A 3NM-64_He added to LARC for Solar Extreme Event studies during solar cycle 24

The Antarctic Laboratory for Cosmic Rays (LARC, acronym for Laboratorio Antartico per i Raggi Cosmici or Laboratorio Antártico para Rayos Cósmicos) operates on King George Island (South Shetlands). Since January 1991 a standard 6NM-64 detector has been recording continuous cosmic ray measurements and several Ground-Level Enhancements have been registered. Here we describe the different phases performed in Italy for the realization of a 3NM-64_³He detector, which started its measurements during the Italian XXII Antarctic Summer Campaign. Data recorded during solar activity cycle 24 will furnish an useful research tool for the next Solar Extreme Events.     

Study of the influence of solar variability on a regional (Indian) climate: 1901–2007

We use Indian temperature data of more than 100 years to study the influence of solar activity on climate. We study the Sun–climate relationship by averaging solar and climate data at various time scales; decadal, solar activity and solar magnetic cycles. We also consider the minimum and maximum values of sunspot number (SSN) during each solar cycle. This parameter SSN is correlated better with Indian temperature when these data are averaged over solar magnetic polarity epochs (SSN maximum to maximum). Our results indicate that the solar variability may still be contributing to ongoing climate change and suggest for more investigations.     

Nonlinear electromagnetic perturbations in a degenerate electron–positron plasma

Nonlinear propagation of fast and slow magnetosonic perturbation modes in an ultra-cold, degenerate (extremely dense) electron–positron (EP) plasma (containing non-relativistic, ultra-cold, degenerate electron and positron fluids) has been investigated by the reductive perturbation method. It is shown that due to the property of being equal mass of the plasma species (_me=_mp$m_e=m_p$, where _me$m_e$ and _mp$m_p$ are electron and positron mass, respectively), the degenerate EP plasma system supports the K-dV solitons which are associated with either fast or slow magnetosonic perturbation modes. It is also found that the basic features of the electromagnetic solitary structures, which are found to exist in such a degenerate EP plasma, are significantly modified by the effects of degenerate electron and positron pressures. The applications of the results in an EP plasma medium, which occurs in compact astrophysical objects, particularly in white dwarfs, have been briefly discussed.     

Heating heavy ions in the polar corona by collisionless shocks: A one-dimensional simulation

Recently a new model for explaining the observations of preferential heating of heavy ions in the polar solar corona was proposed ( and ). In that model the ion energization mechanism is the ion reflection off supercritical quasi-perpendicular collisionless shocks in the corona and the subsequent acceleration by the motional electric field E = −V × B/c. The mechanism of heavy ion reflection is based on ion gyration in the magnetic overshoot of the shock. The acceleration due to the motional electric field is perpendicular to the magnetic field, giving rise to large temperature anisotropy with T_⊥ ? T_∥, in agreement with SoHO observations. Such a model is tested here by means of a one dimensional test particle simulation where ions are launched toward electric and magnetic profiles representing the shock transition. We study the dynamics of O⁵⁺, as representative of coronal heavy ions for Alfvénic Mach numbers of 2–4, as appropriate to solar corona. It is found that O⁵⁺ ions are easily reflected and gain more than mass proportional energy with respect to protons.     

Modeling and observations of the north–south ionospheric asymmetry at low latitudes at long deep solar minimum

Using the physics based model SUPIM and FORMOSAT-3/COSMIC electron density data measured at the long deep solar minimum (2008–2010) we investigate the longitude variations of the north–south asymmetry of the ionosphere at low latitudes (±30° magnetic). The data at around diurnal maximum (12:30–13:30 LT) for magnetically quiet (Ap ? 15) equinoctial conditions (March–April and September–October) are presented for three longitude sectors (a) 60°E–120°E, (b) 60°W–120°W and (c) 15°W–75°W. The sectors (a) and (b) have large displacements of the geomagnetic equator from geographic equator but in opposite hemispheres with small magnetic declination angles; and sector (c) has large declination angle with small displacement of the equators; vertical E × B drift velocities also have differences in the three longitude sectors. SUPIM investigates the importance of the displacement of the equators, magnetic declination angle, and E × B drift on the north–south asymmetry. The data and model qualitatively agree; and indicate that depending on longitudes both the displacement of the equators and declination angle are important in producing the north–south asymmetry though the displacement of the equators seems most effective. This seems to be because it is the displacement of the equators more than the declination angle that produces large north–south difference in the effective magnetic meridional neutral wind velocity, which is the main cause of the ionospheric asymmetry. For the strong control of the neutral wind, east–west electric field has only a small effect on the longitude variation of the ionospheric asymmetry. Though the study is for the long deep solar minimum the conclusions seem valid for all levels of solar activity since the displacement of the equators and declination angle are independent of solar activity.     

