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Flare footpoints and ribbons:The impulsive phase
H.S. Hudson
Space Sciences Lab, UC Berkeley
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
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”)
SMESE 11 March 2008 4/10
Kane & Donnelly 1971
Oda and Takakura observingsolar microwaves in 1948
SMESE 11 March 2008 5/10
GONG
SOHO/MDI
B dB
Sudol & Harvey (2005), flare of 2003 Oct. 29,line-of-sight field differences
SMESE 11 March 2008 6/10
Flare of 2001 Aug. 25:GONG + GOES
Other examples withGOES times
The changes are stepwise, of order10% of the line-of-sight field, andprimarily occur at the impulsive phase of the flare
SMESE 11 March 2008 7/10
First detection of solar flarevia total irradiance: gradualand impulsive phases!
(Woods et al. 2004, 2006)
SMESE 11 March 2008 8/10
CME acceleration at the impulsive phase
Zarro et al. 1999
Temmer 2008 (RHESSI ScienceNugget #71) http://sprg.ssl.berkeley.edu/~tohban/nuggets/
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
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”
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?
SMESE 11 March 2008 12/10
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Fletcher & Hudson 2008
New description of the impulsive phase
http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/
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 BLOS observed in the photosphere below a flare
• It suggests the need for further stereoscopic observation after STEREO, e.g. Solar Orbiter and the Sentinels