Narrow Coronal Mass Ejections Research Articles

Element Abundances in Impulsive Solar Energetic-Particle Events

Impulsive solar energetic-particle (SEP) events were first distinguished as the streaming electrons that produce type III radio bursts as distinct from shock-induced type II bursts. They were then observed as the surprisingly enhanced 3He-rich SEP events, which were also found to have element enhancements rising smoothly with the mass-to-charge ratio A/Q through the elements, even up to Pb. These impulsive SEPs have been found to originate during magnetic reconnection in solar jets where open magnetic field lines allow energetic particles to escape. In contrast, impulsive solar flares are produced when similar reconnection involves closed field lines where energetic ions are trapped on closed loops and dissipate their energy as X-rays, γ-rays, and heat. Abundance enhancements that are power laws in A/Q can be used to determine Q values and hence the coronal source temperature in the events. Results show no evidence of heating, implying reconnection and ion acceleration occur early, rapidly, and at low density. Proton and He excesses that contribute their own power law may identify events with reacceleration of SEPs by shock waves driven by accompanying fast, narrow coronal mass ejections (CMEs) in many of the stronger jets.

Multiwavelength Observations of a Partial Filament Eruption on 13 June 2011

In this paper, we report the multiwavelength observations of the partial filament eruption associated with a C1.2 class flare in NOAA active region 11236 on 13 June 2011. The event occurred at the eastern limb in the field of view (FOV) of Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) spacecraft and was close to the disk center in the FOV of Extreme-UltraViolet Imager (EUVI) onboard the Behind Solar Terrestrial Relations Observatory (STEREO) spacecraft. During eruption, the filament splits into two parts: the major part and the runaway part. The major part flows along closed loops and experiences bifurcation at the loop top. Some of the materials move forward and reach the remote footpoint, while the remainder returns back to the original footpoint. The runaway part flows along open-field lines, which is evidenced by a flare-related type-III radio burst. The runaway part also undergoes bifurcation. The upper branch escapes the corona and evolves into a jet-like narrow coronal mass ejection (CME) at a speed of ∼ 324 km s−1, while the lower branch falls back to the solar surface. A schematic cartoon is proposed to explain the event and provides a new mechanism of partial filament eruptions.

Widespread 1–2 MeV Energetic Particles Associated with Slow and Narrow Coronal Mass Ejections: Parker Solar Probe and STEREO Measurements

Abstract Suprathermal ions in the corona are thought to serve as seed particles for large gradual solar energetic particle (SEP) events associated with fast and wide coronal mass ejections (CMEs). A better understanding of the role of suprathermal particles as seed populations for SEP events can be made by using observations close to the Sun. We study a series of SEP events observed by the Integrated Science Investigation of the Sun (IS⊙IS) suite on board the Parker Solar Probe (PSP) from 2020 May 27 to June 2, during which PSP was at heliocentric distances between ∼0.4 and ∼0.2 au. These events were also observed by the Ahead Solar TErrestrial RElations Observatory (STEREO-A) near 1 au, but the particle intensity magnitude was much lower than that at PSP. We find that the SEPs should have spread in space as their source regions were distant from the nominal magnetic footpoints of both spacecraft and the parent CMEs were slow and narrow. We study the decay phase of the SEP events in the ∼1–2 MeV proton energy range at PSP and STEREO-A, and discuss their properties in terms of both continuous injections by successive solar eruptions and the distances where the measurements were made. This study indicates that seed particles can be continuously generated by eruptions associated with slow and narrow CMEs, spread over a large part of the inner heliosphere, and remain there for tens of hours, even if minimal particle intensity enhancements were measured near 1 au.

Cause and Kinematics of a Jetlike CME

Abstract In this article, we present the multiviewpoint and multiwavelength analysis of an atypical solar jet based on data from Solar Dynamics Observatory, SOlar and Heliospheric Observatory, and Solar TErrestrial RElations Observatory. It is generally believed that coronal mass ejections (CMEs) develop from the large-scale solar eruptions in the lower atmosphere. However, the kinematical and spatial evolution of the jet on 2013 April 28 suggests that the jet was clearly associated with a narrow CME with a width of ≈25° and speed of ≈450 km s−1. To better understand the link between the jet and the CME, we performed a coronal potential field extrapolation from the line-of-sight magnetogram of the active region. The extrapolations suggest that the jet eruption follows the same path of the open magnetic field lines from the source region, which provides a route for the jet material to escape from the solar surface toward the outer corona.

