C2 Coronagraph Research Articles

Study of solar activities associated with a Halo CME on 17 Feb 2023 event

In the present work, propagation of an earth directed fast and wide Coronal Mass Ejection event on 17 February 2023 is studied in detail. The complex magnetic configuration in the Active Region (AR) 13229 at N25E64 caused an intensive X2.3 flare with a peak at 19:38 UT. It is followed by a massive halo CME event observed in the LASCO C3 coronagraph with a linear speed of 930 km/s and shock speed of 1300 km/s. A low frequency Type II emission was detected in the frequency range 10 MHz – 180 kHz during 20:30 UT-04:45 UT on 18 Feb 2023 by space borne Wind/WAVES instrument. From the OMNI data, the IP shock and the ICME reached earth's magnetosphere on 20 Feb 2023. A fast forward type shock was observed using OMNI high resolution data. The IP shock and ICME affected the Galactic Cosmic ray (GCR) detection. This event caused large magnetic turbulences in sheath region caused a major geomagnetic storm (∼-100 nT).

CAMEL. II. A 3D Coronal Mass Ejection Catalog Based on Coronal Mass Ejection Automatic Detection with Deep Learning

Coronal mass ejections (CMEs) are major drivers of geomagnetic storms, which may cause severe space weather effects. Automating the detection, tracking, and three-dimensional (3D) reconstruction of CMEs is important for operational predictions of CME arrivals. The COR1 coronagraphs on board the Solar Terrestrial Relations Observatory spacecraft have facilitated extensive polarization observations, which are very suitable for the establishment of a 3D CME system. We have developed such a 3D system comprising four modules: classification, segmentation, tracking, and 3D reconstructions. We generalize our previously pretrained classification model to classify COR1 coronagraph images. Subsequently, as there are no publicly available CME segmentation data sets, we manually annotate the structural regions of CMEs using Large Angle and Spectrometric Coronagraph C2 observations. Leveraging transformer-based models, we achieve state-of-the-art results in CME segmentation. Furthermore, we improve the tracking algorithm to solve the difficult separation task of multiple CMEs. In the final module, tracking results, combined with the polarization ratio technique, are used to develop the first single-view 3D CME catalog without requiring manual mask annotation. Our method provides higher precision in automatic 2D CME catalog and more reliable physical parameters of CMEs, including 3D propagation direction and speed. The aforementioned 3D CME system can be applied to any coronagraph data with the capability of polarization measurements.

Effects of coronal mass ejection orientation on its propagation in the heliosphere

Context. In the scope of space weather forecasting, it is crucial to be able to more reliably predict the arrival time, speed, and magnetic field configuration of coronal mass ejections (CMEs). From the time a CME is launched, the dominant factor influencing all of the above is the interaction of the interplanetary CME (ICME) with the ambient plasma and interplanetary magnetic field. Aims. Due to a generally anisotropic heliosphere, differently oriented ICMEs may interact differently with the ambient plasma and interplanetary magnetic field, even when the initial eruption conditions are similar. For this, we examined the possible link between the orientation of an ICME and its propagation in the heliosphere (up to 1 AU). Methods. We investigated 31 CME-ICME associations in the period from 1997 to 2018. The CME orientation in the near-Sun environment was determined using an ellipse-fitting technique applied to single-spacecraft data from SOHO/LASCO C2 and C3 coronagraphs. In the near-Earth environment, we obtained the orientation of the corresponding ICME using in situ plasma and magnetic field data. The shock orientation and nonradial flows in the sheath region for differently oriented ICMEs were investigated. In addition, we calculated the ICME transit time to Earth and drag parameter to probe the overall drag force for differently oriented ICMEs. The drag parameter was calculated using the reverse modeling procedure with the drag-based model. Results. We found a significant difference in nonradial flows for differently oriented ICMEs, whereas a significant difference in drag for differently oriented ICMEs was not found.

