Science.gov

Sample records for aa geomagnetic index

  1. An update on the correlation between the cosmic radiation intensity and the geomagnetic AA index

    NASA Technical Reports Server (NTRS)

    Shea, M. A.; Smart, D. F.

    1985-01-01

    A statistical study between the cosmic ray intensity, as observed by a neutron monitor, and of the geomagnetic aa index, as representative of perturbations in the plasma and interplanetary magnetic field in the heliosphere, has been updated to specifically exclude time periods around the reversal of the solar magnetic field. The results of this study show a strong negative correlation for the period 1960 through 1968 with a correlation coefficient of approximately -0.86. However, there is essentially no correlation between the cosmic ray intensity and the aa index for the period 1972-1979 (i.e. correlation coefficient less than 0.16). These results would appear to support the theory of preferential particle propagation into the heliosphere vis the ecliptic during the period 1960-1968 and via the solar polar regions during 1972-1979.

  2. Long-term biases in geomagnetic K and aa indices

    USGS Publications Warehouse

    Love, J.J.

    2011-01-01

    Analysis is made of the geomagnetic-activity aa index and its source K-index data from groups of ground-based observatories in Britain, and Australia, 1868.0-2009.0, solar cycles 11-23. The K data show persistent biases, especially for high (low) K-activity levels at British (Australian) observatories. From examination of multiple subsets of the K data we infer that the biases are not predominantly the result of changes in observatory location, localized induced magnetotelluric currents, changes in magnetometer technology, or the modernization of K-value estimation methods. Instead, the biases appear to be artifacts of the latitude-dependent scaling used to assign K values to particular local levels of geomagnetic activity. The biases are not effectively removed by weighting factors used to estimate aa. We show that long-term averages of the aa index, such as annual averages, are dominated by medium-level geomagnetic activity levels having K values of 3 and 4. ?? 2011 Author(s).

  3. A combined solar and geomagnetic index for thermospheric climate

    PubMed Central

    Mlynczak, Martin G; Hunt, Linda A; Marshall, B Thomas; Russell, James M; Mertens, Christopher J; Thompson, R Earl; Gordley, Larry L

    2015-01-01

    Infrared radiation from nitric oxide (NO) at 5.3 µm is a primary mechanism by which the thermosphere cools to space. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite has been measuring thermospheric cooling by NO for over 13 years. In this letter we show that the SABER time series of globally integrated infrared power (watts) radiated by NO can be replicated accurately by a multiple linear regression fit using the F10.7, Ap, and Dst indices. This allows reconstruction of the NO power time series back nearly 70 years with extant databases of these indices. The relative roles of solar ultraviolet and geomagnetic processes in determining the NO cooling are derived and shown to vary significantly over the solar cycle. The NO power is a fundamental integral constraint on the thermospheric climate, and the time series presented here can be used to test upper atmosphere models over seven different solar cycles. Key Points F10.7, Ap, and Dst replicate time series of radiative cooling by nitric oxide Quantified relative roles of solar irradiance, geomagnetism in radiative cooling Establish a new index and extend record of thermospheric cooling back 70 years PMID:26709319

  4. Homogenization of the historical records of geomagnetic field components and geomagnetic K-index of the Magnetic Observatory of Coimbra

    NASA Astrophysics Data System (ADS)

    Morozova, Anna; Ribeiro, Paulo; Pais, M. Alexandra

    2013-04-01

    The Coimbra Magnetic Observatory (COI) (Portugal) has a long history of observation of the geomagnetic field, spanning almost 150 years. Measurements of the geomagnetic field components started in 1866 and include the observations of all components: horizontal (H), downward vertical (Z), northward (X), eastward (Y), total field magnitude (F), inclination (I) and declination (D). These long instrumental geomagnetic records provide very important information about variability of measured parameters, their trends and cycles, and can be used to improve our knowledge on the sources that drive variations of the geomagnetic field: liquid core dynamics (internal) and solar forcing (external). However, during the long life of the Coimbra observatory, some inevitable changes in station location, instrument's park and electromagnetic environment took place. These changes affected the quality of the data causing breaks and jumps in the series. Clearly, these inhomogeneities, typically of shift-like (step-like) or trend-like, have to be corrected or, at least, minimized in order for the data to be used in scientific studies or to be submitted to international databases. The homogenization of the monthly and annual averages of geomagnetic field components has been done using visual and statistical tests (e.g. standard normal homogeneity test), allowing to estimate not only the level of inhomogeneity of the studied series, but also to detect the highly probable homogeneity break points. These have been compared with the metadata, reference series from the nearest geomagnetic stations and geomagnetic field models (e.g. CM4 and CHAOS3) in order to find and to set up the indispensable correction factors. Similar methods have been applied to the homogenization of the local geomagnetic K-index series (from 1952 to 2012). As a result, the homogenized geomagnetic monthly and annual averages of the series measured in COI are considered to be essentially free of artificial shifts and ready to be used by the scientific community.

  5. Correcting the geomagnetic IHV index of the Eskdalemuir observatory

    NASA Astrophysics Data System (ADS)

    Martini, D.; Mursula, K.

    2006-12-01

    We study here the recently proposed measure of local geomagnetic activity called the IHV (Inter-Hour Variability) index calculated for the Eskdalemuir (ESK) station. It was found earlier that the ESK IHV index depicts an artificial, step-like increase from 1931 to 1932. We show here that this increase is due to the fact that the values of the magnetic field components of the ESK observatory stored at the World Data Center are two-hour running averages of hourly data stored in ESK yearbooks. Two-hour averaging greatly reduces the variability of the data which leads to artificially small values of the IHV index in 1911-1931. We also study the effect of two-hour averaging upon hourly mean and spot values using 1-minute data available for recent years, and calculate the correction factors for the early years, taking into account the weak dependence of correction factors on solar activity. Using these correction factors, we correct the ESK IHV indices in 1912-1931, and revise the estimate of the centennial change based on them. The effect of correction is very significant: the centennial increase in the ESK IHV-raw (IHV-cor) index in 1912-2000 changes from 73.9% (134.4%) before correction to 10.3% (25.3%) thereafter, making the centennial increase at ESK quite similar to other mid-latitude stations. Obviously, earlier long-term studies based on ESK IHV values are affected by the correction and need to be revised. These results also strongly suggest that the ESK yearbook data should be digitized and the hourly ESK data at WDC should be replaced by them.

  6. A New Polar Magnetic Index of Geomagnetic Activity and its Application to Monitoring Ionospheric Parameters

    NASA Technical Reports Server (NTRS)

    Lyatsky, Wladislaw; Khazanov, George V.

    2008-01-01

    For improving the reliability of Space Weather prediction, we developed a new, Polar Magnetic (PM) index of geomagnetic activity, which shows high correlation with both upstream solar wind data and related events in the magnetosphere and ionosphere. Similarly to the existing polar cap PC index, the new, PM index was computed from data from two near-pole geomagnetic observatories; however, the method for computing the PM index is different. The high correlation of the PM index with both solar wind data and events in Geospace environment makes possible to improve significantly forecasting geomagnetic disturbances and such important parameters as the cross-polar-cap voltage and global Joule heating in high latitude ionosphere, which play an important role in the development of geomagnetic, ionospheric and thermospheric disturbances. We tested the PM index for 10-year period (1995-2004). The correlation between PM index and upstream solar wind data for these years is very high (the average correlation coefficient R approximately equal to 0.86). The PM index also shows the high correlation with the cross-polar-cap voltage and hemispheric Joule heating (the correlation coefficient between the actual and predicted values of these parameters is approximately 0.9), which results in significant increasing the prediction reliability of these parameters. Using the PM index of geomagnetic activity provides a significant increase in the forecasting reliability of geomagnetic disturbances and related events in Geospace environment. The PM index may be also used as an important input parameter in modeling ionospheric, magnetospheric, and thermospheric processes.

  7. Study of the Relationship Between Forbush Decrease and Geomagnetic Storm Events Using Dst Index.

    NASA Astrophysics Data System (ADS)

    Dominic, Obiegbuna; Okeke, Fransisca; Okpala, Kingsley

    Abstract A study of the relationship between Forbush decreases (FD) and geomagnetic storms have been carried out using the Dst index. Most important space weather effects including FDs are associated with geomagnetic disturbances (storms). The rigidity cut off of cosmic rays, is related to the latitude of measurement and are affected by geomagnetic disturbances. Four (4) stations hosted by the Bartol research institute, University of Delaware provided continuous CR counts for this study. Clear signatures of Forbush decreases associated with storms happening on days of Kp >7 from 1980-1989 were examined to deduce the level of modulation of CR counts during geomagnetic storms. Enhancement of the count rates are observed during simultaneous Forbush decreases associated with large storms. FD correlated well with Dst for all of the stations with no significant difference observed with regards to rigidity. The anomalous enhancement during the simultaneous FD showed stronger association depending on rigidity and the implications of these results

  8. A combined solar and geomagnetic index for thermospheric climate

    NASA Astrophysics Data System (ADS)

    Hunt, Linda A.; Mlynczak, Martin G.

    2015-04-01

    Infrared radiation from nitric oxide (NO) at 5.3 ?m is a primary mechanism by which the thermosphere cools to space. The SABER instrument on the NASA TIMED satellite has been measuring thermospheric cooling by NO for over 13 years. Physically, changes in NO emission are due to changes in temperature, atomic oxygen, and the NO density. These physical changes however are driven by changes in solar irradiance and changes in geomagnetic conditions. We show that the SABER time series of globally integrated infrared power (Watts) radiated by NO can be replicated accurately by a multiple linear regression fit using the F10.7, Ap, and Dst indices. This fit enables several fundamental properties of NO cooling to be determined as well as their variability with time, permitting reconstruction of the NO power time series back nearly 70 years with extant databases of these indices. The relative roles of solar ultraviolet and geomagnetic processes in determining the NO cooling are derived and shown to be solar cycle dependent. This reconstruction provides a long-term time series of an integral radiative constraint on thermospheric climate that can be used to test climate models.

  9. A combined solar and geomagnetic index for thermospheric climate

    NASA Astrophysics Data System (ADS)

    Mlynczak, Martin G.; Hunt, Linda A.; Marshall, B. Thomas; Russell, James M.; Mertens, Christopher J.; Thompson, R. Earl; Gordley, Larry L.

    2015-05-01

    Infrared radiation from nitric oxide (NO) at 5.3 m is a primary mechanism by which the thermosphere cools to space. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite has been measuring thermospheric cooling by NO for over 13 years. In this letter we show that the SABER time series of globally integrated infrared power (watts) radiated by NO can be replicated accurately by a multiple linear regression fit using the F10.7, Ap, and Dst indices. This allows reconstruction of the NO power time series back nearly 70 years with extant databases of these indices. The relative roles of solar ultraviolet and geomagnetic processes in determining the NO cooling are derived and shown to vary significantly over the solar cycle. The NO power is a fundamental integral constraint on the thermospheric climate, and the time series presented here can be used to test upper atmosphere models over seven different solar cycles.

  10. Evaluation of a new paleosecular variation activity index as a diagnostic tool for geomagnetic field variations

    NASA Astrophysics Data System (ADS)

    Panovska, Sanja; Constable, Catherine

    2015-04-01

    Geomagnetic indices like Dst, K and A, have been used since the early twentieth century to characterize activity in the external part of the modern geomagnetic field and as a diagnostic for space weather. These indices reflect regional and global activity and serve as a proxy for associated physical processes. However, no such tools are yet available for the internal geomagnetic field driven by the geodynamo in Earth's liquid outer core. To some extent this reflects limited spatial and temporal sampling for longer timescales associated with paleomagnetic secular variation, but recent efforts in both paleomagnetic data gathering and modeling activity suggest that longer term characterization of the internal geomagnetic weather/climate and its variability would be useful. Specifically, we propose an index for activity in paleosecular variation, useful as both a local and global measure of field stability during so-called normal secular variation and as a means of identifying more extreme behavior associated with geomagnetic excursions and reversals. To date, geomagnetic excursions have been identified by virtual geomagnetic poles (VGPs) deviating more than some conventional limit from the geographic pole (often 45 degrees), and/or by periods of significant intensity drops below some critical value, for example 50% of the present-day field. We seek to establish a quantitative definition of excursions in paleomagnetic records by searching for synchronous directional deviations and lows in relative paleointensity. We combine paleointensity variations with deviations from the expected geocentric axial dipole (GAD) inclination in a single parameter, which we call the paleosecular variation (PSV) activity index. This new diagnostic can be used on any geomagnetic time series (individual data records, model predictions, spherical harmonic coefficients, etc.) to characterize the level of paleosecular variation activity, find excursions, or even study incipient reversals. Currently reversals can only be detected after they have occurred. A baseline for the new index is established using modern and Holocene geomagnetic field data and models to analyze 'normal' variability. We extend our analyses to the 100 ka interval where several excursions have been identified. We discuss the diminished or absent signatures of excursions in some records, the apparent transgressive behavior of detected excursions, and implications for transitional field behavior. The absence of specific excursions in some sediment records is attributed to smoothing by the sedimentary remanence acquisition process and low sedimentation rates. Overall PSV activity index is inversely correlated with dipole moment, indicating stronger impacts of non-axial-dipole secular variations during periods of low axial dipole strength. Excursional events found with the PSV activity index are analyzed in the context of global probability density functions for VGP positions. We studied the appearance of VGP clusters of the excursions to find the common characteristics of these instabilities, including the non-axial dipole features of the geomagnetic field. A better understanding of geomagnetic excursions will aid attempts to predict when such events might occur in the future.

  11. Comparison of K-index Calculations between Several Geomagnetic Stations during IQDs and IDDs

    NASA Astrophysics Data System (ADS)

    Hwang, Junga; Kim, Hang-Pyo; Park, Young-Deuk

    2013-09-01

    BOH magnetometer was installed at Mt. Bohyun in 2007 and has provided continuous dataset for 3-axis geomagnetic field over the South Korea. We have calculated real-time K-index based on BOH magnetic field data using well-known FMI method. Local K-index is calculated eight times a day, per every three hours. To calculate K-index, it is critical to get the Quiet Day Curve (QDC). For QDC calculation, we take the previous one month's average of H-component. In this paper, we compared four geomagnetic stations' magnetic field data over South Korea and Japan and K-indices of each stations; Bohyun, Gangneung, Jeju, and Kakioka for two years data, 2011-2012. To investigate the difference depending on the latitude, longitude and local time in more detail, we compare K-index on International Quiet Days (IQDs) and International Disturbed Days (IDDs). As a result, we report the correlation between local K-indices are higher than those between Kp and local K-indices, and the correlation is much better after sunset than after sunrise. As the geomagnetic activity becomes stronger, the correlation between the local K-indices and global Kp-index become higher.

  12. Forecasting geomagnetic sctivity of Dst index using radial basis function networks

    NASA Astrophysics Data System (ADS)

    Wei, H. L.; Billings, S. A.; Zhu, D. Q.; Balikhin, M. A.

    The magnetosphere can be considered as a complex input-output system For such a system the solar wind plays the role of the input and the geomagnetic indices can be considered as outputs The Dst index is used to measure the disturbance of the geomagnetic field in the magnetic storms Numerous studies of correlations between the solar wind parameters and magnetospheric disturbances show that the product of the solar wind velocity V and the southward component of the magnetic field quantified by Bs represents the input that can be considered as the input to the magnetosphere This multiplied input will be denoted by VB s Many approaches have been proposed to analyse the Dst and other geomagnetic activity indices Input-output observational data-based modelling approaches provides a powerful tool for forecasting geomagnetic activities for example the prediction of the Dst index Radial basis function RBF networks as a special class of single hidden-layer feedforward neural networks have been proved to be universal approximators One advantage of RBF networks compared with multi-layer perceptrons MLP is that the linearly weighted structure of RBF networks where parameters in the units of the hidden layer can often be pre-fixed can be easily trained with a fast speed without involving nonlinear optimization Another advantage of RBF networks compared with other basis function networks is that each basis function in the hidden units is a nonlinear mapping which maps a multivariable input to a

  13. Periodic variation in the geomagnetic activity - A study based on the Ap index

    NASA Technical Reports Server (NTRS)

    De Gonzalez, Alicia L. C.; Gonzalez, Walter D.; Dutra, Severino L. G.; Tsurutani, Bruce T.

    1993-01-01

    The monthly and daily samples of the Ap index for the interval from 1932 through 1982 were studied using the power spectrum technique. Results obtained for Bartel's period (about 27 days), the semiannual period, the dual-peak solar cycle distribution of geomagnetic storms, and certain other medium-scale periodicities are examined in detail. In addition, results on the cumulative occurrence number of storms per decade as a function of the Ap and Dst indices for the storm are presented.

  14. Forecasting the geomagnetic activity of the Dst index using multiscale radial basis function networks

    NASA Astrophysics Data System (ADS)

    Wei, H. L.; Zhu, D. Q.; Billings, S. A.; Balikhin, M. A.

    The Dst index is a key parameter which characterises the disturbance of the geomagnetic field in magnetic storms. Modelling of the Dst index is thus very important for the analysis of the geomagnetic field. A data-based modelling approach, aimed at obtaining efficient models from limited input-output observational data, provides a powerful tool for analysing and forecasting geomagnetic activities including the prediction of the Dst index. In this study, the process of the Dst index is treated to be a structure-unknown system, where the solar wind parameter ( VBs) and the solar wind dynamic pressure ( P) are the system inputs, and the Dst index is the system output. A novel multiscale RBF (MSRBF) network is introduced to represent such a two-input and single-output system, where the Dst index is related to the solar wind parameter and the dynamic pressure, via a hybrid network model consisting of two submodels: a linear part that reflects the linear relationship between the output and the inputs, and a nonlinear part that captures the effect of the interacting contribution of past observations of the inputs and the output, on the current output. The proposed MSRBF network can easily be converted into a linear-in-the-parameters form and the training of the linear network model can easily be implemented using a forward orthogonal regression (FOR) algorithm. One advantage of the new MSRBF network, compared with traditional single scale RBF networks, is that the new network is more flexible for describing complex nonlinear dynamical systems.

  15. Variations of Geomagnetic Dst-index and Seismicity at Northern Tien-Shan

    NASA Astrophysics Data System (ADS)

    Kairatkyzy, Dina; Khachikyan, Galina; Zhumabayev, Beibit

    2015-04-01

    On the Northern Tien-Shan in the recent past there have been several catastrophic earthquakes: Verny (June 8, 1887, 23:35 UT, 43.1N, 76.8E, M = 7.3); Chilic (July 11, 1889, 22:14 UT, 43.2N, 78.7E, M = 8.3); Kemin (January 3, 1911, 23:25 UT, M = 8.2). Because of such strong events are possible here in the future, the search for earthquake precursors for this area is relevant. Some years ago, Sobolev and Zakrzhevskaya [2003] http://adsabs.harvard.edu/abs/2003EAEJA......135S have revealed an influence of geomagnetic storms on seismicity. They showed, in particular, that in Northern Tien-Shan the number of earthquakes increases within a few days after the sudden onset of geomagnetic storm (SSC). In our work, we attempted to identify the image-signal of seismic precursor in variations of geomagnetic Dst-index, which describes geomagnetic storm. Data on earthquakes with K=>11.0 occurred in area 42.8-43.5N, 76-78E in 1970-2010 (23 events) have been analyzed. Time of earthquake occurrence was taken as a "key event". Using the superposed epoch method, the averaged distribution of hourly Dst values was obtained for 480 hours before and 480 hours after a key event. It is found that a precursor image-signal has a pattern of geomagnetic storm with clear evident both the sudden onset, main and recovery phases as well. Earthquakes with K=>11.0 tend to occur at recovery phase about of 12 days after the sudden onset. The results confirmed earlier findings by Sobolev and Zakrzhevskaya [2003] and can be used for prediction of strong earthquakes in Northern Tien-Shan.

  16. Coincident 1.3-year Periodicities in the ap Geomagnetic Index and the Solar Wind

    NASA Technical Reports Server (NTRS)

    Paularena, K. I.; Szabo, A.; Richardson, J. D.

    1995-01-01

    Recent observations show an approximately 1.3-year period in the speed of the solar wind detected by the IMP 8 and Voyager 2 spacecraft. A similar period is also seen in the north-south (GSE) component of the magnetic field observed by IMP 8. Since both parameters are commonly used as input to models of geomagnetic activity, the 'ap' index (a measure of geomagnetic disturbance) is examined to look for this periodicity. The Lomb-Scargle periodogram method is used on the ap, plasma, and magnetic field data during the 1973-1994 time range. A dynamic FFT periodogram method is also used to analyze the ap data during this time, as well as to look for periods present between 1932 and 1972. A clear 1.3-year periodicity is present in the post-1986 data when the same period is observed in the plasma and field data. The V(2)B(zsm) and V(2)B(s) proxies for geomagnetic activity also show this periodicity. However, the southward (GSM) component of the magnetic field does not have a 1.3-year period, and neither do solar wind or ap data from 1973-1985. This demonstrates that the ap geomagnetic index can act as a proxy for solar wind periodicities at this time scale. Historic ap data are examined, and show that a similar periodicity in ap exists around 1942. Since auroral data show a 1.4-year periodicity, all these similar periods may result from a common underlying solar mechanism.

  17. The Dst index underestimates the solar cycle variation of geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Temerin, Michael; Li, Xinlin

    2015-07-01

    It is known that the correction of the Kyoto Dst index for the secular variation of the Earth's internal field produces a discontinuity in the Kyoto Dst index at the end of each year. We show that this secular correction also introduces a significant baseline error to the Kyoto Dst index that leads to an underestimate of the solar cycle variation of geomagnetic activity and of the strength of the ring current as measured by the Kyoto Dst index. Thus, the average value of the Kyoto Dst index would be approximately 13 nT more negative for the active year 2003 compared to quiet years 2006 and 2009 if the Kyoto Dst index properly measured the effects of the ring current and other currents that influence the Dst observatories. Discontinuities in the Kyoto Dst index at the end of each year have an average value of about 5 nT, but the discontinuity at the end of year 2002 was approximately 12 nT, and the discontinuity at the end of year 1982 may have been as large as 20 nT.

  18. Forecasting geomagnetic activity indices using the Boyle index through artificial neural networks

    NASA Astrophysics Data System (ADS)

    Balasubramanian, Ramkumar

    2010-11-01

    Adverse space weather conditions affect various sectors making both human lives and technologies highly susceptible. This dissertation introduces a new set of algorithms suitable for short term space weather forecasts with an enhanced lead-time and better accuracy in predicting Kp, Dst and the AE index over some leading models. Kp is a 3-hour averaged global geomagnetic activity index good for midlatitude regions. The Dst index, an hourly index calculated using four ground based magnetic field measurements near the equator, measures the energy of the Earth's ring current. The Auroral Electrojet indices or AE indices are hourly indices used to characterize the global geomagnetic activity in the auroral zone. Our algorithms can predict these indices purely from the solar wind data with lead times up to 6 hours. We have trained and tested an ANN (Artificial Neural Network) over a complete solar cycle to serve this purpose. Over the last couple of decades, ANNs have been successful for temporal prediction problems amongst other advanced non-linear techniques. Our ANN-based algorithms receive near-real-time inputs either from ACE (Advanced Composition Explorer), located at L1, and a handful of ground-based magnetometers or only from ACE. The Boyle potential, phi = 10-4 (vkm/sec)2+ 11.7BnT sin3 (theta/2) kV, or the Boyle Index (BI) is an empirically-derived formula that approximates the Earth's polar cap potential and is easily derivable in real time using the solar wind data from ACE. The logarithms of both 3-hour and 1-hour averages of the Boyle Index correlate well with the subsequent Kp, Dst and AE: Kp = 8.93 log 10 - 12.55. Dst = 0.355 - 6.48, and AE = 5.87 - 83.46. Inputs to our ANN models have greatly benefitted from the BI and its proven record as a forecasting parameter since its initiation in October, 2003. A preconditioning event tunes the magnetosphere to a specific state before an impending geomagnetic storm. The neural net not only improves the predictions but also helps the prediction by capturing the influence of preconditioning. Two of our models have been running in near-real-time forecast mode already, and the BI and Kp predictions can be obtained from http://space.rice.edu/ISTP/wind.html.

  19. AE Geomagnetic Index Predictability for High Speed Solar Wind Streams: A Wavelet Decomposition Technique

    NASA Technical Reports Server (NTRS)

    Guarnieri, Fernando L.; Tsurutani, Bruce T.; Hajra, Rajkumar; Echer, Ezequiel; Gonzalez, Walter D.; Mannucci, Anthony J.

