Period Of Solar Cycle Research Articles

A deep learning model employing Bi-LSTM architecture to predict Martian ionosphere electron density using data from the Mars Global Surveyor mission

Planetary scientists and space agencies are highly intrigued by the Martian ionosphere due to its significant impact on upcoming Mars missions. Given its potential influence on satellite communication and navigation systems, measuring the altitude distribution of electron density (ED) values in the Martian ionosphere becomes a vital parameter to consider. The parameter of electron density in the Martian ionosphere serves as a tool to represent and predict the impacts of severe space weather events and solar activity on the Martian ionosphere. This study presents the development of a Bi-directional Long Short-Term Memory (Bi-LSTM) model, a deep machine learning algorithm to predict the Mars ionospheric ED values. To train and evaluate the model’s performance, we employ data samples from the Mars Global Surveyor (MGS) mission. For the preparation of input variables in the Bi-LSTM model, approximately 5600 ED altitude distribution of electron density profiles logged by the MGS between the years 1998 to 2005, which corresponded to the major period of the 23rd solar cycle, are taken into consideration. The performance of the proposed model in predicting both quiet and disturbed times is evaluated using the Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) metrics. The significant minimum values of MAE (0.56 × 109) and RMSE (0.67 × 109) for the quiet day considered and MAE (0.27 × 109) and RMSE (0.31 × 109) for the solar flare disturbed day considered indicate the fair performance of the Bi-LSTM based prediction model. This research’s findings are vital for upcoming Mars missions, as precise predictions of ED of Mars ionosphere are crucial for reliable navigation and communication systems.

Anomaly in the Diurnal Anisotropy During the Transition Period of Solar Cycles 24 and 25

Anomaly in the Diurnal Anisotropy During the Transition Period of Solar Cycles 24 and 25

Solar Wind Plasma Parameters in Relation with Good Quality Magnetic Cloud Related Geomagnetic Storms

We have analyzed magnetic cloud related geomagnetic storms detected during the period of solar cycle 23 and 24 with disturbances in solar wind plasma parameters. We have observed that all the MC related geomagnetic storms are accompanying with disturbances in solar wind plasma parameters. The magnitude of magnetic cloud related geomagnetic storms is soundly correlated with peak disturbances values of solar wind plasma parameters solar wind plasma velocity (SWPV), solar wind plasma density (SWPD), solar wind plasma temperature (SWPT), interplanetary magnetic fields (IMFB) and southward component of interplanetary magnetic fields (IMFBz). Large positive correlation with correlation coefficient 0.60 have found between magnitude of MC related GMS and peak value of related disturbances in IMFB and 0.67 between magnitude of MC related geomagnetic storms and peak value of associated disturbances in IMFBz. Additionally positive correlations with correlation coefficient 0.54 have been found between magnitude of MC related GMS and peak value of associated disturbances in solar wind plasma temperature ,0.40 between magnitude of MC related GMS and peak value of associated disturbances in solar wind plasma velocity, 0.27 between magnitude of MC related geomagnetic storms and peak value of disturbances in soar wind plasma density.

Temporal and Periodic Analysis of Penumbra–Umbra Ratio for the Last Four Solar Cycles

We investigate the long-term dynamic behavior of the sunspot penumbra to umbra area ratio by analyzing the Debrecen Photoheliographic Data (DPD) of sunspot groups during the period 1976–2017 (Solar Cycles 21–24). We consider all types of spots and find that the average penumbra–umbra ratio does not exhibit any significant variation with spot latitudes, solar-cycle phases as well as sunspot-cycle strengths. However, the behavior of this ratio is different when we consider the latitudinal distribution of the northern and southern hemispheres separately. Our analysis indicates that for daily total sunspot area the average spot ratio varies from 5.5 to 6.5 and for very large sunspots (> 5000 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\mu$\\end{document}Hem; one μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\mu$\\end{document}Hem is 10−6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$10^{-6}$\\end{document} the area of visual solar hemisphere) its value rises to about 8.3. In the case of the group-sunspot area, the average spot ratio is ∼6.76. Furthermore, we found that this ratio exhibits a trend for both smaller (area <100 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\mu$\\end{document}Hem) and large (area > 100 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\mu$\\end{document}Hem) sunspots. Finally, we report the periodic and quasiperiodic variations present in this ratio time series after applying the multitaper method (MTM) and Morlet-wavelet technique. We found that along with the ∼11-year solar-cycle period, the penumbra to umbra area ratio also shows several midterm variations, specifically, Rieger-type and quasibiennial periodicities. We also found that Rieger-type periods occur in all cycles, but the temporal evolution and the modulation of these types of periodicities are different in different solar cycles.

