Field-Aligned Currents

Field-aligned, or Birkeland, currents

(FAC) constitute the major electrodynamic coupling between magnetospheres and ionospheres, and are associated with auroral activity. We are assembling a network program whereby near real-time measurements are incorporated into a model of the major FAC systems to display their probable geographic location. This estimation of field-aligned current regions roughly corresponds to the location of the auroral oval and is part of our Space Weather diagnostic effort (see bottom of page).

Severe magnetic storms can be very disruptive, and may be viewed as the space weather analog to thunderstorms. For example, a large storm in March of 1989 caused large scale power grid shutdowns in Canada. Communication links can be upset, both from satellite failures during storms and from disturbances in the ionosphere which affect radio and microwave transmissions. An important space weather site on the World Wide Web is:

NOAA's Space Environment Laboratory

SWAZI Reports:

We have developed a system of near real-time notification of auroral zone expansions using Freja "AC" magnetic field data. The SWAZI (Satellite Warning of Auroral Zone Increases) reports are automatically generated and distributed via email to various and sundry interested parties. Further information on SWAZI reports is available in the POSTER at the 1994 Fall AGU meeting . A subsequent showing at the 1995 Spring AGU meeting demonstrated the Web accessablility and real-time capabilities of the system

Our automatically generated SWAZI Reports and Associated FAC Images are available.

This system remained in reliable operation for approximately 6 months, after which time the Freja spacecraft suspended normal operating procedures. Having established the utility of this type of monitoring, we are eagerly anticipating further flight opportunities. Work is now in progress to develop miniaturized magnetometer packages with simple on-board processing to deliver real-time information on the boundary locations of the auroral oval.

In addition to providing real-time monitoring, we have found it very useful to employ our algorithm throughout the UARS and Freja magnetometer datasets. Further work on the relationships between the large-scale field-aligned currents, energetic particle precipitation, and magnetic field oscillations continues as we investigate a wide range of high latitude geophysical phenomena. Data from various events of interest to the scientific community are online for inspection from our colleagues and others interested in this type of activity.

The Freja Magnetic Field Experiment Home Page describes our efforts and available data in greater detail. More information on the Johns Hopkins University/Applied Physics Laboratory Space Department is available through the JHU/APL Space Department Home Page.

Contact: Jim_Gary@jhuapl.edu