Low latitude ionospheric TEC response to the solar flares during the peak of solar cycle 24 See

We describe the newly discovered response of differential vertical total electron content (DVTEC) in the low-equatorial latitude ionosphere to the solar flares during the peak of solar cycle 24 i.e., the year 2014. GPS TEC data for the existing investigation has been acquired from the international GNSS services network station in Bangalore, India (geomagnetic latitude 4.58oN). For the year 2014, we inspected five X-class solar flares, forty-nine M-class solar flares, and three hundred nin...

Kinetic study of ion acoustic waves in Venusian ionosphere See

Kinetic dispersion of the ion acoustic waves has been explored for an unmagnetized five component plasma system comprising of Venusian protons, Venusian oxygen ions, Venusian electrons, solar wind protons, and kappa electrons. The solar wind protons and electrons are assumed to be streaming along the ambient magnetic field. The plasma parameters for this study have been obtained from Lundin et al. [Icarus 215(2), 751–758 (2011)] for the dawn dusk meridian of Venus Express with the data fro...

Quasi-two-day wave amplification through interhemispheric coupling during the 2010 austral summer See

A quasi-two-day wave (QTDW) event during January-February 2010 is investigated using the MERRA-2 reanalysis dataset. MERRA-2 data reveals the growth of the QTDW westward propagating wavenumber 3 preceded by a weak westward wavenumber 4. The diagnostic analysis suggests that the QTDW growth near tropical stratopause is mainly supported by barotropic (BT) instability in the presence of the summer easterly jet. BT instability during this event is suggested to be linked to the planetary wave b...

Intense (SYM - H 6<-100 nT ) geomagnetic storms induced by planar magnetic structures in co-rotating interaction regions See

Generally, Co-rotating Interaction Region (CIR) induced geomagnetic storms are weak to moderate in magnitude. Moreover, CIRs can also drive intense storms when they are coupled with an ICME or other interplanetary structures. Here, we investigated all intense (SYM H 6 100 nT ) geomagnetic storms caused by CIRs from the years 1996 to 2016. We found 12 intense storms that were solely caused by CIRs, i.e., without any component of ICME. We observed the evolution of a planar magnetic struct...

Understanding Quiet and Storm Time EMIC Waves - 2 Van Allen Probes Results See

Geomagnetic indices have been used as a proxy for studying electromagnetic ion cyclotron (EMIC) wave occurrences under di erent geomagnetic conditions. However, the drivers of EMIC waves are di erent during non-storm, storm time and during individual storm phases. Using 7 years of data from the twin Van Allen Probes, we demonstrate that the occurrence probability of EMIC waves are not well captured by a speci c geomagnetic activity index alone, but is rather well manifested by considering ...

Anisotropy of the near-field coseismic ionospheric perturbation amplitudes reflecting the source process: the 2023 February Turkey earthquakes See

The East Anatolian Fault in southern Turkey ruptured on 6 February 2023, causing a Mw 7.8 earthquake (EQ1), one of the largest strike-slip events recorded on land. ∼9 hr later, earthquake of Mw 7.7 (EQ2) occurred to the north of EQ1. We investigate here near-field coseismic ionospheric perturbations (CIP) caused by acoustic waves (AWs) excited by coseismic vertical crustal movements. We find that observed CIP periods were somewhat longer for EQ1 than EQ2. EQ1 also showed azimuthal depende...

Interplanetary shocks between 0.3 and 1.0 au: Helios 1 and 2 Observations See

The Helios 1 (H1) and Helios 2 (H2) spacecraft measured the solar winds at a distance between ∼0.3 and 1.0 au from the Sun. With increasing heliocentric distance (rh), the plasma speed is found to increase at ∼34–40 km s−1 au−1 and the density exhibits a sharper fall (rh- 2) compared to the magnetic field magnitude (r - h 1.5) and the temperature (rh- 0.8). Using all available solar wind plasma and magnetic field measurements, we identified 68 and 39 fast interplanetary shocks encounte...

Kinetic Alfvén waves excited by multiple free energy sources in the magnetotail See

The generation of kinetic Alfvén waves (KAWs) is investigated through a three-component theoretical model incorporating ion beam and velocity shear as the sources of free energy in a non-Maxwellian κ-distributed plasmas. The model considers Maxwellian distributed background ions, drifting-Maxwellian beam ions, and κ-electrons as its constituent species. It is found that the combination of either positive velocity shear with counter-streaming beam ions or parallel streaming beam ions with ...

Electrostatic solitary waves in the Venusian ionosphere pervaded by the solar wind: a theoretical perspective See

Electrostatic solitary waves (ESWs) in the Venusian ionosphere that are impinged by the solar wind are investigated using a homogeneous, collisionless, and magnetized multicomponent plasma consisting of Venusian H+ and O+ ions, Maxwellian Venusian electrons and streaming solar wind protons, and suprathermal electrons following κ − distribution. The model supports the propagation of positive potential slow O+ and H+ ion-acoustic solitons. The evolution and properties of the solitons occurr...

