Bipolar active regions in both hemispheres tend to be tilted with respect to the East -West equator of the Sun in accordance with Joy's law that describes the average tilt angle as a function of latitude. Mt. Wilson observatory data from 1917 -1985 are used to analyze the active-region tilt angle as a function of solar cycle, hemisphere, and longitude, in addition to the more common dependence on latitude. Our main results are as follows: i) We recommend a revision of Joy's law toward a weaker dependence on latitude (slope of 0.13 -0.26) and without forcing the tilt to zero at the Equator. ii) We determine that the hemispheric mean tilt value of active regions varies with each solar cycle, although the noise from a stochastic process dominates and does not allow for a determination of the slope of Joy's law on an 11-year time-scale. iii) The hemispheric difference in mean tilt angles, 1.1° + 0.27, over Cycles 16 to 21 was significant to a three-σ level, with average tilt angles in the northern and southern hemispheres of 4.7° + 0.26 and 3.6° + 0.27 respectively. iv) Area-weighted mean tilt angles normalized by latitude for Cycles 15 to 21 anti-correlate with cycle strength for the southern hemisphere and whole-Sun data, confirming previous results by Dasi-Espuig, Solanki, Krivova, et al. (2010, Astron. Astrophys. 518, A7). The northern hemispheric mean tilt angles do not show a dependence on cycle strength. vi) Mean tilt angles do not show a dependence on longitude for any hemisphere or cycle. In addition, the standard deviation of the mean tilt is 29 -31° for all cycles and hemispheres indicating that the scatter is due to the same consistent process even if the mean tilt angles vary.

Sunspot groups and bipolar magnetic regions (BMRs) serve as an observational diagnostic of the solar cycle. We use Debrecen Photohelographic Data (DPD) from 1974-2014 that determined sunspot tilt angles from daily white light observations, and data provided by Li & Ulrich (2012) that determined sunspot magnetic tilt angle using Mount Wilson magnetograms from 1974-2012. The magnetograms allowed for BMR tilt angles that were anti-Hale in configuration, so tilt values ranged from 0 to 360 • rather than the more common ±90 • . We explore the visual representation of magnetic tilt angles on a traditional butterfly diagram by plotting the mean area-weighted latitude of umbral activity in each bipolar sunspot group, including tilt information. The large scatter of tilt angles over the course of a single cycle and hemisphere prevents Joy's law from being visually identified in the tilt-butterfly diagram without further binning. The average latitude of anti-Hale regions does not differ from the average latitude of all regions in both hemispheres. The distribution of anti-Hale sunspot tilt angles are broadly distributed between 0 and 360°with a weak preference

We investigate bipolar sunspot regions and how tilt angle and footpoint separation vary during emergence and decay. The Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory collects data at a higher cadence than historical records and allows for a detailed analysis of regions over their lifetimes. We sample the umbral tilt angle, footpoint separation, and umbral area of 235 bipolar sunspot regions in Helioseismic and Magnetic Imager -Debrecen Data (HMIDD) with an hourly cadence. We use the time when the umbral area peaks as time zero to distinguish between the emergence and decay periods of each region and we limit our analysis of tilt and separation behavior over time to within ±96 hours of time zero. Tilt angle evolution is distinctly different for regions with small (≈ 30 MSH), midsize (≈ 50 MSH), and large (≈ 110 MSH) maximum umbral areas, with 45 and 90 MSH being useful divisions in separating the groups. At the peak umbral area, we determine median tilt angles for small (7.6 • ), midsize (5.9 • ) and large (9.3 • ) regions. Within ±48 hours of the time of peak umbral area, large regions steadily increase in tilt angle, midsize regions are nearly constant, and small regions show evidence of negative tilt during emergence. A period of growth in footpoint separation occurs over a 72-hr period for al of thel regions from roughly 40 to 70 Mm. The smallest bipoles (< 9 MSH) are outliers in that they do not obey Joy's law and have a much smaller footpoint separation. We confirm Muñoz-Jaramillo et al. (2015) results that the sunspots appear to be two distinct populations.

No abstract

This was an exploratory effort, rather than a comprehensive research endeavor. We relied on unclassified and publicly available materials to find examples of capabilities that challenge the government-only paradigm. We identified ways these capabilities and trends may impact the U.S. government in terms of emerging threats, policy implications, technology repercussions, human capital considerations, and financial effects. Finally, we identified areas for future study for U.S. and allied government leaders to respond to these changes.During our market scan, we found examples of SIGINT capabilities outside of government that are available to anyone. The capabilities we found have applications in maritime domain awareness; radio frequency (RF) spectrum mapping; eavesdropping, jamming, and hijacking of satellite communications; and cyber surveillance. Most of these capabilities are commercially available, many are free, and some are illegal. In our view, the existence of both legal and illegal markets and capabilities results in an environment where SIGINT has been democratized, or available to anyone.The capabilities we found have implications for the U.S. government and allies. They increase the threat environment by