XRT Picture of the Week (XPOW)

XRT often participates in joint observation campaigns with other observatories which we refer to as Hinode Observation Programs (HOPs). One such HOP that ran in February was observing active region moss. On earth, moss typically grows in shady, moist areas but on the sun, moss exists in the region between the chromosphere and the corona called the transition region. Moss is best seen in AIA 171 images (bottom right), mostly grows around active regions, and is associated with active region plage. But not all plage have moss over it because another important ingredient to grow moss is hot coronal x-ray loops.

Moss is an interesting feature to study on the sun because it links cool chromospheric phenomena, H-alpha spicules, with hot coronal features, foot points of x-ray loops. Moss is difficult to understand because they need magnetic fields to grow but don't match up well with photospheric or chromospheric magnetic elements. Previous observations have shown that moss evolve on really small time-scales, less than 15 seconds.

To fully understand moss, we need simultaneous observations of the chromosphere, transition region, and corona. The Hinode, SDO/AIA, and IRIS observatories coordinated to observe some moss around AR12282. Shown above are just a few of the high resolution images that could help up understand the growth of active region moss. Hinode SOT (upper left) provided chromospheric and magnetic field observations. XRT (upper right) observed the hot coronal loops. IRIS (lower left) observed the chromosphere and transition region and SDO/AIA (lower right) observed the transition region. These observations will continue throughout the month.