Coronal Dimming Research Articles

Interchange reconnection between an active region and a coronal hole

With data from the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, we present a magnetic interaction between an isolated coronal hole (CH) and an emerging active region (AR). The AR emerged nearby the CH and interacted with it. Bright loops constantly formed between them, which led to a continuous retreat of the CH boundaries (CHBs). Meanwhile, two coronal dimmings respectively appeared at the negative polarity of the AR and the east boundary of the bright loops, and the AR was partly disturbed. Loop eruptions followed by a flare occurred in the AR. The interaction was also accompanied by many jets and an arc-shaped brightening that appeared to be observational signatures of magnetic reconnection at the CHBs. By comparing the observations with the derived coronal magnetic configuration, it is suggested that the interaction between the CH and the AR excellently agreed with the model of interchange reconnection. It appears that our observations provide obvious evidence for interchange reconnection.

OVERLYING EXTREME-ULTRAVIOLET ARCADES PREVENTING ERUPTION OF A FILAMENT OBSERVED BY AIA/SDO

Using the multi-wavelength data from the Atmospheric Imaging Assembly/Solar Dynamic Observatory (AIA/SDO) and the Sun Earth Connection Coronal and Heliospheric Investigation/Solar Terrestrial Relations Observatory (SECCHI/STEREO), we report a failed filament eruption in NOAA AR 11339 on 2011 November 3. The eruption was associated with an X1.9 flare, but without any coronal mass ejection (CME), coronal dimming, or extreme ultraviolet (EUV) waves. Some magnetic arcades above the filament were observed distinctly in EUV channels, especially in the AIA 94?? and 131?? wavebands, before and during the filament eruption process. Our results show that the overlying arcades expanded along with the ascent of the filament at first until they reached a projected height of about 49?Mm above the Sun's surface, where they stopped. The following filament material was observed to be confined by the stopped EUV arcades and not to escape from the Sun. After the flare, a new filament formed at the low corona where part of the former filament remained before its eruption. These results support that the overlying arcades play an important role in preventing the filament from successfully erupting outward. We also discuss in this paper the EUV emission of the overlying arcades during the flare. It is rare for a failed filament eruption to be associated with an X1.9 class flare, but not with a CME or EUV waves. Therefore, this study also provides valuable insight into the triggering mechanism of the initiation of CMEs and EUV waves.

X6.9-CLASS FLARE-INDUCED VERTICAL KINK OSCILLATIONS IN A LARGE-SCALE PLASMA CURTAIN AS OBSERVED BY THESOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY

We present rare observational evidence of vertical kink oscillations in a laminar and diffused large-scale plasma curtain as observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The X6.9-class flare in active region 11263 on 2011 August 9 induces a global large-scale disturbance that propagates in a narrow lane above the plasma curtain and creates a low density region that appears as a dimming in the observational image data. This large-scale propagating disturbance acts as a non-periodic driver that interacts asymmetrically and obliquely with the top of the plasma curtain and triggers the observed oscillations. In the deeper layers of the curtain, we find evidence of vertical kink oscillations with two periods (795 s and 530 s). On the magnetic surface of the curtain where the density is inhomogeneous due to coronal dimming, non-decaying vertical oscillations are also observed (period ≈ 763-896 s). We infer that the global large-scale disturbance triggers vertical kink oscillations in the deeper layers as well as on the surface of the large-scale plasma curtain. The properties of the excited waves strongly depend on the local plasma and magnetic field conditions.

Observations of Overlying Extreme-ultraviolet Arches confining the eruption of a Filament

AbstractUsing the multi-wavelength data from AIA/SDO, we report a failed filament eruption, which was associated with an X1.9 flare, but without any distinct CME, coronal dimming or EUV wave. Some magnetic arches above the filament was observed distinctly in EUV channels, especially in 94 Å and 131 Å, before and during the filament eruption. Our results show that the overlying arcades expanded along with the ascent of the filament at first until they reached a projected height of about 49 Mm above the Suns surface, where they stopped. The following filament material was observed to be confined by the stopped EUV arches and not to escape from the Sun. These results support that the overlying arcades play an important role in preventing the filament to erupt outward successfully.

