Predicting the Sun's Polar Magnetic Fields with a Surface Flux Transport Model

The Sun's polar magnetic fields are directly related to solar cycle variability. The strength of the polar fields at the start (minimum) of a cycle determine the subsequent amplitude of that cycle. In addition, the polar field reversals at cycle maximum alter the propagation of galactic cosmic rays throughout the heliosphere in fundamental ways. We describe a surface magnetic flux transport model that advects the magnetic flux emerging in active regions (sunspots) using detailed observations of the near-surface flows that transport the magnetic elements. These flows include the axisymmetric differential rotation and meridional flow and the non-axisymmetric cellular convective flows (supergranules) all of which vary in time in the model as indicated by direct observations. We use this model with data assimilated from full-disk magnetograms to produce full surface maps of the Sun's magnetic field at 15-minute intervals from 1996 May to 2013 July (all of sunspot cycle 23 and the rise to maximum of cycle 24). We tested the predictability of this model using these maps as initial conditions, but with daily sunspot area data used to give the sources of new magnetic flux. We find that the strength of the polar fields at cycle minimum and the polar field reversals at cycle maximum can be reliably predicted up to three years in advance. We include a prediction for the cycle 24 polar field reversal.Comment: 12 pages, 9 figures, ApJ accepte

Early Learning Innovation Fund Evaluation Final Report

This is a formative evaluation of the Hewlett Foundation's Early Learning Innovation Fund that began in 2011 as part of the Quality Education in Developing Countries (QEDC) initiative.  The Fund has four overarching objectives, which are to: promote promising approaches to improve children's learning; strengthen the capacity of organizations implementing those approaches; strengthen those organizations' networks and ownership; and grow 20 percent of implementing organizations into significant players in the education sector. The Fund's original design was to create a "pipeline" of innovative approaches to improve learning outcomes, with the assumption that donors and partners would adopt the most successful ones. A defining feature of the Fund was that it delivered assistance through two intermediary support organizations (ISOs), rather than providing funds directly to implementing organizations. Through an open solicitation process, the Hewlett Foundation selected Firelight Foundation and TrustAfrica to manage the Fund. Firelight Foundation, based in California, was founded in 1999 with a mission to channel resources to community-based organizations (CBOs) working to improve the lives of vulnerable children and families in Africa. It supports 12 implementing organizations in Tanzania for the Fund. TrustAfrica, based in Dakar, Senegal, is a convener that seeks to strengthen African-led initiatives addressing some of the continent's most difficult challenges. The Fund was its first experience working specifically with early learning and childhood development organizations. Under the Fund, it supported 16 such organizations: one in Mali and five each in Senegal, Uganda and Kenya. At the end of 2014, the Hewlett Foundation commissioned Management Systems International (MSI) to conduct a mid-term evaluation assessing the implementation of the Fund exploring the extent to which it achieved intended outcomes and any factors that had limited or enabled its achievements. It analyzed the support that the ISOs provided to their implementing organizations, with specific focus on monitoring and evaluation (M&E). The evaluation included an audit of the implementing organizations' M&E systems and a review of the feasibility of compiling data collected to support an impact evaluation. Finally, the Foundation and the ISOs hoped that this evaluation would reveal the most promising innovations and inform planning for Phase II of the Fund. The evaluation findings sought to inform the Hewlett Foundation and other donors interested in supporting intermediary grant-makers, early learning innovations and the expansion of innovations. TrustAfrica and Firelight Foundation provided input to the evaluation's scope of work. Mid-term evaluation reports for each ISO provided findings about their management of the Fund's Phase I and recommendations for Phase II. This final evaluation report will inform donors, ISOs and other implementing organizations about the best approaches to support promising early learning innovations and their expansion. The full report outlines findings common across both ISOs' experience and includes recommendations in four key areas: adequate time; appropriate capacity building; advocacy and scaling up; and evaluating and documenting innovations. Overall, both Firelight Foundation and TrustAfrica supported a number of effective innovations working through committed and largely competent implementing organizations. The program's open-ended nature avoided being prescriptive in its approach, but based on the lessons learned in this evaluation and the broader literature, the Hewlett Foundation and other donors could have offered more guidance to ISOs to avoid the need to continually relearn some lessons. For example, over the evaluation period, it became increasingly evident that the current context demands more focused advance planning to measure impact on beneficiaries and other stakeholders and a more concrete approach to promoting and resourcing potential scale-up. The main findings from the evaluation and recommendations are summarized here