First Observation of a Type II Solar Radio Burst Transitioning between a Stationary and Drifting State

Abstract Standing shocks are believed to be responsible for stationary Type II solar radio bursts, whereas drifting Type II bursts are excited by moving shocks often related to coronal mass ejections (CMEs). Observations of either stationary or drifting Type II bursts are common, but a transition between the two states has not yet been reported. Here, we present a Type II burst which shows a clear, continuous transition from a stationary to a drifting state, the first observation of its kind. Moreover, band splitting is observed in the stationary parts of the burst, as well as intriguing negative and positive frequency-drift fine structures within the stationary emissions. The relation of the radio emissions to an observed jet and a narrow CME were investigated across multiple wavelengths, and the mechanisms leading to the transitioning Type II burst were determined. We find that a jet eruption generates a streamer-puff CME and that the interplay between the CME-driven shock and the streamer is likely to be responsible for the observed radio emissions.

Are Solar Energetic Particle Events and Type II Bursts Associated with Fast and Narrow Coronal Mass Ejections?

Gradual solar energetic ( $E >10~\mbox{MeV}$ ) particle (SEP) events and metric through kilometric wavelength type II radio bursts are usually associated with shocks driven by fast ( $V \geq 900~\mbox{km}\,\mbox{s}^{-1}$ ) and wide ( $W \geq 60^{\circ} $ ) coronal mass ejections (FW CMEs). This criterion was established empirically by several studies from solar cycle 23. The characteristic Alfven speed in the corona, which ranges over 500 – 1500 km s−1 at heights ${\geq}\, 2~R_{\text{o}}$ , provides the minimum $V$ requirement for a CME to drive a shock, but the general absence of SEP events or type II bursts with fast and narrow ( $W < 60^{\circ}$ ) CMEs has not been explained. We review and confirm the earlier studies with a more comprehensive comparison of SEP events and type II bursts with fast and narrow (FN) CMEs. We offer an explanation for the lack of SEP event and type II burst associations with FN CMEs in terms of recent heuristic arguments and modeling that show that the response of a magnetized plasma to the propagation of a CME depends on the CME geometry as well as on its speed. A clear distinction is made between a projectile that propagates through the medium to produce a bow shock, and a 3D piston that everywhere accumulates material to produce a broad shock and sheath. The bow shock is unfavorable for producing SEP events and type II bursts, but the $60^{\circ} $ cut-off is not explained.

Interaction of the Extended Envelope of a Hot Jupiter with a Narrow Coronal Mass Ejection

The passage of a hot Jupiter with a quasi-closed extended envelope through a short coronal mass ejection (CME) with a small opening angle is considered. The results of three-dimensional gasdynamical simulations are used to determine the characteristics of the flow in the planet’s envelope as it intersects the CME, and to infer possible observational manifestations of such an event. Two options are considered—entry of the planet into the CME at the beginning of the CME and a tangential interaction with the leading edge of the CME. The mass lost by the planet as a result of its interaction with the CME is estimated.

Very narrow coronal mass ejections producing solar energetic particles

Aims. Our main aim is to study the relationship between low-energy solar particles (energies below 1 MeV) and very narrow coronal mass ejections (“jets” with angular width ≤ 20°). Methods. For this purpose, we considered 125 very narrow coronal mass ejections (CMEs) from 1999 to 2003 that are potentially associated with low-energy solar particles (LESPs). These events were chosen on the basis of their source location. We studied only very narrow CMEs at the western limb, which are expected to have good magnetic connectivity with Earth. Results. We found 24 very narrow CMEs associated with energetic particles such as ions (protons and 3He), electrons, or both. We show that arrival times at Earth of energetic particles are consistent with onset times of the respective CMEs, and that in the same time intervals, there are no other potential sources of energetic particles. We also demonstrate statistical differences for the angular width distributions using the Kolmogorov–Smirnov test for angular widths for these 24 events. We consider a coherent sample of jets (mostly originating from boundaries of coronal holes) to identify properties of events that produce solar energetic particles (velocities, widths, and position angles). Our study presents a new approach and result: very narrow CMEs can generate low-energy particles in the vicinity of Earth without other activity on the Sun. The results could be very useful for space weather forecasting.

