News Excerpt:

The study of ionosphere variability over Bharati station in Antarctica reveals strong diurnal patterns even during polar days and nights.

About Ionosphere:

• It is part of Earth’s upper atmosphere, between 80 and about 600 km, where Extreme UltraViolet (EUV) and x-ray solar radiation ionize the atoms and molecules, thus creating a layer of electrons.
• Earth's upper ionosphere, particularly in high latitude regions like the polar cap and auroral oval, is closely linked to the magnetosphere, acting as a major sink for solar-terrestrial energy transfer processes and various magnetospheric and space weather events.
• The polar ionosphere is more variable and dynamic, resulting in unique characteristics such as strong plasma convention, particle precipitation, and joule heating.
• Solar wind and magnetospheric plasma enter the polar atmosphere along magnetic field lines, forming an important ionization source.
• The precipitation of these particles also produces aurorae and airglow.
• Polar ionospheric observations are crucial due to their sensitivity to space weather conditions.
• High latitude ionosphere experiences stronger irregularities and scintillation, which impact satellite-based communication and navigation systems.
• Few studies have been conducted using ground-based GPS receivers and in-situ measurements from CHAMP, DMSP satellites, and SuperDARN radar, with limited focus on short-term analysis or response during space weather events.

Total Electron Content (TEC):

• It is a crucial ionospheric parameter representing the electron density along the path of a radio signal.
• It is highly variable with time, season, and location and exhibits significant variations with geomagnetic activity.
• TEC fluctuations and gradients affect phase ambiguity resolution, increase undetected cycle slips, and loss of signal lock, causing severe amplitude fading and strong phase scintillations.
• These issues affect GPS navigational systems and satellite communication reliability.
• To use TEC as a parameter for diagnosing and forecasting ionospheric delay and navigation errors, the morphology of TEC behaviour must be modelled under quiet geomagnetic conditions.
• Therefore, developing a better understanding of TEC and its impact on scintillation and GPS performance is essential.

Key findings of the study:

• The Indian Institute of Geomagnetism (IIG) has examined the long-term seasonal ionospheric observations at station Bharati between 2010 and 2022, with solar activity following the Sun’s 11-year cycle.
  • Indian Institute of Geomagnetism (IIG) is an autonomous body of the Department of Science and Technology (DST).
• The study found a substantial seasonal variation with maximum total electron count (TEC) in equinoctial months, followed by the summer and winter.
• It was observed that though there was no sunlight incidence throughout the day in winter months (polar nights) at Bharati station, a diurnal pattern was observed with peak ionospheric density near local noon.
• The day-night ionospheric density variations were observed regardless of 24 hours of sunlight in summer and complete darkness in winter.
• The scientists attributed the peak ionization to particle precipitation and transportation of convectional plasma from high latitudes.
• Also, the maximum ionospheric density in the summer months, where 24 hours of sunlight is present (polar days), was about twice that of polar nights in the Bharati region.
• Significance of the study:
  • Such long-term studies can help understand the effects of the ionosphere on satellite-based navigation and communication systems and mitigate them.