ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-27-1207-2009 Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC Mayer C. 1 Jakowski N. 1 German Aerospace Center, Institute of Communications and Navigation, Kalkhorstweg 53, 17235 Neustrelitz, Germany 10 03 2009 27 3 1207 1212 Copyright: © 2009 C. Mayer 2009 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/27/1207/2009/angeo-27-1207-2009.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/27/1207/2009/angeo-27-1207-2009.pdf

Particle precipitation of magnetospheric origin causes additional ionization in the auroral zone at E-layer heights. During night-time, in particular at winter-night, the E-layer ionization may dominate over the F2-layer ionization level. To study the geophysical conditions and characteristics of the related ionospheric processes in more detail, we use GPS radio occultation electron density profile retrievals from CHAMP and Formosat-3/COSMIC to extract those vertical profiles which show the absolute maximum of ionization in the E-layer height range of 90–150 km. In order to select these profiles, we have developed an algorithm which can recognize the shape of a given profile by fitting an empirical Ansatz to it. Using data from CHAMP collected since 2002 and Formosat-3/COSMIC data starting from 2006, we are able to study both, the local-time dependence and the solar-cylce variability of the observed processes.

 References Feldstein, Y I.: On Morphology and Auroral and Magnetic Disturbances at High Latitudes, Geomagn Aeron., 3, 227–239, 1963. Feldstein, Y I., Holzworth, R H., and Meng, C.-I.: Feldstein/Holzworth/Meng Auroral boundary model, http://nssdcftp.gsfc.nasa.gov/models/ionospheric/auroral_oval/feldstein_holzworth, last access November 2008. Hajj, G A. and Romans, L J.: Ionospheric electron density profiles obtained with the Global Positioning System: Results from the GPS/MET experiment, Radio Sci., 33, 175–190, 1998. Hardy, D A., Gussenhoven, M S., Brautigam, D., and McNeil, W.: A statistical model of auroral ion precipitation. II – Functional representation of the average patterns, \jgr, 96, 5539–5547, 1991. Holzworth, R H. and Meng, C.-I.: Mathematical representation of the auroral oval, \grl, 2, 377–380, 1975. IGRF~CGM: http://modelweb.gsfc.nasa.gov/models/cgm/cgm.html, last access November 2008. Jakowski,~N., Wehrenpfennig, A.,~Heise, S.,~Reigber, Ch., Lühr, H., Grunwaldt, L., and Meehan, T. K.: GPS radio occultation measurements of the ionosphere from CHAMP: Early results, \grl, 29(10), 95.1–95.4, https://doi.org/10.1029/2001GL014364, 2002. Jakowski,~N.: Ionospheric GPS radio occultation measurements on board CHAMP, GPS Solutions, 9(2), 88–95, 2005. Jakowski, N., Tsybulya, K., Mielich, J., Belehaki, A., Altadill, D., Jodogne, J. C., and Zolesi, B.: Validation of GPS Radio Occultation Measurements on CHAMP by Vertical Sounding Observations in Europe, in: Earth Observation with CHAMP, Results from Three Years in Orbit, edited by: Reigber, C., Lühr, H., Schwintzer, P., and Wickert, J., Springer-Verlag Berlin, pp. 447–452, 2005. Jakowski,~N., Mayer, C., and Wilken, V.: Ionosphere Monitoring by Ground and Space Based GNSS techniques, Presenation at the FORMOSAT-3/COSMIC Workshop 2006, National Taiwan University, Taipei, Taiwan, 28 November–1 December 2006. Jayachandran, P T., Donovan, E F., MacDougall, J W., Moorcroft, D R., St Maurice, J.-P., and Prikryl, P.: SuperDARN E-region backscatter boundary in the dusk-midnight sector – tracer of equatorward boundary of the auroral oval, Ann. Geophys., 20, 1899–1904, 2002. Khazanov, G V., Gamayunov, K V., Gallagher, D L., and Spann, J F.: Strong pitch-angle diffusion of ring current ions in geomagnetic storm-associated conditions, J. Atmos. Sol.-Terr. Phys., 69, 142, https://doi.org/10.1016/j.jastp.2006.07.010, 2007. Markwardt,~C and Rivers, M.: mpfit.py, http://cars9.uchicago.edu/software/python/mpfit.html, last access November 2008. Mende, S B., Frey, H U., Lampton, M., Gerard, J.-C., Hubert, B., Fuselier, S., Spann, J., Gladstone, R., and Burch, J L.: Global observations of proton and electron auroras in a substorm, \grl, 28, 1139–1142, 2001. Rocken,~C., Kuo, Y.-H., Schreiner, W., Hunt, D., Sokolovskiy, S., and McCormick, C.: COSMIC system description, Terr. Atmos Oceanic Sci., 11, 157–186, 2000. Schreiner, W S., Sokolovskiy, S V., Rocken, C., and Hunt, D C.: Analysis and validation of GPS/MET radio occultation data in the ionosphere, Radio Sci., 34, 949–966, 1999. Schreiner,~W., Rocken, C., Sokolovsky. S., Syndergaard, S., and Hunt, D.: Estimates of the precision of GPS radio occultations from COSMIC/FORMOSAT-3 mission, \grl, submitted, 2009. SWACI: Space Weather Application Center Ionosphere, http://w3swaci.dlr.de, last access 2007. Reinisch, B W., Nsumei, P., Huang, X., and Bilitza, D K.: Modeling the F2 topside and plasmasphere for IRI using IMAGE/RPI and ISIS data, Adv. Space Res., 39, 731, https://doi.org/10.1016/j.asr.2006.05.032, 2007. Szuszczewicz, E. P., Wilkinson, P., Swider, W., Pulinets, S. A., Abdu, M. A., Roelof, E., Fuller-Rowell, T., Evans, D. S., Bateman, T., and Blanchard, P.: Measurements and empirical model comparisons of F-region characteristics and auroral oval boundaries during the solstitial SUNDIAL campaign of 1987, Ann. Geophys., 11, 601–613, 1993. Wehrenpfennig,~A., Jakowski, N., and Wickert, J.: A dynamically configurable system for operational processing of space weather data, Phys Chem Earth(C), 26(8), 601–604, 2001.