The upper chart (sector structure) is based on ACE MAG real time data of recent 27 days. The chart is divided into 27 pieces surrounded by the ideal Archimedes spirals. 1-day averages of the Bx and By components in the GSE coordinate system are used to color the chart. Every day around 0UT we rotate the chart by 1/27*360 degrees and color one piece of the chart based on yesterday's ACE data. We tried other averages (for example 1-hour, 3-hour, and ...) to make this chart, but we found it was best to use 1-day averages to recognize sector boundaries.