Coherent bipolar electric field structures with negative unipolar potentials are widely observed in space plasmas. These bipolar structures are often found to be ion Bernstein Greene Kruskal (BGK) modes or ion holes. Most theoretical models of ion holes assume them to be stationary with respect to the background plasma that follows either Maxwellian or kappa-type distribution. In this paper, we present a new theoretical model of ion holes where the structures are non-stationary, and electrons...

Intense, midnight-to-dawn sector, near-equatorial, chorus rising tones which cross frequencies of_0.5_ce have been analyzed to determine their structures and possible substructures. Upper 𝐴𝐴band (𝐴𝐴 ≥ 0.5𝑓𝑓ce ) chorus and “𝐴𝐴gap” (𝐴𝐴 ∼ 0.5𝑓𝑓ce ) chorus are examined in detail for the first time. It is found that upper band chorus and gap chorus are composed of the same structure as lower 𝐴𝐴 band (𝐴𝐴 ≤ 0.5𝑓𝑓ce ) chorus: they are composed of short-duration subelements, which ar...

During a weak geomagnetic storm (Ap = 15) on 24 December 2014, the penetration electric field perturbations over the Indian dip equatorial sector are found to be anomalous on a number of occasions during post-sunset hours. The event is anomalous as the magnitude and polarity of penetration electric fields do not obey the existing paradigm. The penetration electric field perturbations are investigated using the vertical drifts derived from the CADI (Canadian Advanced Digital Ionosonde) measure...

Shoreline changes have been monitored for the tropical West Coast of Maharashtra using the Survey of India (SOI) toposheet, Remote Sensing (RS) data, and its incorporation in the Geographical Information System (GIS) for the time period from 1980 to 2013. Indian Remote Sensing (IRS) Resource Sat (P6-R2) satellite data of 2013 year were geocoded using an image-to-image rectiBcation process with the help of permanent points on the ground. The registered satellite imageries were added in Arc GIS...

The strong quasi 2-day wave (Q2DW) event that occurred during January 2015 was studied by employing medium frequency and meteor radar observations of winds from three different locations at low latitudes with considerable longitudinal separation. The large-amplitude wave activity that occurred in mid-January is the focus of this study. Using the advantage offered by the longitudinal separation among the stations, the zonal structure of the Q2DW has been examined. The presence of a dominant we...

The study examined the pollution status of Takum town, Nigeria using environmental magnetic, geochemistry and geostatistics. The environmental magnetic approach included measurement of concentration, grain size and magnetic mineral dependent parameters. Magnetic susceptibility (χ), saturation and anhysteric remanent magnetizations were highly variable having values that ranged from 32.11–1118.57 × 10−8 m3kg−1, 95.03–1206.59 × 10−8 m3kg−1 and 199.87–16,002 × 10−5 Am2kg−1 respectively. These va...

The recent upgrade of Medium-Frequency (MF) wind radar at Tirunelveli (8.7⁰N, 77.8⁰E) has improved the height and time resolution of the wind measurements, which are utilized in the present study to examine high frequency (in periods 20–60 min) gravity waves (GW) in the mesosphere and lower thermosphere (MLT) region. We observe, in addition to the dominant wave activity during equinox months, dominant episodes of high-frequency GW activities in the meridional winds during the times 31 May–4 J...

The Precipitable Water Vapour (PWV) content associated with heavy precipitations can be estimated using the temporal variation of the Global Positioning System (GPS) derived Zenith Total Delay (ZTD). The ZTD and PWV were calculated using continuously observed GPS data for nine months (1 April to 31 December of 2018) that include the August 2018 catastrophic rainfall events in the state of Kerala, which is the gateway to the Indian summer monsoon located at southwest coast of India. The result...

Kinetic theory of low frequency electrostatic waves is carried out in the lunar wake plasma modelled by kappa electrons, kappa-beam electrons, Maxwell–Boltzmann distributed protons and doubly charged Helium ions. The present work is motivated by observation of electrostatic waves on the outbound side of the first lunar wake flyby of the mission Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) probe P1. The dispersion characteristics o...