    2014-01-01

    High speed solar wind streams cause geomagnetic activity at Earth. In this study we have applied a wavelet interactive filtering and reconstruction technique on the solar wind magnetic field components and AE index series to allowed us to investigate the relationship between the two. The IMF Bz component was found as the most significant solar wind parameter responsible by the control of the AE activity. Assuming magnetic reconnection associated to southward directed Bz is the main mechanism transferring energy into the magnetosphere, we adjust parameters to forecast the AE index. The adjusted routine is able to forecast AE, based only on the Bz measured at the L1 Lagrangian point. This gives a prediction approximately 30-70 minutes in advance of the actual geomagnetic activity. The correlation coefficient between the observed AE data and the forecasted series reached values higher than 0.90. In some cases the forecast reproduced particularities observed in the signal very well.The high correlation values observed and the high efficacy of the forecasting can be taken as a confirmation that reconnection is the main physical mechanism responsible for the energy transfer during HILDCAAs. The study also shows that the IMF Bz component low frequencies are most important for AE prediction.

  20. Analysis of precursors of tropical cyclogenesis during different phases of the solar cycle and their correlation with the Dst geomagnetic index

    NASA Astrophysics Data System (ADS)

    Pazos, Marni; Mendoza, Blanca; Gimeno, Luis

    2015-10-01

    Three tropical cyclogenesis precursors, (absolute vorticity, relative humidity, vertical shear)and, the combined Genesis Potential Index are investigated in order to analyse their behaviour during three different phases(descending, minimum and ascending) of the solar cycle. The correlation between these tropical cyclogenesis precursors and the Dst geomagnetic index is also assessed, with the main finding being that the correlations between both the Genesis Potential Index and the vertical shear with the Dst index are statistically significant. This result suggests that the relationship between geomagnetic activity and tropical cyclones might be modulated by the influence of geomagnetic activity on the vertical wind shear.

  1. Statistical Technique for Intermediate and Long-Range Estimation of 13-Month Smoothed Solar Flux and Geomagnetic Index

    NASA Technical Reports Server (NTRS)

    Niehuss, K. O.; Euler, H. C., Jr.; Vaughan, W. W.

    1996-01-01

    This report documents the Marshall Space Flight Center (MSFC) 13-month smoothed solar flux (F(sub 10.7)) and geomagnetic index (A(sub p)) intermediate (months) and long-range (years) statistical estimation technique, referred to as the MSFC Lagrangian Linear Regression Technique (MLLRT). Estimates of future solar activity are needed as updated input to upper atmosphere density models used for satellite and spacecraft orbital lifetime predictions. An assessment of the MLLRT computer program's products is provided for 5-year periods from the date estimates were made. This was accomplished for a number of past solar cycles.

  2. A method to predict thermospheric mass density response to geomagnetic disturbances using time-integrated auroral electrojet index

    NASA Astrophysics Data System (ADS)

    Iipponen, Juho; Laitinen, Tiera

    2015-07-01

    Using the thermospheric mass density measurements from the European Space Agency's Gravity field and steady state Ocean Circulation Explorer (GOCE) satellite, we develop a new empirical geomagnetic disturbance time correction based on integrating the auroral electrojet (AE) index. For this, a US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar (NRLMSISE-00) model with no geomagnetic parametrization is subtracted from the GOCE densities, and the regressions between the time-integrated AE index and density residuals are computed as a function of latitude, solar time, and day of year. When we add this correction to the quiet time reference NRLMSISE-00 model, it increases the model's disturbance time correlation with the 270 km normalized GOCE densities from 0.71 to 0.86. We assess the effect of integrating thermospheric density proxies with respect to time using both geomagnetic and solar indices and discover that the integration of AE, ap, and the epsilon parameter significantly increase their correlation with the orbit-averaged GOCE densities. We compare the predictions of our empirical correction with the NRLMSISE-00 and Jacchia-Bowman (JB2008) models, and significant deviations from the measurements are discovered. The NRLMSISE-00 is confirmed to generally underestimate the density enhancement, and the latitudinal shape of the predicted response shows too low enhancements at middle latitudes. Even though these are not issues for the JB2008 model, it performs weaker than the NRLMSISE-00 at reproducing the orbit-averaged densities. This unexpected result is attributed to the weakness of the ap parametrization, which is used in the model during smaller disturbances.

  3. Schizophrenia and season of birth: relationship to geomagnetic storms.

    PubMed

    Kay, Ronald W

    2004-01-01

    An excess pattern of winter and spring birth, of those later diagnosed as schizophrenic, has been clearly identified in most Northern Hemisphere samples with none or lesser variation in Equatorial or Southern Hemisphere samples. Pregnancy and birth complications, seasonal variations in light, weather, temperature, nutrition, toxins, body chemistry and gene expression have all been hypothesized as possible causes. In this study, the hypothesis was tested that seasonal variation in the geomagnetic field of the earth primarily as a result of geomagnetic storms (GMS) at crucial periods in intrauterine brain development, during months 2 to 7 of gestation could affect the later rate of development of schizophrenia. The biological plausibility of this hypothesis is also briefly reviewed. A sample of eight representative published studies of schizophrenic monthly birth variation were compared with averaged geomagnetic disturbance using two global indices (AA*) and (aa). Three samples showed a significant negative correlation to both geomagnetic indices, a further three a significant negative correlation to one of the geomagnetic indices, one showed no significant correlation to either index and one showed a significant positive correlation to one index. It is suggested that these findings are all consistent with the hypothesis and that geomagnetic disturbance or factors associated with this disturbance should be further investigated in birth seasonality studies. PMID:14693348

  4. Superposed epoch analysis and storm statistics from 25 years of the global geomagnetic disturbance index, USGS-Dst

    USGS Publications Warehouse

    Gannon, J.L.

    2012-01-01

    Statistics on geomagnetic storms with minima below -50 nanoTesla are compiled using a 25-year span of the 1-minute resolution disturbance index, U.S. Geological Survey Dst. A sudden commencement, main phase minimum, and time between the two has a magnitude of 35 nanoTesla, -100 nanoTesla, and 12 hours, respectively, at the 50th percentile level. The cumulative distribution functions for each of these features are presented. Correlation between sudden commencement magnitude and main phase magnitude is shown to be low. Small, medium, and large storm templates at the 33rd, 50th, and 90th percentile are presented and compared to real examples. In addition, the relative occurrence of rates of change in Dst are presented.

  5. Assessing the validity of station location assumptions made in the calculation of the geomagnetic disturbance index, Dst

    USGS Publications Warehouse

    Gannon, Jennifer

    2012-01-01

    In this paper, the effects of the assumptions made in the calculation of the Dst index with regard to longitude sampling, hemisphere bias, and latitude correction are explored. The insights gained from this study will allow operational users to better understand the local implications of the Dst index and will lead to future index formulations that are more physically motivated. We recompute the index using 12 longitudinally spaced low-latitude stations, including the traditional 4 (in Honolulu, Kakioka, San Juan, and Hermanus), and compare it to the standard United States Geological Survey definitive Dst. We look at the hemisphere balance by comparing stations at equal geomagnetic latitudes in the Northern and Southern hemispheres. We further separate the 12-station time series into two hemispheric indices and find that there are measurable differences in the traditional Dst formulation due to the undersampling of the Southern Hemisphere in comparison with the Northern Hemisphere. To analyze the effect of latitude correction, we plot latitudinal variation in a disturbance observed during the year 2005 using two separate longitudinal observatory chains. We separate these by activity level and find that while the traditional cosine form fits the latitudinal distributions well for low levels of activity, at higher levels of disturbance the cosine form does not fit the observed variation. This suggests that the traditional latitude scaling is insufficient during active times. The effect of the Northern Hemisphere bias and the inadequate latitude scaling is such that the standard correction underestimates the true disturbance by 10–30 nT for storms of main phase magnitude deviation greater than 150 nT in the traditional Dst index.

  6. Solar-Terrestrial Coupling Evidenced by Periodic Behavior in Geomagnetic Indexes and the Infrared Energy Budget of the Thermosphere

    NASA Technical Reports Server (NTRS)

    Mlynczak, Martin G.; Martin-Torres, F. Javier; Mertens, Christopher J.; Marshall, B. Thomas; Thompson, R. Earl; Kozyra, Janet U.; Remsberg, Ellis E.; Gordley, Larry L.; Russell, James M.; Woods, Thomas

    2008-01-01

    We examine time series of the daily global power (W) radiated by carbon dioxide (at 15 microns) and by nitric oxide (at 5.3 microns) from the Earth s thermosphere between 100 km and 200 km altitude. Also examined is a time series of the daily absorbed solar ultraviolet power in the same altitude region in the wavelength span 0 to 175 nm. The infrared data are derived from the SABER instrument and the solar data are derived from the SEE instrument, both on the NASA TIMED satellite. The time series cover nearly 5 years from 2002 through 2006. The infrared and solar time series exhibit a decrease in radiated and absorbed power consistent with the declining phase of the current 11-year solar cycle. The infrared time series also exhibits high frequency variations that are not evident in the solar power time series. Spectral analysis shows a statistically significant 9-day periodicity in the infrared data but not in the solar data. A very strong 9-day periodicity is also found to exist in the time series of daily A(sub p) and K(sub p) geomagnetic indexes. These 9-day periodicities are linked to the recurrence of coronal holes on the Sun. These results demonstrate a direct coupling between the upper atmosphere of the Sun and the infrared energy budget of the thermosphere.

  7. Solar-terrestrial coupling evidenced by periodic behavior in geomagnetic indexes and the infrared energy budget of the thermosphere

    NASA Astrophysics Data System (ADS)

    Mlynczak, Martin G.; Martin-Torres, F. Javier; Mertens, Christopher J.; Marshall, B. Thomas; Thompson, R. Earl; Kozyra, Janet U.; Remsberg, Ellis E.; Gordley, Larry L.; Russell, James M.; Woods, Thomas

    2008-03-01

    We examine time series of the daily global power (W) radiated by carbon dioxide (at 15 ?m) and by nitric oxide (at 5.3 ?m) from the Earth's thermosphere between 100 km and 200 km altitude. Also examined is a time series of the daily absorbed solar ultraviolet power in the same altitude region in the wavelength span 0 to 175 nm. The infrared data are derived from the SABER instrument and the solar data are derived from the SEE instrument, both on the NASA TIMED satellite. The time series cover nearly 5 years from 2002 through 2006. The infrared and solar time series exhibit a decrease in radiated and absorbed power consistent with the declining phase of the current 11-year solar cycle. The infrared time series also exhibits high frequency variations that are not evident in the solar power time series. Spectral analysis shows a statistically significant 9-day periodicity in the infrared data but not in the solar data. A very strong 9-day periodicity is also found to exist in the time series of daily Ap and Kp geomagnetic indexes. These 9-day periodicities are linked to the recurrence of coronal holes on the Sun. These results demonstrate a direct coupling between the upper atmosphere of the Sun and the infrared energy budget of the thermosphere.

  8. Wind-stress effect on the relationships between sea surface temperature and geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Kirichenko, K. E.; Belousova, E. P.; Kovalenko, V. A.

    2015-11-01

    This paper deals with possible causes of broken relationships between geomagnetic activity (GA) and sea surface temperature (SST) in the regions where it is most prominent. We analyze data of 0/700 m ocean heat content, SST, and wind stress for the period 1948-2013. The aa index is used to describe geomagnetic activity. The zonal wind stress is demonstrated to have a significant effect on sea surface temperature in the regions under consideration. Increased fluctuations of heat content anomalies and change in wind stress structure have been noted since the 1976 climate shift.

  9. Analysis of Ionospheric Electron Parameters in Relation to the Geomagnetic Index Dst and Solar F10.7 Flux from RO Data of FORMOSAT-3/COSMIC

    NASA Astrophysics Data System (ADS)

    Wang, K.; Tam, S. W.

    2009-12-01

    The FORMOSAT-3/COSMIC mission launched in 2006 has provided globally-distributed radio occultation profiles for the ionosphere and atmosphere. Utilizing this advantage, we statistically analyze how the ionospheric electron parameters NmF2, hmF2, and TEC react to the geomagnetic activities and solar activities at different magnetic latitudes and magnetic local time (MLT) based on these data. The responses to geomagnetic index Dst and its changing rate dDst/dt at both quiet and storm time are investigated based on these data of two years from August of 2006 to July of 2008. The results indicate that, in general, the NmF2, hmF2 and TEC decrease as Dst increases at all seasons at the low-latitude dayside regions. During the main phase of a storm, this region can expand to higher latitudes. Only during the sudden commencement phase (SSC) of storm events, NmF2 and TEC generally increase as Dst increases. On the other hand, the investigation results on response to the solar F10.7 flux shows that the extent of variation of these ionospheric parameters may have considerable regional differences.

  10. Geomagnetism during solar cycle 23: Characteristics.

    PubMed

    Zerbo, Jean-Louis; Amory-Mazaudier, Christine; Ouattara, Frdric

    2013-05-01

    On the basis of more than 48years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 1996-2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3nT) and yearly averaged solar wind speed (364km/s) are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568km/s), associated to the highest value of the yearly averaged aa index (37nT). We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century) study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum. PMID:25685427

  11. Geomagnetism during solar cycle 23: Characteristics

    PubMed Central

    Zerbo, Jean-Louis; Amory-Mazaudier, Christine; Ouattara, Frdric

    2012-01-01

    On the basis of more than 48years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 19962009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3nT) and yearly averaged solar wind speed (364km/s) are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568km/s), associated to the highest value of the yearly averaged aa index (37nT). We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century) study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum. PMID:25685427

  12. On the statistics of El Nino occurrences and the relationship of El Nino to volcanic and solar/geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    1989-01-01

    El Nino is conventionally defined as an anomalous and persistent warming of the waters off the coasts of Ecuador and Peru in the eastern equatorial Pacific, having onset usually in Southern Hemispheric summer/fall. Some of the statistical aspects of El Nino occurrences are examined, especially as they relate to the normal distribution and to possible associations with volcanic, solar, and geomagnetic activity. With regard to the very strong El Nino of 1982 to 1983, it is noted that, although it may very well be related to the 1982 eruptions of El Chichon, the event occurred essentially on time (with respect to the past behavior of elapsed times between successive El Nino events; a moderate-to-stronger El Nino was expected during the interval 1978 to 1982, assuming that El Nino occurrences are normally distributed, having a mean elapsed time between successive onsets of 4 years and a standard deviation of 2 years and a last known occurrence in 1976). Also, although not widely recognized, the whole of 1982 was a record year for geomagnetic activity (based on the aa geomagnetic index, with the aa index registering an all time high in February 1982), perhaps, important for determining a possible trigger for this and other El Nino events. A major feature is an extensive bibliography (325 entries) on El Nino and volcanic-solar-geomagnetic effects on climate. Also, included is a tabular listing of the 94 major volcanic eruptions of 1835 to 1986.

  13. On the Relationship between Solar Wind Speed, Earthward-Directed Coronal Mass Ejections, Geomagnetic Activity, and the Sunspot Cycle Using 12-Month Moving Averages

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    For 1996 .2006 (cycle 23), 12-month moving averages of the aa geomagnetic index strongly correlate (r = 0.92) with 12-month moving averages of solar wind speed, and 12-month moving averages of the number of coronal mass ejections (CMEs) (halo and partial halo events) strongly correlate (r = 0.87) with 12-month moving averages of sunspot number. In particular, the minimum (15.8, September/October 1997) and maximum (38.0, August 2003) values of the aa geomagnetic index occur simultaneously with the minimum (376 km/s) and maximum (547 km/s) solar wind speeds, both being strongly correlated with the following recurrent component (due to high-speed streams). The large peak of aa geomagnetic activity in cycle 23, the largest on record, spans the interval late 2002 to mid 2004 and is associated with a decreased number of halo and partial halo CMEs, whereas the smaller secondary peak of early 2005 seems to be associated with a slight rebound in the number of halo and partial halo CMEs. Based on the observed aaM during the declining portion of cycle 23, RM for cycle 24 is predicted to be larger than average, being about 168+/-60 (the 90% prediction interval), whereas based on the expected aam for cycle 24 (greater than or equal to 14.6), RM for cycle 24 should measure greater than or equal to 118+/-30, yielding an overlap of about 128+/-20.

  14. Dominant modes of relationship between U.S. temperature and geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Prohaska, J. T.; Willett, H. C.

    1983-01-01

    Eigen-analysis is applied to a matrix of cross-correlation coefficients between the geomagnetic aa-index for 0 to 23-yr lag and the monthly mean temperature at 32 United States stations. About 75 percent of the relationship between the two fields is contained in three dominant modes. A secular trend (about 90 yr) and two 11-yr cycles dominate the mode time series. The month-to-month changes in the temperature anomaly patterns indicate a slow eddy-like motion to the east of the Continental Divide for all three dominant modes.

  15. Geomagnetic Disturbances Caused by Internal Atmospheric Dynamics

    NASA Technical Reports Server (NTRS)

    Sonneman, G.

    1984-01-01

    It is commonly believed that geomagnetic disturbances are caused by external influences connected with the solar wind. The 27-day recurrence of perturbations seems to be a strong hint for this interaction. But frequently geomagnetic disturbances occur without any relation to sunspot numbers or radiowave fluxes. This was one of the reasons for introducing hypothetical M-regions on the Sun and their relation to solar wind activities. Only one half of the variance of the geomagnetic AL-index could be related to the solar wind. Therefore it is concluded that internal processes of the magnetosphere were responsible for additional geomagnetic activity. Arguments, which might lead to the suggestion of geomagnetic disturbances as being caused by internal atmospheric dynamics are discussed and a rather preliminary scenario of those processes is proposed.

  16. An Examination of Selected Geomagnetic Indices in Relation to the Sunspot Cycle

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2006-01-01

    Previous studies have shown geomagnetic indices to be useful for providing early estimates for the size of the following sunspot cycle several years in advance. Examined this study are various precursor methods for predicting the minimum and maximum amplitude of the following sunspot cycle, these precursors based on the aa and Ap geomagnetic indices and the number of disturbed days (NDD), days when the daily Ap index equaled or exceeded 25. Also examined is the yearly peak of the daily Ap index (Apmax), the number of days when Ap greater than or equal to 100, cyclic averages of sunspot number R, aa, Ap, NDD, and the number of sudden storm commencements (NSSC), as well the cyclic sums of NDD and NSSC. The analysis yields 90-percent prediction intervals for both the minimum and maximum amplitudes for cycle 24, the next sunspot cycle. In terms of yearly averages, the best regressions give Rmin = 9.8+/-2.9 and Rmax = 153.8+/-24.7, equivalent to Rm = 8.8+/-2.8 and RM = 159+/-5.5, based on the 12-mo moving average (or smoothed monthly mean sunspot number). Hence, cycle 24 is expected to be above average in size, similar to cycles 21 and 22, producing more than 300 sudden storm commencements and more than 560 disturbed days, of which about 25 will be Ap greater than or equal to 100. On the basis of annual averages, the sunspot minimum year for cycle 24 will be either 2006 or 2007.

  17. A Study on local geomagnetic activity trend and singularity with geomagnetic data at Cheongyang Magnetic Observatory, Korea

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Jeon, Y.; Ryoo, S.

    2011-12-01

    The KMA(Korea Meteorological Administration) has installed and operated the geomagnetic observatory at Cheongyang-gun, Chungcheongnam-do, Korea which started in April, 2009. As Cheongyang geomagnetic observatory, it has been automatically observing total-, X-, Y- and Z-component data at 1-sec interval and storing in real-time. The National Institute of Meteorological Research, which belongs to KMA, proceeded with their work on the production of K-index that is used for geomagnetic activity observation. In addition, we detect the starting and ending of geomagnetic storm as typical thing of global geomagnetic field change and utilize it for showing current status of geomagnetic storm occurrence. It has been reported that geomagnetic storm occurred seven times during from April, 2010 to July, 2011. It was 5 of the maximum K-index value during geomagnetic storm occurrence period and thought mostly to have been caused by coronal hole and CME(Coronal Mass Ejection). Yet the geomagnetic storm has not been had much of an impact locally. At Cheongyang Observatory, a significantly disturbed geomagnetic data was seen as related to the Tohoku, Japan Earthquake, Mw 9.0, on March 11, 2011. Compared to seismic wave data at Seosan seismic observatory 60km away from Cheongyang geomagnetic observatory, we identified the signal involved to the Tohoku, Japan Earthquake. The power spectral density of the disturbed signal has the dominant frequency band of about 0.05 to 0.1 Hz. We should proceed additional study about this in detail.

  18. On the Relationship Between Global Land-Ocean Temperature and Various Descriptors of Solar-Geomagnetic Activity and Climate

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2014-01-01

    Examined are sunspot cycle- (SC-) length averages of the annual January-December values of the Global Land-Ocean Temperature Index () in relation to SC-length averages of annual values of various descriptors of solar-geomagnetic activity and climate, incorporating lags of 0-5 yr. For the overall interval SC12-SC23, the is inferred to correlate best against the parameter <aa(I:SSN)> incorporating lag = 5 yr, where the parameter <aa(I:SSN)> refers to the resultant aa value having removed that portion of the annual aa average value due to the yearly variation of sunspot number (SSN). The inferred correlation between the and <aa(I:SSN)> is statistically important at confidence level cl > 99.9%, having a coefficient of linear correlation r = 0.865 and standard error of estimate se = 0.149 degC. Excluding the most recent cycles SC22 and SC23, the inferred correlation is stronger, having r = 0.969 and se = 0.048 degC. With respect to the overall trend in the , which has been upwards towards warmer temperatures since SC12 (1878-1888), solar-geomagnetic activity parameters are now trending downwards (since SC19). For SC20-SC23, in contrast, comparison of the against SC-length averages of the annual value of the Mauna Loa carbon dioxide () index is found to be highly statistically important (cl >> 99.9%), having r = 0.9994 and se = 0.012 degC for lag = 2 yr. On the basis of the inferred preferential linear correlation between the and , the current ongoing SC24 is inferred to have warmer than was seen in SC23 (i.e., >0.526 degC), probably in excess of 0.68 degC (relative to the 1951-1980 base period).

  19. Space climate characterization via geomagnetic indices. An attempt of integrating solar, heliospheric, and geomagnetic indices at various time-scales

    NASA Astrophysics Data System (ADS)

    Demetrescu, Crisan; Dobrica, Venera

    2013-04-01

    The so-called space climate concerns the long-term change in the Sun and its effects in the heliosphere and upon the Earth, including the atmosphere and climate. Annual means of measured and reconstructed solar, heliospheric, and magnetospheric parameters are used to infer solar activity signatures at the Hale and Gleissberg cycles timescales. Available open solar flux, modulation strength, cosmic ray flux, total solar irradiance data, reconstructed back to 1700, solar wind parameters (speed, density, dynamic pressure) and the magnitude of the heliospheric magnetic field at 1 AU, reconstructed back to 1870, as well as the time series of geomagnetic activity indices (aa, IDV, IHV), going back to 1870, have been considered. Also, shorter time series of some other geomagnetic indices, designed as proxies for specific current systems, such as the ring current and the auroral electrojet, that develop in the magnetosphere and ionosphere as a consequence of the interraction with the solar wind and heliosperic magnetic field (the Dst and, respectively, AE indices), as well as the merging electric field and convection in the polar ionosphere (the PC index) have been taken into account. Simple filtering procedures (successive 11-, 22-, and 88-year running averages and differences between them) and scaling by the standard deviation from the average value for the common interval covered by the data show that the long-discussed variation in the 20th century (a pronounced increase since ~1900, followed by a depression in the '60s and a new, slower, increase), seen in the 11-year averages of parameters such as geomagnetic activity indices and reconstructed heliospheric magnetic field strength, solar wind speed, open solar flux etc., is a result of the superposition in data of solar activity signatures at Hale and Gleissberg cycles timescales. The Hale and Gleissberg signals were characterized and similarities and differences in the temporal behavior of the analyzed parameters at these timescales are discussed. The similarities in the studied parameters point to the common pacing source, the solar dynamo.

  20. The geomagnetic cutoff rigidities at high latitudes for different solar wind and geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Chu, W.; Qin, G.

    2016-01-01

    Studying the access of the cosmic rays (CRs) into the magnetosphere is important to understand the coupling between the magnetosphere and the solar wind. In this paper we numerically studied CRs' magnetospheric access with vertical geomagnetic cutoff rigidities using the method proposed by Smart and Shea (1999). By the study of CRs' vertical geomagnetic cutoff rigidities at high latitudes we obtain the CRs' window (CRW) whose boundary is determined when the vertical geomagnetic cutoff rigidities drop to a value lower than a threshold value. Furthermore, we studied the area of CRWs and found out they are sensitive to different parameters, such as the z component of interplanetary magnetic field (IMF), the solar wind dynamic pressure, AE index, and Dst index. It was found that both the AE index and Dst index have a strong correlation with the area of CRWs during strong geomagnetic storms. However, during the medium storms, only AE index has a strong correlation with the area of CRWs, while Dst index has a much weaker correlation with the area of CRWs. This result on the CRW can be used for forecasting the variation of the cosmic rays during the geomagnetic storms.

