Years Of Solar Activity Research Articles

Electron Density Reconstruction by Ionospheric Tomography From the Combination of GNSS and Upcoming LEO Constellations

AbstractComputerized ionospheric tomography (CIT) based on Global Navigation Satellite System (GNSS) data is a worthwhile project. However, predominant issues like unevenly distributed stations, lack of data, and high‐elevation GNSS signals could affect the precise information about the ionosphere. To address this problem, many previous studies were mainly improving tomographic algorithms, rather than incorporating multisource data such as data from rapidly developed upcoming Low‐Earth‐Orbit (LEO) satellites. In this paper, the potential improvements of GNSS‐based ionospheric tomography at a global scale by combining the upcoming LEO constellations is investigated. On this basis, some numerical experiments were conducted to evaluate the performances of LEO‐augmented GNSS ionospheric tomography. Specifically, the slant total electron contents (STEC) required for ionospheric tomography from ground receivers to GNSS (including GPS, GLONASS, BDS, and Galileo) and LEO satellites are simulated by the international reference ionosphere (IRI‐2016) model during low and high solar activity in 2018 and 2014, respectively. The simulated STEC values from single‐, double‐ and quad systems of GNSS constellations were first used for ionospheric tomography. Afterward, the GNSS‐based STEC values were combined with the LEO‐based simulated STEC values. The STEC values directly derived from the IRI‐2016 model that have not been used in ionospheric tomography were used as independent references. The results showed that the GNSS + LEO solutions outperform the GNSS‐only solutions overall, the STEC values obtained by GNSS + LEO solutions are more consistent with the STEC references during both high and low years of solar activity. In comparison with the STEC references, the RMS values of the CIT‐derived STEC for GNSS‐only solutions can be decreased by 15% and 20.3% at most during low and high years of solar activity, respectively.

Studying the winter anomaly with altimeter-derived TEC data

• This work presents of a new approach for using altimeter TEC data to study the ionospheric WA. • The outcomes agree with historical results on the locations of WA active regions. • A phenomenon leading to WA events during high solar activity was possibly identified. The ionospheric Winter Anomaly (WA) is a phenomenon discovered almost 100 years ago. It can be defined as the situations in which over a given location the winter ionization level is larger than the summer ionization level, for approximately the same solar activity conditions. Along the decades, a lot of studies have been carried out and relevant theories have been formulated to explain this phenomenon, but some aspects of the nature and physical principles of the WA are still a matter of discussion. The first objective of this work was to introduce a new technique for studying the WA, at any given location over the Oceans, based on the 27-year series of altimeter (TOPEX, Jason1, Jason 2 and Jason3 satellites)-derived Total Electron Content (TEC) data. The second objective of this work was to validate the new technique by presenting a comparative analysis between the results obtained with the new technique and those already published. This goal has been accomplished by studying the WA events over the 50°N and 50°S geographic parallels using the 27-year long altimeter data series. The results have indicated clear and systematic WA occurrences over the Northern Hemisphere and a more complex situation over the Southern Hemisphere, with two regions having different behaviors. These results are in full agreement with the findings published in relevant previous works. The last objective of this work was to present some original findings related to WA events. Taking advantage of the new technique, it has been shown that the WA might be interpreted as a high solar activity period consequence of a yearly periodic phenomenon. This phenomenon is always present, also during low solar activity years, even when WA effects are not visible. During winters over the Southern Hemisphere, it systematically produces (at any solar activity level) low maximum TEC values in the (180°E–360°E) longitudinal region and high maximum TEC values in the (0°E–180°E) longitudinal sector. Precisely, this last sector matches with the well-known region over which WA events are observed for high solar activity.

