F: Coronal Mass Ejections,
Alphonse Sterling (20)
Last Updated Fri Dec 5 16:24:42 2008
| 1: Gemma Attrill (gattrill@cfa.harvard.edu), Smithsonian Astrophysical Observatory [F] |
| [soi] On 1st September 2008 I successfully defended my PhD thesis entitled: Low coronal signatures of CMEs: coronal 'waves' and dimmings. A central component of my thesis work has been to develop a model for understanding the development of CMEs in the low corona. This model intrinsically links diffuse coronal 'wave' bright fronts, coronal dimmings and the associated CME. I therefore feel that I can make a strong and relevant contribution to discussions and data analysis on this subject. I have experience with analysing both solar and in-situ data. Part of my thesis work has shown that there appear to be two different types of coronal dimming evident in EUV data, that appear in conjunction with CMEs - (i) deep, core dimmings, commonly identified as the footpoints of the magnetic flux rope and (ii) secondary dimmings, which often appear as a more widespread, transient dimming that manifests behind the expanding coronal \"wave\" bright front. I expect that this widespread dimming also contributes to the mass of the CME, since its angular extent matches that of the CME. This is particularly evident in cases where the CME is large-scale in the low corona (so where there is a strong lateral expansion, as opposed to the case where there is simply a radial expansion away from the Sun). I would be very interested in work on whether the mass of the CME can be accounted for by mass deficits in the core dimming regions alone, or whether the extended, more subtle dimming should also perhaps be considered. I believe that this widespread dimming also exists even for the famous 12th May 1997 event, which is often cited as a difficulty for work that strives to link the development of coronal 'waves' and dimmings because the core dimmings remain located near to the post-eruptive arcade, whilst the coronal 'wave' bright front expands right across the disk. There is, in fact, a subtle dimming that expands, following the bright front right across the solar disk - this dimming cannot simply be dismissed as being due to noise as the intensity of the pixels in this dimmed region show a non-Gaussian distribution. This widespread dimming is also clearly evident in the limb CME event observed by STEREO-EUVI on 25th January 2007 (Attrill et al., 2007, Astron. Nach). I believe that these dimmings must play a role in the mass contribution to the associated CME, but they are a feature that are not widely acknowledged or studied. I am also interested in the connection between the angular extent of the CME and the characteristics of the source region - what determines whether a CME becomes large-scale in the low corona? In my thesis, I made a study of limb CMEs from January 1997 - June 1998. I find that less than 20% of the CMEs reach a lateral extent of greater than 2R_sun when at a distance of less than 3R_sun from the solar surface. Why do only some CMEs behave like this, becoming so dramatically large-scale in the low corona? Furthermore, this study shows that where a front-side origin can be identified for the CME (e.g. post-eruptive arcade, dimming, filament eruption), _every_ large-scale CME has an associated diffuse coronal 'wave' bright front. I believe that a thorough understanding of CMEs must include consideration of diffuse coronal 'wave' bright fronts as well as dimmings. This connection is the focus of working group F. Concerning the eruption's evolution in interplanetary space, Attrill et al., (2006), Solar Physics, demonstrated how study of the evolution of coronal dimmings could be used to derive insights into the post-eruption connectivity of the ICME. The model for coronal 'wave' bright fronts presented in Attrill et al., (2007), ApJL and in Attrill et al., (2007), Astron. Nach. show that if the diffuse coronal 'wave' bright front is understood as the magnetic footprint of the CME, then the magnetic connectivity of the ICME can be determined. E.g. persistent brightenings at the edge of coronal holes are identified as sites of interchange reconnection, where the CME at that location is disconnected from the Sun. Combined with study of any rotation characteristics of coronal 'wave' bright fronts an understanding of the ICME magnetic connectivity and orientation, and therefore potential geo-effectiveness can be derived. Recent work (Attrill et al., 2008, Solar Phys) tackling the question of how coronal dimmings recover supports the identification of deep, core coronal dimmings (transient coronal