  1. Analysis of geomagnetic hourly ranges

    NASA Astrophysics Data System (ADS)

    Danskin, D. W.; Lotz, S. I.

    2015-08-01

    In an attempt to develop better forecasts of geomagnetic activity, hourly ranges of geomagnetic data are analyzed with a focus on how the data are distributed. A lognormal distribution is found to be able to characterize the magnetic data for all observatories up to moderate disturbances with each distribution controlled by the mean of the logarithm of the hourly range. In the subauroral zone, the distribution deviates from the lognormal, which is interpreted as motion of the auroral electrojet toward the equator. For most observatories, a substantial deviation from the lognormal distribution was noted at the higher values and is best modeled with a power law extrapolation, which gives estimates of the extreme values that may occur at observatories which contribute to the disturbance storm time (Dst) index and in Canada.

  2. Geomagnetic substorm activity associated with magnetic clouds

    NASA Astrophysics Data System (ADS)

    Barkhatov, N. A.; Vinogradov, A. B.; Levitin, A. E.; Revunova, E. A.

    2015-09-01

    The work to establishment of features generation of magnetic substorms interplanetary magnetic clouds, with participation in this process its sheathes is devoted. Research based on comparison parameter dynamics of magnetic clouds fine structure and clouds sheath with dynamics of auroral AL-index and Dst-index of global geomagnetic activity. Clouds sheath is original source of high-latitude activity and gives start to global magnetic storms. Storm development provided by body magnetic cloud parameters was found. However, separate sheath clouds rarely causes global geomagnetic activity, causing usually weak or moderate geomagnetic storms. The most often source of global disturbances becomes a combination of sheath and body, causing classical strong or multi-step storm.

  3. Predicting Solar Cycle 24 Using a Geomagnetic Precursor Pair

    NASA Technical Reports Server (NTRS)

    Pesnell, W. Dean

    2014-01-01

    We describe using Ap and F(10.7) as a geomagnetic-precursor pair to predict the amplitude of Solar Cycle 24. The precursor is created by using F(10.7) to remove the direct solar-activity component of Ap. Four peaks are seen in the precursor function during the decline of Solar Cycle 23. A recurrence index that is generated by a local correlation of Ap is then used to determine which peak is the correct precursor. The earliest peak is the most prominent but coincides with high levels of non-recurrent solar activity associated with the intense solar activity of October and November 2003. The second and third peaks coincide with some recurrent activity on the Sun and show that a weak cycle precursor closely following a period of strong solar activity may be difficult to resolve. A fourth peak, which appears in early 2008 and has recurrent activity similar to precursors of earlier solar cycles, appears to be the "true" precursor peak for Solar Cycle 24 and predicts the smallest amplitude for Solar Cycle 24. To determine the timing of peak activity it is noted that the average time between the precursor peak and the following maximum is approximately equal to 6.4 years. Hence, Solar Cycle 24 would peak during 2014. Several effects contribute to the smaller prediction when compared with other geomagnetic-precursor predictions. During Solar Cycle 23 the correlation between sunspot number and F(10.7) shows that F(10.7) is higher than the equivalent sunspot number over most of the cycle, implying that the sunspot number underestimates the solar-activity component described by F(10.7). During 2003 the correlation between aa and Ap shows that aa is 10 % higher than the value predicted from Ap, leading to an overestimate of the aa precursor for that year. However, the most important difference is the lack of recurrent activity in the first three peaks and the presence of significant recurrent activity in the fourth. While the prediction is for an amplitude of Solar Cycle 24 of 65 +/- 20 in smoothed sunspot number, a below-average amplitude for Solar Cycle 24, with maximum at 2014.5+/-0.5, we conclude that Solar Cycle 24 will be no stronger than average and could be much weaker than average.

  4. On the causes of geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1975-01-01

    The causes of geomagnetic activity are studied both theoretically in terms of the reconnection model and empirically using the am-index and interplanetary solar wind parameters. It is found that two separate mechanisms supply energy to the magnetosphere. One mechanism depends critically on the magnitude and direction of the interplanetary magnetic field. Both depend strongly on solar wind speed.

  5. Astroblemes and geomagnetic inversions

    NASA Astrophysics Data System (ADS)

    Kalinin, Yu. D.

    1993-08-01

    A comparison is made of the age distributions of astroblemes and magnetic inversions, and it is found that these distributions are well correlated. This provides another argument in support of a hypothesis whereby the geomagnetic inversions and geomagnetic polarity superchrons result from the impact of giant asteroids against the earth.

  6. Range indices of geomagnetic activity

    USGS Publications Warehouse

    Stuart, W.F.; Green, A.W., Jr.

    1988-01-01

    The simplest index of geomagnetic activity is the range in nT from maximum to minimum value of the field in a given time interval. The hourly range R was recommended by IAGA for use at observatories at latitudes greater than 65??, but was superceded by AE. The most used geomagnetic index K is based on the range of activity in a 3 h interval corrected for the regular daily variation. In order to take advantage of real time data processing, now available at many observatories, it is proposed to introduce a 1 h range index and also a 3 h range index. Both will be computed hourly, i.e. each will have a series of 24 per day, the 3 h values overlapping. The new data will be available as the range (R) of activity in nT and also as a logarithmic index (I) of the range. The exponent relating index to range in nT is based closely on the scale used for computing K values. The new ranges and range indices are available, from June 1987, to users in real time and can be accessed by telephone connection or computer network. Their first year of production is regarded as a trial period during which their value to the scientific and commercial communities will be assessed, together with their potential as indicators of regional and global disturbances' and in which trials will be conducted into ways of eliminating excessive bias at quiet times due to the rate of change of the daily variation field. ?? 1988.

  7. Major geomagnetic storm due to solar activity (2006-2013).

    NASA Astrophysics Data System (ADS)

    Tiwari, Bhupendra Kumar

    Major geomagnetic storm due to solar activity (2006-2013). Bhupendra Kumar Tiwari Department of Physics, A.P.S.University, Rewa(M.P.) Email: - btiwtari70@yahoo.com mobile 09424981974 Abstract- The geospace environment is dominated by disturbances created by the sun, it is observed that coronal mass ejection (CME) and solar flare events are the causal link to solar activity that produces geomagnetic storm (GMS).CMEs are large scale magneto-plasma structures that erupt from the sun and propagate through the interplanetary medium with speeds ranging from only a few km/s to as large as 4000 km/s. When the interplanetary magnetic field associated with CMEs impinges upon the earth’s magnetosphere and reconnect occur geomagnetic storm. Based on the observation from SOHO/LASCO spacecraft for solar activity and WDC for geomagnetism Kyoto for geomagnetic storm events are characterized by the disturbance storm time (Dst) index during the period 2006-2013. We consider here only intense geomagnetic storm Dst <-100nT, are 12 during 2006-2013.Geomagnetic storm with maximum Dst< -155nT occurred on Dec15, 2006 associated with halo CME with Kp-index 8+ and also verify that halo CME is the main cause to produce large geomagnetic storms.

  8. Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr - Part 4: Near-Earth solar wind speed, IMF, and open solar flux

    NASA Astrophysics Data System (ADS)

    Lockwood, M.; Nevanlinna, H.; Barnard, L.; Owens, M. J.; Harrison, R. G.; Rouillard, A. P.; Scott, C. J.

    2014-04-01

    In the concluding paper of this tetralogy, we here use the different geomagnetic activity indices to reconstruct the near-Earth interplanetary magnetic field (IMF) and solar wind flow speed, as well as the open solar flux (OSF) from 1845 to the present day. The differences in how the various indices vary with near-Earth interplanetary parameters, which are here exploited to separate the effects of the IMF and solar wind speed, are shown to be statistically significant at the 93% level or above. Reconstructions are made using four combinations of different indices, compiled using different data and different algorithms, and the results are almost identical for all parameters. The correction to the aa index required is discussed by comparison with the Ap index from a more extensive network of mid-latitude stations. Data from the Helsinki magnetometer station is used to extend the aa index back to 1845 and the results confirmed by comparison with the nearby St Petersburg observatory. The optimum variations, using all available long-term geomagnetic indices, of the near-Earth IMF and solar wind speed, and of the open solar flux, are presented; all with 2? uncertainties computed using the Monte Carlo technique outlined in the earlier papers. The open solar flux variation derived is shown to be very similar indeed to that obtained using the method of Lockwood et al. (1999).

  9. The new approach for dynamical regimes detection in geomagnetic time series

    NASA Astrophysics Data System (ADS)

    Knyazeva, I. S.; Makarenko, N. G.; Kuperin, Y. A.; Dmitrieva, L. A.

    2016-02-01

    We suggest the new approach that could be used in the task of geomagnetic indexes forecasting. This approach based on the topological structure of the time series. The hourly data of different geomagnetic indexes were analyzed. We split the whole series to the calm parts, and geomagnetic storm preceding parts and find that the main measure of the topological structure of the series which called topological persistence differ significantly between these two groups.

  10. Wavelet analysis of the singular spectral reconstructed time series to study the imprints of Solar-ENSO-Geomagnetic activity on Indian climate

    NASA Astrophysics Data System (ADS)

    Sri Lakshmi, S.; Tiwari, R. K.

    2015-09-01

    In order to study the imprints of solar-ENSO-geomagnetic activity on the Indian Subcontinent, we have applied the Singular Spectral Analysis (SSA) and wavelet analysis to the tree ring temperature variability record from the western Himalayas. The data used in the present study are the Solar Sunspot Number (SSN), Geomagnetic Indices (aa Index), Southern Oscillation Index (SOI) and tree ring temperature record from western Himalayas (WH), for the period of 1876-2000. The SSA and wavelet spectra reveal the presence of 5 years short term ENSO variations to 11 year solar cycle indicating the influence of both the solar-geomagnetic and ENSO imprints in the tree ring data. The presence of 33-year cycle periodicity suggests the Sun-temperature variability probably involving the induced changes in the basic state of the atmosphere. Our wavelet analysis for the SSA reconstructed time series agrees with our previous results and also enhance the amplitude of the signals by removing the noise and showing a strong influence of solar-geomagnetic and ENSO patterns throughout the record. The solar flares are considered to be responsible for cause in the circulation patterns in the atmosphere. The net effect of solar-geomagnetic processes on temperature record thus appears to be the result of counteracting influences on shorter (about 5-6 years) and longer (about 11-12 years) time scales. The present analysis thus suggests that the influence of solar processes on Indian temperature variability operates in part indirectly through ENSO, but on more than one time scale. The analyses hence provides credible evidence for teleconnections of tropical pacific climatic variability with Indian climate ranging from interannual-decadal time scales and also demonstrate the possible role of exogenic triggering in reorganizing the global earth-ocean-atmospheric systems.

  11. Principles of major geomagnetic storms forecasting

    NASA Astrophysics Data System (ADS)

    Zagnetko, Alexander; Applbaum, David; Dorman, Lev; Pustil'Nik, Lev; Sternlieb, Abraham; Zukerman, Igor

    According to NOAA Space Weather Scales, geomagnetic storms of scales G5 (3-hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) are dangerous for people technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others). To prevent these serious damages will be very important to forecast dangerous geomagnetic storms. In many papers it was shown that in principle for this forecasting can be used data on CR intensity and CR anisotropy changing before SC of major geomagnetic storms accompanied by sufficient Forbush-decreases (e.g., Dorman et al., 1995, 1999). In this paper we consider all types of observed precursor effects in CR what can be used for forecasting of great geomagnetic storms and possible mechanisms of these precursor effects origin. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, 49A, 136-144 (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their pre-diction", Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, 6, 476-479 (1999).

  12. Geomagnetic excitation of nutation

    NASA Astrophysics Data System (ADS)

    Ron, C.; Vondrák, J.

    2015-08-01

    We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.

  13. Geomagnetic disturbance and the orientation of nocturnally migrating birds.

    PubMed

    Moore, F R

    1977-05-01

    Free-flying passerine migrants respond to natural fluctuations in the earth's magnetic field. The variability in flight directions of nocturnal migrants is significantly correlated with increasing geomagnetic disturbance as measured by both the K index and various components of the earth's magnetic field. The results indicate that such disturbances influence the orientation of free-flying migrants, but the evidence is not sufficient to show that geomagnetism is a cue in their orientation system. PMID:854743

  14. Statistical Study of Strong and Extreme Geomagnetic Disturbances and Solar Cycle Characteristics

    NASA Astrophysics Data System (ADS)

    Kilpua, E. K. J.; Olspert, N.; Grigorievskiy, A.; Käpylä, M. J.; Tanskanen, E. I.; Miyahara, H.; Kataoka, R.; Pelt, J.; Liu, Y. D.

    2015-06-01

    We study the relation between strong and extreme geomagnetic storms and solar cycle characteristics. The analysis uses an extensive geomagnetic index AA data set spanning over 150 yr complemented by the Kakioka magnetometer recordings. We apply Pearson correlation statistics and estimate the significance of the correlation with a bootstrapping technique. We show that the correlation between the storm occurrence and the strength of the solar cycle decreases from a clear positive correlation with increasing storm magnitude toward a negligible relationship. Hence, the quieter Sun can also launch superstorms that may lead to significant societal and economic impact. Our results show that while weaker storms occur most frequently in the declining phase, the stronger storms have the tendency to occur near solar maximum. Our analysis suggests that the most extreme solar eruptions do not have a direct connection between the solar large-scale dynamo-generated magnetic field, but are rather associated with smaller-scale dynamo and resulting turbulent magnetic fields. The phase distributions of sunspots and storms becoming increasingly in phase with increasing storm strength, on the other hand, may indicate that the extreme storms are related to the toroidal component of the solar large-scale field.

  15. The equatorial electrojet during geomagnetic storms and substorms

    NASA Astrophysics Data System (ADS)

    Yamazaki, Yosuke; Kosch, Michael J.

    2015-03-01

    The climatology of the equatorial electrojet during periods of enhanced geomagnetic activity is examined using long-term records of ground-based magnetometers in the Indian and Peruvian regions. Equatorial electrojet perturbations due to geomagnetic storms and substorms are evaluated using the disturbance storm time (Dst) index and auroral electrojet (AE) index, respectively. The response of the equatorial electrojet to rapid changes in the AE index indicates effects of both prompt penetration electric field and disturbance dynamo electric field, consistent with previous studies based on F region equatorial vertical plasma drift measurements at Jicamarca. The average response of the equatorial electrojet to geomagnetic storms (Dst<-50 nT) reveals persistent disturbances during the recovery phase, which can last for approximately 24 h after the Dst index reaches its minimum value. This "after-storm" effect is found to depend on the magnitude of the storm, solar EUV activity, season, and longitude.

  16. Geomagnetic Workshop, Canberra

    NASA Astrophysics Data System (ADS)

    Barton, C. E.; Lilley, F. E. M.; Milligan, P. R.

    On May 14-15, 1985, 63 discerning geomagnetists flocked to Canberra to attend the Geomagnetic Workshop coorganized by the Australian Bureau of Mineral Resources (BMR) and the Research School of Earth Sciences, Australian National University (ANU). With an aurorally glowing cast that included an International Association of Geomagnetism and Aeronomy (IAGA) president, former president, and division chairman, the Oriental Magneto-Banquet (which was the center of the meeting), was assured of success. As a cunning ploy to mask the true nature of this gastronomic extravagance from the probings of income tax departments, a presentation of scientific papers on Australian geomagnetism in its global setting was arranged.The Australian region, including New Zealand, Papua New Guinea, Indonesia, and a large sector of the Antarctic, covers one eighth of the Earth's surface and historically has played an important role in the study of geomagnetism. The region contains both the south magnetic and geomagnetic poles, and two Australian Antarctic stations (Casey and Davis) are situated in the region of the south polar cusp (see Figure 1).

  17. Geomagnetic Indices Variations And Human Physiology

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.

    2007-12-01

    A group of 86 volunteers was examined on each working day in autumn 2001 and in spring 2002. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were registered. Pulse pressure (PP) was calculated. Data about subjective psycho-physiological complaints (SPPC) were also gathered. Altogether 2799 recordings were obtained. ANOVA was employed to check the significance of influence of daily amplitude of H-component of local geomagnetic field, daily planetary Ap-index and hourly planetary Dst-index on the physiological parameters examined. Post hoc analysis was performed to elicit the significance of differences in the factors levels. Average values of SBP, DBP, PP and SPPC of the group were found to increase statistically significantly and biologically considerably with the increase of geomagnetic indices.

  18. Interplanetary Scintillation and Geomagnetic Activity

    NASA Astrophysics Data System (ADS)

    Perez-Enriquez, Roman; Carrillo-Vargas, Armando; Kotsarenko, Anatoly; Lopez Cruz-Abeyro, Jose Antonio

    In this paper the daily values of the global index of interplanetary scintillation, G, obtained from the g-maps of Cambridge Observatory, UK, were analyzed for the period 1991-1994 in relation with the geomagnetic index DST, to determine the possible impact of both large scale events and small scale magnetic irregularities on the magnetosphere of our planet. The analysis consisted of the comparison of the two time series G and DST, as well as a superposed epoch analysis of G with respect to the ocurrence of 16 events where the DST index dropped to less than -70 nT. While the cross-correlation shows that there is a marked anti-correlation with a lag of 2 days, the superposed epoch analysis showed a peak at day zero of 2.93 sigmas that start 2 days before. No peak was found when the analysis was performed on 16 randomly chosen dates in the period. The results indicate that the state of the inner heliosphere as given by the G index may be important in the study of the solar wind related magnetospheric activity.

  19. Influence of geomagnetic disturbance on atmospheric circulation

    NASA Technical Reports Server (NTRS)

    Kodera, K.

    1985-01-01

    The influence of geomagnetic disturbance or passage of the solar sector boundary on the atmospheric circulation was reported. Unfortunately little is known about the general morphology of Sun weather relationships. In order to know the general characteristics, pressure height variations on an isobaric surface over the Northern Hemisphere were analyzed. Although it may be suitable to use some index, or some integrated value for statistical purposes, weather prediction data were used to verify whether the obtained tropospheric response is caused externally or not.

  20. Prediction of geomagnetic activity

    SciTech Connect

    Goertz, C.K.; Linhua Shan; Smith, R.A. )

    1993-05-01

    The authors present an analytic model to explain the interaction of the solar wind with the earth's magnetosphere, and hence the way the solar wind controls geomagnetic activity. Studies have shown a strong correlation of auroral electrojet activity with geomagnetic activity. This also correlates with a southward turn in the orientation of the interplanetary magnetic field. The major problem in the correlation of electrojet activity is the large time delay associated with the solar wind observations. This model deals with this observation. The model has the possibility of introducing instabilities in the tail to drive geomagnetic activity, but the authors find this is not necessary, implying that the solar wind can drive this directly. The model does show the periodic buildup and decrease in magnetic energy observed during substorm activity.

  1. Conjugate Event Study of Geomagnetic ULF Pulsations with Wavelet-based Indices

    NASA Astrophysics Data System (ADS)

    Xu, Z.; Clauer, C. R.; Kim, H.; Weimer, D. R.; Cai, X.

    2013-12-01

    The interactions between the solar wind and geomagnetic field produce a variety of space weather phenomena, which can impact the advanced technology systems of modern society including, for example, power systems, communication systems, and navigation systems. One type of phenomena is the geomagnetic ULF pulsation observed by ground-based or in-situ satellite measurements. Here, we describe a wavelet-based index and apply it to study the geomagnetic ULF pulsations observed in Antarctica and Greenland magnetometer arrays. The wavelet indices computed from these data show spectrum, correlation, and magnitudes information regarding the geomagnetic pulsations. The results show that the geomagnetic field at conjugate locations responds differently according to the frequency of pulsations. The index is effective for identification of the pulsation events and measures important characteristics of the pulsations. It could be a useful tool for the purpose of monitoring geomagnetic pulsations.

  2. Estimation of interplanetary electric field conditions for historical geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Veenadhari, B.; Tulasi Ram, S.; Selvakumaran, R.; Mukherjee, Shyamoli; Singh, Rajesh; Kadam, B. D.

    2015-09-01

    Ground magnetic measurements provide a unique database in understanding space weather. The continuous geomagnetic records from Colaba-Alibag observatories in India contain historically longest and continuous observations from 1847 to present date. Some of the super intense geomagnetic storms that occurred prior to 1900 have been revisited and investigated in order to understand the probable interplanetary conditions associated with intense storms. Following Burton et al. (1975), an empirical relationship is derived for estimation of interplanetary electric field (IEFy) from the variations of Dst index and ?H at Colaba-Alibag observatories. The estimated IEFy values using Dst and ?HABG variations agree well with the observed IEFy, calculated using Advanced Composition Explorer (ACE) satellite observations for intense geomagnetic storms in solar cycle 23. This study will provide the uniqueness of each event and provide important insights into possible interplanetary conditions for intense geomagnetic storms and probable frequency of their occurrence.

  3. The combined effects of electrojet strength and the geomagnetic activity (Kp-index) on the post sunset height rise of the F-layer and its role in the generation of ESF during high and low solar activity periods

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Rama Rao, P. V. S.; Prasad, D. S. V. V. D.; Niranjan, K.; Raja Babu, A.; Sridharan, R.; Devasia, C. V.; Ravindran, Sudha

    2007-10-01

    Several investigations have been carried out to identify the factors that are responsible for the day-to-day variability in the occurrence of equatorial spread-F (ESF). But the precise forecasting of ESF on a day-to-day basis is still far from reality. The nonlinear development and the sustenance of ESF/plasma bubbles is decided by the background ionospheric conditions, such as the base height of the F-layer (h'F), the electron density gradient (dN/dz), maximum ionization density (Nmax), geomagnetic activity and the neutral dynamics. There is increasing evidence in the literature during the recent past that shows a well developed Equatorial Ionization Anomaly (EIA) during the afternoon hours contributes significantly to the initiation of ESF during the post-sunset hours. Also, there exists a good correlation between the Equatorial Ionization Anomaly (EIA) and the Integrated Equatorial ElectroJet (IEEJ) strength, as the driving force for both is the same, namely, the zonal electric field at the equator. In this paper, we present a linear relationship that exists between the daytime integrated equatorial electrojet (IEEJ) strength and the maximum elevated height of the F-layer during post-sunset hours (denoted as peak h'F). An inverse relationship that exists between the 6-h average Kp-index prior to the local sunset and the peak h'F of the F-layer is also presented. A systematic study on the combined effects of the IEEJ and the average Kp-index on the post-sunset, peak height of the F-layer (peak h'F), which controls the development of ESF/plasma bubbles, is carried out using the ionosonde data from an equatorial station, Trivandrum (8.47° N, 76.91° E, dip.lat. 0.5° N), an off-equatorial station, SHAR (13.6° N, 79.8° E, dip.lat. 10.8° N) and VHF scintillations (244 MHz) observed over a nearby low-latitude station, Waltair (17.7° N, 83.3° E, dip.lat. 20° N). From this study, it has been found that the threshold base height of the F-layer at the equator for the development of plasma bubbles is reduced from 405 km to 317 km as the solar activity decreases from March 2001 (mean Rz=113.5) to March 2005 (mean Rz=24.5). This decrease in threshold height with the decreasing solar activity is explained on the basis of changes in the local linear growth rate of the collisional Rayleigh-Taylor instability, due to the variability of various terms such as inverse density gradient scale length (L-1), ion-neutral collision frequency (νin) and recombination rate (R) with the changes in the solar activity.

  4. Foundations of Geomagnetism

    NASA Astrophysics Data System (ADS)

    Jackson, Andy

    The study of the magnetic field of the Earth, or geomagnetism, is one of the oldest lines of scientific enquiry. Indeed, it has often been said that William Gilbert's De Magnete, published in 1600 and predating Isaac Newton's Principia by 87 years, can claim to be the first true scientific textbook; his study was essentially the first of academic rather than practical interest.What then, we may ask, has been accomplished in the nearly 400 intervening years up to the publication of Foundations of Geomagnetism? In short, a wealth of observational evidence, considerable physical understanding, and a great deal of mathematical apparatus have accrued, placing the subject on a much surer footing.The latter two categories are described in considerable detail, and with attendant rigor, in this book. The sphericity of the Earth means that a frequent theme in the book is the solution of the partial differential equations of electrodynamics in a spherical geometry.

  5. Trends of solar-geomagnetic activity, cosmic rays, atmosphere, and climate changes

    NASA Astrophysics Data System (ADS)

    Voronin, N.; Avakyan, S.