Analytic Representation of Illuminance on the Earth Surface with Different Types and Conditions of Cloud Cover over the 11-Year Solar Activity Cycle

The article describes the analytical expression approximating experimental data on daily natural illuminance on the Earth surface with different types and conditions of cloud cover over the 11-year solar activity cycle within the solar altitude angle range of 0 ° to 90 °. The values of the direct, diffused, and total illuminance on the Earth surface with different types and conditions of the cloud cover and, to some extent, of the substrate were defined and summarised in tables. The data presented may be used as part of the visual perception studies, light and engineering calculations, architecture and construction practice, etc.

The features of the bio-efficiency of geomagnetic activity on the sub-auroral latitiudes in the minimum of the 11-year solar cycle

There has been studied a bio-efficiency of geomagnetic variations in the sub-auroral latitudes (Yakutsk) in the minimum of the 24th 11-year solar cycle activity (2019) according to the parameters of the solar wind, Bz-components of interplanetary magnetic field, solar radiation with a wave length of 10.7 cm. There has been also analyzed a meteo factors’ impact (air temperature, air humidity, atmosphere pressure and wind velocity) in the given period. The condition of the cardiovascular system has been estimated daily (March-April of 2019) by a t-wave symmetry coefficient (TSC) in a phase portrait of the ECG. The research has been organized as a part of a simultaneous multi-latitude monitoring “Heliomed-2”. In the volunteers from sub-auroral latitudes there have not been revealed any disorders of the myocard repolarization in the minimum of the solar activity, according to the TSC in the electrocardiogram phase portrait. Cardio-sensitivity (myocard respond to more than 67% of the geomagnetic activity) has not been revealed in the volunteers. The cardiovascular system of the examinees from the sub-auroral latitudes responded only to 45.5% of the geomagnetic variations, most of which was characterized by high parameters of the solar wind dynamic pressure. Also, the respond of the myocard of the volunteers has been revealed to change of the atmospheric pressure, while temperature, air humidity and wind velocity did not impact the organism.

Scaling Features of Diurnal Variation of Galactic Cosmic Rays

We analyze the scaling properties of the diurnal variation of galactic cosmic rays (GCRs) in Solar Cycle 24 and the solar minima between Solar Cycles 23/24 and 24/25 for 2007 – 2019 based on the count rates of the Oulu, Newark, Hermanus, and Potchefstroom neutron monitors. The scaling features of the GCR diurnal variation are studied by evaluating the Hurst exponent, a quantitative parameter used as an indicator of the state of the randomness of a time series. We estimate the Hurst exponents for GCR diurnal-variation parameters amplitude and phase using structure-function and detrended-fluctuation-analysis methods. Results show that the Hurst exponents for the GCR diurnal variation vary in the range from approx0.3 to approx0.9, with a general tendency of being systematically above 0.5. It suggests that the GCR diurnal variation reveals a more persistent structure than Brownian motion. However, the time series of GCR diurnal-variation amplitude and phase evolve from a more persistent structure in the solar minimum between Solar Cycles 23/24 in 2007 – 2009 to a more random character in and near the solar maximum 2012 – 2014. This observation seems to be in agreement with the general configuration of the heliosphere through the 11-year solar-activity cycle. Moreover, the temporal profile of the Hurst exponent for GCR diurnal amplitude and phase around the beginning of the solar minimum between Solar Cycles 24/25 (2018 – 2019) differs from the solar minimum between Solar Cycles 23/24 in 2007 – 2009, suggesting a dependence on solar-magnetic polarity. These findings could shed more light on GCR particle transport in the turbulent heliosphere over the solar cycle.

RETRACTED ARTICLE: The abnormal precipitation in rainy season based on genetic algorithm and the security of big data in network

