Joint Cluster and XMM-Newton observations
The location of ESA's Cluster and XMM-Newton missions during a solar wind charge exchange emission event on 4 May 2003. The grey scale represents the density of plasma in Earth's magnetic environment at 15:30 UT, based on the Open Geospace Global Circulation Model simulation.
Earth is located within the white, low plasma-density region on the left side of both frames, which is separated from the solar wind (light grey, on the right of the frames) by the magnetosheath (dark grey and black).
When highly charged particles from the solar wind collide with hydrogen atoms, X-rays are emitted – a process known as solar wind charge exchange. When the hydrogen density and solar wind flux are higher than average, such as in the magnetosheath, the result is a stronger emission of soft X-rays.
The blue line indicates the orbit of the Cluster spacecraft between 11:00–16:00 UT; the green solid and dashed lines indicate the orbit of XMM-Newton and its line-of-sight direction, respectively, between 14:33–17:36 UT.
By combining data from both XMM-Newton and Cluster, scientists have been studying Earth's magnetosphere to pave the way for the upcoming Solar wind-Magnetosphere-Ionosphere Link Explorer, or SMILE, a joint European-Chinese mission due to launch in 2023.
The soft X-ray imager on SMILE will detect and image low energy X-rays in the outer regions of Earth's magnetosphere, measuring the motion of boundaries – the magnetopause and bow shock – moving in and out in response to solar wind variations.