Magnetic and Ionospheric Observations During the October 24, 1995 Total Solar Eclipse in Vietnam


The track of the Moon¡¦s shadow during the Total Solar Eclipse of October 24, 1995 passed parallel to the magnetic Equator in the Vietnam sector. This fact together with its lengthy 2-minute duration at around noon time of totality provided an ideal opportunity to study the solar eclipse effect both on the global Sq and electrojet currents.

In Vietnam, the recording of the magnetic variations in order to study the Equatorial Electrojet's effect has been carried out at 4 magnetic stations since 1987. These stations are situated in the region with the magnetic inclination (I) between 0°N and 34°5N. During the period of the Total Solar Eclipse of October 24, 1995, two new temporary magnetic stations were instaled and operated for one week at Phanthiet and Baoloc, two places directly lying under the belt of the Total Solar Eclipse.

The eclipse effect on the H component was observed only in the region of the magnetic Equator (inside the range of 400 km from the magnetic Equator): the H component started to decrease immediately with the beginning of the solar eclipse at 09.33 + 09.38 LT; at the moment of the maximum Sq(H) for October 1995 the delta H with reference to the night time base value decreased to 76-82% of the value of the normal Sq .

Ionospheric observations were carried out in Hanoi (with obscuration 0,78) by the Ionosondes IPS-71 made by KEL Aerospace Pty. Ltd. ( Australia). The analyses of ionograms showed that at the beginning of the local solar eclipse, foFl, with a slightly larger value than that of the monthly median , started to gradually decrease following the decrease in local solar radiation to its minimum value around the time of local maximum occultation. After the end of the local eclipse, foFl returned to its monthly median value.

These results suggest that the normal electric field in the Sq band was left unaffected , and the eclipse effect on the geomagnetism in the region of the magnetic Equator was due to the decrease in the ionization in the Equatorial Electrojet Current.

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