Since Coronal Mass Ejections (CMEs) are the major drivers of space weather, it is crucial to study their evolution starting from the inner corona. In this work we use Graduated Cylindrical Shell (GCS) model to study the 3D evolution of 59 CMEs in the inner (< 3R ) and outer (> 3R ) corona using observations from COR-1 and COR-2 on-board Solar TErrestrial RElations Observatory (STEREO) spacecraft. We identify the source regions of these CMEs and classify them as CMEs associated with Active Regions (ARs), Active Prominences (APs), and Prominence Eruptions (PEs). We find 27 % of CMEs show true expansion and 31 % show true deflections as they propagate outwards. Using 3D kinematic profiles of CMEs, we connect the evolution of true acceleration with the evolution of true width in the inner and outer corona. Thereby providing the observational evidence for the influence of the Lorentz force on the kinematics to lie in the height range of 2.5 − 3 R . We find a broad range in the distribution of peak 3D speeds and accelerations ranging from 396 to 2465 km s −1 and 176 to 10922 m s −2 respectively with a long tail towards high values coming mainly from CMEs originating from ARs or APs. Further, we find the magnitude of true acceleration is be inversely correlated to its duration with a power law index of -1.19. We believe that these results will provide important inputs for the planning of upcoming space missions which will observe the inner corona and the models that study CME initiation and propagation.

Coronal Mass Ejections (CMEs) are highly dynamic events originating in the solar atmosphere, that show a wide range of kinematic properties and are the major drivers of the space weather. The angular width of the CMEs is a crucial parameter in the study of their kinematics. The fact that whether slow and fast CMEs (as based on their relative speed to the average solar wind speed) are associated with different processes at the location of their ejection is still debatable. Thus, in this study, we investigate their angular width to understand the differences between the slow and fast CMEs. We study the width distribution of slow and fast CMEs and find that they follow different power law distributions, with a power law indices (α) of –1.1 and –3.7 for fast and slow CMEs respectively. To reduce the projection effects, we further restrict our analysis to only limb events as derived from manual catalog and we find similar results. We then associate the slow and fast CMEs to their source regions, and classified the sources as Active Regions (ARs) and Prominence Eruptions. We find that slow and fast CMEs coming from ARs and PEs, also follow different power laws in their width distributions. This clearly hints toward a possibility that different mechanisms might be involved in the width expansion of slow and fast CMEs coming from different sources.These results are also crucial from the space weather perspective since the width of the CME is an important factor in that aspect.

Context. Coronal mass ejections (CMEs) are often observed to be accompanied by flare, current sheets, and plasmoids/plasma blobs. 2D and 3D numerical simulations and observations reported plasmoids moving upward as well as downward along the current sheet. Aims. We aim to investigate the properties of plasmoids observed in the current sheet formed after an X-8.3 flare and followed by a fast CME eruption on September 10, 2017 using extreme-ultraviolet (EUV) and white-light coronagraph images. The main goal is to understand the evolution of plasmoids in different spatio-temporal scales using existing ground- and space-based instruments. Methods. We identified the plasmoids manually and tracked them along the current sheet in the successive images of Atmospheric Imaging Assembly (AIA) taken at the 131 Å pass band and in running difference images of the white-light coronagraphs, K-Cor and LASCO/C2. The location and size of the plasmoids in each image were recorded and analyzed, covering the current sheet from the inner to outer corona. Results. We find that the observed current sheet has an Alfvén Mach number of 0.018−0.35. The fast reconnection is also accompanied by plasmoids moving upward and downward. We identified 20 downward-moving and 16 upward-moving plasmoids using AIA 131 Å images. In white-light coronagraph images, only upward-moving plasmoids are observed. Our analysis shows that the downward-moving plasmoids have an average width of 5.92 Mm, whereas upward-moving blobs have an average size of 5.65 Mm in the AIA field of view (FOV). The upward-moving plasmoids, when observed in the white-light images, have an average width of 64 Mm in the K-Cor, which evolves to a mean width of 510 Mm in the LASCO/C2 FOV. Upon tracking the plasmoids in successive images, we find that downward- and upward-moving plasmoids have average speeds of ∼272 km s−1 and ∼191 km s−1, respectively in the EUV channels of observation. The average speed of plasmoids increases to ∼671 km s−1 and ∼1080 km s−1 in the K-Cor and LASCO/C2 FOVs, respectively, implying that the plasmoids become super-Alfvénic when they propagate outward. The downward-moving plasmoids show an acceleration in the range of −11 km s−1 to over 8 km s−1. We also find that the null point of the current sheet is located at ≈1.15 R⊙, where bidirectional plasmoid motion is observed. Conclusions. The width distribution of plasmoids formed during the reconnection process is governed by a power law with an index of −1.12. Unlike previous studies, there is no difference in trend for small- and large-scale plasmoids. The evolution of width W of the plasmoids moving at an average speed V along the current sheet is governed by an empirical relation: V = 115.69W0.37. The presence of accelerating plasmoids near the neutral point indicates a longer diffusion region as predicted by MHD models.