Fast Reconstruction of 3D Density Distribution around the Sun Based on the MAS by Deep Learning

This study is the first attempt to generate a three-dimensional (3D) coronal electron density distribution based on the pix2pixHD model, whose computing time is much shorter than that of the magnetohydrodynamic (MHD) simulation. For this, we consider photospheric solar magnetic fields as input, and electron density distribution simulated with the MHD Algorithm outside a Sphere (MAS) at a given solar radius is taken as output. We consider 155 pairs of Carrington rotations as inputs and outputs from 2010 June to 2022 April for training and testing. We train 152 deep-learning models for 152 solar radii, which are taken up to 30 solar radii. The artificial intelligence (AI) generated 3D electron densities from this study are quite consistent with the simulated ones from lower radii to higher radii, with an average correlation coefficient 0.97. The computing time of testing data sets up to 30 solar radii of 152 deep-learning models is about 45.2 s using the NVIDIA TITAN XP graphics-processing unit, which is much less than the typical simulation time of MAS. We find that the synthetic coronagraphic images estimated from the deep-learning models are similar to the Solar Heliospheric Observatory (SOHO)/Large Angle and Spectroscopic Coronagraph C3 coronagraph data, especially during the solar minimum period. The AI-generated coronal density distribution from this study can be used for space weather models on a near-real-time basis.

Predicting CME arrival time through data integration and ensemble learning

The Sun constantly releases radiation and plasma into the heliosphere. Sporadically, the Sun launches solar eruptions such as flares and coronal mass ejections (CMEs). CMEs carry away a huge amount of mass and magnetic flux with them. An Earth-directed CME can cause serious consequences to the human system. It can destroy power grids/pipelines, satellites, and communications. Therefore, accurately monitoring and predicting CMEs is important to minimize damages to the human system. In this study we propose an ensemble learning approach, named CMETNet, for predicting the arrival time of CMEs from the Sun to the Earth. We collect and integrate eruptive events from two solar cycles, #23 and #24, from 1996 to 2021 with a total of 363 geoeffective CMEs. The data used for making predictions include CME features, solar wind parameters and CME images obtained from the SOHO/LASCO C2 coronagraph. Our ensemble learning framework comprises regression algorithms for numerical data analysis and a convolutional neural network for image processing. Experimental results show that CMETNet performs better than existing machine learning methods reported in the literature, with a Pearson product-moment correlation coefficient of 0.83 and a mean absolute error of 9.75 h.

Determination of coronal mass ejection orientation and consequences for their propagation

Context. The configuration of the interplanetary magnetic field and features of the related ambient solar wind in the ecliptic and meridional plane are different. Therefore, one can expect that the orientation of the flux-rope axis of a coronal mass ejection (CME) influences the propagation of the CME itself. However, the determination of the CME orientation, especially from image data, remains a challenging task to perform. Aim. This study aims to provide a reference to different CME orientation determination methods in the near-Sun environment. Also, it aims to investigate the non-radial flow in the sheath region of the interplanetary CME (ICME) in order to provide the first proxy to relate the ICME orientation with its propagation. Methods. We investigated 22 isolated CME-ICME events in the period 2008–2015. We determined the CME orientation in the near-Sun environment using the following: (1) a 3D reconstruction of the CME with the graduated cylindrical shell (GCS) model applied to coronagraphic images provided by the STEREO and SOHO missions; and (2) an ellipse fitting applied to single spacecraft data from SOHO/LASCO C2 and C3 coronagraphs. In the near-Earth environment, we obtained the orientation of the corresponding ICME using in situ plasma and field data and also investigated the non-radial flow in its sheath region. Results. The ability of GCS and ellipse fitting to determine the CME orientation is found to be limited to reliably distinguish only between the high or low inclination of the events. Most of the CME-ICME pairs under investigation were found to be characterized by a low inclination. For the majority of CME-ICME pairs, we obtain consistent estimations of the tilt from remote and in situ data. The observed non-radial flows in the sheath region show a greater y direction to z direction flow ratio for high-inclination events, indicating that the CME orientation could have an impact on the CME propagation.

Tracking the 3D evolution of a halo coronal mass ejection using the revised cone model

