Physics
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agusmsa31b..07d&link_type=abstract
American Geophysical Union, Spring Meeting 2009, abstract #SA31B-07
Physics
0360 Radiation: Transmission And Scattering, 2407 Auroral Ionosphere (2704), 2423 Ionization Processes (7823), 2475 Polar Cap Ionosphere, 2479 Solar Radiation And Cosmic Ray Effects
Scientific paper
Ionization effects produced at the northern polar ionosphere and upper atmosphere by energetic particles during December 2006 were studied. That period was accompanied by several solar flares and solar energetic particle (SEP) events as well as by several weak and one strong magnetic storms. Fluxes and spectra of energetic protons and electrons precipitating to the high-latitude and polar regions were measured by a constellation of four POES satellites at low-altitude orbit. The precipitating particles of solar, interplanetary and magnetospheric origin demonstrate different spectral properties and spatial distributions that permit us to study their dynamics separately. Magnetospheric particles are electrons having soft spectra and precipitating predominantly at auroral ionosphere. SEP together with particles accelerated at leading edge of interplanetary transients are characterized by higher energies and harder spectra. They penetrate to the magnetosphere in the polar cap region and causing abundant ionization of the lower ionosphere and upper atmosphere. Using POES data and standard models of the ionosphere and atmosphere we calculated height profiles of specific ionization produced by the SEP in the polar cap. The dynamics of SEP ionization reveals three intensifications at heights from 50 to 100 km in 7 to 8, 13 and 14 December. At the same time the ionization was measured as electron content (EC) by the COSMIC/FORMOSAT-3 constellation of six satellites. That experiment provides a 3- D tomography of the ionosphere and upper atmosphere on the base of radio occultation technique, which makes use of radio signals transmitted by the GPS satellites. We found that the observed temporal and spatial patterns of EC are pretty close to the dynamics of specific ionization, produced by the SEP and in particular by the electrons. Namely, the spatial region of enhanced ionization is overlapped pretty well with the enhancements of the electrons penetrating to the bottom ionosphere and upper atmosphere. The importance of energetic electrons in the polar cap absorption effects is discussed.
Dmitriev A. V.
Tsai L.-C.
Yeh Hsien-Chi
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