DEFINING THE %26quot;BLIND SPOT%26quot; OF HINODE EIS AND XRT TEMPERATURE MEASUREMENTS

作者：Winebarger Amy R^*; Warren Harry P; Schmelz Joan T; Cirtain Jonathan; Mulu Moore Fana; Golub Leon; Kobayashi Ken

来源：Astrophysical Journal Letters, 2012, 746(2): L17.

DOI：10.1088/2041-8205/746/2/L17

• Sun: corona

Observing high-temperature, low emission measure plasma is key to unlocking the coronal heating problem. With current instrumentation, a combination of EUV spectral data from Hinode Extreme-ultraviolet Imaging Spectrometer (EIS; sensitive to temperatures up to 4 MK) and broadband filter data from Hinode X-ray Telescope (XRT; sensitive to higher temperatures) is typically used to diagnose the temperature structure of the observed plasma. In this Letter, we demonstrate that a %26quot;blind spot%26quot; exists in temperature-emission measure space for combined Hinode EIS and XRT observations. For a typical active region core with significant emission at 3-4 MK, Hinode EIS and XRT are insensitive to plasma with temperatures greater than similar to 6 MK and emission measures less than similar to 10(27) cm(-5). We then demonstrate that the temperature and emission measure limits of this blind spot depend upon the temperature distribution of the plasma along the line of sight by considering a hypothetical emission measure distribution sharply peaked at 1 MK. For this emission measure distribution, we find that EIS and XRT are insensitive to plasma with emission measures less than similar to 10(26) cm(-5). We suggest that a spatially and spectrally resolved 6-24 angstrom spectrum would improve the sensitivity to these high-temperature, low emission measure plasma.

• 出版日期2012-2-20