Formation of Coronal Shock Waves

Numerical simulations of magnetosonic wave formation driven by an expanding cylindrical piston are performed to get better physical insight into the initiation and evolution of large-scale coronal waves. Several very basic initial configurations are employed to analyze intrinsic characteristics of the MHD wave formation that do not depend on specific properties of the environment. It turns out that these simple initial configurations result in piston/wave morphologies and kinematics that reproduce common characteristics of coronal waves. In the initial stage the wave and the expanding source-region cannot be clearly resolved. During the acceleration stage of the source-region inflation, the wave is driven by the piston expansion, so its amplitude and phase-speed increase, whereas the wavefront profile steepens. At a given point, a discontinuity forms in the wavefront profile. The time/distance required for the shock formation is shorter for a more impulsive source-region expansion. After the piston stops, the wave amplitude and phase-speed start decreasing. During the expansion, most of the source region becomes strongly rarified, which reproduces the coronal dimming left behind the eruption. On the other hand, the density increases at the source-region boundary, and stays enhanced even after the expansion stops, which might explain stationary brightenings that are sometimes observed at the edges of the erupted coronal structure. In addition, in the rear of the wave a weak density depletion develops, trailing the wave, which is sometimes observed as weak transient coronal dimming. Finally, we find a well defined relationship between the impulsiveness of the source-region expansion and the wave amplitude and phase speed. The results for the cylindrical piston are also compared with the outcome for a planar wave, to find out how different geometries affect the evolution of the wave.

Loop oscillations and an extreme ultraviolet wave associated with a micro-sigmoid eruption

Taking advantage of the high temporal and spatial resolution observations of the Solar Dynamics Observatory, we present an extreme ultraviolet (EUV) wave associated with a micro-sigmoid eruption, which took place on 2012 October 4. The micro-sigmoid underwent a typical sigmoid-to-arcade evolution via tether-cutting reconnection, accompanied by a micro-flare, a filament eruption. The twin coronal dimmings at the footpoints of the sigmoid indicate the existence of the associated micro-coronal mass ejection that likely triggered a small-scale EUV wave. The wave onset was nearly simultaneous with the start of the eruption and the associated flare. The wave had a nearly circular front, and propagated at initial velocities of 300–360 km s−1. Because the sigmoid was located in the non-quiet region, the generated wave interacted with the ambient loops, and triggered transverse loop oscillations, resulting in many loop-shaped dimmings. Moreover, the interaction between the wave and one large loop led not only to the oscillation but also to the downward plasma flow along the loop, inducing loop footpoints to brighten. Another small loop was nearly intact after the wave passed. In some directions, the wave was refracted by the loops, and the refracted speeds increased, decreased, or vanished in different directions. All results provide evidence that the EUV wave was a fast-mode magnetohydrodynamic wave.

STUDY OF THE RECURRING DIMMING REGION DETECTED AT AR 11305 USING THE CORONAL DIMMING TRACKER (CoDiT)

We present a new approach to coronal dimming detection using the COronal DImming Tracker tool (CODIT), which was found to be successful in locating and tracking multiple dimming regions. This tool, an extension of a previously developed coronal hole tracking software, allows us to study the prop- erties and the spatial evolution of dimming regions at high temporal and spatial cadence from the time of their appearance to their disappearance. We use the Solar Dynamics Observatory/Atmospheric Imaging Assembly 193 A wavelength observations and Helioseismic and Magnetic Imager to study dimmings. As a demonstration of the detection technique we analyzed six recurrences of a dimming observed near AR 11305 between 2011 September 29 and October 2. The dimming repeatedly ap- peared and formed in a similar way, first expanding then shrinking and occasionally stabilizing in the same location until the next eruption. The dimming areas were studied in conjunction with the corre- sponding flare magnitudes and coronal mass ejection (CME) masses. These properties were found to follow a similar trend during the observation period, which is consistent with the idea that the mag- nitude of the eruption and the CME mass affect the relative sizes of the consecutive dimmings. We also present a hypothesis to explain the evolution of the recurrent single dimming through interchange reconnection. This process would accommodate the relocation of quasi-open magnetic field lines and hence allow the CME flux rope footpoint (the dimming) to expand into quiet Sun regions. By relating the properties of dimmings, flares, and CMEs we improve our understanding of the magnetic field reconfiguration caused by reconnection.

