Space Physics

This study focuses on the variability of 2 and the impact of the solar and geomagnetic activity on the variability of 2 over Ouagadougou, an equatorial ionisation anomaly station in the African sector. The daily hourly values of the critical frequency (2) covering two different solar cycles are used to study the variability of 2. The solar and geomagnetic data are used to examine their effect on the variability of 2. The results show that 2 displays obvious diurnal, seasonal and solar cycle effects. The semi-annual variation, winter and annual anomalies of 2 are clearly seen at all levels of solar activities. There is equinoctial asymmetry in 2. 2 is also characterized by two peaks namely pre-noon and post-noon peaks and noontime bite-out. The is observed to have major effects on the variability of 2.

Coronal Mass Ejections (CMEs) are believed to be effective in producing shocks in the solar corona and the interplanetary space. One of the important signatures of shocks and shock acceleration are Type II solar radio bursts that drift with the shock speed and produce bands of fundamental and higher harmonic plasma radio emission. An intriguing aspect of Type II radio bursts is the occasional split of a harmonic band into thinner lanes, known as band-splitting. Here, we report a detailed imaging and spectroscopic observation of a CME-driven shock producing band-splitting in a Type II burst. Using the Low Frequency Array (LOFAR), we examine the spatial and temporal relation of the Type II burst to the associated CME event, use source imaging to calculate the apparent coronal density, and demonstrate how source imaging can be used to estimate projection effects. We consider two widely accepted band-splitting models that make opposing predictions regarding the locations of the true emission sources with respect to the shock front. Our observations suggest that the locations of the upper and lower sub-band sources are spatially separated by ∼ 0.2 ± 0.05 R. However, we quantitatively show, for the first time, that such separation is consistent with radio-wave scattering of plasma radio emission from a single region, implying that the split-band Type II sources could originate from nearly co-spatial locations. Considering the effects of scattering, the observations provide supporting evidence for the model that interprets the band-splitting as emission originating in the upstream and downstream regions of the shock front, two virtually co-spatial areas.

Geodesy, the oldest science, has become an important discipline in the geosciences, in large part by enhancing Global Positioning System (GPS) capabilities over the last 35 years well beyond the satellite constellation's original design. The ability of GPS geodesy to estimate 3D positions with millimeter-level precision with respect to a global terrestrial reference frame has contributed to significant advances in geophysics, seismology, atmospheric science, hydrology, and natural hazard science. Monitoring the changes in the positions or trajectories of GPS instruments on the Earth's land and water surfaces, in the atmosphere, or in space, is important for both theory and applications, from an improved understanding of tectonic and magmatic processes to developing systems for mitigating the impact of natural hazards on society and the environment. Besides accurate positioning, all disturbances in the propagation of the transmitted GPS radio signals from satellite to receiver are mined for information, from troposphere and ionosphere delays for weather, climate, and natural hazard applications, to disturbances in the signals due to multipath reflections from the solid ground, water, and ice for environmental applications. We review the relevant concepts of geodetic theory, data analysis, and physical modeling for a myriad of processes at multiple spatial and temporal scales, and discuss the extensive global infrastructure that has been built to support GPS geodesy consisting of thousands of continuously operating stations. We also discuss the integration of heterogeneous and complementary data sets from geodesy, seismology, and geology, focusing on crustal deformation applications and early warning systems for natural hazards.

