Unusual ionospheric absorption characterizing energetic electron precipitation into the South Atlantic Magnetic Anomaly
Earth, Planets and Space volume 54, pages 907–916 (2002)
An imaging riometer (IRIS) was installed newly in the southern area of Brazil in order to investigate precipitation of energetic electrons into the South Atlantic Magnetic Anomaly (SAMA). An unusual ionospheric absorption event was observed in the nighttime (∼20 h LT) near the maximum depression (D st ∼ −164 nT) and the following positive excursion during the strong geomagnetic storm on September 22–23, 1999. The unusual absorption that has short time-duration of 30–40 min shows two characteristic features: One feature is a sheet structure of the absorption appearing at the high-latitude part of the IRIS field-of-view, showing an eastward drift from the western to the eastern parts and subsequent retreat to the western part. Another feature is a meridionally elongated structure with a narrow longitudinal width (100–150 km) appearing from the zenith to the low-latitude part of the IRIS field-of-view, enhanced simultaneously with the sheet absorption, and is subsequently changed to a localized structure. These features likely characterize precipitation of energetic electrons into the SAMA ionosphere, associated with substorm occurrences during the strong geomagnetic storm. From the eastward drift (∼250 m/s) of the sheet absorption, precipitating electrons are estimated to be ∼20 keV energies, assuming plasmaspheric electric fields of 1.8 mV/m. However, no ionospheric effect due to the precipitating electrons was definitely detected by the ionosonde measurements at Cachoeira Paulista, separated eastward by about 1000 km from the IRIS station.
Abdu, M. A., S. S. Degaonkar, and K. R. Ramanathan, Attenuation of galactic noise at 25 MHz and 21.3 MHz in the ionosphere over Ahmedabad during 1957–1964, J. Geophys. Res., 72, 1547–1554, 1967.
Abdu, M. A., S. Ananthakrishman, E. F. Coutinho, B. A. Krishnan, and S. Reis, Azimuthal drift and precipitation of electrons into the South Atlantic geomagnetic anomaly during a SC magnetic storm, J. Geophys. Res., 78, 5830–5836, 1973.
Abdu, M. A. and I. S. Batista, Sporadic E-layer phenomena in the Brazilian geomagnetic anomaly; evidence for a regular particle ionization sources, J. Atmos. Terr. Phys., 39, 723–731, 1977.
Abdu, M. A., I. S. Batista, L. R. Piazza, and O. Massambani, Magnetic storm associated enhanced particle precipitation in the South Atlantic anomaly: Evidence from VLF phase measurements, J. Geophys. Res., 86, 7533–7542, 1981.
Abel, B. and R. M. Thorne, Modeling energetic electron prcipitation near the South Atlantic anomaly, J. Geophys. Res., 104, 7037–7044, 1999.
Baker, D. N., J. B. Blake, L. B. Callis, J. R. Cummings, D. Hovestadt, S. Kanekal, B. Klecker, R. A. Mewaldt, and R. D. Zwickl, Relativistic electron acceleration and decay time scales in the inner and outer radiation belts: SAMPEX, Geophys. Res. Lett., 21, 409–412, 1994.
Badhwar, G. D., Drift rate of the South Atlantic Anomaly, J. Geophys. Res., 102, 2343–2349, 1997.
Batista, I. S. and M. A. Abdu, Magnetic storm associated delayed sporadic E enhancements in the Brazilian geomagnetic anomaly, J. Geophys. Res., 82(29), 4777–4783, 1977.
Detrick, D. and T. J. Rosenberg, A phased array radio wave imager for studies of cosmic noise absorption, Radio Sci., 25, 325–338, 1990.
Gledhill, J. A., Aeronomic effects in the South Atlantic anomaly, Rev. Geophys. Space Res., 14, 173–187, 1976.
Gledhill, J. A. and R. A. Hoffman, Nighttime observation of 0.2- to 26 keV electrons in the South Atlantic anomaly made by Atmospheric Explorer C, J. Geophys. Res., 86, 6739–6744, 1981.
Gonzalez, W. D., S. L. G. Dutra, and O. Pinto, Jr., Middle atmospheric electrodynamic modification by particle precipitation at the South Atlantic Magnetic Anomaly, J. Atmos. Terr. Phys., 49, 377–383, 1987.
