Working Group 6

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SEP working group led by Olga E. Malandraki (Greece) and Alessandro Bemporad (Italy)

Scientific Objectives

The main objective of this Working Group, directly aligned with the ISEST science objectives,

is the improvement of our understanding of the origin, acceleration and transport of energetic

particles in the heliosphere, in association with Coronal Mass Ejections and Corotating

Interaction Regions (CIRs) propagation and evolution.

Scientific Questions

• What is the role of dynamical small-scale magnetic islands in the solar wind to the local particle acceleration in the solar wind?

• Study of particle signatures in the vicinity of the Heliospheric Current Sheet (HCS) – Multi-spacecraft observations

• What is the role of magnetic reconnection at the HCS to the particle energization?

• What is the effect of the HCS interaction with ICMEs / CIRs to the particle acceleration?

• How can the origin of SEPs be traced?

• What is the shock type at SEP injection site?

• What is the role of compression on SEP production?

• What is the solar cycle behavior of energetic protons and eruptive events? (solar cycle 23 vs solar cycle 24)

• What are the properties of SEP events as inferred from their associated radio emission?

Methodology and Implementation

• Study of the HCS crossing on 7 September 1999 as observed by the ACE and WIND spacecraft

• Identification of the HCS crossing, multiple Current Sheets observed and Magnetic islands identifications at both spacecraft

• Comparison of magnetic field and solar wind plasma parameters between the two spacecraft - evidence for magnetic merging of magnetic islands?

• Investigation of the HCS-CIR interaction during the August 2007 event using multi-spacecraft energetic particle observations (ACE, STEREO A & B)

• Study of the particle acceleration in Magnetic islands confined by an ICME and the HCS during the 23 May 2002 event (ACE/EPAM energetic particle observations)

(Olga Khabarova, Gary Zank, Gang Li, Olga E. Malandraki)

• Use of list of SEPs at Earth, triangulation analysis and SEP intensity

(Alexis Rouillard) In collaboration with WG1

• Tracing the origin of SEP events in the low corona via 3D reconstructions of the shock envelope

• Understanding of the shock type of SEP injection site. Methodology: estimate the shock normal angle to

B-field via 3D reconstruction of shock envelope and B-field model (PFSS) (e.g. see Kozarev et al. ApJ, 799, 167, 2015)

• Study of the role of compression on SEP production. (e.g. Schwandron et al., ApJ, 810:97, 2015)

Method: Measure CME lateral expansion low in the corona.

Open Questions under study: How common is this mechanism?

Is an EUV bubble (shock proxy) a necessary condition for SEPs?

What is the role of the flare-accelerated particles?

(Angelos Vourlidas)

• Use of 115 events SEP events at L1 and the respective proton enhancements ~68 MeV

• Proton release time at the Sun using the Velocity Dispersion Analysis (VDA)

• Associated radio emission for each event registered (both space and ground-based radio-spectrographs)

• Examination of the time difference of proton release with respect to the escape of keV electrons into space

• For the cases of type II radio association: estimation of the proton release heights from the height-time profile of the CME leading edge

(Athanasios Kouloumvakos, Alexander Nindos, Olga E. Malandraki)