In this paper, cloudsim cloud simulation tool is studied, and its running environment is reasonably configured. Taking the platform as the background, the improved genetic algorithm proposed in this paper is used for simulation experiment that is to optimize the genetic algorithm through simulated annealing behavior. Through the simulation experiment of the improved genetic algorithm, it can be known that the genetic algorithm designed in this paper can satisfy multiple customers one by one and has a certain improvement effect on cloud service quality. In this paper, the problem of rainfall anomaly in city D is studied. The results show that the rainfall anomaly of city D is related to solar activity, 500hPa height field in winter and SST in the Central South Pacific from June to August of the previous year. It is found that there is almost no rainfall during the high solar activity years, while there is frequent rainfall near the low solar activity years. Finally, according to the homomorphic encryption mechanism, this paper studies the protection of data confidentiality in computer network security and the multistorage technology of big data. In this research scheme, by adding a certain number of virtual objects to two different computing information dummies, we successfully protect the data such as the number of items owned by the data owner, the content of the items owned, and the item objects called by the user. In addition, this paper uses bilinear mapping and RS coding technology to create related protocols to solve some problems, such as infinite verification of big data integrity, error data recovery, and protection of data owner’s computing resources. Through the design of solutions to the above problems, this paper successfully completed the protection of big data resources and network security based on cloud computing environment.

Assessing the performance of artificial neural networks to predict ionospheric TEC over Nigeria during different space weather events

The ionosphere model is essential to satellite-based systems to accurately correct the ionospheric error encountered by satellite signals en route. The Levenberg–Marquardt backpropagation (LMBP) algorithm in the artificial neural network (ANN) was used in this work to predict the total electron content (TEC) within the trough of equatorial ionization anomaly (EIA) over Nigeria. Two sets of data were used over the period of three consecutive years (2011–2013) of high solar activity. The first set was used as an input to the ANN model and the second set of data was used as a target. Seventy percent of the data sets were used to train the network, 15% of the data were used for validation, and 15% used for testing. The performance of the model was assessed during specific quiet and disturbed geomagnetic conditions. The regression analysis of the model output was optimized by minimizing a cost function of the mean square error (MSE). The results of the errors, regression, and comparative analyses have revealed that the ANN model is able to predict accurate and reliable TEC that compares well with the actual experimental data at any geophysical conditions. Hence, this model would be useful to forecast TEC over Nigeria to a reliable threshold.

Solar activity modulates the El Niño‐Southern Oscillation‐induced precipitation anomalies over southern China in early spring

AbstractThe present study identifies an evident solar cycle modulation upon the spatial pattern of the El Niño‐Southern Oscillation (ENSO) impact on the southern China precipitation in early spring (February–March). During high/low solar activity (HS/LS) years, the significant positive correlation between the wintertime Niño 3.4 index and the precipitation in the following early spring mainly locates at the southeastern China/Yangtze River Valley (SEC/YRV). Our analysis also suggests that the precipitation anomalies show asymmetries between ENSO warm and cold events under both solar phases. In HS years, the ENSO warm events‐related rainfall anomalies over the southern China are weak, but during the ENSO cold events significant dry anomalies appear at the SEC region. In LS years, significant wet anomalies over the YRV region are found during the ENSO warm events, whilst the rainfall anomalies are insignificant for the ENSO cold events. These modulations on precipitation are mediated by the changes in the ENSO‐associated anomalous western North Pacific anticyclone/cyclone, which may be attributed to the solar modulations on the ENSO‐associated sea surface temperature anomalies. Our results highlight that the level of solar activity should be taken into account when ENSO is used as a predictor for the precipitation over East Asia. [Correction added on 18 June 2021, after first online publication: The text for the abstract and graphical abstract were interchanged in the original‐published article. This updated version rectifies the error.]

Ionospheric variability during quiet and disturb geomagnetic conditions for low and high solar activity year

