Properties Of Coronal Mass Ejections Research Articles

MORPHOLOGICAL EVOLUTION OF A THREE-DIMENSIONAL CORONAL MASS EJECTION CLOUD RECONSTRUCTED FROM THREE VIEWPOINTS

The propagation properties of coronal mass ejections (CMEs) are crucial to predict its geomagnetic effect. A newly developed three dimensional (3D) mask fitting reconstruction method using coronagraph images from three viewpoints has been described and applied to the CME ejected on August 7, 2010. The CME's 3D localisation, real shape and morphological evolution are presented. Due to its interaction with the ambient solar wind, the morphology of this CME changed significantly in the early phase of evolution. Two hours after its initiation, it was expanding almost self-similarly. CME's 3D localisation is quite helpful to link remote sensing observations to in situ measurements. The investigated CME was propagating to Venus with its flank just touching STEREO B. Its corresponding ICME in the interplanetary space shows a possible signature of a magnetic cloud with a preceding shock in VEX observations, while from STEREO B only a shock is observed. We have calculated three principle axes for the reconstructed 3D CME cloud. The orientation of the major axis is in general consistent with the orientation of a filament (polarity inversion line) observed by SDO/AIA and SDO/HMI. The flux rope axis derived by the MVA analysis from VEX indicates a radial-directed axis orientation. It might be that locally only the leg of the flux rope passed through VEX. The height and speed profiles from the Sun to Venus are obtained. We find that the CME speed possibly had been adjusted to the speed of the ambient solar wind flow after leaving COR2 field of view and before arriving Venus. A southward deflection of the CME from the source region is found from the trajectory of the CME geometric center. We attribute it to the influence of the coronal hole where the fast solar wind emanated from.

Effect of Solar Wind Drag on the Determination of the Properties of Coronal Mass Ejections from Heliospheric Images

The Fixed-Φ (FΦ) and Harmonic Mean (HM) fitting methods are two methods to determine the “average” direction and velocity of coronal mass ejections (CMEs) from time–elongation tracks produced by Heliospheric Imagers (HIs), such as the HIs onboard the STEREO spacecraft. Both methods assume a constant velocity in their descriptions of the time–elongation profiles of CMEs, which are used to fit the observed time–elongation data. Here, we analyze the effect of aerodynamic drag on CMEs propagating through interplanetary space, and how this drag affects the result of the FΦ and HM fitting methods. A simple drag model is used to analytically construct time–elongation profiles which are then fitted with the two methods. It is found that higher angles and velocities give rise to greater error in both methods, reaching errors in the direction of propagation of up to 15∘ and 30∘ for the FΦ and HM fitting methods, respectively. This is due to the physical accelerations of the CMEs being interpreted as geometrical accelerations by the fitting methods. Because of the geometrical definition of the HM fitting method, it is more affected by the acceleration than the FΦ fitting method. Overall, we find that both techniques overestimate the initial (and final) velocity and direction for fast CMEs propagating beyond 90∘ from the Sun–spacecraft line, meaning that arrival times at 1 AU would be predicted early (by up to 12 hours). We also find that the direction and arrival time of a wide and decelerating CME can be better reproduced by the FΦ due to the cancelation of two errors: neglecting the CME width and neglecting the CME deceleration. Overall, the inaccuracies of the two fitting methods are expected to play an important role in the prediction of CME hit and arrival times as we head towards solar maximum and the STEREO spacecraft further move behind the Sun.

Ensemble prediction model of solar proton events associated with solar flares and coronal mass ejections

An ensemble prediction model of solar proton events (SPEs), combining the information of solar flares and coronal mass ejections (CMEs), is built. In this model, solar flares are parameterized by the peak flux, the duration and the longitude. In addition, CMEs are parameterized by the width, the speed and the measurement position angle. The importance of each parameter for the occurrence of SPEs is estimated by the information gain ratio. We find that the CME width and speed are more informative than the flare's peak flux and duration. As the physical mechanism of SPEs is not very clear, a hidden naive Bayes approach, which is a probability-based calculation method from the field of machine learning, is used to build the prediction model from the observational data. As is known, SPEs originate from solar flares and/or shock waves associated with CMEs. Hence, we first build two base prediction models using the properties of solar flares and CMEs, respectively. Then the outputs of these models are combined to generate the ensemble prediction model of SPEs. The ensemble prediction model incorporating the complementary information of solar flares and CMEs achieves better performance than each base prediction model taken separately.

