SPRG Seminars
October 21, 2008:
"Estimating Electric Fields from Vector Magnetogram Sequences"
George H. Fisher, SSL
The advent of extensive ground-based and space-based vector magnetogram data will greatly improve our quantitative understanding of how magnetic fields evolve in the solar atmosphere. A problem of great interest is the derivation of electric fields from vector magnetogram data, as this is the crucial link between observation and future physics-based time-dependent models of the solar atmosphere. Most previous techniques for deriving E have used only the normal component of the magnetic induction equation, as it is generally believed that depth derivatives contained in the magnetic induction equation cannot be derived from vector measurements taken within a single layer. I will show that in fact, sufficient information exists within a sequence of vector magnetograms to determine a 3-dimensional electric field whose curl reproduces the observed changes in all 3 components of B. While this is certainly a major step forward, it is still true that the electric field E itself, as opposed to its curl, is under-constrained by the data. I will discuss how additional considerations may be used to uniquely determine all 3 components of the electric field.