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We analyze Big Data in solar-terrestrial physics in order to explain and predict the dynamics of geomagnetic phenomena. We apply wavelet analysis to high-frequency time series data from various sources: (1) the interplanetary magnetic field (from the ACE satellite), (2) the ionospheric parameters – TEC (from ionospheric sounding stations), and (3) the ground geomagnetic data (from ground geomagnetic observatories, located at middle geographic latitudes). We seek for correlations in the wavelet coefficients which explain the dynamics of different magnetic phenomena in the solar-terrestrial physics. The large variety of data used in our research from both solar astronomy and Earth observations makes it a contribution to the newly developing area of AstroGeoInformatics.

The main purpose of this paper is to investigate the response of the ionospheric F layer in the American and African sectors during the intense geomagnetic storm which occurred on 30 September-01 October 2012. In this work, we used observations from a chain of 20 GPS stations in the equatorial, low- and mid-latitude regions in the American and African sectors. Also, in this study ionospheric sounding data obtained during 29th September to 2nd October, 2012 at Jicamarca (JIC), Peru, São Luis (SL), Fortaleza (FZ), Brazil, and Port Stanley (PST), are presented. On the night of 30 September-01 October, in the main and recovery phase, the hDF variations showed an unusual uplifting of the F region at equatorial (JIC, SL and FZ) and mid- (PST) latitude stations related with the propagations of traveling ionospheric disturbances (TIDs) generated by Joule heating at auroral regions. On 30 September, the VTEC variations and foF2 observations at mid-latitude stations (American sector) showed a long-duration positive ionospheric storm (over 6h of enhancement) associated with large-scale wind circulations and equatorward neutral winds. Also, on 01 October, a long-duration positive ionospheric storm was observed at equatorial, low- and mid- latitude stations in the African sector, related with the large-scale wind circulations and equatorward neutral winds. On 01 and 02 October, positive ionospheric storms were observed at equatorial, low- and mid-latitude stations in the American sector, possibly associated with the TIDs and an equatorward neutral wind. Also, on 01 October negative ionospheric storms were observed at equatorial, low- and mid-latitude regions in the American sector, probably associated with the changes in the O/N2 ratio. On the night of 30 September-01 October, ionospheric plasma bubbles were observed at equatorial, low- and mid- latitude stations in the South American sector, possibly associated with the occurrence of geomagnetic storm. Fil: de Jesus, R.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasil. Universidade do Vale do Paraíba; Brasil Fil: Fagundes, P.R.. Universidade do Vale do Paraíba; Brasil Fil: Coster, A.. Massachusetts Institute of Technology; Estados Unidos Fil: Bolaji, O. S.. University of Lagos; Nigeria Fil: Sobral, J. H. A.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasil Fil: Batista, I. S.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasil Fil: de Abreu, A. J.. Universidade do Vale do Paraíba; Brasil. Instituto Tecnológico de Aeronáutica; Brasil Fil: Venkatesh, K.. Universidade do Vale do Paraíba; Brasil Fil: Gende, Mauricio Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina Fil: Abalde, J. R.. Universidade do Vale do Paraíba; Brasil Fil: Sumod, S. G.. Mahatma Gandhi University; India

Mars Express, the first European interplanetary mission, carries the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to search for ice and water in the Martian subsurface. Developed by an Italian–US team, MARSIS transmits low-frequency, wide-band radio pulses penetrating below the surface and reflected by dielectric discontinuities linked to structural or compositional changes. MARSIS is also a topside ionosphere sounder, transmitting a burst of short, narrow-band pulses at different frequencies that are reflected by plasma with varying densities at different altitudes. The radar operates since July 2005, after the successful deployment of its 40 m antenna, acquiring data at altitudes lower than 1200 km. Subsurface sounding (SS) data are processed on board by stacking together a batch of echoes acquired at the same frequency. On ground, SS data are further processed by correlating the received echo with the transmitted waveform and compensating de-focusing caused by the dispersive ionosphere. Ground processing of active ionospheric sounding (AIS) data consists in the reconstruction of the electron density profile as a function of altitude. MARSIS observed the internal structure of Planum Boreum outlining the Basal Unit, an icy deposit lying beneath the North Polar Layered Deposits thought to have formed in an epoch in which climate was markedly different from the current one. The total volume of ice in polar layered deposits could be estimated, and parts of the Southern residual ice cap were revealed to consist of ≈ 10 m of CO2 ice. Radar properties of the Vastitas Borealis Formation point to the presence of large quantities of ice buried beneath the surface. Observations of the ionosphere revealed the complex interplay between plasma, crustal magnetic field and solar wind, contributing to space weather studies at Mars. The presence of three-dimensional plasma structures in the ionosphere was revealed for the first time. MARSIS could successfully operate at Phobos, becoming the first instrument of its kind to observe an asteroid-like body. The main goal pursued by MARSIS, the search for liquid water beneath the surface, remains elusive. However, because of the many factors affecting detection and of the difficulties in identifying water in radar echoes, a definitive conclusion on its presence cannot yet be drawn.