A dominant process by which energy and momentum are transported from the magnetosphere
to the ionosphere is known as field-aligned current (FAC). It is enhanced during magnetic reconnection and
explosive energy release at a substorm. In this paper, we studied FAC, interplanetary electric field component
(Ey), interplanetary magnetic field component (Bz), and northward (x) and eastward (y) components of
geomagnetic field during three events of supersubstorm occurred on 24 November 2001, 21 January 2005,
and 24 August 2005. Large-scale FAC, supposed to be produced during supersubstorm (SSS), has potentiality
to cause blackout on Earth. We examined temporal variations of the x and y components of high-latitude
geomagnetic field during SSS, which is attributed to the FACs. We shall report the characteristics of
high-latitude northward and eastward components of geomagnetic field variation during the growth phase
of SSS by the implementation of discrete wavelet transform (DWT) and cross-correlation analysis. Among
three examples of SSS events, the highest peak value of FAC was estimated to be ~19 μAm
2. This is shore up
with the prediction made by Parks (1991) and Stasiewicz et al. (1998) that the FACs may vary from a few
tens to several hundred μAm
2. Although this peak value of FACs for SSS event is much higher than the
average FACs associated with regular substorms or magnetic storms, it is expedient and can be expect for
SSS events which might be due to very high density solar wind plasma parcels (PPs) triggering the SSS
events. In all events, during growth phase, the FAC increases to extremely high level and the geomagnetic
northward component decreases to extremely low level. This represents a strong positive correlation
between FAC and geomagnetic northward component. The DWT analysis accounts that the highest
amplitude of the wavelet coefficients indicates singularities present in FAC during SSS event. But the
amplitude of squared wavelet coefficient is found to be different from each other, which might be due to the
solar wind PPs of different density triggering the SSS events. The cross-correlation analysis suggests that the
perturbation on geomagnetic northward component at high latitude during SSS strongly correlates with
the fluctuation pattern of FAC density. Hence, the FAC is the primary sources for the eastward-westward
magnetic field perturbations at high latitude.

We investigate an Australian Aboriginal cultural story that seems to describe an extraordinary series of astronomical events occurring at the same time. We hypothesise that this was a witnessed natural event and explore natural phenomena that could account for the description. We select a thunderstorm, total solar eclipse, and strong Aurora Australis as the most likely candidates, then conclude a plausible date of 764 CE. We evaluate the different factors that would determine whether all these events could have been visible, include meteorological data, alternative total solar eclipse dates, solar activity cycles, aurorae appearances, and sky brightness during total solar eclipses. We conduct this study as a test-case for rigorously and systematically examining descriptions of rare natural phenomena in oral traditions, highlighting the difficulties and challenges with interpreting this type of hypothesis.

Plasmas are ubiquitous in nature, surround our local geospace environment, and
permeate the universe. Plasma phenomena in space give rise to energetic particles, the
aurora, solar flares and coronal mass ejections, as well as many energetic phenomena
in interstellar space. Although plasmas can be studied in laboratory settings, it is often
difficult, if not impossible, to replicate the conditions (density, temperature, magnetic
and electric fields, etc.) of space. Single-point space missions too numerous to list have
described many properties of near-Earth and heliospheric plasmas as measured both
in situ and remotely (see http://www.nasa.gov/missions/#.U1mcVmeweRY for a list
of NASA-related missions). However, a full description of our plasma environment
requires three-dimensional spatial measurements. Cluster is the first, and until data
begin flowing from the Magnetospheric Multiscale Mission (MMS), the only mission
designed to describe the three-dimensional spatial structure of plasma phenomena in
geospace. In this paper, we concentrate on some of the many plasma phenomena
that have been studied using data from Cluster. To date, there have been more
than 2000 refereed papers published using Cluster data but in this paper we will,
of necessity, refer to only a small fraction of the published work. We have focused
on a few basic plasma phenomena, but, for example, have not dealt with most of
the vast body of work describing dynamical phenomena in Earth’s magnetosphere,
including the dynamics of current sheets in Earth’s magnetotail and the morphology
of the dayside high latitude cusp. Several review articles and special publications
are available that describe aspects of that research in detail and interested readers
are referred to them (see for example, Escoubet et al. 2005 Multiscale Coupling of
Sun-Earth Processes, p. 459, Keith et al. 2005 Sur. Geophys. 26, 307–339, Paschmann
et al. 2005 Outer Magnetospheric Boundaries: Cluster Results, Space Sciences Series of
ISSI. Berlin: Springer, Goldstein et al. 2006 Adv. Space Res. 38, 21–36, Taylor et al.

We developed a new technique for registration of the far solar corona from ground-based observations at distances comparable to those obtained from space coronagraphs. It makes possible visualization of fine details of studied objects invisible by naked eye. Here we demonstrate that streamers of the electron corona sometimes punch the dust corona and that the shape of the dust corona

We present a study about the propagation of interplanetary shock waves driven by super magnetosonic coronal mass ejections (CMEs). The discussion focus on a model which discribes the dynamic relationship between the CME and its driven shock and the way to approximate the trajectory of shocks based on those relationships from near the Sun to 1 AU. We apply the model in the analysis of a study case, in which our calculations show quantitative and cualitative agreements with different kind of data. We discuss the importance of solar wind and CME initial conditions on the shock wave evolution.

