ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-28-1659-2010 Estimating the location of the open-closed magnetic field line boundary from auroral images Longden N. 1 Chisham G. 1 Freeman M. P. 1 Abel G. A. 1 Sotirelis T. 2 British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA 10 09 2010 28 9 1659 1678 Copyright: © 2010 N. Longden et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/28/1659/2010/angeo-28-1659-2010.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/28/1659/2010/angeo-28-1659-2010.pdf

The open-closed magnetic field line boundary (OCB) delimits the region of open magnetic flux forming the polar cap in the Earth's ionosphere. We present a reliable, automated method for determining the location of the poleward auroral luminosity boundary (PALB) from far ultraviolet (FUV) images of the aurora, which we use as a proxy for the OCB. This technique models latitudinal profiles of auroral luminosity as both a single and double Gaussian function with a quadratic background to produce estimates of the PALB without prior knowledge of the level of auroral activity or of the presence of bifurcation in the auroral oval. We have applied this technique to FUV images recorded by the IMAGE satellite from May 2000 until August 2002 to produce a database of over a million PALB location estimates, which is freely available to download. From this database, we assess and illustrate the accuracy and reliability of this technique during varying geomagnetic conditions. We find that up to 35% of our PALB estimates are made from double Gaussian fits to latitudinal intensity profiles, in preference to single Gaussian fits, in nightside magnetic local time (MLT) sectors. The accuracy of our PALBs as a proxy for the location of the OCB is evaluated by comparison with particle precipitation boundary (PPB) proxies from the DMSP satellites. We demonstrate the value of this technique in estimating the total rate of magnetic reconnection from the time variation of the polar cap area calculated from our OCB estimates.

 References Akasofu, S.-I. and Kimball, D.: Auroral morphology as shown by all-sky photographs: {A}rctic and {A}ntarctic, Annals of the International Geophysical Year, 38, 1965. Baker, J., Clauer, C., Ridley, A., Papitashvili, V., Brittnacher, M., and Newell, P.: The nightside poleward boundary of the auroral oval as seen by DMSP and the Ultraviolet Imager, J. Geophys. Res., 105, 21267–21280, 2000. Baker, K. and Wing, S.: A new magnetic coordinate system for conjugate studies at high latitudes, J. Geophys. Res., 94, 9139–9143, 1989. Baker, K., Dudeney, J., Greenwald, R., Pinnock, M., Newell, P., Roger, A., Mattin, N., and Meng, C.-I.: HF radar signatures of the cusp and low-latitude boundary layer, J. Geophys. Res., 100, 7671–7695, 1995. Baker, K., Rodger, A., and Lu, G.: HF}-radar observations of the dayside magnetic merging rate: {A {G}eospace {E}nvironment {M}odeling boundary layer campaign study, J. Geophys. Res., 102, 9603–9617, 1997. Blanchard, G., Lyons, L., Samson, J., and Rich, F.: Locating the polar cap boundary from observations of 6300\AA auroral emission, J. Geophys. Res., 100, 7855–7862, 1995. Boakes, P. D., Milan, S. E., Abel, G. A., Freeman, M. P., Chisham, G., Hubert, B., and Sotirelis, T.: On the use of IMAGE FUV for estimating the latitude of the open/closed magnetic field line boundary in the ionosphere, Ann. Geophys., 26, 2759–2769, https://doi.org/10.5194/angeo-26-2759-2008, 2008. Brittnacher, M., Fillingim, M., and Parks, G.: Polar cap area and boundary motion during substorms, J. Geophys. Res., 104, 12251–12262, 1999. Burch, J.: IMAGE mission overview, Space Sci. Rev., 91, 1–14, 2000. Carbary, J., Sotirelis, T., Newell, P., and Meng, C.