    2009-04-01

    The results are presented of the analysis of trends in the solar-geomagnetic activity and intensity of galactic cosmic rays (GCR) for the several eleven-year solar cycles. The indication has been revealed of the change of signs in the long-term changes in geomagnetic activity (aa-index) and the GCR in recent years. These changes correspond to the changes of sings in long-term trends in some of atmospheric parameters (transparency, albedo, cloudness, the content of water vapour, methane, ozone, the erythemal radiation flux). These global changes in atmosphere is most important problem of the up-to-date science. The global warming observed during the several past decades presents a real danger for the mankind. Till present the predominant point of view has been that the main cause of the increase of mean surface air temperature is the increase of concentrations of the anthropogenic gases first of all carbon dioxide CO2 and methane CH_4. Indeed, from the beginning of nineteen century the concentration of CO2 in the atmosphere has been growing and now it exceeds the initial level by the factor of 1.4 and the speed of this increase being growing too. This was the reason of international efforts to accept the Kyoto Protocol which limited the ejections of greenhouse gases. However there are premises which show that the influence of solar variability on the climate should be taken into account in the first place. The obtained results are analyzed from the point of view of well known effects of GCR influence on weather and climate with taken into account also a novel trigger mechanism in solar-terrestrial relations what allows revaluation of the role of solar flares and geomagnetic storms. The mechanism explains how agents of solar and geomagnetic activities affect atmospheric processes. This first agent under consideration is variation of fluxes of solar EUV and X-ray radiation. The second agent is fluxes of electrons and protons which precipitate from radiation belts as a result of geomagnetic disturbances. All these fluxes are completely absorbed in the ionosphere and hence do not reach lower atmosphere. Our novel radiooptical trigger mechanism of influence of solar and geomagnetic activity on the formation of weather and climate changes consists of three stages. The first stage is an increase in generation of the microwave radiation which penetrates from the ionosphere to the earth surface. The microwave radiation arises from the transitions between Rydberg states which are exited by the energetic ionospheric electrons. The second stage is a change in the proportion of water vapour to water clusters caused by increased microwave radiation. The third stage is a change of the atmosphere transparency in the absorption bands of water vapour and clusters. The atmosphere transparency determines the fluxes of solar irradiance coming down as well as flux of the thermal radiation coming out from the underlying surface. These fluxes form the basis of the thermal balance and affect the weather and climate characteristics of the lower troposphere. The novel mechanism explains how factors of solar and geomagnetic activities affect atmospheric processes and why the changes observed in long-term trends might result in slowing down of global warming in the nearest future. According to the recent analysis of meteorological data (NASA Goddard Institute for Space Studies, 2008) the rate of global warming in 2008 appears to be slowing in comparison with the last eight years.

  6. A new pair of indices to describe the relationship between ionospheric disturbances and geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Chen, Zhou; Wang, Jing-Song; Huang, Chun-Ming; Huang, Lin-Feng

    2014-12-01

    In this paper, a new ionospheric index pairthe single-station index (Js) and the planetary index (Jp), which describe ionospheric disturbancesis constructed using the spectral-whitening method. Observations covering more than 30 years and obtained from 21 ionosonde stations widely distributed across middle- and low-latitude areas are used in the study. Variations in the Js index at all stations generally follow the variation of the geomagnetic Dst index during periods of strong to moderate geomagnetic activity. Nevertheless, the inertial response of Js to weak geomagnetic activity results in a weak correlation between Js and Dst. The extrema of Js and Dst during the same geomagnetic activity period have a much higher correlation coefficient, since they avoid the delaying effect of the ionospheric response to geomagnetic activity. To smooth out local differences among ionospheric disturbances, the Jp index was defined as the means of all Js indices and so describes ionospheric disturbances at the planetary scale. The Jp index is significantly correlated to the Dst index, and the correlation coefficient between the extrema of Jp and Dst is up to -0.8. This correlation remains robust when the data set length varies, and data from approximately 10 stations are sufficient to derive a reasonable estimate of Jp. The quantitative relationship between Jp and Dst can be used to reproduce Jp by adopting Dst as the precursor, and this raises the possibility of predicting planetary ionospheric disturbances based on geomagnetic activity.

  7. Pacific geomagnetic secular variation.

    PubMed

    Doell, R R; Cox, A

    1971-01-22

    We have considered several different types of records of long-period geomagnetic secular variation: direct measurements made in geomagnetic observatories; paleomagnetic measurements on Hawaiian lava flows with accurately known ages in the interval 0 to 200 years; paleomagentic measurements on Hawaiian lava flows with loosely determined ages within the interval 200 to 10,000 years ago; and worldwide paleomagnetic measurements of the average geomagnetic angular dispersion recorded in lava flows that formed during the past 0.7 million years. All these magnetic records indicate that, during this time, the nondipole component of the earth's field was lower in the central Pacific than elsewhere, as it is today. This, in turn, indicates that there is some type of inhomogeneity in the lower mantle which is coupled to the earth's core in such a way as to suppress the generation of the nondipole field beneath the central Pacific. With the present incomplete state of knowledge about the processes that give rise to the earth's field, it is uncertain whether undulations in the core-mantle interface or lateral variations in the composition and physical state of the lower mantle are ultimately responsible for the pattern of secular variation seen at the earth's surface. PMID:17736217

  8. On extreme geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Cid, Consuelo; Palacios, Judith; Saiz, Elena; Guerrero, Antonio; Cerrato, Yolanda

    2014-10-01

    Extreme geomagnetic storms are considered as one of the major natural hazards for technology-dependent society. Geomagnetic field disturbances can disrupt the operation of critical infrastructures relying on space-based assets, and can also result in terrestrial effects, such as the Quebec electrical disruption in 1989. Forecasting potential hazards is a matter of high priority, but considering large flares as the only criterion for early-warning systems has demonstrated to release a large amount of false alarms and misses. Moreover, the quantification of the severity of the geomagnetic disturbance at the terrestrial surface using indices as Dst cannot be considered as the best approach to give account of the damage in utilities. High temporal resolution local indices come out as a possible solution to this issue, as disturbances recorded at the terrestrial surface differ largely both in latitude and longitude. The recovery phase of extreme storms presents also some peculiar features which make it different from other less intense storms. This paper goes through all these issues related to extreme storms by analysing a few events, highlighting the March 1989 storm, related to the Quebec blackout, and the October 2003 event, when several transformers burnt out in South Africa.

  9. Geomagnetic disturbances and coronal rays

    NASA Astrophysics Data System (ADS)

    Pintr, T.; Lorenc, M.; Rybansk, M.

    The cause of 92 geomagnetic disturbances in the period of 1997 - 2003 was analyzed. There were used data from LASCO C3 instrument from SOHO satellite, SOHO LASCO CME Catatalog, and the daily average indices Ap. In this contribution we proposed to search sources of the geomagnetic storms taking into account the old idea by Newkirk and Bohlin (1965). According to this idea a solar coronal streamer can cause geomagnetic disturbance when it crosses the Earth's space.

  10. Geomagnetic storms and telluric currents

    NASA Astrophysics Data System (ADS)

    Silbergleit, V. M.; Larocca, P. A.

    2009-04-01

    For June 12-13, 2005 thegeomagnetic indices AE and Dst, the parameters of the solar wind (speed and pressure) and the Bz component of the interplanetary geomagnetic field are analyzed as indicators of the development of the troubled period. During this period there were significant geomagnetic variations due to geomagnetic substorms and induced currents on the pipeline located in high latitudes, this fact could produce corrosion increases in its structure.

  11. The national geomagnetic initiative

    NASA Technical Reports Server (NTRS)

    1993-01-01

    The Earth's magnetic field, through its variability over a spectrum of spatial and temporal scales, contains fundamental information on the solid Earth and geospace environment (the latter comprising the atmosphere, ionosphere, and magnetosphere). Integrated studies of the geomagnetic field have the potential to address a wide range of important processes in the deep mantle and core, asthenosphere, lithosphere, oceans, and the solar-terrestrial environment. These studies have direct applications to important societal problems, including resource assessment and exploration, natural hazard mitigation, safe navigation, and the maintenance and survivability of communications and power systems on the ground and in space. Studies of the Earth's magnetic field are supported by a variety of federal and state agencies as well as by private industry. Both basic and applied research is presently supported by several federal agencies, including the National Science Foundation (NSF), U.S. Geological Survey (USGS), U.S. Department of Energy (DOE), National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and U.S. Department of Defense (DOD) (through the Navy, Air Force, and Defense Mapping Agency). Although each agency has a unique, well-defined mission in geomagnetic studies, many areas of interest overlap. For example, NASA, the Navy, and USGS collaborate closely in the development of main field reference models. NASA, NSF, and the Air Force collaborate in space physics. These interagency linkages need to be strengthened. Over the past decade, new opportunities for fundamental advances in geomagnetic research have emerged as a result of three factors: well-posed, first-order scientific questions; increased interrelation of research activities dealing with geomagnetic phenomena; and recent developments in technology. These new opportunities can be exploited through a national geomagnetic initiative to define objectives and encourage coordination of efforts among federal and state agencies, academic institutions, and industry to systematically characterize the spatial and temporal behavior of the Earth's magnetic field on local, regional, and global scales in order to understand the physical processes in the solid earth and geospace environment, and to apply this understanding to a variety of scientific problems and to technical and societal needs.

  12. The national geomagnetic initiative

    NASA Astrophysics Data System (ADS)

    The Earth's magnetic field, through its variability over a spectrum of spatial and temporal scales, contains fundamental information on the solid Earth and geospace environment (the latter comprising the atmosphere, ionosphere, and magnetosphere). Integrated studies of the geomagnetic field have the potential to address a wide range of important processes in the deep mantle and core, asthenosphere, lithosphere, oceans, and the solar-terrestrial environment. These studies have direct applications to important societal problems, including resource assessment and exploration, natural hazard mitigation, safe navigation, and the maintenance and survivability of communications and power systems on the ground and in space. Studies of the Earth's magnetic field are supported by a variety of federal and state agencies as well as by private industry. Both basic and applied research is presently supported by several federal agencies, including the National Science Foundation (NSF), U.S. Geological Survey (USGS), U.S. Department of Energy (DOE), National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and U.S. Department of Defense (DOD) (through the Navy, Air Force, and Defense Mapping Agency). Although each agency has a unique, well-defined mission in geomagnetic studies, many areas of interest overlap. For example, NASA, the Navy, and USGS collaborate closely in the development of main field reference models. NASA, NSF, and the Air Force collaborate in space physics. These interagency linkages need to be strengthened. Over the past decade, new opportunities for fundamental advances in geomagnetic research have emerged as a result of three factors: well-posed, first-order scientific questions; increased interrelation of research activities dealing with geomagnetic phenomena; and recent developments in technology. These new opportunities can be exploited through a national geomagnetic initiative to define objectives and encourage coordination of efforts among federal and state agencies, academic institutions, and industry to systematically characterize the spatial and temporal behavior of the Earth's magnetic field on local, regional, and global scales in order to understand the physical processes in the solid earth and geospace environment, and to apply this understanding to a variety of scientific problems and to technical and societal needs.

  13. Prediction of Geomagnetic Activity and Key Parameters in High-Latitude Ionosphere-Basic Elements

    NASA Technical Reports Server (NTRS)

    Lyatsky, W.; Khazanov, G. V.

    2007-01-01

    Prediction of geomagnetic activity and related events in the Earth's magnetosphere and ionosphere is an important task of the Space Weather program. Prediction reliability is dependent on the prediction method and elements included in the prediction scheme. Two main elements are a suitable geomagnetic activity index and coupling function -- the combination of solar wind parameters providing the best correlation between upstream solar wind data and geomagnetic activity. The appropriate choice of these two elements is imperative for any reliable prediction model. The purpose of this work was to elaborate on these two elements -- the appropriate geomagnetic activity index and the coupling function -- and investigate the opportunity to improve the reliability of the prediction of geomagnetic activity and other events in the Earth's magnetosphere. The new polar magnetic index of geomagnetic activity and the new version of the coupling function lead to a significant increase in the reliability of predicting the geomagnetic activity and some key parameters, such as cross-polar cap voltage and total Joule heating in high-latitude ionosphere, which play a very important role in the development of geomagnetic and other activity in the Earth s magnetosphere, and are widely used as key input parameters in modeling magnetospheric, ionospheric, and thermospheric processes.

  14. Geomagnetic polarity transitions

    NASA Astrophysics Data System (ADS)

    Merrill, Ronald T.; McFadden, Phillip L.

    1999-05-01

    The top of Earth's liquid outer core is nearly 2900 km beneath Earth's surface, so we will never be able to observe it directly. This hot, dense, molten iron-rich body is continuously in motion and is the source of Earth's magnetic field. One of the most dynamic manifestations at Earth's surface of this fluid body is, perhaps, a reversal of the geomagnetic field. Unfortunately, the most recent polarity transition occurred at about 780 ka, so we have never observed a transition directly. It seems that a polarity transition spans many human lifetimes, so no human will ever witness the phenomenon in its entirety. Thus we are left with the tantalizing prospect that paleomagnetic records of polarity transitions may betray some of the secrets of the deep Earth. Certainly, if there are systematics in the reversal process and they can be documented, then this will reveal substantial information about the nature of the lowermost mantle and of the outer core. Despite their slowness on a human timescale, polarity transitions occur almost instantaneously on a geological timescale. This rapidity, together with limitations in the paleomagnetic recording process, prohibits a comprehensive description of any reversal transition both now and into the foreseeable future, which limits the questions that may at this stage be sensibly asked. The natural model for the geomagnetic field is a set of spherical harmonic components, and we are not able to obtain a reliable model for even the first few harmonic terms during a transition. Nevertheless, it is possible, in principle, to make statements about the harmonic character of a geomagnetic polarity transition without having a rigorous spherical harmonic description of one. For example, harmonic descriptions of recent geomagnetic polarity transitions that are purely zonal can be ruled out (a zonal harmonic does not change along a line of latitude). Gleaning information about transitions has proven to be difficult, but it does seem reasonable to draw the following conclusions with varying degrees of confidence. There appears to be a substantial decrease in the mean intensity of the dipole field during a transition to 25% of its usual value. The duration of an average geomagnetic polarity transition is not well known but probably lies between 1000 and 8000 years. Values outside these bounds have been reported, but we give reasons as to why such outliers are likely to be artifacts. The reversal process is probably longer than the manifestation of the reversal at Earth's surface as recorded in paleomagnetic directional data. Convection hiatus during a geomagnetic polarity transition seems unlikely, and free-decay models for reversals appear to be generally incompatible with the data. This implies that certain theorems in dynamo theory, such as Cowling's theorem, should not be invoked to explain the origin of reversals. Unfortunately, the detailed description of directional changes during transitions remains controversial. Contrary to common belief, certain low-degree nondipole fields can produce significant longitudinal confinement of virtual geomagnetic poles (VGP) during a transition. The data are currently inadequate to refute or verify claims of longitudinal dipole confinement, VGP clustering, or other systematics during polarity transitions.

  15. Solar generated quasi-biennial geomagnetic variation

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Poros, D. J.

    1977-01-01

    The existence of highly correlated quasi-biennial variations in the geomagnetic field and in solar activity is demonstrated. The analysis uses a numerical filter technique applied to monthly averages of the geomagnetic horizontal component and of the Zurich relative sunspot number. Striking correlations are found between the quasi-biennial geomagnetic variations determined from several magnetic observatories located at widely different longitudes, indicating a worldwide nature of the obtained variation. The correlation coefficient between the filtered Dst index and the filtered relative sunspot number is found to be -0.79 at confidence level greater than 99% with a time-lag of 4 months, with solar activity preceding the Dst variation. The correlation between the unfiltered data of Dst and of the sunspot number is also high with a similar time-lag. Such a timelag has not been discussed in the literature, and a further study is required to establish the mode of sun-earth relationship that gives this time delay.

  16. Solar activity geomagnetic field and terrestrial weather

    NASA Technical Reports Server (NTRS)

    Knight, J. W.; Sturrock, P. A.

    1976-01-01

    Spectral analysis is used as an independent test of the reported association between interplanetary-magnetic-field structure and terrestrial weather. Spectra of the Ap geomagnetic activity index and the vorticity area index for the years from 1964 to 1970 are examined for common features that may be associated with solar-related phenomena, specifically for peaks in the power spectra of both time series with periods near 27.1 days. The spectra are compared in three ways, and the largest peak with the smallest probability estimate is found to occur at a period of 27.49 days. This result is considered to be statistically significant at the 98% level. It is concluded that the period derived from the Ap spectrum is related to solar rotation and that the analysis provides supporting evidence for a connection between the vorticity area index and solar activity.

  17. Resolving issues concerning Eskdalemuir geomagnetic hourly values

    NASA Astrophysics Data System (ADS)

    MacMillan, S.; Clarke, E.

    2011-02-01

    The hourly values of the geomagnetic field from 1911 to 1931 derived from measurements made at Eskdalemuir observatory in the UK, and available online from the World Data Centre for Geomagnetism at http://www.wdc.bgs.ac.uk/, have now been corrected. Previously they were 2-point averaged and transformed from the original north, east and vertical down values in the tables in the observatory yearbooks. This paper documents the course of events from discovering the post-processing done to the data to the final resolution of the problem. As it was through the development of a new index, the Inter-Hour Variability index, that this post-processing came to light, we provide a revised series of this index for Eskdalemuir and compare it with that from another European observatory. Conclusions of studies concerning long-term magnetic field variability and inferred solar variability, whilst not necessarily consistent with one another, are not obviously invalidated by the incorrect hourly values from Eskdalemuir. This series of events illustrates the challenges that lie ahead in removing any remaining errors and inconsistencies in the data holdings of different World Data Centres.

  18. Sources of Geomagnetic Activity during Nearly Three Solar Cycles (1972-2000)

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Cane, H. V.; Cliver, E. W.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We examine the contributions of the principal solar wind components (corotating highspeed streams, slow solar wind, and transient structures, i.e., interplanetary coronal mass ejections (CMEs), shocks, and postshock flows) to averages of the aa geomagnetic index and the interplanetary magnetic field (IMF) strength in 1972-2000 during nearly three solar cycles. A prime motivation is to understand the influence of solar cycle variations in solar wind structure on long-term (e.g., approximately annual) averages of these parameters. We show that high-speed streams account for approximately two-thirds of long-term aa averages at solar minimum, while at solar maximum, structures associated with transients make the largest contribution (approx. 50%), though contributions from streams and slow solar wind continue to be present. Similarly, high-speed streams are the principal contributor (approx. 55%) to solar minimum averages of the IMF, while transient-related structures are the leading contributor (approx. 40%) at solar maximum. These differences between solar maximum and minimum reflect the changing structure of the near-ecliptic solar wind during the solar cycle. For minimum periods, the Earth is embedded in high-speed streams approx. 55% of the time versus approx. 35% for slow solar wind and approx. 10% for CME-associated structures, while at solar maximum, typical percentages are as follows: high-speed streams approx. 35%, slow solar wind approx. 30%, and CME-associated approx. 35%. These compositions show little cycle-to-cycle variation, at least for the interval considered in this paper. Despite the change in the occurrences of different types of solar wind over the solar cycle (and less significant changes from cycle to cycle), overall, variations in the averages of the aa index and IMF closely follow those in corotating streams. Considering solar cycle averages, we show that high-speed streams account for approx. 44%, approx. 48%, and approx. 40% of the solar wind composition, aa, and the IMF strength, respectively, with corresponding figures of approx. 22%, approx. 32%, and approx. 25% for CME-related structures, and approx. 33%, approx. 19%, and approx. 33% for slow solar wind.

  19. Ionospheric redistribution during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; Mannucci, A. J.

    2013-12-01

    The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<-100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3-6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  20. Longitude dependent response of the GPS derived ionospheric ROTI to geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Tanna, H. J.; Pathak, K. N.

    2014-08-01

    The local time dependent effects of geomagnetic storm on the ionospheric TEC and Rate of change of TEC Index (ROTI) are studied here using the GPS data for four different low latitude stations: Ogaswara, Japan (24.29 N, 153.91 E; Geomagnetic: 17.21 N, 136.16 W); Surat, India (21.16 N, 72.78 E; Geomagnetic: 12.88 N, 146.91 E); Bogota, Colombia (4.64 N, -74.09 E; Geomagnetic: 14.42 N, 1.67 W); and Kokee park Waimea, Hawaii, US (22.12 N, -159.67 E; Geomagnetic: 22.13 N, 91.19 W). The solar wind velocity and geomagnetic indices: Dst, Kp and IMF Bz are utilized to validate the geomagnetic storms registered during the years 2011 and 2012. Using the GPS based TEC data and computed values of ROTI, the storm induced ionospheric irregularities generation and inhibition has been studied for all stations. The present study suggests that, the F-region irregularities of a scale length of few kilometers over the magnetic equator are locally affected by geomagnetic storms. This study also shows a good agreement (70-84 %) with the Aaron's criteria (Aarons, Radio Sci., 26:1131-1149, 1991; Biktash, Ann. Geophys., 19:731-739, 2004) as significant absence and enhancement of ROTI was found to be influenced by the local time of the negative peak of Dst index association.

  1. Bracing for the geomagnetic storms

    SciTech Connect

    Kappenman, J.G. ); Albertson, V.D. )

    1990-03-01

    The authors discuss the impact of geomagnetic storms on utility transmission networks. The effects of a recent storm on the Hydro-Quebec transmission system are described in detail. Research into geomagnetic disturbance prediction is discussed. In coming months, geomagnetic field activity will be high as it builds toward a peak, the 22nd since reliable records of the phenomenon began in the mid-1700s. The peaks come in roughly 11-year cycles, and the next is expected later this year or early in 1991. The solar activity has so far risen at one of the fastest rates ever recorded, and solar forecasters expect cycle 22 to have unusually high activity levels.

  2. High latitude TEC fluctuations and irregularity oval during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Shagimuratov, I. I.; Krankowski, A.; Ephishov, I.; Cherniak, Yu.; Wielgosz, P.; Zakharenkova, I.

    2012-06-01

    GPS measurements obtained by the global IGS network were used to study the occurrence of TEC fluctuations in the northern and southern high-latitude ionosphere during severe geomagnetic storms. In the northern hemisphere, GPS stations located higher than 55N Corrected Geomagnetic Latitude (CGL) at different longitudes were selected. In the southern hemisphere, Antarctic permanent GPS stations were used. Dual-frequency GPS measurements for individual satellite passes served as raw data. As a measure of fluctuation activity the rate of TEC (ROT) was used, and the fluctuation intensity was evaluated using the ROTI index. Using daily GPS measurements from all selected stations, images of the spatial and temporal behavior of TEC fluctuations were formed (in Corrected Geomagnetic CoordinatesCGC and geomagnetic local timeGLT). Similarly to the auroral oval, these images demonstrate an irregularity oval. The occurrence of the irregularity oval relates to the auroral oval, cusp and polar cap. During a storm, the intensity of TEC fluctuations essentially increased. The irregularity oval expands equatorward with an increase of magnetic activity. The study showed that the existing high-latitude GPS stations can provide a permanent monitoring tool for the irregularity oval in near real-time. In this paper, the features of the development of phase fluctuations at the geomagnetic conjugate points, and inter-hemispheric differences and similarities during winter and summer conditions, are discussed.

  3. [Can solar/geomagnetic activity restrict the occurrence of some shellfish poisoning outbreaks? The example of PSP caused by Gymnodinium catenatum at the Atlantic Portuguese coast].

    PubMed

    Vale, P

    2013-01-01

    Cyclic outbreaks of accumulation of paralytic shellfish poisoning (PSP) toxins in mussels attributed to Gymnodinium catenatum blooms displayed several of the highest inter-annual maxima coincidental with minima of the 11-year solar sunspot number (SSN) cycle. The monthly distribution of PSP was associated with low levels of the solar radio flux, a more quantitative approach than SSN for fluctuations in solar activity. A comparison between monthly distribution of PSP and other common biotoxins (okadaic acid (OA), dinophysistoxin-2 (DTX2) and amnesic shellfish poisoning (ASP) toxins) demonstrated that only PSP was significantly associated with low levels of radio flux (p < 0.01). PSP occurrence suggests a prior decline in solar activity could be required to act as a trigger, in a similar manner to a photoperiodic signal. The seasonal frequency increased towards autumn during the study period, which might be related to the progressive atmospheric cut-off of deleterious radiation associated with the seasonal change in solar declination, and might play an additional role in seasonal signal-triggering. PSP distribution was also associated with low levels of the geomagnetic index Aa. A comparison between monthly distribution of PSP and other common biotoxins, also demonstrated that only PSP was significantly associated with low levels of the Aa index (p < 0.01). In some years of SSN minima no significant PSP-outbreaks in mussels were detected. This was attributed to a steady rise in geomagnetic activity that could disrupt the triggering signal. Global distribution patterns show that hotspots for G. catenatum blooms are regions with deficient crustal magnetic anomalies. In addition to the variable magnetic field mostly of solar origin, static fields related to magnetized rocks in the crust and upper mantle might play a role in restricting worldwide geographic distribution. PMID:24455892

  4. Geomagnetic Variability and Predictability

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia

    2011-01-01

    The Earth's magnetic field varies on time scales from seconds to millions of years. These variations can be measured directly by ground observatories and satellites, and indirectly through laboratories. They are from different electromagnetic processes in magnetosphere and ionosphere (external), ocean and crust (surface), and deep in the Earth's fluid outer core (internal). Of the measured magnetic signals, 95% is from the core, and is called the core field, or internal field. Variation of the core field, often called the geomagnetic secular variation (SV), is the manifestation of the magnetohydrodynamic processes in the core. Therefore, SV provides rich information on the core dynamical state that is then critical for understanding the geophysical mechanisms of the SV, the core-mantle interactions, and contribution of mass transport inside the core on Earth's gravity variation. Traditionally, the core state is probed via two independent methodologies: core flow inversion from the observed SV, and pure numerical dynamo simulation. The former is driven by observations, but does not include necessary interactions among physical variables; the latter is dynamically consistent, but is not constrained by any observation. Therefore, both are very limited in providing appropriate estimates of the core state. To avoid these limitations, a new approach, geomagnetic data assimilation, appears recently. In this approach, simulation results (model forecasts) are constantly corrected with observations, the corrected solutions (analysis), are then used as the initial conditions to make more accurate forecasts of future. Recent studies have demonstrated successfully that assimilation solutions are different from those of free running models. These new solutions are better estimates of the core state, and have been used to provide accurate prediction of SV for the period from 2010 to 2015. This prediction is part of the IGRF field model for international community applications.