In this paper, we present and discuss the response of the ionospheric F-region in the American sector during the intense geomagnetic storm which occurred on 24–25 October 2011. In this investigation ionospheric sounding data obtained of 23, 24, 25, and 26 October 2011 at Puerto Rico (United States), Jicamarca (Peru), Palmas, Sa˜o Jose´ dos Campos (Brazil), and Port Stanley, are presented. Also, the GPS observations obtained at 12 stations in the equatorial, low-, mid- and high-mid-latitude regions in the American sector are presented. During the fast decrease of Dst (about 54 nT/h between 23:00 and 01:00 UT) on the night of 24–25 October (main phase), there is a prompt penetration of electric field of magnetospheric origin resulting an unusual uplifting of the F region at equatorial stations. On the night of 24–25 October 2011 (recovery phase) equatorial, low- and mid-latitude stations show h0 F variations much larger than the average variations possibly associated with traveling ionospheric disturbances (TIDs) caused by Joule heating at high latitudes. The foF2 variations at mid-latitude stations and the GPS-VTEC observations at mid- and low-latitude stations show a positive ionospheric storm on the night of 24–25 October, possibly due to changes in the large-scale wind circulation. The foF2 observations at mid-latitude station and the GPS-VTEC observations at mid- and high-mid-latitude stations show a negative ionospheric storm on the night of 24–25 October, probably associated with an increase in the density of molecular nitrogen. During the daytime on 25 October, the variations in foF2 at mid-latitude stations show large negative ionospheric storm, possibly due to changes in the O/N2 ratio. On the night of 24–25, ionospheric plasma bubbles (equatorial irregularities that extended to the low- and mid-latitude regions) are observed at equatorial, lowand mid-latitude stations. Also, on the night of 25–26, ionospheric plasma bubbles are observed at equatorial and low-latitude regions. Fil: de Jesus, R.. Universidade do Vale do Paraíba; Brasil Fil: Sahai, Y.. Universidade do Vale do Paraíba; Brasil Fil: Fagundes, P. R.. Universidade do Vale do Paraíba; Brasil Fil: de Abreu, A. J.. Universidade do Vale do Paraíba; Brasil Fil: Brunini, Claudio Antonio. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gende, Mauricio Alfredo. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Bittencourt, J. A.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; Brasil Fil: Abalde, J. R.. Universidade do Vale do Paraíba; Brasil Fil: Pillat, V. G.. Universidade do Vale do Paraíba; Brasil

A controlled active experiment was performed by a plasma gun on-board a rocket to study the plasma stream across the magnetic field in space. A mother and daughter system was employed. An 8 kV 0.8 μF (25 J) capacitor bank on the daughter rocket was discharged every 12 s and about 1016 ion and electron pairs were ejected. A plasma signal was detected on the electron temperature probe. The propagation speed of the plasma stream is estimated to be 106 cm/s, considerably lower than that obtained in the prelaunch test. The amplitude of the plasma signal decays as the inverse square of the mutual distance between the mother and daughter rockets and this decay is much slower than the free streaming. The importance of the geomagnetic field on the plasma propagation in space is discussed.

Electron density data obtained over the dip equator using rocket-borne high resolution Langmuir probes is examined during the presence of blanketing (Es-b) as well as diffused type (Es-q) sporadic E layers in the ionosphere. Plasma irregularities are found to exist in both the cases which could be ascribed to the crossfield instability mechanism. It is found that the irregularities are located in the bottomside gradient portion in the E region when Es-q is generated and on the topside gradient portion of a sublayer produced during Es-b. This behaviour is interpreted in terms of the orientation and shape of the plasma irregularities which in both cases are found to have a saw-tooth structure. It is suggested that the presence of long lived metallic ions must be facilitating the formation and maintenance of the observed sharp structure of the irregularities.

Based on a novel approach, it is demonstrated that VHF Backscatter Radar observations on the equatorial electrojet can be used to estimate the ionospheric and magnetospheric contributions to the low latitude geomagnetic field perturbations during magnetic storms.

Using the VHF backscatter radar observations on the equatorial electrojet at Thumba, the possibility of the short period (20–40 mins.) fluctuations of the electrojet on quiet days being a part of the global scale electric field fluctuations has been examined. The observations on days with Ap ≤ 6 indicate that the equatorial electrojet fluctuations even on quiet days are likely to be caused by global scale electric field fluctuations which originate in the auroral-polar dynamo region disturbances.