Dynamic orbit propagation in a gravitational field of an inhomogeneous attractive body using the Lagrange coefficients

The analytical methods have nearly been replaced by the numerical methods due to their higher accuracy and accessibility of computation facilities. The semi-analytical Lagrange method of orbit propagation using f and g series is a competitive alternative to the numerical integration technique if the Lagrange coefficients are derived in a full gravitational field. In this paper, a generalization of the Lagrange method of orbit propagation is introduced. In other words, we introduce a complete form of the Lagrange coefficients in all force fields developed in the spherical harmonics for example full gravitational field of the Earth. The method is numerically compared with the numerical integration technique. In order to show the numerical performance of the method, it has been implemented for orbit propagation of a GPS-like MEO and CHAMP-like LEO satellites. Discrepancy at centimeter level for CHAMP-like and sub-millimeter accuracy for GPS-like satellites shows relatively high performance of the developed algorithm. Compared to integration method, the proposed Lagrange method is nearly faster by a factor two for small Nmax and four for large Nmax.     

Predicting the probability of occurrence of spread-F over Brazil using neural networks

The probability of occurrence of spread-F can be modeled and predicted using neural networks (NNs). This paper presents a feasibility study into the development of a NN based model for the prediction of the probability of occurrence of spread-F over selected equatorial stations within the Brazilian sector. The input space included the day number (seasonal variation), hour (diurnal variation), sunspot number (measure of the solar activity), magnetic index (measure of the magnetic activity) and magnetic position. Twelve years of spread-F data from Brazil (covering the period 1978–1989) measured at the equatorial site Fortaleza (3.9°S, 38.45°W) and low latitude site Cachoeira Paulista (22.6°S, 45.0°W) are used in the development of an input space and NN architecture for the model. Spread-F data that is believed to be related to plasma bubble developments (range spread-F) was used in the development of the model. The model results show the probability of spread-F occurrence as a function of local time, season and latitude. Results from the Brazilian Sector NN (BSNN) based model are presented in this paper, as well as a comparative analysis with a Brazilian model developed for the same purpose.     

Effect of vertical plasma transport on ionospheric F2-region parameters at equatorial latitude

The variability of the F2-layer even during magnetically quiet times are fairly complex owing to the effects of plasma transport. The vertical E × B drift velocities (estimated from simplified electron density continuity equation) were used to investigate the seasonal effects of the vertical ion drifts on the bottomside daytime ionospheric parameters over an equatorial latitude in West Africa, Ibadan, Nigeria (Geographic: 7.4°N, 3.9°E, dip angle: 6°S) using 1 year of ionsonde data during International Geophysical Year (IGY) of 1958, that correspond to a period of high solar activity for quiet conditions. The variation patterns between the changes of the vertical ion drifts and the ionospheric F2-layer parameters, especially; f_oF₂ and h_mF₂ are seen remarkable. On the other hand, we observed strong anti-correlation between vertical drift velocities and h′F in all the seasons. We found no clear trend between N_mF₂ and h_mF₂ variations. The yearly average value of upward daytime drift at 300 km altitude was a little less than the generally reported magnitude of 20 ms⁻¹ for equatorial F-region in published literature, and the largest upward velocity was roughly 32 ms⁻¹. Our results indicate that vertical plasma drifts; ionospheric F2-layer peak height, and the critical frequency of F2-layer appear to be somewhat interconnected.     

