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Fig. 1 | Earth, Planets and Space

Fig. 1

From: Comparison of volcanic explosions in Japan using impulsive ionospheric disturbances

Fig. 1

Ionospheric disturbance caused by continuous (Type 1 left) and explosive (Type 2 right) volcanic eruptions can be detected by differential ionospheric delays of microwave signals of two carrier frequencies (L1 and L2) from GNSS satellites. Strong continuous eruptions sometimes excite atmospheric modes and long-term oscillatory disturbances in ionosphere. For explosive eruptions, we often find short-term impulsive disturbances in ionosphere 8–10 min after eruptions, the time required for acoustic waves to reach the ionospheric F region. The acoustic wave makes electron density anomalies (pairs of positive and negative anomalies as shown with red and blue colors in the figure) on the southern side of the volcano (for northern hemisphere cases) due to interaction with geomagnetic field (blue arrow)

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