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Published byClementine Bond Modified over 9 years ago
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SUB-GROUP 1: Surface Solar Magnetic Fields The central question: Can we infer the orientation of Bz of an ICME at 1 AU by focusing on the study of the surface magnetic fields? A. Nindos: Examined chirality of source region using photospheric magnetograms and coronal information (SXT & EIT), applied the coronal flux-rope model to infer the orientation of the leading edge and then compared the result with IP measurements.. Results: (1)Agreement in ~65% (12/19) of cases regarding the sign and the orientation of the field (2) In 8 cases there was no magnetic cloud (MC) at 1 AU (3) Completion of work using all unambiguously identified sources will follow.
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V. Yurchyshyn: Test with two active region cases: (1)11/7/04: X2.0 flare and CME event. Erupted filament with a magnetic field orientation roughly agreeing with the orientation of the MC (2)4/9/01: System of loops disappeared in SXT. Their orientation agreed roughly with the orientation of the MC at 1 AU. NOTE: Both exercises are not automatic. Visual inspection required. Results: (1) Two cases in which the orientation of the erupting feature agreed with MCs' orientation Additional test: Compared the CME launch speed with the Dst index of the subsequent disturbances. As a result, Vasyl found that the geoeffectiveness of an ICME seems to correlate well with the CME's launch speed.
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We’ve reached a consensus that surface magnetic fields are indeed very useful in predicting the geoeffectiveness of ICMEs, at least in some of the events HOWEVER: (1)We need more reliable ways to infer the coronal magnetic fields (calculated or measured) (2)We need more reliable MC models (3)The task is worthy but currently the technique is not able to predict the geoeffectiveness of ICMEs on a routine basis. The process is not automatic.
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M. K. Georgoulis: A quantitative approach based solely on the photospheric magnetic fields. An array of tools applicable only to vector magnetograms: (1)Resolution of the 180-deg azimuthal ambiguity (2)Calculation of the photospheric velocity field vector as a solution of the ideal induction equation (3) Evaluation of the energy-helicity formula in the linear force-free approximation. Upgrade to a nonlinear force-free method in preparation.
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RESULTS: (1)There seems to be significant quantitative difference between flare/CME prolific active regions and quiescent active regions in terms of the total helicity budget and the percentage of the free magnetic energy over the total magnetic energy in the configuration (2)One case showed distinctive flow differences 30 min before a M2 flare and a CME (3)In one case of an X3 flare the total magnetic helicity / free energy decreased after the event, thus allowing a lower-limit estimation of the event’s helicity and free energy content NOTES: (1)More active region cases obviously needed (2)Large error bars in several cases because of the lff approximation (3)Obviously, no mention about the geoeffectiveness of CMEs. Combined studies required
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OVERALL CONSENSUS: Magnetic helicity is an important tool for understanding the process of CME initiation However, there are still several gaps in the understanding of the CME triggering process – moreover, several analysis tools need to be refined We need help! More people need to become involved, and more data need to be contributed. If the above results are backed up by a sufficient statistical sample of cases, a promising forecasting ability may emerge
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