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Zhao Wu 1 , Yao Chen 1 , Gang Li 2 , L. Zhao 2 , R. W. Ebert 3 , M. I. Desai 3,4 , G. M. Mason 5. Observation and modeling of a CIR pair event. 1 School of Space Science and Physics, Shandong University at Weihai 2 CSPAR , University of Alabama in Huntsville
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Zhao Wu1, Yao Chen1, Gang Li2, L. Zhao2, R. W. Ebert3, M. I. Desai3,4, G. M. Mason5 Observation and modeling of a CIR pair event 1 School of Space Science and Physics, Shandong University at Weihai 2 CSPAR, University of Alabama in Huntsville 3 Southwest Research Institute 4 University of Texas at San Antonio 5 Applied Physics Laboratory, Johns Hopkins University
outline • Introduction What is CIR CIR and its associated particles Our question • Observation Unusual observations • Discussion propose our scenario explain the observation • Conclusion
1. Introduction - - CIRs • Corotating interaction regions (CIRs) • Major structure in the interplanetary space • The formation of CIRs • Solar rotation • Fast & slow solar wind overtake • Frozen in no penetration compression Pizzo,1978 • Observation of CIRs • increase at LE • decrease at TE • Forward & Reverse shock • (FS & RS)
1. Introduction – CIRs particles • Important particle accelerator • Ions: a few MeV/N; Electron: several hundred keV. • Peak around trailing edge (90%, Ebert, et al, 2012) Mann, et al 2002
1. Introduction -- motivation • Multiple CIRs structure exist • Multiple CIRs & particle acceleration Gomez et al., 2009
2. Observations • CIR pairs: time interval smaller than 5 days • 24 events in 2007-2008 • CIR pair in CR 2060
2. Observations - - energetic particle flux • Flux peak inbetween CIR I & II • Ions: up to 10 MeV Electron: hundreds of keV • Totally different from that of a single CIR WHY?
2. Observations -- anisotropy A: near the TE of CIR I Low flux, some isotropy C: Flux peak time Isotropy, inward flow ~ outward flow D: Declining phase Outward flow > inward flow B: Rising phase Inward flow > outward flow B: red (inward); blue (outward) Flux: the length of the sector
To summary the anisotropy • Anisotropic – Isotropic –Anisotropic • Inward flow dominate –equivalent – outward flow dominate WHY?
3. Discussion • Flux peak in between CIR I & II • The changing anisotropy • What caused these unusual observations? Particles are CIR origin (low solar activity, ratio of He/H ) Green: CIR value Blue: SEP value The direction reverse of magnetic field
3.1 Two possible scenario A B • Magnetic field line: connection to the Sun or U-shape topology. • A: CIR particles flow sunward
3.2 Peak flux • Larger heliocentric distance(R)---stronger accelerator • Closer to C --- MFL connect to larger R • Flux rises from B to C • Flux peaks around C • Flux decrease from C to D
3.3 Anisotropy • Particles accelerated at CIR I • B: inward > outward (No shock at CIR II, particle leakage) • C: inward ~ outward (RS & FS) • D: inward < outward (like B, direction reverse)
3.4 CSE & spectrum • Closed magnetic field --- Counter streaming electrons • Efficient accelerator --- harder spectrum
3.5 MHD simulation • To model the propagation of large scale structure • Transient phenomena grows up to large scale structure
4. Conclusion • The CIR pair event in CR2060 has several unusual observational features: • The time intensity peaks between the two CIRs. • The sense of the anisotropy changed in between the CIR-pair. • The presence of counter-streaming electrons between CIR1 and CIR2 …… • We conjecture that a U-shape magnetic field formed due to reconnection at high corona. • The U-shape magnetic field propagates out as a transient structure. • The 2D simulation support our scenario.
