Coronal Mass Ejections Height Research Articles

A Statistical Analysis of Deflection of Coronal Mass Ejections in the Field of View of LASCO Coronagraphs

Coronal mass ejections (CMEs) can generate the most severe geomagnetic disturbances. One of the most critical factors affecting a CME’s geoeffectiveness is its trajectory. It is crucial to determine whether and when CME will hit Earth. It is commonly assumed that CMEs experience a deflection of propagation in the corona and in interplanetary space. In this study, we analyze more than 14,000 CMEs listed in the Coordinate Data Analysis Workshop (CDAW) catalog during 1996–2022 to estimate their deflection in the Large and Spectrometric Coronagraph field of view (LFOV). In our statistical analysis, the deflection was determined using the CME height–time measurements listed in the CDAW catalog. We have shown that, in the solar corona, CME deflection is a common phenomenon, heavily influenced by solar activity cycles as well as phases of these cycles. We have demonstrated that during periods of solar activity minima the deflection of CMEs is mostly toward the equator, and during periods of maxima it is mostly toward the poles. This general trend of deflection is further modified by the specific structure of the magnetic field generated during successive cycles of solar activity (e.g., the asymmetry between the hemispheres). A systematic increase in deflection with time was also recognized. We have also found that the deflection increases linearly with the distance from the Sun in the LFOV (the line slope is 0.5).

Properties of High-Frequency Type II Radio Bursts and Their Relation to the Associated Coronal Mass Ejections

Solar radio bursts are often early indicators of space weather events such as coronal mass ejections (CMEs). In this study, we determined the properties of a sample of 40 high-starting-frequency (≥ 150 MHz) type II radio bursts and the characteristics of the associated CMEs such as width, location and speed during 2010–2016. The high starting frequency implies shock formation closer to the solar surface, which has important ramifications for the analysis of particle acceleration near the Sun. We found the CME heliocentric distances at the onset time of metric type II bursts range from 1.16 to 1.90 solar radii (Rs). The study was also extended to 128 metric type II bursts to include lower-starting-frequency events for further analysis. The projected CME heights range from 1.15 to 2.85 Rs. The lower starting frequency correspond to shocks forming at larger heights. A weak correlation was found between the type-II starting frequency and CME heights, which is consistent with the density decline in the inner corona. The analysis confirmed a good correlation between the drift rate and the starting frequency of type II bursts (correlation coefficient ∼ 0.8). Taking into account the radial variation of CMEs speeds from the inner corona to the interplanetary medium, we observed the deviations from the universal drift-rate spectrum of type II bursts and confirmed the previous results relating type II bursts to CMEs.

Spatial Organization of Seven Extreme Solar Energetic Particle Events

Abstract Emission of relativistic protons and helium responsible for extreme solar particle events (ground level enhancements (GLEs)) is often structured. We investigate its organization depending on the eruption stage characterized by the heliocentric height of associated coronal mass ejections (CMEs). Seven GLEs are considered: events on 1997 November 6, 1998 May 2, 2000 July 14, 2001 December 26, 2003 November 2, 2006 December 13, and 2012 May 17, which are half of the SOlar and Heliospheric Observatory (SOHO )-era GLEs, excluding very weak events. Count-rate profiles of the GLEs plotted as a function of the CME height reveal two types (or two components) of the high-energy particle emission. The first component rises in a step-like manner during the CME transit from 2 R ⊙ to 3 R ⊙, when the CME exits from predominantly closed coronal magnetic structures, irrespective of the CME speed (type H). This component is of coronal origin. The second component of the GLE-producing particles starts to rise when CME is at about 4 R ⊙, achieves its maximum at 6–10 R ⊙, and declines shortly after that (type J). The type J particle injection into the interplanetary space coincides with the decametric–hectometric radio burst complex that includes enhanced emission of type II and concurrent low-frequency type III bursts, indicative of the CME interaction with a streamer-like structure at a few solar radii from the Sun. Those could be delayed particles from the flare region. A possible additional contribution of the CME-bow-shock acceleration in unstructured solar wind is not large in the two considered types of events.

Heights of Coronal Mass Ejections and Shocks Inferred from Metric and DH Type II Radio Bursts

