The Low-Latitude Plasma Irregularities after Sunrise from Multiple Observations in Both Hemispheres during the Recovery Phase of a Storm

The daytime plasma density disturbances in the low-latitude ionosphere, referred to as plasma irregularities, mainly occur during the nighttime and are an unusual phenomenon. Based on the observations from multiple low Earth orbiting (LEO) satellites, e.g., the Defense Meteorological Satellite Program (DMSP) F13 and F15, the first Satellite of the Republic of China (ROCSAT-1), the Gravity Recovery and the Climate Experiment (GRACE), and Challenging Mini-satellite Payload (CHAMP) satellites, as well as the ground-based Global Positioning System (GPS) receivers, we report a special event of low-latitude plasma irregularities that were observed after sunrise in the Pacific longitudes on 18 August, 2003, following a moderate geomagnetic storm. Observations from three ground-based GPS stations in both hemispheres showed remarkable total electron content (TEC) disturbances during 20:00 to 21:00 UT (around local sunrise), agreeing well with the in situ plasma density irregularities recorded by the nearby flying LEO satellites. The plasma irregularities observed by these LEO satellites showed quite different depletion intensities at different altitudes. We suggest that the plasma irregularities were freshly generated near sunrise hours due to the disturbance of the dynamo electric field (DDEF), evolving into the post-sunrise and morning sector, but were not the remnant of the plasma irregularities generated during the previous nighttime.