The Wave–Driver System of the Off-Disk Coronal Wave of 17 January 2010

Abstract

We study the 17 January 2010 flare–CME–wave event by using STEREO/SECCHI-EUVI and -COR1 data. The observational study is combined with an analytic model that simulates the evolution of the coronal wave phenomenon associated with the event. From EUV observations, the wave signature appears to be dome shaped having a component propagating on the solar surface ($\overline{v}\approx280~\mathrm{km}\,\mathrm{s}^{-1}$) as well as one off-disk ($\overline{v}\approx 600~\mathrm{km}\,\mathrm{s}^{-1}$) away from the Sun. The off-disk dome of the wave consists of two enhancements in intensity, which conjointly develop and can be followed up to white-light coronagraph images. Applying an analytic model, we derive that these intensity variations belong to a wave–driver system with a weakly shocked wave, initially driven by expanding loops, which are indicative of the early evolution phase of the accompanying CME. We obtain the shock standoff distance between wave and driver from observations as well as from model results. The shock standoff distance close to the Sun (< 0.3 R _⊙ above the solar surface) is found to rapidly increase with values of ≈ 0.03 – 0.09 R _⊙, which gives evidence of an initial lateral (over)expansion of the CME. The kinematical evolution of the on-disk wave could be modeled using input parameters that require a more impulsive driver (duration t=90 s, acceleration a=1.7 km s⁻²) compared to the off-disk component (duration t=340 s, acceleration a=1.5 km s⁻²).