Quiet Sun Explosive Events: Jets, Splashes, and Eruptions

Explosive events appear as broad non-Gaussian wings in the line profiles of small transition-region phenomena. Images from the Solar Dynamics Observatory (SDO) give a first view of the plasma dynamics at the sites of explosive events seen simultaneously in O vi spectra of a region of quiet Sun, taken with the ultraviolet spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the Solar and Heliospheric Observatory (SOHO). Distinct event bursts were seen either at the junction of supergranular network cells or near emerging flux. Three are described in the context of their surrounding transition region (304 Å) and coronal (171 Å) activity. One showed plasma ejections from an isolated pair of sites, with a time lag of 50 seconds between events. At the site where the later explosive event was seen, the extreme ultraviolet (EUV) images show a hot core surrounded by a small, expanding ring of chromospheric emission, which we interpret as a “splash.” The second explosive-event burst was related to flux cancellation, inferred from Helioseismic and Magnetic Imager (HMI) magnetograms, and a coronal dimming surrounded by a ring of bright EUV emission with explosive events at positions where the spectrometer slit crossed the bright ring. The third series of events occurred at the base of a slow, small coronal mass ejection (mini-CME). All events studied here imply jet-like flows probably triggered by magnetic reconnection at supergranular junctions. Events come from sites close to the footpoints of jets seen in Atmospheric Imaging Assembly (AIA) images, and possibly from the landing site of high-velocity flows. They are not caused by rapid rotation in spicules.

DIFFERENTIAL EMISSION MEASURE ANALYSIS OF MULTIPLE STRUCTURAL COMPONENTS OF CORONAL MASS EJECTIONS IN THE INNER CORONA

In this paper, we study the temperature and density properties of multiple structural components of coronal mass ejections (CMEs) using differential emission measure (DEM) analysis. The DEM analysis is based on the six-passband EUV observations of solar corona from the Atmospheric Imaging Assembly onboard the \emph{Solar Dynamic Observatory}. The structural components studied include the hot channel in the core region (presumably the magnetic flux rope of the CME), the bright loop-like leading front (LF), and coronal dimming in the wake of the CME. We find that the presumed flux rope has the highest average temperature ($>$8 MK) and density ($\sim$1.0 $\times10^{9}$ cm$^{-3}$), resulting in an enhanced emission measure (EM) over a broad temperature range (3 $\leq$ T(MK) $\leq$ 20). On the other hand, the CME LF has a relatively cool temperature ($\sim$2 MK) and a narrow temperature distribution similar to the pre-eruption coronal temperature (1 $\leq$ T(MK) $\leq$ 3). The density in the LF, however, is increased by 2% to 32% compared with that of the pre-eruption corona, depending on the event and location. In coronal dimmings, the temperature is more broadly distributed (1 $\leq$ T(MK) $\leq$ 4), but the density decreases by $\sim$35% to $\sim$40%. These observational results show that: (1) CME core regions are significantly heated, presumably through magnetic reconnection, (2) CME LFs are a consequence of compression of ambient plasma caused by the expansion of the CME core region, and (3) the dimmings are largely caused by the plasma rarefaction associated with the eruption.

