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Progenitors to Geoeffective Coronal Mass Ejections: Filaments and Sigmoids David McKenzie, Robert Leamon Karen Wilson, Zhona Tang, Anthony Running Wolf PROM Workshop, September 30, 2003
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CMEs: Different sources, different effects? Focus on two specific kinds of CME progenitors: erupting filaments and coronal sigmoids Both have been modeled with flux rope structure Differences in associated ICMEs (Leamon et al 2002) –Phase of leading field reversal –Hemispheric rule of handedness Goal: Capitalize on the differences
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Proposed Work Investigate systematic differences in magnetic clouds resulting from eruption of filaments and sigmoids, e.g., –Temperature depression –Increase in magnetic field strength and plasma β –Composition (ion charge state distribution) Test if magnetic field strength can be linked to CME acceleration Examine correlation between magnetic cloud tilt angle and duration of southward IMF Explore relationship of progenitor axial field and overlying PFSS field “If the potential for geoeffectiveness depends on the details of the pre-eruption magnetic structures, can the characteristics of magnetic clouds at 1 au be related statistically to measurements made via remote sensing?”
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Baby steps Assemble list of geomagnetic storms –Cane & Richardson (2003) –Zhang et al (2003) –Leamon et al (2002) –Webb (p.c.), Jones (p.c.) Collect solar wind data from ACE, Wind –magnetic field strength & direction –proton density –alpha/proton density ratio –temperature Average conditions within magnetic cloud Fit flux rope model to in situ data Associate each magnetic cloud with its progenitor, compare two populations
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Preliminary, very preliminary Choice of sixteen geoeffective magnetic clouds –9 sigmoids –7 non-active region filaments Very small sample: “Lies, damn lies, and sigmoids” density velocity temp α/p ratio Dst (cm -3 ) (km/s) (kK) Filaments 9.8 ± 1.5 482 ± 26 40.7 ± 5.8 5.6 ± 1 -115 ± 30 Sigmoids 6.6 ± 1.6 492 ± 38 47.7 ± 9.6 6.6 ± 1.5 -144 ± 25 Different Same Inconclusive Inconclusive Inconclusive
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To do More events tied to their progenitors and flux rope models Incorporate photospheric magnetic field measurements PFSS relationships This work supported by NASA Grant NAG5-13500, Living With a Star Targeted Research & Technology
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