Ionospheric disturbances at low and mid-low latitudes of the South American sector during the March 2015 great storm

This paper analyzes the response of the near equatorial and low latitude ionosphere of the South American sector to the geomagnetic storm occurred on 17 March 2015. Ionosonde data from Ramey (18.5° N, 292.9° E), Jicamarca (12.0° S, 283.2° E), Boa Vista (2.8° N, 299.3° E), Sao Luis (2.6° S, 315.8° E), Fortaleza (3.9° S, 321.6° E) and Cachoeira Paulista (22.7° S, 315.0° E) are used for the study. The results show negative disturbances in foF2 at low latitudes during the main phase of the storm, which were attributed to prompt penetration electric fields. Thus, the Equatorial Anomaly (EA) started to reduce their structure in this sector since on 17 March. During the recovery phase (on 18 March), positive disturbances were observed at low, mid-low latitudes (in the post-midnight – predawn hours), which can be mainly attributed to enhanced storm-time neutral winds and composition changes (i.e., increase in the O/N2 ratio). Disturbance dynamo electric fields would also contribute in modulating the electron density of the EA during this storm period.     

Thermosphere–ionosphere response to a severe magnetic storm: A case study

This paper reports the response of the ionosphere–thermosphere system to an intense geomagnetic storm. For that, data taken by instruments on board Dynamic Explorer 2 at heights of the F2-layer (molecular nitrogen N₂ and atomic oxygen O compositions, neutral temperature Tg and electron density Ne) were used. The ionospheric response is characterized by a negative storm effect expanding from mid–high to low latitude. It is observed during this severe geomagnetic storm that negative effects were caused mainly by an increase in molecular nitrogen composition N₂ and almost no changes in atomic oxygen composition O.     

Astrobiologically interesting stars within 10 parsecs of the sun

The existence of life based on carbon chemistry and water oceans relies upon planetary properties, chiefly climate stability, and stellar properties, such as mass, age, metallicity, and galactic orbits. The latter can be well constrained with present knowledge. We present a detailed, up-to-date compilation of the atmospheric parameters, chemical composition, multiplicity, and degree of chromospheric activity for the astrobiologically interesting solar-type stars within 10 parsecs of the Sun. We determined their state of evolution, masses, ages, and space velocities, and produced an optimized list of candidates that merit serious scientific consideration by the future space-based interferometry probes aimed at directly detecting Earthsized extrasolar planets and seeking spectroscopic infrared biomarkers as evidence of photosynthetic life. The initially selected stars number 33 solar-type within the total population (excluding some incompleteness for late M-dwarfs) of 182 stars closer than 10 parsecs. A comprehensive and detailed data compilation for these objects is still lacking; a considerable amount of recent data has so far gone unexplored in this context. We present 13 objects as the nearest "biostars," after eliminating multiple stars, young, chromospherically active, hard x-ray- emitting stars, and low metallicity objects. Three of these "biostars"-- Zeta Tucanae, Beta Canum Venaticorum, and 61 Virginis -- closely reproduce most of the solar properties and are considered as premier targets. We show that approximately 7% of the nearby stars are optimally interesting targets for exobiology.     

How the astronomical aspects of climate science were settled? On the Milankovitch and Bacsák anniversaries,with lessons for today

It was 100 years ago (on August 7, 1920), that the comprehensive mathematical foundations of climate change research, written by a Serbian researcher, Milutin Milankovitch, were published. A later interpreter and developer of his results, Georg (in Hungarian: György) Bacsák (Pozsony/Pressburg/Bratislava, June 5, 1870 - Fonyód, March 4, 1970) was born 150 years ago and died at the age of one hundred, half a century ago. In this commemorative paper we look back to special circumstances in revealing the secrets of ice ages that had puzzled scientists for at least several centuries. Recently, after 100 years, the Milankovitch theory, including related short-term forcings (ranging from interannual, multidecadal to millennial timescales) has not only been confirmed, but its climate forcing mechanism has also been identified and proposed. Owing to the uniqueness of the problem, the science of the orbital forcing of climate change can be proclaimed to be essentially settled.     

Ionospheric response to the 3 August 2010 geomagnetic storm at mid and mid-high latitudes

The global ionospheric response to the geomagnetic storm occurred of 3 August 2010 is studied in terms of the ionospheric parameter foF2. Data from three longitudinal sectors (Asia/Pacific, Europe/Africa and America) are considered. Some new aspects of the storm time ionospheric behavior are revealed. Results of the analysis show that the main ionospheric effects of the storm under consideration are: (a) prior to the storm, Japanese, Australian and American stations show increases in foF2, irrespective of the local time. (b) During the main phase, the stations of mid latitudes of the American sector show positive disturbances (in the pre-dusk hours), which subsequently change to negative. (c) During the recovery phase of the magnetic storm long-duration positive disturbances are observed at mid-low latitudes of the African chain. Also positive disturbances are observed in the Australian sector. In the European sector long-duration negative disturbances are seen at mid-high latitudes during the last part of the recovery phase while at mid-low latitudes a positive disturbance is seen, followed by a negative disturbance. In general, the ionospheric storm effects show a clear hemispheric asymmetry.     

Some ionospheric storm effects at equatorial and low latitudes

In this paper, the response of the equatorial and low latitude ionosphere to three intense geomagnetic storms occurred in 2002 and 2003 is reported. For that, critical frequency of F2-layer foF2 and the peak height hmF2 hmF2 for the stations Jicamarca (11.9°S), Ascension Is (7.92°S) and Tucuman (26.9°S) are used. The results show a “smoothing” of the Equatorial Anomaly structure during the development of the storms. Noticeable features are the increases in foF2 before the storm sudden commencement (SC) at equatorial latitudes and the southern crest of the Equatorial Anomaly. In some cases nearly simultaneous increases in foF2 are observed in response to the storm, which are attributed to the prompt electric field. Also, positive effects observed at equatorial and low latitudes during the development of the storm seem to be caused by the disturbance dynamo electric field due to the storm-time circulation. Increases in foF2 above the equator and simultaneous decreases in foF2 at the south crest near to the end of a long-duration main phase are attributed to equatorward-directed meridional winds. Decreases in foF2 observed during the recovery phase of storms are believed to be caused by composition changes. The results indicate that the prompt penetration electric field on the EA is important but their effect is of short lived. More significant ionospheric effects are the produced by the disturbance dynamo electric field. The role of storm-time winds is important because they modify the “fountain effect” and transport the composition changes toward low latitudes.     

Experimental evaluation of the radiative heat flux from rocket plumes on satellite structures

An experimental method capable of directly measuring the net radiant heat flux on complex geometry surfaces by non invasive methods has been devised, designed, realized and tested. The method is based on a computerized thermographic system capable of directly outputting the radiative heat fluxes absorbed by the surface to be examined. The calibration tests have shown the feasibility and the accuracy of the proposed method. Preliminary tests are presented which simulate the radiation flux from a jet exhaust.