The plasma mantle: Composition and other characteristics observed by means of the PROGNOZ-7 satellite

A brief summary of the main results of magnetospheric ion composition measurements in general is first presented. PROGNOZ-7 measurements in the nightside plasma mantle are then described and analyzed. Some of the results are the following: In the nightside mantle not too far from midnight the properties of the mantle are sometimes consistent with the open magnetosphere model. However during most magnetic storm situations O⁺ ions appear in the mantle in large proportions and with high energies. The acceleration process affecting the ions has been found in several cases to give equal amounts of energy to all ions independent of mass. Along the flanks of the magnetosphere the flow of the plasma is often low or absent. The O⁺ content is high (up to 20%) and the energy spectrum of both ions and electrons may be very hot, even up to the level of the ring current plasma in the keV range.The O⁺ content in the plasma mantle is positively correlated with the magnetospheric activity level. The mantle, however, does not appear to be the dominating source for the storm time ring current. Direct acceleration of ionospheric ions onto the closed field lines of the plasma sheet and ring current is most likely the main source. The magnetopause on the nightside and along the flanks of the magnetosphere appears to be a fairly solid boundary for mantle ions of ionospheric origin. This is especially evident during periods with high geomagnetic activity, when the mantle is associated with fairly strong fluxes of O⁺ ions.An interesting observation in most of the mantle passages during geomagnetically disturbed periods is the occurrence of intense, magnetosheath like, regions deep inside the mantle. In some cases these regions with strong antisunward flow and with predominant magnetosheath ion composition was observed in the innermost part of the mantle, i.e. marking a boundary region between the lobe and the mantle. These magnetosheath penetration events are usually associated with strong fluxes of accelerated ionospheric ions in nearby parts of the mantle. Evanescent penetration regions with much reduced flow properties are frequently observed in the flank mantle.     

Application of SVM on satellite images to detect hotspots in Jharia coal field region of India

The present paper deals with the application of Support Vector Machine (SVM) and image analysis techniques on NOAA/AVHRR satellite image to detect hotspots on the Jharia coal field region of India. One of the major advantages of using these satellite data is that the data are free with very good temporal resolution; while, one drawback is that these have low spatial resolution (i.e., approximately 1.1 km at nadir). Therefore, it is important to do research by applying some efficient optimization techniques along with the image analysis techniques to rectify these drawbacks and use satellite images for efficient hotspot detection and monitoring. For this purpose, SVM and multi-threshold techniques are explored for hotspot detection. The multi-threshold algorithm is developed to remove the cloud coverage from the land coverage. This algorithm also highlights the hotspots or fire spots in the suspected regions. SVM has the advantage over multi-thresholding technique that it can learn patterns from the examples and therefore is used to optimize the performance by removing the false points which are highlighted in the threshold technique. Both approaches can be used separately or in combination depending on the size of the image. The RBF (Radial Basis Function) kernel is used in training of three sets of inputs: brightness temperature of channel 3, Normalized Difference Vegetation Index (NDVI) and Global Environment Monitoring Index (GEMI), respectively. This makes a classified image in the output that highlights the hotspot and non-hotspot pixels. The performance of the SVM is also compared with the performance obtained from the neural networks and SVM appears to detect hotspots more accurately (greater than 91% classification accuracy) with lesser false alarm rate. The results obtained are found to be in good agreement with the ground based observations of the hotspots. This type of work will be quite helpful in the near future to develop a hotspots monitoring system using these operational satellites data.     

Rio de la Plata estuarine system: Relationship between river flow and frontal variability

This paper deals with the application of SeaWIFS images to characterize spatial and temporal variability of fronts in the Rio de la Plata estuarine system over the period 2000–2003. We aim to depict the relationship between river outflow and variability of fronts’ loci on monthly to ENSO-related timescales and the influence of the winds along Rio de la Plata (axial winds) on the abrupt changes in frontal dynamics over synoptic timescales. During the studied period both La Niña (July 1999–June 2000) and El Niño (April 2002–May 2003) events induced significant displacements of fronts. Three distinct fronts were analyzed between river, estuarine, coastal and marine waters of the Rio de la Plata: Main Turbidity Front, Main Marine Front, and Secondary Marine Front. Their number, location and separation seem to be mainly related to river outflow and second, to fresh (>8 m/s) axial winds. During low discharge periods (i.e. summer time and/or La Niña events) these winds induce abrupt changes in the location of fronts (100–200 km) and greater separation between them over synoptic timescale, whereas during high river discharge or ENSO years some of the variability of fronts location is explained by the river’s outflow fluctuations, especially by the high variability of the River Uruguay discharge.     

Indirect search for Dark Matter with H.E.S.S.

Observations of the Galactic center region with the H.E.S.S. telescopes have established the existence of a steady, extended source of gamma-ray emission coinciding with the position of the super massive black hole Sgr A^*. This is a remarkable finding given the expected presence of dense self-annihilating Dark Matter in the Galactic center region. The self-annihilation process is giving rise to gamma-ray production through hadronization including the production of neutral pions which decay into gamma-rays but also through (loop-suppressed) annihilation into final states of almost mono-energetic photons. We study the observed gamma-ray signal (spectrum and shape) from the Galactic center in the context of Dark Matter annihilation and indicate the prospects for further indirect Dark Matter searches with H.E.S.S.     