The differential rotation of the chromosphere and the quiet chromosphere in the falling and rising periods of a solar cycle

ABSTRACT The full-disc chromosphere was routinely monitored in the He i 10 830 Å line at the National Solar Observatory/Kitt Peak from 2004 November to 2013 March, and thereby, synoptic maps of He i line intensity from Carrington rotations 2032 to 2135 were acquired. They are utilized to investigate the differential rotation of the chromosphere and the quiet chromosphere during the one falling (descending part of solar cycle 23) period and the one rising (ascending part of solar cycle 24) period of a solar cycle. Both the quiet chromosphere and the chromosphere are found to rotate slower and have a more prominent differential rotation in the rising period of solar cycle 24 than in the falling period of solar cycle 23, and an illustration is offered.

Study of the Extensive Geomagnetic Storm with Helio-Spheric Phenomena during the Period of Solar Cycle 24

Study of the Extensive Geomagnetic Storm with Helio-Spheric Phenomena during the Period of Solar Cycle 24

Long-term equatorial ionosphere variations over Ethiopia

This paper focuses on the investigation of the long-term behavior of the equatorial ionosphere in Ethiopia. To explore the extended ionospheric variations, we analyze Total Electron Content (TEC) fluctuations in conjunction with solar activity indices, including F10.7 radio flux, EUV radiation, and Sunspot Number (SSN). The dataset used encompasses GPS-derived TEC records spanning 11 consecutive years from 2007 to 2017, corresponding to the period of solar cycle 24. Our analysis shows that the highest TEC levels generally occur during the post-noon hours, while the lowest values are observed around post-midnight or early morning. Notably, exceptions to this pattern are found in 2011 and 2013 when the highest TEC levels are observed during the December solstice. Otherwise, the seasonal TEC variation exhibits a semi-annual pattern, with peak TEC values occurring during the equinoxes and the lowest values during the solstices. Further examination demonstrates that in both solar activity phases, TEC magnitude is higher during the March Equinox compared to the September Equinox, and slightly higher during the December Solstice compared to the June Solstice. This reveals an asymmetry in the seasonal variations, encompassing the equinoxes, solstices, and the ascending and descending phases of the solar cycle. Our study confirms that long-term fluctuations in ionospheric TEC closely correspond to variations in solar activity indices. Correlation analysis indicates a strong link between all solar activity indices and TEC. Notably, while a negative correlation is observed in 2007, the correlation in 2011 is remarkably stronger. Additionally, we find that the long-term TEC variation exhibits stronger correlations with EUV and F10.7 radio flux than with SSN, with correlation coefficients of 0.86, 0.85, and 0.78, respectively. Lastly, our study extends previous research by identifying the long-term trends of vertical TEC (vTEC) in relation to various driving factors such as F10.7, SSN, and EUV.

The response of rhythmically forming processes to the latitudinal position of the zones of their implementation

