Markus,
I thought that your papers on the early STEREO data indicated that background subtraction was reasonably well understood. You obtained similar intensities from the two different vantage points.
Also, you've stressed the importance of computing the cross-correlation of the emission at different temperatures. Considering only highly correlated data removes many spurious broad DEM results.
I think that the most significant problem is our bias toward bright loops that we can measure easily. They might not be representative.
Finally, a quick comment on the paper. I was expecting to see some Monte Carlo simulations and least-square fits to the resulting data. Isn't the real question how many lines and what level of uncertainty do we need to determine the emission measure.
Best wishes,
Harry
On 9/23/10 10:20 AM, "Markus J. Aschwanden" aschwanden@lmsal.com wrote:
Friends,
I'm glad to see that the EM loci method is put on a more quantitative basis, especially in relationship to Gaussian DEM functions with variable temperature spread. While the two methods can now being used interchangably thanks to this recent nice study of Landi and Klimchuk, the biggest diagnostic problem for coronal loops is (in my view) still the proper background subtraction. Every contaminations from background fluxes introduces always a bias towards broader multi-thermal DEMs. This problem is even worse for AIA data, because more filters involve more confusion.
Looking forward to a patented background subtraction technique.
Cheers, Markus