Aims. This paper aims to track the three-dimensional (3D) evolution of a full halo coronal mass ejection (CME) on 2011 June 21. Methods. The CME results from a nonradial eruption of a filament-carrying flux rope in NOAA active region 11236. The eruption was observed in extreme-ultraviolet (EUV) wavelengths by the extreme-ultraviolet imager (EUVI) on board the ahead and behind Solar TErrestrial RElations Observatory (STEREO) spacecrafts and the atmospheric imaging assembly (AIA) on board the solar dynamics observatory (SDO). The CME was observed by the COR1 coronagraph on board STEREO and the C2 coronagraph on board the large angle spectroscopic coronagraph (LASCO). The revised cone model was slightly modified, with the top of the cone becoming a sphere, which is internally tangent to the legs. Using the multipoint observations, the cone model was applied to derive the morphological and kinematic properties of the CME. Results. The cone shape fits nicely with the CME observed by EUVI and COR1 on board the STEREO twin spacecraft and LASCO/C2 coronagraph. The cone angle increases sharply from 54° to 130° in the initial phase, indicating a rapid expansion. A relation between the cone angle and the heliocentric distance of the CME leading front is derived, ω = 130° −480d−5, where d is in units of R⊙. The inclination angle decreases gradually from ∼51° to ∼18°, suggesting a trend of radial propagation. The heliocentric distance increases gradually in the initial phase and quickly in the later phase up to ∼11 R⊙. The true speed of the CME reaches ∼1140 km s−1, which is ∼1.6 times higher than the apparent speed in the LASCO/C2 field of view. Conclusions. The revised cone model is promising in tracking the complete evolution of CMEs.

Analysis of signal to noise ratio in coronagraph observations of coronal mass ejections

We establish a baseline signal-to-noise ratio (SNR) requirement for the European Space Agency (ESA)-funded Solar Coronagraph for OPErations (SCOPE) instrument in its field of view of 2.5–30 solar radii based on existing observations by the Solar and Heliospheric Observatory (SOHO). Using automatic detection of coronal mass ejections (CMEs), we anaylse the impacts when SNR deviates significantly from our previously established baseline. For our analysis, SNR values are estimated from observations made by the C3 coronagraph on the Solar and Heliospheric Observatory (SOHO) spacecraft for a number of different CMEs. Additionally, we generate a series of artificial coronagraph images, each consisting of a modelled coronal background and a CME, the latter simulated using the graduated cylindrical shell (GCS) model together with the SCRaytrace code available in the Interactive Data Language (IDL) SolarSoft library. Images are created with CME SNR levels between 0.5 and 10 at the outer edge of the field of view (FOV), generated by adding Poisson noise, and velocities between 700 km s−1 and 2800 km s−1. The images are analysed for the detectability of the CME above the noise with the automatic CME detection tool CACTus. We find in the analysed C3 images that CMEs near the outer edge of the field of view are typically 2% of the total brightness and have an SNR between 1 and 4 at their leading edge. An SNR of 4 is defined as the baseline SNR for SCOPE. The automated detection of CMEs in our simulated images by CACTus succeeded well down to SNR = 1 and for CME velocities up to 1400 km s−1. At lower SNR and higher velocity of ≥ 2100 km s−1 the detection started to break down. For SCOPE, the results from the two approaches confirm that the initial design goal of SNR = 4 would, if achieved, deliver a comparable performance to established data used in operations today, with a more compact instrument design, and a margin in SNR before existing automatic detection produces significant false positives.

Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA

Abstract We present the first results of a solar radio event observed with the Owens Valley Radio Observatory Long Wavelength Array at metric wavelengths. We examine a complex event consisting of multiple radio sources/bursts associated with a fast coronal mass ejection (CME) and an M2.1 GOES soft X-ray flare from 2015 September 20. Images of 9 s cadence are used to analyze the event over a 120 minute period, and solar emission is observed out to a distance of ≈3.5 R ⊙, with an instantaneous bandwidth covering 22 MHz within the frequency range of 40–70 MHz. We present our results from the investigation of the radio event, focusing particularly on one burst source that exhibits outward motion, which we classify as a moving type IV burst. We image the event at multiple frequencies and use the source centroids to obtain the velocity for the outward motion. Spatial and temporal comparison with observations of the CME in white light from the C2 coronagraph of the Large Angle and Spectrometric COronagraph, indicates an association of the outward motion with the core of the CME. By performing graduated-cylindrical-shell reconstruction of the CME, we constrain the density in the volume. The electron plasma frequency obtained from the density estimates do not allow us to completely dismiss plasma emission as the underlying mechanism. However, based on source height and smoothness of the emission in frequency and time, we argue that gyrosynchrotron is the more plausible mechanism. We use gyrosynchrotron spectral-fitting techniques to estimate the evolving physical conditions during the outward motion of this burst source.