The problem of variability of the Milankovich scale and cyclic oscillations in the troposphere circulation mode depending on the geographical latitude of the area is investigated. Parallels in the dynamics of multi-thousand-year and intra-century climate cycles in different latitudinal zones and possible causes of this phenomenon are considered. New data on the influence of axial rotation and the shape of the Earth on the structure of rhythm-forming processes are presented. It is established that the zone with a high frequency of pulsations of climatic phases is confined to low latitudes with the highest energy potential. The dependence of the velocity of air currents on the length of geographical parallels is shown. Thus, during the formation of air currents near the equator – the longest parallel of the planet (Hadley circulation cell), their velocity, which is set by the axial rotation of the Earth, is higher than the speed of sound and twice as high as similar flows originating in the temperate latitudes (Ferell cell). Paleogeographic evidence confirming Milankovich’s calculations about the different duration of the solar cycle period in the low, temperate and polar latitudes is presented. Thus, the dating of the terraces of the island of Barbados in the Caribbean Sea (low latitudes) showed that the period of the Milankovich cycle here is close to 20 thousand years. While in the zone of temperate latitudes, the period of the same cycle, judging by the dating of the stadial moraines of the former glacial covers, is 41 thousand years, i. e. twice as long. Maximum – up to 100 thousand years – set for polar latitudes in the study of the ice sheets of Antarctica and Greenland. Different degrees of meteorological impacts on ecosystems and the level of natural hazards within different latitudinal corridors have been revealed. The most dynamic and dangerous are the low latitudes with their hurricanes, typhoons, floods and storms with high frequency. This should be taken into account when developing a strategy for the economic development of high-risk territories and preventive measures for the protection of engineering orientation.

Solar Flux Effects on the Variations of Equatorial Electrojet (EEJ) and Counter-Electrojet (CEJ) Current across the Different Longitudinal Sectors during Low and High Solar Activity

This study examined the effect of solar flux (F10.7) and sunspots number (R) on the daily variation of equatorial electrojet (EEJ) and morning/afternoon counter electrojet (MCEJ/ACEJ) in the ionospheric E region across the eight longitudinal sectors during quiet days from January 2008 to December 2013. In particular, we focus on both minimum and maximum solar cycle of 24. For this purpose, we have collected a 6-year ground-based magnetic data from multiple stations to investigate EEJ/CEJ climatology in the Peruvian, Brazilian, West &amp; East African, Indian, Southeast Asian, Philippine, and Pacific sectors with the corresponding F10.7 and R data from satellites simultaneously. Our results reveal that the variations of monthly mean EEJ intensities were consistent with the variations of solar flux and sunspot number patterns of a cycle, further indicating that there is a significant seasonal and longitudinal dependence. During the high solar cycle period, F10.7 and R have shown a strong peak around equinoctial months, consequently, the strong daytime EEJs occurred in the Peruvian and Southeast Asian sectors followed by the Philippine regions throughout the years investigated. In those sectors, the correlation between the day Maxima EEJ and F10.7 strengths have a positive value during periods of high solar activity, and they have relatively higher values than the other sectors. A predominance of MCEJ occurrences is observed in the Brazilian (TTB), East African (AAE), and Peruvian (HUA) sectors. We have also observed the CEJ dependence on solar flux with an anti-correlation between ACEJ events and F10.7 are observed especially during a high solar cycle period.

Study of TEC Depletion during Low Solar Activity Periods of 23rd and 24th Solar Cycle at Crest of Indian EIA Region

Study of TEC Depletion during Low Solar Activity Periods of 23rd and 24th Solar Cycle at Crest of Indian EIA Region

Study of the Green Coronal Line with Altitude from Out-of-Eclipse Observations during Solar Cycle 24

The results of studies of the coronal emission line λ = 5303 Å (Fe XIV) for the period of solar cycle 24 are presented. The spectral data were obtained with an out-of-eclipse Lyot coronagraph at the Mountain Astronomical Station of the Pulkovo Observatory, Russian Academy of Sciences (near Kislovodsk). As a result of processing of out-of-eclipse observations, a database of three types of daily coronal maps of green line intensity I5303 was created with a height distribution h from 1R☉ to 1.38R☉ (R☉ is the radius of the Sun). Irregularities along the λ = 5303 Å line were found and identified, which were associated with the configuration of magnetic fields in the solar corona above active regions. The length of the green line from the position angle of the Sun was calculated. We have shown that the time distribution of the line length in the polar regions has two maxima, which coincide with the times of the reversal of the polar magnetic field on the Sun. The maximum values of the average length of the coronal line along the entire limb occur in 2012–2014. For different phases (the rise, the period of maximum, the decline, and the minimum solar activity) of this solar cycle and for different regions of solar activity, dependences of the height variations of the I5303 values were plotted and studied. The regression equations for these fitting curves are presented. The variation in I5303 with height for the polar regions is most likely determined by a logarithmic function, and the approximating trend curves for the remaining latitudinal zones are determined by a third-order power function.

