Back to Volume
Paper: Quiet-Sun: A Comparison of MDI and SOT Fluxes
Volume: 397, First Results From Hinode
Page: 31
Authors: Parnell, C.E.; Deforest, C.E.; Hagenaar, H.J.; Lamb, D.A.; Welsch, B.T.
Abstract: The SOT-NFI on Hinode has both higher resolution and better sensitivity than MDI on SOHO. Line-of-sight magnetograms of the quiet Sun taken simultaneously by both MDI and SOT are investigated to show how the observed flux differs between the two instruments. We find that: (i) the total unsigned flux observed by SOT is approximately 50% greater than that observed by MDI and (ii) the total signed flux remains approximately constant. Thus, the extra flux observed by SOT is made up of equal amounts of positive and negative flux. By comparing the observed flux distributions from MDI and SOT we find that the extra flux is contained in features with fluxes less than the smallest observed by MDI. Indeed, the smallest features in SOT have just ≥ 1016 Mx, a factor of thirty less than the smallest observed by MDI.

The distributions of feature fluxes observed by the two instruments are also compared. We find that by using a ‘clumping’ algorithm, which counts a single ‘flux massif’ as one feature, the fluxes in MDI and SOT follow the same distribution - a power-law - between 2 × 1017 and 1020 Mx. Thus, the mechanism producing network and intranetwork features appears to be the same. Furthermore, the power-law index of this distribution is found to be −1.85. This value is neither the Kolomogrov −5/3 slope of hydrodynamic turbulence nor the Krichenen −2 slope of magneto-hydrodynamic turbulence, although both of these numbers may be within the error bars of our analysis.

Back to Volume