A Numerical Study of the Response of the Coronal Magnetic Field to Flux Emergence

Large-scale solar eruptions, known as coronal mass ejections (CMEs), are regarded as the main drivers of space weather. The exact trigger mechanism of these violent events is still not completely clear; however, the solar magnetic field indisputably plays a crucial role in the onset of CMEs. The strength and morphology of the solar magnetic field are expected to have a decisive effect on CME properties, such as size and speed. This study aims to investigate the evolution of a magnetic configuration when driven by the emergence of new magnetic flux in order to get a better insight into the onset of CMEs and their magnetic structure. The three-dimensional, time-dependent equations for ideal magnetohydrodynamics are numerically solved on a spherical mesh. New flux emergence in a bipolar active region causes destabilisation of the initial stationary structure, finally resulting in an eruption. The initial magnetic topology is suitable for the ‘breakout’ CME scenario to work. Although no magnetic flux rope structure is present in the initial condition, highly twisted magnetic field lines are formed during the evolution of the system as a result of internal reconnection due to the interaction of the active region magnetic field with the ambient field. The magnetic energy built up in the system and the final speed of the CME depend on the strength of the overlying magnetic field, the flux emergence rate, and the total amount of emerged flux. The interaction with the global coronal field makes the eruption a large-scale event, involving distant parts of the solar surface.

Properties of coronal mass ejections propagating in the heliosphere

Properties of coronal mass ejections propagating in the heliosphere

Coronal Mass Ejections: Observations

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.

Characteristics of CMEs associated with solar flares and DH type II radio bursts based on source position

We studied the characteristics of Coronal Mass Ejections (CMEs) associated with solar flares and Deca-Hectometric (DH) type II radio bursts, based on source position during 23rd solar cycle (1997–2007). We classified these CME events into three groups using solar flare locations as, (i) disk events (0–30∘); (ii) intermediate events (31–60∘) and (iii) limb events (61–90∘). Main results from this studies are, (i) the number of CMEs associated with solar flares and DH-type IIs decreases as the source position approaches from disk to limb, (ii) most of the DH CMEs are halo (72%) in disk events and the number of occurrence of halo CMEs decreases from disk to limb, (iii) the average width and speed of limb events (164∘ and 1447 km s−1) are higher than those of disk events (134∘ and 1035 km s−1) and intermediate events (146∘ and 1170 km s−1) and (iv) the average accelerations for disk, intermediate and limb events are −8.2 m s−2, −10.3 m s−2 and −4.5 m s−2 respectively. These analysis of CMEs properties show more dependency on longitude and it gives strong evidence for projection effect.

Statistical study of coronal mass ejection source locations: 2. Role of active regions in CME production

[1] This is the second paper of the statistical study of coronal mass ejection (CME) source locations, in which the relationship between CMEs and active regions (ARs) is statistically studied on the basis of the information of CME source locations and the ARs automatically extracted from magnetic synoptic charts of Michelson Doppler Imager (MDI) during 1997–1998. Totally, 224 CMEs with a known location and 108 MDI ARs are included in our sample. It is found that about 63% of the CMEs are related with ARs, at least about 53% of the ARs produced one or more CMEs, and particularly about 14% of ARs are CME-rich (3 or more CMEs were generated) during one transit across the visible disk. Several issues are then tried to clarify: whether or not the CMEs originating from ARs are distinct from others, whether or not the CME kinematics depend on AR properties, and whether or not the CME productivity depends on AR properties. The statistical results suggest that (1) there is no evident difference between AR-related and non-AR-related CMEs in terms of CME speed, acceleration and width, (2) the size, strength and complexity of ARs do little with the kinematic properties of CMEs, but have significant effects on the CME productivity, and (3) the sunspots in all the most productive ARs at least belong to βγ type, whereas 90% of those in CME-less ARs are α or β type only. A detailed analysis on CME-rich ARs further reveals that (1) the distribution of the waiting time of same-AR CMEs, consists of two parts with a separation at about 15 hours, which implies that the CMEs with a waiting time shorter than 15 hours are probably truly physical related, and (2) an AR tends to produce such related same-AR CMEs at a pace of 8 hours, but cannot produce two or more fast CMEs (>800 km s−1) within a time interval of 15 hours. This interesting phenomenon is particularly discussed.

