The Heliospheric Imagers Onboard the STEREO Mission

Eyles, C. J.; Harrison, R. A.; Davis, CJ; Waltham, N.; Shaughnessy, BM; Mapson-Menard, H.; Bewsher, D.; Crothers, S. R.; Davies, J. A.; Simnett, G. M.; Howard, R. A.; Moses, J. D.; Newmark, J. S.; Socker, D. G.; Halain, J. P.; Defise, J. M.; Mazy, Emmanuel; Rochus, Pierre

doi:10.1007/s11207-008-9299-0

Cited by 367 publications

(364 citation statements)

References 27 publications

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“…This study considers observations by instruments from the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI). The SECCHI package on each spacecraft (Howard et al, 2008;Eyles et al, 2009) provides STEREO's remote imaging capabilities. It consists of two coronagraphs (COR1 and COR2), an extreme ultraviolet imager (EUVI) and a pair of heliospheric imagers (HI-1 and HI-2).…”

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confidence: 99%

Assessing the Effect of Spacecraft Motion on Single-Spacecraft Solar Wind Tracking Techniques

2014

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Recent advances in wide-angle imaging by the Solar Mass Ejection Imager (SMEI) on board the Coriolis spacecraft and more recently by the Heliospheric Imagers (HI) aboard NASA's Solar TErrestrial RElations Observatory (STEREO), have enabled solar wind transients to be imaged and tracked from the Sun to 1 AU and beyond. In this paper we consider two of the techniques that have been used to determine the propagation characteristics of solar wind transients based on single-spacecraft observations, in particular propagation direction and radial speed. These techniques usually assume that the observing spacecraft remains stationary for the duration of observation of the solar wind transient. We determine the inaccuracy introduced by this assumption for the two STEREO spacecraft and find that it can be significant, and it can lead to an overestimation of the transient velocity as seen from STEREO-A and an underestimation as seen by STEREO-B. This has implications for the prediction or solar wind transients at 1 AU and hence is important for the study of space weather.

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confidence: 99%

Assessing the Effect of Spacecraft Motion on Single-Spacecraft Solar Wind Tracking Techniques

2014

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“…Therefore, an additional procedure is performed to adjust the size of the HI1 image, so the central coordinate of the image is referred to the center of the Sun. The FOV in an HI1 image is from 15 to 90 Rs (Eyles et al 2009) and the size is 256 · 256 pixels. The total FOV of 75 Rs would correspond to 256 columns in the scale of digital images, i.e., one solar radius is 3.4 columns.…”

Section: Pre-processing Modulementioning

confidence: 99%

“…The FOV in the COR2 and HI1 images is equal to 15 and 75 Rs (Eyles et al 2009), which correspond to 128 and 256 columns in an image. The projected height, denoted as RsImage in Eq.…”

Section: Tracking Modulementioning

confidence: 99%

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Combining STEREO SECCHI COR2 and HI1 images for automatic CME front edge tracking

Kirnosov

Chang

Pulkkinen

2016

J. Space Weather Space Clim.

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COR2 coronagraph images are the most commonly used data for coronal mass ejection (CME) analysis among the various types of data provided by the STEREO (Solar Terrestrial Relations Observatory) SECCHI (Sun-Earth Connection Coronal and Heliospheric Investigation) suite of instruments. The field of view (FOV) in COR2 images covers 2-15 solar radii (Rs) that allow for tracking the front edge of a CME in its initial stage to forecast the lead-time of a CME and its chances of reaching the Earth. However, estimating the lead-time of a CME using COR2 images gives a larger lead-time, which may be associated with greater uncertainty. To reduce this uncertainty, CME front edge tracking should be continued beyond the FOV of COR2 images. Therefore, heliospheric imager (HI1) data that covers 15-90 Rs FOV must be included. In this paper, we propose a novel automatic method that takes both COR2 and HI1 images into account and combine the results to track the front edges of a CME continuously. The method consists of two modules: pre-processing and tracking. The pre-processing module produces a set of segmented images, which contain the signature of a CME, for both COR2 and HI1 separately. In addition, the HI1 images are resized and padded, so that the center of the Sun is the central coordinate of the resized HI1 images. The resulting COR2 and HI1 image set is then fed into the tracking module to estimate the position angle (PA) and track the front edge of a CME. The detected front edge is then used to produce a height-time profile that is used to estimate the speed of a CME. The method was validated using 15 CME events observed in the period from January 1, 2008 to August 31, 2009. The results demonstrate that the proposed method is effective for CME front edge tracking in both COR2 and HI1 images. Using this method, the CME front edge can now be tracked automatically and continuously in a much larger range, i.e., from 2 to 90 Rs, for the first time. These improvements can greatly help in making the quantitative CME analysis more accurate and have the potential to assist in space weather forecasting.