Measurements of the Sun's High Latitude Meridional Circulation

The meridional circulation at high latitudes is crucial to the build-up and reversal of the Sun's polar magnetic fields. Here we characterize the axisymmetric flows by applying a magnetic feature cross-correlation procedure to high resolution magnetograms obtained by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We focus on Carrington Rotations 2096-2107 (April 2010 to March 2011) - the overlap interval between HMI and the Michelson Doppler Investigation (MDI). HMI magnetograms averaged over 720 seconds are first mapped into heliographic coordinates. Strips from these maps are then cross-correlated to determine the distances in latitude and longitude that the magnetic element pattern has moved, thus providing meridional flow and differential rotation velocities for each rotation of the Sun. Flow velocities were averaged for the overlap interval and compared to results obtained from MDI data. This comparison indicates that these HMI images are rotated counter-clockwise by 0.075 degrees with respect to the Sun's rotation axis. The profiles indicate that HMI data can be used to reliably measure these axisymmetric flow velocities to at least within 5 degrees of the poles. Unlike the noisier MDI measurements, no evidence of a meridional flow counter-cell is seen in either hemisphere with the HMI measurements: poleward flow continues all the way to the poles. Slight North-South asymmetries are observed in the meridional flow. These asymmetries should contribute to the observed asymmetries in the polar fields and the timing of their reversals.Comment: 6 pages, 3 color figures, accepted for publication in The Astrophysical Journal Lette

Firelight Foundation: An interim evaluation report of the Early Learning Innovation Fund

The Hewlett Foundation in 2014 selected Management Systems International (MSI) to implement a midterm evaluation of the Early Learning Innovation Fund. This evaluation explores the concept and design of the Fund; progress in achieving the Hewlett Foundation's four intermediary outcomes; and Firelight's implementation of the innovation fund with a focus on its approach to capacity building and expanding innovative programs. This evaluation also reviews the quality of the sub-grantees' monitoring and evaluation (M&E) systems and explores the potential of conducting an impact evaluation of sub-grantee activities

Reproducing the Photospheric Magnetic Field Evolution During the Rise of Cycle 24 with Flux Transport by Supergranules

We simulate the transport of magnetic flux in the Sun s photosphere by an evolving pattern of cellular horizontal flows (supergranules). Characteristics of the simulated flow pattern match observed characteristics including the velocity power spectrum, cell lifetimes, and cell pattern motion in longitude and latitude. Simulations using an average, and north-south symmetric, meridional motion of the cellular pattern produce polar magnetic fields that are too weak in the North and too strong in the South. Simulations using cellular patterns with meridional motions that evolve with the observed changes in strength and north-south asymmetry will be analyzed to see if they reproduce the polar field evolution observed during the rise of Cycle 24

Photospheric Magnetic Flux Transport - Supergranules Rule

Observations of the transport of magnetic flux in the Sun's photosphere show that active region magnetic flux is carried far from its origin by a combination of flows. These flows have previously been identified and modeled as separate axisymmetric processes: differential rotation, meridional flow, and supergranule diffusion. Experiments with a surface convective flow model reveal that the true nature of this transport is advection by the non-axisymmetric cellular flows themselves - supergranules. Magnetic elements are transported to the boundaries of the cells and then follow the evolving boundaries. The convective flows in supergranules have peak velocities near 500 m/s. These flows completely overpower the superimposed 20 m/s meridional flow and 100 m/s differential rotation. The magnetic elements remain pinned at the supergranule boundaries. Experiments with and without the superimposed axisymmetric photospheric flows show that the axisymmetric transport of magnetic flux is controlled by the advection of the cellular pattern by underlying flows representative of deeper layers. The magnetic elements follow the differential rotation and meridional flow associated with the convection cells themselves -- supergranules rule