Ionospheric and geomagnetic response to the total solar eclipse on 1 August 2008 over Northern Hemisphere

[1] The ionospheric and geomagnetic response to the total eclipse of the Sun on 1 August 2008 over Northern Hemisphere has been examined using 14 GPS, three ISR radar, and three magnetometer ground-based stations. Three different approaches were employed to examine the TEC depletion occurrence at the GPS stations: determination of the TEC depletion parameters during the solar eclipse with respect the quiet day TEC variations, comparison of the total TEC (Sigma TEC) during the solar eclipse period with respect to quiet day TEC measurements for the same period of time, and determination of the average daily TEC obtained from eight GPS stations and compares the values with the average quiet day TEC at these stations. The GPS observations indicate obvious TEC depression occurrence at all stations with the values was varying between 11% and 40%. The observations show that TEC depression at most GPS stations started on the neck of the first contact of the eclipse followed by deeper negative deviation while the area of optical disk obscured getting larger. Periods of TEC depletion were also observed before the first contact time of solar eclipse and after the fourth contact of solar eclipse due to earlier and later obscuration of the solar corona before and after the eclipse observation time. The incoherent scatter radar observations at Svalbard, Tromso, and Sondrestrom also show clear depletion occurrence in electron density, electron temperature, ion velocity, and plasma cutoff frequency during the solar eclipse passage at these stations. Radar measurements show obvious difference in the ionospheric response between the E and F layers of ionosphere and between ion and electron temperature in the F layer. The geomagnetic field response to the solar eclipse at CBB, RESO, and NUR stations was examined by using two different techniques, first by comparing the daily variations of geomagnetic field during the eclipse period with the variations on the day before and day after the eclipse, and second by determination the Delta magnetic field with respect to the average quiet geomagnetic field. The results show obvious decrease in the total field, X and Z components of geomagnetic field and obvious increase in the Y component at both CBB and RESO stations. The depletion in X, Z, and total field was in the range between 15 and 28 nT while the increase in the Y component was 18-22 nT.