Magnetospheric Physics: Substorms; Magnetospheric Physics: Magnetospheric configuration and dynamics; Magnetospheric Physics: Solar wind/magnetosphere interactions
Abstract :
[en] In this paper we determine the probability of substorm onset as a function of open magnetic flux in the magnetosphere by comparing the occurrence distribution of open flux observed at all times with that observed at the time of substorm onset. The open magnetic flux is measured in 12735 auroral images of the ionospheric polar cap from the IMAGE WIC detector. The probability of substorm onset is found to be negligible for fluxes below ~0.3 GWb, increases almost linearly until ~0.9 GWb, and is undefined above this. We also demonstrate that those substorms which show a clear particle injection signature at geosynchronous orbit, as measured by the LANL spacecraft, occur, on average, with higher values of open flux than those showing no activity. We discuss these results in the context of various hypotheses for substorm onset.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Boakes, P. D.; British Antarctic Survey, Cambridge, UK) ; AB(Department of Physics and Astronomy, University of Leicester, Leicester, UK) ; AC(British Antarctic Survey, Cambridge, UK) ; AD(British Antarctic Survey, Cambridge, UK) ; AE(British Antarctic Survey, Cambridge, UK) ; AF(Laboratory of Planetary and Atmospheric Physics, University of Liege, Liege, Belgium
Milan, S. E.
Abel, G. A.
Freeman, M. P.
Chisham, G.
Hubert, Benoît ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Language :
English
Title :
A statistical study of the open magnetic flux content of the magnetosphere at the time of substorm onset
Publication date :
01 February 2009
Journal title :
Geophysical Research Letters
ISSN :
0094-8276
eISSN :
1944-8007
Publisher :
Wiley, Washington, United States - District of Columbia
Abel, G. A., M. P. Freeman, A. J. Smith, and G. D. Reeves (2006), Association of substorm chorus events with drift echoes, J. Geophys. Res., 111, A11220, doi:10.1029/2006JA011860.
Akasofu, S. I. (1975), Roles of north-south component of interplanetary magnetic-field on large-scale auroral dynamics observed by DMSP satellite, Planet. Space Sci., 23, 1349-1354.
Baker, D. N., R. D. Belian, P. R. Higbie, and E. W. Hones (1979), High-energy magnetospheric protons and their dependence on geomagnetic and inter-planetary conditions, J. Geophys. Res., 84, 7138-7154.
Belian, R. D., D. N. Baker, P. R. Higbie, and E. W. Hones (1978), High-resolution energetic particle measurements at 6.6-RE: 2. High-energy proton drift echoes, J. Geophys. Res., 83, 4857-4862.
Belian, R. D., G. R. Gisler, T. Cayton, and R. Christensen (1992), High-Z energetic particles at geosynchronous orbit during the great solar proton event series of October 1989, J. Geophys. Res., 97, 16,897-16,906.
Boakes, P. D., S. E. Milan, G. A. Abel, M. P. Freeman, G. Chisham, B. Hubert, and T. Sotirelis (2008), On the use of IMAGE FUV forestimating the latitude of the open/closed magnetic field line boundary in the ionosphere, Ann. Geophys., 26, 2759-2769.
Büchner, J., and-L. M. Zelenyi (1987), Chaotization of the electron motion as the cause of an internal magnetotail instability and substorm onset, J. Geophys. Res., 92, 13,456-13,466.
Coumans, V., C. Blockx, J.-C. Gerard, B. Hubert, and M. Connors (2007), Global morphology of substorm growth phases observed by the IMAGE-SI12 imager, J. Geophys.Res., 112, A11211,doi:10.1029/2007JAO12329.
DeJong, A. D,, X. Cai, R. C. Clauer, and J. F. Spann (2007), Aurora and open magnetic flux during isolated substorms, sawteeth, and SMC events, Ann. Geophys., 25, 1865-1876.
Freeman, M. P., and S. K. Morley (2004), A minimal substorm model that explains the observed statistical distribution of times between substorms, Geophys. Res. Lett., 31, LI2807, doi:10.1029/2004GL019989.
