Mass Ejection Onset Research Articles

DERIVING THE PROPERTIES OF CORONAL PRESSURE FRONTS IN 3D: APPLICATION TO THE 2012 MAY 17 GROUND LEVEL ENHANCEMENT

ABSTRACT We study the link between an expanding coronal shock and the energetic particles measured near Earth during the ground level enhancement of 2012 May 17. We developed a new technique based on multipoint imaging to triangulate the three-dimensional (3D) expansion of the shock forming in the corona. It uses images from three vantage points by mapping the outermost extent of the coronal region perturbed by the pressure front. We derive for the first time the 3D velocity vector and the distribution of Mach numbers, M FM, of the entire front as a function of time. Our approach uses magnetic field reconstructions of the coronal field, full magnetohydrodynamic simulations and imaging inversion techniques. We find that the highest M FM values appear near the coronal neutral line within a few minutes of the coronal mass ejection onset; this neutral line is usually associated with the source of the heliospheric current and plasma sheet. We illustrate the variability of the shock speed, shock geometry, and Mach number along different modeled magnetic field lines. Despite the level of uncertainty in deriving the shock Mach numbers, all employed reconstruction techniques show that the release time of GeV particles occurs when the coronal shock becomes super-critical (M FM > 3). Combining in situ measurements with heliospheric imagery, we also demonstrate that magnetic connectivity between the accelerator (the coronal shock of 2012 May 17) and the near-Earth environment is established via a magnetic cloud that erupted from the same active region roughly five days earlier.

A benchmark event sequence for mass ejection onset studies

Aims. In this study, we report on the spectroscopic observations of a particularly well-observed flare and coronal mass ejection (CME) event sequence which we feel can be used as a benchmark study for CME onsets. Methods. Specifically, we report on a set of extreme-ultraviolet (EUV) spectroscopic observations using the Solar and Heliospheric Observatory (SOHO) to determine features of the CME onset process revealed through the analysis of plasma at different temperatures. Results. The flare which occurred on the north-western limb was associated with a large CME. The event in question showed evidence for pre-flare ascending loops containing 1-2 million K plasma, which disappeared just prior to the flare. This disappearance is interpreted as coronal dimming, and it appears to coincide with the projected mass ejection onset time. In addition, a discrete, short-lived coronal loop containing plasma at transition region temperatures was detected just prior to this eruption. This loop displayed mass motion, along flux tubes, with oppositely directed flows. The nature and timing of this transient loop suggest a close relationship between it and the eruption process. Examinations of the timing and topology, which extend previous studies considerably, are found to be consistent with the mass ejection onset interpretation of Zhang and co-workers. Conclusions. The clarity of this event sequence suggests that we should regard it as a benchmark in studies of the mass ejection onset process.

Flare‐associated Coronal Disturbances Observed with the Norikura Green‐Line Imaging System. I. A Coronal Mass Ejection Onset

We present the first detection of an onset of a coronal mass ejection (CME) in the coronal green-line emission (Fe XIV λ5303, 2 MK) by the two-dimensional Doppler coronagraph NOGIS (Norikura Green-Line Imaging System) at the Norikura Solar Observatory, National Astronomical Observatory of Japan. On 2003 June 1-2, NOGIS continuously observed the birthplace of a that originated in a complex of two neighboring magnetic flux systems across the solar equator: a flare-productive NOAA Active Region 10365, and a bundle of face-on coronal loops overlaying a quiescent filament. An early precursor of the event was a density enhancement of a 2 MK plasma in between the two flux systems. Following a filament eruption from NOAA AR 10365 that was observed by the Transition Region and Coronal Explorer (TRACE) in the 195 A passband (1.6 MK), NOGIS observed a blueshifted bubble and a redshifted wave that almost simultaneously expanded from the boundary of NOAA AR 10365 and the overlying dense region. The redshifted wave propagated toward the face-on loop system and triggered a damping oscillation in Doppler shifts among the adjacent loops within the system. The blueshifted bubble propagated both inward and upward. The inward motion triggered an M6.5 flare in AR 10365, while the upward motion evolved into a partial halo that had an angular extent covering the latitudinal range of the two flux systems. Differing from typical disturbances that evolve within a single flux system with a bipolar arcade on its center, our event proceeded via interaction, which was a presumably magnetic reconnection between separatrices of the two flux systems. These observational properties may suggest the existence of CME corridors in multiple complex flux systems, from which huge CMEs can be launched.