Solar wind H+ fluxes at 1 AU for solar cycles 23 and 24

The solar wind consists of electrons and ion species having kinetic energy ≲10 keVs. Ion stream is mainly composed of protons. Their flux magnitude is especially important for radiation hardness assurance scientists who qualify materials for future space missions. Materials irreversibly degrade as soon as are exposed to solar radiation. Hence, proton differential and integral flux spectra play a crucial role in properly estimating radiation loads deposited within satellite functional components. Up to now, the wind fluxes were read out, e.g., from figures made for specific periods of a solar cycle. This method is not effective and is a source of a flux, and further on, a fluence uncertainty. The objective of this work was to calculate and tabulate the solar wind differential and integral proton fluxes, which can be used further on to evaluatespace mission proton fluence spectra. Solar wind proton bulk velocity and number density from four space solar observatories (SOHO, ACE, WIND, and DSCOVR) were numerically processed to achieve that goal. Fluxes were tabulated and represented in calendar year periods.Now, the radiation hardness assurance community can quickly access, compute and compare SW proton fluxes from different energy ranges, calendar years, and satellite data sources. Proton fluxes presented here indicate magnitude variations along with the solar cycle period. A correlation between the number of sunspots and the proton average flux was found, i.e., the larger the number of spots, the larger the flux magnitude. More importantly, it was discovered that proton fluxes indicate huge variations in magnitude for a selected year based on different satellite data sources. For some years, the difference reaches 240%. This value is reported for the first time and shows that to have a complete picture of the SW proton stream population, one must compare data from all four satellites. Also, it is reported that satellites, for a given calendar year, record different ranges of proton velocity and number density values. This finding, even stronger, suggests a necessity of comparing SW data from as many solar observatories as possible. The spread in the proton flux magnitude (240%) has a direct implication for planning and executing satellite material on-ground radiation test campaigns. Not carefully choosing a proton flux may result in a false impression of how examined material would degrade under an interplanetary space radiation environment. In this article, recommendations for selecting proper proton spectra are given.

Short-term Adaptive Forecast Model for TEC over equatorial low latitude region

In today's world, satellite navigation is one of the most widely used navigational aids, which is why accurate positioning is of critical importance. The ionosphere's Total Electron Content (TEC) is a significant contributor to the positional error in signal traveling between a satellite and the earth and reduces the system's positional accuracy. The ionosphere adds an excess delay to the radio wave traversing through it, resulting in position estimation error. Since the delay is a function of the ionospheric parameter TEC, estimation of TEC can help in correcting the errors. The challenge in estimating TEC in the equatorial region is that it exhibits a non-deterministic or unpredictable characteristic due to the complex electrodynamics resulting from Equatorial Ionospheric Anomaly (EIA). In addition, space weather phenomena like geomagnetic storms further disturb the ionosphere causing irregular short-term disturbances. This study explores the inherent VTEC pattern during geomagnetic storm conditions, especially during the high solar activity period, and proposes a short-term adaptive segmented regression model to forecast VTEC. The study is undertaken over six years of high solar activity period in the 24th solar cycle. The forecast model uses both linear and polynomial autoregression coefficients of recent past data. The model's performance is evaluated for extreme conditions, including the high solar activity and geomagnetic storms, which are the most challenging scenario for TEC prediction. The accuracy of the predicted output is calculated in terms of RMSE and correlation coefficient. The results were also compared with IRI 2016 model. The proposed short-term prediction model thus aims to help fill the precision required by long-term forecast models by considering near real-time nonlinear dynamics in the ionosphere.

