Real-time determination and monitoring of the auroral electrojet boundaries

Journal of Space Weather and Space Climate

Magnar Gullikstad Johnsen¹ 

[1] Tromsø Geophysical Observatory (TGO), University of Tromsø,N-9037 Tromsø,Norway

关键词: geomagnetism;    aeronomy;    space weather;    aurora;    ionosphere (auroral);   

Others  :  800664
DOI  :  doi:10.1051/swsc/2013050

 received in 2013-01-31, accepted in 2013-06-23,  发布年份 2013

【 摘 要 】

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.

【 授权许可】

   
© M.G. Johnsen, Published by EDP Sciences 2013

【 图 表 】

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9.

Fig. 10.

【 参考文献 】

• [1]Elphinstone, R.D., K. Jankowska, J.S. Murphree, and L.L. Cogger, The configuration of the auroral distribution for interplanetary magnetic field Bz northward. I – IMF Bx and By dependencies as observed by the Viking satellite, J. Geophys. Res., 95, 5791–5804, 1990.
• [2]Harang, L., The mean field of the polar earth-magnetic storm, Geofysiske Publikasjoner (Geophysica Norwegica), 16, 1–44, 1946a.
• [3]Harang, L., The mean field of disturbance of polar geomagnetic storms, Terrestrial Magnetism and Atmospheric Electricity (J. Geophys. Res.), 51, 353, 1946b.
• [4]Heppner, J.P., The Harang discontinuity in auroral belt ionospheric currents, Geofysiske Publikasjoner (Geophysica Norwegica), 29, 105–120, 1972.
• [5]Kabin, K., R. Rankin, G. Rostoker, R. Marchand, I.J. Rae, A.J. Ridley, T.I. Gombosi, C.R. Clauer, and D.L. DeZeeuw, Open-closed field line boundary position: a parametric study using an MHD model, J. Geophys. Res. (Space Phys.), 109, A05222, 2004.
• [6]Kisabeth, J.L., and G. Rostoker, Development of the polar electrojet during polar magnetic substorms, J. Geophys. Res., 76, 6815, 1971.
• [7]Machol, J.L., J.C. Green, R.J. Redmon, R.A. Viereck, and P.T. Newell, Evaluation of OVATION Prime as a forecast model for visible aurorae, Space Weather, 10, S03005, 2012.
• [8]Milan, S.E., M. Lester, S.W.H. Cowley, K. Oksavik, M. Brittnacher, R.A. Greenwald, G. Sofko, and J.-P. Villain, Variations in the polar cap area during two substorm cycles, Ann. Geophys., 21, 1121–1140, 2003.
• [9]Milan, S.E., G. Provan, and B. Hubert, Magnetic flux transport in the Dungey cycle: a survey of dayside and nightside reconnection rates, J. Geophys. Res., 112, A01209, 2007.
• [10]Newell, P.T., T. Sotirelis, J.M. Ruohoniemi, J.F. Carbary, K. Liou, J.P. Skura, C.-I. Meng, C. Deehr, D. Wilkinson, and F.J. Rich, OVATION: oval variation, assessment, tracking, intensity, and online nowcasting, Ann. Geophys., 20, 1039–1047, 2002.
• [11]Newell, P.T., T. Sotirelis, K. Liou, A.R. Lee, S. Wing, J. Green, and R. Redmon, Predictive ability of four auroral precipitation models as evaluated using Polar UVI global images, Space Weather, 8, S12004, 2010a.
• [12]Newell, P.T., T. Sotirelis, and S. Wing, Seasonal variations in diffuse, monoenergetic, and broadband aurora, J. Geophys. Res. (Space Phys.), 115, A03216, 2010b.
• [13]Rae, I.J., K. Kabin, J.Y. Lu, R. Rankin, S.E. Milan, F.R. Fenrich, C.E.J. Watt, J.-C. Zhang, A.J. Ridley, T.I. Gombosi, C.R. Clauer, G. Tóth, and D.L. DeZeeuw, Comparison of the open-closed separatrix in a global magnetospheric simulation with observations: the role of the ring current, J. Geophys. Res. (Space Phys.), 115, A08216, 2010.
• [14]Rostoker, G., and J.L. Kisabeth, Response of the polar electrojets in the evening sector to polar magnetic substorms, J. Geophys. Res., 78, 5559, 1973.
• [15]Rostoker, G., K. Kawasaki, T.J. Hughes, J.D. Winningham, and J.R. Burrows, Energetic particle precipitation into the high-latitude ionosphere and the auroral electrojets. II – Eastward electrojet and field-aligned current flow at the dusk meridian, J. Geophys. Res., 84, 2006–2018, 1979.
• [16]Sigernes, F., M. Dyrland, P. Brekke, S. Chernouss, D.A. Lorentzen, K. Oksavik, and C. Sterling Deehr, Two methods to forecast auroral displays, J. Space Weather Space Clim., 1, A03, 2011.
• [17]Starkov, G., Mathematical model of the auroral boundaries, Geomag. Aeron., 34, 331–336, 1994.
• [18]Vennerstrom, S., E. Friis-Christensen, T.S. Jorgensen, O. Rasmussen, C.R. Clauer, and V.B. Wickwar, Ionospheric currents and F-region plasma boundaries near the dayside cusp, Geophys. Res. Lett., 11, 903906, 1984.
• [19]Walker, J.K., Space-time associations of the aurora and magnetic disturbance, J. Atmos. Terr. Phys., 26, 951–954, 1964.
• [20]Wallis, D.D., G. Rostoker, and C.D. Anger, The spatial relationship of auroral electrojets and visible aurora in the evening sector, J. Geophys. Res., 81, 2857–2869, 1976.
• [21]Weimer, D.R., Improved ionospheric electrodynamic models and application to calculating Joule heating rates, J. Geophys. Res. (Space Phys.), 110, A05306, 2005a.
• [22]Weimer, D.R., Predicting surface geomagnetic variations using ionospheric electrodynamic models, J. Geophys. Res. (Space Phys.), 110, A12307, 2005b.
• [23]Winningham, J.D., K. Kawasaki, and G. Rostoker, Energetic particle precipitation into the high-latitude ionosphere and the auroral electrojets. I – Definition of electrojet boundaries using energetic electron spectra and ground-based magnetometer data, J. Geophys. Res., 84, 1993–2005, 1979.
• [24]Zhang, Y., and L.J. Paxton, An empirical Kp-dependent global auroral model based on TIMED/GUVIFUV data, J. Atmos. Sol. Terr. Phys., 70, 1231–1242, 2008.