  5. TWINS Geomagnetic Storm Catalog

    NASA Astrophysics Data System (ADS)

    Perez, J. D.; Buzulukova, N.; Fok, M. C. H.; Goldstein, J.; McComas, D. J.; Valek, P. W.; Wood, K. D.

    2014-12-01

    Results from TWINS 1 & 2 observations and CIMI simulations have been cataloged for geomagnetic storms with Dst or SYM/H below -100 nT in the years 2008-2013. TWINS (Two Wide-angle Imaging Neutral-atom Spectrometers) provides ENA (Energetic Neutral Atom) images on a nearly continuous basis over a broad energy range (1-100 keV/amu). CIMI (Comprehensive Inner-Magnetosphere Ionosphere) model combines the ability to simulate ringcurrent dynamics solving for particle distributions and corresponding ENA fluxes with the ability to calculate radiation belt particle fluxes and inner plasma sheet electron precipitation. For each storm, the TWINS Storm Catalog provides 1-hour-samples ENA images, corresponding deconvolved 2D equatorial ion number flux and pitch angle anisotropy, and the energy spectrum and pitch angle distribution at the position of the peak of the number flux. Also included for direct comparison are results from CIMI simulations for the same quantities. The catalog is available to all interested parties. It will be shown how users of the Catalog will have the opportunity to perform a number of studies related to the dynamics of the ring current during geomagnetic storms. For example, the storms cataloged to date show trends in changes of the energy spectrum from high energy tails deficient in ions as compared to a Maxwellian, to a high energy tail and finally approaching a Maxwellian. Likewise, pitch angle distributions are shown to evolve from having more perpendicular than parallel ions to a nearly isotropic distribution. It is also possible to investigate differences in ring current behavior for CIR and ICME driven storms.It is to be noted that in this context, opportunities for results from the measurements and simulations on a finer time scale, for spectra as a function of equatorial position, and similarly for pitch angle distributions are available by request.

  6. Relationship between isolated sleep paralysis and geomagnetic influences: a case study.

    PubMed

    Conesa, J

    1995-06-01

    This preliminary report, of a longitudinal study, looks at the relationship between geomagnetic activity and the incidence of isolated sleep paralysis over a 23.5-mo. period. The author, who has frequently and for the last 24 years experienced isolated sleep paralysis was the subject. In addition, incidence of lucid dreaming, vivid dreams, and total dream frequency were looked at with respect to geomagnetic activity. The data were in the form of dream-recall frequency recorded in a diary. These frequency data were correlated with geomagnetic activity k-index values obtained from two observatories. A significant correlation was obtained between periods of local geomagnetic activity and the incidence of isolated sleep paralysis. Specifically, periods of relatively quiet geomagnetic activity were significantly associated with an increased incidence of episodes. PMID:7478886

  7. Influence of the atmospheric blocking on the hydrometeorological variables from the Danube basin and possible response to the solar/geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Mares, Ileana; Dobrica, Venera; Demetrescu, Crisan; Mares, Constantin

    2015-04-01

    In order to test the large-scale atmospheric circulation influence on the hydrometeorological variables from the Danube basin, four blocking indices were considered for the regions: Greenland (GBI), Atlantic-European (AEBI), Atlantic (ABI) and Europe (EBI). In addition, an index for Greenland-Balkan Oscillation (GBOI) was introduced. For the Danube basin were analyzed: precipitation and temperatures at 15 stations and the Danube discharge at Orsova. Also, for each station were calculated four indices of Palmer type and a simple drought index (TPPI). Solar activity was represented by Wolf numbers and 10.7cm solar flux and the geomagnetic activity by the aa index. The time series of temperatures and precipitation were represented by the first principal component (PC1) of the development in empirical orthogonal functions (EOFs) and the four Palmer indices were analyzed by the PC1 of the development in multivariate EOFs (MEOFs). Cross correlations, power spectra and filters were performed. The analyses were achieved for two periods, 1901-2000 and 1948-2000, separately for each season. Concerning the simultaneous connections, for spring, the most significant results with a high confidence level (99%) were obtained for GBOI and EBI, which influence the discharge and the other hydrometeorological variables. Signals of solar or geomagnetic activity have been found only in EBI at level of 95%. For the summertime, the results are weaker. It is noted however, the significant influence of GBOI on the variables in the Danube basin, mainly on precipitation, and of EBI signal on temperatures. Solar signal is statistical significant (90% - 95%) in the GBI. Autumn, GBI, GBOI and EBI have a clear influence on all hydrometeorological fields. Signals statistically significant of aa index and 10.7 cm flux, were found in ABI and AEBI respectively. Winter, atmospheric circulation, quantified by GBI, EBI and GBOI, has an impact simultaneous on temperatures, precipitation and on the Orsova discharge. Also, significant signals of the aa index have been found in the GBI and GBOI. An analysis of the relationship between large-scale fields in the wintertime and the variables at regional / local scale during spring was achieved. This analysis revealed that the GB, GBO indices and especially EBI in wintertime are good predictors for the spring discharge. Also, the aa index in winter has a statistically significant signal (99%) in hydrometeorological variables with the highest correlation with precipitation. Also, the 10.7 cm solar flux in winter shows a statistically significant signal (at a level of 95%) in the Palmer indices as well as in temperatures and in precipitation during springtime. From the cross-correlation analysis with a lag of 5-years, between the hydroatmospheric variables and the geomagnetic or solar activity, were obtained very different results, depending on the season and variables analyzed. The most significant values have been found in summer for the 10.7 cm flux signal in variables from the Danube basin, with the 2-3 years before and after a maximum or minimum solar.

  8. Forecasting geomagnetic activity at monthly and annual horizons: Time series models

    NASA Astrophysics Data System (ADS)

    Reikard, Gordon

    2015-10-01

    Most of the existing work on forecasting geomagnetic activity has been over short intervals, on the order of hours or days. However, it is also of interest to predict over longer horizons, ranging from months to years. Forecasting tests are run for the Aa index, which begins in 1868 and provides the longest continuous records of geomagnetic activity. This series is challenging to forecast. While it exhibits cycles at 11-22 years, the amplitude and period of the cycles varies over time. There is also evidence of discontinuous trending: the slope and direction of the trend change repeatedly. Further, at the monthly resolution, the data exhibits nonlinear variability, with intermittent large outliers. Several types of models are tested: regressions, neural networks, a frequency domain algorithm, and combined models. Forecasting tests are run at horizons of 1-11 years using the annual data, and 1-12 months using the monthly data. At the 1-year horizon, the mean errors are in the range of 13-17 percent while the median errors are in the range of 10-14 percent. The accuracy of the models deteriorates at longer horizons. At 5 years, the mean errors lie in the range of 21-23 percent, and at 11 years, 23-25 percent. At the 1 year horizon, the most accurate forecast is achieved by a combined model, but over longer horizons (2-11 years), the neural net dominates. At the monthly resolution, the mean errors are in the range of 17-19 percent at 1 month, while the median errors lie in a range of 14-17 percent. The mean error increases to 23-24 percent at 5 months, and 25 percent at 12 months. A model combining frequency and time domain methods is marginally better than regressions and neural networks alone, up to 11 months. The main conclusion is that geomagnetic activity can only be predicted to within a limited threshold of accuracy, over a given range of horizons. This is consistent with the finding of irregular trends and cycles in the annual data and nonlinear variability in the monthly series.

  9. Solar activity and human health at middle and low geomagnetic latitudes in Central America

    NASA Astrophysics Data System (ADS)

    Mendoza, Blanca; Sánchez de La Peña, Salvador

    2010-08-01

    The study of the possible effect of solar variability on living organisms is one of the most controversial issues of present day science. It has been firstly and mainly carried on high latitudes, while at middle and low latitudes this study is rare. In the present review we focused on the work developed at middle and low geomagnetic latitudes of America. At these geomagnetic latitudes the groups consistently dedicated to this issue are mainly two, one in Cuba and the other in Mexico. The Cuban and Mexican studies show that at such latitudes there are biological consequences to the solar/geomagnetic activity, coinciding in four points: (1) the male population behave differently from the female population, (2) the most vulnerable age group to geomagnetic perturbations is that of ⩾65 years old, (3) there is a tendency for myocardial infarctions (death or occurrence) to increase one day after a geomagnetic Ap index large value or during the day of the associated Forbush decrease, and (4) the myocardial infarctions (death or occurrence) increase as the geomagnetic perturbation increases. Additionally, the Cuban group found seasonal periodicities from their data, and also that increases of female myocardial infarctions occurred before and after the day of the geomagnetic disturbance. The Mexican group found that the male sex is more vulnerable to geomagnetic perturbations and that the myocardial infarction deaths present the conspicuous cycle of ˜7 days.

  10. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<−100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3–6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  11. Effect of possible passage through Halley's magnetic tail on geomagnetic activity

    SciTech Connect

    Russell, C.T.; Phillips, J.L. ); Fedder, J.A. ); Allen, J.H.; Morris, L. ); Craig, R.A. )

    1987-10-01

    The geomagnetic aa index shows that a nonrecurrent magnetic disturbance occurred in May 1910 near the time of the passage of comet Halley through inferior conjunction. Examination of ground-based magnetograms from May 18 to 20, 1910, shows that this disturbance consisted, in part, of a negative bay of the depth expected if the magnetopause currents had ceased. The duration of this bay could have been caused by the Earth's entry into a cometary tail lobe width of about 10{degrees} km. Other features during this period suggest that the Earth may have also earlier grazed the other lobe of the cometary tail and passed through the plasma sheet. If this interpretation is true, the entire region of interaction was about 6 {times} 10{sup 6} km wide 24 {times} 10{sup 6} km downstream from the nucleus. MHD computer simulations of the solar wind interaction with Halley to 7 {times} 10{sup 6} km downstream are consistent with the inferred tail properties. The fact that the signature of the interaction was observed earlier than expected suggests that momentum transfer occurred from the comet to the solar wind over a very extended region of space around the comet. If this momentum transfer deflected the solar wind flow with the 45-km/s transverse velocity of the comet, the observed timing would be consistent with an initially radially flowing solar wind of 750 km/s or a solar wind flow 4{degrees} from the radial of 500 km/s.

  12. Different geomagnetic indices as an indicator for geo-effective solar storms and human physiological state

    NASA Astrophysics Data System (ADS)

    Dimitrova, Svetla

    2008-02-01

    A group of 86 healthy volunteers were examined on each working day during periods of high solar activity. Data about systolic and diastolic blood pressure, pulse pressure, heart rate and subjective psycho-physiological complaints were gathered. MANOVA was employed to check the significance of the influence of three factors on the physiological parameters. The factors were as follows: (1) geomagnetic activity estimated by daily amplitude of H-component of the local geomagnetic field, Ap- and Dst-index; (2) gender; and (3) the presence of medication. Average values of systolic, diastolic blood pressure, pulse pressure and subjective complaints of the group were found to increase significantly with geomagnetic activity increment.

  13. Croatian Geomagnetic Surveys 2004-2009

    NASA Astrophysics Data System (ADS)

    Brki?, Mario; Jungwirth, Enio; Ugar, Danijel .; Pavasovi?, Marko

    2010-05-01

    The setup and surveys of Croatian Geomagnetic Repeat Stations Network and the dense Croatian Geomagnetic Network for Field Mapping was presented. Regular and new field practices that include CROPOS coordinates determination and D-I-F Survey software utilization were described. Experiences encountered on the Adriatic volcanic island Jabuka, as well as on many terra rossa sights in Dalmatia and Istria, and the influence of artificial noises, were investigated. The reduced geomagnetic field of 2007.5 and its annual variation for the territory of Croatia was presented. Keywords: geomagnetic repeat station network, geomagnetic network for field mapping, geomagnetic surveys.

  14. a Millennium of Geomagnetism

    NASA Astrophysics Data System (ADS)

    Stern, David P.

    2002-11-01

    The history of geomagnetism began around the year 1000 with the discovery in China of the magnetic compass. Methodical studies of the Earth's field started in 1600 with William Gilbert's De Magnete [Gilbert, 1600] and continued with the work of (among others) Edmond Halley, Charles Augustin de Coulomb, Carl Friedrich Gauss, and Edward Sabine. The discovery of electromagnetism by Hans Christian Oersted and André-Marie Ampére led Michael Faraday to the notion of fluid dynamos, and the observation of sunspot magnetism by George Ellery Hale led Sir Joseph Larmor in 1919 to the idea that such dynamos could sustain themselves naturally in convecting conducting fluids. From that came modern dynamo theory, of both the solar and terrestrial magnetic fields. Paleomagnetic studies revealed that the Earth's dipole had undergone reversals in the distant past, and these became the critical evidence in establishing plate tectonics. Finally, the recent availability of scientific spacecraft has demonstrated the intricacy of the Earth's distant magnetic field, as well as the existence of magnetic fields associated with other planets and with satellites in our solar system.

  15. The AAS Workforce Survey

    NASA Astrophysics Data System (ADS)

    Postman, Marc; Norman, D. J.; Evans, N. R.; Ivie, R.

    2014-01-01

    The AAS Demographics Committee, on behalf of the AAS, was tasked with initiating a biennial survey to improve the Society's ability to serve its members and to inform the community about changes in the community's demographics. A survey, based in part on similar surveys for other scientific societies, was developed in the summer of 2012 and was publicly launched in January 2013. The survey randomly targeted 2500 astronomers who are members of the AAS. The survey was closed 4 months later (April 2013). The response rate was excellent - 63% (1583 people) completed the survey. I will summarize the results from this survey, highlighting key results and plans for their broad dissemination.

  16. Section AA Pre2004 Fire, Section AA 2009, Section AA, South ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Section A-A Pre-2004 Fire, Section A-A 2009, Section A-A, South Elevation - Boston & Maine Railroad, Berlin Branch Bridge #148.81, Formerly spanning Moose Brook at former Boston & Maine Railroad, Gorham, Coos County, NH

  17. Following the geomagnetic activity: events on September and October (1999)

    NASA Astrophysics Data System (ADS)

    Blanco, J. J.; Hidalgo, M. A.; Rodrguez-Pacheco, J.; Medina, J.; Sequeiros, J.; Nieves-Chinchilla, T.

    2006-12-01

    On 21-22 October 1999 a very intense geomagnetic storm (DST index: -237 nT) was detected. This event was associated with a High Speed Stream (HSS) and an interplanetary coronal mass ejection. Before and after this event, the interplanetary magnetic field showed an inversion probably associated with Heliospheric Current Sheet (HCS) crossings. One month before (21-22 September) a strong geomagnetic storm (DST index: -164 nT) was detected and the solar wind conditions were similar to those observed in October, i. e. magnetic cloud, HSS and HCS crossings. Nevertheless, the October event was stronger than the September one. We have compared both events trying to clarify what caused the difference between them. This work has been supported by the Spanish Comisin Internacional de Ciencia y Tecnologa (CICYT), grant ESP2005-07290-C02-01 and ESP2006-08459 and Madrid Autonomous Community / University of Alcala grant CAM-UAH 2005/007.

  18. Solar wind control of auroral zone geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.; Mcpherron, R. L.; Searls, C.; Kivelson, M. G.

    1981-01-01

    Solar wind magnetosphere energy coupling functions are analyzed using linear prediction filtering with 2.5 minute data. The relationship of auroral zone geomagnetic activity to solar wind power input functions are examined, and a least squares prediction filter, or impulse response function is designed from the data. Computed impulse response functions are observed to have characteristics of a low pass filter with time delay. The AL index is found well related to solar wind energy functions, although the AU index shows a poor relationship. High frequency variations of auroral indices and substorm expansions are not predictable with solar wind information alone, suggesting influence by internal magnetospheric processes. Finally, the epsilon parameter shows a poorer relationship with auroral geomagnetic activity than a power parameter, having a VBs solar wind dependency.

  19. Spectrum analysis of short-period K index behaviour at high and mid-latitudes

    NASA Astrophysics Data System (ADS)

    Kotz, P. B.

    2015-01-01

    Geomagnetic activity levels during the declining phase and solar minimum period of the solar cycle are considerably different from those during the solar maximum phase. Previous studies revealed variations in the pattern of recurrent activity from cycle to cycle as well as variations in the average geomagnetic activity levels during a solar cycle. During the declining phase of a solar cycle (and solar minimum), the solar and interplanetary causes of geomagnetic activity are substantially different from those during the solar maximum phase. Co-rotating fast solar wind streams originating from large polar coronal holes, extending towards the Sun's equator, interact with the Earth's magnetosphere, resulting in recurrent geomagnetic activity particularly during solar cycle minimum periods. This is a well-known phenomenon with respect to 27.0- and 13.5-day recurrence geomagnetic activity, and it is well-known to be related to sectorial (non-axial) poloidal magnetic field structure in the Sun. Published results of the recent solar-cycle-23 minimum showed that the presence of 9.0- and 6.7-day recurrent geomagnetic activities can be attributed to the sectorial spherical harmonic structure present in the solar magnetic field. In this study we performed a wavelet and Lomb-Scargle analysis of the geomagnetic activity K index at Lerwick (LER), Hermanus (HER) and Canberra (CNB) for the period between 1960 and 2010, overlapping with solar cycles 20 to 23. Daily mean K indices are used to identify how several harmonics of the 27.0-day recurrent period change during each solar cycle when comparing high and mid-latitude geomagnetic activity, applying a 95% confidence level. In particular the behaviour of the second (13.5-day), third (9.0-day) and fourth (6.7-day) harmonics are investigated by doing a wavelet analysis of each individual year's K indices at each location. Results obtained show that particularly during solar minima the 27.0-day period is no longer detectable above the 95% confidence level, and that geomagnetic activity is in fact dominated by higher harmonics like 13.5-, 9.0- and 6.7-day periods. These findings in fact are in line with previous investigations and confirm the results obtained by researchers using other geomagnetic activity indices like aa and C9. The wavelet-spectrum analysis also reveals that during the downward phase of cycle 23 and the very long minimum of 23-24 between 2002 and 2008, the 27.0-day activity period drops below the 95% confidence level. This is confirmed by Lomb-Scargle analyses of every year's K index activity. Results obtained in this study support evidence by other investigations that this can be attributed to the lack of coronal-mass ejection (CME)-dominated solar activity during solar minima, periods characterized by strong solar dipolar magnetic fields, less sunspot numbers than at solar maxima, and multiple prominent co-rotating solar wind streams present. This analysis further confirms previous studies by other authors that the pattern of recurrent activity is dictated by the configuration of coronal holes which give rise to related high-speed streams during a solar cycle by analysing K indices at both high- and mid-latitude magnetic observatories.

  20. AAS 227: Welcome!

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    Greetings from the 227th American Astronomical Society meeting in Kissimmee, Florida! This week, along with several fellow authors from astrobites, Iwill bewritingupdates on selectedevents at themeeting and posting at the end of each day. You can follow along here or atastrobites.com, or catch ourlive-tweeted updates from the@astrobites Twitter account. The usual posting schedule for AAS Nova will resumenext week.If youre an author or referee (or plan to be!) and youre here at the meeting, consider joining us at our Author and Referee Workshop on Wednesday in the Tallahassee room, where well be sharingsome of the exciting new features of the AAS journals. You can drop intoeither of the two-hour sessions(10 AM 12 PM or 1 PM 3 PM), and there will be afree buffet lunch at noon.Heres the agenda:Morning SessionTopic Speaker10:00 am 10:05 amIntroductionsJulie Steffen10:05 am 10:35 amChanges at AAS Journals; How to Be a Successful AAS AuthorEthan Vishniac10:35 am 11:00 amThe Peer Review ProcessButler Burton11:00 am 11:15 amAAS Nova: Sharing AAS Authors Research with the Broader CommunitySusanna Kohler11:15 am 11:30 amFixing Software and Instrumentation Publishing: New Paper Styles in AAS JournalsChris Lintott11:30 am 11:45 amMaking Article Writing Easier with the New AASTeX v6.0Greg Schwarz11:45 am 12:00 pmBringing JavaScript and Interactivity to Your AAS Journal FiguresGus MuenchLunch SessionTopic Speaker12:00 pm 12:15 pmUnified Astronomy ThesaurusKatie Frey12:15 pm 12:30 pmAAS/ADS ORCID Integration ToolAlberto Accomazzi12:30 pm 12:45 pmWorldWide Telescope and Video AbstractsJosh Peek12:45 pm 01:00 pmArizona Astronomical Data Hub (AADH)Bryan HeidornAfternoon SessionTopic Speaker01:00 pm 01:05 pmIntroductionsJulie Steffen01:05 pm 01:35 pmChanges at AAS Journals; How to Be a Successful AAS AuthorEthan Vishniac01:35 pm 02:00 pmThe Peer Review ProcessButler Burton02:00 pm 02:15 pmAAS Nova: Sharing AAS Authors Research with the Broader CommunitySusanna Kohler02:15 pm 02:30 pmFixing Software and Instrumentation Publishing: New Paper Styles in AAS JournalsChris Lintott02:30 pm 02:45 pmMaking Article Writing Easier with the New AASTeX v6.0Greg Schwarz02:45 pm 03:00 pmBringing JavaScript and Interactivity to Your AAS Journal FiguresGus MuenchIf youre at the meeting but cant make the workshop, stopby the IOP booth in the Exhibit Hall (Booth #223) to learn more about the new corridors for AAS Journals and to pick up a badge pin to representyour corridor!

  1. A'a' Channel

    USGS Multimedia Gallery

    Detail of levee on an active channelized aa flow. Note the pahoehoe overflows in the levees and the level of the active flow below the tops of the levees. This lower flow level is not allowed in the commonly used

  2. Statistical Properties of Geomagnetic Activity Indices and Solar Wind Parameters

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hee; Chang, Heon-Young

    2014-06-01

    As the prediction of geomagnetic storms is becoming an important and practical problem, conditions in the Earth¡¯s magnetosphere have been studied rigorously in terms of those in the interplanetary space. Another approach to space weather forecast is to deal with it as a probabilistic geomagnetic storm forecasting problem. In this study, we carry out detailed statistical analysis of solar wind parameters and geomagnetic indices examining the dependence of the distribution on the solar cycle and annual variations. Our main findings are as follows: (1) The distribution of parameters obtained via the superimposed epoch method follows the Gaussian distribution. (2) When solar activity is at its maximum the mean value of the distribution is shifted to the direction indicating the intense environment. Furthermore, the width of the distribution becomes wider at its maximum than at its minimum so that more extreme case can be expected. (3) The distribution of some certain heliospheric parameters is less sensitive to the phase of the solar cycle and annual variations. (4) The distribution of the eastward component of the interplanetary electric field BV and the solar wind driving function BV2, however, appears to be all dependent on the solar maximum/minimum, the descending/ascending phases of the solar cycle and the equinoxes/solstices. (5) The distribution of the AE index and the Dst index shares statistical features closely with BV and BV2 compared with other heliospheric parameters. In this sense, BV and BV2 are more robust proxies of the geomagnetic storm. We conclude by pointing out that our results allow us to step forward in providing the occurrence probability of geomagnetic storms for space weather and physical modeling.

  3. Solar Influences on Geomagnetic and Related Phenomena

    NASA Technical Reports Server (NTRS)

    Vestine, E. H.