AN EXTREME ULTRAVIOLET WAVE ASSOCIATED WITH A MICRO-SIGMOID ERUPTION

Taking advantage of the high temporal and spatial resolution of the Solar Dynamics Observatory (SDO) observations, we present an extreme ultraviolet (EUV) wave associated with a micro-sigmoid eruption on 2010 October 21. The micro-sigmoid underwent a typical sigmoid-to-arcade evolution via tether-cutting reconnection, accompanied by a B1.7 flare, a filament eruption, and coronal twin dimmings. In the eruption, the newly formed sigmoidal loops expanded quickly, and the expansion likely triggered an EUV wave. The wave onset was nearly simultaneous with the start of the eruption and the associated flare. The wave had a nearly circular front and propagated at a constant velocity of 270-350 km s(-1) with very little angular dependence. Remarkably, in some direction, the wave encountered a small loop and refracted at a higher speed. All the results provide evidences that the wave was a fast-mode magnetohydrodynamic (MHD) wave. Owing to the close temporal and spatial relationship between the wave and the expanding loops, we believe that the wave was most likely triggered by the fast expansion of the newly formed sigmoidal loops, which evolved into the leading front of the invisible micro-coronal mass ejection.

A blowout surge from the eruption of a miniature filament confined by large coronal loops

By means of Hα, EUV, soft X-ray, hard X-ray, and photospheric magnetic field observations, we report the surge-like eruption of a small-scale filament, called “blowout surge” according to recent observations, occurring on a plage region around AR 10876 on 1 May 2006. Along magnetic polarity reversal boundaries with obvious magnetic cancelations, the filament was located underneath a compact coronal arcade and close to one end of large coronal loops around the AR’s periphery. The filament started to erupt about 8min before the main impulsive phase of a small two-ribbon flare, which had two Hα blue-wing kernels connected by hard X-ray loop-top sources on the both sides of the filament. After the flare end, the filament further underwent a distant eruption following a path nearly along the preexisting large loops, and thus looked like an Hα surge and an EUV jet. During the eruption, a small coronal dimming was formed near the flare, while weak brightenings appeared around the remote end of the large loops. We interpret these joint observations as the filament eruption being confined and guided by the large loops. The filament eruption, initially embedded in one footpoint region of the large loops, can break away from the magnetic restraint of the overlying compact arcade, but might be still limited inside the large loops. As a result, the eruption took a surge form that can only expand laterally along the large loops rather than erupt radially.

The Asymmetrical Eruption of a Quiescent Filament and Associated Halo CME

We will present detailed observations of the asymmetrical eruption of a large quiescent filament on 24 November 2002, which was followed by a two-ribbon flare, three coronal dimmings, endpoint brightenings, and a very fast halo-type coronal mass ejection (CME). Before the eruption, the filament lay along the main neutral line (MNL) underneath a single-arcade helmet streamer with a simple bipolar configuration. However, photospheric magnetic fields on both sides of the filament showed an asymmetrical distribution, and the filament and MNL were not located just at the center of the streamer base but were closer to the eastern leg of the streamer arcade. Therefore, instead of erupting along the streamer’s symmetrical axis, the filament showed a nonradial and asymmetrical eruption. It lifted from the eastern flank of the streamer arcade to impact the western leg directly, leading to an asymmetrical CME that expanded westward; eventually the streamer was disrupted significantly. Accordingly, the opposite-polarity coronal dimmings at both sides of the filament forming in the eruption also showed an asymmetrical area distribution. We thus assume that the streamer arcade could guide the filament at the early eruption phase but failed to restrain it later. Consistent with previous results, these observations suggest that the global background magnetic field can impose additional action on the initial eruption of the filament and CME, as well as the dimming configuration.