A set of 27 continuous events that showed extension of metric Type-II radio bursts (m-Type IIs) into the deca–hectometric (DH) domain is considered. The coronal mass ejections (CMEs) associated with this type of continuous event supply more energy to produce space-weather effects than the CMEs that produce Type-II bursts in any one region. Since the heights of shock formation at the start of m-Type IIs were not available from observations, they were estimated using kinematic modeling in previous studies. In the present study, the heights of shock formation during metric and DH Type-II bursts are determined using two methods: i) the CME leading-edge method and ii) a method employing known electron-density models and start/end frequencies. In the first method, assuming that the shocks are generated by the associated CMEs at the leading edge, the height of the CME leading edge (LE) is calculated at the onset and end of m-Type IIs using the kinematic equation with constant acceleration or constant speed. The LE heights of CMEs that are assumed to be the heights of shock formation/end of nearly 79% of m-Type IIs are found to be within the acceptable range of \(1\,\mbox{--}\,3~\mbox{R}_{\odot}\). For other events, the heights are beyond this range, for which the shocks might either have been generated at the CME flanks/flare-blast waves, or the initial CME height might have been different. The CME/shock height at the onset and end of 17 DH Type IIs are found to be in the range of \(2\,\mbox{--}\,6~\mbox{R}_{\odot}\) and within \(30~\mbox{R}_{\odot}\), respectively. In addition, the CME LE heights from observations at the onset and end of metric/DH Type IIs are compared with the heights corresponding to the observed frequency that is determined using the known electron-density models, and they are in agreement with the model results. The heights are also estimated using the space speed available for 15 halo CMEs, and it is found that the difference is smaller at the m-Type II start/end (0.02 to \(0.66~\mbox{R}_{\odot}\)) and slightly greater at the DH Type II end (0.19 to \(1.94~\mbox{R}_{\odot}\)). Finally, the possibility of CME–streamer interactions at the start of DH Type IIs is checked, and it is found that many of the events with streamers have lower start frequencies. In addition, these results are discussed in comparison with the values reported in the literature. This study will be useful to find the source region of metric and DH Type IIs and to understand the CME-shock propagation.

Origin of Radio Enhancements in Type II Bursts in the Outer Corona

We study interplanetary (IP) solar radio type II bursts from 2011 – 2014 in order to determine the cause of the intense enhancements in their radio emission. Type II bursts are known to be due to propagating shocks that are often associated with fast halo-type coronal mass ejections (CMEs). We analysed the radio spectral data and the white-light coronagraph data from 16 selected events to obtain directions and heights for the propagating CMEs and the type II bursts. CMEs preceding the selected events were included in the analysis to verify whether CME interaction was possible. As a result, we were able to classify the events into five different groups. 1) Events where the heights of the CMEs and type II bursts are consistent, indicating that the shock is located at the leading front of the CME. The radio enhancements are superposed on the type II lanes, and they are probably formed when the shock meets remnant material from earlier CMEs, but the shock continues to propagate at the same speed. 2) Events where the type II heights agree with the CME leading front and an earlier CME is located at a height that suggests interaction. The radio enhancements and frequency jumps could be due to the merging process of the CMEs. 3) Events where the type II heights are significantly lower than the CME heights almost from the start. Interaction with close-by streamers is probably the cause for the enhanced radio emission, which is located at the CME flank region. 4) Events where the radio enhancements are located within wide-band type II bursts and the causes for the radio enhancements are not clear. 5) Events where the radio enhancements are associated with later-accelerated particles (electron beams, observed as type III bursts) that stop at the type II burst emission lane, and no other obvious reason for the enhancement can be identified. Most of the events (38%) were due to shock–streamer interaction, while one quarter of the events was due to possible CME–CME interaction. The drift rates, bandwidth characteristics, or cross-correlations of various characteristics did not reveal any clear association with particular category types. The chosen atmospheric density model causes the largest uncertainties in the derived radio heights, although in some cases, the emission bandwidths also lead to relatively large error margins. Our conclusion is that the enhanced radio emission associated with CMEs and propagating shocks can have different origins, depending on their overall configuration and the associated processes.

Height of shock formation in the solar corona inferred from observations of type II radio bursts and coronal mass ejections

Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5Rs. In a few cases, the CME height at type II onset was close to 2Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25–40MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.

TEMPORAL AND PHYSICAL CONNECTION BETWEEN CORONAL MASS EJECTIONS AND FLARES

The physical connection between the eruption of coronal mass ejections (CMEs) and associated flare energy release is examined. The trajectories of five CMEs are determined using LASCO/SOHO or SECCHI/STEREO data, and the associated soft X-ray (SXR) light curves are obtained from GOES 1-8 A data. As the theoretical description of CME physics, the existing erupting flux-rope model is used in which an initial flux rope is driven out of equilibrium by the increasing poloidal magnetic flux {Phi}{sub p}(t) (poloidal 'flux injection'). Mathematically, this is represented by d{Phi}{sub p}(t)/dt. For each CME, this function is adjusted to obtain the solution that best fits the observed height-time data. The resulting d{Phi}{sub p}(t)/dt is shown to be strongly constrained by the CME height data. This function and the attendant electromotive force (EMF) given by E(t){identical_to}-(1/c)d{Phi}{sub p}(t)/dt constitute predictions of the theory for each CME trajectory. It is shown that the best-fit solutions fit the CME trajectories within 1%-2% of the CME height data and that the temporal profile of the predicted d{Phi} {sub p}(t)/dt is correlated with that of the associated X-ray light curve regardless of the flare duration. Specifically, we find that the observed duration of SXR emission {Delta}T{sub SXR} is comparablemore » to and scales with the predicted duration {Delta}T{sub p} of poloidal flux injection, i.e., {Delta}T{sub SXR} {approx_equal} {Delta}T{sub p} . Neither the predicted d{Phi} {sub p}(t)/dt nor the input CME height data contain any information on X-ray data. Thus, the correlation is nontrivial, constituting evidence that poloidal flux injection is physically connected to flare energy release. It is suggested that this connection is provided by the EMF that produces electric fields to accelerate particles.« less