Remote sensing using GNSS signals: Current status and future directions

The refracted, reflected and scattered signals of global navigation satellite systems (GNSS) have been successfully used to remotely sense the Earth’s surface and atmosphere. It has demonstrated its potential to sense the atmosphere and ionosphere, ocean, land surfaces (including soil moisture) and the cryosphere. These new measurements, although in need of refinement and further validation in many cases, can be used to complement existing techniques and sensors, e.g., radiosonde, ionosonde, radar altimetry and synthetic aperture radar (SAR). This paper presents the current status and new developments of remote sensing using GNSS signals as well as its future directions and applications. Some notable emerging applications include monitoring sea ice, dangerous sea states, ocean eddy and storm surges. With the further improvement of the next generation multi-frequency GNSS systems and receivers and new space-based instruments utilizing GNSS reflections and refractions, new scientific applications of GNSS are expected in various environment remote sensing fields in the near future.     

GPS derived TEC and foF2 variability at an equatorial station and the performance of IRI-model

The ionosphere induces a time delay in transionospheric radio signals such as the Global Positioning System (GPS) signal. The Total Electron Content (TEC) is a key parameter in the mitigation of ionospheric effects on transionospheric signals. The delay in GPS signal induced by the ionosphere is proportional to TEC along the path from the GPS satellite to a receiver. The diurnal monthly and seasonal variations of ionospheric electron content were studied during the year 2010, a year of extreme solar minimum (F10.7 = 81 solar flux unit), with data from the GPS receiver and the Digisonde Portable Sounder (DPS) collocated at Ilorin (Geog. Lat. 8.50°N, Long. 4.50°E, dip −7.9°). The diurnal monthly variation shows steady increases in TEC and F2-layer critical frequency (foF2) from pre-dawn minimum to afternoon maximum and then decreases after sunset. TEC show significant seasonal variation during the daytime between 0900 and 1900 UT (LT = UT + 1 h) with a maximum during the March equinox (about 35 TECU) and minimum during the June solstice (about 24 TECU). The GPS-TEC and foF2 values reveal a weak seasonal anomaly and equinoctial asymmetry during the daytime. The variations observed find their explanations in the amount of solar radiation and neutral gas composition. The measured TEC and foF2 values were compared with last two versions of the International Reference Ionosphere (IRI-2007 and IRI-2012) model predictions using the NeQuick and CCIR (International Radio Consultative Committee) options respectively in the model. In general, the two models give foF2 close to the experimental values, whereas significant discrepancies are found in the predictions of TEC from the models especially during the daytime. The error in height dependent thickness parameter, daytime underestimation of equatorial drift and contributions of electrons from altitudes above 2000 km have been suggested as the possible causes.     

Multi-spacecraft tracing of turbulent boundary layer

Multi-spacecraft tracing of the high latitude magnetopause (MP) and boundary layers and Interball-1 statistics indicate that:

1. (a) The turbulent boundary layer (TBL) is a persistent feature in the region of the cusp and ‘sash’, a noticeable part of the disturbances weakly depends on the interplanetary magnetic field By component; TBL is a major site for magnetosheath (MSH) plasma penetration inside the magnetosphere through percolation and local reconnection.

2. (b) The TBL disturbances are mainly inherent with the characteristic kinked double-slope spectra and, most probably, 3-wave cascading. The bi-spectral phase coupling indicates self-organization of the TBL as the entire region with features of the non-equilibrium multi-scale and multi-phase system in the near-critical state.

3. (c) We've found the different outer cusp topologies in summer/winter periods: the summer cusp throat is open for the decelerated MSH flows, the winter one is closed by the distant MP with a large-scale (several Re) diamagnetic ‘plasma ball’ inside the MP; the ‘ball’ is filled from MSH through patchy merging rather than large-scale reconnection.

4. (d) A mechanism for the energy release and mass inflow is the local TBL reconnection, which operates at the larger scales for the average anti-parallel fields and at the smaller scales for the nonlinear fluctuating fields; the latter is operative throughout the TBL. The remote from TBL anti-parallel reconnection seems to happen independently.

