STEREO observed stealth CME

Introduction

Figure 1: Schematic view of the CME that erupted on June 1st 2008, projected on the ecliptic plane (top view). The separation angle between the A and B spacecraft was <math>53^{\circ}</math>. The CME traveled towards STEREO B and was clearly visible in coronagraph images from STEREO A.

The twin STEREO probes are two identical spacecraft, one flying ahead (A) of the Earth and one flying behind it (B). They were launched on Wednesday, October 25th, 2006 from Cape Canaveral, Florida. The separation angle between the two spacecraft increases as time progresses. This double observation allows us to view solar activity from two different vantage points. On June 1st 2008, this angle reached <math>53^{\circ}</math> (Fig 1). On this day, a coronal mass ejection (CME) was captured by the STEREO A coronagraphs (Fig2).