Coronal Waves and Dimmings: Insights into CME Connectivity

1. Figure from Thompson et al., 2000 Two different types of coronal wave? (e.g. Gopalswamy et al., 2000; Biesecker et al., 2002; Vrsnak, 2005) “S”-wave Diffuse bright front Coronal waves and dimmings - what can they tell us about their CME counterparts? Gemma Attrill Harvard-Smithsonian Astrophysical Observatory PhD Thesis Low coronal signatures of CMEs: Coronal “waves” and dimmings University College London, Mullard Space Science Laboratory

2. 25 January 2007 9 April 2008 26 April 2008 Diffuse coronal wavemaps footprint of CME in the low corona Study of large-scale limb CMEs from January 1997 - June1998 (Attrill, PhD Thesis, 2008). Where a front-side origincan be identified for the CME (e.g. post-eruptive arcade, dimming, filamenteruption), EVERY large-scale CME has an associated diffuse coronal wavebright front.

3. Magnetic Flux through CH: + = 4.1 x 1021 (± 9.1x 1020) Mx - = -2.9 x 1021 (± 8.3x 1020) Mx CH boundary retreat Bright fronts can be used to determine CME connectivity in interplanetary space. Persistent brightenings can be due to interchange reconnection(Attrill et al., 2006; 2007).

4. Coronal dimming - locations of plasma evacuation (i) deep, core dimmings, commonly identified as thefootpoints of the magnetic flux rope (e.g. Sterling & Hudson, 1997; Webb et al., 2000; Attrill et al., 2006) (ii) secondary dimmings, which oftenappear as a more widespread, transient dimming that manifests behind theexpanding coronal wave bright front (Attrill et al., 2007). A diffuse coronal “wave” can be understood as the magneticfootprint of a CME (Attrill et al., 2007). Expansion of the core CME magnetic fielddrives successive reconnections with the surrounding magnetic fieldenvironment. The outermost shell of the CME is progressively stepped further from the source region, generating the diffuse brightfront, as well as both the deep core dimmings and widespread secondarydimmings. We expect that the widespread (secondary) dimmingalso contributes to the mass of the CME, since its angular extent matches that ofthe CME (Thompson et al., 2000).

5. Balance of net magnetic flux in dimmings - proper identification of all CME source regions Mandrini et al., (2007)

6. Recovery of coronal dimmings - connectivity to the Sun Early-stage recovery: • Study of the evolution of coronal dimmings can be used to derive insights into the post-eruption connectivity of the ICME (Attrill et al., 2006; Crooker and Webb, 2006). • TCH identified as source of temporary fast solar wind stream that interacted with CME. Complex relationship between departed CME and plasma outflow from dimmings. (Ivanov et al., 2003; Odstrcil et al., 2005; Attrill et al., 2006; McIntosh, 2008) Long-term recovery: Why and how do coronal dimmings disappear whilst the magnetic connectivity of the CME ejecta to the Sun is maintained? • Recovery can be due to interchange reconnections facilitating dispersal (as opposed to disconnection)of “open” flux (Attrill et al., 2008) ∆Area/∆Time coronal dimmings = 2.6 x 105 km2 s-1 Fisk and Zurbuchen (2006) c.f. Diffusion coefficient,  = 1.6 x 105 km2 s-1(Fisk and Schwadron, 2001).

7. Poster today: F01 Attrill First Hinode/XRT and STEREO/EUVI observations of a coronal “wave” event Conclusions: Coronal waves and dimmings when studied in the context of their global magnetic surroundings can give useful information regarding the connectivity and origin of the mass supply of the associated ICME. Importance of the surrounding global magnetic environment Gemma Attrill, Alec Engell, Meredith Wills-Davey, Paolo Grigis, Paola Testa, Aad van-Ballegooijen