    1961-01-01

    A discussion of the geomagnetic effects of streams of electromagnetic and particular radiation from the sun. The interplay of forces between the geomagnetic field and solar streams is outlined; and the theoretical relationship between these, the solar storms, the trapped Van Allen radiations, the polar aurora, and geomagnetic field distortion are presented.

  4. On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    The aa index can be decomposed into two separate components: the leading sporadic component due to solar activity as measured by sunspot number and the residual or recurrent component due to interplanetary disturbances, such as coronal holes. For the interval 1964-2006, a highly statistically important correlation (r = 0.749) is found between annual averages of the aa index and the solar wind speed (especially between the residual component of aa and the solar wind speed, r = 0.865). Because cyclic averages of aa (and the residual component) have trended upward during cycles 11-23, cyclic averages of solar wind speed are inferred to have also trended upward.

  5. Solar and geomagnetic activity control on equatorial VHF Scintillations in the Indian region

    NASA Astrophysics Data System (ADS)

    Banola, S.; Maurya, R. N.; Prasad, D. S. V.; Rama Rao, P. S. V.

    The ionospheric plasma density irregularities are responsible for scintillation of trans-equatorial radio signals. VHF radio wave Scintillation technique is extensively used to study plasma density irregularities of sub-km size. A ground network of 14 stations were operated by Indian Institute of Geomagnetism (and one station at Waltair) under All India coordinated Programme of Ionospheric and Thermospheric Studies (AICPITS), monitoring amplitude scintillations of 244/250 MHz signal from FLEETSAT (73° E) in India for more than a solar cycle. Effect of solar and geomagnetic activity on scintillation is studied in detail. Using long series of simultaneous amplitude scintillation data at different stations for the period 1989-2000, solar cycle association of scintillation is studied. Boundary of the equatorial belt of scintillation is determined using the entire network data. Geomagnetic control on the width of the scintillation belt is studied from the latitudinal variations of scintillation occurrence separately for geomagnetic quiet and disturbed days and also for the groups of days with low, medium and high Kp values. Kp and Ap indices, characterizing the geomagnetic activity which are shown extensively related to the dynamic properties of the plasma from the sun, are examined for their association with the scintillations. It is noticed that with increase in geomagnetic activity at low and equatorial regions scintillation occurrence is inhibited. Scintillation activity under different magnetic storm conditions is studied using Dst index and classification of the various geomagnetic storms into 3 types of Aaron's criteria (Radio Science,1991), satisfying in about 70 % of cases.

  6. Geomagnetic activity influences the melatonin secretion at latitude 70 degrees N.

    PubMed

    Weydahl, A; Sothern, R B; Cornélissen, G; Wetterberg, L

    2001-01-01

    Factors other than light may affect variations in melatonin, including disturbances in the geomagnetic field. Such a possibility was tested in Alta, Norway, located at latitude 70 degrees N, where the aurora borealis is a result of large changes in the horizontal component (H) of the geomagnetic field. Geomagnetic disturbances are felt more strongly closer to the pole than at lower latitudes. Also noteworthy in Alta is the fact that the sun does not rise above the horizon for several weeks during the winter. To examine whether changes in geomagnetic activity influence the secretion of melatonin, saliva was collected from 25 healthy subjects in Alta several times during the day-night and at different times of the year. Single cosinor analyses yielded individual estimates of.the circadian amplitude and MESOR of melatonin. A 3-hour mean value for the local geomagnetic activity index, K, was used for approximately the same 24-hour span. A circadian rhythm was found to characterize both melatonin and K, the peak in K (23:24) preceding that of melatonin (06:08). During the span of investigation, a circannual variation also characterized both variables. Correlation analyses suggest that changes in geomagnetic activity had to be of a certain magnitude to affect the circadian amplitude of melatonin. If large enough (> 80 nT/3 h), changes in geomagnetic activity also significantly decreased salivary melatonin concentration. PMID:11774869

  7. Analysis of the Solar Diameter Variations at July, 1986 and the Geomagnetic Storm of March, 1989

    NASA Astrophysics Data System (ADS)

    Humberto Andrei, Alexandre; Garcia, Marcos A.; Papa, Andres R. R.; Calderari Boscardin, Sergio; Lousada Penna, Jucira; Sigismondi, Costantino

    2015-08-01

    In this work, we have a well-known event in scientific literature used to illustrate our investigation on the viability of the solar diameter variation be a precursor for the occurrence of sets of coronal mass ejections, and thus, for geomagnetic storms, as noted in previous works of our group, but now, in a time scale of a few days. The selected event was that of March 13, 1989, a strong geomagnetic storm that made the Hydro-Quebec power grid fall down by 9 hours, damaging the local economy in millions of dollars. At the same time we have investigated a time interval belonging to a solar minimum period, on July 1986, prior to the rising phase and solar maximum of Solar Cycle 22, to compare with the geomagnetic pattern, as well as with the solar diameter behavior along these periods of low solar and geomagnetic activity. We used the time series of the CERGA’s astrolabe (because its dataset is long enough as to comprise both time periods of the analysis), the geomagnetic index AP and the H geomagnetic component from the Tatuoca Magnetic Observatory (because it is near to the geomagnetic equator and with the extra aim of checking the sensitivity of its magnetometers to global events).

  8. Prediction of Geomagnetic Activity and Key Parameters in High-latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.; Lyatsky, Wladislaw; Tan, Arjun; Ridley, Aaron

    2007-01-01

    Prediction of geomagnetic activity and related events in the Earth's magnetosphere and ionosphere are important tasks of US Space Weather Program. Prediction reliability is dependent on the prediction method, and elements included in the prediction scheme. Two of the main elements of such prediction scheme are: an appropriate geomagnetic activity index, and an appropriate coupling function (the combination of solar wind parameters providing the best correlation between upstream solar wind data and geomagnetic activity). We have developed a new index of geomagnetic activity, the Polar Magnetic (PM) index and an improved version of solar wind coupling function. PM index is similar to the existing polar cap PC index but it shows much better correlation with upstream solar wind/IMF data and other events in the magnetosphere and ionosphere. We investigate the correlation of PM index with upstream solar wind/IMF data for 10 years (1995-2004) that include both low and high solar activity. We also have introduced a new prediction function for the predicting of cross-polar-cap voltage and Joule heating based on using both PM index and upstream solar wind/IMF data. As we show such prediction function significantly increase the reliability of prediction of these important parameters. The correlation coefficients between the actual and predicted values of these parameters are approx. 0.9 and higher.

  9. [The study of effects of geomagnetic disturbances at high latitudes on the intrauterine condition of fetus by cardiotocography].

    PubMed

    Shumilov, O I; Kasatkina, E A; Enikeev, A V; Khramov, A A

    2003-01-01

    The effect of geomagnetic disturbances on the intrauterine condition of the fetus in high latitudes was studied by comparing the index of fetus condition (IFC) with the heliogeophysical indices (planetary Kp index and Dst variation index). The functional state of fetus at late terms of pregnancy was assessed by the method of cardiomonitoring. The data of fetal cardiomonitoring were processed by the method of Prof. Demidov by calculating the integral IFC using a computer program. It was found that the variations in maximum IFC values (approximately 15% of the total number of cases) coincide with seasonal variations in geomagnetic disturbances. The maximum values of IFC were observed at the equinox (March-April-May, October-November), and the minimum values were registered in the period of the solstice. A comparison of IFC values with the indices of geomagnetic disturbances indicated that the IFC value was maximum in the periods of either the greatest weakening of geomagnetic activity or maximum disturbances. PMID:12723366

  10. Simulating the lunar geomagnetic variations

    NASA Astrophysics Data System (ADS)

    Stening, R. J.; Carmody, C.; Du, J.

    2002-07-01

    The equivalent circuit method is used to simulate the lunar semidiurnal geomagnetic tides. Samples of observations of the lunar geomagnetic tide are also presented, derived from analyses of hourly values of the horizontal component of the magnetic field recorded at several observatories. These are compared to the results of the simulations at different seasons. The winds used in the simulation are derived from the Global Scale Wave Model (GSWM) and from those determined by Forbes and Gillette [1982]. The calculations are only carried out for a lunar age of zero (new moon), but this still enables a comparison to be made with the observed phases of the lunar geomagnetic tide. A mostly fair agreement is obtained both for the amplitude and phase of the lunar geomagnetic tide. The agreement is generally better when winds from the Global Scale Wave Model are used rather than those from the earlier Forbes and Gillette model. The July simulation gives poorer agreement: there is corroborating evidence that the phase of the winds near the equator in July should be about 3 hours earlier than that presently given by the GSWM. The situation in December is different from other seasons both in the simulation and the observations, but agreement is difficult to achieve on account of the year-to-year variability in this season.

  11. Mantle superplumes induce geomagnetic superchrons

    NASA Astrophysics Data System (ADS)

    Olson, Peter; Amit, Hagay

    2015-07-01

    We use polarity reversal systematics from numerical dynamos to quantify the hypothesis that the modulation of geomagnetic reversal frequency, including geomagnetic superchrons, results from changes in core heat flux related to growth and collapse of lower mantle superplumes. We parameterize the reversal frequency sensitivity from numerical dynamos in terms of average core heat flux normalized by the difference between the present-day core heat flux and the core heat flux at geomagnetic superchron onset. A low-order polynomial fit to the 0-300 Ma Geomagnetic Polarity Time Scale (GPTS) reveals that a decrease in core heat flux relative to present-day of approximately 30% can account for the Cretaceous Normal Polarity and Kiaman Reverse Polarity Superchrons, whereas the hyper-reversing periods in the Jurassic require a core heat flux equal to or higher than present-day. Possible links between GPTS transitions, large igneous provinces (LIPs), and the two lower mantle superplumes are explored. Lower mantle superplume growth and collapse induce GPTS transitions by increasing and decreasing core heat flux, respectively. Age clusters of major LIPs postdate transitions from hyper-reversing to superchron geodynamo states by 30-60 Myr, suggesting that superchron onset may be contemporaneous with LIP-forming instabilities produced during collapses of lower mantle superplumes.

  12. Climate determinism or Geomagnetic determinism?

    NASA Astrophysics Data System (ADS)

    Gallet, Y.; Genevey, A.; Le Goff, M.; Fluteau, F.; Courtillot, V.

    2006-12-01

    A number of episodes of sharp geomagnetic field variations (in both intensity and direction), lasting on the order of a century, have been identified in archeomagnetic records from Western Eurasia and have been called "archeomagnetic jerks". These seem to correlate well with multi-decadal cooling episodes detected in the North Atlantic Ocean and Western Europe, suggesting a causal link between both phenomena. A possible mechanism could be a geomagnetic modulation of the cosmic ray flux that would control the nucleation rate of clouds. We wish to underline the remarkable coincidence between archeomagnetic jerks, cooling events in Western Europe and drought periods in tropical and sub-tropical regions of the northern hemisphere. The latter two can be interpreted in terms of global teleconnections among regional climates. It has been suggested that these climatic variations had caused major changes in the history of ancient civilizations, such as in Mesopotamia, which were critically dependent on water supply and particularly vulnerable to lower rainfall amounts. This is one of the foundations of "climate determinism". Our studies, which suggest a geomagnetic origin for at least some of the inferred climatic events, lead us to propose the idea of a "geomagnetic determinism" in the history of humanity.

  13. Correction of artificial jumps in the historical geomagnetic measurements of Coimbra Observatory, Portugal

    NASA Astrophysics Data System (ADS)

    Morozova, A. L.; Ribeiro, P.; Pais, M. A.

    2014-01-01

    The Coimbra Magnetic Observatory (International Association of Geomagnetism and Aeronomy code COI) in Portugal has a long history of observation of the geomagnetic field, spanning almost 150 yr since the first geomagnetic measurements in 1866. These long instrumental geomagnetic records provide very important information about variability of geomagnetic elements and indices, their trends and cycles, and can be used to improve our knowledge on the sources that drive variations of the geomagnetic field: liquid core dynamics (internal) and solar forcing (external). However, during the long life of the Coimbra Observatory, some inevitable changes in station location, instrument's park and electromagnetic environment have taken place. These changes affected the quality of the data collected at COI causing breaks and jumps in the series of geomagnetic field components and local K index. Clearly, these inhomogeneities, typically shift-like (step-like) or trend-like, have to be corrected or, at least, minimized in order for the data to be used in scientific studies or to be submitted to international databases. In this study, the series of local K index and declination of the geomagnetic field are analysed: the former because it allows direct application of standard homogenization methods and the latter because it is the longest continuous series produced at COI. For the homogenization, visual and statistical tests (e.g. standard normal homogeneity test) have been applied directly to the local geomagnetic K index series (from 1951 to 2012). The homogenization of the monthly averages of declination (from 1867 to 2012) has been done using visual analysis and statistical tests applied to the time series of the first differences of declination values, as an approximation to the first time derivative. This allowed not only estimating the level of inhomogeneity of the studied series but also detecting the highly probable homogeneity break points. These points have been cross-checked with the metadata, and the COI series have been compared with reference series from the nearest geomagnetic stations and, in the case of declination series, from the recent geomagnetic field model COV-OBS to set up the required correction factors. As a result, the homogenized series measured in COI are considered to be essentially free of artificial shifts starting from the second half of the 20th century, and ready to be used by the scientific community.

  14. Geomagnetic activity associated with Earth passage of interplanetary shock disturbances and coronal mass ejections

    SciTech Connect

    Gosling, J.T.; McComas, D.J.; Phillips, J.L.; Bame, S.J. )

    1991-05-01

    Previous work indicates that virtually all transient shock wave disturbances in the solar wind are driven by fast coronal mass ejection events (CMEs). Using a recently appreciated capability for distinguishing CMEs in solar wind data in the form of counterstreaming solar wind electron events, this paper explores the overall effectiveness of shock wave disturbances and CMEs in general in stimulating geomagnetic activity. The study is confined to the interval from mid-August 1978 through mid-October 1982, spanning the last solar activity maximum, when ISEE 3 was in orbit about the L1 Lagrange point 220 R{sub e} upstream from Earth. The authors find that all but one of the 37 largest geomagnetic storms in that era were associated with Earth passage of CMEs and/or shock disturbances, with the large majority of these storms being associated with interplanetary events where Earth encountered both a shock and the CME driving the shock (shock/CME events). Although CMEs and/or shock disturbances were increasingly the cause of geomagnetic activity as the level of geomagnetic activity increased, many smaller geomagnetic disturbances were unrelated to these events. Further, approximately half of all CMEs and half of all shock disturbances encountered by Earth did not produce any substantial geomagnetic activity as measured by the planetary geomagnetic index Kp. The geomagnetic effectiveness of Earth directed CMEs and shock wave disturbances was directly related to the flow speed, the magnetic field magnitude, and the strength of the southward (GSM) field component associated with the events. The initial speed of a CME close to the Sun appears to be the most crucial factor in determining if an earthward directed event will be effective in exciting a large geomagnetic disturbance.

  15. Theoretical effects of geomagnetic activity on thermospheric tides

    SciTech Connect

    Fesen, C.G.; Richmond, A.D.; Roble, R.G.

    1993-09-01

    The theoretical effects of auroral activity on thermospheric tides during equinox solar cycle minimum are investigated using simulations from the National Center for Atmospheric Research thermosphere-ionosphere general circulation model. One set of model runs examined the effects of increasing levels of geomagnetic activity on the neutral horizontal winds and temperatures. A second set of model runs examined the generation of diurnal and semidiurnal waves in the neutral horizontal winds and temperatures by solar forcing, auroral forcing, and waves propagating vertically from the lower atmosphere. The model simulations were made for four levels of geomagnetic activity, parameterized principally by the total hemispheric power index and the potential drop across the polar cap. The resulting neutral horizontal wind and temperature fields were examined at geographic latitudes of 17.5{degrees}N, 42.5{degrees}N, and 67.5{degrees}N at 70{degrees}W longitude. The modeled response to the level of geomagnetic activity varies with altitude and latitude: the effects tend to maximize at high altitudes and high latitudes and penetrate lower in altitude as geomagnetic activity increases. The simulated mean temperatures increase and the mean winds become more southward and westward at all latitudes with increasing auroral activity. In the upper thermosphere, the model diurnal temperature amplitudes decrease with increasing activity, while the diurnal meridional wind amplitudes increase. The modeled semidiurnal winds are strongly affected by the level of geomagnetic activity, while the semidiurnal temperatures are not. Analysis of the second set of model simulations focusing on the generation of the tidal waves indicates that the tidal response to auroral activity is largely determined by the interference between the waves due to upward propagating tides and in situ solar forcing and those generated by the auroral momentum and energy sources. 28 refs., 19 figs.

  16. AAS 227: Day 4

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    Editors Note:This week were at the 227th AAS Meeting in Kissimmee, FL. Along with several fellow authors from astrobites.com, I will bewritingupdates on selectedevents at themeeting and posting at the end of each day. Follow along here or atastrobites.com, or catch ourlive-tweeted updates from the@astrobites Twitter account. The usual posting schedule for AAS Nova will resumenext week.Welcome to Day 4 of the winter American Astronomical Society (AAS) meeting in Kissimmee! Several of us are attending the conference this year, and we will report highlights from each day here on astrobites. If youd like to see more timely updates during the day, we encourage you to follow @astrobites on twitter or search the #aas227 hashtag.Helen B. Warner Prize: Origins of Structure in Planetary Systems (by Erika Nesvold)Another excellent prize lecture started off todays sessions. The Helen B. Warner Prize is awarded for achievement in observational or theoretical astrophysics by a young researcher (no more than eight years after their Ph.D.). This years Warner Prize was presented to Ruth Murray-Clay of UC Santa Barbara. For her award lecture, Murray-Clay told us all about planetary system architecture: the number, masses, and orbits of planets in a given system.Ruth Murray-Clay [photo from http://web.physics.ucsb.edu/ ~murray/biocv.html]The underlying question motivating this type of research is: How rare is the Solar System? In other words, how likely is it that a given planetary system will have rocky planets close to their star, gas giants farther out, and ice giants at the outer reaches of the system? Answering this question will help us solve the physics problem of how and where planets form, and will also help us on our search for other planets like Earth.The data on exoplanet population from transit and radial velocity observations and from direct imaging tell us that our Solar System is not common (many systems we observe have much more eccentric gas giants), but that doesnt mean its not typical. While we wait for more and better observations of exoplanet systems, theory can help us understand why the Solar System formed the way it did, and where to look for systems that formed the same way. For example, some of Murray-Clays previous work has shown that metal-rich stars tend to host more hot Jupiters and eccentric giant planets (very different from Solar System architecture). So if we want to find more systems like our own, we need to search around stars with low-to-moderate metallicity.Extrasolar Planets: Hosts, Interactions, Formation, and Interiors (by Caroline Morley)This session was a mashup of a variety of planetary topics ranging from solar flares to interiors to habitability.Leslie Rogers kicked off the session by presenting work done in collaboration with her student Ellen Price to constrain the composition of the ultra-short period (4 hours!?!) planet candidate KOI 1843.03 using models of the objects interior. Since its so close to the star, it can only exist without being torn apart if its very dense, which allows them to calculate that it must be iron-rich like Mercury!Next Kevin Thielen, an undergrad at Eckerd College, presented results from a summer project to apply a variable polytrope index to planet models. Tom Barclay then showed models that demonstrate the huge effect that having giant planets in the outer solar system has on the formation of terrestrial planets. He finds that without Jupiter and Saturn, more planets would form (8 instead of 3-4!) and giant impacts (like the moon-forming impact) would be more frequent but less energetic.Aomawa Shields shifted to discuss her 3D GCM models to determine the orbital configurations that would lead to liquid water on the surface of the planet Kepler-62f. She determines the effect of eccentricity, axis tilt (obliquity), and rotation rate on habitability. Edward Guinan brought us closer to home discussing the potential for superflares solar flares up to hundreds of times more energetic than normalin our solar system. Analyses of Kepler data suggest that these flares likely happen every 300-500 years in Sunlike stars (way more often than previously thought!), and would devastate communications systems on Earth (and hurt astronauts in space).Peter Buhler and Taisiya Kopytova finished up the session. Peter showed how he used Spitzer secondary eclipses and MESA models to determine the tidal love number and core mass of HAT-P-13b. Taisiya presented her thesis work on observations of brown dwarfs and low-mass stars. She shows that in many cases, particularly for young objects and cold objects, the models for these objects do not fit the data very well!Press Conference: Sloan Digital Sky Survey (SDSS) IV (by Susanna Kohler)The final press conference of the meeting was all about the fourth generation of the Sloan Digital Sky Survey.In the opening talk, Michael Blanton (New York University) presented some early results from SDSS-IV, which is slated to run from 2014 to 2020. The major components to SDSS-IV are extended Baryon Oscillation Spectroscopic Survey (eBOSS), a cosmological survey of quasars and galaxies; APO Galactic Evolution Experiment (APOGEE-2), a stellar survey of the Milky Way; and Mapping Nearby Galaxies at APO (MaNGA), a survey that will map the detailed internal structure of nearly 10,000 nearby galaxies.Next up was Melissa Ness (Max Planck Institute for Astronomy), speaking about APOGEEs creation of the first global age map of the Milky Way. APOGEE obtained the spectra for 70,000 red giant stars. These spectra, combined with the stars light curves, allowed the team to infer the ages of these stars distributed across the Milky Way galaxy. The resulting map is shown in the video below. From this map, Ness says its pretty clear: the Milky Way started as a small disk, and its expanded out from there, since. Our galaxy grew, and it grew up by growing out. Heres the press release. This is a big 3D map showing the age of stars in the Milky Way the latest from #aas227: https://t.co/HiPbm9eW6J pic.twitter.com/DqG6NNsPTU jonathan jb webb (@jjbw) January 8, 2016Francesco Belfiore (University of Cambridge) gave the next talk, cleverly titled Proof That Some Galaxies Are LIERs. The title is a play on the astrophysical source known as a LINER, or Low-Ionization Nuclear Emission-line Region an area within a galactic center that displays line emission from weakly ionized or neutral atoms. These have commonly been interpreted as being a wimpy active galactic nucleus (AGN). But a closer look with MaNGA, which is able to take spectroscopic data for the whole galaxy at once, has revealed that these sources are actually distributed throughout the galaxy, rather than being nuclear hence, no N: these galaxies are LIERs. Instead of AGN, the sources may be newly born white dwarfs. Heres the press release.Artists conception of the changing look quasar as it appeared in early 2015. [Dana Berry / SkyWorks Digital, Inc.; SDSS collaboration]The final speaker was Jessie Runnoe (Pennsylvania State University), who captured everyones attention with the topic of changing look quasars. We know that quasars can transition from a bright state, where active accretion onto the galaxys central supermassive black hole is visible in their emission spectrum, to a dim state, where they look like a normal galaxy. But SDSS has just observed the quasar SDSS J1011+5442 turn off within the span of just 10 years. Based on the data, the team concludes that this quasar exhausted the supply of gas in its immediate vicinity, turning off when there was no longer anything available to accrete. Runnoe showed an awesome animation of this process, which you can check out here. Heres the press release.Coffee, Black Holes, Editors and Beer: The Science-Writing Life (by Susanna Kohler)This talk was a part of the series Beyond the Academy: Showcasing Astronomy Alumni in Non-Academic Careers. Matthew Francis is a former academic scientist (with a PhD in physics and astronomy) who transitioned to being a freelance science writer. Wearing a distinctive bowler hat, Francis talked to a room full of students (and some non-students!) about what its like to be a science writer. Here are some highlights from among his recommendations and comments.A day in the life of a science writer.About the mechanics of freelancing:Some sample numbers: he wrote 73 articles in 2015, for 12 different publications. These vary in length and time invested. He supports himself fully by freelancing.The time between pitching a story and getting it published can vary between a few hours for online news stories to months for feature articles.The answer to the question, What do science writers do all day? (see photo)About transitioning into science writing:If youre interested in a science writing career, start blogging now to build up a portfolio.Use your training! As a researcher, you can read plots, understand scientific articles, and talk to scientists as colleagues. These are great strengths.About writing for the public:Theres a difference in writing for academics and the public: when writing for academics, youre trying to bring them up to your level. When writing for the public, thats probably not the goal.That said, on the subject of dumbing down: If you think your audience is somehow deficient, youve already failed.writing for the web: youll make fundamental spelling/grammar errors, youll find them only when you read the published post. Truth! #aas227 astrobites (@astrobites) January 8, 2016At the end of the session, Francis told us what he considers to be the best part of being a science writer: getting to tell people something that theyve never heard before. Getting it right is communicating a mundane fact to you that is an astounding surprise to your audience.Plenary Talk: News on the Search for Milky Way Satellite Galaxies (by Susanna Kohler)The second-to-last plenary talk of the meeting was given by Keith Bechtol, John Bahcall fellow at University of Wisconsin-Madison. Bechtol spoke about the recent discovery of new satellite galaxies of the Milky Way. Dwarf galaxies orbiting the Milky Way are often hard to spot because they are so faint while globular clusters have mass-to-light ratios of around 1, the ultra-faint satellites around the Milky Way can have mass-to-light ratios of hundreds or thousands! A combination of better facilities and improved analysis techniques has been lengthening the list of known Milky Way satellites, however: SDSS took us from ~10 to ~30 in the last ten years, and facilities like the Dark Energy Survey Camera (DES), Pan-STARRS 1, SkyMapper, and Hyper Suprime-Cam pushed that number to ~50 in 2015.Bechtol plenary on the discovery of new MW satellites #aas227 pic.twitter.com/3GH0Sd2J8c Matthias Steinmetz (@GalacticRAVE) January 8, 2016The new candidates discovered with DES are all less luminous and more distant than previous satellites found. One interesting aspect of this sample is that 15/17 of the candidates fall in the southern half of the DES footprint, and are located near the Large and Small Magellanic Clouds. This anisotropy is not thought to be a selection effect so is it coincidence, or could they possibly be satellites of satellites? Were not sure yet!Why do we care about finding Milky Way satellites? There are lots of reasons, but one of the biggest is that they may help us to unravel some of the mysteries of dark matter. These faint-but-massive galaxies were probably born in the Milky Ways dark-matter halo, and they could be great places to indirectly detect dark matter. In addition, theres the missing satellite problem the phenomenon wherein the cold-dark-matter model predicts there should be hundreds of satellites around the Milky Way, yet weve only found a few dozen. Finding more of these galaxies would help clear up whether its the theory or the observations that are wrong.One more time, it shouldnt be called the Missing Satellite Problem. The theorists have a Satellite Overabundance Problem. #aas227 Peter Yoachim (@PeterYoachim) January 8, 2016Overall, Bechtol declares, its been an exciting year for the discovery of new Milky Way satellites, and with new surveys and facilities still in development, the future looks promising as well!Hack Day (by Meredith Rawls)A large contingent of astronomers spent our Friday working on small projects or chunks of larger projects that could be accomplished in a day. Astrobites has written about hack days before. Look for a dedicated recap post with all the great projects later in January!