Extracting Hale Cycle Related Components from Cosmic-Ray Data Using Principal Component Analysis

We decompose the monthly cosmic-ray data, using several neutron-monitor count rates, of Cycles 19 – 24 with principal component analysis (PCA). Using different cycle limits, we show that the first and second PC of cosmic-ray (CR) data explain 77 – 79% and 13 – 15% of the total variation of the Oulu CR Cycles 20 – 24 (C20 – C24), 73 – 77% and 13 – 17% of the variation of Hermanus C20 – C24, and 74 – 78% and 17 – 21% of the Climax C19 – C22, respectively. The PC1 time series of the CR Cycles 19 – 24 has only one peak in its power spectrum at the period 10.95 years, which is the average solar-cycle period for SC19 – SC24. The PC2 time series of the same cycles has a clear peak at period 21.90 (Hale cycle) and another peak at one third of that period with no peak at the solar-cycle period. We show that the PC2 of the CR is essential in explaining the differences in the intensities of the even and odd cycles of the CR. The odd cycles have a positive phase in the first half and a negative phase in the second half of their PC2. This leads to a slow decrease in intensity at the beginning of the cycle and a flat minimum for the odd cycles. On the contrary, for the even cycles the phases are reversed, and this leads to faster decrease and more rapid recovery of the CR intensity of the cycle. As a consequence, the even cycles have a more peak-like structure. These results are confirmed with skewness–kurtosis (S–K) analysis. Furthermore, S–K shows that other even and odd cycles, except Cycle 21, are on the regression line with a correlation coefficient 0.85. The Cycles 21 of all eight stations are compactly located in the S–K coordinate system and have smaller skewnesses and higher kurtoses than the odd Cycles 23.

Automatic Algorithm for Tracking Bipolar Magnetic Regions

AbstractProperties of bipolar magnetic regions (BMRs), particularly, the tilt angle play critical roles in generating the observed polar magnetic field and its reversal. Hence, a long-term study of BMR over its lifetime is crucial not only to understand the solar dynamo but also to identify the origin of the properties of BMR. In our work, we have developed an automatic algorithm to detect and track the BMRs from the line-of-sight (LOS) magnetograms of Michelson Doppler Imager (MDI) for the period of Solar Cycle 23 over its lifetime/disk passage. Here, we present the details of our algorithm and the features of BMR, particularly the tilt angle, magnetic field strength and lifetime.

Annual and Semiannual Variation in the Ionospheric F2-Layer Electron Density over the Indian Zone and Effect of Solar Activity on It

In situ measurement carried out by the Retarding potential Analyzer (RPA) on board SROSS C2 and ROCSAT during 1995 to 2003 covering ascending and descending periods of solar cycle 23 over Indian equatorial and low latitude were used to study the annual and semiannual variation of electron density at the topside F region. The ‘Semiannual anomaly’ which represent the electron density in equinox (March, April, September and October) is greater than that at solstice (May, June, July, August, November, December, January and February). The ‘annual anomaly’ which represents the electron density in winter (November, December, January, February) is higher than that in summer (May, June, July, August). The analysis has been carried out for the geomagnetic equator and ±10o magnetic latitudes. Observations reveal the existence of an equatorial asymmetry during daytime (10:00 – 14:00 hrs.) with higher electron density in spring (March, April) than in autumn (September, October) for both ascending and descending leg of the solar cycle. At the peak of the solar cycle, the density becomes equal for both equinoxes. Nighttime (22:00 – 00:00 hrs.) density in autumn is higher than that in spring for the ascending half of the solar cycle, becomes equal for both the equinoxes around the peak of the solar cycle. In the descending half the vernal density becomes higher than the autumnal density. The periodograms obtained from a Fourier analysis of the daytime average density shows that the annual variation is dominant over the semiannual variations for low to moderate solar activity whereas the semiannual peak becomes dominant over annual peak for high solar activity irrespective of the latitudes. At night, however, latitudinal differences have been observed. The annual variation is stronger than the semiannual variation at 10o N for low to moderate solar activity while for high solar activity the situation reverses. At 10o S and the magnetic equator, the annual variation is dominant for all levels of solar activity. Amplitude of the annual variation is higher in winter compared to that in summer. The physical and dynamical processes responsible for the observed annual and semi-annual trends in topside density will be identified and discussed.