-I.: Auroral boundary correlations between UVI and DMSP, J. Geophys. Res., 108, 1018, <a href="http://dx.doi.org/10.1029/2002JA009378">https://doi.org/10.1029/2002JA009378</a>, 2003. Chisham, G. and Freeman, M. P.: A technique for accurately determining the cusp-region polar cap boundary using SuperDARN HF radar measurements, Ann. Geophys., 21, 983–996, https://doi.org/10.5194/angeo-21-983-2003, 2003. Chisham, G., Pinnock, M., and Rodger, A.: The response of the HF radar spectral width boundary to a switch in the IMF <i>B<sub>y</sub></i> direction: {I}onospheric consequences of transient dayside reconnection?, J. Geophys. Res., 106, 191–202, 2001. Chisham, G., Pinnock, M., Coleman, I. J., Hairston, M. R., and Walker, A. D. M.: An unusual geometry of the ionospheric signature of the cusp: implications for magnetopause merging sites, Ann. Geophys., 20, 29–40, https://doi.org/10.5194/angeo-20-29-2002, 2002. Chisham, G., Freeman, M. P., Coleman, I. J., Pinnock, M., Hairston, M. R., Lester, M., and Sofko, G.: Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field, Ann. Geophys., 22, 4243–4258, https://doi.org/10.5194/angeo-22-4243-2004, 2004. Chisham, G., Freeman, M., Abel, G., Lam, M., Pinnock, M., Coleman, I., Milan, S., Lester, M., Bristow, W., Greenwald, R., Sofko, G., and Villain, J.-P.: Remote sensing of the spatial and temporal structure of the magnetopause and magnetotail reconnection from the ionosphere, Rev. Geophys., 46, RG1004, <a href="http://dx.doi.org/10.1029/2007RG000223">https://doi.org/10.1029/2007RG000223</a>, 2008. DeJong, A. D., Cai, X., Clauer, R. C., and Spann, J. F.: Aurora and open magnetic flux during isolated substorms, sawteeth, and SMC events, Ann. Geophys., 25, 1865–1876, https://doi.org/10.5194/angeo-25-1865-2007, 2007. Elphinstone, R., Jankowska, K., Murphree, J., and Cogger, L.: The configuration of the auroral distribution for interplanetary magnetic field <i>B<sub>Z</sub></i> northward. 1. IMF <i>B<sub>x</sub></i> and <i>B<sub>y</sub></i> dependencies as observed by the {V}iking satellite, J. Geophys. Res., 95, 5791–5804, 1990. Elphinstone, R., Hearn, D., Cogger, L., Murphree, J., Wright, A., Sandahl, I., Ohtani, S., Neweel, P., Klumpar, D., Shapsak, M., Potemra, T., Mursula, K., and Sauvaud, J.: The double oval UV auroral distribution. 2. {T}he most poleward arc system and the dynamics of the magnetotail, J. Geophys. Res., 100, 12093–12102, 1995a. Elphinstone, R., Murphree, J., Hearn, D., Cogger, L., Sandahl, I., Newell, P., Klumpar, D., Ohtani, S., Sauvaud, J., Potemra, T., Mursula, K., Wright, A., and Shapshak, M.: The double oval UV auroral distribution. 1. {I}mplications for the mapping of auroral arcs, J. Geophys. Res., 100, 12075–12092, 1995b. Feldstein, Y. and Galperin, Y.&nbsp;I.: The auroral luminosity structure in the high-latitude upper atmosphere: its dynamics and relationship to the large-scale structure of the {E}arth's magnetosphere, Rev. Geophys., 23, 217–275, 1985. Frey, H.: Localized aurora beyond the auroral oval, Rev. Geophys., 45, RG1003, <a href="http://dx.doi.org/10.1029/2005RG000174">https://doi.org/10.1029/2005RG000174</a>, 2007. Frey, H. and Mende, S.: Substorm onsets as observed by IMAGE-FUV, in: Proceedings of the Eigth International Conference on Substorms (ICS-8), edited by: Syrjäsuo, M. and Donovan, E. F., University of Calgaray, Alberta, Canada, 71–75, 2006. Frey, H., Mende, S., and