A large helmet streamer is usually observed after the eruption of a filament or CME, and this probably shows the side view of a giant arcade. An example of this is presented in Figure 7 (Hiei et al., 1993). It is interesting to note that the temperature is higher near the edge of the cusp-shaped loop of giant arcades, which is similar to LDE flares. Note also that the soft X-ray intensity in a giant arcade is usually very low, and this is why giant arcades had belonged to a different category than flares. However, Yohkoh/SXT has revealed that giant arcades have a lot of similarities to LDE flares except for their spatial scale and magnetic field strength. These two factors actually affect the time scale, amount of released energy, and emission measure of individual events.
Outside the cusp-shaped structure the soft X-ray intensity often decreases with time, which is called dimming (Tsuneta, 1996; Sterling and Hudson, 1997; Harra and Sterling, 2001). Tsuneta (1996) attributed dimming to the inflow driven by reconnection that carries a large amount of plasma surrounding a current sheet into the sheet, thereby decreasing the gas density outside the current sheet (see also Shiota et al., 2005). Although usual dimmings associated with CMEs are attributed to stretching /opening of field lines by eruption (e.g., Sterling and Hudson, 1997; Harra and Sterling, 2001), there is a possibility that some of them are caused by the evacuation via the inflow into reconnection region like above (e.g., Shiota et al., 2005).
Living Rev. Solar Phys. 8, (2011), 6
This work is licensed under a Creative Commons License.