Multi-wavelength study of a coronal mass ejection: a flare event from AR#9393

The active region, AR#9393, produced a number of intense flares during March–April 2001. In this paper, we report the analysis of an X1.1 flare event of April 2, 2001 and its associated coronal mass ejection. The timing and location of the H α eruption, radio burst activities, and the onset of mass ejection suggest an energy release that occurred close to the surface of the sun. At this region, as shown by the magnetogram, X-ray and EUV images, the field configuration was complex and the 3-D extrapolation revealed the presence of a magnetic null point. Results also suggest that the energy release is followed by the magnetic reconnection between the low-lying loops near the separator point and outlying loops. This study provides the support for the magnetic break-out process to trigger the energy release in eruptive flare event.

On the Coronal Mass Ejection onset and Coronal Dimming

A comprehensive case and statistical study of CME onsets has been conducted on the solar limb using the CDS, LASCO and EIT instruments aboard the SOHO spacecraft. This is the first dedicated campaign to establish firmly the EUV signatures of CME onsets and is based on a series of low-corona observing campaigns made in 2002. The event database consisted of 36 multiple emission line sequences observed with CDS and the study builds, in particular, on studies of EUV coronal dimming which have been associated with CME onsets. We witness a range of dimming events in EUV coronal emission line data. Shorter events, commonly of duration 4 hours) appear to be either due to coronal evolution or rotational effects. However, for some CME onsets, where the CDS pointing was appropriate, no dimming was observed. Dimming observed in EIT typically occurred immediately after the launch of a loop or prominence, and in 5 out of 9 events there is evidence of a matter buildup within the loop before launch. A total of 10 events occurred where CDS was used to directly observe the CME footprint, but no relationship between these events was found. The results suggest that the response of the corona to a CME launch differs between the low (1.0 R⊙≤R≤1.2 R⊙) and middle (1.2 R⊙<R≤2.0 R⊙) corona regions, hence implying a difference between dimming observations conducted with different instruments.

UV spectroscopy with SOHO

The UV spectroscopy from SOHO has provided new and exciting results from a wide range of phenomena observed on the Sun. Determination of plasma parameters such as velocity, density, temperatures, line widths and abundances have provided new physical insight into fundamental problems in solar physics. These include magnetic reconnection, quiet Sun coronal heating, active region dynamics, flows in solar flares, formation of the solar wind, determination of coronal mass ejection onset, characteristics of coronal waves and the twisting of magnetic structures. This paper will review these results and discuss what can be achieved with future spectroscopic instrumentation.

Coronal dimming and the coronal mass ejection onset

A set of five observations of extreme-ultraviolet (EUV) coronal dimming associated with coronal mass ejection (CME) activity is examined. Using spectroscopic data, plasma characteristics across a broad range of temperatures from 20 000 K to 2 million K are determined. The dimming events are found to coincide in time, and to coincide spatially, with the projected onset times and locations of the associated CMEs. The spectral data confirm that the dimming is due to mass- loss, and not temperature variations. The actual mass-loss calculated from the degree of dimming, using two dierent methods, shows that the extracted mass in each case, is of the same order as the mass of the associated CME. In some cases, the EUV observations are limited to relatively small regions under the CME events and it is expected that we do not witness the mass- loss associated with the entire event, for these. However, we believe that this analysis has provided a method for locating the source region of the trigger for a CME eruption, and that the dimming characteristics can be used to distinguish between onset processes of the CME. In particular, the gradual nature of the dimming process, which takes place over several hours, suggests that either the CME has a continuous driver rather than a sudden impulsive onset, or the low coronal response to a CME extends over a long period.

