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

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

doi:10.1007/s11207-015-0759-z

Cited by 6 publications

(8 citation statements)

References 32 publications

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“…CDSs are most clearly imaged in the heliosphere during solar minimum, when the heliospheric images are not too perturbed by the presence of CMEs (Figure 3). Their derived speeds correspond to that of the slow solar wind throughout the solar cycle (Figure 2; see also Conlon et al (2015)). This is in good agreement with the results of analysis of their source regions using a PFSS model, if we relate large expansion factors to slow solar wind speeds (Figure 11) as is commonly done (Wang and Sheeley, 1992;Arge et al, 2002).…”

Section: Discussionsupporting

confidence: 54%

“…We have also found that the predicted arrival time of these structures at 1 AU has an accuracy of about 9 hours for ST-A and 11 hours for ST-B. Since the completion of this work, a paper by Conlon et al (2015) has been published, which studies a smaller sample of 40 CDSs (although obviously they did not use that terminology) also observed in ecliptic J-maps from HI on ST-A between 2007 and 2010. Those authors come to similar conclusions about the propagation speed of CDSs detected by HI being close to the slow solar wind speed.…”

Section: Discussionmentioning

confidence: 77%

“…They also show that accounting for the time-varying separation in ecliptic longitude between the spacecraft and the outflowing transient (φ) in the fitting procedure -in essence taking into consideration the longitudinal drift of the STEREO spacecraft (Equation 2 of their article) -improves the speed predictions by a few tens of km s −1 (Figure 6 of their article). In the present work, this effect was not taken into account and, hence, our technique tends to predict speeds some 20 -30 km s −1 slower than the in situ solar wind values (see Figures 6 and 10) and the speeds derived by Conlon et al (2015) where the same events were considered. We note that the main conclusions presented in this paper are not significantly affected by the non-implementation of this correction (see comparison with the in situ catalog, Section 4.3), but the correction for the angular motion of the satellite will be implemented in upcoming updates to the catalog.…”

Section: Discussionmentioning

confidence: 85%

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Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

et al. 2016

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The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalog listing the properties of 190 corotating structures well-observed in images taken by the Heliospheric Imager (HI) instruments onboard STEREO-A (ST-A). Based on this catalog, we present here one of very few long-term analyses of solar wind structures advected by the background solar wind. We concentrate on the subset of plasma density structures clearly identified inside corotating structures. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be 311 ± 31 km s −1 . Such a low mean value corresponds to the terminal speed of the slow solar wind rather than the speed of stream interfaces, which is typically intermediate between the slow and fast solar wind speeds (∼ 400 km s −1 ). Using our fitting technique, we predicted the arrival time of each corotating density structure at different probes in the inner heliosphere. We find that our derived speeds are systematically lower by ∼ 100 km s −1 than those measured in situ at the predicted impact times. Moreover, for cases when a stream interaction region is clearly detected in situ at the estimated impact time, we find that our derived speeds are lower than the speed of the stream interface measured in situ by an average of 55 km s −1 at ST-A and 84 km s −1 at STEREO-B (ST-B). We show that the speeds of the corotating density structures derived using our fitting technique track well the long-term variation of the radial speed of the slow solar wind during solar minimum years (2007 -2008). Furthermore, we demonstrate that these features originate near the coronal neutral line that eventually becomes the heliospheric current sheet.

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Section: Discussionsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 85%

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Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

et al. 2016

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“…Rouillard et al (2008) showed that plasma parcels entrained into corotation interaction regions (CIRs) could be imaged in HI. Subsequently, Plotnikov et al (2016) tracked many such events in HI images to study the long-term variability of CIRs and whether their arrival at Earth could be predicted from analysis of the HI images, demonstrating that they typically propagate at close to the slow solar wind speed ahead of the CIR, and their arrival near Earth can be predicted with an accuracy of several hours; these results broadly consolidate those from similar but independent studies by Davis et al (2012) and Conlon et al (2015). This line of research was further pursued by Sanchez-Diaz et al (2017), who better quantified the temporal and spatial scales of plasma blobs released into the heliosphere near the heliospheric current sheet.…”

