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The Flux-Rope Scaling of the Acceleration of Coronal Mass Ejections and Eruptive Prominences  

Christophe Marque   Submitted: 2006-07-17 05:56

The new flux-rope scaling law of the acceleration of coronal mass ejections (CMEs) derived by Chen and Krall (2003) (Paper 1) is quantitatively tested by comparing the theoretical prediction with the near-Sun acceleration profiles of 13 eruptive prominences (EPs) and four CMEs. A CME and associated EP are assumed to be organized by an underlying magnetic flux rope (MFR) with specific structural and geometrical relationships. The scaling law states that if the initial structure is a flux rope with a footpoint separation distance of Sf, then the height Zmax at which the acceleration measured at the centroid of the apex reaches maximum scales with Sf . The primary source of prominence data is the radio data from the archive of the Nobeyama Radio Observatory. A number of Hα events are also included. For CMEs, previously published events with good coverage of the initial acceleration are used. For each event, observed quantities are used to determine Sf and Zmax . It is shown that for the events included in the present study, Zmax scales with Sf in accordance with the scaling law. The result is consistent with the hypothesis that the pre-eruption magnetic structure underlying a CME and the associated EP is a flux rope driven by the toroidal Lorentz hoop force. The scaling law may constitute a quantitative observable discriminator of the pre-eruption magnetic geometry underlying CMEs/EPs and the driving force.

Authors: J. Chen, Ch. Marque, A. Vourlidas, J. Krall, P.W. Schuck
Projects: None

Publication Status: ApJ in press, 2006
Last Modified: 2006-07-17 07:24
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Solar Energetic Particles and Radio-Silent Fast Coronal Mass Ejections  

Christophe Marque   Submitted: 2006-02-07 09:03

Both solar flares and shock waves driven by fast coronal mass ejections (CMEs) can accelerate charged particles in the solar corona and create transient enhancements of solar energetic particle (SEP) fluxes in interplanetary space, known as SEP events. Since fast CMEs and flares often occur together, it is difficult to directly identify the actual source of the SEPs detected near Earth orbit. In this paper, we attempt to single out fast CMEs without any signature of particle acceleration related to a flare. In order to minimize effects of occultation by the solar limb, we choose meter wave radio emission from energetic electrons as a tracer of flare-related particle acceleration, because this emission arises at greater coronal heights than X-rays or centimetric radio waves. In truly radio-silent fast CMEs, where the absence of metric radio emission is not due to limb occultation, the only source of SEP acceleration should be the shock wave driven by the CME. In a systematic search in the early CME catalog of the SoHO/LASCO coronagraph (St. Cyr et al. 2000) for fast CMEs (V > 900 km s-1) located above the western solar limb between July 1996 and June 1998 we found 24 fast CMEs, of which only three were radio-silent. Comparison of their speeds with the fast magnetosonic speed in the corona shows that these three CMEs very likely drive coronal shock waves, and that their properties do not depart significantly from a reference set of SEP-associated fast CMEs, except for their angular width, which is smaller. Although one, possibly two of the three radio silent CMEs are accompanied by weak enhancements of the electron and proton fluxes (Ep < 20 MeV) observed by the particle detectors COSTEP aboard SoHO and EPAM aboard ACE, none produces a conspicuous SEP event. This suggests that either efficient particle acceleration at CME shocks occurs over much smaller angular ranges than generally believed or that the shock is not as efficient a particle accelerator at energies above ~10 MeV as often thought.

Authors: C. Marque, A. Posner, K.-L. Klein
Projects: None

Publication Status: ApJ (in press) 2006
Last Modified: 2006-02-07 09:03
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The Flux-Rope Scaling of the Acceleration of Coronal Mass Ejections and Eruptive Prominences
Solar Energetic Particles and Radio-Silent Fast Coronal Mass Ejections

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