Present Paper describes analysis of GPS-data recorded at low latitude station Hyderabad (Geographic latitude 17 $$^\circ $$ , 25′ N, longitude 78 $$^\circ $$ , 33′ E), India to study the effect of magnetic activity on ionospheric TEC. The total electron content (TEC) data were considered for the ionosphere during five most quiet and most disturbed days for each month of the solar minimum year 2009 and the high solar activity year 2013. The results show that GPS-TEC is found to be more during disturbed days than that during quiet days with a maximum difference during the equinox season. In addition, the difference in TEC during quiet and disturbed days is found to be higher for solar maximum than that for solar minimum year. Moreover the GPS-TEC variations depend on the season with the maximum in equinox season and minimum in summer and winter season. Generally daytime TEC is found to be larger than that in the nighttime which is maximized around the local noontime hour but the peak formation delayed for the solar minimum year. The EIA development process during the solar minimum is quite slow and occurs in late afternoon as compared to that during the high solar activity year. In addition, this delay is larger for summer and winter season than that for equinox months. The formation of post sunset anomaly in the post-sunset sector (1900–2300 LT) is prominent during high solar activity year 2013 whereas same is insignificant for solar minimum year 2009. The post-sunset anomaly could be attributed to pre-reversal enhancement (PRE) of zonal electric field.

Captura de Langosta en Baja California y su relación con la Actividad Solar

Es creciente el interés por conocer los vínculos entre el comportamiento de la Actividad Solar (AS) y del Clima Espacial con numerosos procesos de la biosfera y en particular, los relacionados con la extracción de especies marinas. En este trabajo se relacionó la serie de tiempo anual (1959-2018) de captura de langosta por varias cooperativas pesqueras a lo largo de la Península de Baja California, México, con los ciclos multianuales de la AS, con el objetivo de revelar si se cumple la hipótesis de asociación entre estas variables. La relación estadística y análisis espectral entre las dos series muestran un marcado sincronismo entre las series de tiempo y la presencia en los volúmenes de captura del período principal de 11 años de la AS. Se explica la posible conexión AS-clima-océano con la variabilidad pesquera del crustáceo. Teniendo en cuenta los volúmenes de captura de langosta y la importancia económica que ello constituye para la región, se considera un aspecto importante para su posible aplicación práctica y explotación de este conocimiento en el marco de la tendencia en los ecosistemas debido a la variabilidad climática.
 Palabras claves: Clima Espacial, Clima, Producción Pesquera.

Improving DGNSS Performance through the Use of Network RTK Corrections

The differential global navigation satellite system (DGNSS) is an enhancement system that is widely used to improve the accuracy of single-frequency receivers. However, distance-dependent errors are not considered in conventional DGNSS, and DGNSS accuracy decreases when baseline length increases. In network real-time kinematic (RTK) positioning, distance-dependent errors are accurately modelled to enable ambiguity resolution on the user side, and standard Radio Technical Commission for Maritime Services (RTCM) formats have also been developed to describe the spatial characteristics of distance-dependent errors. However, the network RTK service was mainly developed for carrier-phase measurements on professional user receivers. The purpose of this study was to modify the local-area DGNSS through the use of network RTK corrections. Distance-dependent errors can be reduced, and accuracy for a longer baseline length can be improved. The results in the low-latitude areas showed that the accuracy of the modified DGNSS could be improved by more than 50% for a 17.9 km baseline during solar active years. The method in this paper extends the use of available network RTK corrections with high accuracy to normal local-area DGNSS applications.

Evidence for the Significant Differences in Response Times of Equatorial Ionization Anomaly Crest Corresponding to Plasma Fountains During Daytime and Post‐Sunset Hours

AbstractBased on 10 years' (2010–2019) of vertical total electron content (VTEC) data from Ahmedabad (23.0°N, 72.6°E, dip angle 35.2°) and campaign based OI 630.0 nm airglow intensity measurements from Mt. Abu (24.6°N, 72.7°E, dip angle 38.0°), it is shown that plasma density over the equatorial ionization anomaly (EIA) crest region increases in varying degrees during post‐sunset hours (2000–2100 LT) in magnetically quiet periods. The post‐sunset peak in VTEC precedes the corresponding peak in airglow intensity. By comparing post‐sunset VTEC enhancements with ionosonde observations from Tirunelveli (8.7°N, 77.7°E, dip angle 1.7°), it is shown that pre‐reversal enhancement (PRE) of the zonal electric field causes these enhancements over the EIA crest region. These observations are supported by TEC measurements by GAGAN (GPS Aided Geo Augmented navigation), the Indian Satellite‐based Augmentation System (SBAS). Comparison of average VTEC variations with global empirical model drifts reveals that the post‐sunset enhancements in VTEC occurs ∼1.7 h after the PRE and are significant only during December solstice and equinoctial months in high solar activity years similar to seasonal variations in PRE amplitudes. This time delay (response time of EIA crest) is almost half compared to the average response time (3–4 h) associated with the daytime fountain. Based on the latitudinal gradient in SBAS‐TEC, it is proposed that the PRE drives plasma from 5°N to 10°N magnetic latitudes to the EIA crest region leading to shorter response time. These results show the important role of the PRE in conditioning the EIA crest region.