  17. NM-MT network and space dangerous phenomena, 1. Principles of major geomagnetic storms forecasting

    NASA Astrophysics Data System (ADS)

    Dorman, L.; Pustil Nik, L.; Sternlieb, A.; Zukerman, I.

    According to NOAA Space Weather Scales, geomagnetic storms of scales G5 (3- hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) are dangerous for people technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others). To prevent these serious damages will be very important to forecast dangerous geomagnetic storms. In many papers it was shown that in principle for this forecasting can be used data on CR intensity and CR anisotropy changing before SC of major geomagnetic storms accompanied by sufficient Forbush-decreases (e.g., Dorman et al., 1995, 1999). In this paper we consider over 100 major geomagnetic storms and for each case we analyze hourly data of many NM for 8 days with SC in the 4-st day of 8 days period (so before SC we have at least 3 full days). We- determine what part of major geomagnetic storms is accompanied CR intensity and CR anisotropy changing before SC, and what part of major geomagnetic storms does not show any features what can be used for forecasting. We estimate also how these parts depend from the index of geomagnetic activity Kp. This research is partly supported by the INTAS grant 00-0810. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, 49A, 136-144 (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their prediction", Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, 6, 476-479 (1999).

  18. No covariation between the geomagnetic activity and the incidence of acute myocardial infarction in the polar area of northern Sweden

    NASA Astrophysics Data System (ADS)

    Messner, T.; Hggstrm, I.; Sandahl, I.; Lundberg, V.

    2002-05-01

    This study was undertaken to investigate whether there was any relation between the aurora borealis (measured as the geomagnetic activity) and the number of acute myocardial infarctions (AMI) in the northern, partly polar, area of Sweden. The AMI cases were collected from The Northern Sweden MONICA (multinational MONItoring of trends and determinants of CArdiovascular disease) AMI registry between 1985 and 1998, inclusive, and the information on the geomagnetic activity from continuous measurements at the Swedish Institute of Space Physics, Kiruna. In the analyses, both the relation between the individual AMI case and ambient geomagnetic activity, and the relation between the mean daily K index and the daily number of AMI cases were tested. We found no statistically significant relation between the number of fatal or non-fatal AMI cases, the number of sudden deaths or the number of patients with chest pain without myocardial damage, and geomagnetic activity. Our data do not support a relation between the geomagnetic activity and AMI.

  19. A'a' Channel

    USGS Multimedia Gallery

    An a'a' channel near the Royal Gardens subdivision on Kilauea Volcano, Hawaii. The flows in the background are from the 1980s. Note that the flow level is below the levees and the pahoehoe overflows emplaced on top of the a'a'.  If lava has the right viscosity, it can travel across a landscape...

  20. Worldwide Geomagnetic Data Collection and Management

    NASA Astrophysics Data System (ADS)

    Mandea, Mioara; Papitashvili, Vladimir

    2009-11-01

    Geomagnetic data provided by different platforms piece together a global picture of Earth's magnetic field and its interaction with geospace. Furthermore, a great diversity of the geomagnetic field changes, from secular (over decades to centuries) to short time variations (down to minutes and seconds), can be detected only through continued observations. An international effort to watch and record geomagnetic changes first began in the 1830s with a network of scientific observers organized by Karl Friedrich Gauss in Germany, and this effort has continued since then. One of the most remarkable achievements in understanding the geomagnetic field morphology and time behavior was made possible by the International Geophysical Year (IGY), an exploration and research effort that lasted for 18 months, starting on 1 July 1957. The IGY encompassed 11 geoscience disciplines, including geomagnetism. The IGY has represented a giant step forward in the quality and quantity of worldwide geomagnetic measurements, as well as in the widespread interest in magnetic measurements. A half century of probing the geomagnetic field spatial and temporal variations has produced a number of outstanding results, and the interested reader can find recent reviews on various geomagnetic field topics (from measurements to modeling) in Encyclopedia of Geomagnetism and Paleomagnetism [Gubbins and Herrero-Bervera, 2007] or Treatise on Geophysics: Geomagnetism [Kono, 2007].

  1. Reduced nocturnal morphine analgesia in mice following a geomagnetic disturbance.

    PubMed

    Ossenkopp, K P; Kavaliers, M; Hirst, M

    1983-10-10

    Latency to respond to an aversive thermal stimulus and the degree of analgesia induced by morphine were examined in mice injected with either isotonic saline or morphine sulfate (10 mg/kg) during midscotophase of a 12:12 h LD cycle. When mean response latencies were compared to the degree of geomagnetic disturbance (Ap index) present on test days, it was found that during the geomagnetic storm on December 17th, 1982, a significant reduction (P less than 0.01) in response latency was evident in both saline- and morphine-treated mice. The reduction in response latencies was greater, and lasted longer in the morphine-treated animals. It is suggested that the pineal gland may mediate this biomagnetic effect. PMID:6646507

  2. Research on Historical Records of Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Lakhina, G. S.; Alex, S.; Tsurutani, B. T.; Gonzalez, W. D.

    In recent times, there has been keen interest in understanding Sun-Earth connection events, such as solar flares, CMEs and concomitant magnetic storms. Magnetic storms are the most dramatic and perhaps important component of space weather effects on Earth. Super-intense magnetic storms (defined here as those with Dst < -500 nT, where Dst stands for the disturbance storm time index that measures the strength of the magnetic storm) although relatively rare, have the largest societal and technological relevance. Such storms can cause life-threatening power outages, satellite damage, communication failures and navigational problems. However, the data for such magnetic storms is rather scarce. For example, only one super-intense magnetic storm has been recorded (Dst=-640 nT, March 13, 1989) during the space-age (since 1958), although such storms may have occurred many times in the last 160 years or so when the regular observatory network came into existence. Thus, research on historical geomagnetic storms can help to create a good data base for intense and super-intense magnetic storms. From the application of knowledge of interplanetary and solar causes of storms gained from the spaceage observations applied to the super-intense storm of September 1-2, 1859, it has been possible to deduce that an exceptionally fast (and intense) magnetic cloud was the interplanetary cause of this geomagnetic storm with a Dst -1760 nT, nearly 3 times as large as that of March 13, 1989 super-intense storm. The talk will focus on super-intense storms of September 1-2, 1859, and also discuss the results in the context of some recent intense storms.

  3. Semiannual variation of geomagnetic activity.

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Mcpherron, R. L.

    1973-01-01

    It is proposed that the semiannual variation in geomagnetic activity is caused by a semiannual variation in the effective southward component of the interplanetary field. The southward field arises because the interplanetary field is ordered in the solar equatorial coordinate system, whereas the interaction with the magnetosphere is controlled by a magnetospheric system. Several simple models utilizing this effective modulation of the southward component of the interplanetary field are examined. One of these closely predicts the observed phase and amplitude of the semiannual variation. This model assumes that northward interplanetary fields are noninteracting and that the interaction with southward fields is ordered in solar magnetospheric coordinates. The prediction of the diurnal variation of the strength of the interaction at the magnetopause by this model, does not, however, match the diurnal variation of geomagnetic activity as derived from ground-based data.

  4. Ice ages and geomagnetic reversals

    NASA Technical Reports Server (NTRS)

    Wu, Patrick

    1992-01-01

    There have been speculations on the relationship between climatic cooling and polarity reversals of the earth's magnetic field during the Pleistocene. Two of the common criticisms on this relationship have been the reality of these short duration geomagnetic events and the accuracy of their dates. Champion et al. (1988) have reviewed recent progress in this area. They identified a total of 10 short-duration polarity events in the last 1 Ma and 6 of these events have been found in volcanic rocks, which also have K-Ar dates. Supposing that the speculated relationship between climatic cooling and geomagnetic reversals actually exist, two mechanisms that assume climatic cooling causes short period magnetic reversals will be investigated. These two methods are core-mantle boundary topography and transfer of the rotational energy to the core.

  5. Teaching Geomagnetism in High School

    NASA Astrophysics Data System (ADS)

    Stern, D. P.

    2001-05-01

    Many high school curricula include a one-year course in Earth Sciences, often in the 9th grade (essentially pre-algebra). That is a good time to teach about geomagnetism. Not only are dipole reversals and sea-floor magnetization central to this subject, but this is a good opportunity to introduce students to magnetism and its connection to electric currents. The story of Oersted and Faraday give a fascinating insight into the uneven path of scientific discovery, the magnetic compass and William Gilbert provide a view of the beginnings of the scientific revolution, and even basic concepts of dynamo theory and its connection to solar physics can be included. A resource including all the suitable material now exists on the world-wide web at http://www-spof.gsfc.nasa.gov/earthmag/demagint.htm (home page). A 1-month unit on geomagnetism will be outlined.

  6. Correlative comparison of geomagnetic storms and auroral substorms using geomagnetic indeces. Master's thesis

    SciTech Connect

    Cade, W.B.

    1993-06-01

    Partial contents include the following: (1) Geomagnetic storm and substorm processes; (2) Magnetospheric structure; (3) Substorm processes; (4) Data description; (5) Geomagnetic indices; and (6) Data period and data sets.

  7. Global geomagnetic field mapping - from secular variation to geomagnetic excursions

    NASA Astrophysics Data System (ADS)

    Panovska, Sanja; Constable, Catherine

    2015-04-01

    The main source of the geomagnetic field is a self-sustaining dynamo produced by fluid motions in Earth's liquid outer core. We study the spatial and temporal changes in the internal magnetic field by mapping the time-varying geomagnetic field over the past 100 thousand years. This is accomplished using a new global data set of paleomagnetic records drawn from high accumulation rate sediments and from volcanic rocks spanning the past 100 thousand years (Late Pleistocene). Sediment data comprises 105 declination, 117 inclination and 150 relative paleointensity (RPI) records, mainly concentrated in northern mid-latitudes, although some are available in the southern hemisphere. Northern Atlantic and Western Pacific are regions with high concentrations of data. The number of available volcanic/archeomagnetic data is comparitively small on the global scale, especially in the Southern hemisphere. Temporal distributions show that the number of data increases toward more recent times with a good coverage for the past 50 ka. Laschamp excursion (41 ka BP) is well represented for both directional and intensity data. The significant increase in data compared to previous compilations results in an improvement over current geomagnetic field models covering these timescales. Robust aspects of individual sediment records are successfully captured by smoothing spline modeling allowing an estimate of random uncertainties present in the records. This reveals a wide range of fidelities across the sediment magnetic records. Median uncertainties are: 17 for declination (range, 1 to 113), 6 for inclination (1 to 50) and 0.4 for standardized relative paleointensity (0.02 to 1.4). The median temporal resolution of the records defined by the smoothing time is 400 years (range, 50 years to about 14 kyr). Using these data, a global, time-varying, geomagnetic field model is constructed covering the past 100 thousand years. The modeling directly uses relative forms of sediment declination and paleointensity variation without prior calibration. The procedure is sensitive to the starting model for the inversion and it is, therefore, important to use absolute observations to initialize the calibration factors. Global geomagnetic field evolution is investigated in terms of changes in the field morphology at the core-mantle boundary, with particular interest in following the location of reconstructed flux lobes, determining need for any longitudinal structure and hemispheric asymmetry. The Laschamp excursion behavior suggests a time-transgressive process, either a true geomagnetic field feature or a result of age inconsistencies in the underlying data. An extreme axial dipole low is associated with the Laschamp excursion, but other reported excursions during the past 100 ka do not exhibit such pronounced dipole lows. Existing field studies extending back 10 thousand years show greater geomagnetic variability in the southern hemisphere than in the north, and lower average field strength. Modeling results are used to test whether hemispheric asymmetry in secular variation and the time-averaged field persist on this time scale, whether there are detectable differences in growth versus decay rates for the axial dipole.

  8. The origin of geomagnetic jerks.

    PubMed

    Bloxham, Jeremy; Zatman, Stephen; Dumberry, Mathieu

    2002-11-01

    Geomagnetic jerks, which in the second half of the twentieth century occurred in 1969 (refs 1, 2), 1978 (refs 3, 4), 1991 (ref. 5) and 1999 (ref. 6), are abrupt changes in the second time-derivative (secular acceleration) of the Earth's magnetic field. Jerks separate periods of almost steady secular acceleration, so that the first time-derivative (secular variation) appears as a series of straight-line segments separated by geomagnetic jerks. The fact that they represent a reorganization of the secular variation implies that they are of internal origin (as has been established through spherical harmonic analysis), and their short timescale implies that they are due to a change in the fluid flow at the surface of the Earth's core (as has also been established through mapping the time-varying flow at the core surface). However, little is understood of their physical origin. Here we show that geomagnetic jerks can be explained by the combination of a steady flow and a simple time-varying, axisymmetric, equatorially symmetric, toroidal zonal flow. Such a flow is consistent with torsional oscillations in the Earth's core, which are simple oscillatory flows in the core that are expected on theoretical grounds, and observed in both core flow models and numerical dynamo models. PMID:12422214

  9. Possible Geomagnetic and Environmental Symptoms in the Area of Athens During the Solar Cycle No 22

    NASA Astrophysics Data System (ADS)

    Nastos, P. T.; Paliatsos, A. G.; Korbakis, G. K.; Tritakis, V. P.; Bergiannaki, A.; Psarros, K.; Paparrigopoulos, P.; Stafanis, K.

    The goal of this research is to confirm possible influences of environmental and geomagnetic variability in psychiatric hygiene of sensitive and heavily psychological patients. Three yearly samples of psychological patients consisted by four thousand cases (4000) each have been studied. The patients have been filed by the psychiatric clinic of the Eginition hospital in Athens where the three samples have been compiled during three very characteristic years of the No 22 11-year cycle, the maximum (1989), the minimum (1996) and one intermediate year of the descending branch (1994). A file with five to eight psychological symptoms like depression, sleep disturbance anxiety, aggressiveness etc. is attached to every patient. Each of these symptoms is correlated to the local geomagnetic index (k-index), the international geomagnetic index (Dst) and the environmental index (DI, Discomfort Index) in both daily and monthly basis. A clear seasonal variation in almost all symptoms and samples is present with maximum at the end of summer (August/September) and minimum at the end of winter (February-March). In addition very significant correlations among DI, Dst and some psychological symptoms appear. The main conclusion is that meteorological and geomagnetic factors play a significant role in the formation of sensitive psychological patients, behavior

  10. The Geomagnetic Field During a Reversal

    NASA Technical Reports Server (NTRS)

    Heirtzler, James R.

    2003-01-01

    By modifying the IGRF it is possible to learn what may happen to the geomagnetic field during a geomagnetic reversal. If the entire IGRF reverses then the declination and inclination only reverse when the field strength is zero. If only the dipole component of the IGRF reverses a large geomagnetic field remains when the dipole component is zero and he direction of the field at the end of the reversal is not exactly reversed from the directions at the beginning of the reversal.

  11. Restoration project of geomagnetic survey in Latvia

    NASA Astrophysics Data System (ADS)

    Burlakovs, J.; Lembere, I.

    2003-04-01

    THE RESTORATION PROJECT OF GEOMAGNETIC SURVEY IN LATVIA J. Burlakovs, I. Lembere State Land Service of Latvia, Geodesy Board juris.burlakovs@gp.vzd.gov.lv / Fax: +371-7612736 The aim of geomagnetic survey measurements is to study the geomagnetic field at global, regional as well as local scales. To determine secular changes of the geomagnetic field it is very important to do a lot of regular field work. Recalculation and comparison of measured data for corrections must be made using the observatory or magnetic station data collected nearby the investigated area in the real-time. Field geomagnetic survey measurements in Latvia have not been made since 1991. The State Land Service of Latvia, the Geodesy Board plans to restart such kind of measurements in Latvia. The repeat station network must be renewed, regular magnetic declination, inclination and total field intensity data must be gathered, compared with the observatory data and secular changes of the geomagnetic field discovered. It is also possible to do regional correlations for data to determine future trends of the geomagnetic field changes. The detection of geomagnetic anomalies and the reason of the existence of those at particular territories could be made. Such kind of measurements demands the highest accuracy and therefore is necessary to cooperate with geomagnetic research network groups in neighbouring areas - Estonia, Finland and Poland, where permanent magnetic stations are situated. One permanent magnetic station also could be established in Latvia to do permanent recordings of geomagnetic field components, which give the possibility to do regional corrections for separate measurement recordings in the field. Geomagnetic field studies are important for cartography, navigational and military needs, also it is possible to use this information together with geological and geophysical data to create and specify the geological model for the territory. In future Latvia must participate within the framework of international projects, e.g. IMAGE and INTERMAGNET; it will be important step towards the geomagnetic observation network development in Europe.

  12. Geomagnetic activity during the rising phase of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Richardson, Ian G.

    2013-03-01

    As previous studies have shown, geomagnetic activity during the solar minimum following solar cycle 23 was at low levels unprecedented during the space era, and even since the beginning of the Kp index in 1932. Here, we summarize the characteristics of geomagnetic activity during the first 4 years of cycle 24 following smoothed sunspot minimum in December, 2008, and compare these with those of similar periods during earlier cycles going back to the start of Kp (cycles 17-23). The most outstanding feature is the continuing low levels of geomagnetic activity that are well below those observed during the rising phases of the other cycles studied. Even 4 years into cycle 24, geomagnetic storm rates are still only comparable to or below the rates observed during activity minima in previous cycles. We note that the storm rate during the rising phases of cycles 17-23 was correlated with the peak sunspot number (SSN) in the cycle. Extrapolating these results to the low storm rates in cycle 24 suggests values of the peak SSN in cycle 24 that are consistent with the NOAA Space Weather Prediction Center prediction of 90 10, indicating that cycle 24 is likely to be the weakest cycle since at least 1932. No severe (Dst < -200 nT) storms have been observed during the first 4 years of cycle 24 compared with 4 in the comparable interval of cycle 23, and only 10 intense (Dst < -100 nT) storms, compared with 21 in cycle 23. These storms were all associated with the passage of Interplanetary Coronal Mass Ejections (ICMEs) and/or their associated sheaths. The lack of strong southward magnetic fields in ICMEs and their sheaths, their lower speeds close to the average solar wind speed, a ~20% reduction in the number of ICMEs passing the Earth, and weaker than normal fields in corotating high-speed streams, contribute to the low levels of geomagnetic storm activity in the rise phase of cycle 24. However, the observation of an ICME with strong southward fields at the STEREO A spacecraft on July 24, 2012, which would have been highly geoeffective had it encountered the Earth, demonstrates that strong geomagnetic storms may still occur during weak solar cycles.

  13. Solar-generated quasi-biennial geomagnetic variation

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Poros, D. J.

    1977-01-01

    The existence of highly correlated quasi-biennial variations in the geomagnetic field and in solar activity is demonstrated. The analysis uses a numerical filter technique applied to monthly averages of the geomagnetic horizontal component and of the Zurich relative sunspot number. Striking correlations are found between the quasi-biennial geomagnetic variations determined from several magnetic observatories located at widely different longitudes, indicating the worldwide nature of the obtained variation. The correlation coefficient between the filtered Dst index and the filtered relative sunspot number is found to be -0.79 at confidence level greater than 99% with a time lag of 4 months, solar activity preceding the Dst variation. The correlation between the unfiltered data of Dst and those of the sunspot number is also high with a similar time lag. Such a time lag has not been discussed in the literature, and a further study is required to establish the mode of sun-earth relationship that gives this time delay.

  14. New hemispheric geomagnetic indices α with 15 min time resolution

    NASA Astrophysics Data System (ADS)

    Chambodut, Aude; Marchaudon, Aurélie; Lathuillère, Chantal; Menvielle, Michel; Foucault, Etienne

    2015-11-01

    New subauroral α15 indices are proposed. They are based on a simple reproducible algorithm which relies on an as dense as possible network of magnetic observatories in each hemisphere. At first, the variation with time of local geomagnetic activity is determined at each magnetic station. Gathering all obtained stations' precomputed values, a normalization with corrected geomagnetic latitude is determined. Then, for each 15 min interval, magnetic activity on the horizontal component is averaged out over 15 min and corrected using this normalization, before a spline modeling of the longitudinal variation in each hemisphere is applied. Hemispheric and planetary 15 min indices are then computed by arithmetic means. Preliminary statistical results, from probability distribution function over a solar cycle and superposed epoch analysis during storms conditions, show, by comparison with am geomagnetic index series, that new α15 indices are reliable in describing subauroral magnetic activity. These new indices will suit any future user, allowing either to choose the spatial description (planetary versus hemispheric) and/or to choose the temporal resolution, knowing unambiguously all their strengths and caveats.

  15. Predicting ground electric field due to geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Nair, M. C.; Pthe, C.; Kuvshinov, A. V.

    2013-12-01

    Electric field induced in the ground by geomagnetic disturbances drives currents in the power transmission grids, telecommunication lines or buried pipelines. These currents, known as Geomagnetically Induced Currents (GIC) are known to cause service disruptions. This effect is maximal at high latitudes due to the presence of strong polar electrojet currents. However both observations and models show that GIC caused by ring current intensifications also pose a risk at low- and mid-latitude locations, where majority of systems vulnerable to GIC are installed. A technique to model geoelectric field induced by the magnetospheric currents in a 3D conductivity model of the Earth is presented by Pthe & Kuvshinov (2013). We extend this work by predicting the induced geoelectric field solely based on Disturbance storm time index (Dst), a measure of ring current activity. Two major components of this effort are 1) Pre-computed 3D electromagnetic response of the ground to a unit magnetopsheric (P01) source and 2) Forecasted Dst data (Temerin & Li, 2002; 2006) from Advanced Composition Explorer (ACE) satellite at the L1 Lagrange point. Depending on the solar wind speed, the Dst forecasts are available approximately 1 hour in advance. The pre-computed response function for a site is multiplied by the Dst data in frequency domain to obtain predicted electric field for that location. Validating our approach, the predicted geoelectric field compares favorably with observed data from an ocean bottom electromagnetic array in the Pacific Ocean during the geomagnetic storm of April 2000. We also compare data from USArray magnetotelluric stations operational during the geomagnetic storm of October 2011. In this case, the results are site specific, with varying degrees of model fit. This indicates the influence of local surface conductivity inhomogeneities on the observed geoelectric data. Averaging data from adjacent stations seems to improve the fit with the prediction.

  16. Electric utility industry experience with geomagnetic disturbances

    SciTech Connect

    Barnes, P.R.; Rizy, D.T.; McConnell, B.W. ); Taylor, E.R. Jr. ); Tesche, F.M.

    1991-09-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems' responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration. 49 refs.

  17. Electric utility industry experience with geomagnetic disturbances

    SciTech Connect

    Barnes, P.R.; Rizy, D.T.; McConnell, B.W.; Taylor, E.R. Jr.; Tesche, F.M.

    1991-09-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems` responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration. 49 refs.