holes) as the footpoints of CMEs (e.g. Sterling and Hudson 1997; Webb et al., 2000). Kahler and Hudson (2001) questioned this relationship, believing that the identification of transient coronal holes as the source regions of magnetic clouds is unjustified, citing the recovery of the dimmings before the observation of associated magnetic clouds at 1 AU as implication of a complete disconnection of the magnetic flux rope from the Sun. However, if the dimmings are understood to recover via interchange reconnections with surrounding small closed/emerging loops (Attrill et al., 2008), then the 'open' flux forming the dimmings is dispersed, so recovering the intensity of the dimming, whilst still maintaining the magnetic connectivity of the ICME to the Sun. This work therefore directly concerns the connection of ICMEs to their source regions on the Sun. I hope this can be of interest/use in discussions in this workshop. I would really love to participate in Working Group F. I feel I can make a valuable contribution, and I would definitely welcome the opportunity to meet and discuss, in person, with the participants of this group. After months of thesis writing, it would be really great to reconnect (pardon the pun...) with the CME-dimmings-coronal wave community again. |
| [poster] Coronal 'waves' and dimmings - what can they tell us about their CME counterparts? Diffuse coronal 'waves' can be understood as the magnetic footprint of a CME. In this model, the expansion of the core CME magnetic field drives successive reconnections with the surrounding magnetic field environment. The outermost shell of the CME is progressively stepped further and further from the source region, generating a diffuse coronal 'wave' bright front, as well as (i) deep core dimmings and (ii) widespread secondary dimmings. We apply this model to some of the events that are the focus of Working Group F, in an endeavour to establish a definitive connection between CMEs, their low coronal counterparts and therefore their source regions on the Sun. |
| 2: Ed Cliver (edward.cliver@hanscom.af.mil), Air Force Research Laboratory [E] |
| [soi] I would like to apply OSPaN (formerly ISOON) digitized H-alpha data to solar eruptions to help elucidate the initiation mechanism. |
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| 3: Len Culhane (jlc@mssl.ucl.ac.uk), Mullard Space Science Lab., UK [E] |
| [soi] Interested in the initiation and eruption of CMEs and the associated flares, their passage through the IPM and their arrival at Earth when that happens. Have most recently been working on the event of 19 May 2007 and considered both the associated flare and the CME which appears to be due to two filaments - one AR and one quiescent that merge before the eruption |
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| 4: Russell Howard (russ.howard@nrl.navy.mil), NRL [C] |
| [soi] I have a long interest in characterizing the relation between CMEs and surface phenomena. I am generally skeptical of drawing cause and effect conclusions from timing relationships. I would like to add a contrarian view. |
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| 5: Linda Hunt (Linda.A.Hunt@nasa.gov), SSAI/NASA LaRC [B] |
| [soi] |
| [poster] Effects of solar variability on the energy balance of the thermosphere The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite measures the vertical distribution of infrared radiation emitted by various atmospheric gases (ozone, water vapor, nitric oxide, and carbon dioxide), providing important information about the radiation budget in the upper atmosphere. From these measurements, the infrared power and energy radiated by nitric oxide (NO) and carbon dioxide (CO2) have been computed. It has been demonstrated that NO, in particular, acts as a natural thermostat, providing a mechanism for solar storm energy to be lost from the atmosphere via infrared emission. A new version (Version 1.07) of the SABER data set has been released and new computations of flux, power and energy have been made with these data over the full mission timeline (2002-2008). A pubic database of the computed daily zonal power values is being developed. Cooling by the atomic oxygen fine structure line at 63 um based on atmospheric model profiles will also be computed and included in the database. Results for the new data version and comparison with the previous version will be presented. The seven-year span of this data set provides information on long-term solar variability, and the inclusion of more recent data aids the search for evidence of the start of solar cycle 24. These data provide fundamental information on the climate of the thermosphere and enable detailed investigation of short and long-term variability as a function of latitude. |
