Working Group 2

Theory group led by Bojan Vrsnak (Croatia) and Yuming Wang (China)

A brief summary of the activity of WG1 at the workshop can be found here.

Objectives

• Initiation of CMEs and their take-off dynamics ("acceleration stage")

• Heliospheric dynamics of ICMEs and evolution of their structure

• Relationship between empirical, analytical, and numerical propagation models and comparison with observations; forecasting aspects

• CME/ICME-associated phenomena (flares, shocks, SEPs, etc.)

• Together with WG3, WG2 should provide a "theoretical-background service" to WG1 and WG2

---

---

Scientific Questions

Which mechanisms, processes, forces are governing the CME take-off and ICME propagation?

2.1.1 What is the role of the flare-associated reconnection?

2.1.2 What is the role of emerging flux and poloidal-flux injection?

2.1.3 How long the Lorentz force dominates over the aerodynamic drag

2.1.4 How the inductive effects affect the CME eruption and ICME propagation?

2.1.5 What is the role of the ICME/ambient-field reconnection?

2.1.6 How to measure the real mass of ICMEs?

---

How much variable ambient conditions affect ICMEs?

2.2.1 Which processes are involved in ICME-ICME interactions?

2.2.2 How ICME-ICME interactions affect the dynamics and structure of ICMEs?

2.2.3 How high-speed solar wind streams (corotating interacting regions) affect ICMEs?

2.2.4 How the ICME-driven shock forms and evolves in the decreasing Alfven-velocity environment?

2.2.5 How ambient solar wind exchanges momentum, energy and magnetic flux with ICMEs?

2.2.6 What is the morphological shape of an ICME?

2.2.7 How does the morphological shape change and evolve from the Sun to the Earth?

---

What is the state of the art in the ICME-arrival and ICME-geoeffectiveness forecasting?

2.3.1 What are forecasting-performances of various empirical, analytical, and numerical models?

2.3.2 How well models reproduce heliospheric kinematics of ICMEs?

2.3.3 What are the key model-input parameters?

2.3.4 What can be done regarding the geomagnetic-activity forecasting?

2.3.5 What processes determine the ICME Forbush-decrease effectiveness?

---

The CME-associated phenomena

2.4.1 What are the mechanisms of initiation and what is the nature of CME-driven coronal waves and shocks?

2.4.2 What is the role of flares in the initiation and acceleration of CMEs?

2.4.3 What can we learn from coronal dimmings?

2.4.4 How the associated phenomena (flares, waves, dimmings) can help in the space-weather forecasting?

2.4.5 How SEPs are accelerated by shocks and how they transport in heliosphere?

---

---

Results of the Workshop and Future Plans/Collaborations

The tasks in the coming year:

3.1 Addressing aerodynamics of ICMEs in IP space

• Drag force/coefficient, external forces, internal forces, …
• Participants:
  • Bojan Vrsnak, Jie Zhang, Christian Moestl, Yuming Wang, Fang Shen, Valbona Kunkel, ……
• Models & Methods:
  • Drag model, flux rope model, Triangulation methods, spherical methods, ……

3.2 Addressing deflection of ICMEs’ propagation

• Which conditions, How significant, Physical mechanisms, ……
• Participants:
  • Manuela Temmer, Chenglong Shen, Noe Lugaz, ……
• Models & Methods:
  • GCS model, Triangulation methods, spherical methods, ……

3.3 Addressing CME arrival

• Compare models, input/output parameters, ……
• Participants:
  • Nandita Srivastava, Luciano Rodriguez, Philippe Lamy, Yuming Wang, Dusan Odstrcil, Chin-Chun Wu, ……
• Models & Methods:
  • CME auto-detection methods, cone models, Drag model, ENLIL model, HAF model, WSA model, ……