Diagnostics of the non-Maxwellian kappa-distributions and electron density from coordinated EUV/UV/visible observations
We propose this HOP to acquire unique joint observations to probe the diagnostics for the non-Maxwellian distributions from Hinode/EIS, COMP, and IRIS. The target will be a limb active region and this will be a Target-of-Opportunity (ToO) HOP.
The assumption of a Maxwellian distribution is common in the analysis of solar spectra. However, this assumption may be incorrect if the emitting plasma is heated dynamically e.g. by nanoflares. A possible signature of such dynamic heating in the solar corona would be the presence of non-Maxwellian distributions. The kappa-distributions, characterized by a high-energy tail, have been diagnosed in a transient coronal loop observations made by EIS in Fe XI々II (Dudik et al. 2015, ApJ, 807, 123) and are also commonly observed in the solar wind (e.g. Maksimovic et al. 1997, Zouganelis 2008). Such distributions should
result in an increase in the intensity of the coronal forbidden lines compared to the EUV ones (Dudik et al. 2014, A&A, 570, A124), an effect detectable by coordinated EIS, IRIS, and COMP ground-based coronagraphic observations.
This is the focus of this proposal. In order to disentangle the effect of kappa-distributions from the effects of the electron density and differential emission measure (DEM), observations of additional EUV lines are needed for density and DEM diagnostics. These additional lines can also be used for diagnostics of κ from EIS lines alone. The Fe XIII lines at 10747 and 10798 A observed by COMP can also be used for independent diagnostics of electron density that can be compared with the densities from EIS Fe XIII lines.
The observations should be run during February, May-June, or August- September, when there is more than average probability (the average being 68%) of good weather conditions at the Mauna Loa Solar Observatory. This is a much higher chance than for the COMP-S instrument at Lomnicky Peak Observatory (1 in 7) involved in the previous HOP 265 observations. For this HOP, use the CompS_NonMax sequences developed previously.
The proposers will examine data from SDO and STEREO-A to determine, ahead of an observing plan, whether the observations should go ahead, and at which position angle on the limb. Given this point in the solar cycle, however, we expect that there will be a limb active region for much of the period.