| 6: Ying Liu (liuxying@ssl.berkeley.edu), UC Berkeley [C] |
| [soi] |
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| 7: James McAteer (james.mcateer@tcd.ie), Trinity College Dublin [I] |
| [soi] The kinematics of CMES are studied in detail to gain insight into both the early evolution (below 2 solar radii) and late stage evolution (great then 50 solar radii). In both cases we study the leading egde in full 3D coordiates from STEREO and SOHO. Early stage evolution shows a peak in acceleration around 1.5 solar radii. Late stage development show little evidence of an interplanetary drag force |
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| 8: Ron Moore (ron.moore@nasa.gov), NASA/MSFC/NSSTC [B] |
| [soi] |
| [poster] Title: The Flare/CME Connection.Authors: Ron Moore, David Falconer, Alphonse Sterling. Abstract: Moore, Sterling, & Suess (2007, ApJ, 668, 1221) present evidence that (1) a CME is typically a magnetic bubble, a low-beta plasmoid-with-legs having roughly the 3D shape of a light bulb, and (2) in the outer corona the CME plasmoid is in lateral pressure equilibrium with the ambient magnetic field. They present three CMEs observed by SOHO/LASCO, each from a very different source located near the limb. One of these CMEs came from a compact ejective eruption from a small part of a sunspot active region, another came from a large quiet-region filament eruption, and the third CME, an extremely large and fast one, was produced in tandem with an X20 flare arcade that was centered on a huge delta sunspot. Each of these CMEs had more or less the classic light-bulb silhouette and attained a constant heliocentric angular width in the outer corona. This indicates that the CME plasmoid attained lateral magnetic pressure balance with the ambient radial magnetic field in the outer corona. This lateral pressure balance, together with the standard scenario for CME production by the eruption of a sheared-core magnetic arcade, yields the following simple estimate of the strength BFlare of the magnetic field in the flare arcade produced together with the CME: BFlare ~ 1.4(AngleCME/AngleFlare)^2 Gauss, where AngleCME is the heliocentric angular width of the CME plasmoid in the outer corona and AngleFlare is the heliocentric angular width of the full-grown flare arcade. Conversely, AngleCME ~ (RSun)^-1(FluxFlare/1.4)^1/2 radians, where FluxFlare is the magnetic flux covered by the full-grown flare arcade. In addition to presenting the three CMEs of Moore, Sterling, & Suess (2007) and their agreement with this relation between AngleCME and FluxFlare, we present a further empirical test of this relation. For CMEs that erupt from active regions, the co-produced flare arcade seldom if ever covers the entire active region: if FluxAR is the total magnetic flux of the active region, FluxFlare < FluxAR, and we predict that AngleCME < (RSun)^-1(FluxAR/1.4)^1/2 radians. For a random sample of 31 CMEs that erupted from active regions within 30 degrees of the limb, for each CME we have measured AngleCME from LASCO/C3 and have measured FluxAR from a SOHO/MDI magnetogram of the source active region when it was within 30 degrees of disk center. We find that each CME obeys the above predicted inequality, none having width greater than half of the upper bound given by FluxAR . Thus, an active region's magnetic flux content, together with its location on the solar disk, largely determines whether the active region can possibly produce a CME that is wide enough to intercept the Earth.This work was supported by NASA's Science Mission Directorate through its Heliophysics Guest Investigators Program and its Living With a Star Targeted Research & Technology Program, and by NSF through its SHINE Program. |
| 9: Nariaki Nitta (nitta@lmsal.com), LMSAL [E] |
| [soi] I would like to understand how the properties of CMEs reflect their low coronal signatures. I have some experiences of comparing CMEs and ICMEs. |
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| 10: Jaz Pearson (jazpearson@gmail.com), University of Central Lancashire [D] |
| [soi] For the past year i have been using STEREO (SECCHI) to look at CMEs. Using a variety of techniques we have been able to track a CME from initiation in the EUVI right out into the HI2 field of view. We have also used a number of techniques to work out a CMEs angle of propagation, and thus understand some of the physical properties (eg. velocity) that a CME may possess. |
