National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Using Far-Side Imaging to Provide Improved Magnetic Maps to Drive Atmospheric and Solar Wind Models

ROSES ID: NNH16ZDA001N      Selection Year: 2016      

Program Element: Focused Science Topic

Principal Investigator: Harry Warren

Affiliation(s): U.S. Naval Research Laboratory

Project Member(s):
Upton, Lisa A Co-I null
Ugarte-Urra, Ignacio Co-I Naval Research Laboratory
Wu, ChinChun Co-I Naval Research laboratory


The photospheric magnetic fields drive the solar atmosphere, the solar wind, and are responsible for the production of space weather events such as solar flares and coronal mass ejections. Currently one of the biggest limitations for determining the global state of the solar atmosphere and inner heliosphere is the absence of reliable magnetic data for the far-side of the Sun. While advances in far-side Helioseismology are able to provide a probability that a far-side Active Region (AR) may exist (with an estimate of the location and the amplitude), this does not include details about the structure of the AR (e.g., polarity separation). Furthermore, some ARs do not show up until they actually appear in the nearside observations. Our group has developed an innovative technique which utilizes far-side EUV data as a proxy for magnetic field strength (Ugarte-Urra et. al., 2015). We have found that this information can be incorporated into the Advective Flux Transport (AFT; Upton and Hathway 2014a,b) model to accurately reproduce the evolution of the total unsigned flux in an Active Region prior to being observed on the near-side of the Sun and continuing for multiple solar rotations.

Goals and Objectives:

-- Develop magnetic proxy maps of the far-side photospheric magnetic field.

-- Perform Data Assimilation of far-side proxy maps into AFT (AFT+304 maps).

-- Provide real-time AFT+304 maps and predictive AFT+304 maps.

-- Evaluate the errors and uncertainties associated with these maps and forecasts.

-- Compute potential field source-surface extrapolations from these maps

-- Compute proxies for solar activity based on these maps

-- Evaluate the impact of revised maps on the solar wind observed at Earth and with STEREO

-- Adapt our technique for Future Missions.


In the last few years, Surface Flux Transport (SFT) models have made considerable progress in reproducing the evolution of the photospheric magnetic field. By advecting the flows with an evolving convection pattern, described by Hathaway et al. (2010), the AFT model is able surpass the realism (including the production of a magnetic network) that can be obtained by traditional SFT models which use a diffusivity coefficient to account for the turbulent motions. We have found that even once data assimilation is halted, AFT can accurately reproduce the active region evolution of the total unsigned flux in an Active Region to within a factor of 2 for multiple solar rotations (Ugarte-Urra et. al., 2015). Furthermore, AFT can incorporate magnetic sources in two different ways: either by manually inserting bipolar ARs or by using data assimilation to directly incorporate magnetic data from magnetograms.

We will begin by using STEREO 304 images to develop proxy maps for ARs occurring on the far-side of the Sun. We will then use data assimilation to incorporate these proxy maps into AFT, producing full-Sun synchronic maps of the Sun's global photospheric magnetic field (AFT+304 maps). These AFT+304 maps are ideal for atmospheric and solar wind models which require a time-dependent sequence of boundary conditions. We will automate the process so that we can provide these maps in near real time. Additionally, we will allow AFT to run in its predictive mode to provide forecasts of the Sun's global magnetic field configuration. Finally, we will adapt our process for future missions, including Solar Orbiter.

Proposed Contributions to the Focus Team Effort:

By combining assimilation of nearside data with far side data from 304 measurements, AFT+304 will be able to provide the most complete picture of the magnetic field configuration of the entire Sun. This has significant implications for space weather predictions, such as solar irradiance, solar wind, and coronal field models. We propose to contribute both the far-side proxy maps and the AFT+304 maps to the team for use as magnetic source data to drive the solar atmosphere or solar wind models.
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