Tracking Streamer Blobs Into the Heliosphere

Sheeley, N. R.; Rouillard, A. P.

doi:10.1088/0004-637x/715/1/300

Cited by 50 publications

(52 citation statements)

References 23 publications

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“…Similarly, small events are also detected with heliospheric imagers Sheeley and Rouillard, 2010) as well as in the corona, including eruptions from ephemeral regions and narrow CMEs Robbrecht, Berghmans, and Van der Linden, 2009;Schrijver, 2010), blowout Xray jets (Moore et al, 2010(Moore et al, , 2013, and streamer blobs (Wang, Zhang, and Shen, 2009;Sheeley et al, 2009). In parallel, much smaller FRs than typical MCs have been detected with in-situ measurements (Moldwin et al, 2000).…”

Section: Introductionmentioning

confidence: 68%

Are There Different Populations of Flux Ropes in the Solar Wind?

2014

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Flux ropes are twisted magnetic structures, which can be detected by in-situ measurements in the solar wind. However, different properties of detected flux ropes suggest different types of flux-rope population. As such, are there different populations of flux ropes? The answer is positive, and is the result of the analysis of four lists of flux ropes, including magnetic clouds (MCs), observed at 1 AU. The in-situ data for the four lists have been fitted with the same cylindrical force-free model, which provides an estimation of the local flux-rope parameters such as its radius and orientation. Since the flux-rope distributions have a large dynamic range, we go beyond a simple histogram analysis by developing a partition technique that uniformly distributes the statistical fluctuations over the radius range. By doing so, we find that small flux ropes with radius R < 0.1 AU have a steep power-law distribution in contrast to the larger flux ropes (identified as MCs), which have a Gaussian-like distribution. Next, from four CME catalogs, we estimate the expected flux-rope frequency per year at 1 AU. We find that the predicted numbers are similar to the frequencies of MCs observed in-situ. However, we also find that small flux ropes are at least ten times too abundant to correspond to CMEs, even to narrow ones. Investigating the different possible scenarios for the origin of those small flux ropes, we conclude that these twisted structures can be formed by blowout jets in the low corona or in coronal streamers.

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Section: Introductionmentioning

confidence: 68%

Are There Different Populations of Flux Ropes in the Solar Wind?

2014

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“…The convergent shape of each set of tracks is a characteristic of the corotating nature of the global structure (Rouillard et al, 2008); the tracks converge along a 'locus of enhanced visibility', indicated by green arrows (Sheeley and Rouillard, 2010). This locus marks the direction along the line-of-sight that is a tangent to the spiral formed by the series of emitted blobs, i.e.…”

Section: Methodology For Tracking Corotating Density Structuresmentioning

confidence: 99%

“…the CDS (see, e.g. Sheeley and Rouillard, 2010). To determine the time-dependent 3-D location of each CDS we select a single reference track in each pattern, corresponding to a single blob, and fit its trajectory by assuming that it moves radially outward at constant speed (the socalled 'fixed-phi' approximation).…”

Section: Methodology For Tracking Corotating Density Structuresmentioning

confidence: 99%

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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“…While they do not have the full PA coverage of SMEI, their location outside the Earth's magnetosphere removes noise sources that decreased the quality of SMEI images, such as energetic particle saturation from the cusp and South-Atlantic anomaly, glare from the moon, and the aurora. A number of large-scale solar wind transients have been tracked through the SECCHI field of view, including CMEs (e.g., Harrison et al, 2008;Davis et al, 2009;Möstl et al, 2010), corotating interaction regions (e.g., Sheeley Jr et al, 2008;Rouillard et al, 2008;Tappin and Howard, 2009), and solar wind "puffs" (e.g., Rouillard et al, 2010) and "blobs" (e.g., Sheeley Jr et al, 2009;Sheeley Jr and Rouillard, 2010).…”

Section: Heliospheric Imagersmentioning

confidence: 99%

Coronal Mass Ejections: Observations

Webb

Howard

2012

Living Rev. Solar Phys.

670

534

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Solar eruptive phenomena embrace a variety of eruptions, including flares, solar energetic particles, and radio bursts. Since the vast majority of these are associated with the eruption, development, and evolution of coronal mass ejections (CMEs), we focus on CME observations in this review. CMEs are a key aspect of coronal and interplanetary dynamics. They inject large quantities of mass and magnetic flux into the heliosphere, causing major transient disturbances. CMEs can drive interplanetary shocks, a key source of solar energetic particles and are known to be the major contributor to severe space weather at the Earth. Studies over the past decade using the data sets from (among others) the SOHO, TRACE, Wind, ACE, STEREO, and SDO spacecraft, along with ground-based instruments, have improved our knowledge of the origins and development of CMEs at the Sun and how they contribute to space weather at Earth. SOHO, launched in 1995, has provided us with almost continuous coverage of the solar corona over more than a complete solar cycle, and the heliospheric imagers SMEI (2003 -2011) and the HIs (operating since early 2007) have provided us with the capability to image and track CMEs continually across the inner heliosphere. We review some key coronal properties of CMEs, their source regions and their propagation through the solar wind. The LASCO coronagraphs routinely observe CMEs launched along the Sun-Earth line as halo-like brightenings. STEREO also permits observing Earth-directed CMEs from three different viewpoints of increasing azimuthal separation, thereby enabling the estimation of their three-dimensional properties. These are important not only for space weather prediction purposes, but also for understanding the development and internal structure of CMEs since we view their source regions on the solar disk and can measure their in-situ characteristics along their axes. Included in our discussion of the recent developments in CME-related phenomena are the latest developments from the STEREO and LASCO coronagraphs and the SMEI and HI heliospheric imagers.

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Tracking Streamer Blobs Into the Heliosphere

Cited by 50 publications

References 23 publications

Are There Different Populations of Flux Ropes in the Solar Wind?

Are There Different Populations of Flux Ropes in the Solar Wind?

Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging

Coronal Mass Ejections: Observations

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