| [poster] We present preliminary analysis of a coronal mass ejection (CME) from the 25th March 2008, using SECCHI observations aboard the STEREO spacecraft. From initiation, we observe the CME in EUVI at 171 Angstroms. We then track the CME with the coronagraphs (COR1 and COR2) and then out into interplanetary space (STEREO A only) with the Heliospheric Imagers (HI1 and HI2). We track the CME's position, speed and angle of propagation, using two techniques and compare our results. Using the HI data we calculate an angle of propagation of 67 degrees (plus/minus 12.5 degrees) and with the EUVI data an angle of approximately 78 (plus/minus 4 degrees). |
| 11: Monique Pick (Monique.Pick@obspm.fr), Observatoire de Paris [E] |
| [soi] I am interested by the multiwavelength data analysis of CME events: initiation, development and flare association. I work on the May 19 2007 event at present time. |
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| 12: Kimberley Steed (ks3@mssl.ucl.ac.uk), UCL - MSSL [J] |
| [soi] My research interests include investigating the structure, propagation and evolution of interplanetary coronal mass ejections (ICMEs), particularly those termed magnetic clouds. Combining observations of ICMEs of both the Sun and in situ near Earth using multiple spacecraft allows us to directly investigate the magnetic topology of the erupting structure prior to, during and post-eruption, and understanding the magnetic topology of the structure is crucial to understanding how and why an eruption occurred. Some of the techniques I have employed in my study of magnetic clouds include the fitting of magnetic clouds to a cylindrical, force-free model, inferring the geometry of a magnetic cloud from solar observations and estimating the time of eruption of a magnetic cloud using in situ near Earth observations. |
| [poster] Using ACE in situ data we identify and describe an interplanetary magnetic cloud (MC) observed near Earth on 13 April 2006. We use multi-instrument and multi-wavelength observations from SOHO, TRACE and ground-based observatories to determine the solar source of this MC. Here we present the evidence that supports the link between an eruption in a small, spotless, northern hemisphere active region and this magnetic cloud, despite the presence of a number of larger active regions on the Sun which initially appeared to be more probable source regions of the MC. This event highlights the complexities associated with locating the solar source of an ICME observed near Earth, and serves to emphasise that it is the combination of a number of physical characteristics and signatures that is important for successfully tying together the Earth-end and the Sun-end of an event. Further investigation of this MC has revealed some sub-structure towards its centre, observed in the azimuthal magnetic field component of the MC. We explore several possible explanations for this signature, including multiple flux ropes and warping of the magnetic cloud. We also consider whether magnetic reconnection plays a role in creating the geometry which would explain these observations. |
| 13: Alphonse Sterling (alphonse.sterling@nasa.gov), NASA/MSFC/ISAS [F] |
| [soi] Group Leader |
| [none] |
| 14: Yingna Su (ynsu@head.cfa.harvard.edu), Smithsonian Astrophysical Observatory [J] |
| [soi] My contribution to Group F (Coronal Mass Ejections) is: I can help on collecting data sets of the candidate events from Hinode/XRT and TRACE. I may also help with NLFFF modeling of the pre-CME magnetic configuration in order to understand the magnetic configuration of the erupting region at the Sun.My interest in Group J (Filaments and Prominences) is: I am interested in mutli-wavelength observations and NLFFF modeling of the magnetic configuration of filaments/filament channels. |
| [poster] We will present preliminary results of an investigation on filament channels observed by Hinode/XRT and STEREO/EUVI. We selected 8 filament channels which are located in active region remnants. Filament channels 1, 2 and 3 appear to be the same channel observed at different solar rotations, and channels 5, 6, 7 and 8 are also the same channel at different solar rotations. We study the X-ray and EUV structures as well as the evolution of these channels observed by Hinode/XRT and STEREO/EUV. The corresponding H-alpha filament information is provided by KSO and MLSO. In order to understand the magnetic configuration of filament channels, we will also explore non-linear force-free field modeling of two selected filament channels. The modeling is based on flux rope insertion method, and the magnetic field information is provided by SOLIS. |
