McA Science

The unique power of the McIntosh archive is its capability for simultaneously representing closed and open magnetic structures over a long time period (Figures 1 & 2). Closed-field regions include sunspots, plage, and, if magnetic shear/twist is concentrated at the polarity inversion line (PIL), filaments. Of particular note on a global scale are polar crown filaments, which at times extend nearly 360 degrees around the sun at high latitudes. Open-field regions manifest as unipolar coronal holes, which, depending on solar-cycle phase, may appear predominantly at the poles or as isolated structures at lower latitudes.

A sequence of equatorial slices from the maps image
Figure 1: A sequence of equatorial slices from the maps (-20° to +20° latitude) is stacked along a curving axis advancing in time from top to bottom through  CROTs 1910 – 2084 (including all of SC 23); width is longitude. Colors are as in Fig. 2 (bottom). In general there is a long-lived pattern where coronal holes (red/blue) appear, disappear, and reappear in a preferred (differentially-rotating) set of longitudes. The persistence of low-latitude coronal holes coupled with solar rotation drives periodic behavior, both in the solar wind and in the Earth's space environment and upper atmosphere.

The completion of the full McA digitization will provide the community with a comprehensive resource for addressing key questions including: How do active longitudes vary within and between solar cycles, for both closed and open magnetic features? Where are closed and open magnetic features rooted (as evidenced by rotation rate), and how does this depend on solar cycle phase, feature lifetime, and latitude? How does the evolution of open and closed magnetic features relate to surface flows on solar-cycle time scales? Answering any or all of these questions has important implications for our understanding of the solar dynamo, and for our interpretation of periodic variations of Earth's space environment and upper atmosphere.

Solar Cycle 23 (1995-2009) patterns image
Figure 2: Solar Cycle 23 (1995-2009) patterns of open vs. closed magnetic features (Carrington Rotations CR1910 - CR2086 are plotted). The classic “butterfly” diagram of sunspots (orange) is shown, where sunspots are plotted vs. solar latitude for each solar rotation. The location of the polar crown filament (green) shows the so-called “rush to the poles” just prior to the reversal of the polar magnetic fields. This reversal is seen in the pattern of coronal hole boundaries (red=negative, blue=positive; furthest north per rotation=circles, furthest south=diamonds), which represent both polar and low-latitude coronal holes.