Observational Study of an Earth-affecting Problematic ICME from STEREO

Abstract We present a study of the origin of one interplanetary coronal mass ejection (ICME) that lacked an easily identifiable signature of an associated progenitor coronal mass ejection (CME) near the Sun in the observations of SOHO/LASCO at the L1 point. We consider these kinds of ICMEs as problematic, as they pose the difficulty of understanding the Sun–Earth connection and providing space weather warnings; understanding the causes of problematic ICMEs is important for space weather forecasting. This study presents the first detailed analysis of a geoeffective problematic ICME that occurred on 2011 May 28, whose progenitor CMEs are difficult to identify in LASCO images, but fortunately they were captured by SECCHI on board the STEREO spacecraft in the quadrature configuration. There are two progenitor CMEs launching from the Sun in succession of 8 hours. We apply the graduated cylindrical shell model to reconstruct the 3D geometry, propagating direction, velocity, and brightness of the two CMEs. The main cause of the first CME (CME-1) invisible in SOHO/LASCO is due to its low mass; that is, when the CME emerges above the occulter, its brightness is as faint as the noise. The second CME (CME-2) is small, including a narrow angular width and a small cross-section of the magnetic flux rope. Even though propagating toward the Earth, CME-2 appeared as a narrow CME instead of as a halo or partial halo CME in the LASCO field of view. We also show that CME-2 propagates faster than CME-1, and that they might have interacted in the interplanetary space.

Flux rope breaking and formation of a rotating blowout jet

We analyzed a small flux rope eruption converted into a helical blowout jet in a fan-spine configuration using multi-wavelength observations taken by SDO, which occurred near the limb on 2016 January 9. In our study, first, we estimated the fan-spine magnetic configuration with the potential field calculation and found a sinistral small filament inside it. The filament along with the flux rope erupted upward and interacted with the surrounding fan- spine magnetic configuration, where the flux rope breaks in the middle section. We observed compact brightening, flare ribbons and post-flare loops underneath the erupting filament. The northern section of the flux rope reconnected with the surrounding positive polarity, while the southern section straightened. Next, we observed the untwisting motion of the southern leg, which was transformed into a rotating helical blowout jet. The sign of the helicity of the mini-filament matches the one of the rotating jet. This is consistent with the jet models presented by Adams et al. (2014) and Sterling et al. (2015). We focused on the fine thread structure of the rotating jet and traced three blobs with the speed of 60-120 km/s, while the radial speed of the jet is approx 400 km/s. The untwisting motion of the jet accelerated plasma upward along the collimated outer spine field lines, and it finally evolved into a narrow coronal mass ejection at the height of approx 9 Rsun . On the basis of the detailed analysis, we discussed clear evidence of the scenario of the breaking of the flux rope and the formation of the helical blowout jet in the fan-spine magnetic configuration.

ASSOCIATION OF 3He-RICH SOLAR ENERGETIC PARTICLES WITH LARGE-SCALE CORONAL WAVES

ABSTRACT Small, 3He-rich solar energetic particle (SEP) events have been commonly associated with extreme-ultraviolet (EUV) jets and narrow coronal mass ejections (CMEs) that are believed to be the signatures of magnetic reconnection, involving field lines open to interplanetary space. The elemental and isotopic fractionation in these events are thought to be caused by processes confined to the flare sites. In this study, we identify 32 3He-rich SEP events observed by the Advanced Composition Explorer, near the Earth, during the solar minimum period 2007–2010, and we examine their solar sources with the high resolution Solar Terrestrial Relations Observatory (STEREO) EUV images. Leading the Earth, STEREO-A has provided, for the first time, a direct view on 3He-rich flares, which are generally located on the Sun’s western hemisphere. Surprisingly, we find that about half of the 3He-rich SEP events in this survey are associated with large-scale EUV coronal waves. An examination of the wave front propagation, the source-flare distribution, and the coronal magnetic field connections suggests that the EUV waves may affect the injection of 3He-rich SEPs into interplanetary space.