Equatorial plasma bubble association with lower atmospheric gravity waves – Further evidences See

Space based radio wave communication and navigation has become need of the society. Atmospheric (thermospheric-ionospheric) processes, such as Equatorial Plasma Bubbles (EPBs), affect the radio waves propagating through this region, causing heavy perturbations on signals received at ground. This paper investigates the causative mechanism of EPB through the ground based remotely sensed imaging observations of O (1S) 557.7 nm and O (1D) 630.0 nm emissions emanating from the upper mesosphere ...

A mechanism for large-amplitude parallel electrostatic waves observed at the Magnetopause See

Large-amplitude electrostatic waves propagating parallel to the background magnetic field have been observed at the Earth’s magnetopause by the Magnetospheric Multiscale (MMS) spacecraft. These waves are observed in the region where there is an intermixing of magnetosheath and magnetospheric plasmas. The plasma in the intermixing region is modeled as a five-component plasma consisting of three types of electrons, namely, two counterstreaming hot electron beams and cold electrons, and two...

Day-to-day quantification of changes in global lightning activity based on Schumann resonances See

The importance of lightning has long been recognized from the point of view of climate-related phenomena. However, the detailed investigation of lightning on global scales is currently hindered by the incomplete and spatially uneven detection efficiency of ground-based global lightning detection networks and by the restricted spatio-temporal coverage of satellite observations. We are developing different methods for investigating global lightning activity based on Schumann resonance (SR) ...

The possible cause of most intense geomagnetic superstorm of the 21st century on 20 November 2003 See

An extreme geomagnetic storm has the potential to affect various technologies and activities in space and on the ground, e.g., power grids, oil and gas industries, communications, ground transportation, satellite infrastructure, global navigation satellite systems, aviation, etc. Therefore, it is considered a major source of risk by various governmental agencies and corporations at the international level. All notable space weather events (superstorms) are caused by interplanetary corona...

Spatially heterogeneous lithospheric architecture of the Cambay rift basin and adjoining Aravalli-Delhi Fold Belt, western India – A synthesis of magnetotelluric results See

The Cambay rift basin (CRB) evolution has been associated with separation of the Indian continent from the African continent and subsequent interaction with the R´eunion mantle plume, which resulted in significant alternations in the regional lithospheric structure of western India, more prominently in the CRB due to its proximity to the plume track. In our continued effort to delineate the lithospheric structure of the CRB and adjoining regions, we acquired magnetotelluric (MT) data at 3...

Enhanced gravity wave activity in the mesosphere lower thermosphere region over Tirunelveli as a response to tropospheric convective event See

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–...

Machine learning approach for detection of plasma depletions from TEC See

Ionospheric delay is of concern for trans-ionospheric radio communication, especially for the navigation systems relying on these satellite signals. Most of the ionospheric delays are estimated to a degree of first-order using dual frequency global navigation satellite system (GNSS) receivers except during irregularities and equatorial plasma bubbles. The plasma bubbles are observed as a decrease or reduction in total electron content (TEC) as a result of large-scale irregularities that ar...

Performance of the CORDEX-SA regional climate models in simulating summer monsoon rainfall and future projections over East India See

—The Indian summer monsoon rainfall (ISMR, June– September) is an important factor in agricultural planning and the Indian economy. The ISMR over East India (EI: ChhattisgarhBihar-Jharkhand-Odisha) is particularly significant, and it can have an impact on the country’s average ISMR. The current study examined projected changes in ISMR over EI with two emission scenarios, RCP4.5 and RCP8.5, for near (2017–2040) and far-future (2041–2070) projections using a set of ten CORDEX-SA Regional ...

Studies on the variability of mean winds in the mesosphere and lower thermosphere region (MLT) over Kolhapur (16.8oN, 74.2oE) See

We present the study of mesospheric winds in the 78–98 km height range using observations by a partial reflection radar station (MF–radar) situated at Kolhapur (16.8° N, 74.2° E), India. The sequential wind profiles over the period of 2014–2019 obtained from this radar operated at 1.98 MHz are used for this study. To delineate the behaviour of the winds in the mesosphere and lower thermosphere (MLT) region, we use wind data providing horizontal wind velocities averaged for an hour. Detail...

Nonlinear electrostatic structures and stopbands in a three-component magnetosheath plasma See

Large amplitude parallel propagating electric field structures of nonlinear electron-acoustic waves are examined in an unmagnetized magnetosheath plasma. Based on the observations and simulations by Ergun et al. (2016), the plasma in the magnetosheath side of the ion diffusion layer is modeled by a 3-component adiabatic fluid dynamic plasma consisting of cold magnetospheric (MSP) electrons, magnetosheath electrons, and background ions. Using the Sagdeev pseudopotential technique, for the p...