HR: 10:50h
AN: SA32C-03    [Abstracts]
TI: Near Synchronous Plasma Structuring in the Middle and Equatorial Ionosphere During Intense Magnetic Storms
AU: * Basu, S
EM: basu@ppd.nrl.navy.mil
AF: Air Force Research Lab, AFRL/VSBX, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: Basu, S
EM: basu@bu.edu
AF: Boston University, Center for Space Research, 725 Commonwealth Avenue, Boston, MA 02215 United States
AU: Groves, K M
EM: Keith.Groves@hanscom.af.mil
AF: Air Force Research Lab, AFRL/VSBX, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: MacKenzie, E
EM: Eileen.Mackenzie@hanscom.af.mil
AF: Boston College, Institute for Scientific Research, 140 Commonweealth Avenue, Chestnut Hill, MA 02467 United States
AU: Keskinen, M J
EM: keskinen@ppd.nrl.navy.mil
AF: Naval Research Laboratory, 4225 Overlook Ave, S.W., Code 6790, Washington, DC 20375 United States
AU: Rich, F
AF: Air Force Research Lab, AFRL/VSBX, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AB: 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.
DE: 2411 Electric fields (2712)
DE: 2439 Ionospheric irregularities
DE: 2471 Plasma waves and instabilities
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting