Overshielding event of 28–29 July 2000

On 29 July 2000, IMAGE EUV observed a shoulder‐like bulge on the plasmapause. Goldstein et al. [2002] showed that plasmaspheric shoulders may be caused by a pre‐dawn concentration of eastward overshielding electric (E) field triggered by a decrease in magnetospheric convection. A simulation by the Magnetospheric Specification Model (MSM) captures the shoulder formation, reproducing its approximate size and location. ROCSAT‐1 ion drift meter data are consistent with the strength, time development and local‐time variation of the MSM eastward penetration E‐field (and associated radial flows) during the shoulder formation on 28 July.