Interplanetary proton and electron enhancements associated with radio-loud and radio-quiet CME-driven shocks P. Mäkelä 1,2, N. Gopalswamy 2, H. Xie 1,2, S. Akiyama 1,2, S. Yashiro 1,2 (1) The Catholic University of America, Washington DC, USA; (2) NASA Goddard Space Flight Center, Greenbelt MD, USA; pertti.makela; nat.gopalswamy; hong.xie; sachiko.akiyama; Shock waves driven by coronal mass ejections (CMEs) traveling in the solar corona and in interplanetary (IP) space can accelerate particles. Type II radio bursts and shock-associated increases of particle flux are two important signatures of particle acceleration of a shock. However, acceleration efficiency of the shock depends on properties of the shock itself and of the ambient medium it encounters, which both evolve as the shock propagates further out from the Sun. Type II bursts are due to beams of shock accelerated electrons propagating along IP magnetic field lines, and they are widely accepted to be associated with CMEs [1]. However, the converse association does not necessarily hold. Even fast and wide CMEs that are expected to be energetic enough to drive strong shocks are not always associated with type II bursts [e.g., 2]. These events are generally called radio-quiet (RQ) to distinguish from radio-loud (RL) events that have a type II burst either in metric (low corona) or in decameter-hectometric (DH; IP space) wavelengths, or both. Shock-associated increases of electrons and protons are observed in the vicinity of IP shocks, and they are generally called energetic storm particle (ESP) events [3] or shock spikes depending on the time profile of the flux increase [e.g., 4]. The time profiles of the shock-associated increases varies greatly from event to event [e.g., 5,6]. In order to understand the time evolution of shock acceleration in transient shocks we have conducted a statistical survey of RQ and RL CME-driven shocks and shock-associated increases of IP particle flux. Introduction Results Summary Data analysis Starting point is the list of CME-driven shocks observed by the ACE 1, the SOHO 2, and/or the Wind 3 spacecraft during 1996–2006 [7]. CMEs were identified from the SOHO/LASCO CME catalogue 4. Solar source (flare) locations were obtained from GOES X-ray (Solar Geophysical Data) and SOHO/EIT EUV observations. Shock parameters are from the database 5 by J. Kasper or from the analysis of magnetic field (MF) and plasma data using the Shock and Discontinuities Analysis Tool [SDAT, 8]. For shock drivers we used the Wind magnetic cloud list 6 or inspected the plasma and MF data. The existence of metric type IIs is checked using published ground-based observations, and that of DH bursts using the list 7 by the Wind/WAVES team or inferred from the dynamic spectra. Particle observations were provided by ACE/EPAM in the 66–4750 keV and by SOHO/ERNE in the 1.8– 50.1 MeV range. Particle events were classified into keV and MeV range events based on the highest-energy channel where the shock-associated increase was observable. We also searched for shock-associated enhancements in the 38–53 keV electron measurements made by ACE/EPAM. A total of 230 CME-driven shocks in (4 shocks have inconclusive radio data and are excluded from the analysis). Shock-associated increases in RQ shocks are less frequent and less intense than those in RL shocks, but radio-quietness and the lack of shock-associated increases at 1 AU are not strictly correlated. CMEs and shocks evolve while traveling in the inner corona and in IP space. Shock acceleration efficiency of electrons and ions are not connected to each other in a straightforward manner as type II emission by electrons requires wave production and their conversion to radio waves. In shock-associated events accelerated particles do not have to escape from the shock front; for type II bursts, the accelerated electrons have to escape the shock front to produce Langmuir waves. Electron acceleration during RQ shocks is observed mainly in quasi-perpendicular shocks. Acknowledgments. We would like to thank the ACE Science Center and all the ACE, SOHO and Wind instrument and data analysis teams for providing the data for analysis. SOHO is an international cooperation project between ESA and NASA. This research was supported by NASA grant NNX08AD60A. References [1] Cane et al., 1987, JGR 92, [2] Gopalswamy et al. 2008, ApJ 674, 560. [3] Bryant et al., 1962, JGR 67, [4] Tsurutani & Lin, 1985, JGR 90, 1. [5] van Nes et al., 1984, JGR 89, [6] Lario et al., 2005, in Proc. Solar Wind 11-SOHO 16 (Noordwijk: ESA), 81. [7] Gopalswamy et al., 2009, ApJ, accepted. [8] Viñas & Scudder, 1986, JGR 91, 39. Data lists on the Web: 1) 2) 3) 4) 5) 6) 7) (See also Fig 1. Radio emission and particle flux associated with the 11 September 2005 RL (left) and the 5 October 2000 RQ shock (right). Both combined dynamic spectra of RSTN and Wind/WAVES show type III bursts (~19:45 and ~03:30 UT), but the type II burst is missing in the October 2000 event on the right. The dashed white line marks the first observation time of the associated halo CMEs by the SOHO/LASCO coronagraph. The particle fluxes by ACE/EPAM reveal a shock-associated increase at the time (dotted line) the shock reached L1 and the ACE spacecraft. Fig 2. Source locations of RQ (top) and RL (bottom) shocks with and without shock- associated increase in (a) the keV and (b) the MeV energy range. Fig 3. Shock speed vs CME speed for RQ and RL shocks. RL shocks have lower speeds at 1 AU than the associated CMEs near the Sun, indicating shock deceleration during propagation from the Sun. Shock-associated increases correspond MeV range events. Fig 4. Shock normal angle θ Bn vs solar source (flare) longitude for RQ and RL shocks. RQ shocks with shock-associated increases tend to have θ Bn & 60 °. For behind the limb sources the unknown longitude is set to 91°. Shock-associated increases correspond MeV range events. Fig 5. Size of the shock- associated proton flux increase vs shock speed (left) and CME speed (right) for RQ and RL shocks. Shock- associated increases for RQ shocks are smaller in size and have lower shock/CME speed. Fig 6. Size of the shock- associated electron increase vs shock speed (top) and CME speed (bottom) for RQ and RL shocks. Difference in the event size between RQ and RL shocks is more clear than for protons in Fig. 5. Fig 7. Size of the shock- associated electron increase vs the shock normal angle θ Bn. Most of the RQ events have θ Bn & 60° as was the case for protons in Fig. 4. Shock enhancements of proton flux keV rangeMeV range RLRQRLRQ 80%65%52%33% Shock enhancements of electron flux 39%20%-- θ Bn & 60 ° with shock enhancement 53%60%55%64% θ Bn & 60 ° without shock enhancement 32%46%44%47% Table 1. Event statistics