The kinematics of coronal mass ejections using multiscale methods

Aims. The diffuse morphology and transient nature of coronal mass ejections (CMEs) make them diffi cult to identify and track using traditional image processing techniques. We apply multiscale methods to enhance the visibility of the faint CME front. This enables an ellipse characterisation to objectively study the chang ing morphology and kinematics of a sample of events imaged by the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO). The accuracy of these methods allows us to test the CMEs for non-constant acceleration and expansion. Methods. We exploit the multiscale nature of CMEs to extract structure with a multiscale decomposition, akin to a Canny edge detector. Spatio-temporal filtering highlights the CME fro nt as it propagates in time. We apply an ellipse parameterisation of the front to extract the kinematics (height, velocity, acceleration ) and changing morphology (width, orientation). Results. The kinematic evolution of the CMEs discussed in this paper have been shown to differ from existing catalogues. These catalogues are based upon running-difference techniques that can lead to over-estimating CME heights. Our resulting kinematic curves are not well-fitted with the constant acceleration mo del. It is shown that some events have high acceleration below∼5 R⊙. Furthermore, we find that the CME angular widths measured by t hese catalogues are over-estimated, and indeed for some events our analysis shows non-constant CME expansion across the plane-of-sky.

Type II radio bursts and energetic solar eruptions

We report on a study of type II radio bursts from the Wind/WAVES experiment in conjunction with white‐light coronal mass ejections (CME) from the Solar and Heliospheric Observatory (SOHO). The type II bursts considered here have emission components in all the spectral domains: metric, decameter‐hectometric (DH) and kilometric (km), so we refer to them as m‐to‐km type II bursts. CMEs associated with the m‐to‐km type II bursts were more energetic than those associated with bursts in any single wavelength regime. CMEs associated with type II bursts confined to the metric domain were more energetic (wider and faster) than the general population of CMEs but less energetic than CMEs associated with DH type II bursts. Thus the CME kinetic energy seems to organize the life time of the type II bursts. Contrary to previous results, the starting frequency of metric type II bursts with interplanetary counterparts seems to be no different from that of type II bursts without interplanetary counterparts. We also verified this by showing that the average CME height at the onset time of the type II bursts is the same for the two metric populations. The majority (78%) of the m‐to‐km type II bursts were associated with solar energetic particle (SEP) events. The solar sources of the small fraction of m‐to‐km type II bursts without SEP association were poorly connected to the observer near Earth. Finally, we found that the m‐to‐km type II bursts were associated with bigger flares compared to the purely metric type II bursts.

Four Corona Mass Ejections and their Associated Surface Activity Observed on 26 October 2003

Four coronal mass ejections (CMEs) occurs successively from the solar disk near the west limb on October 26, 2003. They, together with the associated activities of the solar surface, were observed by various instruments both in space and on ground, such as the Large Angle and Spectrometric Coronagraph Experiment (LASCO), the Extreme Ultraviolet Imaging Telescope, and the Michelson Doppler Imager on board the Solar and Heliospheric Observatory, as well as the Huairou Solar Observing Station and the Big Bear Solar Observatory. These four events start with a filament eruption that manifests a two-ribbon flare in a spotless region, destroyed a helmet streamer, and give rise to an X1.2 flare in the active region AR0484. We notice that these eruptions occur either in active region, or in quiescent region, or in the region without any precursors. The time profiles of the CME (filament) heights show that the main acceleration takes place within one solar radius .To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Injection profiles of solar energetic particles as functions of coronal mass ejection heights

Previous studies with Skylab and Solwind coronal mass ejections (CMEs) have shown that nearly all large E greater than 10 MeV solar energetic particle (SEP) events are associated with fast (v greater than 400 km/sec) CMEs. We compare heights of CMEs observed on the SMM spacecraft with the flux-time profiles of five associated SEP events observed by the GOES spacecraft, including three events observed as ground-level events (GLEs) by neutron monitors. The SEP injection profiles as functions of the CME heights are estimated from the 'solar release times' and the effects of interplanetary scattering. We find that the peaks of the 470 MeV to 4 GeV injection profiles of the GLEs occur when CME heights reach 5 to 15 R(sub 0) or greater and that the onsets occur no earlier than the maxima of the flare impulsive phases. In those events SEP injection appears to result only from a single CME-driven shock and not from the flare impulsive phase or from separate coronal and interplanetary shocks. In one small SEP event an impulsive flux-time profile is consistent with injection during the flare impulsive phase but could also be due to injection from a coronal shock over a limited time.