Energetic storm particle events in coronal mass ejection-driven shocks

[1] We investigate the variability in the occurrence of energetic storm particle (ESP) events associated with shocks driven by coronal mass ejections (CMEs). The interplanetary shocks were detected during the period from 1996 to 2006. First, we analyze the CME properties near the Sun. The CMEs with an ESP-producing shock are faster (〈VCME〉 = 1088 km/s) than those driving shocks without an ESP event (〈VCME〉 = 771 km/s) and have a larger fraction of halo CMEs (67% versus 38%). The Alfvenic Mach numbers of shocks with an ESP event are on average 1.6 times higher than those of shocks without. We also contrast the ESP event properties and frequency in shocks with and without a type II radio burst by dividing the shocks into radio-loud (RL) and radio-quiet (RQ) shocks, respectively. The shocks seem to be organized into a decreasing sequence by the energy content of the CMEs: RL shocks with an ESP event are driven by the most energetic CMEs, followed by RL shocks without an ESP event, then RQ shocks with and without an ESP event. The ESP events occur more often in RL shocks than in RQ shocks: 52% of RL shocks and only ∼33% of RQ shocks produced an ESP event at proton energies above 1.8 MeV; in the keV energy range the ESP frequencies are 80% and 65%, respectively. Electron ESP events were detected in 19% of RQ shocks and 39% of RL shocks. In addition, we find that (1) ESP events in RQ shocks are less intense than those in RL shocks; (2) RQ shocks with ESP events are predominately quasi-perpendicular shocks; (3) their solar sources are located slightly to the east of the central meridian; and (4) ESP event sizes show a modest positive correlation with the CME and shock speeds. The observation that RL shocks tend to produce more frequently ESP events with larger particle flux increases than RQ shocks emphasizes the importance of type II bursts in identifying solar events prone to producing high particle fluxes in the near-Earth space. However, the trend is not definitive. If there is no type II emission, an ESP event is less likely but not absent. The variability in the probability and size of ESP events most likely reflects differences in the shock formation in the low corona and changes in the properties of the shocks as they propagate through interplanetary space and the escape efficiency of accelerated particles from the shock front.

Studies on some properties of coronal mass ejections based on angular width

We investigated the properties of narrow CMEs (width ≤20°), intermediate CMEs (20° < width < 200°) and wide CMEs (width ≥ 200°) observed during 23rd (1996–1997) and 24th (2008–2009) solar cycle minima and compared their characteristics. We found 1099 narrow CMEs during 24th solar cycle and this is 15 times greater than 23rd solar cycle (75). On the other hand, the number of wide CMEs during 23rd cycle (26) is 6.5 times greater than 24th solar cycle (4) minimum. There is no remarkable difference between the number of intermediate CMEs of 23rd (489) and 24th (506) solar cycle minima. The interesting result is that the CMEs width distributions of the two minima are very different. The median and mean speeds of intermediate CMEs during 24th cycle (195 and 215 km s−1) are smaller than those (256 and 290 km s−1) during 23rd cycle. There is no significant difference in median and mean speeds of narrow and wide CMEs. During 23rd and 24th solar cycle minima we noted (i) 71% and 83% of narrow CMEs, (ii) 81% and 94% of intermediate CMEs and (iii) 46% and 50% of wide CMEs have speed < 400 km s−1, respectively. The maximum CME speeds observed during 23rd and 24th cycle are 1556 km s−1 (wide CME) and 1103 km s−1 (intermediate CME), respectively. We noticed that the speed of 24th solar cycle CMEs is smaller than 23rd solar cycle CMEs. The narrow CMEs are found to be distributed at low and high latitudes in 24th cycle, whereas in 23rd cycle, most of the narrow CMEs occurred around the equator.

CONSTRAINTS ON CORONAL MASS EJECTION EVOLUTION FROM IN SITU OBSERVATIONS OF IONIC CHARGE STATES

We present a novel procedure for deriving the physical properties of coronal mass ejections (CMEs) in the corona. Our methodology uses in situ measurements of ionic charge states of C, O, Si, and Fe in the heliosphere and interprets them in the context of a model for the early evolution of interplanetary CME (ICME) plasma, between 2 and 5 R� . We find that the data are best fit by an evolution that consists of an initial heating of the plasma, followed by an expansion that ultimately results in cooling. The heating profile is consistent with a compression of coronal plasma due to flare reconnection jets and an expansion cooling due to the ejection, as expected from the standard CME/flare model. The observed frozen-in ionic charge states reflect this time history and, therefore, provide important constraints for the heating and expansion timescales, as well as the maximum temperature the CME plasma is heated to during its eruption. Furthermore, our analysis places severe limits on the possible density of CME plasma in the corona. We discuss the implications of our results for CME models and for future analysis of ICME plasma composition.

