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

Conlon, Thomas; Milan, S. E.; Davies, J. A.

doi:10.1007/s11207-014-0549-z

Cited by 8 publications

(12 citation statements)

References 20 publications

(21 reference statements)

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“…• in each case, consistent with the results presented by Conlon, Milan, and Davies (2014). Correcting for spacecraft motion makes little difference to the estimated speed.…”

Section: Remote Cir Observations From Stereosupporting

confidence: 86%

“…for lower φ-values the revised speed was lower than that presented by Rouillard et al (2010). This is consistent with the findings of Conlon, Milan, and Davies (2014). As mentioned previously, Rouillard et al (2010) also performed this analysis on STEREO-B/HI observations; however, they only have a few tracks from each CIR as seen from STEREO-B and so we have only included the STEREO-A results here.…”

Section: Remote Cir Observations From Stereosupporting

confidence: 86%

“…As discussed by Conlon, Milan, and Davies (2014), φ will not actually be constant even if the transient propagates out radially, as spacecraft motion during the propagation of the transient will cause φ to vary, changing by about 1…”

Section: Remote Cir Observations From Stereomentioning

confidence: 99%

“…They observed this primarily with STEREO-A, for which they had more data. The effects of spacecraft motion on fixed-φ fitting of single time-elongation profiles noted by Conlon, Milan, and Davies (2014) change the fitted propagation speed and φ so we first consider whether it can explain the trend observed by Rouillard et al (2010). Table 1 gives an estimate for the radial propagation speed assuming that spacecraft motion is corrected for.…”

Section: Remote Cir Observations From Stereomentioning

confidence: 99%

“…Fits, by eye, were performed to the whole family of traces in each instance to estimate radial propagation speeds, as outlined in Section 1. The fitting was performed to equations that incorporate the correction for spacecraft motion outlined by Conlon, Milan, and Davies (2014). For each CIR identified this way, we thus have a single estimated radial propagation speed for all of the features associated with the CIR (as opposed to a single speed per time-elongation profile).…”

Section: Cir Propagation Speedmentioning

confidence: 99%

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Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

et al. 2015

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NASA's Solar Terrestrial Relations Observatory (STEREO) mission has coincided with a pronounced solar minimum. This allowed for easier detection of corotating interaction regions (CIRs). CIRs are formed by the interaction between fast and slow solarwind streams ejected from source regions on the solar surface that rotate with the Sun. High-density plasma blobs that have become entrained at the stream interface can be tracked out to large elongations in data from the Heliospheric Imager (HI) instruments onboard STEREO. These blobs act as tracers of the CIR itself such that their HI signatures can be used to estimate CIR source location and radial speed. We estimate the kinematic properties of solar-wind transients associated with 40 CIRs detected by the HI instrument onboard the STEREO-A spacecraft between 2007 and 2010. We identify in-situ signatures of these transients at L1 using the Advanced Composition Explorer (ACE) and compare the in-situ parameters with the HI results. We note that solar-wind transients associated with CIRs appear to travel at or close to the slow solar-wind speed preceding the event as measured in situ. We also highlight limitations in the commonly used analysis techniques of solar-wind transients by considering variability in the solar wind.

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“…• in each case, consistent with the results presented by Conlon, Milan, and Davies (2014). Correcting for spacecraft motion makes little difference to the estimated speed.…”

Section: Remote Cir Observations From Stereosupporting

confidence: 86%

Section: Remote Cir Observations From Stereosupporting

confidence: 86%

Section: Remote Cir Observations From Stereomentioning

confidence: 99%

Section: Remote Cir Observations From Stereomentioning

confidence: 99%

Section: Cir Propagation Speedmentioning

confidence: 99%

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Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

et al. 2015

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Differences between the CME fronts tracked by an expert, an automated algorithm, and the Solar Stormwatch project

et al. 2015

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Observations from the Heliospheric Imager (HI) instruments aboard the twin STEREO spacecraft have enabled the compilation of several catalogues of coronal mass ejections (CMEs), each characterizing the propagation of CMEs through the inner heliosphere. Three such catalogues are the Rutherford Appleton Laboratory (RAL)-HI event list, the Solar Stormwatch CME catalogue, and, presented here, the J-tracker catalogue. Each catalogue uses a different method to characterize the location of CME fronts in the HI images: manual identification by an expert, the statistical reduction of the manual identifications of many citizen scientists, and an automated algorithm. We provide a quantitative comparison of the differences between these catalogues and techniques, using 51 CMEs common to each catalogue. The time-elongation profiles of these CME fronts are compared, as are the estimates of the CME kinematics derived from application of three widely used single-spacecraft-fitting techniques. The J-tracker and RAL-HI profiles are most similar, while the Solar Stormwatch profiles display a small systematic offset. Evidence is presented that these differences arise because the RAL-HI and J-tracker profiles follow the sunward edge of CME density enhancements, while Solar Stormwatch profiles track closer to the antisunward (leading) edge. We demonstrate that the method used to produce the time-elongation profile typically introduces more variability into the kinematic estimates than differences between the various single-spacecraft-fitting techniques. This has implications for the repeatability and robustness of these types of analyses, arguably especially so in the context of space weather forecasting, where it could make the results strongly dependent on the methods used by the forecaster.

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Testing the current paradigm for space weather prediction with heliospheric imagers

et al. 2017

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Predictions of the arrival of four coronal mass ejections (CMEs) in geospace are produced through use of three CME geometric models combined with CME drag modeling, constraining these models with the available Coronagraph and Heliospheric Imager data. The efficacy of these predications is assessed by comparison with the Space Weather Prediction Center (SWPC) numerical MHD forecasts of these same events. It is found that such a prediction technique cannot outperform the standard SWPC forecast at a statistically meaningful level. We test the Harmonic Mean, Self‐Similar Expansion, and Ellipse Evolution geometric models, and find that, for these events at least, the differences between the models are smaller than the observational errors. We present a new method of characterizing CME fronts in the Heliospheric Imager field of view, utilizing the analysis of citizen scientists working with the Solar Stormwatch project, and we demonstrate that this provides a more accurate representation of the CME front than is obtained by experts analyzing elongation time maps for the studied events. Comparison of the CME kinematics estimated independently from the STEREO‐A and STEREO‐B Heliospheric Imager data reveals inconsistencies that cannot be explained within the observational errors and model assumptions. We argue that these observations imply that the assumptions of the CME geometric models are routinely invalidated and question their utility in a space weather forecasting context. These results argue for the continuing development of more advanced techniques to better exploit the Heliospheric Imager observations for space weather forecasting.

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

Cited by 8 publications

References 20 publications

Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

Corotating Interaction Regions as Seen by the STEREO Heliospheric Imagers 2007 – 2010

Differences between the CME fronts tracked by an expert, an automated algorithm, and the Solar Stormwatch project

Testing the current paradigm for space weather prediction with heliospheric imagers

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