What Are the Sources of Solar Energetic Particles? Element Abundances and Source Plasma Temperatures

We have spent 50 years in heated discussion over which populations of solar energetic particles (SEPs) are accelerated at flares and which by shock waves driven out from the Sun by coronal mass ejections (CMEs). The association of the large "gradual" SEP events with shock acceleration is supported by the extensive spatial distribution of SEPs and by the delayed acceleration of the particles. The relative abundances of the elements in these gradual events are a measure of those in the ambient solar corona, differing from those in the photosphere by a widely-observed function of the first ionization potential (FIP) of the elements. SEP events we call "impulsive", the traditional "3He-rich" events with enhanced heavy-element abundances, are associated with type III radio bursts, flares, and narrow CMEs; they selectively populate flux tubes that thread a localized source, and they are fit to new particle-in-cell models of magnetic reconnection on open field lines as found in solar jets. These models help explain the strong enhancements seen in heavy elements as a power (of 2 - 8) in the mass-to-charge ratio A/Q throughout the periodic table from He to Pb. A study of the temperature dependence of A/Q shows that the source plasma in impulsive SEP events must lie in the range of 2-4 MK to explain the pattern of abundances. This is much lower than the temperatures of >10 MK seen on closed loops in solar flares. Recent studies of A/Q-dependent enhancements or suppressions from scattering during transport show source plasma temperatures in gradual SEP events to be 0.8-1.6 MK in 69% of the events, i.e. coronal plasma; 24% of the events show reaccelerated impulsive-event material.

CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms

On 13 June 2010, an eruptive event occurred near the solar limb. It included a small filament eruption and the onset of a relatively narrow coronal mass ejection (CME) surrounded by an extreme ultraviolet wave front recorded by the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was accompanied by a GOES M1.0 soft X-ray flare and a Type-II radio burst; high-resolution dynamic spectra of the latter were obtained by the ARTEMIS IV radio spectrograph. The combined observations enabled a study of the evolution of the ejecta and the EUV wavefront and its relationship with the coronal shock manifesting itself as metric Type-II burst. By introducing a novel technique, which deduces a proxy of the EUV compression ratio from AIA imaging data and compares it with the compression ratio deduced from the band-split of the Type-II metric radio burst, we are able to infer the potential source locations of the radio emission of the shock on that AIA images. Our results indicate that the expansion of the CME ejecta is the source for both EUV and radio shock emissions. Early in the CME expansion phase, the Type-II burst seems to originate in the sheath region between the EUV bubble and the EUV shock front in both radial and lateral directions. This suggests that both the nose and the flanks of the expanding bubble could have driven the shock.

Ineffectiveness of Narrow CMEs for Cosmic Ray Modulation

Monthly coronal mass ejection (CME) counts, - for all CMEs and CMEs with widths > 30 ◦ , - and monthly averaged speeds for the events in these two groups were com- pared with both the monthly averaged cosmic ray intensity and the monthly sunspot number. The monthly Pi-index, which is a linear combination of monthly CME count rate and aver- age speed, was also compared with the cosmic ray intensity and sunspot number. The main finding is that narrow CMEs, which were numerous during 2007 - 2009, are ineffective for modulation. A cross-correlation analysis, calculating both the Pearson (r) product-moment correlation coefficient and the Spearman (ρ) rank correlation coefficient, has been used. Be- tween all CMEs and cosmic ray intensity we found correlation coefficients r =− 0.49 and ρ =− 0.46, while between CMEs with widths > 30 ◦ and cosmic ray intensity we found r =− 0.75 and ρ =− 0.77, which implies a significant increase. Finally, the best expres- sion for the Pi-index for the examined period was analyzed. The highly anticorrelated be- havior among this CME index, the cosmic ray intensity (r =− 0.84 and ρ =− 0.83), and the sunspot number (r =+ 0.82 and ρ =+ 0.89) suggests that the first one is a very useful solar-heliospheric parameter for heliospheric and space weather models in general.