Legislative modifications of the General Civil Protection Law in Mexico in 2014 included specific references to space hazards and space weather phenomena. The legislation is consistent with United Nations promotion of international engagement and cooperation on space weather awareness, studies, and monitoring. These internal and external conditions motivated the creation of a space weather service in Mexico. The Mexican Space Weather Service (SCiESMEX in Spanish) (www.sciesmex.unam.mx) was initiated in October 2014 and is operated by the Institute of Geophysics at the Universidad Nacional Autonoma de Mexico (UNAM). SCiESMEX became a Regional Warning Center of the International Space Environment Services (ISES) in June 2015. We present the characteristics of the service, some products, and the initial actions for developing a space weather strategy in Mexico. The service operates a computing infrastructure including a web application, data repository, and a high-performance computing server to run numerical models. SCiESMEX uses data of the ground-based instrumental network of the National Space Weather Laboratory (LANCE), covering solar radio burst emissions, solar wind and interplanetary disturbances (by interplanetary scintillation observations), geomagnetic measurements, and analysis of the total electron content (TEC) of the ionosphere (by employing data from local networks of GPS receiver stations).

Interplanetary Coronal mass ejections (ICMEs) (super-magnetosonically) faster than the ambient solar wind are preceded by shock waves. Earth-directed shock waves, plasma sheaths and ICMEs are precursors of the major geomag-netic storms. The plasma sheath between the shock and the ICME leading edge plays a very important role to determine the geoeffectiveness of the events. There are multiple efforts (empirical, analytical and numerical) to forecast ICME-shock transit times and arrival speeds to 1 AU. We present a formalism (combining analytical and empirical solutions) to compute tra-jectories of fast halo Earth directed ICMEs, plasma sheaths, and shocks. This formalism combines the 'piston-shock' semi-empirical model (Corona-Romero et al., 2013), and the MHD polytropic jump relations (Petrinec and

" Zebra stripes " are newly found energetic electron energy-spatial (L shell) distributed structure with an energy between tens to a few hundreds keV in the inner radiation belt. Using high-quality measurements of electron fluxes from Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the twin Van Allen Probes, we carry out case and statistical studies from April 2013 to April 2014 to study the structural and evolutionary characteristics of zebra stripes below L = 3. It is revealed that the zebra stripes can be transformed into evenly spaced patterns in the electron drift frequency coordinate: the detrended logarithmic fluxes in each L shell region can be well described by sinusoidal functions of drift frequency. The " wave number " of this sinusoidal function, which corresponds to the reciprocal of the gap between two adjacent peaks in the drift frequency coordinate, increases in proportion to real time. Further, these structural and evolutionary characteristics of zebra stripes can be reproduced by an analytic model of the evolution of the particle distribution under a single monochromatic or static azimuthal electric field. It is shown that the essential ingredient for the formation of multiple zebra stripes is the periodic drift of particles. The amplitude of the zebra stripes shows a good positive correlation with Kp index, which indicates that the generation mechanism of zebra stripes should be related to geomagnetic activities.

The variation of horizontal component of the geomagnetic field (Sq-H) is taken in the year 2003 to study the diurnal, monthly as
well as seasonal variation of Sq-H using 4 geomagnetic stations across various latitudes and longitudes. We have carried out this work on “Variation of Horizontal Component of Magnetic Field in Low Solar Activity” to understand the variation of solar quite (Sq)
current and its effect on the Earth’s surface. The geomagnetic daily variations in the ionosphere are produced by electric currents.
We studied the variation of Sq current over the various 4 quietest days of February 2003. Results show that Sq (H) exhibits transient
variations with varying amplitude according to seasons and days of the year 2003. The analysis was carried out on solar quiet days
using hourly values of horizontal H component of geomagnetic field. The variations of Sq-H are mainly characterized maximum
around the daytime (0700–1700 LT) and the minimum around pre-sunrise (0500–0600 LT) and the nighttime (1800–0400 LT). These
results show that the Sq-H have consistent minimum values during pre-sunrise hours between 0500 and 0600 LT. The maxima