Inclusion of Real-Time In-Situ Measurements into the UCSD Time-Dependent Tomography and Its Use as a Forecast Algorithm

Abstract

The University of California, San Diego (UCSD) three-dimensional (3D) timedependent tomography program, used for over a decade to reconstruct and forecast coronal mass ejections (CMEs), does so from observations of interplanetary scintillation (IPS) taken using the Solar-Terrestrial Environment Laboratory (STELab) radio arrays in Japan. An earlier article (Jackson et al. in Solar Phys. 265, 245, 2010) tion can be used in addition to remote-sensing data to constrain a time-dependent tomographic velocity solution. Here we extend this in-situ inclusion to density measurements, and show how this constrains the tomographic density solution. Supplementing remote-sensing observations with in-situ measurements provides additional information to construct an iterated solar-wind parameter that is propagated outward from near the solar surface past the measurement location, and throughout the volume. As in the case of velocity when this is done, the largest changes within the volume are close to the radial directions around Earth that incorporate the in-situ measurements; the inclusion significantly reduces the uncertainty in extending these measurements to global 3D reconstructions that are distant in time and space from the spacecraft. At Earth, this analysis provides a finely tuned real-time result up to the latest time for which in-situ measurements are available, and enables more-accurate extension of these results near Earth to those remotely sensed. We show examples of this new algorithm using real-time STELab IPS data that were used in our forecasts throughout Carrington rotations 2010 through 2016, and we provide one metric prescription that we have used to determine the forecasting accuracy one, two, and three days in advance of the time data become available to analyze from STELab. We show that the accuracy is considerably better than assuming persistence of the same signal over one to two days in advance of when the data are available.

Exploration of solar photospheric magnetic field data sets using the UCSD tomography

“…IPS data used in the present paper are from the Solar Terrestrial Environment Laboratory (STELab), now called the Institute for Space‐Earth Environmental Research (ISEE), Japan [ Kojima and Kakinuma , ]. To further refine these results, the analyses are fit to near‐Earth in situ measurements of plasma velocities and densities [ Jackson et al ., , ]. Global heliospheric results are calculated for Carrington rotation time intervals (27 days).…”

A Determination of the North–south Heliospheric Magnetic Field Component From Inner Corona Closed-Loop Propagation

“…Best fit is achieved iteratively: when the modeled 3D solar wind at a large solar distance does not match the overall observations, the source surface values are altered to minimize the deviations. These global heliospheric analyses also iteratively match hour-averaged in situ data at Earth to provide a normalization of the two parameters that are mapped globally in the solar wind (Jackson et al 2010(Jackson et al , 2013. Figure 2 is an example of the Carrington-rotation interval 2056 (CR2056) velocity at Earth from our 3D reconstruction analysis using STELab IPS data from 2007 April and May.…”

“…These observations measure small-scale (∼150 km) heliospheric density variations along each line of sight (LOS). Analyses of data from IPS have long been used to study the heliosphere (e.g., Houminer 1971;Hewish & Bravo 1986;Behannon et al 1991;Jackson et al 1998Jackson et al , 2011Jackson et al , 2013Breen et al 2008;Tokumaru 2013). The IPS normalized scintillation level (g-level) data serve as a proxy for density, and provide a determination of large-scale heliospheric density structures.…”

“…Velocity analyses using STELab data are a primary source of information about the largescale velocities in the inner heliosphere (e.g., Tokumaru 2013). Since 1999, these data have been used to determine heliospheric structure variation on a day-by-day basis in near real time using the UCSD 3D tomography (e.g., Jackson et al 2003Jackson et al , 2013 and references therein).…”

The utility of polarized heliospheric imaging for space weather monitoring

“…Tracking and visually identifying coronal mass ejections (CMEs) and corotating interaction regions (CIRs) are critical to predicting impact probability, arrival time, and expected ram pressure—three key aspects of successful geomagnetic storm prediction. Current CME prediction techniques used by the U.S. government rely primarily on coronagraphs (e.g., SOHO /Large Angle and Spectrometric Coronagraph (LASCO), STEREO/Coronagraph (COR) ) and modeling [e.g., Odstrcil and Pizzo , ; Lee et al , ] to identify CMEs and estimate the parameters describing their arrival at the Earth [e.g., Odstrcil et al , ; Taktakishvili et al , ], although other techniques are used scientifically, e.g., interplanetary scintillation [e.g., Tokumaru , ; Jackson et al , ]. Similarly, prediction of CIR arrival at Earth currently relies almost exclusively on solar wind modeling from magnetic structures measured on the surface of the Sun (e.g.…”