An Updated View of Solar Eruptive Flares and Development of Shocks and CMEs: History of the 2006 December 13 GLE-Productive Extreme Event

TL;DR

This paper analyzes the 2006 December 13 solar event, clarifying the relationship between eruptions, shocks, and flares, and supports the idea that shocks are excited early by erupting magnetic ropes rather than delayed CME-driven bow shocks.

Contribution

It provides new observational evidence that shocks are excited during flare rise by erupting magnetic ropes, challenging the delayed bow-shock acceleration scenario.

Findings

Two shocks observed, contradicting delayed bow-shock hypothesis.

Shocks formed early, before flare peak, capable of accelerating protons.

Shocks merged into a stronger one before decelerating.

Abstract

An extreme 2006 December 13 event marked the onset of the Hinode era being the last major flare in the solar cycle 23 observed with NoRH and NoRP. The event produced a fast CME, strong shock, and big particle event responsible for GLE70. We endeavor to clarify relations between eruptions, shock wave, and the flare, and to shed light on a debate over the origin of energetic protons. One concept relates it with flare processes. Another one associates acceleration of ions with a bow shock driven by a CME at (2-4)R_sun. The latter scenario is favored by a delayed particle release time after the flare. However, our previous studies have established that a shock wave is typically excited by an impulsively erupting magnetic rope (future CME core) during the flare rise, while the outer CME surface evolves from an arcade whose expansion is driven from inside. Observations of the 2006 December 13 event reveal two shocks following each other, whose excitation scenario contradicts the delayed CME-driven bow-shock hypothesis. Actually, the shocks developed much earlier, and could accelerate protons still before the flare peak. Then, the two shocks merged into a single stronger one and only decelerated and dampened long afterwards.