Comparison of bottomside ionospheric profile parameters (B0 and B1) extracted from FORMOSAT-7/COSMIC-2 GNSS Radio occultations with Digisondes and IRI-2016 model

The bottomside thickness (B0) and shape (B1) are two important parameters considered in the bottomside electron density profile (EDP) specification of the International Reference Ionosphere (IRI) model that is the most widely accepted global empirical ionospheric model. In the present study, we investigated B0 and B1 as derived from least-square fitting of FORMOSAT-7/COSMIC-2 (F7/C2) radio occultation (RO) profiles by employing certain quality constraints in accordance to coincident Digisonde soundings. We performed a comparative analysis of the local time diurnal, seasonal and latitudinal behaviour of B0 and B1 parameters from a huge database of F7/C2 profiles accumulated during the last two years (2020 and 2021) with estimations from the IRI-2016 submodels: Bil-2000, Gul-1987, and ABT-2009, referring to the bottomside profile characteristics during the low solar activity period of 25th solar cycle. The results reveal daytime underestimation and nighttime overestimation features of IRI submodels. The typical pre-sunrise enhancement in B0 is clearly discernible in the F7/C2 observations which could not be reproduced in any of the IRI submodels. Moreover, the equatorial bottomside thickness anomaly (EBTA) presenting hemispheric asymmetry is not evidenced in the observed as well as modelled parameters. The sharp changeover in B0 magnitude from summer to winter solstice hemisphere and spring to fall equinox hemisphere in Gul-1987 indicates its inability to accurately represent the B0 variation at the equatorial and low latitude sector. Despite the fact that ABT-2009 performs relatively better than Gul-1987 sub-model based on F7/C2 and Digisonde datasets in different seasons, we demonstrate that there is room for possible improvement in terms of B0 and B1 representation.

Solar and interplanetary causes of x-class, x-ray solar flare related forbush decreases of higher magnitude in cosmic ray intensity during the period of solar cycle 23 and rising phase of solar cycle 24

Solar and interplanetary causes of x-class, x-ray solar flare related forbush decreases of higher magnitude in cosmic ray intensity during the period of solar cycle 23 and rising phase of solar cycle 24

Bayesian Solar Wind Modeling with Pulsar Timing Arrays

Abstract Using Bayesian analyses we study the solar electron density with the NANOGrav 11 yr pulsar timing array (PTA) data set. Our model of the solar wind is incorporated into a global fit starting from pulse times of arrival. We introduce new tools developed for this global fit, including analytic expressions for solar electron column densities and open source models for the solar wind that port into existing PTA software. We perform an ab initio recovery of various solar wind model parameters. We then demonstrate the richness of information about the solar electron density, n E , that can be gleaned from PTA data, including higher order corrections to the simple 1/r 2 model associated with a free-streaming wind (which are informative probes of coronal acceleration physics), quarterly binned measurements of n E and a continuous time-varying model for n E spanning approximately one solar cycle period. Finally, we discuss the importance of our model for chromatic noise mitigation in gravitational-wave analyses of pulsar timing data and the potential of developing synergies between sophisticated PTA solar electron density models and those developed by the solar physics community.

Relationship among Some Prevalent Diseases and Changes in Weather at Ilorin over a Solar Cycle Period

A study of the relationships existing between the variations in the tropospheric weather and occurrences of three prevalent diseases namely: typhoid, meningitis and asthma in Ilorin (lat. 8.5ºN and long. 4.5ºE), located within the Guinea savannah zone of West Africa have been carried out using data covering a period of eleven years (1999-2010; one solar cycle). Variations in five weather parameters namely, minimum temperature, maximum temperature, rainfall, relative humidity and sunshine hour were studied and used to determine the relationship of the diseases with changes in weather. The results showed that tropospheric weather is solar cycle dependent while the (three) diseases studied were found to be influenced by changes in weather to different extents. Hence they are seasonal dependent. Typhoid showed 97% dependence on maximum temperature, relative humidity and sunshine hours thus revealing that typhoid is promoted during dry season at Ilorin. Asthma occurrence showed 93% dependence on rainfall and minimum temperature therefore showing that it is prevalence during rainy season. The results also showed that meningitis occurrence with 95% of agreement with maximum temperature and relative humidity can have prevalence any time of the year irrespective of season.