Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation.

Unlike the nightside aurora, which is controlled mainly by magnetic field reconnection in the magnetotail, the dayside aurora is closely associated with magnetic field merging at the dayside magnetopause. About two decades ago, it was discovered that the aurora is also controlled by solar insolation. Because the finding was based on data acquired mainly in the Northern Hemisphere, an outstanding question is if the auroral solar insolation effect also exists in the Southern Hemisphere. The present study addresses this question by studying dayside auroras from both hemispheres. We analyze 6 years' worth of Earth disk emissions at far ultraviolet wavelengths acquired by the Global UltraViolet Imager on-board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite from 2002 to 2007. It is found that the solar insolation effect also exists in the Southern Hemisphere. In essence, the energy flux deposited as electron precipitation, is larger when the polar hemisphere is sunlit and is smaller when the polar hemisphere is dark. Because auroras are produced mainly by electron precipitation and because electrons are the main current carrier, this north-south asymmetry is consistent with the previous finding that larger (smaller) field-aligned currents are flowing out of the sunlit (dark) hemisphere. This trend is independent of the solar wind driving, suggesting that it is an effect associated with solar insolation. A small north-south asymmetry in the dayside auroral energy flux was identified. We discuss the asymmetry in the context of magnetospheric current and voltage generators.

North-South Asymmetry in the Geographic Location of Auroral Substorms correlated with Ionospheric Effects.

Energetic particles of magnetospheric origin constantly strike the Earth's upper atmosphere in the polar regions, producing optical emissions known as the aurora. The most spectacular auroral displays are associated with recurrent events called magnetospheric substorms (aka auroral substorms). Substorms are initiated in the nightside magnetosphere on closed magnetic field lines. As a consequence, it is generally thought that auroral substorms should occur in both hemispheres on the same field line (i.e., magnetically conjugated). However, such a hypothesis has not been verified statistically. Here, by analyzing 2659 auroral substorms acquired by the Ultraviolet Imager on board the NASA satellite "Polar", we have discovered surprising evidence that the averaged location for substorm onsets is not conjugate but shows a geographic preference that cannot be easily explained by current substorm theories. In the Northern Hemisphere (NH) the auroral substorms occur most frequently in Churchill, Canada (~90°W) and Khatanga, Siberia (~100°E), up to three times as often as in Iceland (~22°W). In the Southern Hemisphere (SH), substorms occur more frequently over a location in the Antarctic ocean (~120°E), up to ~4 times more than over the Antarctic Continent. Such a large difference in the longitudinal distribution of north and south onset defies the common belief that substorms in the NH and SH should be magnetically conjugated. A further analysis indicates that these substorm events occurred more frequently when more of the ionosphere was dark. These geographic areas also coincide with regions where the Earth's magnetic field is largest. These facts suggest that auroral substorms occur more frequently, and perhaps more intensely, when the ionospheric conductivity is lower. With much of the magnetotail energy coming from the solar wind through merging of the interplanetary and Earth's magnetic field, it is generally thought that the occurrence of substorms is externally controlled by the solar wind and plasma instability in the magnetotail. The present study results provide a strong argument that the ionosphere plays a more active role in the occurrence of substorms.

Efficacy of leisure intervention groups in rehabilitation of people with an acquired brain injury.

PURPOSE: To determine whether participation in a week-long residential leisure intervention program targeting individuals with an acquired brain injury (ABI) improved the leisure satisfaction, self-esteem and quality of life (QOL) of participants. The program included leisure awareness, leisure resources, social interaction skills and leisure activity skills. METHOD: Using a pre- and post-intervention design leisure satisfaction, self-esteem and QOL were assessed prior to, immediately following and at three months post program. Data were analyzed using Wilcoxon signed-rank tests. RESULTS: Participants were eight men and four women aged between 19 and 49 years who were recent clients of a rural Brain Injury Rehabilitation Service. The majority (7/12) had acquired their ABI more than two years previously, and for most (10/12) the cause was trauma. Program participants showed clinically important and statistically significant improvements in leisure satisfaction (p = 0.002), self-esteem (p = 0.03) and QOL (p = 0.02 to 0.008 for four domains of the World Health Organisation Quality of Life - Bref scale) three months post program. CONCLUSION: Adults with an ABI participating in leisure education programs can experience improvements in leisure satisfaction, self-esteem and QOL following the program. The findings suggest that active leisure intervention programs should be included in the ongoing rehabilitative care of adults with an ABI. Implications for Rehabilitation Leisure participation, leisure satisfaction and social integration can be seriously compromised following an acquired brain injury (ABI). Engagement in leisure activities has positive effects on physical and mental health and is increasingly recognised as an important determinant of quality of life (QOL) for people with ABI. Participation in a short-term intensive leisure intervention program can improve leisure satisfaction, self-esteem and QOL. Active leisure intervention programs should be included in the ongoing rehabilitation and reintegration of adults with ABI.