Real-time determination and monitoring of the auroral electrojet boundaries

Magnar Gullikstad Johnsen

doi:10.1051/swsc/2013050

Abstract

A method for nowcasting of the auroral electrojet location from real-time geomagnetic data in the European sector is presented. Along the auroral ovals strong electrojet currents are flowing. The variation in the geomagnetic field caused by these auroral electrojets is observed on a routine basis at high latitudes using ground-based magnetometers. From latitude profiles of the vertical component of these variations it is possible to identify the boundaries of the electrojets. Using realtime data from ground magnetometer chains is the only existing method for continuous monitoring and nowcasting of the location and strength of the auroral electrojets in a given sector. This is an important aspect of any space weather programme. The method for obtaining the electrojet boundaries is described and assessed in a controlled environment using modelling. Furthermore a provisional, real-time electrojet tracker for the European sector based on data from the Tromsø Geophyiscal Observatory magnetometer chain is presented. The relationship between the electrojet and the diffuse auroral oval is discussed, and it is concluded that although there may exist time-dependent differences in boundary locations, there exists a general coincidence. Furthermore, it is pointed out that knowledge about the latitudinal location of the geomagnetic activity, that is the electrojets, is more critical for space weather sensitive, ground-based technology than the location of the aurora.

Highlights

The auroral ovals are oval-shaped bands of aurora with radii of approximately 3500 km and foci in the vicinity of the geomagnetic poles
In order to illustrate the method for obtaining the auroral electrojet boundaries, we have applied the method to the high latitude equivalent current system as derived from a model of the high latitude electric field and field aligned currents, the Weimer 2005 (W05) model (Weimer 2005a)
We have in this paper described a method for obtaining the poleward and equatorward boundaries of the auroral electrojets from a meridian chain of magnetometers

Summary

Introduction

The auroral ovals are oval-shaped bands of aurora with radii of approximately 3500 km and foci in the vicinity of the geomagnetic poles. This paper describes the method for an ‘‘Online provision of auroral alert and tracking system’’, an auroral electrojet tracker, as designed in order to meet the requirements of Deliverable 4.3 in ‘‘WP-4 Forecasting tools and Modeling’’ of the European Union Frame Work program 7 AFFECTS (Advanced Forecast For Ensuring Communications Through Space) project This auroral electrojet tracker, which is based on the assumption that the auroral electrojet is co-located with the auroral oval to a great extent, uses real-time measurements of the geomagnetic field variation to determine the equatorward and poleward edges of the auroral electrojet in the European sector. As determined by this method, in relation to auroral and precipitation boundaries and the possibilities of expanding and improving the current product, is discussed

Auroral oval determination by means of geomagnetic measurements – concept

The latitudinal signature of the auroral electrojet

Auroral electrojet location obtained from a model

Tromsø Geophysical Observatory – geomagnetic measurements

Auroral tracking and alert system based on TGO magnetometer data

Discussion and concluding remarks