Mechanism of cosmic ray high-energy particles charging test mass

The testing mass is the core sensor for measuring the spatial gravitational waves. The high-energy cosmic ray particles penetrating the outer structure of the spacecraft result in the electrical charges on the testing mass. The Coulomb force produced by the charges on the surrounding conducting surface and the Lorentz force generated by the motion through the interplanetary magnetic field will exert a serious influence on the geodesic motion of the testing mass. In this paper are investigated the process and mechanism of charging the testing mass by high-energy particles from different cosmic rays through using the Monte Carlo simulation method. It is concluded that the charging rate gradually increases with the decrease of cut-off energy under the same energy spectrum. The positive charging rate (elementary charges per second) in the years of minimum solar activity is predicted to be 39.5 +e/s, and the protons account for approximately 83.16% of the total quantity of galactic cosmic rays. The positive charging rate of the testing mass during the years of maximum solar activity is about 12.5 +e/s, and the charging rate of the testing mass of the worst solar energetic particle event in 1989 is about 120700 +e/s. The charging rate of the components of the galactic cosmic ray depends on the deposition of primary particles of each component in the testing mass during the years of minimum solar activity, with primary particles accounting for 73% of the total charging rate. The charging contribution of protons in years of minimum solar activity is mainly in an energy range of 0.1–1 GeV, accounting for about 65%. The research results can be used to assess the charging patterns of test quality on-orbit charges and provide a basis for designing the charge management and on-orbit work.

Solar Energetic Particle Event occurrence prediction using Solar Flare Soft X-ray measurements and Machine Learning

The prediction of the occurrence of Solar Energetic Particle (SEP) events has been investigated over many years, and multiple works have presented significant advances in this problem. The accurate and timely prediction of SEPs is of interest to the scientific community as well as mission designers, operators, and industrial partners due to the threat SEPs pose to satellites, spacecrafts, and crewed missions. In this work, we present a methodology for the prediction of SEPs from the soft X-rays of solar flares associated with SEPs that were measured in 1 AU. We use an expansive dataset covering 25 years of solar activity, 1988–2013, which includes thousands of flares and more than two hundred identified and catalogued SEPs. Neural networks are employed as the predictors in the model, providing probabilities for the occurrence or not of a SEP, which are converted to yes/no predictions. The neural networks are designed using current and state-of-the-art tools integrating recent advances in the machine learning field. The results of the methodology are extensively evaluated and validated using all the available data, and it is shown that we achieve very good levels of accuracy with correct SEP occurrence prediction higher than 85% and correct no-SEP predictions higher than 92%. Finally, we discuss further work towards potential improvements and the applicability of our model in real-life conditions.

Analysis of the correlation between horizontal wind and 11-year solar activity over Langfang, China

In this study, long term observations of medium frequency (MF) radar at Langfang site (39.4°N, 116.7°E) from 2009 to 2020 have been used to analyze the dependence of the 11-year solar cycle on horizontal winds in the local mesosphere and lower thermosphere (MLT). The results show that the zonal wind is positively correlated with solar activity during spring at 80–84 km, and during summer at 80–82 km; the meridional wind is positively correlated with solar activity during spring at 84–88 km and during summer at 84–90 km. In contrast, the results show no correlation between the horizontal wind and solar activity in autumn and winter. We attempt to explain the correlations in terms of the changes in stratospheric temperature and the net flux of gravity waves during solar activities. In addition, annual and semiannual oscillations of the zonal/meridional wind were found by using the least squares fitting method on daily horizontal winds, which show negative correlations with solar activity at heights of 80–90 km.