Frey, H. U., S. B. Mende, V. Angelopoulos, and E. F. Donovan (2004), Substorm onset observations by IMAGE-FUV, J. Geophys. Res., 109, A10304, doi:10.1029/2004JA010607.
Hamming, R. W. (1989), Digital Filters, 3rd ed., Prentice Hall, Hertfordshire,U.K.
Henderson, M. G., G. D. Reeves, R. D. Belian, and J. S. Murphree (1996), Observations of magnetospheric substorms occurring with no apparent solar wind IMF trigger, J. Geophys. Res., 101, 10,773-10,791.
Hsu, TVS., and R. L. McPherron (2002), An evaluation of the statistical significance of the association between northward turnings of the interplanetary magnetic field and substorm expansion onsets, J. Geophys. Res., 107(All), 1398, doi:10.1029/2000JA000125.
Hsu, T.-S., and R. L. McPherron (2003), Occurrence frequencies of IMF triggered and nontriggered substorms, J. Geophys. Res., 108(A7), 1307, doi: 10.1029/2002JA009442.
Kamide, Y., P. D. Perreault, S. I. Akasofu, and J. D. Winningham (1977), Dependence of substorm occurrence probability on interplanetary magnetic field and on size of auroral oval, J. Geophys. Res., 82, 5521-5528.
Lyons, L. R., G. T. Blanchard, J. C. Samson, R. P. Lepping, T. Yamamoto, and T. Moretto (1997), Coordinated observations demonstrating external substorm triggering, J. Geophys. Res., 102, 27,039-27,051.
McPherron, R. L. (1970), Growth phase of magnetospheric substorms, J. Geophys. Res., 75, 5592-5599.
Mende, S. B., et al. (2000), Far ultraviolet imaging from the IMAGE spacecraft. 2. Wideband FUV imaging, Space Sci. Rev., 91, 271-285.
Milan, S. E., M. Lester, S. W. H. Cowley, K. Oksavik, M. Brittnacher, R. A. Greenwald, G. Sofko, and J. P. Villain (2003), Variations in the polar cap area during two substorm cycles, Ann. Geophys., 21, 1121-1140.
Milan, S. E., G. Provan, and B. Hubert (2007), Magnetic flux transport in the Dungey cycle: A survey of dayside and nightside reconnection rates, J. Geophys. Res., 112, A01209, doi:10.1029/2006JA011642.
Milan, S. E., P. D. Boakes, and B. Hubert (2008), Response of the expanding/contracting polar cap to weak and strong solar wind driving: Implications for substorm onset, J. Geophys. Res., 113, A09215, doi:10.1029/2008JA013340.
Milan, S. E., A. Grocott, C. Forsyth, S. M. Imber, P. D. Boakes, and B. Hubert (2009), A superposed epoch analysis of auroral evolution during substorm growth, onset and recovery: Open magnetic flux control of substorm intensity, Ann. Geophys., in press.
Morley, S. K., and M. P. Freeman (2007), On the association between northward turnings of the interplanetary magnetic field and substorm onsets, Geophys. Res. Lett., 34, L08104, doi:10.1029/2006GL028891.
Morley, S. K., M. P. Freeman, and E. I. Tanskanen (2007), A comparison of the probability distribution of observed substorm magnitude with that predicted by a minimal substorm model, Ann. Geophys., 25, 2427-2437.
Nakai, H., and Y. Kamide (2004), A critical condition in magnetotail pressure for leading to a substorm expansion onset: Geotail's observations, J. Geophys. Res., 109, A01205, doi:10.1029/2003JA010070.
Shukhtina, M. A., N. P. Dmitrieva, N. G. Popova, V. A. Sergeev, A. G. Yahnin, and I. V. Despirak (2005), Observational evidence of the loading-unloading substorm scheme, Geophys. Res. Lett., 32, L17107, doi:10.1029/2005GL023779.