The association of transequatorial loops in the solar corona with coronal mass ejection onset

It has been shown that transequatorial loops can disappear in association with the onset of a coronal mass ejection (CME) (Khan & Hudson 2000). We extend this result by considering a larger sample of transequatorial loop systems (TLS) to investigate their associated flaring and CME activity. We find 10 of a total 18 TLS considered here to be associated with flaring and CME onset originating from a connected active region. A total 33 cases of flaring and associated CME onset are observed from these 10 systems during their lifetime. We observe the influence of this activity on the TLS in each case. In contrast to the Khan & Hudson result, we find evidence that transequatorial loop eruption leading to soft X-ray brightening equivalent in temperature to a B-class flare is equally as common as dimming in the corona. Consequently we conclude that the scenario observed by Khan & Hudson is not universal and that other types of CME-TLS association occur. It was found that for transequatorial loops that were associated with CMEs the asymmetry in longitude was larger than for those that were not associated to a CME by 10degrees. In addition, the extent in latitude (as a measure of the loop length) was nearly twice as large for those TLS associated with CMEs than those that were not. The asymmetry in latitude was actually on average larger for those TLS not associated with CMEs, than for those that were. This suggests that differential rotation is not a major contributor to the production of CMEs from transequatorial loops. Instead it is more likely for a CME to be produced if the loop is long, and if there is a large asymmetry in longitude. The implications of these results for CME onset prediction are discussed.

Material Outflows from Coronal Intensity “Dimming Regions” during Coronal Mass Ejection Onset

One signature of expulsion of coronal mass ejections (CMEs) from the solar corona is the appearance of transient intensity dimmings in coronal images. These dimmings have generally been assumed to be due to discharge of CME material from the corona, and thus the are thought of as an important signature of the sources of CMEs. We present spectral observations of two dimming regions at the time of expulsion of CMEs, using the Coronal Diagnostic Spectrometer (CDS) on the SOHO satellite. One of the dimming regions is at the solar limb and associated with a CME traveling in the plane of the sky, while the other region is on the solar disk and associated with an Earth-directed halo CME. From the limb event, we see Doppler signatures of approximately equal to 30 kilometers per second in coronal (Fe XVI and Mg Ix) emission lines, where the enhanced velocities coincide with the locations of coronal dimming. This provides direct evidence that the dimmings are associated with outflowing material. We also see larger (approximately equal to 100 kilometers per second). Doppler velocities in transition region (0 v and He I) emission lines, which are likely to be associated with motions of a prominence and loops at transition region temperatures. An EIT accompanies the disk event, and a dimming region behind the wave shows strong blue-shifted Doppler signatures of approximately equal to 100 kilometers per second in 0 v, suggesting that material from the dimming regions behind the wave may be feeding the CME.

IACG Campaign III: Solar events and their manifestation in interplanetary space and in geospace

In Spring 1994 the Inter Agency Consultative Group Campaign III was set up at a kick-off meeting in Sagamihara, Japan. The basic idea of Campaign III was to coordinate solar, interplanetary and near-Earth spacecraft in an effort to link solar and near-Earth observations relating to activity such as solar mass ejections, and features such as corotating interaction regions. The Campaign was split into two basic activities, namely (i) studies of the onset of mass ejections, and (ii) studies of the effects of mass ejections and other solar phenomena at the Earth. The onset of the Campaign activities was effectively linked to the launch date of the Solar and Heliospheric Observatory (SOHO) spacecraft, since most of the planned activities centred on use of SOHO data linked to other spacecraft. SOHO was launched in December 1995 and the onset of full scientific operations was in March/April 1996. At the time of writing the more complex, time consuming multiple instrument operations such as the ones required for the IACG campaign have not been run, though pilot studies between selected instruments have been performed. Thus, we have preliminary observations relevant to the Campaign, and we anticipate the full campaign tobe run on several occasions before the end of the year. In this paper, we report on the IACG Campaign III concept and on the preliminary results from the pilot studies.

