The F-corona and the Circum-Solar Dust Evidences and Properties [G. Nikolsky Memorial Lecture]

Koutchmy, S.; Lamy, Philippe

doi:10.1007/978-94-009-5464-9_14

Cited by 81 publications

(42 citation statements)

References 19 publications

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“…Preliminary analysis indicates that we detect F-coronal intensities ranging from 1.25 ×10 −11 to 1.7 ×10 −13 B o in the region from 4 to 24 degrees from the Sun (15 to 95 solar radii above the limb), which is consistent with but slightly lower than the intensity values predicted by Koutchmy and Lamy (1985). Extending such unique measurements to more observations is clearly essential for characterising the F-coronal distribution out to Earth-like distances.…”

Section: Discussionsupporting

confidence: 74%

“…For Figure 12a, which means for the F-coronal intensity, we see the intensity drop from 1.25 ×10 −11 to 1.7 ×10 −13 B o . These figures compare favourably with the values predicted by Koutchmy and Lamy (1985) when one considers that (a) the spacecraft was rolled by 22 degrees, so we are probably seeing reduced intensities relative to the equatorial values, and (b) the Koutchmy and Lamy values are from a modelled corona rather than measurement. Indeed, the latter fact stresses the need for the HI instruments to produce the first and definitive study of the measured F-coronal intensity along the Sun -Earth line.…”

Section: ×10supporting

confidence: 80%

“…The lower panel of Figure 2 shows, on the same elongation axis, the anticipated signal of the F + K corona, in units of B o , the solar disc intensity. This curve is based on projections calculated by Koutchmy and Lamy (1985). Also shown is the anticipated intensity of an average CME, as a function of elongation.…”

Section: The Heliospheric Imagersmentioning

confidence: 99%

“…We examine the CME intensity along the line denoted XZ. Figure 12a shows the intensity (in arbitrary units) along the line, plotted against image pixel number (from an image array 1024 pixels across) prior to the F-coronal subtraction; the curve is dominated by the F-corona and can be compared to the predicted F-coronal intensity of Koutchmy and Lamy (1985) (see Figure 2). Their Figure 3 suggests that above the solar equator the F-coronal intensity should be 8 ×10 −11 B o at the inner edge of HI-1 and 1 ×10 −12 B o at the outer edge.…”

Section: Figurementioning

confidence: 99%

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First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line

et al. 2007

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We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the SunEarth line, that is, those directed towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detect CMEs in the heliosphere, and this is an extremely important milestone for CME research. For the principal event being analysed here we demonstrate an ability to track a CME from the corona to over 40 degrees. The time -altitude history shows a constant speed of ascent over at least the first 50 solar radii and some evidence for deceleration at distances of over 20 degrees. Comparisons of associated coronagraph data and the HI images show that the basic structure of the CME remains clearly intact as it propagates from the corona into the heliosphere. Extracting the CME signal requires a consideration of the F-coronal intensity distribution, which can be identified from the HI data. Thus we present the preliminary results on this measured F-coronal intensity and compare these to the modelled F-corona of Koutchmy and Lamy (IAU Colloq. 85, 63, 1985). This analysis demonstrates that CME material some two orders of magnitude weaker than the F-corona can be detected; a specific example at 40 solar radii revealed CME intensities as low as 1.7×10 −14 of the solar brightness. These observations herald a new era in CME research as we extend our capability for tracking, in particular, Earth-directed CMEs into the heliosphere.

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Section: Discussionsupporting

confidence: 74%

Section: ×10supporting

confidence: 80%

Section: The Heliospheric Imagersmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line

et al. 2007

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“…Since our MHD model only allows us to directly treat electron density, we estimate the contribution of dust scattering with the same power-law empirical relationship used to make the LASCO images. In this case, the background F corona brightness is taken to have the form B F ¼ cr (0:22 cos (2 )À2:47) ( Koutchmy & Lamy 1985). Here we estimate the magnitude of c by setting B F ¼ B K at r ¼ 4 R , where B K is the background polar brightness of the K corona taken from Saito et al (1977).…”

Section: Comparisons With Lasco Observationsmentioning

confidence: 99%

Three‐dimensional MHD Simulation of the 2003 October 28 Coronal Mass Ejection: Comparison with LASCO Coronagraph Observations

Manchester

Vourlidas

Tóth

et al. 2008

Astrophysical Journal

151

117

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We numerically model the coronal mass ejection (CME) event of 2003 October 28 that erupted from AR 10486 and propagated to Earth in less than 20 hr, causing severe geomagnetic storms. The magnetohydrodynamic (MHD) model is formulated by first arriving at a steady state corona and solar wind employing synoptic magnetograms. We initiate two CMEs from the same active region, one approximately a day earlier that preconditions the solar wind for the much faster CME on the 28th. This second CME travels through the corona at a rate of over 2500 km s À1 , driving a strong forward shock. We clearly identify this shock in an image produced by the Large Angle Spectrometric Coronagraph (LASCO) C3 and reproduce the shock and its appearance in synthetic white-light images from the simulation. We find excellent agreement with both the general morphology and the quantitative brightness of the model CME with LASCO observations. These results demonstrate that the CME shape is largely determined by its interaction with the ambient solar wind and may not be sensitive to the initiation process. We then show how the CME would appear as observed by wide-angle coronagraphs on board the Solar Terrestrial Relations Observatory (STEREO) spacecraft. We find complex time evolution of the white-light images as a result of the way in which the density structures pass through the Thomson sphere. The simulation is performed with the Space Weather Modeling Framework (SWMF).

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Coronal electron density distributions estimated from CMEs, DH type II radio bursts, and polarized brightness measurements

et al. 2016

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We determine coronal electron density distributions (CEDDs) by analyzing decahectometric (DH) type II observations under two assumptions. DH type II bursts are generated by either (1) shocks at the leading edges of coronal mass ejections (CMEs) or (2) CME shock‐streamer interactions. Among 399 Wind/WAVES type II bursts (from 1997 to 2012) associated with SOHO/LASCO (Large Angle Spectroscopic COronagraph) CMEs, we select 11 limb events whose fundamental and second harmonic emission lanes are well identified. We determine the lowest frequencies of fundamental emission lanes and the heights of leading edges of their associated CMEs. We also determine the heights of CME shock‐streamer interaction regions. The CEDDs are estimated by minimizing the root‐mean‐square error between the heights from the CME leading edges (or CME shock‐streamer interaction regions) and DH type II bursts. We also estimate CEDDs of seven events using polarized brightness (pB) measurements. We find the following results. Under the first assumption, the average of estimated CEDDs from 3 to 20 Rs is about 5‐fold Saito's model (NSaito(r)). Under the second assumption, the average of estimated CEDDs from 3 to 10 Rs is 1.5‐fold NSaito(r). While the CEDDs obtained from pB measurements are significantly smaller than those based on the first assumption and CME flank regions without streamers, they are well consistent with those on the second assumption. Our results show that not only about 1‐fold NSaito(r) is a proper CEDD for analyzing DH type II bursts but also CME shock‐streamer interactions could be a plausible origin for generating DH type II bursts.

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The F-corona and the Circum-Solar Dust Evidences and Properties [G. Nikolsky Memorial Lecture]

Cited by 81 publications

References 19 publications

First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line

First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line

Three‐dimensional MHD Simulation of the 2003 October 28 Coronal Mass Ejection: Comparison with LASCO Coronagraph Observations

Coronal electron density distributions estimated from CMEs, DH type II radio bursts, and polarized brightness measurements

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