POST-CORONAL MASS EJECTION PLASMA OBSERVED BYHINODE

In the present work we study the evolution of an active region after the eruption of a coronal mass ejection (CME) using observations from the EIS and XRT instruments on board Hinode. The field of view includes a post-eruption arcade, a current sheet, and a coronal dimming. The goal of this paper is to provide a comprehensive set of measurements for all these aspects of the CME phenomenon made on the same CME event. The main physical properties of the plasma along the line of sight—electron density, thermal structure, plasma composition, size, and, when possible, mass—are measured and monitored with time for the first three hours following the CME event of 2008 April 9. We find that the loop arcade observed by EIS and XRT may not be related to the post-eruption arcade. Post-CME plasma is hotter than the surrounding corona, but its temperature never exceeds 3 MK. Both the electron density and thermal structure do not show significant evolution with time, while we found that the size of the loop arcade in the Hinode plane of the sky decreased with time. The plasma composition is the same in the current sheet, in the loop arcade, and in the ambient plasma, so all these plasmas are likely of coronal origin. No significant plasma flows were detected.

AN OVER-AND-OUT HALO CORONAL MASS EJECTION DRIVEN BY THE FULL ERUPTION OF A KINKED FILAMENT

Over-and-out coronal mass ejections (CMEs) represent a broad class of CMEs that come from flare-producing magnetic explosions of various sizes but are laterally far offset from the flare, and their productions can be depicted by the magnetic-arch-blowout scenario. In this paper, we present observations of an over-and-out halo CME from the full eruption of a small kinking filament in an emerging active region (AR). In combination with the results of a derived coronal magnetic configuration, our observations showed that the CME was associated with a coronal helmet streamer, and the filament was located in the northern outskirts of the streamer base. Formed along a neutral line where flux cancellation was forced by the emerging AR with the surrounding opposite-polarity magnetic field, the filament underwent a full, non-radial eruption along the northern leg of the streamer arcade, accompanied by a clockwise deflection of the eruption direction. As a characteristic property of kink instability, the eruption displayed a clear inverse γ shape, indicative of a writhing motion of the filament apex. Coronal dimmings, including a remote one, formed in opposite-polarity footprint regions of the streamer arcade during the eruption, and the consequent CME was laterally offset from the AR. These observations suggest that the kink instability is likely to be the driver in the eruption. The event can be well explained by putting this driver into the magnetic-arch-blowout model, in which the eruption-direction deflection and the full-eruption nature of the kinking filament are caused by the guiding action of the streamer arcade and the external reconnection between them.

Coronal Dimmings and the Early Phase of a CME Observed with STEREO and Hinode/EIS

We investigate the early phase of the 13 February 2009 coronal mass ejection (CME). Observations with the twin STEREO spacecraft in quadrature allow us to compare for the first time in one and the same event the temporal evolution of coronal EUV dimmings, observed simultaneously on-disk and above-the-limb. We find that these dimmings are synchronized and appear during the impulsive acceleration phase of the CME, with the highest EUV intensity drop occurring a few minutes after the maximum CME acceleration. During the propagation phase two confined, bipolar dimming regions, appearing near the footpoints of a pre-flare sigmoid structure, show an apparent migration away from the site of the CME-associated flare. Additionally, they rotate around the ‘center’ of the flare site, i.e., the configuration of the dimmings exhibits the same ‘sheared-to-potential’ evolution as the postflare loops. We conclude that the motion pattern of the twin dimmings reflects not only the eruption of the flux rope, but also the ensuing stretching of the overlying arcade. Finally, we find that: i) the global-scale dimmings, expanding from the source region of the eruption, propagate with a speed similar to that of the leaving CME front; ii) the mass loss occurs mainly during the period of strongest CME acceleration. Two hours after the eruption Hinode/EIS observations show no substantial plasma outflow, originating from the ‘open’ field twin dimming regions.