Gonzalez, W. D., O. Pinto, Jr., and O. Mendes, Jr., Large plasmaspheric electric fields at L ~ 2 measured by the S3-3 satellite during strong geomagnetic activity, Geophys. Res. Lett., 13, 363–365, 1986.
Heirtzler, J. R. and J. H. Allen, Ever-present South Atlantic anomaly damages spacecraft, EOS Trans. AGU, 83(15), 165/169, 2002.
Jayanthi, U. B., M. G. Pereira, I. M. Martin, Y. Stozkov, F. D’Amico, and T. Villela, Electron precipitation associated with geomagnetic activity: Balloon observation of X ray flux in South Atlantic anomaly, J. Geophys. Res., 102, 24069–24073, 1997.
Kikuchi, T. and D. S. Evans, Energetic electrons observed by NOAA-6 over Japan (L = 1.3) at the time of geomagnetic storm on February 8–9, 1986, Proc. Res. Inst. Atmos., Nagoya Univ., 36, 137–149, 1989.
Kohno, T., K. Munakata, K. Nagata, H. Murakami, A. Nakamoto, N. Hasebe, J. Kikuchi, and J. Doke, Intensity maps of MeV electrons and protons below the radiation belt, Planet. Space Sci., 38, 483–490, 1990.
Lühr, H., A. Aylward, S. C. Bucher, K. Pajunpaa, T. Holmboe, and S. M. Zalewski, Westward moving substorm features observed with the IMAGE magnetometer network and the ground-based instruments, Ann. Geophys., 16, 425–440, 1998.
Nishino, M., Y. Tanaka, T. Oguti, H. Yamagishi, and J. A. Holtet, Initial observation results with imaging riometer at Ny Alesund (L= 16), Proc. NIPR Symp. Upper Atmos. Phys., 6, 47–61, 1993.
Obara, T., M. Den, Y. Miyoshi, and A. Morioka, Energetic electron variation in the outer radiation zone during early May 1998 magnetic storm, J. Atmos. Solar-Terr. Phys., 62, 1405–1412, 2000.
Paulikas, G. A., Precipitation of particles at low and middle latitudes, Rev. Geophysics and Space Physics, 13, 709–734, 1975.
Pinto, O. Jr., and W. D. Gonzalez, X ray measurements at the South Atlantic magnetic anomaly, J. Geophys. Res., 91, 7072–7078, 1986.
Pinto, O. Jr., and W. D. Gonzalez, Energetic electron precipitation at the South Atlantic magnetic anomaly: a review, J. Atmos. Terr. Phys., 51(5), 351–365, 1989.
Pinto, O., Jr., W. D. Gonzalez, and N. M. Paes Leme, VLF disturbances at the South Atlantic Magnetic Anomaly following magnetic storms, Planet. Space Sci., 38, 633–636, 1990.
Rees, M. H., Auroral ionization and excitation by incident energetic electrons, Planet. Space Sci., 11, 1209, 1963.
Sato, M., H. Yamagishi, Y. Kato, and M. Nishino, Quick-look system of auroral absorption images by imaging riometer, Antarctic Rec, 36, 251–267, 1992 (in Japanese with English abstract).
Stauning, P., S. Henriksen, and H. Yamagishi, Imaging riometer installation in Danmarkshavn, Greenland, Danish Meteorological Institute, Technical Rep, 92–4, 1–25, 1992.
Takeda, M., T. Iyemori, and T. Kamei, World Data Center for Geomagnetism, Data Catalogue, 25, 133, 1999.
Torr, D. G., M. R. Torr, and J. C. G. Walker, Particle precipitation in the South Atlantic geomagnetic anomaly, Planet. Space Sci, 23, 15–26, 1975.
Trivedi, N. B., D. B. Rai, I. M. Martin, and J. M. Da Costa, Particle precipitation in Brazilian geomagnetic anomaly during magnetic storms, Planet. Space. Sci, 21, 1699–1704, 1973.
Vampola, A. L. and D. J. Gorney, Electron energy deposition in the middle atmosphere, J. Geophys. Res., 88, 6267–6274, 1983.
About this article
Cite this article
Nishino, M., Makita, K., Yumoto, K. et al. Unusual ionospheric absorption characterizing energetic electron precipitation into the South Atlantic Magnetic Anomaly. Earth Planet Sp 54, 907–916 (2002). https://doi.org/10.1186/BF03352438