Observations of a positive storm phase on September 10, 2005
Abstract |
<p>In this study, we present multi-instrument observations of a strong positive phase of ionospheric storm, which occurred on September 10, 2005 during a moderate geomagnetic storm with minimum <em>D</em><sub>st</sub>=-60\ nT and maximum <em>K</em><sub>p</sub>=6\textendash. The daytime electron density measured by the Millstone Hill incoherent scatter radar (42.6\textdegreeN, 288.5\textdegreeE) increased after 13\ UT (\~8\ LT) compared with that before the storm. This increase is observed throughout the daytime, lasts for about 9\ h, and covers <em>F</em>-region altitudes above \~230\ km. At the altitude of 300\ km, the maximum increase in <em>N</em><sub>e</sub> reaches a factor of 3 by 19:30\textendash20:00\ UT and is accompanied by a \~1000\ K decrease in electron temperature, a \~100\textendash150\ K increase in ion temperature, and a strong upward drift. Observations by Arecibo ISR (18.3\textdegreeN, 293.3\textdegreeE) reveal similar features, with the maximum increase in electron density reaching a factor of 2.5 at 21:30\ UT, i.e. 1.5\textendash2\ h later than over Millstone Hill. The GPS TEC data show that the increase in electron density observed at Millstone Hill and Arecibo is only a part of a global picture reflected in TEC. The increase in TEC reaches a factor of 2 and covers middle and low latitudes at 19\ UT. At later times this increase moves to lower latitudes. A combination of mechanisms were involved in generation of positive phase. The penetration electric field resulted in <em>N</em><sub>e</sub> enhancements at subauroral and middle latitudes, the TAD/TID played an important role at middle and lower latitudes, and increase in O/N<sub>2</sub> ratio could contribute to the observed positive phase at middle and lower latitudes. The results show the importance of an upward vertical drift at \~140\textendash250\ km altitude, which is observed for sustained period of time and assists in the convergence of ionization into the <em>F</em>-region.</p>
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Year of Publication |
2007
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Journal |
Journal of Atmospheric and Solar-Terrestrial Physics
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Volume |
69
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Number of Pages |
1253-1272
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Date Published |
07/2007
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ISSN Number |
13646826
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URL |
http://linkinghub.elsevier.com/retrieve/pii/S1364682607000727
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DOI |
10.1016/j.jastp.2006.09.011
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