ANALYSIS OF CHARACTERISTIC PARAMETERS OF LARGE-SCALE CORONAL WAVES OBSERVED BY THESOLAR-TERRESTRIAL RELATIONS OBSERVATORY/EXTREME ULTRAVIOLET IMAGER

The kinematical evolution of four extreme ultraviolet waves, well observed by the Extreme Ultraviolet Imager on board the Solar-Terrestrial Relations Observatory (STEREO), is studied by visually tracking wave fronts as well as by a semi-automatized perturbation profile method, which leads to results matching each other within the error limits. The derived mean velocities of the events under study lie in the range of 220-350 km s–1. The fastest of the events (2007 May 19) reveals a significant deceleration of ≈ – 190 m s–2, while the others are consistent with a constant velocity during wave propagation. The evolution of maximum-intensity values reveals initial intensification of 20%-70% and decays to original levels within 40-60 minutes, while the widths at half-maximum and full-maximum of the perturbation profiles broaden by a factor of two to four. The integral below the perturbation profile remains basically constant in two cases, while it shows a decrease by a factor of three to four in the other two cases. From the peak perturbation amplitudes, we estimate the corresponding magnetosonic Mach numbers M ms, which range from 1.08-1.21. The perturbation profiles reveal three distinct features behind the propagating wave fronts: coronal dimmings, stationary brightenings, and rarefaction regions. All features appear after the wave passage and only slowly fade away. Our findings indicate that the events under study are weak-shock fast-mode magnetohydrodynamic waves initiated by the CME lateral expansion.

NEW SOLAR EXTREME-ULTRAVIOLET IRRADIANCE OBSERVATIONS DURING FLARES

New solar extreme-ultraviolet (EUV) irradiance observations from the NASA Solar Dynamics Observatory (SDO) EUV Variability Experiment provide full coverage in the EUV range from 0.1 to 106 nm and continuously at a cadence of 10 s for spectra at 0.1 nm resolution and even faster, 0.25 s, for six EUV bands. These observations can be decomposed into four distinct characteristics during flares. First, the emissions that dominate during the flare's impulsive phase are the transition region emissions, such as the He II 30.4 nm. Second, the hot coronal emissions above 5 MK dominate during the gradual phase and are highly correlated with the GOES X-ray. A third flare characteristic in the EUV is coronal dimming, seen best in the cool corona, such as the Fe IX 17.1 nm. As the post-flare loops reconnect and cool, many of the EUV coronal emissions peak a few minutes after the GOES X-ray peak. One interesting variation of the post-eruptive loop reconnection is that warm coronal emissions (e.g., Fe XVI 33.5 nm) sometimes exhibit a second large peak separated from the primary flare event by many minutes to hours, with EUV emission originating not from the original flare site and its immediate vicinity, but rather from a volume of higher loops. We refer to this second peak as the EUV late phase. The characterization of many flares during the SDO mission is provided, including quantification of the spectral irradiance from the EUV late phase that cannot be inferred from GOES X-ray diagnostics.

Discovery in 1960 of the Flare Nimbus Phenomenon and Changes with Time in Its Interpretation

During the International Geophysical Year (IGY, 1957/1958) Dunsink Observatory near Dublin in Ireland was a World Data Centre for Solar Activity. In this circumstance, Hα Lyot Heliograph records secured on a daily basis between 07:00 – 14:00 UT at the Cape of Good Hope (then an integral link in a network of similar instruments contributing during the IGY to global monitoring of solar chromospheric activity) were routinely sent to Dunsink for analysis and dissemination. The investigations carried out at Dunsink on these data resulted, inter alia, in the discovery of the Flare Nimbus phenomenon. The nimbus comprises a dark expanding halo seen in the plage regions around major flares at, or within a few minutes of, the time of flare maximum intensity in Hα light. It reaches its greatest extent about 30 minutes after flare maximum. Its maximum dimensions (estimated visually) lie in the range 2 – 4×105 km and its duration ranges from ∼ 1 – 2 hours. Within the nimbus the striation pattern is either completely destroyed or loses its pre-flare configuration. An account of this phenomenon and its interpretation appeared primarily, although not exclusively, in the locally produced Dunsink Observatory Publications which are not now easily accessible to the world community of solar researchers. Also, at around the time when the nimbus was first identified and recorded in Lyot Heliograph data at several observatories, techniques in solar physics shifted towards high resolution narrow field observations. Under these conditions no further examples of the nimbus were recorded and the subject has remained dormant over several decades. The present paper again places the scientific results obtained with regard to the nimbus in the public domain, together with an account of the evolution within the scientific community of an explanation of this phenomenon. It is suggested here for the first time, in the light of present day data concerning coronal mass ejections (CMEs) and coronal dimming, that the nimbus provides a signature of CME-related reorganization of the magnetic field in the chromosphere (such that the transverse magnetic field component decreases and transforms into the line of sight component as the vector field stretches out). Coronal dimming provides a complementary signature of CME-related mass depletion in the corona.

