Main Objective: The goals of this HOP is to characterize the X-ray emission from the Sun during solar minimum
Scientific Justification: The Sun currently is entering its minimum period of activity, and we expect the absolute minimum to occur in about 2019. The key to this program is to obtain frequent glimpses of the global X-ray corona, via fulldisk images with XRT and one-orbit mosaic maps of the Sun with NuSTAR at times of no (or minimal) solar ghost-ray background. During solar minimum, the shear zones of the solar torsional oscillations, which relate globally to magnetic flux emergence, will jump from low latitudes to high latitudes according to the well-established Babcock-Leighton pattern. The NuSTAR observations can relate this to global coronal temperaturevariations at for the first time. XRT will provide important context for these observations. In addition to thermal emission processes we also note the possibility of non-thermal signatures associated with coronal heating (e.g., nanoflares) or with cosmic-ray secondary products. |
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