Bifurcation of the metric type II radio emission associated with the giant

solar flare of April 2 2001

S. Mancuso and L. Abbo(2004, A&A, 415, L17)

Okamoto Takenori

Abstract

• Bifurcation– on April 2 2001, X20 flare.– the radio emission lanes, which is very

rare• Model

– the interaction of a piston driven shock with a vertical current sheet

– the model replicates successfully the observed bifurcation

– the magnetic reconnection was triggered in the current sheet by the shock wave passage

bifurcation

bifurcation

type II burst

NiCT/HiRAS

streamer axis and CME

The axis of symmetry of the expanding bubble does not coincide with the streamer axis.

CME

roughly circular shape

SOHO/LASCO

ModelThe frequencies of the type II were emitted at the two intersections of the expanding shock surface with the streamer axis.

Model

• Radio bursts– selectively produced– in the densest parts (along streamer axes)– the strength of fast-mode shocks can be very

much enhanced

• The shock wave passage– triggers magnetic reconnection just above the

AR the ejection of a supermagnetosonic plasmoid another shock

CME fronts

CME/Linear fit

UVCS

DPS

LASCO

Second shock

second shock

Conclusions

• The bifurcation of the radio type II emission was produced by a curved fast shock surface intersecting a vertical current sheet above an AR.

• The shock wave may have triggered magnetic reconnection in the current sheet, causing the ejection of a second plasmoid.

• Redio emitting inward propagating shocks should occur more often.– The emission of the positively drifting lanes

fades quickly.