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Daytime ionospheric absorption features in the polar cap associated with poleward drifting F-region plasma patches
Earth, Planets and Spacevolume 50, pages107–117 (1998)
Absorption of radio waves in the polar ionosphere near the magnetic noon was observed on October 8, 1991, by the 30 MHz imaging riometer at Ny-Alesund, Svalbard (invariant latitude 76.1°). These observations showed that the initially widespread absorption features became localized and enhanced in the high-latitude sector of the field of view, and followed a poleward motion. This behavior occurred quasi-periodically and repeated every 10–20 min. Simultaneous observations by EISCAT “Polar” experiments showed that nine discrete plasma patches, with F-region electron density enhanced by an order of 106 el/cm3, drifted poleward from the polar cusp to the cap during the same period. This coincidence suggested that the ionospheric absorption was associated with F-region plasma patches in the polar cap. Theoretical absorption values of 0.14 dB, estimated using the electron densities and the electron-ion collision frequencies from the EISCAT F-region plasma data, are smaller than the observed values (<0.8 dB). This discrepancy may be related to the difference between the theoretically- and experimentally-determined collision frequencies, as indicated by Wang et al. (1994). These localized, enhanced, and poleward drifting absorption features over Ny-Alesund may be explained as F-region plasma patches produced by a magnetosheath-like particle precipitation into the cusp, and as small-scale irregularities caused by density gradients of the patches drifting into the polar cap.
Aggarwal, K. M., Narinder Nath, and C. S. K. Setty, Collision frequency and transport properties of electrons in the ionosphere, Planet. Space Sci., 27, 753–768, 1979.
Anderson, D. N., J. Buchau, and R. A. Heelis, Origin of density enhancements in the winter polar cap ionosphere, Radio Sci., 23, 513–519, 1988.
Baker, K. B., R. A. Greenwald, J. M. Ruohoniemi, J. R. Dedeny, M. Pinnock, N. Mattin, and J. M. Leonard, PACE, Polar Anglo-American Conjugate Experiment, EOS Trans. AGU, 70, 785, 1989.
Cowley, S. W. H., M. P. Freeman, M. Lockwood, and M. F. Smith, The ionospheric signature of flux transfer events, in CLUSTER-Dayside Polar Cusp, ESA SP-330, pp. 105–112, ESTEC, Nordvijk, The Netherlands, 1991.
Detrick, D. L. and T. J. Rosenberg, A phased-array radio wave imager for studies of cosmic noise absorption, Radio Sci., 25, 325–338, 1990.
Foster, J. C., Storm time plasma transport at middle and high latitude, J. Geophys. Res., 98, 1675–1689, 1993.
Kirkwood, S., Modeling the undisturbed high-latitude region, Adv. Space Res., 13, 3, 101–104, 1993.
Lockwood, M. and H. C. Carlson, Jr., Production of polar cap electron density patches by transient magnetopause reconnection, Geophys. Res. Lett., 19, 1731–1734, 1992.
Lockwood, M. and M. F. Smith, The variation of reconnection rate at the dayside magnetopause and cusp ion precipitation, J. Geophys. Res., 97, 14,841–14,847, 1992.
Lockwood, M., P. E. Sandholt, A. D. Farmer, S. W. H. Cowley, B. Lybekk, and V. N. Davda, Auroral and plasma flow transients at magnetic noon, Planet. Space Sci., 38, 8, 973–993, 1990.
Lockwood, M., W. F. Denig, A. D. Farmer. V. N. Davda, S. W. H. Cowley, and H. Luhr, Ionospheric signatures of pulsed reconnection at the Earth’ magnetopause, Nature, 361, 4, 424–428, 1993.
Newell, P. T. and C. I. Meng, Mapping the dayside ionosphere to the magnetosphere according to particle precipitation characteristics, Geophys. Res. Lett., 19, 6, 609–612, 1992.
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 Symposium on Upper Atmosphere Physics, No. 6, 47–61, 1993.
Nishino, M., H. Yamagishi, P. Stauning, T. J. Rosenberg, and J. A. Holtet, Location, spatial scale and motion of radio wave absorption in the cusp-latitude ionosphere observed by imaging riometers, J. Atmos. Terr. Phys., 59, 8, 903–924, 1997.
Rodger, A. S., M. Pinnock, J. R. Dudeney, K. B. Baker, and R. A. Greenwald, A new mechanism for polar patch formation, J. Geophys. Res., 99, 6425–6436, 1994.
Rosenberg, T. J., Z. Wang, A. S. Rodger, J. R. Dudeney, and K. B. Baker, Imaging riometer and HF radar measurements of drifting F region electron density structures in the polar cap, J. Geophys. Res., 98, 7757–7764, 1993.
Russell, C. T. and R. C. Elphic, Initial ISEE magnetometer results: Magntopause observations, Space Sci. Rev., 22, 681–715, 1978.
Sandholt, P. E., C. S. Dehr, A. Egeland, B. Lybekk, R. Viereck, and G. L. Romick, Signatures in the dayside aurora of plasma transfer from the magnetosheath, J. Geophys. Res.91, A9, 10,063–10,079, 1986.
Setty, C. S. G. K., A. R. Jain, and M. K. Vyawahare, Collision frequency of electrons in the F-region, Can, J. Phys., 48, 653–658, 1970.
Stauning, P., Absorption of cosmic noise in the E-region during electron heating events. A new class of riometer absorption events. Geophys. Res. Lett., 11, 1184–1187, 1984.
Stauning, P., Investigations of ionospheric radio wave absorption processes using imaging riometer techniques, J. Atmos. Terr. Phys., 58, 6, 753–764, 1996a.
Stauning, P., High-latitude D- and E-region investigations using imaging riometer observations, J. Atmos. Terr. Phys., 58, 6, 765–783, 1996b.
Stauning, P. and J. K. Olesen, Observations of the unstable plasma in the disturbed polar E-region, Physica Scripta, 40, 325–332, 1989.
Wang, Z., T. J. Rosenberg, P. Stauning, S. Basu, and G. Crowley, Calculations of riometer absorption associated with F region plasma structures based on Sondre Stromfjord incoherent scatter radar observations, Radio Sci., 29, 209–215, 1994.
Yamagishi, H., M. Nishino, M. Sato, Y. Kato, M. Kojima, N. Sato, and T. Kikuchi, Development of imaging riometers, Antarctic Record, 36, 2, 227–250, 1992 (in Japanese).