SIDE MAGNETIC RECONNECTIONS INDUCED BY CORONAL MASS EJECTIONS: OBSERVATIONS AND SIMULATIONS

Over the last few years coronagraphic and spectroscopic observations have demonstrated that small-scale eruptions, such as 'jets', 'narrow coronal mass ejections (CMEs)', 'mini CMEs', 'streamer puffs', 'streamer detachments', and others, occur ubiquitously on the Sun. Nevertheless, the origin of small-scale eruptive events and how these are interrelated with larger scale CMEs have been poorly investigated so far. In this work, we study a series of small-scale side eruptions that occurred during and after a large-scale CME. Observations show that a CME can be associated not only with a single reconnection process, leading to the large-scale phenomenon, but also with many other side reconnections occurring at different locations and times around the main flux rope, possibly induced by the CME expansion in the surrounding corona. White light and EUV observations of a slow CME acquired by the SOHO/LASCO and SOHO/UVCS instruments are analyzed here to characterize the locations of side reconnections induced by the CME. The magnetic reconnection rate M has been estimated from the UVCS data from the ratio between the inflows and outflows observed around the reconnection region, and from the LASCO data from the observed aperture angles between the slow mode shocks (SMSs) associated with the reconnection. Itmore » turns out that M {approx_equal} 0.05 at the heliocentric distance of 1.8 R{sub sun}, while between {approx}2.5 and 5.5 R{sub sun}, M values progressively decrease with time/altitude from M {approx} 1 down to M {approx} 0.3. Such large values of M are theoretically acceptable only if flux pile-up reconnection is envisaged. The observed occurrence of multiple reconnections associated with a CME is verified by numerical simulations of an eruption occurring within multiple helmet streamers. The simulations confirm that small side reconnections are a consequence of CME expansion against the surrounding coronal streamers. The simulated and observed evolution of aperture angles between the SMSs are in good agreement as well. These results demonstrate the effect of the global coronal magnetic field in the occurrence of small-scale eruptions due to lateral reconnection in a preceding CME event.« less

An EUV Jet and Hα Filament Eruption Associated with Flux Cancelation in a Decaying Active Region

Using data from the Transition Region and Coronal Explorer (TRACE), Solar and Heliospheric Observatory (SOHO), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and Hida Observatory (HO), we present a detailed study of an EUV jet and the associated Hα filament eruption in a major flare in the active region NOAA 10044 on 29 July 2002. In the Hα line wings, a small filament was found to erupt out from the magnetic neutral line of the active region during the flare. Two bright EUV loops were observed rising and expanding with the filament eruption, and both hot and cool EUV plasma ejections were observed to form the EUV jet. The two thermal components spatially separated from each other and lasted for about 25 minutes. In the white-light corona data, a narrow coronal mass ejection (CME) was found to respond to this EUV jet. We cannot find obvious emerging flux in the photosphere accounting for the filament eruption and the EUV jet. However, significant sunspot decay and magnetic-flux cancelation owing to collision of opposite flux before the events were noticed. Based on the hard X-ray data from RHESSI, which showed evidence of magnetic reconnection along the main magnetic neutral line, we think that all of the observed dynamical phenomena, including the EUV jet, filament eruption, flare, and CME, should have a close relation to the flux cancelation in the low atmosphere.

A comparison of coronal mass ejections identified by manual and automatic methods

Abstract. Coronal mass ejections (CMEs) are related to many phenomena (e.g. flares, solar energetic particles, geomagnetic storms), thus compiling of event catalogs is important for a global understanding these phenomena. CMEs have been identified manually for a long time, but in the SOHO era, automatic identification methods are being developed. In order to clarify the advantage and disadvantage of the manual and automatic CME catalogs, we examined the distributions of CME properties listed in the CDAW (manual) and CACTus (automatic) catalogs. Both catalogs have a good agreement on the wide CMEs (width&gt;120°) in their properties, while there is a significant discrepancy on the narrow CMEs (width≤30°): CACTus has a larger number of narrow CMEs than CDAW. We carried out an event-by-event examination of a sample of events and found that the CDAW catalog have missed many narrow CMEs during the solar maximum. Another significant discrepancy was found on the fast CMEs (speed&gt;1000 km/s): the majority of the fast CDAW CMEs are wide and originate from low latitudes, while the fast CACTus CMEs are narrow and originate from all latitudes. Event-by-event examination of a sample of events suggests that CACTus has a problem on the detection of the fast CMEs.