The inversion of the real kinematic properties of coronal mass ejections by forward modeling

Kinematic properties of coronal mass ejections (CMEs) suffer from projection effects, and it is expected that the real velocity should be larger and the real angular width should be smaller than the apparent values. Several attempts have been taken to correct the projection effects, which however led to an inflated average velocity probably due to the biased choice of CME events. In order to estimate the overall influence of the projection effects on the kinematic properties of the CMEs, we perform a forward modeling of real distributions of CME properties, such as the velocity, the angular width, and the latitude, by requiring their projected distributions to best match observations. Such a matching is conducted by Monte Carlo simulations. According to the derived real distributions, we found that (1) the average real velocity of all non-full-halo CMEs is about 514 km s−1, and the average real angular width is about 33°, in contrast to the corresponding apparent values of 418 km s−1and 42.7° in observations; (2) For the CMEs with the angular width in the range of 20° – 120°, the average real velocity is 510 km s−1and the average real angular width is 43.4°, in contrast to the corresponding apparent values of 392 km s−1and 52° in observations.

COMPREHENSIVE ANALYSIS OF CORONAL MASS EJECTION MASS AND ENERGY PROPERTIES OVER A FULL SOLAR CYCLE

The LASCO coronagraphs, in continuous operation since 1995, have observed the evolution of the solar corona and coronal mass ejections (CMEs) over a full solar cycle with high quality images and regular cadence. This is the first time that such a dataset becomes available and constitutes a unique resource for the study of CMEs. In this paper, we present a comprehensive investigation of the solar cycle dependence on the CME mass and energy over a full solar cycle (1996-2009) including the first in-depth discussion of the mass and energy analysis methods and their associated errors. Our analysis provides several results worthy of further studies. It demonstrates the possible existence of two event classes; 'normal' CMEs reaching constant mass for $>10$ R$_{\sun}$ and 'pseudo' CMEs which disappear in the C3 FOV. It shows that the mass and energy properties of CME reach constant levels, and therefore should be measured, only above $\sim 10 R_\sun$. The mass density ($g/R_\sun^2$) of CMEs varies relatively little ($<$ order of magnitude) suggesting that the majority of the mass originates from a small range in coronal heights. We find a sudden reduction in the CME mass in mid-2003 which may be related to a change in the electron content of the large scale corona and we uncover the presence of a six-month periodicity in the ejected mass from 2003 onwards.

Forward modelling to determine the observational signatures of white-light imaging and interplanetary scintillation for the propagation of an interplanetary shock in the ecliptic plane

Recent coordinated observations of interplanetary scintillation (IPS) from the EISCAT, MERLIN, and STELab, and stereoscopic white-light imaging from the two heliospheric imagers (HIs) onboard the twin STEREO spacecraft are significant to continuously track the propagation and evolution of solar eruptions throughout interplanetary space. In order to obtain a better understanding of the observational signatures in these two remote-sensing techniques, the magnetohydrodynamics of the macro-scale interplanetary disturbance and the radio-wave scattering of the micro-scale electron-density fluctuation are coupled and investigated using a newly constructed multi-scale numerical model. This model is then applied to a case of an interplanetary shock propagation within the ecliptic plane. The shock could be nearly invisible to an HI, once entering the Thomson-scattering sphere of the HI. The asymmetry in the optical images between the western and eastern HIs suggests the shock propagation off the Sun–Earth line. Meanwhile, an IPS signal, strongly dependent on the local electron density, is insensitive to the density cavity far downstream of the shock front. When this cavity (or the shock nose) is cut through by an IPS ray-path, a single speed component at the flank (or the nose) of the shock can be recorded; when an IPS ray-path penetrates the sheath between the shock nose and this cavity, two speed components at the sheath and flank can be detected. Moreover, once a shock front touches an IPS ray-path, the derived position and speed at the irregularity source of this IPS signal, together with an assumption of a radial and constant propagation of the shock, can be used to estimate the later appearance of the shock front in the elongation of the HI field of view. The results of synthetic measurements from forward modelling are helpful in inferring the in-situ properties of coronal mass ejection from real observational data via an inverse approach.

Coronal Shocks Associated with Impulsive and Decaying Phases of Solar Flares

We have analyzed a set of 147 metric Type II radio bursts observed by Culgoora radio spectrograph from November 1997 to December 2006. These events were divided into two sets: The first subset contains Type II events that started during the impulsive phase of the associated solar flares and the second subset contains those starting during the decaying phase of flares. Our main aim is to differentiate the metric Type IIs, flares and coronal mass ejections (CMEs) of these two subsets. It is found that while Type II burst characteristics of both subsets are very similar, there are significant differences between flare and CME properties for these two subsets. Considering all analyzed relationships between the characteristics of Type IIs, flares and CMEs in these two Type II subsets, we conclude that most of the coronal shocks causing metric Type II bursts are driven by CMEs, but that a fraction of events are probably ignited by solar flares.