Ballooning perturbations in the inner magnetosphere of the Earth: Spectrum,stability and eigenmode analysis

We investigate the generation of ballooning perturbations in the inner magnetosphere of the Earth in the dipole model of the geomagnetic field taking into account ionospheric boundary conditions. The ionosphere is considered as a thin layer with finite conductivity. The eigenmode spectrum is discrete and consists of Alfvén, slow magnetosonic, flute and incompressible modes. Their interaction depends on ionospheric conductivity. The decay rate is small in noon and night sectors and large in dawn and dusk sectors. The lowest stability threshold α/γ ≈ 4.25 is determined by flute modes.     

Distribution and variability of accelerated electrons at Mars

We investigate accelerated electrons observed by Mars Global Surveyor (MGS), using data from the Electron Reflectometer (ER) instrument. We find three different types of accelerated electron events. Current sheet events occur over regions with weak or no crustal fields, have the highest electron energy fluxes, and are likely located on draped magnetotail fields. Extended events occur over regions with moderate crustal magnetic fields, and are most often observed on closed magnetic field lines. Localized events have the lowest energy fluxes, occur in strong magnetic cusp regions, and are the most likely kind of event to be found on open magnetic field lines. Some localized events have clear signatures of field-aligned currents; these events have much higher electron fluxes, and are preferentially observed on radially oriented open magnetic field lines. Electron acceleration events, especially localized events, are similar in many ways to events observed in the terrestrial auroral zone. However, physical processes related to those found in the terrestrial cusp and/or plasmasheet could also be responsible for accelerating electrons at Mars.     

Antiparticle content in the magnetosphere

In the present work we assess the stable and transient antiparticle content of planetary magnetospheres, and subsequently we consider their capture and application to high delta-v space propulsion. We estimate the total antiparticle mass contained within the Earth’s magnetosphere to assess the expediency of such usage. Using Earth’s magnetic field region as an example, we have considered the various source mechanisms that are applicable to a planetary magnetosphere, the confinement duration versus transport processes, and the antiparticle loss mechanisms. We have estimated the content of the trapped population of antiparticles magnetically confined following production in the exosphere due to nuclear interactions between high energy cosmic rays (CR) and constituents of the residual planetary upper atmosphere.The galactic antiprotons that directly penetrate into the Earth’s magnetosphere are themselves secondary by its nature, i.e. produced in nuclear reactions of the cosmic rays passing through the interstellar matter. These antiproton fluxes are modified, dependent on energy, when penetrating into the heliosphere and subsequently into planetary magnetospheres. During its lifetime in the Galaxy, CR pass through the small grammage of the interstellar matter where they produce secondary antiprotons. In contrast to this, antiprotons generated by the same CR in magnetosphere are locally produced at a path length of several tens g/cm² of matter in the ambient planetary upper atmosphere. Due to the latter process, the resulting magnetically confined fluxes significantly exceed the fluxes of the galactic antiprotons in the Earth’s vicinity by up to two orders of magnitude at some energies.The radiation belt antiparticles can possibly be extracted with an electromagnetic-based “scoop” device. The antiparticles could be concentrated by and then stored within the superimposed magnetic field structure of such a device. In future developments, it is anticipated that the energy of the captured antiparticles (both rest energy and kinetic energy) can be adapted for use as a fuel for propelling spacecraft to high velocities for remote solar system missions.     

Results from the ESA SREM monitors and comparison with existing radiation belt models

The Standard Radiation Environment Monitor (SREM) is a simple particle detector developed for wide application on ESA satellites. It measures high-energy protons and electrons of the space environment with a 20° angular resolution and limited spectral information. Of the ten SREMs that have been manufactured, four have so far flown. The first model on STRV-1c functioned well until an early spacecraft failure. The other three are on-board, the ESA spacecraft INTEGRAL, ROSETTA and PROBA-1. Another model is flying on GIOVE-B, launched in April 2008 with three L-2 science missions to follow: both Herschel and Planck in 2008, and GAIA in 2011). The diverse orbits of these spacecraft and the common calibration of the monitors provides a unique dataset covering a wide range of B-L* space, providing a direct comparison of the radiation levels in the belts at different locations, and the effects of geomagnetic shielding. Data from the PROBA/SREM and INTEGRAL/IREM are compared with existing radiation belt models.     

Solar modulation model with reentrant particles

We developed a one dimensional model of particle transport in the heliosphere. As opposite to widely used models, we apply a method where a quasi-particle is traced back in time. The model gives us the possibility to work on the possible existence of reentrant particles in the heliosphere that can be hardly solved by the traditional forward tracking method. Particles escape from the heliosphere and may reenter back. We estimate how these particles affect the modulation process in the heliosphere. Presented here are the results for different values of particles mean free path in the interstellar space and for different interstellar magnetic field values.     

The evolution of mirror type magnetic fluctuations in the magnetosheath based on multipoint observations

Two orbits were selected in January–February 2006 when the separation between the Cluster spacecraft was large and mirror type magnetic field fluctuations were observed by all spacecraft in different regions of the terrestrial magnetosheath. Minimum variance analysis was applied to find the mirror type fluctuations, and the amplitude of the fluctuations was determined individually. Mirror mode structures are moving along the streamlines frozen in the plasma. A model was developed for the calculation of plasma flowtime from the bow shock to the observation point. The growth rate of the field strength perturbations was estimated by comparing the amplitudes of fluctuations observed simultaneously at distant locations (∼10,000 km) based on the assumption that δB ∼ exp(γt). The obtained growth rate values were about an order of magnitude smaller than those provided by linear models and they decreased in the inner regions of the magnetosheath, indicating some saturation in the growth of the waves when proceeding towards the magnetopause. The results of these two case studies suggest that mirror type fluctuations originate from the compression region downstream of the quasi-perpendicular bow shock, and the growth of the fluctuations cannot be described by linear approximations.