Behaviour of the F1-region, and Esand spread-F phenomena at European middle latitudes, particularly under geomagnetic storm conditions

Knowledge of the ionospheric electron density distribution and its fluctuations is essential for predicting ionospheric characteristics for radio wave propagation and for other applications such as satellite tracking, navigation, etc. Geomagnetic storm is the most important source of the ionisation density perturbatio ns. Recent studies of the F1-region electron density distribution revealed systematic seasonal and latitudinal differences in the F1-layer response to geomagnetic storm. At European higher middle latitudes no significant effect has been observed in summer and spring at heights of 160-190 km, whereas well-pronounced depression appears in winter and late autumn at least at 180- 190 km. A brief interpretation of this finding will be presented. On the other hand, the pattern of the response of the ionosphere at F1-layer heights does not seem to depend on the type of response of F2-layer (foF2) or on solar activity. Concerning the main types of ionospheric irregularities sporadic E and spread-F, it has been found that considering sporadic E-layers as thin diffraction screen, it may be modelled for propagation of radio-waves by the determination of the temporal variation of foEs representing in ionograms the mean ion density of «patches» of increased ion density embedded in the Es-layer. Spectrum of these variations indicates the mean period of the variations, which multiplied by the wind velocity gives the mean distance of patches, that is, the mean distance between the screen points. In case of spread-F, it has been found that irregularities causing spread-F are mostly due to plasma instabilities, though the role of travelling ionospheric disturbances may be not entirely neglected

Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences and Countermeasures.

Circadian (∼ 24 hour) timing systems pervade all kingdoms of life, and temporally optimize behaviour and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behaviour and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these too are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally-driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioural and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important

Behaviour of the F1-region, and Esand spread-F phenomena at European middle latitudes, particularly under geomagnetic storm conditions

Knowledge of the ionospheric electron density distribution and its fluctuations is essential for predicting ionospheric characteristics for radio wave propagation and for other applications such as satellite tracking, navigation, etc. Geomagnetic storm is the most important source of the ionisation density perturbatio ns. Recent studies of the F1-region electron density distribution revealed systematic seasonal and latitudinal differences in the F1-layer response to geomagnetic storm. At European higher middle latitudes no significant effect has been observed in summer and spring at heights of 160-190 km, whereas well-pronounced depression appears in winter and late autumn at least at 180- 190 km. A brief interpretation of this finding will be presented. On the other hand, the pattern of the response of the ionosphere at F1-layer heights does not seem to depend on the type of response of F2-layer (foF2) or on solar activity. Concerning the main types of ionospheric irregularities sporadic E and spread-F, it has been found that considering sporadic E-layers as thin diffraction screen, it may be modelled for propagation of radio-waves by the determination of the temporal variation of foEs representing in ionograms the mean ion density of «patches» of increased ion density embedded in the Es-layer. Spectrum of these variations indicates the mean period of the variations, which multiplied by the wind velocity gives the mean distance of patches, that is, the mean distance between the screen points. In case of spread-F, it has been found that irregularities causing spread-F are mostly due to plasma instabilities, though the role of travelling ionospheric disturbances may be not entirely neglected

Effectiveness of the IRI-2001-predicted N(h) profile updating with real-time measurements under intense geomagnetic storm conditions over Europe

It is well known that as long as variations in the ionosphere follow regular patterns, the latest version of the International Reference Ionosphere IRI-2001 model estimates sufficiently accurate NmF2 and other parameters relevant for the ionospheric effects on radio wave propagation. During geomagnetic storms, it is desirable that for the IRI-2001 model to be tested against available observations. This paper presents the comparison of the IRI-2001-generated electron density (N(h)) profiles with those updated using measured values over European area during October and November 2003 geomagnetic super storms. Ionospheric stations involved in this study are Athens, Chilton, Rome, Juliusruh and Tromso. These stations provide real-time ionospheric characteristics and N(h) profiles regularly within the framework of the EU COST271 Action on ‘‘Effects of the upper atmosphere on terrestrial and earth-space communications’’. Comparative analysis shows that significant discrepancies do exist predominantly during the storm main phase. The model not always estimates correctly the phase and the magnitude of intense geomagnetic storm effects on the daytime F2 layer peak electron density at different European latitudes. Results are discussed in the context of real-time N(h) profile updating capabilities and effectiveness. 2006 COSPAR. Published by Elsevier Ltd. All rights reserved

Effectiveness of the IRI-2001-predicted N(h) profile updating with real-time measurements under intense geomagnetic storm conditions over Europe

It is well known that as long as variations in the ionosphere follow regular patterns, the latest version of the International Reference Ionosphere IRI-2001 model estimates sufficiently accurate NmF2 and other parameters relevant for the ionospheric effects on radio wave propagation. During geomagnetic storms, it is desirable that for the IRI-2001 model to be tested against available observations. This paper presents the comparison of the IRI-2001-generated electron density (N(h)) profiles with those updated using measured values over European area during October and November 2003 geomagnetic super storms. Ionospheric stations involved in this study are Athens, Chilton, Rome, Juliusruh and Tromso. These stations provide real-time ionospheric characteristics and N(h) profiles regularly within the framework of the EU COST271 Action on ‘‘Effects of the upper atmosphere on terrestrial and earth-space communications’’. Comparative analysis shows that significant discrepancies do exist predominantly during the storm main phase. The model not always estimates correctly the phase and the magnitude of intense geomagnetic storm effects on the daytime F2 layer peak electron density at different European latitudes. Results are discussed in the context of real-time N(h) profile updating capabilities and effectiveness. 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.Published1061–1068reserve

Effectiveness of the IRI-2001-predicted N(h) profile updating with real-time measurements under intense geomagnetic storm conditions over Europe

It is well known that as long as variations in the ionosphere follow regular patterns, the latest version of the International Reference Ionosphere IRI-2001 model estimates sufficiently accurate NmF2 and other parameters relevant for the ionospheric effects on radio wave propagation. During geomagnetic storms, it is desirable that for the IRI-2001 model to be tested against available observations. This paper presents the comparison of the IRI-2001-generated electron density (N(h)) profiles with those updated using measured values over European area during October and November 2003 geomagnetic super storms. Ionospheric stations involved in this study are Athens, Chilton, Rome, Juliusruh and Tromso. These stations provide real-time ionospheric characteristics and N(h) profiles regularly within the framework of the EU COST271 Action on ‘‘Effects of the upper atmosphere on terrestrial and earth-space communications’’. Comparative analysis shows that significant discrepancies do exist predominantly during the storm main phase. The model not always estimates correctly the phase and the magnitude of intense geomagnetic storm effects on the daytime F2 layer peak electron density at different European latitudes. Results are discussed in the context of real-time N(h) profile updating capabilities and effectiveness. 2006 COSPAR. Published by Elsevier Ltd. All rights reserved