A Study of Surges: II. On the Relationship between Chromospheric Surges and Coronal Mass Ejections

Liu et al. (Astrophys. J. 628, 1056, 2005a) described one surge – coronal mass ejection (CME) event showing a close relationship between solar chromospheric surge ejection and CME that had not been noted before. In this work, large Hα surges (>72 Mm, or 100 arcsec) are studied. Eight of these were associated with CMEs. According to their distinct morphological features, Hα surges can be classified into three types: jetlike, diffuse, and closed loop. It was found that all of the jetlike surges were associated with jetlike CMEs (with angular widths ≤30 degrees); the diffuse surges were all associated with wide-angle CMEs (e.g., halo); the closed-loop surges were not associated with CMEs. The exclusive relation between Hα surges and CMEs indicates difference in magnetic field configurations. The jetlike surges and related narrow CMEs propagate along coronal fields that are originally open. The unusual transverse mass motions in the diffuse surges are suggested to be due to magnetic reconnections in the corona that produce wide-angle CMEs. For the closed-loop surges, their paths are just outlining stable closed loops close to the solar surface. Thus no CMEs are associated with them.

A STATISTICAL STUDY OF STREAMER-ASSOCIATED CORONAL MASS EJECTIONS

We have made a comprehensive statistical study on the coronal mass ejections(CMEs) associated with helmet streamers. A total number of 3810 CMEs observed by SOHO/LASCO coronagraph from 1996 to 2000 have been visually inspected. By comparing their LASCO images and running difference images, we picked out streamer-associated CMEs, which are classified into two sub-groups: Class-A events whose morphological shape seen in the LASCO running difference image is quite similar to that of the pre-existing streamer, and Class-B events whose ejections occurred in a part of the streamer. The former type of CME may be caused by the destabilization of the helmet streamer and the latter type of CME may be related to the eruption of a filament underlying the helmet streamer or narrow CMEs such as streamer puffs. We have examined the distributions of CME speed and acceleration for both classes as well as the correlation between their speed and acceleration. The major results from these investigations are as follows. First, about a quarter of all CMEs are streamer-associated CMEs. Second, their mean speed is 413 km for Class-A events and 371 km for Class-B events. And the fraction of the streamer-associated CMEs decreases with speed. Third, the speed-acceleration diagrams show that there are no correlations between two quantities for both classes and the accelerations are nearly symmetric with respect to zero acceleration line. Fourth, their mean angular width are about , which is similar to that of normal CMEs. Fifth, the fraction of streamer-associated CMEs during the solar minimum is a little larger than that during the solar maximum. Our results show that the kinematic characteristics of streamer-associated CMEs, especially Class-A events, are quite similar to those of quiescent filament-associated CMEs.

Visibility of coronal mass ejections as a function of flare location and intensity

We report the visibility (detection efficiency) of coronal mass ejections (CMEs) of the Large Angle Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). We collected 1301 X‐ray flare events (above C3 level) detected by the GOES satellite and examined their CME associations using data from LASCO coronagraphs. The CME visibility was examined using the longitudinal variation of CME association of X‐ray flares, under the assumption that all CMEs associated with limb flares are detectable by LASCO. Our findings are (1) the CME association rate clearly increased with X‐ray flare size from 20% for C‐class flares (between C3 and C9 levels) to 100% for huge flares (above X3 level), (2) all CMEs associated with X‐class flares were detected by the LASCO coronagraphs, while half (25–67%) of CMEs associated with C‐class flares were invisible. We examined the statistical properties of the flare‐associated CMEs and compared them by flare size and longitude. CMEs associated with X‐class flares were significantly faster (median 1556 km/s) and wider (median 244°) than those of CMEs associated with disk C‐class flares (432 km/s, 68°). We conclude that all fast and wide CMEs are detectable by LASCO, but slow and narrow CMEs may not be visible when the CMEs originate from the disk center.