The annual and longitudinal variations in plasmaspheric ion density

first_imgThis paper shows that at solar maximum, equatorial ion densities at L = 2.5 are substantially higher at American longitudes in the December months than in the June months. This arises because the configuration of the geomagnetic field causes a longitude-dependent asymmetry in ionospheric solar illumination at conjugate points that is greatest at American longitudes. For example, at −60°E geographic longitude the L = 2.5 field line has its foot point near 65° geographic latitude in the Southern Hemisphere but near 42° latitude in the Northern Hemisphere. We investigated the consequent effects on equatorial electron and ion densities by comparing ground-based observations of ULF field line eigenoscillations with in situ measurements of electron densities (from the CRRES and IMAGE spacecraft) and He+ densities (IMAGE) for L = 2.5 at solar maximum. Near −60°E longitude the electron and ion mass densities are about 1.5 and 2.2 times larger, respectively, in the December months than in the June months. Over the Asia-Pacific region there is little difference between summer and winter densities. Plasmaspheric empirical density models should be modified accordingly. By comparing the electron, helium, and mass densities, we estimate the annual variation in H+, He+, and O+ concentrations near −3°E longitude and −74°E longitude. In each case the He+ concentration is about 5% by number, but O+ concentrations are substantially higher at −3°E longitude compared with −74° E. We speculate that this may be related to enhanced ionospheric temperatures associated with the South Atlantic anomaly.last_img read more

Ellsworth swim team sweeps Washington Academy on Senior Night

first_imgELLSWORTH — The Ellsworth swim team closed out an excellent regular season Tuesday with a Senior Night sweep against the visiting Washington Academy Raiders at the Down East Family YMCA.The meet, which was postponed from Friday after bad weather prevented Washington Academy from traveling to Hancock County as scheduled that day, served as a final chance for the Eagles to tune up for the conference and state championship meets later this month. The Eagles’ won the boys’ matchup 118-38 and the girls’ matchup by a score of 116-30.On the boys’ side, Ellsworth won all but one race on the evening. Camden Holmes (200-yard freestyle and 100-yard backstroke) and Richie Matthews (50- and 100-yard freestyles) provided the Eagles with two individual event wins apiece. Matthews, a senior, was competing in his final home meet.Ellsworth also came close to winning every event on the girls’ side, falling just short in the 50-yard freestyle. Ellie Clarke (100 freestyle and 200 individual medley) and Caitlin MacPherson (100-yard breaststroke and 100-yard butterfly) each earned a pair of individual wins for the Eagles.This is placeholder textThis is placeholder textEllsworth will compete in the Penobscot Valley Conference championships this weekend at the University of Maine. The boys’ meet will be held at 6 p.m. Friday, Feb. 9, and the girls’ meet is scheduled to begin at 2 p.m. Saturday, Feb. 10.last_img read more