Superposed epoch analysis of mid-latitude ionospheric convection during disturbed periods with the SuperDARN Hokkaido radar

Details Superposed epoch analysis of mid-latitude ionospheric convection during disturbed periods with the SuperDARN Hokkaido radar Superposed epoch analysis of mid-latitude ionospheric convection during disturbed periods with the SuperDARN Hokkaido radar

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsa41b1854y&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #SA41B-1854

Physics

[2435] Ionosphere / Ionospheric Disturbances, [2437] Ionosphere / Ionospheric Dynamics, [2443] Ionosphere / Midlatitude Ionosphere, [2463] Ionosphere / Plasma Convection

Scientific paper

Characteristics of ionospheric convection in the mid-latitude and sub-auroral regions have been studied by various observation instruments and computer experiments in the last few decades. Presence of westward flows around midnight at mid-latitude has been extensively discussed. This flow can be generated by so-called disturbance dynamo mechanisms working at mid-latitudes (Blanc et al., JGR, 1980). We tested the disturbance dynamo theory by using ionospheric echo data obtained by the SuperDARN Hokkaido radar for 4.5 years. The SuperDARN Hokkaido radar has been measuring line-of-sight velocities of ionospheric irregularities, which can be regarded as line-of-sight velocities of ionospheric convection. The radar can monitor mid-latitude ionospheric convection (geomagnetic latitude: 40 to 60 degrees), which could not be monitored by using preexisting SuperDARN radars. We found the presence of westward flows around midnight at about 40 to 55 degrees geomagnetic latitude. The flows intensified with increasing geomagnetic activity. Kumar et al. (2010, JGR) reported, using the data from Digisonde drift measurements made at Bundoora (145.1 degrees E, 37.7 degrees S geographic, 49 degrees S magnetic), Australia, that the major storms cause the westward flow in the nighttime mid-latitude ionosphere for several tens of hours. Moreover, in order to understand the influence of disturbances dynamo effects at the mid-latitude region, it is necessary to study the geomagnetic latitudinal dependence. In our analysis, we found that the westward flow during of major disturbances (minimum Dst below -60nT) in the nighttime mid-latitude (geomagnetic latitude: 43 to 59 degrees) ionosphere lasted up to about 30 hrs after storm onset. The latitudinally extensive observations made by SuperDARN Hokkaido radar proved the presence of very remarkable disturbances dynamo effects in the vicinity of 45-deg geomagnetic latitude. We are also studying the influences of AL defined disturbances and Dst defined storms including weak storms on mid-latitude ionosphere convection observed by the Hokkaido radar. Detailed analysis results will be reported in the presentation.

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