| 15: Virendra K. Verma (vkvermadr@rediffmail.com), Uttrakhand Space Application Center [E] |
| [soi] I have carried out detailed study about north south asymmetry of solar active phenomena for duration of 6-24 solar cycle. Our study show that N-S asymmetry of 24th solar cyccle is southerly dominated as predicted by Verma (1992). References:Verma, V. K. 1992, ASP, 27, 429.[For GROUP F] The CMEs observed by LASCO coronagraph and associated solar activity phenomena whose locations were identified by EIT instruments and solar Ha flares observations during years 2000-2005 indicate that about 40%, 26% and 30% CMEs were observed when there were coronal holes (CHs) within 1-10, 11-20 and 21-40 degrees, respectively from the location of solar Ha flares. The CHs data used in the study were taken from KPNO, USA website. From the study carried out in the present paper we are of the view that CMEs might have been produced by some mechanism by which the mass ejected by some solar flares or active prominences, gets connected with open magnetic lines of CHs (source of high speed solar wind streams) and moves along them to appear as CMEs as suggested earlier by Verma and Pande(1989), Verma(1992) and Verma(2002). In this paper we have also discussed the detail scenario about the origin of solar coronal mass ejections which are confirmed by the recent observations of LASCO and EIT. References Verma, V. K. & Pande, M. C. (1989) Proc. IAU Colloq. 104 (Poster Papers), Standford University, Stanford, USA, p.239. Verma, V. K. (1992) Indian Journal Radio & Space Phys. , 21, 64. Verma, V. K. (2002) COSPAR Colloquia Series, 13, 319. |
| [poster] On the North-South Asymmetry of Solar Active Phenomena during 24th Solar Cycle Abstract. We report here a study of various solar activity phenomena occurring in both north and south (N-S) hemispheres of the Sun during solar cycles 6-24(1821-2008). In the study we have used sunspot data, H- alpha flare index data, solar X-ray flares and solar active prominences data. Earlier Verma (1992) reported long-term cyclic period in N-S asymmetry and also predicted that the N-S asymmetry of solar activity phenomena during solar cycles 21, 22, 23 and 24 will be south dominated. and the N-S asymmetry will shift to north hemisphere in solar cycle 25. The present study shows that N-S asymmetry of solar active phenomena has the long period of 11 solar cycles which further shows that the N-S asymmetry may be southern dominated during solar cycles 24 and 25 and N-S asymmetry may shift to northern hemisphere during solar cycle 26. The present study shows that the N-S asymmetry during solar cycles 22, 23 and 24 are southern dominated and comfirm the prediction of Verma (1992). The cause of the long term N-S asymmetry of solar phenomena is not known but may be due to internal structure of the Sun. References: Verma, V. K. 1992, ASP, 27, 429.[For group F] Abstract. The CMEs observed by LASCO coronagraph and associated solar activity phenomena whose locations were identified by EIT instruments and solar Ha flares observations during years 2000-2005 indicate that about 40%, 26% and 30% CMEs were observed when there were coronal holes (CHs) within 1-10, 11-20 and 21-40 degrees, respectively from the location of solar Ha flares. The CHs data used in the study were taken from KPNO, USA website. From the study carried out in the present paper we are of the view that CMEs might have been produced by some mechanism by which the mass ejected by some solar flares or active prominences, gets connected with open magnetic lines of CHs (source of high speed solar wind streams) and moves along them to appear as CMEs as suggested earlier by Verma and Pande(1989), Verma(1992) and Verma(2002). In this paper we have also discussed the detail scenario about the origin of solar coronal mass ejections which are confirmed by the recent observations of LASCO and EIT. References Verma, V. K. & Pande, M. C. (1989) Proc. IAU Colloq. 104 (Poster Papers), Standford University, Stanford, USA, p.239. Verma, V. K. (1992) Indian Journal Radio & Space Phys. , 21, 64. Verma, V. K. (2002) COSPAR Colloquia Series, 13, 319. |
| 16: Angelos Vourlidas (vourlidas@nrl.navy.mil), Naval Research Laboratory [C] |
| [soi] Present 3D observations of CME initiation using SECCHI data. |
| [talk] |
| 17: Yuming Wang (ymwang@ustc.edu.cn), University of Science & Technology of China [J] |
