Variation of ionospheric plasma density during the annular solar eclipse on December 26, 2019

The annular solar eclipse of the previous decade that occurred on December 26, 2019, was mostly visible from most Asian countries, including India. In this manuscript, we present the variation of ionospheric plasma density profiles at different heights during the eclipse and non-eclipse days. We use both the ground- and space-based instruments to study the depletion in the electron density profile in the ionospheric D and F layers. We use the International GNSS Service (IGS)/Global Positioning System (GPS) stations and Swarm satellites outcomes to compute ionospheric Total Electron Content (TEC). We choose the IGS stations either on the path of the annularity or in the close vicinity of the annularity belt. For the first kind, we choose two IGS stations, GUUG in Guam island near the Western Pacific and CNMR in the Northern Mariana islands. We choose two Indian stations, IISC in Bangalore and HYDE in Hyderabad, that are close to the annularity belt. We observe similar to 20-40% depletion in the diurnal profile of TEC, as estimated from the IGS stations. This depletion is validated by a NovAtel GPS station-6 instrument situated at Hyderabad. Significant depletion in the spatio-temporal profile of TEC and electron density profile as computed from Swarm satellite data. The depletion in TEC is also validated by NASA's CDAWEB archive using Global Ionospheric Map (GIM). We try to estimate the TEC in the F layer and the electron density in the D layer using a numerical model. We compute the solar obscuration percentage by the geometrical configuration of the Sun and Moon. For TEC we use the solar irradiation model and calculate the delay of the maximum depletion compared to the maximum obscuration. To investigate the effects of the eclipse at the lower ionospheric heights (68-88 km), we use the GPI ion-chemistry model and observe depletion in the electron density profiles of around similar to 58-73% for all the locations. We observe that the time between the maximum depletion in the electron density and the maximum obscuration decreases with increasing height, and it gets the minimum value at an altitude of 84 km. All methods give consistent outcomes with depletion of plasma density that corroborates the effects of the solar eclipse on the Earth's ionosphere.