Angelopoulos, V.: Substorm onset observations by IMAGE-FUV, J. Geophys. Res., 109, A10304, <a href="http://dx.doi.org/10.1029/2004JA010607">https://doi.org/10.1029/2004JA010607</a>, 2004. Gibson, W., Burch, J., Scherrer, J., Tapley, M., Killough, R., Volpe, F., Davis, W., Vaccarello, D., Grismore, G., Sakkas, D., and Housten, S.: The IMAGE observatory, Space Sci. Rev., 91, 15–50, 2000. Gjerloev, J., Hoffman, R., Sigwarth, J., and Frank, L.: Statistical description of the bulge-type auroal substorm in the far ultraviolet, J. Geophys. Res., 112, A07213, <a href="http://dx.doi.org/10.1029/2006JA012189">https://doi.org/10.1029/2006JA012189</a>, 2007. Gjerloev, J., Hoffman, R., Sigwarth, J., Frank, L., and Baker, J.: Typical auroral substorm: A bifurcated oval, J. Geophys. Res., 113, A03211, <a href="http://dx.doi.org/10.1029/2007JA012431">https://doi.org/10.1029/2007JA012431</a>, 2008. Hardy, D., Schmitt, L., Gussenhoveann, M., Marshall, F., Yeh, H., Schumaker, T., Huber, A., and Pantazis, J.: Precipitating electron and ion detectors (SSJ/4) for the block 5D}/flights 6-10 {DMSP satellites: {C}alibration and data presentation, in: Environmental Research Papers, 902, Air Force Geophysics Laboratory, Hanscom Air Force Base, MA, 1984. Hoffman, R. A., Gjerloev, J. W., Frank, L. A., and Sigwarth, J. W.: Are there optical differences between storm-time substorms and isolated substorms?, Ann. Geophys., 28, 1183–1198, https://doi.org/10.5194/angeo-28-1183-2010, 2010. Hubert, B., Miolan, S., Grocott, A., Blockx, C., Cowley, S., and Gérard, J.-C.: Dayside and nightside reconnection rates inferred from IMAGE FUV and {S}uper {D}ual {A}uroral {R}adar {N}etwork data, J. Geophys. Res., 111, A03217, <a href="http://dx.doi.org/10.1029/2005JA011140">https://doi.org/10.1029/2005JA011140</a>, 2006. Iijima, T. and Potemra, T.: Large-scale characteristics of field-aligned currents associated with substorms, J. Geophys. Res., 83, 599–615, 1978. Immel, T., Craven, J., and Nicholas, A.: An empiracal model of the OI FUV dayglow from DE-1 images, J. Atmos. Sol.-Terr. Phy., 62, 47–64, 2000. Kauristie, K., Weygand, J., Pulkkinen, T., Murphree, J., and Newell, P.: Size of the auroral oval: UV ovals and precipitation boundaries compared, J. Geophys. Res., 104, 2321–2331, 1999. Makita, K. and Meng, C.-I.: Average electron precipitation patterns and visual aurora characteristics during geomagnetic quiescence, J. Geophys. Res., 89, 2861–2872, 1984. Makita, K., Meng, C.-I., and Akasofu, S.-I.: The shift of the auroral electron precipitation boundaries in the dusk-dawn sector in association with geomagnetic activity and interplanetary magnetic field, J. Geophys. Res., 88, 7967–7981, 1983. Meier, R.: Ultraviolet spectroscopy and remote sensing of the upper atmosphere, Space Sci. Rev., 58, 1–185, 1991. Mende, S., Heetderks, H., Frey, H., Lampton, M., Geller, S., Abiad, R., Siegmund, O., Tremsin, A., Spann, J., Dougani, H., Fuselier, S., Magoncelli, A., Bumala, M., Murphree, S., and Trondsen, T.: Far ultraviolet imaging from the IMAGE spacecraft. 2. Wideband FUV imaging, Space Sci. Rev., 91, 271–285, 2000a. Mende, S., Heetderks, H., Frey, H., Lampton, M., Geller, S., Habraken, S., Renotte, E., Jamar, C., Rochus, P., Spann, J., Fuselier, S., Gerard, J.-C., Gladstone, R., Murphree, S., and Cogger, L.: Far ultraviolet imaging from the IMAGE spacecraft. 1. {S}ystem design, Space Sci. Rev., 91, 243–270, 2000b. Mende, S., Heetderks, H., Frey, H., Stock, J., Lampton, M., Geller, S., Abiad, R., Siegmund, O., Habraken, S., Renotte, E., Jamar, C., Rochus, P., Gerard, J.