Physics
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsa32c..03b&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #SA32C-03
Physics
2411 Electric Fields (2712), 2439 Ionospheric Irregularities, 2471 Plasma Waves And Instabilities, 2736 Magnetosphere/Ionosphere Interactions, 2788 Storms And Substorms
Scientific paper
Near simultaneous formation of plasma density structures in the ionosphere at middle and equatorial latitudes during intense magnetic storms is investigated. The magnetic storms of July 15, 2000, March 30-31, 2001 and October 29 - 31, 2003 are studied. These storms are characterized by minimum SYM-H (1-min Dst) values of -350 nT, -420 nT and -400 nT respectively. The evolution of plasma density structures in the midlatitude and the equatorial ionosphere is investigated by measuring amplitude scintillation of satellite signals at 250 MHz and L-band, phase fluctuations of GPS signals and by detecting equatorial plasma bubbles with DMSP satellites. It is shown that at the time of the fast rate of change of SYM-H, an impulsive onset of scintillation occurs at Hanscom AFB, a sub-auroral station, and the associated plasma structures in the equatorial ionosphere are observed in the specific longitude sector for which the early evening period corresponds to the time of rapid SYM-H variation, as shown earlier for moderate storms (Basu et al., JGR, 2001). From continuous measurements of scintillation of signals from geostationary satellites and phase fluctuations of GPS signals, it is found that the onset of equatorial plasma structures is delayed by about 20 minutes from the onset of midlatitude scintillation. This delay is discussed in the framework of instantaneous storm-time electric field penetration from high latitudes to middle to equatorial latitudes and the instability growth time of sub-km scale irregularities. It is also shown that during intense storms, the equatorward neutral wind can cause the post-sunset plasma drift in the equatorial region to be as large as 200 m/sec in the westward direction in contrast to the quiet time drift of 100 m/sec in the eastward direction.
Basu Sarbani
Groves Keith M.
Keskinen Michael J.
MacKenzie E.
Rich F.
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