|
|
 |
|
|
Ann. Geophys., 21, 1141-1151, 2003
www.ann-geophys.net/21/1141/2003/
© European Geosciences Union 2003
Ionosphere dynamics over Europe and western Asia during magnetospheric substorms 1998–99
D. V. Blagoveshchensky1, O. A. Maltseva2, and A. S. Rodger3
1University of Aerospace Instrumentation, St. Petersburg, 190000, Russia
2Institute of Physics, Rostov University, Rostov-on-Don, 344090, Russia
3British Antarctic Survey, Madingley Road, Cambridge, CB3 OET, UK
Abstract. The temporal and spatial
behaviour of the ionospheric parameters foF2 and h'F during isolated
substorms are examined using data from ionospheric stations distributed across
Europe and western Asia. The main purpose is finding the forerunners of the
substorm disturbances and a possible prediction of these disturbances. During
the period from March 1998 to March 1999, 41 isolated substorms with
intensities I = 60 - 400 nT were identified and studied. The study separated
occasions when the local magnetometers were affected by the eastward electrojet
(positive substorms) from those influenced by the westward electrojet (negative
substorms). The deviations of the ionospheric parameters from their monthly
medians (DfoF2 and Dh'F)
have been used to determine the variations through the substorm. Substorm
effects occurred simultaneously (< 1 h) across the entire observatory
network. For negative substorms, DfoF2-values
increase > 6 h before substorm onset, To, reaching a maximum 2–3
h before To. A second maximum occurs 1–2 h after the end of the
substorm. The Dh'F values 3–4 h before To
have a small minimum but then increase to a maximum at To. There is
a second maximum at the end of the expansion phase before dh'F
drops to a minimum 2–3 h after ending the expansion phase. For positive
substorms, the timing of the first maximum of the dfoF2
and dh'F values depends on the substorm
length – if it is longer, the position is closer to To. The
effects on the ionosphere are significant: DfoF2
and Dh'F reach 2–3 MHz (dfoF2
= 50–70% from median value) and 50–70 km (D
h'F = 20–30% from median value), respectively. Regular patterns of occurrence
ahead of the first substorm signature on the magnetometer offer an excellent
possibility to improve short-term forecasting of radio wave propagation
conditions.
Key words. Ionosphere (ionospheric
disturbances) – Magnetospheric physics (storms and substorms) Radio science (ionospheric
physics)
Full Article in PDF (283 KB) |
|
|