The Solar Event of 14\u2009\u2013\u200915 July 2012 and Its Geoeffectiveness

During Solar Cycle 24, which started at the end of 2008, the Sun was calm, and there were not many spectacular geoeffective events. In this article, we analyze the geomagnetic storm that happened on 15 July 2012 during the 602nd anniversary of the Polish Battle of Grunwald, thus we propose this event to be called the “Battle of Grunwald Day Storm”. According to NOAA scale, it was a G3 geomagnetic storm with a southward component of the heliospheric magnetic field, Bz, falling to −20 nT, minimum Dst index of −139 nT, AE index of 1368 nT, and Ap index of 132 nT. It was preceded by a solar flare class X1.4 on 12 July. This geomagnetic storm was associated with the fast halo coronal mass ejection at 16:48:05 UT on 12 July, first appearance in the Large Angle and Spectroscopic Coronagraph C2, with a plane-of-sky speed of 885 km s−1 and maximum of 1415 km s−1. This geomagnetic storm was classified as the fourth strongest geomagnetic storm of Solar Cycle 24. At that time, a significant growth in the failures of the Polish electric transmission lines was observed, which could have a solar origin.

Compositing Eclipse Images from the Ground and from Space

Abstract We present composite white-light images of the 2019 July 2, total solar eclipse, from the minimum of the solar-activity cycle. We exhibit high-resolution high dynamic range composites from three observation sites in Chile, including one made of 646 individual ground-based images and with such a wide field it exceeds the field of view of the Naval Research Laboratory’s C2 and C3 coronagraphs aboard ESA’s Solar and Heliospheric Observatory. We compare the resolution of the coronal streamers and other magnetic phenomena of the corona. We also show continuity of features on the solar surface as observed from NOAA’s GOES-16 and GOES-17 Solar Ultraviolet Imager.

Properties of Streamer Wave Events Observed during the STEREO Era

Abstract Transverse waves are sometimes observed in solar helmet streamers, typically after the passage of a coronal mass ejection (CME). The CME-driven shock wave moves the streamer sideways, and a decaying oscillation of the streamer is observed after the CME passage. Previous works generally reported observations of streamer oscillations taken from a single vantage point (typically the Solar and Heliospheric Observatory (SOHO) spacecraft). We conduct a data survey searching for streamer wave events observed by the COR2 coronagraphs on board the STEREO spacecraft. For the first time, we report observations of streamer wave events from multiple vantage points by using the COR2 instrument on both STEREO A and B, as well as the SOHO/LASCO C2+C3 coronagraphs. We investigate the properties of streamer waves by comparing the different events and performing a statistical analysis. Common observational features give us additional insight on the physical nature of streamer wave events. The most important conclusion is that there appears to be no relation between the speed of the CME and the phase speed of the resulting streamer wave, indicating that the streamer wave speed is determined by the physical properties of the streamer rather than the properties of the CME. This result makes streamer wave events excellent candidates for coronal seismology studies. From a comparison between the measured phase speeds and the phase speeds calculated from the measured periods and wavelengths, we could determine that the speed of the postshock solar wind flow in our streamers is around 300 km s−1.

Enhancing coronal structures with radial local multi-scale filter

Images of the corona contain information over a wide range of spatial scales and various structures such as coronal holes, coronal loops, coronal mass ejections (CMEs), and helmet streamers with differences in brightness. Therefore, processing these images is important for determining various types of information. However, it is very difficult to elucidate the intricate structure of the corona because of the steep radial gradient in terms of brightness and the large differences in brightness within local areas of coronal images. In this study, we present a filter inspired by the normalizing-radial-graded filter, which we call the radial local multi-scale filter (RLMF). The RLMF method extracts radial vectors and performs local multi-scale filtering based on each vector, before normalizing the vector in order to enhance coronal images. This method facilitates the enhancement of large-scale structural characteristics and fine details in low contrast regions. To demonstrate the power of the RLMF, we applied the proposed method to Large Angle and Spectrometric Coronagraph C2 and K-Coronagraph observations. The RLMF method more clearly revealed the fine details of the corona and CMEs compared with the original observations.