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“…Provided that interaction can be found in the raypath, high-frequency IPS measurements can be used to detect the early formation of compression regions or shear between fast and slow streams. Since IPS measurements are sensitive to the approximate electron density squared, the technique has a much greater sensitivity to density changes in the solar wind than, for example, white-light observations such as those by the Solar Mass Ejection Imager (SMEI) instrument (Eyles et al, 2003;Jackson et al, 2004) or the HIs (Harrison, Davis, and Eyles, 2005;Harrison et al, 2008;Eyles et al, 2009) onboard the twin STEREO spacecraft (Kaiser, 2005;Kaiser et al, 2008): STEREO-A (Ahead) and STEREO-B (Behind). IPS measurements should therefore be able to detect compression regions closer to the Sun than other techniques.…”

Section: Observationsmentioning

confidence: 99%

Interplanetary Scintillation Observations of Stream Interaction Regions in the Solar Wind

et al. 2009

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We present a summary of results from ten years of interplanetary scintillation (IPS) observations of stream interaction regions (SIRs) in the solar wind. Previous studies had shown that SIRs were characterized by intermediate-velocity solar wind and -in the case of compressive interactions -higher levels of scintillation. In this study we considered all cases of intermediate velocities in IPS observations from the European Incoherent SCATter (EISCAT) radar facility made at low-and mid-heliographic latitudes between 1994 and 2003. After dismissing intermediate-velocity observations which were associated with solar-wind transients (such as coronal mass ejections) we found that the remaining cases of intermediate velocities lay above coronal structures where stream interaction would be expected. An improved ballistic mapping method (compared to that used in earlier EISCAT studies of interaction regions) was used to identify the regions of raypath in IPS observations which might be expected to include interaction regions and to project these regions out to the distances of in-situ observations. The early stages of developing compression regions, consistent with their development on the leading edges of compressive stream interaction regions, were clearly detected as close to the Sun as 30 R , and further ballistic projection out to the distances of in-situ observations clearly associated these developing structures with density and velocity features characteristic of developed interaction regions in in-situ data in the cases when such data were available. The same approach was applied to study non-compressive interaction regions (shear layers) between solar-wind streams of different velocities where the stream interface lay at near-constant latitude and the results compared with those from compressive interaction regions. The results confirm that intermediate velocities seen in IPS observations above stream boundaries may arise from either detection of intermediate-velocity flow in compression regions, or from non-compressive shear layers. The variation in velocity about the mean determined from IPS measurements (representing the spread in velocity across that part of the raypath associated with the interaction region in the analysis) was comparable in compressive and non-compressive regions -a potentially interesting result which may contain important information on the geometry of developing SIRs. It is clear from these results that compressive and non-compressive interaction regions belong to the same class of stream -stream interaction, with the dominant mode determined by the latitudinal gradient of the stream interface. Finally, we discuss the results from this survey in the light of new data from the Heliospheric Imagers (HI) on the Solar TErrestrial RElations Observatory (STEREO) spacecraft and other instruments, and suggest possible directions for further work.

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The Heliospheric Imagers Onboard the STEREO Mission

Cited by 367 publications

References 27 publications

Assessing the Effect of Spacecraft Motion on Single-Spacecraft Solar Wind Tracking Techniques

Assessing the Effect of Spacecraft Motion on Single-Spacecraft Solar Wind Tracking Techniques

Combining STEREO SECCHI COR2 and HI1 images for automatic CME front edge tracking

Interplanetary Scintillation Observations of Stream Interaction Regions in the Solar Wind

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