Climatology of ionospheric scintillations and TEC trend over the Ugandan region

This study presents results on the investigation of the diurnal, monthly and seasonal variability of Total Electron Content (TEC), phase (_σΦ${\sigma }_{\mathrm{\Phi }}$) and amplitude (S4) scintillation indices over Ugandan (Low latitude) region. Scintillation Network Decision Aid (SCINDA) data was obtained from Makerere (0.34°N, 32.57°E) station, Uganda for two years (2011 and 2012). Data from two dual frequency GPS receivers at Mbarara (0.60°S, 30.74°E) and Entebbe (0.04°N, 32.44°E) was used to study TEC climatology during the same period of scintillation study. The results show that peak TEC values were recorded during the months of October–November, and the lowest values during the months of July–August. The diurnal peak of TEC occurs between 10:00 and 14:00 UT hours. Seasonally, the ascending and descending phases of TEC were observed during the equinoxes (March and September) and solstice (June and December), respectively. The scintillations observed during the study were classified as weak (0.1≤$\le$S4,_σΦ≤${\sigma }_{\mathrm{\Phi }}\le$0.3) and strong (0.3<$<$S4,_σΦ≤${\sigma }_{\mathrm{\Phi }}\le$1.0). The diurnal scintillation pattern showed peaks between 17:00 and 22:00 UT hour, while the seasonal pattern follows the TEC pattern mentioned above. Amplitude scintillation was more dominant than phase scintillation during the two years of the study. Scintillation peaks occur during the months of March–April and September–October, while the least scintillations occur during the months of June–July. Therefore, the contribution of this study is filling the gap in the current documentation of amplitude scintillation without phase scintillation over the Ugandan region. The scintillations observed have been attributed to wave-like structures which have periods of about 2–3 h, in the range of that of large scale travelling ionospheric disturbances (LSTIDs).     

Acceleration of energetic particles by whistler waves in active space experiment with charged particle beams injection

In this paper the investigation of wave-particle interaction during simultaneous injection of electron and xenon ion beams from the satellite Intercosmos-25 (IK-25) carried out using the data of the double satellite system with subsatellite Magion-3 (APEX). Results of active space experiment devoted to the beam-plasma instability are partially presented in the paper Baranets et al. (2007). A specific feature of the experiment carried out in orbits 201, 202 was that charged particle flows were injected in the same direction along the magnetic field lines B₀ so the oblique beam-into-beam injection have been produced. Results of the beam-plasma interaction for this configuration were registered by scientific instruments mounted on the station IK-25 and Magion-3 subsatellite. Main attention is paid to study the electromagnetic and longitudinal waves excitation in different frequency ranges and the energetic electron fluxes disturbed due to wave-particle interaction with whistler waves. The whistler wave excitation on the 1st electron cyclotron harmonic via normal Doppler effect during electron beam injection in ionospheric plasma are considered.     

Problems and progress in flare fast particle diagnostics

Recent progress in the diagnosis of flare fast particles is critically discussed with the main emphasis on high resolution hard X-ray (HXR) data from RHESSI and coordinated data from other instruments. Spectacular new photon data findings are highlighted as are advances in theoretical aspects of their use as fast particle diagnostics, and some important comparisons made with interplanetary particle data. More specifically the following topics are addressed:

• (a)RHESSI data on HXR (electron) versus gamma-ray line (ion) source locations.
• (b)RHESSI hard X-ray source spatial structure in relation to theoretical models and loop density structure.
• (c)Energy budget of flare electrons and the Neupert effect.
• (d)Spectral deconvolution methods including blind target testing and results for RHESSI HXR spectra, including the reality and implications of dips inferred in electron spectra.
• (e)The relation between flare in situ and interplanetary particle data.

     

Identification and dynamics of agricultural environments in Northeast Thailand from landsat images (1972, 1976, 1982)

The objective of this research is to prepare a cartographic methodology to present agricultural environments and their dynamics from satellite data. Three Landsat images (October 1972, January 1976, January 1982) have been used and a field survey has been done in 1984. After interactive processing on TRIAS system of Institut Geographique National (IGN). Five colour maps have been produced:

• - a spatio-map with the new roads (1:250,000);
• - a map of the surface-states in 1982 (classified image) using a comparison with the two other dates for improvement (1:250,000);
• - a map of agro-ecological landscape units based on the combination between surface states showing interrelationships between agrarian systems and bio-physical environment (1:5000,000);
• - a map of the surface moisture seasonal variations to show the availability of water for the agriculture (1:400,000);
• - a map of changes in some agricultural environments components (1972–1982): water and flooded areas, agricultural areas, forests (1:500,000).