Observational Tracking of the 2D Structure of Coronal Mass Ejections Between the Sun and 1 AU

Savani, N. P.; Davies, J. A.; Davis, C. J.; Shiota, Daikou; Rouillard, A. P.; Owens, M. J.; Kusano, K.; Bothmer, V.; Bamford, Steven P.; Lintott, Chris; Smith, Arfon M.

doi:10.1007/s11207-012-0041-6

Cited by 26 publications

(28 citation statements)

References 67 publications

(135 reference statements)

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“…Based on the typical error for the distance, the widths have an uncertainty of ±1.2 R . A similar study was recently completed by Savani et al (2009Savani et al ( , 2012 for four CMEs observed by SECCHI. As can be seen in the bottom right panel of Figure 6, the three widths increase with distance, except that the ejecta and total ICME width become constant or start to decrease on May 25 at 00:09 UT.…”

Section: Width Of the First Cmementioning

confidence: 70%

The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined in Situ Measurements and Heliospheric Imaging

Lugaz

Farrugia

Davies

et al. 2012

ApJ

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159

189

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In 2010 May 23-24, Solar Dynamics Observatory (SDO) observed the launch of two successive coronal mass ejections (CMEs), which were subsequently tracked by the SECCHI suite on board STEREO. Using the COR2 coronagraphs and the heliospheric imagers (HIs), the initial direction of both CMEs is determined to be slightly west of the Sun-Earth line. We derive the CME kinematics, including the evolution of the CME expansion until 0.4 AU. We find that, during the interaction, the second CME decelerates from a speed above 500 km s −1 to 380 km s −1 , the speed of the leading edge of the first CME. STEREO observes a complex structure composed of two different bright tracks in HI2-A but only one bright track in HI2-B. In situ measurements from Wind show an "isolated" interplanetary CME, with the geometry of a flux rope preceded by a shock. Measurements in the sheath are consistent with draping around the transient. By combining remote-sensing and in situ measurements, we determine that this event shows a clear instance of deflection of two CMEs after their collision, and we estimate the deflection of the first CME to be about 10• toward the Sun-Earth line. The arrival time, arrival speed, and radius at Earth of the first CME are best predicted from remote-sensing observations taken before the collision of the CMEs. Due to the over-expansion of the CME after the collision, there are few, if any, signs of interaction in in situ measurements. This study illustrates that complex interactions during the Sun-to-Earth propagation may not be revealed by in situ measurements alone.

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Section: Width Of the First Cmementioning

confidence: 70%

The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined in Situ Measurements and Heliospheric Imaging

Lugaz

Farrugia

Davies

et al. 2012

ApJ

Self Cite

159

189

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“…Since r is fixed for a given LAT-map, the equation provides, for each image, the HEEQ longitude corresponding to this height. Equation (10) of Rouillard et al (2009) can be used to convert each latitude/longitude (λ, l) pair into β, A and in Equation (1) of Savani et al (2012) to compute PA,…”

Section: Appendix Coordinatesmentioning

confidence: 99%

The Temporal and Spatial Scales of Density Structures Released in the Slow Solar Wind During Solar Activity Maximum

Sanchez-Diaz

Rouillard

Davies

et al. 2017

ApJ

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In a recent study, we took advantage of a highly tilted coronal neutral sheet to show that density structures, extending radially over several solar radii (R s ), are released in the forming slow solar wind approximately 4-5 R s above the solar surface. We related the signatures of this formation process to intermittent magnetic reconnection occurring continuously above helmet streamers. We now exploit the heliospheric imagery from the Solar Terrestrial Relation Observatory (STEREO) to map the spatial and temporal distribution of the ejected structures. We demonstrate that streamers experience quasi-periodic bursts of activity with the simultaneous outpouring of small transients over a large range of latitudes in the corona. This cyclic activity leads to the emergence of welldefined and broad structures. Derivation of the trajectories and kinematic properties of the individual small transients that make up these large-scale structures confirms their association with the forming slow solar wind (SSW). We find that these transients are released, on average, every 19.5 hr, simultaneously at all latitudes with a typical radial size of 12 R s . Their spatial distribution, release rate, and three-dimensional extent are used to estimate the contribution of this cyclic activity to the mass flux carried outward by the SSW. Our results suggest that, in interplanetary space, the global structure of the heliospheric current sheet is dominated by a succession of blobs and associated flux ropes. We demonstrate this with an example event using STEREO-A in situ measurements.

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“…If deformation is important, the computed magnetic flux could be underestimated, questioning the decreasing magnetic flux calculated for MCs at different solar distances. To compare the circular cross-section approach with deformed cross-sections, we plotted the linear relationship of the radial width and distance to the Sun proposed by Savani et al (2012), W = 0.14R + 0.04 (continuous line in the upper panel of Fig. 9).…”

Section: Forbush Decreases and MC Propertiesmentioning

confidence: 99%

Energetic-particle-flux decreases related to magnetic cloud passages as observed by the Helios 1 and 2 spacecraft

Blanco

Hidalgo

Gómez-Herrero

et al. 2013

A&A

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It has been observed that a magnetic cloud (MC) can affect the propagation conditions of solar energetic particles and low-energy cosmic rays. This effect is commonly observed as a decrease in the energetic-particle fluxes, which are partially excluded from the interior of the cloud. The twin spacecraft Helios 1 and Helios 2 explored the inner heliosphere between 0.29 AU and 1 AU from the mid 1970s to early 1980s. The E6 Experiment onboard Helios is the energetic-particle detector able to measure electrons, protons and alphas in the range of 300 keV/n to >50 MeV/n. It has been shown previously that, in absence of strong solar-particle events, the single detector rates of the E6 anti-coincidence and saphire Cherenkov detectors are sensitive to cosmic rays with rigidities above GV. Because their statistical precision is in the order of hundreds of counts per second, both detectors are very well suited for studying the short-term decreases observed in their count rates during magnetic cloud passages. A total of 35 magnetic clouds have been identified at the Helios locations. Nineteen of them were free of solar energetic-particle contamination. This subset led us to investigate the effect of magnetic clouds on the galactic cosmic ray (GCR) flux. The depth of the decreases are studied in terms of the solar wind and magnetic field properties of the magnetic cloud. We found dependences with the MC magnetic field strength, magnetic rigidity and with the MC time of flight, with the latter supporting the idea of magnetically closed MCs, i.e. with the two legs rooted in the Sun. We also studied MC properties and found evidence of MC expansion during its journey through the inner heliosphere.

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Observational Tracking of the 2D Structure of Coronal Mass Ejections Between the Sun and 1 AU

Cited by 26 publications

References 67 publications

The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined in Situ Measurements and Heliospheric Imaging

The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined in Situ Measurements and Heliospheric Imaging

The Temporal and Spatial Scales of Density Structures Released in the Slow Solar Wind During Solar Activity Maximum

Energetic-particle-flux decreases related to magnetic cloud passages as observed by the Helios 1 and 2 spacecraft

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