On the solar activity dependence of midnight equatorial plasma bubbles during June solstice periods

The occurrence of midnight Equatorial Plasma Bubbles (EPBs) during the June solstice period of the ascending phase of solar cycle 24, from 2010 to 2014, was studied using data from the 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang, Indonesia. The analysis shows that the occurrence of midnight hour EPBs was at its maximum during the low solar activity year 2010 and monotonically decreased thereafter with increasing solar activity. Details of the dependence of midnight hour EPB occurrence on solar activity were investigated using SAMI2 model simulation with a realistic input of <i><b>E</b></i> × <i><b>B</b></i> drift velocity data obtained from the CINDI-IVM onboard the C/NOFS satellite. Results obtained from term-by-term analysis of the flux tube integrated linear growth rate of RT instability indicate that the formation of a high flux tube electron content height gradient (steep vertical gradient) region at higher altitudes, due to the elevated F layer, is the key factor enhancing the growth rate of RT instability during low solar activity June solstices. Other factors are discussed in light of the relatively weak westward zonal electric field in the presence of the equatorward neutral wind and north-to-south transequatorial wind around the midnight hours of low solar activity June solstices. Also discussed are the initial seeding of RT instability by MSTIDs and how the threshold height required for EPB development varies with solar activity.

Variability of Weddell Sea ionospheric anomaly as deduced from observations at the Akademik Vernadsky station

Ionospheric Weddell Sea anomaly is an inversion of diurnal variation of the electron density in the ionosphere over Antarctic Peninsula, Weddell Sea, and neighbor territories observed during Antarctic summer. This paper aims at analyzing the reaction of the ionosphere during the Weddell Sea anomaly to changes in solar and geomagnetic activity as deduced from the data of vertical sounding of the ionosphere conducted at the Akademik Vernadsky station. The aim is achieved by comparing the monthly median values of the critical frequencies of the ionosphere (foF2) during Weddell Sea anomaly for the years of high and low solar activity; as well as by comparison of median December height-time diagrams (HT-diagrams) of foF2 calculated separately for the time intervals characterized by low or high levels of F10.7 and K indices for the period from 2007 till 2016. It was experimentally demonstrated that the Weddell Sea anomaly depends on the levels of solar ultraviolet flux and local K indices. The biggest nighttime maximum of ionization corresponds to low K indices and high values of F10.7. The most accurate inversion of diurnal variation of electron density in the F region is observed under the low values of K index and low F10.7 flux. The growth of geomagnetic activity decreases the nighttime ionization under both low and high levels of F10.7 fluxes and leads to a blur of the night maximum. Visible virtual heights of maximums increase together with F10.7 independently of the K index level. Blurring of the night maximum can be explained by destruction of the field of thermospheric winds supporting the nighttime anomaly, and/or by increasing role of plasma drifts in comparison with wind impact. The growth of visible virtual height of the nighttime maximum with increasing solar F10.7 flux could be explained by the gain of equatorward thermospheric wind with increasing solar ultraviolet flux that leads to growth of plasma upwelling effect. The Doppler frequency shift of the signals reflected from the ionosphere during nighttime in presence of the Weddell Sea anomaly is close to zero which could be explained by a stable F2 layer formed as a result of dynamic equilibrium between photochemical processes and upward plasma transport.

