Abstract. We study the impact of the geomagnetic storm of 7–9 September 2017 on the low- to mid-latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of two SYM-H minima with values of −146 and −115 nT on 8 September at 01:08 and 13:56 UT, respectively. The study is based on the analysis of data from the Global Positioning System (GPS) stations and magnetic observatories located at different longitudinal sectors corresponding to the Pacific, Asia, Africa and the Americas during the period 4–14 September 2017. The GPS data are used to derive the global, regional and vertical total electron content (vTEC) in the four selected regions. It is observed that the storm-time response of the vTEC over the Asian and Pacific sectors is earlier than over the African and American sectors. Magnetic observatory data are used to illustrate the variation in the magnetic field particularly, in its horizontal component. The global thermospheric neutral density ratio; i.e., O∕N2 maps obtained from the Global UltraViolet Spectrographic Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are used to characterize the storm-time response of the thermosphere. These maps exhibit a significant storm-time depletion of the O∕N2 density ratio in the northern middle and lower latitudes over the western Pacific and American sectors as compared to the eastern Pacific, Asian and African sectors. However, the positive storm effects in the O∕N2 ratio can be observed in the low latitudes and equatorial regions. It can be deduced that the storm-time thermospheric and ionospheric responses are correlated. Overall, the positive ionospheric storm effects appear over the dayside sectors which are associated with the ionospheric electric fields and the traveling atmospheric disturbances. It is inferred that a variety of space weather phenomena such as the coronal mass ejection, the high-speed solar wind stream and the solar radio flux are the cause of multiple day enhancements of the vTEC in the low- to mid-latitude ionosphere during the period 4–14 September 2017.
Abstract. We study the impact of geomagnetic storm of September 6–9, 2017 on the low-to-mid latitude ionosphere. The prominent feature of this solar event is the sequential occurrence of the two Dst minima of maximum negative values −148 nT and −122 nT on September 8 at 2 UT and 15 UT, respectively. The study is based on analyzing the data from GPS stations and the magnetometer observatories located at different longitudinal sectors such as Asia, Africa and America. The GPS data is used to derive the global, regional and vertical total electron content (TEC) in the selected regions. The data of the magnetic observatories is used to illustrate the variation in the magnetic field particularly, the horizontal component of the magnetic field. It is observed that the storm time response of the TEC over the pre-noon sector (Asia) is earlier than Africa and America. The global thermospheric composition maps by Global Ultraviolet Imager exhibits a storm time variation in the O/N2 ratio. The positive storm effects in the vertical TEC and in the O/N2 ratio occur in the low latitudes/ equatorial regions.
Ion acoustic shock waves (IASWs) are studied in an unmagnetized plasma consisting of electrons, positrons and adiabatically hot positive ions. This is done by deriving the Kadomstev-Petviashvilli-Burger (KPB) equation under the small-amplitude perturbation expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. The dependence of the IASWs on various plasma parameters is explored in detail. It is observed that an increasing positron concentration decreases the amplitude of the IASW. Furthermore, it is found that an increasing η 0 not only enhances the amplitude appreciably but also modifies the steepness of the shock front. Limiting cases of the KPB equation are also discussed. It is found that the amplitude of the KP soliton decreases with an increase in positron concentration. An interesting new equation in the limiting case (i.e. the Burger-KP equation) is given and its comparison with the KPB equation is also presented. The relevance of the present study with regard to the dense astrophysical environments is also pointed out.
We employ quasipotential analysis to derive the Sagdeev potential which accounts for the effect of electron trapping in a warm electronegative plasma with κ-distributed electrons. The trapped electron density is truncated to some finite order of the electrostatic potential Φ. This consequently leads to an extended KdV equation which gives rise to small amplitude double layers (SIADLs). The effects of various plasma parameters, e.g., superthermality index, the electron trapping efficiency, the mass ratio of negative to positive ion, the number density ratio of electron to positive ion, and temperature ratio of positive ion to electron on the small amplitude ion acoustic double layers (SIADLs), have been investigated. It has been found that these parameters have a significant modifying role in the SIADLs.
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