Comment on “The solar flare myth” by J. T. Gosling

Journal of Geophysical Research: Space PhysicsVolume 100, Issue A5 p. 7917-7919 Papers on Solar and Heliospheric Physics CommentariesFree Access Comment on “The solar flare myth” by J. T. Gosling M. I. Pudovkin, M. I. PudovkinSearch for more papers by this author M. I. Pudovkin, M. I. PudovkinSearch for more papers by this author First published: 1 May 1995 https://doi.org/10.1029/94JA03033Citations: 7AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References Akasofu, S.-I., S. Yoshida, The structure of the solar plasma flow generated by solar flares, Planet. Space Sci., 15, 39, 1967. Cane, H. V., The evolution of interplanetary shocks, J. Geophys. Res., 90, 191, 1985. Gold, T., Plasma and magnetic fields in the solar system, J. Geophys. Res., 64, 1665, 1959. Gosling, J. T., The solar flare myth, J. Geophys. Res., 98, 18,937, 1993. Harrison, R. A., E. Hildner, A. J. Hundhausen, D. G. Sime, G. M. Simnett, The launch of solar coronal mass ejection: Results from the coronal mass ejection onset program, J. Geophys. Res., 95, 917, 1990. Ivanov, K. G., N. V. Mikerina, Ground level geomagnetic effects of interplanetary shocks fronts from powerful isolated flares of the nearby zone (in Russian), Geomagn. Aeron., 20, 508– 514, 1980. Ivanov, K. G., N. V. Mikerina, Powerful isolated flares of the near zone and the connection of the magnetic field of bipolar groups with the field of interplanetary flare throws and with geomagnetic disturbances (in Russian), Geomagn. Aeron., 21, 34– 38, 1981. King, J. H., The Interplanetary Medium Data Book, National Space Science Data Center, Greenbelt, Md., 1977. Piddington, J. H., Cosmic electrodynamics, 87, John Willey, New York, 1969. Pudovkin, M. I., A. D. Chertkov, Magnetic field of the solar wind, Sol. Phys., 50, 213– 229, 1976. Pudovkin, M. I., S. A. Zaitseva, I. P. Oleferenko, Magnetic field of the flare stream, in Russian, Izv. Acad. Nauk SSSR Ser. phys., 41, 242– 251, 1977. Pudovkin, M. I., S. A. Zaitseva, A. D. Chertkov, E. M. Fomina, The structure and geoefficiency of high velocity solar wind streams, Solar-Terrestrial Predictions Proceedings, , 3 F. Donnelly, B56– 65, U.S. Department of Commerce, Washington, 1980. Sheeley, N. R., R. A. Howard, M. J. Koomen, D. J. Michels, R. Schwenn, K. H. Mühlhäuser, H. Rosenbauer, Coronal mass ejections and interplanetary shocks, J. Geophys. Res., 90, 163, 1985. Citing Literature Volume100, IssueA51 May 1995Pages 7917-7919 ReferencesRelatedInformation

The launch of solar coronal mass ejections: Results from the coronal mass ejection onset program

We describe a set of solar coronal mass ejection (CME) events where coincident data sets from both X ray and white light instruments have been made available through deliberate planning. Using these we have been able to put tight limits on possible descriptions of the typical sequence of events, and these we relate to interpretations of models involving flares and CMEs. Our findings confirm recent suggestions that CME onsets precede any related flare activity and that the associated flaring commonly lies to one side of the CME span. The CME launch appears to be associated with minor X ray (flare precursor) activity. Although this scenario has been previously discussed (see Harrison, 1986, and references therein), the abundance of flare and CME models which are not compatible with this picture demands that confirmation be sought using programs such as this.

The relationship between coronal mass ejections and solar flares

X-ray observations show that at a time consistent with a coronal mass ejection onset there is a small, soft X-ray burst (precursor). Generally this is followed some 20–30m later by a more significant flare. At the onset time there is frequently simultaneous activity from widely separated points on the Sun (>10 5 km). We present a model which accounts for the relationship between the coronal mass ejection and the precursor using 10 2–10 3 keV protons as the energy transfer agent. The protons (1) heat the high coronal loop. Inferred from the simultaneous activity, destabilizing the pressure balance to produce the ejection and (2) are guided by the magnetic field to below the transition region where they heat the chromospheric plasma to produce the precursor X-rays. High correlation between these events and a subsequent flare suggests that there may be a feedback mechanism operating from the coronal mass ejection.