Simultaneous observations of magnetopause flux transfer events and of their associated signatures at ionospheric altitudes

first_imgAn extensive variety of instruments, including Geotail, DMSP F11, SuperDARN, and IMP-8, were monitoring the dayside magnetosphere and ionosphere between 14:00 and 18:00 UT on 18 January 1999. The location of the instruments provided an excellent opportunity to study in detail the direct coupling between the solar wind, the magnetosphere, and the ionosphere. Flux transfer events were observed by Geotail near the magnetopause in the dawn side magnetosheath at about 4 magnetic local time during exclusively northward interplanetary magnetic field conditions. Excellent coverage of the entire dayside high-latitude ionosphere was achieved by the Northern Hemisphere SuperDARN radars. On the large scale, temporally and spatially, the dayside magnetosphere convection remained directly driven by the interplanetary magnetic field, despite the highly variable interplanetary magnetic field conditions, including long periods of northward field. The SuperDARN radars in the dawn sector also measured small-scale temporally varying convection velocities, which are indicative of flux transfer event activity, in the vicinity of the magnetic footprint of Geotail. DMSP F11 in the Southern Hemisphere measured typical cusp precipitation simultaneously with and magnetically conjugate to a single flux transfer event signature detected by Geotail. A study of the characteristics of the DMSP ion spectrogram revealed that the source plasma from the reconnection site originated downstream of the subsolar point. Detailed analyses of locally optimised coordinate Systems for individual flux transfer events at Geotail are consistent with a series of flux tubes protruding from the magnetopause, and originating from a high-latitude reconnection site in the Southern Hemisphere. This high-latitude reconnection site agrees with plasma injected away from the subsolar point. This is the first simultaneous and independent determination from ionospheric and space-based data of the location of magnetic reconnection.last_img read more

Forecasters eying two tropical systems

first_img Sharing is caring! Atlantic tropical cyclone activity. NHC/NOAA graphicMIAMI, USA — According to the national Hurricane Center in Miami, an area of low pressure over the western Caribbean Sea is centered about 170 miles east of the coast of Nicaragua. The associated shower activity has become better organized and there is a likelihood that a tropical depression will form during the weekend.Little motion is anticipated in the short term but a slow northward drift should begin on Sunday. This system has a high chance — 60 percent — of becoming a tropical cyclone during the next 48 hours.Another broad area of low pressure has formed about 350 miles east-southeast of Trinidad in the southern Windward Islands. Cloudiness and showers associated with this low have become a little better organized and the potential for development has increased. This system has a low chance — 20 percent — of becoming a tropical cyclone during the next 48 hours.Regardless of development, cloudiness and heavy rains will likely spread over northern Venezuela and the southern Windward Islands during the next few days.By Caribbean News Now contributor Share 5 Views   no discussions Tweetcenter_img Share LocalNews Forecasters eying two tropical systems by: – October 22, 2011 Sharelast_img read more