Here, the impact of the 26 December 2019 solar eclipse on the equatorial and low latitude ionosphere has been investigated using ground and space-based observations over Indian and Southeast Asian longitudes. The high-resolution Ionosonde observations at Tirunelveli, GPS Total Electron Content (TEC) observations from a chain of GPS receivers along and across the eclipse path, TIMED-SABER, and Ionospheric Connection Explorer (ICON) satellites were utilized to investigate the eclipse-induced va...

Rise times of earthquake moment release influence the spectra of seismic waves. For example, slow fault movements in tsunami earthquakes excite larger tsunamis than expected from intensities of short-period seismic waves. Here we compare amplitudes of two different atmospheric waves, long-period internal gravity waves and short-period acoustic waves, excited by coseismic vertical crustal movements. We observe them as coseismic ionospheric disturbances by measuring ionospheric electrons using ...

The effect of power-law dust size distribution and dust number density on the low frequency hall current instabilities have been studied in and above the equatorial electrojet altitudes using a linear fluid model consisting of electrons, ions and dust particles. The dispersion relation includes electron and ion drift perpendicular to the equilibrium uniform electric and magnetic field, mass and pressure of the charged species and collision between charged and neutral particles. The effect of ...

Helical and chiral plasma structures are ubiquitous, especially in nuclear fusion devices and space plasmas. However, the spontaneous formation of helical structures has rarely been noticed in non-equilibrium cold plasma jets that have wide applications in biomedicine and material science. Recently the chiral plasma plume without any notable asymmetry has been discovered. Under the specific parameters of pulsed discharges, the plasma bullets that at the beginning propagated in the straight li...

We investigated the external magnetic potential due to solar forcing, with nine years of data during 2001-2009, covering the deep solar minimum (2006-2009), at two stations: one is in the polar cap -Vostok (78º27'S, 106º52’E; mag. lat 83ºS) and another is in the subauroral region - Maitri (70º45'S, 11º43'E: mag. lat 67ºS) in Antarctica. The significance of the work is associated with space weather prediction and its impact on planet Earth. We used Advance Composition Explorer (ACE) satellite ...

Space and upper atmospheric sciences group in the National Institute of Polar Research (NIPR) is now constructing an observation network for auroral phenomena along the coast of the Dronning Maud Land in the Antarctica including Japanese Syowa Station (SYO), and has developed a Unmanned Auroral Observation system (UAO), which is equipped with a 3-axis fluxgate magnetometer, all-sky auroral imager, GNSS/TEC receiver, and a data communication system using the Inmarsat satellite data link with a...

Various remote and in situ observations, along with several models, simulations, and kinetic studies, have been proposed in recent years, suggesting that the morphology of an interplanetary coronal mass ejection (ICME) magnetic cloud can vary from cylindrical, elliptical, toroidal, flattened, pancaked, etc. Recently, Raghav et al. proposed for the first time a unique morphological characteristic of an ICME magnetic cloud at 1 au that showed characteristics of a planar magnetic structure, ...

Space weather refers to conditions around a star, like our Sun, and its interplanetary space that may affect space- and ground-based assets as well as human life. Space weather can manifest as many different phenomena, often simultaneously, and can create complex and sometimes dangerous conditions. The study of space weather is inherently trans-disciplinary, including subfields of solar, magnetospheric, ionospheric, and atmospheric research communities, but benefiting from collaborations with...

The present work studies a severe smog event that occurred in Delhi (India) in 2017, targeting the characterization of PM2.5 and its deposition potential in human respiratory tract of different population groups in which the PM2.5 levels raised from 124.0 µg/m3 (pre-smog period) to 717.2 µg/m3 (during smog period). Higher concentration of elements such as C, N, O, Na, Mg, Al, Si, S, Fe, Cl, Ca, Ti, Cr, Pb, Fe, K, Cu, Cl, P, and F were observed during the smog along with dominant organi...

Spectral Resonance Structures (SRS) of Ionospheric Alfven Resonator (IAR) are investigated by analysing the magnetic field data of a high sampling frequency induction coil magnetometer, installed at a low latitude Indian station, Shillong(25.56◦N, 91.86◦E, dipoleL = 1.08) . One of the distinguishing features of IAR resonance structure observed at this latitude is the excitation of two spectral resonance structures simultaneously, one with a small frequency separation and the other with a ...