1. Flare footpoints and ribbons: The impulsive phase H.S. Hudson Space Sciences Lab, UC Berkeley

2. SMESE 11 March 2008 2/10 Contents History & Nomenclature - Impulsive phase and gradual phase - Other things (Krucker) Magnetic changes (Fletcher) TSI observations Flares and CMEs (Zhang, Temmer) Flare waves (Regnier?) Implosions (Ji) Conclusions

3. SMESE 11 March 2008 3/10 Flare-related ionospheric effects SPA (“Sudden Phase Anomaly”) => soft X-rays SFD (“Sudden Frequency Deviation”) => EUV burst SCNA, SES, SWF, … The Neupert effect could be anticipated in 1971 (or earlier) via the SPA/SFD comparison (Donnelly 1969) Kane & Donnelly (1971) introduced the term “impulsive phase” (cf. Joan Vorpahl thesis; H  “flash phase”)

4. SMESE 11 March 2008 4/10 Kane & Donnelly 1971 Oda and Takakura observing solar microwaves in 1948

5. SMESE 11 March 2008 5/10 GONG SOHO/MDI B dB Sudol & Harvey (2005), flare of 2003 Oct. 29, line-of-sight field differences

6. SMESE 11 March 2008 6/10 Flare of 2001 Aug. 25: GONG + GOES Other examples with GOES times The changes are stepwise, of order 10% of the line-of-sight field, and primarily occur at the impulsive phase of the flare

7. SMESE 11 March 2008 7/10 First detection of solar flare via total irradiance: gradual and impulsive phases! (Woods et al. 2004, 2006)

8. SMESE 11 March 2008 8/10 CME acceleration at the impulsive phase Zarro et al. 1999 Temmer 2008 (RHESSI Science Nugget #71) http://sprg.ssl.berkeley.edu/~tohban/nuggets/

9. SMESE 11 March 2008 9/10 Flare-related large-scale waves Metric type II wave / Moreton wave (blast wave) Ejection-driven wave (CME bow shock) - Mewaldt et al. (2004), Emslie et al. (2005) find of order 10% total flare energy in SEPs Seismic wave in solar interior (Kosovichev-Zharkova) The motions of these waves originate in the field restructuring that provides the energy

10. SMESE 11 March 2008 10/10 Implosive motion Veronig et al. 2005 Hudson 2000 Liu et al. 2005 http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/ “Magnetoisobar” “Bald patch”

11. SMESE 11 March 2008 11/10 Conclusions The impulsive phase is extremely energetic It can be seen all across the electromagnetic spectrum and in mechanical forms as well The impulsive phase is characterized by large-scale effects reflecting intermittent and unresolved elements So… what is the physics of the impulsive phase?

12. SMESE 11 March 2008 12/10 Fletcher & Hudson 2008 New description of the impulsive phase http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/

13. SMESE 11 March 2008 13/10 How does this cartoon help? It is a useful application to astrophysics of lessons learned in space plasmas It takes a different and healthy approach to the major flare problem of electron beam stability It acknowledges a recent solar observational breakthrough - the stepwise changes in B LOS observed in the photosphere below a flare It suggests the need for further stereoscopic observation after STEREO, e.g. Solar Orbiter and the Sentinels