Solar eruptions such as Coronal Mass Ejections (CMEs) observed in the inner solar corona (up to 4 R ) show acceleration profiles which appear as parabolic ridges in height-time plots. Inspired by the white-light automated detection algorithms, Computer Aided CME Tracking System (CACTus) and So-R.

ADITYA-L1 is India's first space mission to study the Sun from Lagrangian 1 position. Visible Emission Line Coronagraph (VELC) is one of the seven payloads in ADITYA-L1 mission scheduled to be launched around 2020. One of the primary objectives of the VELC is to study the dynamics of coronal mass ejections (CMEs) in the inner corona. This will be accomplished by taking high resolution (≈ 2.51 arcsec pixel −1 ) images of corona from 1.05 R -3 R at high cadence of 1 s in 10Å passband centered at 5000Å. Due to limited telemetry at Lagrangian 1 position we plan to implement an onboard automated CME detection algorithm. The detection algorithm is based on the intensity thresholding followed by the area thresholding in successive difference images spatially re-binned to improve signal to noise ratio. We present the results of the application of this algorithm on the data from existing coronagraphs such as STEREO/SECCHI COR-1, which is space based coronagraph, and K-Cor, a ground based coronagraph, because they have field of view (FOV) nearest to VELC. Since, no existing space-based coronagraph has FOV similar to VELC, we have created synthetic coronal images for VELC FOV after including photon R. Patel ritesh.patel@iiap.res.in V. Pant vaibhav@iiap.res.in Amareswari K. Patel R. et al.noise and injected CMEs of different types. The performance of CME detection algorithm is tested on these images. We found that for VELC images, the telemetry can be reduced by a factor of 85% or more keeping CME detection rate of 70% or above at the same time. Finally, we discuss the advantages and disadvantages of this algorithm. The application of such onboard algorithm in future will enable us to take higher resolution images with improved cadence from space and also reduce the load on limited telemetry at the same time. This will help in better understanding of CMEs by studying their characteristics with improved spatial and temporal resolutions.

Some of the major challenges faced in understanding the early evolution of coronal mass ejections (CMEs) are due to the limited observations in the inner corona (<3 R ⊙) and the plane-of-sky measurements. In this work, we have thus extended the application of the Graduated Cylindrical Shell (GCS) model to inner coronal observations from the ground-based coronagraph K-Cor of the Mauna Loa Solar Observatory, along with the pairs of observations from COR-1 on board the Solar Terrestrial Relations Observatory. We study the rapid initial acceleration and width expansion phases of five CMEs in white light at the lower heights. We also study the evolution of the modeled volumes of these CMEs in the inner corona and report, for the first time, a power-law dependence of CME volume with distance from the Sun. We further find that the volumes of the ellipsoidal leading front and the conical legs follow different power laws, thus indicating differential volume expansion throughout a CME. The study also reveals two distinct power laws for the total volume evolution of CMEs in the inner and outer corona, thus suggesting different expansion mechanisms at these different heights. Besides aiding our current understanding of CME evolution, these results will also provide better constraints to CME initiation and propagation models. Also, given the loss of the STEREO-B (and hence COR-1B data) from 2016, the modified GCS model presented here will still enable stereoscopy in the inner corona for the 3D study of CMEs in white light.

Despite studying coronal mass ejections (CMEs) for several years, we do not yet have a complete understanding of their kinematics. To this end, it is essential to understand the change in kinematics of the CMEs as they travel from the inner corona (<3 R ⊙) up to the higher heights of the outer corona. We conduct a follow-up statistical study of several 3D kinematic parameters of 59 CMEs previously studied by Majumdar et al. (2020). The source regions of these CMEs are identified and classified as active regions (ARs), active prominences (APs), or prominence eruptions (PEs). We study several statistical correlations between different kinematic parameters of the CMEs. We show that the CMEs’ average kinematic parameters change as they propagate from the inner to the outer corona, indicating the importance of a region where the common practice is to perform averaging. We also find that the CME parameters in the outer corona are highly influenced by those in the inner corona, indicating the importance of the inner corona in the understanding of the kinematics. Furthermore, we find that the source regions of the CMEs tend to have a distinct imprint on the statistical correlations between different kinematic parameters, and that an overall correlation tends to wash away this crucial information. The results of this work supports the possibility of different dynamical classes for the CMEs from ARs and prominences, which gets manifested in their kinematics.

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