Prompt penetration (PP) and ionospheric disturbance dynamo (Ddyn) are two expressions of the disturbed electric field developed during a geomagnetic storm in the Earth's ionosphere. Earlier investigations treated these two processes independently over longitudinal separation beyond 20°. In the present study, we investigate the conjunction of these phenomena on equatorial electrojet at 20° longitude separations using daytime magnetic field data from three equatorial sites viz., Minicoy, Vencode, and Campbell Bay and three low‐latitude sites viz., Alibag, Hyderabad, and Nabagram, located within 20° longitude over Indian region, during three intense storms (Dst <− 150 nT). We propose a statistical method to identify PP signatures from large data set. In addition, we distinguish the signatures of PP and Ddyn during early recovery phase of intense storms and compute pure Ddyn signature in the late recovery phase. It is seen that the effect of PP is similar at the three equatorial sites for each storm. We find that signatures of Ddyn are amplified at Minicoy and Vencode compared to Campbell Bay, and their magnitude decreases toward low‐latitude stations, also reflected in the current vector patterns. Our investigations of intense geomagnetic storms show that PP effect dominates the main phase, followed by a combined effect of PP and Ddyn in the early recovery phase. Eventually the Ddyn signature dominates in the late recovery phase with decreasing amplitudes of Ddyn with increasing time. Such investigations can provide new information about variations in ionospheric parameters.

One second measurements of the geomagnetic field variations, which meet INTERMAGNET quality and transmission specifications, require very special conditions to be maintained at the observatories over sustained periods of time, which pose serious challenges for the operators, particularly when infrastructural and environmental conditions are far from ideal. This work presents the progressive steps, which led to the successful setup of such measurements at the new magnetic observatory of the Council of Scientific and Industrial Research (CSIR)-National Geophysical Research Institute (NGRI) in the Choutuppal (CPL) campus, Hyderabad (HYB), India. The 1 s magnetic measurements in trial mode commenced in 2015 using the newly developed observatory-grade 1 s fluxgate magnetometer, GEOMAG-02MO, from Research Centre GEOMAGNET (GM), Ukraine, and the Overhauser proton precession magnetometer, GSM-90F1, along with the data acquisition system, Magrec-4B from Mingeo, Hungary. Iterative tuning of the setup led to the generation of good quality data from 2016 onward. The processes of commissioning this setup in low-latitude conditions, with the aim of producing 1 s definitive data, and the characteristics of the data from this new instrument are presented here.

Continuous time series data from geomagnetic observatories are increasingly contaminated by anthropogenic noise related to developing socio-economic activities. More and more sophisticated techniques of data processing are used to eliminate this noise; nonetheless, some of it cannot be removed. The main sources of noise in the Hyderabad (HYB) data are vehicular traffic, power lines and a power station, 500 m to 1 km away. During the nationwide COVID-19 pandemic lockdown from 24 March to 17 May 2020, both road and metro rail traffic came to a complete halt. The data from this time interval give us an opportunity to evaluate the effects of the absence of traffic-generated noise sources. We found noticeable differences in the noise levels present in vector and scalar variation data, due to the vehicular noise observed before and during the lockdown periods. Noise spectrum estimates quantify the reduction in the noise levels during this period. We also noticed decreased scatter in absolute values of the H (horizontal), D (declination), Z (vertical) and I (inclination) components of the geomagnetic field during lockdown. The details of increased data quality in the absence of traffic-generated noise sources are discussed.

The characteristics of longitudinal variability of equatorial electrojet (EEJ) and counter electrojet (CEJ), presented in this study, are based on concurrent observations from a hitherto unsampled region of the world to examine the (1) degree of correlation between hourly means and monthly averaged hourly means of ground observations with equatorial electrojet climatological model (EEJM-2.0), (2) day-to-day longitudinal variability of EEJ strength between the pairs of sites, and (3) longitudinal variability in occurrences of counter electrojet. The analyses are based on the data obtained from an observatory and three new remote sites in the northern Indian Ocean at a longitudinal separation of approximately 15°: Hyderabad (HYB) and Vencode (VEN) at 77° E and Port Blair (PBR) and Campbell Bay (CBY) at 93° E, for a period of 4 months during Lloyd's D-season (November 2011 to February 2012) and comparison with the EEJM-2.0 based on CHAMP satellite data.