SOLAR-v: A new solar spectral irradiance dataset based on SOLAR/SOLSPEC observations during solar cycle 24

Context. Solar spectral irradiance (SSI) is the wavelength-dependent energy input to the top of the Earth’s atmosphere. Solar ultraviolet (UV) irradiance represents the primary forcing mechanism for the photochemistry, heating, and dynamics of the Earth’s atmosphere. Hence, both temporal and spectral variations in solar UV irradiance represent crucial inputs to the modeling and understanding of the behavior of the Earth’s atmosphere. Therefore, measuring the long-term solar UV irradiance variations over the 11-year solar activity cycle (and over longer timescales) is fundamental. Thus, each new solar spectral irradiance dataset based on long-term observations represents a major interest and can be used for further investigations of the long-term trend of solar activity and the construction of a homogeneous solar spectral irradiance record. Aims. The main objective of this article is to present a new solar spectral irradiance database (SOLAR-v) with the associated uncertainties. This dataset is based on solar UV irradiance observations (165−300 nm) of the SOLAR/SOLSPEC space-based instrument, which provides measurements of the full-disk SSI during solar cycle 24. Methods. SOLAR/SOLSPEC made solar acquisitions between April 5, 2008 and February 10, 2017. During this period, the instrument was affected by the harsh space environment that introduces instrumental trends (degradation) in the SSI measurements. A new method based on an adaptation of the Multiple Same-Irradiance-Level (MuSIL) technique was used to separate solar variability and any uncorrected instrumental trends in the SOLAR/SOLSPEC UV irradiance measurements. Results. A new method for correcting degradation has been applied to the SOLAR/SOLSPEC UV irradiance records to provide new solar cycle variability results during solar cycle 24. Irradiances are reported at a mean solar distance of 1 astronomical unit (AU). In the 165−242 nm spectral region, the SOLAR/SOLSPEC data agrees with the observations (SORCE/SOLSTICE) and models (SATIRE-S, NRLSSI 2) to within the 1-sigma error envelope. Between 242 and 300 nm, SOLAR/SOLSPEC agrees only with the models.

The post sunset equatorial F- region zonal drift variability and its linkage with equatorial spread F onset and duration over Indian longitudes

The seasonal and solar activity variation of the post sunset F- region zonal plasma drift, at the magnetic equatorial region over Indian longitudes is analyzed using the Republic of China Satellite-1 data from January 2000 to April 2004. The post sunset F- region zonal drifts are observed to be higher in the years of high solar activity in comparison with low solar activity, while seasonally the drifts are minimum in summer with much higher values in other seasons. The seasonal and solar activity variations of zonal plasma drift are attributed to the corresponding variations in the neutral winds. The dependences of the F region peak vertical drift on the zonal plasma drift at 18.5 IST (Indian Standard Time) and the time difference of the conjugate points sunset times, are quantitatively analyzed. Further an integrated parameter (incorporating the above mentioned two independent factors), which is able to predict the peak vertical drift and growth rate of Rayleigh Taylor instability is proposed. The other major outcome of the study is the successful prediction of the Equatorial Spread F (ESF) onset time and duration using the new integrated parameter at 18.5 IST. ESF irregularities and associated scintillations adversely affect communication and navigation systems. Hence, the present methodology for the prediction of the characteristics of these nocturnal irregularities becomes relevant.

Criteria for early prediction of geomagnetic disturbances caused by coronal holes during periods of low solar activity based on muon flux variations

Coronal holes generate a high speed solar wind. This wind is the cause of magnetic storms on the Earth during the years of low solar activity. Also a high speed solar wind creates disturbances in the interplanetary magnetic field. The disturbance may reflect cosmic rays hitting them in the direction of the Earth. As a result, it is possible to observe a change in the flux of cosmic rays on the Earth before the arrival of the disturbance. The paper identifies a criterion for early detection of cosmic ray flux increasing by the muon hodoscope URAGAN (MEPhI, Moscow) to coronal holes in years of decreased solar activity (2009-2010, 2018-2019). It was found that increases of cosmic ray intensity are visible before the main sequence of areas of increasing and decreasing cosmic ray intensities in GSE maps in 60% of the cases.