Results of total electron content at 0otacamund obtained from Faraday rotation measurements (NF) and from Group delay measurements (NT) are described. Using bottomside ionogram data from Kodaikanal, equivalent slab-thickness (NT/Nm) has also been studied. In addition residual content NR, defined as NT-NF and a rough measure of the plasmasphere electron content, has been obtained and its daily variation studied. With increasing geomagnetic activity, the peak value of NR decreases suggesting the depletion of the plasmasphere.

Using rocket-borne H.F. quadrupole probes, the altitude profiles of electron density (Ne) in the E-region over Thumba have been obtained on two occasions. During the time of the first rocket measurement, a strong partial counter electrojet event plus a magnetic substorm disturbance were in progress, while a weaker partial counter electrojet event was in progress during the second flight. Both electron density profiles show a significant decrease of Ne at higher E-region altitudes, in contrast to earlier observational results.

Small amplitude oscillations of 4 − 5 minute period and larger amplitude quasi-periodic fluctuations of 20 − 25 minutes period have been observed in the mean Doppler frequency of the VHF radar signals backscattered from the equatorial electrojet irregularities at Thumba. The Doppler frequency fluctuations are attributed to the electric field fluctuations generated by propagating acoustic-gravity waves in the electrojet. Such an interpretation is supported by two other observational evidences: (a) the change of phase of the fluctuations with height as observed with the backscatter radar and (b) the occurrence of blanketing ES layers (as indicated by ionograms) along with the oscillations of the electric fields.

A four-channel electrophotometer was instaled on board a Centaur-II rocket to measure the vertical distribution of 5577 A, 6563 A, 6600 A, 3914 A airglow emissions. The rocket was launched on 31 October 1978 from Thumba, India, in moderate solar and geomagnetic activity conditions -Ap = 20, Kp =4, Dst = − 74, Rs = 98, F10.7 = 144. The pair of red filters showed no H emission, i.e. no particle dissipation. The green oxygen line emission is between 77 and 110 km, with maximum at 97 km. A slow intensity increase is observed at about 105 km. The illumination of 3900 A filter was interpreted as emission of 02 Herzberg's band. The intensity maximum coincided with that of 5577 A. Some atmospheric parameters within the interval 75–110 km are calculated using the experimental values and the Chapman mechanism of excitation.

Results of measurement of atmospheric ion and neutral composition between 100 to 160 km are presented. The measurements have been carried out on December 21, 1978 (one at night and the other at sunrise) on board of two Centaure rockets flown from Thumba Equatorial Rocket Launching Station. The observations show the existence of strong diurnal variations of the atmospheric composition in the lower thermosphere and in the altitude of the turbopause. The results are compared with those obtained from similar measurements made in 1975.

Doppler frequency measurements with VHF backscatter radar at Thumba give the drift velocity of the ionization irregularities, which can be used to deduce the electron drift velocity. By measuring the frequency shifts at different altitudes within the electrojet, the height structure of the electron drift velocity in the E-W direction is obtained. The study shows that on some days, deviations from a simple structure in the altitude profile take place. Also westward currents flowing at lower heights (below 100 km.) along with the normal eastward currents above 100 km are also observed on some days.

The paper gives an overall review on the original or modified instrumentation designed for the Intercosmos-Bulgaria-1300 experiment. The main scientific fields of research are also discissed. Fundamental space physics problems related with insufficient knowledge or instrumental reliability are also described.

A v.l.f. ionospheric sounding system has been designed, built, and operated by the U.S. Navy Electronics Laboratory for the purpose of examining the structure and propagation characteristics of the D-region. The system consists of a 30 kW phase stable CW transmitter, two horizontal half-wave dipole transmitting antennas aligned along and normal to the geomagnetic field, and three receivers capable of measuring phase and amplitude. The receivers are located in mobile vans. The transmitting antennas possess ground wave nulls normal to the antenna axes at midpoint and most of the radiation is directed upward thus allowing a suitably placed receiver to receive only an ionospherically reflected downcoming wave. Spaced receiver measurements have been made at 10, 13, 17 and 23 kc/s. Spectra of phase and amplitude fluctuations and the cross correlograms between phase and amplitude are presented. The drift direction and velocity of ionospheric inhomogeneities derived from cross correlations of fluctuation data between pairs of receivers are discussed. The reflection coefficients predicted by the full-wave solution of the wave equations for propagation in a continuous magneto-ionic medium are compared with measured characteristics of the polarization ellipse of the downcoming wave. The profiles of electron density and collision frequency which give the best agreement between the theoretical and experimental results are discussed.