Intermediate-term periodicities in the green corona brightness of the Sun

We have analysed intermediate-term periodicities in the green corona by dividing 10° latitudinal belts for the solar cycles 18, 19, and 20 (1947–1976). Discrete Fourier transform technique was used and three noticeable periodicities (3.48, 2.57, and 2.27 years) were found. The physical origin of these periods is not known, but evidence in our results exclude the possibility that the observed periods are a harmonic due to the method of analyse. The period of 3.48-year is the strongest one. 17.6-month periodicity was found only on around +40° belt while 155-day periodicity was not found in our analysis.     

The variability of foF2 in different phases of solar cycle 23

In this paper we examined the variations of the foF2 with solar activity for different local time and different seasons. Beside this we evaluated International Reference Ionosphere (IRI) models at different phases of solar cycle 23, different latitudes and different local time. We studied F2 layer critical frequency (foF2) of the ionosphere by using the flare index calculated by the Kandilli Observatory. For this purpose, we identified the months similar with high flare activity during the solar cycle 23. We chose 6 months which represented the different phases (ascending branch, maximum and descending branch) of the solar cycle. We also took into account the fact that these months were in different seasons. The hourly monthly means of observed foF2 data from four ionosonde stations for 6 months were calculated. On the other hand, the identical foF2 values of the same months were calculated for the year 1996, which is the minimum year of the previous solar activity cycle. We subtracted the foF2 values of 1996 from the values of the selected months of the last solar cycle to obtain the residuals, Δ(foF2). Then the magnitude of the residuals is compared through the cycle. We used IRI-2007 as well as IRI-2001 models to see the degree of deviation of the observed results from the predicted ones. We found that the predicted values of the ΔfoF2, which are calculated by the IRI-2007, fitted well with the observed Δ(foF2) and showed that the Δ(foF2) are dependent on the solar cycle variations in general.     

The 73-day periodicity of the flare index during the current solar cycle 22

The flare index of the current solar cycle 22 is analysed to detect periodicities. Power spectral analysis of the time series of solar flare index data reveals a periodicity around 73 and 53 days. We find that a periodicity of 73 days was in operation from November 1988 to the end of December 1991. We also find that when the 73-day periodicity or the 154-day periodicity is in operation the flare index is well correlated with the relative sunspot numbers.     

The good,the bad,and the ugly facts of tornado survival

Anytime that tornadoes interface with people, the results are often grim. The varied characteristics of tornado windfields and the diverse techniques of home construction complicate the expected outcomes of such interactions. Since it is now known that tornadoes do not produce unfathomable winds, engineers have developed techniques for increasing a home’s tornado resistance; thus, increasing the odds of survival of the inhabitants. Even considering these advances, tornadoes still wreak havoc and cause much causality every year. The story of tornado survival is partly chance, partly knowledge, and partly science. This essay utilizes analogies between a popular motion picture and the state of the art of tornado-resistant construction to illustrate the good, the bad, and the ugly facts of tornado survival. First examined are the positive aspects of tornado probability. The odds of experiencing a tornado are so low that massive expenditures are not necessarily cost effective. Next, various techniques of tornado-resistant construction practices are included for new and existing structures. Introduction of equations for predicting debris penetration are compared with various building techniques to describe the viability of tornado protection. The negative aspect of tornado/structure interfaces describes the fact that despite contemporary construction and prevention exercise, the unpredictability of the tornado windfield causes tremendous damage and loss of life. The final section examines the interface between tornadoes and mobile homes. This proves very ugly in every aspect of the word. Statistics and equations confirm the inherent dangers of such an interaction. Also, described is a novel approach to the design of a portable tornado shelter.     

Periodic behavior of solar flare index during solar cycles 20 and 21

Short-term periodicities of solar activity were studied with the flare index by using Discrete Fourier Transform for the time interval 1966–1986. Two noticeable periodicities (18.5 and 5 months) have been found. The existence of these periodicities comparing with the early findings is discussed.     

Distribution of LDE flares on the Sun during solar cycles 20 and 21

We have studied the latitude and longitude (northern and southern hemispheric) distributions based on 2277 LDE flares observed during the period from 1966 to 1986. We have found that there exist active zones, in which the LDE flare occurrence rate is much higher. Latitudinal belts between 11–20° and longitudinal belts around 80–100° are the most prolific places to produce LDE flares. During cycles 20 and 21 these active zones produced 36% of the total number of LDE flares by occupying only 6% area of the Sun.     

Physical Characteristics of Umbral Dots Derived from a High-Resolution Observations

Solar Physics - We study the features of the magnetic field variations within the 2011 June 7 eruptive event that includes a large filament eruption, a flare, and a CME formation. The magnetic...     

Biomonitoring of heavy metals by <Emphasis Type="Italic">Pseudevernia furfuracea</Emphasis> (L.) Zopf in Ankara (Turkey)

The objective of this study was to determine the air pollution level of Ankara and to generate the air pollution map of this city by using Pseudevernia furfuracea (L.) Zopf as a biomonitor. Lichen samples were collected from unpolluted area at Yaprakli Mountains, Cankiri in November 2002 and transplanted to 27 localities in Ankara. Lichen samples were retrieved following an exposure of 3 and 6 months. Heavy metal, Cu, Mn, Ni, Pb and Zn, contents were determined by using inductively coupled plasma spectrometry (ICP). The chlorophyll a and b contents were determined by using DMSO method. The increase in Ni, Pb, Zn and chlorophyll a content of the specimens were statistically important. All the increases and decreases in the variables could be explained by the environmental stress like pollution, but it is hard to say that this is the only reason of these changes, also climatic conditions, seasons, strength of the light and the physiological status of the plant itself effective on these changes. According to the results of heavy metal analysis Pseudevernia furfuracea continued to accumulate heavy metals and worked well as a biomonitor. The air pollution level of Ankara shows great variations because of the great area of the city.