SYMPATHETIC FILAMENT ERUPTIONS CONNECTED BY CORONAL DIMMINGS

We present for the first time detailed observations of three successive, interdependent filament eruptions that occurred one by one within 5 hr from different locations beyond the range of a single active region. The first eruption was observed from an active region and was associated with a coronal mass ejection (CME), during which diffuse and complex coronal dimmings formed, largely extending to the two other filaments located in quiet-Sun regions. Then, both quiescent filaments consecutively underwent the second and third eruptions, while the nearby dimmings were persistent. Comparing the result of a derived coronal magnetic configuration, the magnetic connectivity between the dimmings suggested that they were caused by the joint effect of simple expansion of overlying loop systems forced by the first eruption, as well as by its erupting field interacting or reconnecting with the surrounding magnetic structures. Note that the dimming process in the first eruption indicated a weakening and partial removal of an overlying magnetic field constraint on the two other filaments, and thus one can physically connect these eruptions as sympathetic. It appears that the peculiar magnetic field configuration in our event was largely favorable to the occurrence of sympathetic filament eruptions. Because coronal dimmings are frequent and common phenomena in solar eruptions, especially in CME events, it is very likely that they represent a universal agent that can link consecutive eruptions nearby with sympathetic eruptions.

SOLAR SOURCE AND HELIOSPHERIC CONSEQUENCES OF THE 2010 APRIL 3 CORONAL MASS EJECTION: A COMPREHENSIVE VIEW

We study the solar source and heliospheric consequences of the 2010 April 3 coronal mass ejection (CME) in the frame of the Sun-Earth connection using observations from a fleet of spacecraft. The CME is accompanied by a B7.4 long-duration flare, dramatic coronal dimming, and EUV waves. It causes significant heliospheric consequences and space weather effects such as radio bursts, a prominent shock wave, the largest/fastest interplanetary CME at 1 AU since the 2006 December 13 CME, the first gradual solar energetic particle (SEP) events in solar cycle 24, and a prolonged geomagnetic storm resulting in a breakdown of the Galaxy 15 satellite. This event, together with several following periods of intense solar activities, indicates awakening of the Sun from a long minimum. The CME EUV loop begins to rise at least 10 minutes before the flare impulsive phase. The associated coronal wave forms an envelope around the CME, a large-scale three-dimensional structure that can only be explained by a pressure wave. The CME and its preceding shock are imaged by both STEREO A and B almost throughout the whole Sun-Earth space. CME kinematics in the ecliptic plane are obtained as a function of distance out to 0.75 AU by a geometric triangulation technique. The CME has a propagation direction near the Sun-Earth line and a speed that first increases to 1000-1100 km s–1 and then decreases to about 800 km s–1. Both the predicted arrival time and speed at the Earth are well confirmed by the in situ measurements. The gradual SEP events observed by three widely separated spacecraft show time profiles much more complicated than suggested by the standard conceptual picture of SEP event heliolongitude distribution. Evolving shock properties, the realistic time-dependent connection between the observer and shock source, and a possible role of particle perpendicular diffusion may be needed to interpret this SEP event spatial distribution.