Section: 1029/2019sw002226supporting

confidence: 62%

Extracting Inner‐Heliosphere Solar Wind Speed Information From Heliospheric Imager Observations

et al. 2019

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We present evidence that variability in the STEREO‐A Heliospheric Imager (HI) data is correlated with in situ solar wind speed estimates from WIND, STEREO‐A, and STEREO‐B. For 2008–2012, we compute the variability in HI differenced images in a plane‐of‐sky shell between 20 to 22.5 solar radii and, for a range of position angles, compare daily means of HI variability and in situ solar wind speed estimates. We show that the HI variability data and in situ solar wind speeds have similar temporal autocorrelation functions. Carrington rotation periodicities are well documented for in situ solar wind speeds, but, to our knowledge, this is the first time they have been presented in statistics computed from HI images. In situ solar wind speeds from STEREO‐A, STEREO‐B, and WIND are all are correlated with the HI variability, with a lag that varies in a manner consistent with the longitudinal separation of the in situ monitor and the HI instrument. Unlike many approaches to processing HI observations, our method requires no manual feature tracking; it is automated, is quick to compute, and does not suffer the subjective biases associated with manual classifications. These results suggest we could possibly estimate solar wind speeds in the low heliosphere directly from HI observations. This motivates further investigation, as this could be a significant asset to the space weather forecasting community; it might provide an independent observational constraint on heliospheric solar wind forecasts, through, for example, data assimilation. Finally, these results are another argument for the potential utility of including a HI on an operational space weather mission.

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“…It is now known that CIRs produce an easily recognized signature, particularly in STEREO A imaging data, as the location of the spacecraft to the west of the Sun‐Earth line placed it in a favorable location to observe the developed CIR front far from the Sun, prior to its arrival at Earth [see, e.g., Rouillard et al , ; Tappin and Howard , ; Wood et al , ]. These characteristic CIR signatures appear in a type of representation of SECCHI data known as a “J‐map” [ Davies et al , ], where a lateral slice through an image data cube produces a map of brightness as a function of elongation and time [see Rouillard et al ,, ; Tappin and Howard , ; Conlon et al , for some examples of J‐maps of CIRs]. This has provided a new capability to predict CIR arrivals ahead of their arrival at 1 AU, as workers can observe the development of these signatures in the J‐map hours, and potentially days, ahead of their arrival at 1 AU [e.g., Davis et al , ].…”

Section: Polarization Properties Of Thomson Scattered Lightmentioning

confidence: 99%

The utility of polarized heliospheric imaging for space weather monitoring

et al. 2016

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A polarizing heliospheric imager is a critical next generation tool for space weather monitoring and prediction. Heliospheric imagers can track coronal mass ejections (CMEs) as they cross the solar system, using sunlight scattered by electrons in the CME. This tracking has been demonstrated to improve the forecasting of impact probability and arrival time for Earth‐directed CMEs. Polarized imaging allows locating CMEs in three dimensions from a single vantage point. Recent advances in heliospheric imaging have demonstrated that a polarized imager is feasible with current component technology.Developing this technology to a high technology readiness level is critical for space weather relevant imaging from either a near‐Earth or deep‐space mission. In this primarily technical review, we developpreliminary hardware requirements for a space weather polarizing heliospheric imager system and outline possible ways to flight qualify and ultimately deploy the technology operationally on upcoming specific missions. We consider deployment as an instrument on NOAA's Deep Space Climate Observatory follow‐on near the Sun‐Earth L1 Lagrange point, as a stand‐alone constellation of smallsats in low Earth orbit, or as an instrument located at the Sun‐Earth L5 Lagrange point. The critical first step is the demonstration of the technology, in either a science or prototype operational mission context.

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

Cited by 6 publications

References 32 publications

Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

Extracting Inner‐Heliosphere Solar Wind Speed Information From Heliospheric Imager Observations

The utility of polarized heliospheric imaging for space weather monitoring

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