| [soi] For WG-F, I am interested in the CME expansion and propagation throughout the interplanetary space, and the success or failure of the flux-rope ejections (or called confined and eruptive flares). I would like to show our most recent work, in which two physical parameters, the polytropic index (\Gamma) of CME plasmas and non-force-free index (I_nff), as well as their variations could be unscrambled based on observations of the CME expansions and propagations. Besides, if possible, I would like to present a poster about our paper published in 2007, in which confined and eruptive X-class flares were compared. For WF-J, I am interested in the 3D topology and dynamics of filaments as will as their relationship with CMEs. At the present stage, I have my students being worked on the 3D reconstruction of filaments. I would like to present a poster about our recent progress at the meeting. |
| [poster] 1. (WG-F) Title: A Comparative Study between Eruptive X-class Flares Associated with Coronal Mass Ejections and Confined X-class Flares. Abstract: From 1996 to 2004, about 90% of X-class flares are eruptive, but the remaining 10% are confined. To probe why the largest energy releases could be either eruptive or confined, we investigate four X-class events from each of the two types. Both sets of events are selected to have very similar intensities and duration in soft X-ray observations, to reduce any bias due to flare size on CME occurrence. We find that the occurrence of eruption (or confinement) is sensitive to the displacement of the location of the energy release, defined as the distance between the flare site and the flux-weighted magnetic center of the source active region. The displacement is 6 - 17 Mm for confined events but as large as 22 - 37 Mm for eruptive events. Further, we use the potential field source-surface model to infer the coronal magnetic field above the source active regions and calculate the flux ratio of low (<1.1 Rs) to high (>1.1 Rs) corona. We find that the confined events have a lower ratio (<5.7) than the eruptive events (>7.1). These results imply that a stronger overlying arcade field may prevent energy releases in the low corona from being eruptive, resulting in flares, but without CMEs. 2. (WG-J) Title: Solar LImb Prominence CAtcher and Tracker (SLIPCAT).Abstract: Prominences are a long-observed but still not well understood phenomenon in the solar atmosphere. They have a close connection to CMEs, which is also not clear enough so far. We are developing an automated system - Solar LImb Prominence CAtcher and Tracker (SLIPCAT), to outline and track the prominence from the STEREO/SECCHI EUVI 304 A images. The 3D reconstruction of prominences is under development. |
| 18: David Webb (david.webb@hanscom.af.mil), Boston College [J] |
| [soi] Origin and development of CMEs; relation to prominences, dimmings, etc.; WHI transients during CR 2067-2069; SECCHI and SMEI data |
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| 19: Meredith Wills-Davey (meredith@head.cfa.harvard.edu), Smithsonian Astrophysical Observatory [D] |
| [soi] Interested in CME origins, specifically how they relate to large-scale coronal waves and dimming regions. Particularly interested in the properties of large-scale coronal waves and the connections between the lateral dynamics of dimming regions and CMEs. |
| [none] |
| 20: Vasyl Yurchyshyn (vayur@bbso.njit.edu), Big Bear Solar Observatory [C] |
| [soi] Coronal mass ejections (CMEs) and their interplanetary counterparts, interplanetary CMEs (ICMEs) usually exhibit a complex structure that very often includes a magnetic cloud (MC), which is thought to be a magnetic fluxrope. Id like to briefly review the association between coronal ejecta and the post eruption aracdes and their relationship in terms of magnetic flux budget, magnetic orientation and twist. Our recent study indicates the orientation of a halo CME elongation may correspond to the orientation of the underlying flux rope. Among other, we will compare orientation angles of elongated LASCO CMEs, both halo and partial to the EIT post eruption arcades (PEA). Data for 100 events had been analyzed and er report the following: i) it is further supported that majority of halo CMEs are elongated in the direction of the aixial field of PEA arcades. This relationship is found to be weeker for partial CME and those events that originate further from the disk center. There also is an indication that events in the northern hemisphere generally exhibit better correlation that those in the southern hemisphere. |
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Second Choice
Gemma Attrill, Cilia Damiani, Yan Li, Paulett Liewer, Yang Liu, Mari Paz Miralles, Karin Muglach, Richard Nightingale, Olga Panasenco, Lawrence Sparks, Alphonse Sterling, Leif Svalgaard, Stephen White,