-C., Sigler, R., and Lauche, H.: Far ultraviolet imaging from the IMAGE spacecraft. 3. Spectral imaging of the {L}yman-α and OI 135.6 nm, Space Sci. Rev., 91, 287–318, 2000c. Mende, S., Frey, H., Morsony, B., and Immel, T.: Statistical behaviour of proton and electron auroras during substorms, J. Geophys. Res., 108, 1339, <a href="http://dx.doi.org/10.1029/2002JA009751">https://doi.org/10.1029/2002JA009751</a>, 2003. Meurant, M., Gérard, J.-C., Hubert, B., Coumans, V., Blockx, C., Østgaard, N., and Mende, S.: Dynamics of global scale electron and proton precipitation induced by a solar wind pressure pulse, Geophys. Res. Lett., 30, 2032, <a href="http://dx.doi.org/10.1029/2003GL018017">https://doi.org/10.1029/2003GL018017</a>, 2003. Milan, S. E. and Lester, M.: A classification of spectral populations observed in HF radar backscatter from the E region auroral electrojets, Ann. Geophys., 19, 189–204, https://doi.org/10.5194/angeo-19-189-2001, 2001. Milan, S. E., Lester, M., Cowley, S. W. H., Moen, J., Sandholt, P. E., and Owen, C. J.: Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study, Ann. Geophys., 17, 159–172, https://doi.org/10.1007/s00585-999-0159-5, 1999. Milan, S. E., Lester, M., Cowley, S. W. H., Oksavik, K., Brittnacher, M., Greenwald, R. A., Sofko, G., and Villain, J.-P.: Variations in the polar cap area during two substorm cycles, Ann. Geophys., 21, 1121–1140, https://doi.org/10.5194/angeo-21-1121-2003, 2003. Mishin, V.: The magnetogram inversion technique and some applications, Space Sci. Rev., 53, 83–163, 1990. Mishin, V., Bazarzhapov, A., Saifudinova, T., Lunyushkin, S., Shirapov, S.&nbsp;S., Woch, J., Eliasson, L., Opgenoorth, H., and Murphree, J.: Different methods to determine the polar cap area, J. Geomagn. Geoelectr., 44, 1207–1214, 1992. Newell, P., Burke, W., Sánchez, E., Meng, C.-I., Greenspan, M., and Clauer, C.: The low-latitude boundary layer and the boundary plasma sheet at low altitude: {P}renoon precipitation regions and convection reversal boundaries, J. Geophys. Res., 96, 21013–21023, 1991. Newell, P., Feldstein, Y., Galperin, Y., and Meng, C.-I.: Morphology of nightside precipitation, J. Geophys. Res., 101, 10737–10748, 1996. Newell, P., Xu, D., Meng, C.-I., and Kivelson, M.: Dynamical polar cap: A unifying approach, J. Geophys. Res., 102, 127–139, 1997. Newell, P., Liou, K., and Wilson, G.: Polar cap particle precipitation and aurora: {R}eview and commentary, J. Atmos. Solar-Terr. Phys., 71, 199–215, <a href="http://dx.doi.org/10.1016/j.jastp.2009.11.004">https://doi.org/10.1016/j.jastp.2009.11.004</a>, 2009. Pinnock, M., Chisham, G., Coleman, I. J., Freeman, M. P., Hairston, M., and Villain, J.-P.: The location and rate of dayside reconnection during an interval of southward interplanetary magnetic field, Ann. Geophys., 21, 1467–1482, https://doi.org/10.5194/angeo-21-1467-2003, 2003. Press, W., Teukolsky, S., Vetterling, W., and Flannery, B.: Numerical Recipes in C. The Art of Scientific Computing, Cambridge University Press, 2nd edn., 1992. Sandholt, P., Farrugia, C., Øieroset, M., Stauning, P., and Denig, W.: Auroral activity associated with unsteady magnetospheric erosion: {O}bservations on {D}ecember 18, 1990, J. Geophys. Res., 103, 2309–2317, 1998. Siscoe, G. and Huang, T.: Polar cap inflation and deflation, J. Geophys. Res., 90, 543–547, 1985. Sotirelis, T. and Newell, P.: Boundary-oriented electron precipitation model, J. Geophys. Res., 105, 18655–18673, 2000. Vampola, A.: Access of solar electrons to closed field lines, J. Geophys. Res., 76, 36–43, 1971.