|
|
 |
|
|
Ann. Geophys., 23, 3473-3480, 2005
www.ann-geophys.net/23/3473/2005/
© European Geosciences Union 2005
Concurrent study of bottomside spread F and plasma bubble events in the equatorial ionosphere during solar maximum using digisonde and ROCSAT-1
C.-C. Lee1, S.-Y. Su2, and B. W. Reinisch3
1General Education Center, Ching-Yun University, Jhongli City, Taoyuan County, Taiwan
2Institute of Space Science and Center for Space and Remote Sensing Research, National Central University, Jhongli City, Taoyuan County, Taiwan
3Center for Atmospheric Research, University of Massachusetts Lowell, Massachusetts, USA
Abstract. Data from the Jicamarca digisonde and the ROCSAT-1 satellite are employed to
study the equatorial ionosphere on the west side of South America during
April 1999-March 2000 for the concurrent bottomside spread F (BSSF) and
plasma bubble events. This study, using digisonde and ROCSAT-1 concurrently,
is the first attempt to investigate the equatorial spread F. Results show
that BSSF and plasma bubble observations appear frequently respectively in the summer (January,
February, November, and December) and in the equinoctial (March, April,
September, and October) months, respectively, but are both rarely observed in the winter
(May-August) months. The upward drift velocity during the concurrent BSSF
and bubble observations has been determined to study the driving mechanism.
This analysis shows that large vertical drift velocities favor BSSF and
bubble formations in the equinoctial and summer months. Conversely, the
smaller upward velocities during the winter months cause fewer BSSF and
bubble occurrences. For the geomagnetic effect, the BSSF/bubble occurrence
decreases with an increasing Kp value in the equinoctial months, but no such
correlation is found for the summer and winter months. Moreover, the
anti-correlations between Kp and dh'F/dt are apparent in the equinoctial months,
but not in the summer and winter months. These results indicate that in the
equinoctial months the BSSF/bubble generations and the pre-reversal drift
velocity can be suppressed by geomagnetic activity, because the disturbance
dynamo effects could have decreased the eastward electric field near sunset.
However, BSSF and bubble occurrences may not be suppressed by the
geomagnetic activity in the summer and winter months.
Full Article in PDF (5536 KB) |
|
|