Characteristics of coronal mass ejection associated with DH type II radio bursts (All and Limb events)

We have studied the characteristics of coronal mass ejections (CMEs) associated with Deca-Hectometric (DH) type II radio bursts (1–14 MHz) in the interplanetary medium during the year 1997–2005. The DH CMEs are divided into two parts: (i) DH CMEs (All) and (ii) DH CMEs (Limb). We found that 65% (177/273) of all events have the speed >900 km s−1 and the remaining 35% (96/273) events have the speed below 900 km s−1. The average speed of all and limb DH CMEs are 1230 and 1288 km s−1, respectively, which is nearly three times the average speed of general population of CMEs (473 km s−1). The average widths of all and limb DH CMEs are 105° and 106°, respectively, which is twice the average width (52°) of the general population of CMEs. We found a better correlation between the speed and width of limb DH CMEs (R=−0.61) than all DH CMEs (R=−0.53). Only 28% (177/637) of fast >900 km s−1 general population of CMEs are reported with DH type II bursts counterpart. The above results gives that the relation between the CME properties is better for limb events.

DETERMINING THE AZIMUTHAL PROPERTIES OF CORONAL MASS EJECTIONS FROM MULTI-SPACECRAFT REMOTE-SENSING OBSERVATIONS WITHSTEREOSECCHI

We discuss how simultaneous observations by multiple heliospheric imagers can provide some important information about the azimuthal properties of Coronal Mass Ejections (CMEs) in the heliosphere. We propose two simple models of CME geometry that can be used to derive information about the azimuthal deflection and the azimuthal expansion of CMEs from SECCHI/HI observations. We apply these two models to four CMEs well-observed by both STEREO spacecraft during the year 2008. We find that in three cases, the joint STEREO-A and B observations are consistent with CMEs moving radially outward. In some cases, we are able to derive the azimuthal cross-section of the CME fronts, and we are able to measure the deviation from self-similar evolution. The results from this analysis show the importance of having multiple satellites dedicated to space weather forecasting, for example in orbits at the Lagrangian L4 and L5 points.

Coronal mass ejection detection using wavelets, curvelets and ridgelets: Applications for space weather monitoring

Coronal mass ejections (CMEs) are large-scale eruptions of plasma and magnetic field that can produce adverse space weather at Earth and other locations in the Heliosphere. Due to the intrinsic multiscale nature of features in coronagraph images, wavelet and multiscale image processing techniques are well suited to enhancing the visibility of CMEs and suppressing noise. However, wavelets are better suited to identifying point-like features, such as noise or background stars, than to enhancing the visibility of the curved form of a typical CME front. Higher order multiscale techniques, such as ridgelets and curvelets, were therefore explored to characterise the morphology (width, curvature) and kinematics (position, velocity, acceleration) of CMEs. Curvelets in particular were found to be well suited to characterising CME properties in a self-consistent manner. Curvelets are thus likely to be of benefit to autonomous monitoring of CME properties for space weather applications.

INTERPLANETARY SHOCKS LACKING TYPE II RADIO BURSTS

We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun–Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (∼34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed ∼535 km s−1) and only ∼40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km s−1 and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration ∼+6.8 m s−2), while those associated with RL shocks were decelerating (average acceleration ∼–3.5 m s−2). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter—hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is predominant in the rise phase and decreases through the maximum and declining phases of solar cycle 23. About 18% of the IP shocks do not have discernible ejecta behind them. These shocks are due to CMEs moving at large angles from the Sun–Earth line and hence are not blast waves. The solar sources of the shock-driving CMEs follow the sunspot butterfly diagram, consistent with the higher-energy requirement for driving shocks.

Tracking of Coronal White-Light Events by Texture

The extraction of the kinematic properties of coronal mass ejections (CMEs) from white-light coronagraph images involves a significant degree of user interaction: defining the edge of the event, separating the core from the front or from nearby unrelated structures, etc. To contribute towards a less subjective and more quantitative definition, and therefore better kinematic characterization of such events, we have developed a novel image-processing technique based on the concept of “texture of the event”. The texture is defined by the so-called gray-level co-occurrence matrix, and the technique consists of a supervised segmentation algorithm to isolate a particular region of interest based upon its similarity with a pre-specified model. Once the event is visually defined early in its evolution, it is possible to automatically track the event by applying the segmentation algorithm to the corresponding time series of coronagraph images. In this paper we describe the technique, present some examples, and show how the coronal background, the core of the event, and even the associated shock (if one exists) can be identified for different kind of CMEs detected by the LASCO and SECCHI coronagraphs.