survey searching for streamer wave events observed by the COR2 coronagraphs onboard the STEREO spacecraft. For the first time, we report observations of streamer wave events from multiple vantage points, by using the COR2 instrument on both STEREO A and B, as well as the SOHO/LASCO C2+C3 coronagraphs. We investigate the properties of streamer waves by comparing the different events and performing a statistical analysis. Common observational features give us additional insight on the physical nature of streamer wave events. The most important conclusion is that there appears to be no relation between the speed of the CME and the phase speed of the resulting streamer wave, indicating that the streamer wave speed is determined by the physical properties of the streamer rather than the properties of the CME. This result makes streamer waves events excellent candidates for coronal seismology studies. From a comparison between the measured phase speeds and the phase speeds calculated from the measured periods and wavelengths, we could determine that the speed of the post-shock solar wind flow in our streamers is around 300 km s −1 .

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Section: Discussionmentioning

confidence: 99%

Section: Data Surveymentioning

confidence: 99%

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Properties of Streamer Wave Events Observed during the STEREO Era

Decraemer

Zhukov

Doorsselaere

2020

ApJ

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“…If the streamer location was such that it lay in between Wind and the type II shock, then STEREO-A would have been able to observe the type II directly, and Wind only through the streamer. Modeled streamer densities (Decraemer, Zhukov, and Van Doorsselaere, 2019) are very near to the type II density values at these heights.…”

Section: Observations From Different Viewing Anglesmentioning

confidence: 72%

Formation of Isolated Radio Type II Bursts at Low Frequencies

Pohjolainen

Sheshvan

2021

Sol Phys

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The first appearance of radio type II burst emission at decameter-hectometer (DH) waves typically occurs in connection, and often simultaneously, with other types of radio emissions. As type II bursts are signatures of propagating shock waves that are associated with flares and coronal mass ejections (CMEs), a rich variety of radio emissions can be expected. However, sometimes DH type II bursts appear in the dynamic spectra without other or earlier radio signatures. One explanation for them could be that the flare-CME launch happens on the far side of the Sun, and the emission is observed only when the source gets high enough in the solar atmosphere. In this study we have analysed 26 radio type II bursts that started at DH waves and were well-separated (‘isolated’) from other radio emission features. These bursts were identified from all DH type II bursts observed in 1998 – 2016, and for 12 events we had observations from at least two different viewing angles with the instruments on board Wind and the Solar Terrestrial Relations Observatory (STEREO) satellites. We found that only 30% of the type II bursts had their source origin on the far side of the Sun, but also that no bursts originated from the central region of the Sun (longitudes E30 – W40). Almost all of the isolated DH type II bursts could be associated with a shock near the CME leading front, and only few were determined to be shocks near the CME flank regions. In this respect our result differs from earlier findings. Our analysis, which included inspection of various CME and radio emission characteristics, suggests that the isolated DH type II bursts could be a special subgroup within DH type II bursts, where the radio emission requires particular coronal conditions to form and to die out.

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“…Here ψ denotes the orientation of the polarizer direction with respect to the x-axis of the image, and it can be 0, 60, or 120. The approach is based on the approaches described in Decraemer et al (2019). A global coronal density model was taken from Guhathakurta et al (1996), Table 3B and 3C, which included a polar corona and a streamer (called a current sheet therein).…”

Section: Polarized Imagesmentioning

confidence: 99%

Expected performances of the PROBA-3/ASPIICS solar coronagraph: Simulated data

Shestov

Zhukov

Inhester

et al. 2021

A&A

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Context. The Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS) is a novel externally occulted solar coronagraph that will be launched on board the Project for On-Board Autonomy (PROBA-3) mission in 2023. The external occulter will be placed on the first satellite ∼ 150 m ahead of the second satellite, which will carry an optical instrument. During 6 hours per orbit, the satellites will fly in a precise formation and will constitute a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights of ∼ 1.1R ⊙ . Aims. Developing and testing of algorithms for the scientific image processing requires understanding of all the optics-related and detector-related effects of the coronagraph, development of appropriate physical and numerical models, and preparation of simulated images that include all these effects. At the same time, an analysis of the simulated data gives valuable information about the performance of the instrument, the suitable observation regime, and the amount of telemetry. Methods. We used available physical models of the instrument and implemented them as a software to generate simulated data. We analyzed intermediate and complete simulated images to obtain a better understanding of the performance of ASPIICS, in particular, to predict its photometric sensitivity, effect of noise, suitable exposure times, etc. Results. The proposed models and algorithms are used not only to create the simulated data, but also to form the basis for the scientific processing algorithms to be applied during on-ground ASPIICS data processing. We discuss the possible effect of noise and the uncertainty of the calibration factors on the accuracy of final data, and propose suitable exposure times.

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Three-dimensional Density Structure of a Solar Coronal Streamer Observed by SOHO/LASCO and STEREO/COR2 in Quadrature

Cited by 18 publications

References 49 publications

Properties of Streamer Wave Events Observed during the STEREO Era

Properties of Streamer Wave Events Observed during the STEREO Era

Formation of Isolated Radio Type II Bursts at Low Frequencies

Expected performances of the PROBA-3/ASPIICS solar coronagraph: Simulated data

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