V arc interplanetary coronal mass ejections observed with the Solar Mass Ejection Imager

Kahler, S. W.; Webb, D. F.

doi:10.1029/2007ja012358

Cited by 109 publications

(122 citation statements)

References 43 publications

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“…If the results suggesting a circular cross section are to be believed then the question to ask is, how can this be true while the CME still propagates radially away from the Sun? One possible solution is to appreciate that a CME should not be treated as a solid object travelling through a plasma, but an object that may interact and be distorted by its surroundings (Kahler & Webb 2007). Using the inner HI camera on STEREO-A, Savani et al (2010) monitored the distorting of a CME's leading edge into a concave shape.…”

Section: Discussionmentioning

confidence: 99%

Evolution of Coronal Mass Ejection Morphology With Increasing Heliocentric Distance. Ii. In Situ Observations

Savani

Owens

Rouillard

et al. 2011

ApJ

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Interplanetary coronal mass ejections (ICMEs) are often observed to travel much faster than the ambient solar wind. If the relative speed between the two exceeds the fast magnetosonic velocity, then a shock wave will form. The Mach number and the shock standoff distance ahead of the ICME leading edge is measured to infer the vertical size of an ICME in a direction that is perpendicular to the solar wind flow. We analyze the shock standoff distance for 45 events varying between 0.5 AU and 5.5 AU in order to infer their physical dimensions. We find that the average ratio of the inferred vertical size to measured radial width, referred to as the aspect ratio, of an ICME is 2.8 ± 0.5. We also compare these results to the geometrical predictions from Paper I that forecast an aspect ratio between 3 and 6. The geometrical solution varies with heliocentric distance and appears to provide a theoretical maximum for the aspect ratio of ICMEs. The minimum aspect ratio appears to remain constant at 1 (i.e., a circular cross section) for all distances. These results suggest that possible distortions to the leading edge of ICMEs are frequent. But, these results may also indicate that the constants calculated in the empirical relationship correlating the different shock front need to be modified; or perhaps both distortions and a change in the empirical formulae are required.

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Section: Discussionmentioning

confidence: 99%

Evolution of Coronal Mass Ejection Morphology With Increasing Heliocentric Distance. Ii. In Situ Observations

Savani

Owens

Rouillard

et al. 2011

ApJ

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“…This is also known as the fixed-φ (FP) approximation (Kahler & Webb 2007). These definitions are visualized in Figure 1.…”

Section: Fixed-φ and Harmonic Meanmentioning

confidence: 99%

ARRIVAL TIME CALCULATION FOR INTERPLANETARY CORONAL MASS EJECTIONS WITH CIRCULAR FRONTS AND APPLICATION TOSTEREOOBSERVATIONS OF THE 2009 FEBRUARY 13 ERUPTION

Möstl

Rollett

Lugaz

et al. 2011

ApJ

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One of the goals of the NASA Solar TErestrial RElations Observatory (STEREO) mission is to study the feasibility of forecasting the direction, arrival time, and internal structure of solar coronal mass ejections (CMEs) from a vantage point outside the Sun-Earth line. Through a case study, we discuss the arrival time calculation of interplanetary CMEs (ICMEs) in the ecliptic plane using data from STEREO/SECCHI at large elongations from the Sun in combination with different geometric assumptions about the ICME front shape [fixed-Φ (FP): a point and harmonic mean (HM): a circle]. These forecasting techniques use single-spacecraft imaging data and are based on the assumption of constant velocity and direction. We show that for the slow (350 km s −1 ) ICME on 2009 February 13-18, observed at quadrature by the two STEREO spacecraft, the results for the arrival time given by the HM approximation are more accurate by 12 hr than those for FP in comparison to in situ observations of solar wind plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by 6 hr for the arrival time at Venus Express (MAG). We propose that the improvement is directly related to the ICME front shape being more accurately described by HM for an ICME with a low inclination of its symmetry axis to the ecliptic. In this case, the ICME has to be tracked to >30 • elongation to obtain arrival time errors <± 5 hr. A newly derived formula for calculating arrival times with the HM method is also useful for a triangulation technique assuming the same geometry.

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“…It is possible to fit time-elongation profiles using Equation (1) in order to extract the best-fit values of V r and φ that correspond to that profile (Rouillard et al, 2008). This technique is termed fixed-φ fitting (Kahler and Webb, 2007). A single CIR as imaged by HI results in a family of time-elongation profiles, each corresponding to (it is surmised) an individual blob entrained at the stream interface.…”

Section: Remote Cir Observations From Stereomentioning

confidence: 99%

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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V arc interplanetary coronal mass ejections observed with the Solar Mass Ejection Imager

Cited by 109 publications

References 43 publications

Evolution of Coronal Mass Ejection Morphology With Increasing Heliocentric Distance. Ii. In Situ Observations

Evolution of Coronal Mass Ejection Morphology With Increasing Heliocentric Distance. Ii. In Situ Observations

ARRIVAL TIME CALCULATION FOR INTERPLANETARY CORONAL MASS EJECTIONS WITH CIRCULAR FRONTS AND APPLICATION TOSTEREOOBSERVATIONS OF THE 2009 FEBRUARY 13 ERUPTION

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

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