Comparing the Features of Generation of CMEs Moving with Different Speed in the Field of View of the LASCO Coronagraphs

This study is aimed at finding an answer to the following question: are there any fundamental differences in the generation of coronal mass ejections (CMEs) with different speeds, especially low and high speeds, detected in the field of view of LASCO coronagraphs? Fast CMEs are conventionally understood as mass ejections with a linear projection velocity in LASCO field of view $${{V}_{{LIN}}}$$ > 1500 km/s; slow CMEs are those with $${{V}_{{LIN}}}$$ ≤ 600 km/s. CMEs with $${{V}_{{LIN}}}$$ between 600 and 1500 km/s are referred to as mass ejections with intermediate speed. The results of the analysis are presented by the example of three halo-type CME events (fast, slow, and intermediate) with sources in the sunspot groups removed from the center of the solar disk by no more than 45°. For analysis, we used data from SDO/AIA telescopes and the SDO/HMI instrument, as well as the LASCO C2 and C3 coronagraphs. The properties of active regions in which CMEs with different speeds have occurred are compared. The morphological features of the formation of the selected mass ejections based on the observations in the extreme ultraviolet lines are compared with features of their kinematics. Using the data of vector measurements of the photospheric magnetic field with the SDO/HMI instrument over the regions of CME formation, the altitude distributions of the magnetic field are calculated in the nonlinear force-free approximation. The analysis of these distributions showed that before the onset of a CME-related flare, the rate of altitude variation in the magnetic field above the CME generation site is noticeably different for all selected events.

Global Oscillations of the Sun according to SOHO/LASCO C3 Coronagraph Data

Long-period oscillations in the brightness of the Sun as a star have been analyzed on the basis of measurements of the solar light reflected by planets when they come into the field of view of the Large Angle and Spectrometric Coronagraph (LASCO C3) onboard the Solar and Heliospheric Observatory (SOHO). We took sequences of FITS intensitygrams from the archive of the SOHO/LASCO C3 space observatory for the observational data; they were 1024 × 1024 pixels in size, and they were acquired with the 12-min interval. In 5-day continuous time series of the brightness of Mars and Jupiter, coinciding modes of 8–10 and 36–38 h were found. This coincidence apparently indicates their solar origin. In addition, for Mars, we obtained 25-day series of time variations of the reflected solar radiation, in which a mode with even a lower frequency of 8–10 days was detected.

Comparison of Features of the Generation of Coronal Mass Ejections with Variable Velocity in the Field of View of LASCO Coronagraphs

This paper compares features of the generation of coronal mass ejections (CMEs) with the lowest, intermediate, and highest velocities in the field of view of LASCO C2 and C3 coronagraphs found from an analysis of multi-wavelength data with high temporal and spatial resolution. The dynamics of the field characteristics in the umbra of sunspots of active regions (ARs) in which variable-velocity CMEs occur are compared based on SDO/HMI vector magnetic field measurements. It is found that there are almost no noticeable changes in field characteristics in the AR sunspots in which slow CMEs occur after the onset of the eruptive event. However, there are noticeable changes in the field intensity and inclination angles of the flux tube emerging from the umbra of the sunspot in some AR sunspots in which CMEs occur after the onset of the eruptive event. Thus, for the fast CME detected on January 7, 2014, the inclination angle of the flux tube from the umbra of one of the sunspots before the flare onset reached a maximum value of ≈4°. After the flare onset, it was less than 1°.

Fine-scale structure in cometary dust tails I: Analysis of striae in Comet C/2006 P1 (McNaught) through temporal mapping

Striated features, or striae, form in cometary dust tails due to an as-yet unconstrained process or processes. For the first time we directly display the formation of striae, at C/2006 P1 McNaught, using data from the SOHO LASCO C3 coronagraph. The nature of this formation suggests both fragmentation and shadowing effects are important in the formation process. Using the SOHO data with STEREO-A and B data from the HI-1 and HI-2 instruments, we display the evolution of these striae for two weeks, with a temporal resolution of two hours or better. This includes a period of morphological change on 2007 January 13–14 that we attribute to Lorentz forces caused by the comet’s dust tail crossing the heliospheric current sheet. The nature of this interaction also implies a mixing of different sized dust along the striae, implying that fragmentation must be continuous or cascading. To enable this analysis, we have developed a new technique – temporal mapping – that displays cometary dust tails directly in the radiation beta (ratio of radiation pressure to gravity) and dust ejection time phase space. This allows for the combination of various data sets and the removal of transient motion and scaling effects.

