Recovering Solar Toroidal Field Dynamics From Sunspot Location Patterns

We analyze both Kitt Peak magnetogram data and MDI continuum intensity sunspot data to search for the following solar toroidal band properties: width in latitude and the existence of a tipping instability (longitudinal m=1 mode) for any time during the solar cycle. To determine the extent which we can recover the toroidal field dynamics, we forward model artificially generated sunspot distributions from subsurface toroidal fields we assigned certain properties. We analyzed two sunspot distribution parameters using MDI and model data: the average latitudinal separation of sunspot pairs as a function of longitudinal separation, and the number of sunspot pairs creating a given angle with respect to the E-W direction. A toroidal band of 10 degrees width with a constant tipping of 5 degrees best fits MDI data early in the solar cycle. A toroidal band of 20 degrees width with a tipping amplitude decreasing in time from 5 to 0 degrees best fits MDI data late in the solar cycle. Model data generated by untipped toroidal bands cannot fit MDI high latitude data and can fit only one parameter at low latitudes. Tipped toroidal bands satisfy chi squared criteria at both high and low latitudes. We conclude this is evidence to reject the null hypothesis - that toroidal bands in the solar tachocline do not experience a tipping instability - in favor of the hypothesis that the toroidal band experiences an m=1 tipping instability. Our finding that the band widens from ~10 degrees early in the solar cycle to ~20 degrees late in the solar cycle may be explained in theory by magnetic drag spreading the toroidal band due to altered flow along the tipped field lines.Comment: This paper is accepted to Astrophysical Journal, September 2005 issu

Cement Based Batteries and their Potential for Use in Low Power Operations

This paper presents the development of an innovative cement-electrolyte battery for low power operations such as cathodic protection of reinforced concrete. A battery design was refined by altering different constituents and examining the open circuit voltage, resistor loaded current and lifespan. The final design consisted of a copper plate cathode, aluminium plate anode, and a cement electrolyte which included additives of carbon black, plasticiser, Alum salt and Epsom salt. A relationship between age, temperature and hydration of the cell and the current it produced was determined. It was found that sealing the battery using varnish increased the moisture retention and current output. Current was also found to increase with internal temperature of the electrolyte and connecting two cells in parallel further doubled or even tripled the current. Parallel-connected cells could sustain an average current of 0.35mA through a 10Ω resistor over two weeks of recording. The preliminary findings demonstrate that cement-based batteries can produce sufficient sustainable electrical outputs with the correct materials and arrangement of components. Work is ongoing to determine how these batteries can be recharged using photovoltaics which will further enhance their sustainability properties

First Steps in Developing Cement-Based Batteries to Power Cathodic Protection of Embedded Steel in Concrete

This paper presents the first steps in developing innovative cement-based batteries to power cathodic protection in reinforced concrete structures. Initial electrical outputs of 1.55V and 23mA have been found to be sufficient to polarise prescribed corrosion currents of 20mA per m2 of embedded steel. Cathodic protection is a well-developed and powerful technique to limit the effects of steel reinforcement corrosion. However, as it requires an electrical supply day and night, it is often powered by non-environmentally friendly diesel generators or connected to the electrical grid. This paper focuses on increasing the ionic conductivity of the solution in the cement pores, increasing the porosity of the cement, examining ways of sealing moisture into the cement and comparing different electrode materials and treatments. The batteries presented consist of different combinations of Portland cement, water, carbon black and salt solutions with embedded copper acting as the cathode and magnesium, aluminium or zinc cast as the anode. The preliminary findings demonstrate that cementbased batteries can produce sufficient sustainable electrical outputs with the correct materials and arrangement of cast-in anodes. Work is ongoing to determine how these batteries can be recharged using photovoltaics which will further enhance their sustainability properties

Cathodic Protection for Reinforced Concrete Structures: Present Practice and Moves Toward using Renewable Energy

Abstract: Cathodic protection (CP) limits the corrosion of a metal by making it the cathode of an electrochemical cell. This is achieved either by (i) using more active sacrificial anodes to create a driving current, or (ii) using inert anodes and impressing an external direct current (DC). This paper presents up-to-date CP systems available for reinforced concrete, particularly Impressed Current Cathodic Protection (ICCP) and self-sufficient or renewable energy systems. The potential for overcoming the mismatch in energy provision from renewable sources (intermittent current) with energy needs for CP (constant current) is discussed by exploring novel designs and examining current requirments

How much more can sunspots tell us about the solar dynamo?

Sunspot observations inspired solar dynamo theory and continue to do so. Simply counting them established the sunspot cycle and its period. Latitudinal distributions introduced the tough constraint that the source of sunspots moves equator-ward as the cycle progresses. Observations of Hale's polarity law mandated hemispheric asymmetry. How much more can sunspots tell us about the solar dynamo? We draw attention to a few outstanding questions raised by inherent sunspot properties. Namely, how to explain sunspot rotation rates, the incoherence of follower spots, the longitudinal spacing of sunspot groups, and brightness trends within a given sunspot cycle. After reviewing the first several topics, we then present new results on the brightness of sunspots in Cycle 24 as observed with the Helioseismic Magnetic Imager (HMI). We compare these results to the sunspot brightness observed in Cycle 23 with the Michelson Doppler Imager (MDI). Next, we compare the minimum intensities of five sunspots simultaneously observed by the Hinode Solar Optical Telescope Spectropolarimeter (SOT-SP) and HMI to verify that the minimum brightness of sunspot umbrae correlates well to the maximum field strength. We then examine 90 and 52 sunspots in the north and south hemisphere, respectively, from 2010 - 2012. Finally, we conclude that the average maximum field strengths of umbra 40 Carrington Rotations into Cycle 24 are 2690 Gauss, virtually indistinguishable from the 2660 Gauss value observed at a similar time in Cycle 23 with MDI

The Dependence of Joy's Law as a Function of Flux Emergence Phase

Data from the Michelson Doppler Imager (MDI) and Helioseismic and Magnetic Imager (HMI) are analyzed from 1996 to 2023 to investigate tilt angles ($\gamma$) of bipolar magnetic regions and Joy's Law for Cycles 23, 24, and a portion of 25. The HMI radial magnetic field ($B_{r}$) and MDI magnetogram ($B_{los}$) data are used to calculate ($\gamma$) using the flux-weighted centroids of the positive and negative polarities. Each AR is only sampled once. The analysis includes only Beta ($\beta$)-class active regions since computing $\gamma$ of complex active regions is less meaningful. During the emergence of the ARs, we find that the average tilt angle ($\bar{\gamma}$) increases from 3.30$^{\circ}\pm$0.75 when 20\% of the flux has emerged to 6.79$^{\circ}\pm$0.66 when the ARs are at their maximum flux. Cycle 24 had a larger average tilt $\bar{\gamma}_{24}$=6.67$\pm$0.66 than Cycle 23, $\bar{\gamma}_{23}$=5.11$\pm$0.61. There are persistent differences in $\bar{\gamma}$ in the hemispheres with the southern hemisphere having higher ${\bar{\gamma}}$ in Cycles 23 and 24 but the errors are such that these differences are not statistically significant.Comment: 11 pages, 8 figures, 3 table