Prediction of the Interplanetary Magnetic Field Vector Bz at L1

Team Chair: Angelos Vourlidas
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Target Description: There has been significant progress in recent years in our ability to observe Coronal Mass Ejections (CMEs) from space. However, the net effect of CMEs on the geomagnetic field is a function of both CME speed and the embedded Interplanetary Magnetic Field (IMF) vector Bz. It would be valuable to the operations community if highly reliable forecasts were available of the vector Bz prior to the passage of the CME at L1.Reliable forecasts of the Bx and By components are also desirable, but of secondary importance. A time series prediction of Bz is fundamentally important in the provision of space weather forecasts because:
• It allows for a prediction of the intensity of the ensuing geomagnetic storm
• It affords a much better-than-climatological prediction of the duration of the storm
• It would minimize false alarms
Given that Solar-B, STEREO, and SDO will be delivering revolutionary new observations of the photospheric magnetic and velocity fields and of the coronal structures that give rise to CMEs, it is now timely to mount a coordinated attack on the problem of identifying the characteristics of the magnetic field embedded in the CME. It is only when Bz can be well predicted that significant advances in space weather services can occur.

Goals and measures of success: The goal of this Focused Science Topic is to quantify accurately the polarity and magnitude of the IMF Bz for the next 12-24 hours. The prime measure of success for this work would be a good agreement in the time series of predicted and observed BZ values at L1. An added bonus would be the ability to predict all three components of magnetic field, especially if either Bx or By are significantly larger than Bz.

Types of solicited investigations: It is expected that the focus team will include, but certainly not be limited to, the following types of investigations:
• observational and theoretical/modeling investigations relating to identification of characteristics of Bz (Bx, By) that relate to real-time photospheric magnetograms,
and perhaps sub-surface flows from ground and space-based observations.
• observational and theoretical/modeling investigations relating to identification of characteristics of the inner heliosphere that affect the magnetic field topology – specifically, Bz (Bx, By) at L1
• observational and theoretical/modeling investigations of CMEs to include the embedded magnetic field vector Bz (Bx, By)