Periodic behaviour of coronal mass ejections, eruptive events, and solar activity proxies during solar cycles 23 and 24

We report on the parallel analysis of the periodic behaviour of coronal mass ejections (CMEs) based on 21 years [1996–2016] of observations with the SOHO/LASCO–C2 coronagraph, solar flares, prominences, and several proxies of solar activity. We consider values of the rates globally and whenever possible, distinguish solar hemispheres and solar cycles 23 and 24. Periodicities are investigated using both frequency (periodogram) and time-frequency (wavelet) analysis. We find that these different processes, in addition to following the ≈11-year Solar Cycle, exhibit diverse statistically significant oscillations with properties common to all solar, coronal, and heliospheric processes: variable periodicity, intermittence, asymmetric development in the northern and southern solar hemispheres, and largest amplitudes during the maximum phase of solar cycles, being more pronounced during solar cycle 23 than the weaker cycle 24. However, our analysis reveals an extremely complex and diverse situation. For instance, there exists very limited commonality for periods of less than one year. The few exceptions are the periods of 3.1–3.2 months found in the global occurrence rates of CMEs and in the sunspot area (SSA) and those of 5.9–6.1 months found in the northern hemisphere. Mid-range periods of ≈1 and ≈2 years are more wide spread among the studied processes, but exhibit a very distinct behaviour with the first one being present only in the northern hemisphere and the second one only in the southern hemisphere. These periodic behaviours likely results from the complexity of the underlying physical processes, prominently the emergence of magnetic flux.

Auto-detection of Halo CME Parameters as the Initial Condition of Solar Wind Propagation

Halo coronal mass ejections (CMEs) originating from solar activities give rise to geomagnetic storms when they reach the Earth. Variations in the geomagnetic field during a geomagnetic storm can damage satellites, communication systems, electrical power grids, and power systems, and induce currents. Therefore, automated techniques for detecting and analyzing halo CMEs have been eliciting increasing attention for the monitoring and prediction of the space weather environment. In this study, we developed an algorithm to sense and detect halo CMEs using large angle and spectrometric coronagraph (LASCO) C3 coronagraph images from the solar and heliospheric observatory (SOHO) satellite. In addition, we developed an image processing technique to derive the morphological and dynamical characteristics of halo CMEs, namely, the source location, width, actual CME speed, and arrival time at a 21.5 solar radius. The proposed halo CME automatic analysis model was validated using a model of the past three halo CME events. As a result, a solar event that occurred at 03:38 UT on Mar. 23, 2014 was predicted to arrive at Earth at 23:00 UT on Mar. 25, whereas the actual arrival time was at 04:30 UT on Mar. 26, which is a difference of 5 hr and 30 min. In addition, a solar event that occurred at 12:55 UT on Apr. 18, 2014 was estimated to arrive at Earth at 16:00 UT on Apr. 20, which is 4 hr ahead of the actual arrival time of 20:00 UT on the same day. However, the estimation error was reduced significantly compared to the ENLIL model. As a further study, the model will be applied to many more events for validation and testing, and after such tests are completed, on-line service will be provided at the Korean Space Weather Center to detect halo CMEs and derive the model parameters.

Inflows in the Inner White-light Corona: The Closing-down of Flux after Coronal Mass Ejections

Abstract During times of high solar activity, the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph C2 coronagraph has recorded multitudes of small features moving inward through its field of view. These outer-coronal inflows, which are concentrated around the heliospheric current sheet, tend to be poorly correlated with individual coronal mass ejection (CME) events. Using running-difference movies constructed from Solar Terrestrial Relations Observatory/COR1 coronagraph images taken during 2008–2014, we have identified large numbers of inward-moving features at heliocentric distances below , with the rate increasing with sunspot and CME activity. Most of these inner-coronal inflows are closely associated with CMEs, being observed during and in the days immediately following the eruptions. Here, we describe several examples of the pinching-off of tapered streamer structures in the wake of CMEs. This type of inflow event is characterized by a separation of the flow into incoming and outgoing components connected by a thin spike, which is interpreted as a continually elongating current sheet viewed edge-on; by the prior convergence of narrow rays toward the current sheet; and by a succession of collapsing loops that form a cusp-shaped structure at the base of the current sheet. The re-forming streamer overlies a growing post-eruption arcade that is visible in EUV images. These observations provide support for standard reconnection models for the formation/evolution of flux ropes during solar eruptive events. We suggest that inflow streams that occur over a relatively wide range of position angles result from the pinching-off of loop arcades whose axes are oriented parallel rather than perpendicular to the sky plane.