Ionosphere dynamics over Europe and western Asia during magnetospheric substorms 1998–99

• Main Authors: D. V. Blagoveshchensky, O. A. Maltseva, A. S. Rodger
• Format: Article
• Language: English
• Published: Copernicus Publications 2003-05-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/21/1141/2003/angeo-21-1141-2003.pdf

The temporal and spatial behaviour of the ionospheric parameters <i>f</i>oF2 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 (<i><font face="Symbol">D</font>f</i>oF2 and <i><font face="Symbol">D</font></i>h'F) have been used to determine the variations through the substorm. Substorm effects occurred simultaneously (&lt; 1 h) across the entire observatory network. For negative substorms, <i><font face="Symbol">D</font>f</i>oF2-values increase &gt; 6 h before substorm onset, T_o, reaching a maximum 2–3 h before T_o. A second maximum occurs 1–2 h after the end of the substorm. The <i><font face="Symbol">D</font></i>h'F values 3–4 h before To have a small minimum but then increase to a maximum at T_o. There is a second maximum at the end of the expansion phase before <font face="Symbol"><i>d</i></font>h'F drops to a minimum 2–3 h after ending the expansion phase. For positive substorms, the timing of the first maximum of the <i><font face="Symbol">d</font>f</i>oF2 and <font face="Symbol"><i>d</i></font>h'F values depends on the substorm length – if it is longer, the position is closer to T_o. The effects on the ionosphere are significant: <i><font face="Symbol">D</font>f</i>oF2 and <i><font face="Symbol">D</font></i>h'F reach 2–3 MHz (<i><font face="Symbol">d</font>f</i>oF2 = 50–70% from median value) and 50–70 km (<i><font face="Symbol">D</font></i> 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.<br><br><b>Key words. </b>Ionosphere (ionospheric disturbances) – Magnetospheric physics (storms and substorms) Radio science (ionospheric physics)