IGPP, March Coronal shock waves observed in images H.S. Hudson SSL/UCB

IGPP, March Outline How coronal imaging should help with understanding shock waves Origins of large-scale coronal waves Mach numbers

IGPP, March Conclusions Large-scale coronal waves originate in compact magnetic structures The Mach numbers in the corona are low We can’t yet image the CME flow field in the corona (ie, below coronagraph occulting edges)

IGPP, March What coronal shocks should look like… Korreck et al., 2004

IGPP, March Chandra E

IGPP, March Imaging of coronal shocks: good news and bad news A shock wave should provide a sharp density gradient, easy to detect in images We can observe motions in two dimensions The medium is optically thin => confusion The wave may not be bright compared with other flare components The corona generally has low plasma beta, so the observed mass may not be structurally important

IGPP, March … Only imaging can properly characterize the large-scale structure The solar corona isn’t really accessible any other way

IGPP, March Imaging of coronal shocks Type II bursts (plasma radiation) Moreton waves (H  in the chromosphere) New modalities: EIT, X-rays 1, microwaves, meter waves, He Three events: Khan & Aurass (2002); Narukage et al. (2002); Hudson et al. (2003)

IGPP, March Type II burst

IGPP, March Moreton-Ramsey wave and EIT wave Thompson et al., 1998

IGPP, March G. A. Gary, Solar Phys. 203, 71 (2001) CH Mann et al., A&A 400, 329 (2003) Gopalswamy et al., JGR 106, (2001) (v A ~ 200  -1/2 km/s ?)

IGPP, March Direct X-ray observation Uchida 1968 Yohkoh 1998 EIT

IGPP, March Why X-ray waves are hard to observe directly

IGPP, March Field and energy are concentrated in active regions Active-region magnetic fields via Roumeliotis-Wheatland technique (McTiernan) Mass loading via empirical law (Lundquist/Fisher)

IGPP, March Lundquist et al., SPD 2004

IGPP, March NOAA 10486, Haleakala IVM data,  cube Roumeliotis-Wheatland-McTiernan method pixel size ~3000 km ScaledNot scaled

IGPP, March Heliospheric shocks in images? Maia et al., ApJ 528, L49 (2000) Vourlidas et al., ApJ 598, 1392 (2003) SOHO/UVCS

IGPP, March Vourlidas et al., ApJ 598, 1392 (2003) Where is the bow shock ?

IGPP, March Inferring the Mach number

IGPP, March X-ray signal S ~ n e 2 f(T) f(T) ~ T 2 d(ln(S))/d(ln(n)) ~ 2  Mach number estimate for 6 May 1998 event

IGPP, March Movie of dimming (Aug 28, 1992) Coronal Dimming

IGPP, March Dimming observed spectroscopically Harra & Sterling, ApJ 561, L216, 2001

IGPP, March UVCS shock observations Raouafi et al., A&A 434, 1039, 2004 Mancuso et al., A&A 383, 267, 2002 Raymond et al., GRL 27, 1439, 2000

IGPP, March Cartoon illustrating wave origins cf.

IGPP, March The CME-driven shock in the corona The CME involves outward plasma motions perpendicular to the field We see the result of these motions as dimmings, but the data are not good enough to follow the flows nor to see a bow wave There is an Alfven-speed “hole” in the middle corona in which Mach numbers could be larger

IGPP, March SUMMARY Coronal shock waves (metric type II) are blast waves (Uchida) launched by compact structures at flare onset. These propagate in an undisturbed corona The CME eruption restructures the corona and pushes a bow wave ahead of it into the solar wind. This creates a type II burst at long wavelengths

IGPP, March Conclusions Large-scale coronal waves originate in compact magnetic structures The Mach numbers in the corona are low We can’t yet image the CME flow field in the corona (ie, below coronagraph occulting edges)

IGPP, March END

IGPP, March Flare and CME energy partition