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

Abstract

A component of the magnetic field measured in situ near the Earth in the solar wind is present from north-south fields from the low solar corona. Using the Current-sheet Source Surface model, these fields can be extrapolated upward from near the solar surface to 1 AU. Global velocities inferred from a combination of interplanetary scintillation observations matched to in situ velocities and densities provide the extrapolation to 1 AU assuming mass and mass flux conservation. The north-south field component is compared with the same ACE in situ magnetic field component-the Normal (Radial Tangential Normal) Bn coordinate-for three years throughout the solar minimum of the current solar cycle. We find a significant positive correlation throughout this period between this method of determining the Bn field compared with in situ measurements. Given this result from a study during the latest solar minimum, this indicates that a small fraction of the low-coronal Bn component flux regularly escapes from closed field regions. The prospects for Space Weather, where the knowledge of a Bz field at Earth is important for its geomagnetic field effects, is also now enhanced. This is because the Bn field provides the major portion of the Geocentric Solar Magnetospheric Bz field coordinate that couples most closely to the Earth's geomagnetic field.

A Daily Determination of BZ Using the Russell‐McPherron Effect to Forecast Geomagnetic Activity

“…A high velocity forecast just prior to the B z decrease can also be observed to shorten the arrival time of the decrease in the last day or two of the forecast. Future efforts in this work to provide better arrival times and nonradial transport of the fields causing these effects are currently one of the main efforts pursued by the UCSD IPS analysis effort (Jackson et al, , ). We leave for the future effort a forecast of geomagnetic minor and moderate storm activity using the UCSD predicted parameter values in addition to the B z decrease to better quantify the effect of geomagnetic storm activity.…”

The utility of polarized heliospheric imaging for space weather monitoring

“…In principle, this could yield a new way to infer the sign of the north/south component of the magnetic field ( B z ) in the leading portion of the CME. This B z property is notoriously hard to predict because of the dual problems of determining B z at the solar surface and understanding the effect of potential writhe as the CME departs from the Sun and propagates, despite recent promising work in this direction [ Jackson et al , ]. Additional complications arise because CMEs are optically thin, are extended 3‐D structures, and change in kinematics and geometry in an asymmetric fashion.…”

Single‐Site IPS Power Spectra Analysis for Space Weather Products Using Cross‐Correlation Function Results From EISCAT and MERLIN IPS Data

“…Crucially, for space weather applications, use of IPS has been shown capable of detecting stream interaction regions (SIRs) and CMEs, including those Earth‐directed throughout the inner heliosphere (e.g., Bisi et al, , ; Breen et al, ; Jackson et al, ; , ; Jones et al, ; Manoharan et al, , and references therein), making it a technique with a proven potential for the prediction and to the study of Earth‐directed events. In this work, the SSA was applied to structures that included CME and SIR, where the velocity values can be higher than ambient solar wind.…”