  18. Electric Utility Industry Experience with Geomagnetic Disturbances

    SciTech Connect

    Barnes, P.R.

    1991-01-01

    A geomagnetic disturbance (GMD) by its nature occurs globally and almost simultaneously. Severe geomagnetic storms cause problems for electric power systems. The vulnerability of electric power systems to such events has apparently increased during the last 10 to 20 years because power system transmission lines have become more interconnected and have increased in length and because power systems are now operated closer to their limits than in the past. In this report, the experience of electric utilities during geomagnetic storms is examined and analyzed. Measured data, effects on power system components, and power system impacts are considered. It has been found that electric power systems are susceptible to geomagnetically induced earth-surface potential gradients as small as a few (2 to 3) volts per kilometer, corresponding to a storm of K-6 intensity over an area of high earth resistivity. The causes and effects are reasonably well understood, but additional research is needed to develop a better understanding of solar-induced geomagnetic storms and the responses of power systems to these types of storms. A better understanding of geomagnetic storms and the power systems' responses to GMDs is needed so that mitigation measures can be implemented that will make power systems less susceptible to severe geomagnetic disturbances. A GMD caused by a large high-altitude nuclear detonation is similar in many ways to that of solar-induced geomagnetic storms except that a nuclear-caused disturbance would be much more intense with a far shorter duration.

  19. Snowstorm at the geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    ?op, R.

    2015-08-01

    The Sinji Vrh Geomagnetic Observatory (hereinafter the Observatory) is situated on Gora above Ajdov?ina, a highland karst plateau, in the southwestern part of Slovenia. The Observatory operates in exceptional geological and meteorological conditions due to its location. The very first measurements at the time of initial tests showed that weather fronts induce changes in the local magnetic field. The first measurements intended to determine the value of this influence were carried out at the end of summer 2011. In 2013 the first such measurements were carried out in January. This article presents the results of these measurements, showing how the snowstorm induced changes in Earth's magnetic field.

  20. Snowstorm at the geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    ?op, R.

    2015-01-01

    The Sinji Vrh Geomagnetic Observatory is situated on Gora above Ajdov?ina, a highland Karst Plateau, in the southwest part of Slovenia. The observatory operates in exceptional geological and meteorological conditions due to its location. Already first measurements at the time of initial tests showed that weather fronts induce changes in the local magnetic field. The first dedicated measurements for determining the value of this influence were carried out at the end of summer 2011. On January 2013 the first such measurements were carried out during the winter. This article presents the results of these measurements, showing how the snowstorm induced changes in the earth magnetic field.

  1. History of the geomagnetic field

    USGS Publications Warehouse

    Doell, Richard R.

    1969-01-01

    Direct measurements of the direction and strength of the earth's magnetic field have provided a knowledge of the field's form and behavior during the last few hundreds of years. For older times, however, it has been necessary to measure the magnetism of certain rocks to learn what the geomagnetic field was like. For example, when a lava flow solidifies (at temperatures near 1000??C) and cools through the Curie point of the magnetic minerals contained in it (around 500??C) it acquires a remanent magnetism that is (1) very weak, (2) very stablel, (3) paralle to the direction of the ambient geomagnetic field, and (4) proportional in intensity to the ambient field. Separating, by various analytical means, this magnetization from other 'unwanted' magnetizations has allowed paleomagnetists to study the historical and prehistorical behavior of the earth's field. It has been learned, for example, that the strength of the field was almost twice its present value 2000 years ago and that it has often completely reversed its polarity. Paleo-magnetists have also confirmed that most oceans are, geologically speaking, relatively new features, and that the continents have markedly changed their positions over the surface of the earth. ?? 1969 The American Institute of Physics.

  2. Statistical analysis and verification of 3-hourly geomagnetic activity probability predictions

    NASA Astrophysics Data System (ADS)

    Wang, Jingjing; Zhong, Qiuzhen; Liu, Siqing; Miao, Juan; Liu, Fanghua; Li, Zhitao; Tang, Weiwei

    2015-12-01

    The Space Environment Prediction Center (SEPC) has classified geomagnetic activity into four levels: quiet to unsettled (Kp < 4), active (Kp = 4), minor to moderate storm (Kp = 5 or 6), and major to severe storm (Kp > 6). The 3-hourly Kp index prediction product provided by the SEPC is updated half hourly. In this study, the statistical conditional forecast models for the 3-hourly geomagnetic activity level were developed based on 10 years of data and applied to more than 3 years of data, using the previous Kp index, interplanetary magnetic field, and solar wind parameters measured by the Advanced Composition Explorer as conditional parameters. The quality of the forecast models was measured and compared against verifications of accuracy, reliability, discrimination capability, and skill of predicting all geomagnetic activity levels, especially the probability of reaching the storm level given a previous "calm" (nonstorm level) or "storm" (storm level) condition. It was found that the conditional models that used the previous Kp index, the peak value of BtV (the product of the total interplanetary magnetic field and speed), the average value of Bz (the southerly component of the interplanetary magnetic field), and BzV (the product of the southerly component of the interplanetary magnetic field and speed) over the last 6 h as conditional parameters provide a relative operating characteristic area of 0.64 and can be an appropriate predictor for the probability forecast of geomagnetic activity level.

  3. Artificial static and geomagnetic field interrelated impact on cardiovascular regulation.

    PubMed

    Gmitrov, Juraj; Ohkubo, Chiyoji

    2002-07-01

    Spreading evidence suggests that environmental and artificial magnetic fields have a significant impact on cardiovascular system. The modulation of cardiovascular regulatory mechanisms may play a key role in observed effects. The objective was to study interrelated impacts of artificial static magnetic field (SMF) and natural geomagnetic field (GMF) on arterial baroreceptors. We studied baroreflex sensitivity (BRS) in conscious rabbits before and after 40 min of sham (n = 20) or application of Nd2-Fe14-B alloy magnets (n = 26) to the sinocarotid baroreceptor region in conjunction with GMF disturbance during the actual experiment, determined by K- and A(k)-indexes from a local geomagnetic observatory. SMF at the position of baroreceptors was 0.35 T. BRS was estimated from peak responses of mean arterial pressure (MAP) and heart rate expressed as percentages of the resting values preceding each pair of pressure (phenylephrine) and depressor drug (nitroprusside) injections. We observed a significant increase in BRS for the nitroprusside depressor test (0.78 +/- 0.1 vs. 1.15 +/- 0.14 bpm/mmHg%, initial value vs. SMF exposure, P <.0002) and a tendency for phenylephrine pressor test to increase in BRS. Prior to SMF exposure, a significant positive correlation was found between actual K index values and MAP (t = 2.33, P =.025, n = 46) and a negative correlation of the K index with BRS (t = -3.6, P =.001, n = 46). After SMF exposure we observed attenuation of the geomagnetic disturbance induced a decrease in BRS. Clinical trials should be performed to support these results, but there is a strong expectation that 0.35 T SMF local exposure to sinocarotid baroreceptors will be effective in cardiovascular conditions with arterial hypertension and decreased BRS, due to a favorable SMF effect on the arterial baroreflex. Magnets to the sinocarotid triangle along with modification of the pharmacotherapy for hypertension should be especially effective on days with intense geomagnetic disturbance, in moderating sympathetic activation and baroreceptor dysfunction. PMID:12111753

  4. North-south asymmetry in emission intensities of geomagnetic conjugate auroras

    NASA Astrophysics Data System (ADS)

    Shigenobu, K.; Taguchi, M.; Kadokura, A.; Sato, N.

    2012-12-01

    Aurora has a lot of information on the magnetosphere along a geomagnetic line. The geomagnetic field of the Earth has a shape close to a dipole, and two ground points connected by a geomagnetic field line like a pair of Husafell in Iceland and Syowa Station in Antarctica are called geomagnetic conjugate points. Auroras which appear over both points at the same time are called geomagnetic conjugate auroras. We observed auroras simultaneously at geomagnetic conjugate points and compared their intensity, shape, and appearance frequency. In general, conjugate auroras appear in a similar shape, if the magnetosphere is symmetric about the equatorial plane. However, conjugacy of aurora is not always maintained because of differences in the states of the magnetosphere and ionosphere in the northern and southern hemispheres. When, a geomagnetic field line dynamically changes in response to temporal variations in the interplanetary magnetic field orientation, it is often observed that similar auroras change suddenly into dissimilar auroras in a few minutes. One of the causes of this non-conjugate property is an asymmetric diversity in the northern and southern field -aligned acceleration regions that exist around altitudes of 3000~10000 km. Difference in the auroral intensity could result from the interhemispheric difference in the fluxes of auroral particle precipitation. Until now, geomagnetic conjugate auroras have been mainaly investigated in terms of their shape and temporal variation. Difference in the emission intensities of conjugate auroras was theoretically pointed out by Stenbaek-Nielsen [1937], but only, a few examples were observationally shown by Asozu[2006]. In order to verify the emission intensity ratio of geomagnetic conjugate auroras and to retrieve information on north-south asymmetry in the magnetosphere and ionosphere we have been observing conjugate auroras using two identical all-sky imagers installed at the conjugate points in Syowa Station and Iceland. An auroral substorm event was simultaneously observed at the conjugate points on September 9, 2011, when K-index reaches 6. In this study we compare N2+ 427.8 nm auroral intensities observed at Syowa Station and Iceland conjugate points during an event on September 9, 2011. As a result, Auroras appear in the southern hemisphere are ~40% brighter than those in the northern hemisphere. The obtained emission intensity ratio agrees well with the value theoretically expected from the north-south difference in the geomagnetic field intensity.

  5. AAS 227: Day 2

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    Editors Note:This week were at the 227th AAS Meeting in Kissimmee, FL. Along with several fellow authors from astrobites.com, I will bewritingupdates on selectedevents at themeeting and posting at the end of each day. Follow along here or atastrobites.com, or catch ourlive-tweeted updates from the@astrobites Twitter account. The usual posting schedule for AAS Nova will resumenext week.Welcome to Day 2 of the winter American Astronomical Society (AAS) meeting in Kissimmee! Several of us are attending the conference this year, and we will report highlights from each day here on astrobites. If youd like to see more timely updates during the day, we encourage you to follow @astrobites on twitter or search the #aas227 hashtag.Plenary Session: Black Hole Physics with the Event Horizon Telescope (by Susanna Kohler)If anyone needed motivation to wake up early this morning, they got it in the form of Feryal Ozel (University of Arizona) enthralling us all with exciting pictures, videos, and words about black holes and the Event Horizon Telescope. Ozel spoke to a packed room (at 8:30am!) about where the project currently stands, and where its heading in the future.The EHT has pretty much the coolest goal ever: actually image the event horizons of black holes in our universe. The problem is that the largest black hole we can look at (Sgr A*, in the center of our galaxy) has an event horizon size of 50 as. For this kind of resolution roughly equivalent to trying to image a DVD on the Moon! wed need an Earth-sized telescope. EHT has solved this problem by linking telescopes around the world, creating one giant, mm-wavelength effective telescope with a baseline the size of Earth.Besides producing awesome images, the EHT will be able to test properties of black-hole spacetime, the no-hair theorem, and general relativity (GR) in new regimes.Ozel walked us through some of the theory prep work we need to do now in order to get the most science out of the EHT, including devising new tests of GR, and performing predictive GRMHD simulations hydrodynamics simulations that include magnetic fields and full GR treatment. Ozel pointed out that one of the recent theoretical advancements in GRMHD simulations is harnessing the power of GPUs to render images in simulations; check out the tweet below for the awesome video she showed us!Watch C. Chan manipulate black hole simulation with hand motions https://t.co/O5BgaltYAu (more on the code: https://t.co/9GC46ReMGs) #aas227 Sarah Scoles (@ScolesSarah) January 6, 2016Deployment of the full EHT array is planned for early 2017, and theyve already got 10 targets selected black holes that are near enough and large enough that the EHT should be able to image their shadows. I, for one, cant wait to see the first results!Grad School and Postdocs as a Means to a Job (by Meredith Rawls)This morning session was presented by Karen Kelsky of The Professor Is In. She presented a very practical overview of the advice in her book (which this job-searching Astrobiter highly recommends). Her target audience is postdocs and graduate students who are finishing their PhDs and applying for tenure-track jobs. Karens background is in the social sciences, but she has worked with many scientists and her expertise easily transferred. Much of her writing advice also applies for undergraduates who are writing research statements and proposals to apply to graduate school. For example:What not to do, with @ProfessorIsIn #aas227 pic.twitter.com/afGAsSuPwN Meredith Rawls (@merrdiff) January 6, 2016One of Karens main takeaways is that academia is not automatically good preparation for a job search. Writing documents like cover letters, resumes, and research statements will be harder and take more time than you think, and it is important to make them top-notch. Karen was also surprised that the majority of professional astronomers at the AAS meeting carry backpacks, because she typically advises against bringing a backpack to a job interview or campus visit. She conceded that astronomy is an exception to this rule!Brown Dwarfs and Exoplanets (by Caroline Morley)I started my morning in a session near and dear to my heart on brown dwarfs. The session had four dissertation talks, showcasing each students (impressive!) work over the last 4+ years.Astrobites alumnus Ben Montet kicked off the session to talk about his recent work to study the eclipsing brown dwarf LHS 6343, discovered in Kepler data. This brown dwarf is one of the best so-called benchmark brown dwarfs that we have discovered. Unlike almost every other object, we can measure LHS 6343s mass, radius, luminosity, and metallicity. Bens Spitzer observations reveal that its a ~1100 K T dwarf.Joe Filippazzo spoke next about his work to put together a large and impressive database of 300 brown dwarfs ranging in spectral type from M to Y, stitching together literature photometry, parallaxes, and both low and high resolution spectra. He studies the effect of age on the fundamental properties of these objects, empirically without needing models! You can download the database at BDNYC.org and use Joes open-source Python package astrokit which includes the SQL management tools to use the database.Jonathan Gagn presented results from his survey to find young free-floating objects in young moving groups. These objects are really interesting because they have the masses of planets but are easier to observe since they dont have nearby stars. He is currently extending his survey from his PhD thesis to be able to find even cooler objects (literally and figuratively) in these groups.Sebastian Pineda gave a very interesting talk about his thesis work to understand auroral emission from brown dwarfs. Brown dwarfs with a range of temperatures have been observed to have both radio activity and H-alpha emission, despite their neutral atmospheres. These properties are believed to be generated by auroral emission just like aurorae on Jupiter! One of many interesting results is that cooler objects have rare and weak aurorae. Sebastian postulates that these brown dwarfs may have aurorae that are modulated by the presence of satellites (brown dwarf moons?!). Very cool idea that needs more study!The last speaker of the session was the only non-dissertation talk of the session. Nolan Grieves presented results from his statistical survey of brown dwarf companions using the MARVELS radial velocity survey and finds a brown dwarf companion occurrence rate around 0.7%.Science to Action: Thoughts on Convincing a Skeptical Public (by Meredith Rawls)This years Public Policy plenary talk was delivered by William Press from UT Austin. Many scientific stories follow a familiar narrative, and too often, scientific consensus about a hazard has been accepted by the public only after some catalyzing event like a catastrophic fire or a spike in deaths linked to smoking. Press suggested that climate change may be at the tipping point of mainstream acceptance. He also discussed how a definition of science can encompass two distinct ideas: a series of fact-based conclusions and a value judgment based on rational thinking. To illustrate this dichotomy, he posed a question to the audience:Debate about science vs about values. Speaker forced a vote by raise of hand; split 50/50 in big room. Wow. #aas227 pic.twitter.com/rdvqUuuR95 Meredith Rawls (@merrdiff) January 6, 2016Press stated that he strongly supports the top view, but it was eye-opening to see a nearly even split of raised hands. His point was that GMO labeling ultimately boils down to a value judgement, not a scientific one, and we should be careful to understand the difference. Science communicators certainly have our work cut out for us! In the broadest sense, Press takeaway for effective science communication is a two-step approach: (1) communicate the value of a rationalist approach to decision making, and (2) communicate well-established scientific results.AAS Journals Workshop for Authors RefereesFirst half (by Susanna Kohler)Disclaimer: Im an employee of the AAS, as editor of AAS Nova.This 2-hour-long author referee workshop was intended partially as an overview of what it means to be an author or a referee (in any journal), and partly as a reveal of some of the new features that are now being implemented within the AAS publishing program. Many of the presentations have been uploaded here. A few highlights from the first half:Talks about authoring articles by Ethan Vishniac, and refereeing articles by Butler BurtonIntro to AAS Nova the AASs means of sharing its authors results with the broader community by me!Discussion of the AASs new policy for software citation by Chris LintottSecond half (by Becky Nevin)In between hopping between all the amazing science sessions today I made it to the last half of a very interesting Author Referee Workshop run by AAS journals. Even with missing the first half, I can still tell that theres a lot of changes coming to AAS journals (which include ApJ, AJ, ApJS, ApJL), in particular in the way that your research will be published. All good from what I saw in particular theyve addressed the long-standing problem of how to cite astronomical software (usually produced for free by a keen member of the community). Now they give guidelines for how to do this and have even appointed a new lead editor for instrumentation software.What got me most excited though was the demonstration by Greg Schwarz of AASTex v6.0 a markup package to assist authors in preparing manuscripts intended for submission to AAS-affiliated journals i.e. super cool amazing new LaTeX commands to satisfy even the most obsessive LaTeX-er! Check it out, because it will definitely ease the pain of writing and responding to referees. In the final talk (before free lunch, score!) Gus Muench showcased the new ways that authors will be able to include interactive JavaScript figures into articles in AAS journals. You can check out some of the amazing integrations in this nifty tutorial.A Report on the Inclusive Astronomy 2015 Meeting: Community Recommendations for Diversity and Inclusion in AstronomyThis very well-attended session recapped the Inclusive Astronomy 2015 meeting (see this link for a summary!)The IA2015 meeting results can be found here.A draft of the recommendations from IA2015 is here. Note that this document, termed the Nashville Recommendations, is a living document that isnt yet finalized, and feedback is welcome.Dannie Heineman Prize: From ~ to Precision Science: Cosmology from 1995 to 2025 (by Erika Nesvold)Marc Kamionkowski of Johns Hopkins University and David Spergel of Princeton University shared this years Heineman Prize for outstanding work in astronomy, and gave an impressive tag-team overview of the progress in the field of cosmology over the past 20 years.Spergel pointed out that in 1995, cosmologists were still debating over the value of the Hubble constant, and whether or not the universe is flat. Kamionkowski pointed out that back then, cosmology was an order of magnitude game where observations lagged far behind theory. He noted that in general, theorists tend to sit around predicting things, and not much progress is made in testing those predictions, at least not within the lifetime of an individual theorist. In cosmology, however, the measurements and observations made since 1995 have been more successful and precise than anyone could have anticipated.This is thanks in part to the WMAP mission and later the Planck satellite, which measured the cosmic microwave background and collected an amazing set of data. There is excellent agreement between the data from WMAP and Planck, a triumph for observational cosmologists. Much to the surprise of Spergel and other cosmologists, a simple model of only five fundamental parameters fits these data extremely well. Twenty years later, thanks to the hard work of cosmologists, we now know that the age of the universe is 13.8 billion years, and that it is composed of roughly 4% atoms, 23% dark matter, and 73% dark energy.Spergel and Kamionkowski then pointed towards the future, predicting even more spectacular results to come over the next decade or so. Our current model of the universe predicts gravitational waves, which we havent observed so far, but the search is heating up. Kamionkowski called this potentially the most important new physics result of this century! He also explained that we can now do neutrino physics using the cosmic microwave background, which already provides the strongest constraint on the sum of neutrinon masses. In the next decade, we should be able to further determine the neutrino mass hierarchy. The coming years in cosmology could be even more exciting than the past twenty!HEAD Rossi Prize talk: A New View of the High Energy Universe with NuSTAR (by Susanna Kohler)This years Rossi Prize winner Fiona Harrison capped off the main part of the day with a plenary talk about some of the highlights from the first two years of the NuSTAR mission, NASAs space-based, high-energy X-ray telescope.Additional science results from the past two years with NuSTAR.Harrison began by telling us about NuSTARs launch in 2012, in which a Pegasus rocket with NuSTAR as its payload was launched from a L-1011 Stargazer aircraft. She claims to have been unconcerned about this part: The payload would go up or it would go down, there wasnt anything I could do about it. The real terror for the NuSTAR team came 9 days later when the telescope slowly unfolded itself over the span of 24 minutes, snapping components into place. All went well, however, and NuSTAR has since been forging exciting new territory in the high-energy X-ray regime!Harrison discussed science highlights from the last two years of NuSTAR, like the discovery of a population of dead stars in the inner parsecs of the galaxy, the identification of the mechanism that most likely re-energizes stalled shocks in supernovae and launches the explosion (in case youre keeping track, its because the star sloshes around. Seriously.), or the evidence that supernova 1987A exploded asymmetrically.NuSTAR is funded through the end of 2016 and is now in its extended mission, so we can expect to see more exciting science coming from it in the future!

  6. AAS 227: Day 1

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    Editors Note:This week were at the 227th AAS Meeting in Kissimmee, FL. Along with several fellow authors from astrobites.com, I will bewritingupdates on selectedevents at themeeting and posting at the end of each day. Follow along here or at astrobites.com, or catch ourlive-tweeted updates from the @astrobites Twitter account. The usual posting schedule for AAS Nova will resumenext week.Things kicked off last night at our undergraduate reception booth. Thanks to all of you who stopped by we were delightedto have so many people tell us that they already know about and useastrobites, and we were excited to introduce a new cohort of students at AAS to astrobites for the first time.Tuesday morning was the official start of the meeting. Here are just a few of the talks and workshops astrobiters attended today.Opening Address (by Becky Smethurst)The President of the AAS, aka our fearless leader Meg Urry kicked off the meeting this morning at the purely coffee powered hour of 8am this morning. She spoke about the importance of young astronomers at the meeting (heres looking at you reader!) and also the importance of the new Working Group for Accessibility and Disabilities (aka WGAD pronounced like wicked) at the AAS. The Society has made extra effort this year to make the conference accessible to all,a message which was very well received by everyone in attendance.Kavli Lecture: New Horizons Alan Stern (by Becky Smethurst)We were definitely spoilt with the first Plenary lecture at this years conference Alan Stern gave us a a review of the New Horizons mission of the Pluto Fly By (astrobites covered the mission back in July with this post). We were treated to beautiful images, wonderful results and a foray into geology.Before (Hubble) and after #NewHorizons. #thatisall #science #astro alanstern #aas227 pic.twitter.com/kkMt6RsSIR Science News (@topsciencething) January 5, 2016Some awesome facts from the lecture that blew my mind:New Horizons is now 2AU (!) beyond PlutoThe mission was featured on the front pages of 450 newspapers worldwide on every single continent (including Antartica!)New Horizons reached the Moon in9 HOURSafter launch (compared to the ~3 days it took the Apollo missions)The mission controllers were aiming for a 100km window of space all the way from EarthThere was a window of ~400seconds which the probe had to arrive within the probe arrived90 seconds early! Putting tardy astronomers everywhere to shame.Charon was the only satellite of Pluto known at the time of the mission proposalThe canyon found on Charon is not only bigger than the Grand Canyon but bigger than Mariner Valley on Mars which is already4000 km (2500 mi) long and reaches depths of up to 7 km (4 mi)!Charons surface. Tectonic feature runs about 1500 km, around 10 km deep. Eat it, Mars. #aas227 pic.twitter.com/blewwJaXEn Danny Barringer (@HeavyFe_H) January 5, 2016The mountains ringing the Sputnik Planum (aka the heart of Pluto) are over 4km high and are snow capped with methane icePlutos mountain ranges. Means surface nitrogen layer is thin, probably water ice according to @AlanStern. #aas227 pic.twitter.com/0yyHZvpBOE Danny Barringer (@HeavyFe_H) January 5, 2016Plutos atmosphere has a dozendistincthaze layers but how they arecreated is a mystery#aas227 hazes on Pluto wow pic.twitter.com/VPx99ZhPj1 Lisa StorrieLombardi (@lisajsl) January 5, 2016Alan also spoke about the future of New Horizons there is a new mission proposal for a fly by of a Kuiper Belt object 2014MU69 in Jan 2019 which should give us a better understanding of this icy frontier at the edge ofthe Solar System. As a parting gift Alan playedthemost gorgeously detailed fly over video of Plutos surface that had all in the room melting into their flip flops. Its safe to say that the whole room is now Pluto-curious and wondering whether a change of discipline is in order!Press Conference: Black Holes and Exoplanets (by Susanna Kohler)This morning marked the first press conference of the meeting, covering some hot topics in black holes and exoplanets.Hubble (background) and Chandra (purple) image of SDSS J1126+2944. The arrow marks the second black hole. (From http://casa.colorado.edu/~comerford/press)The first speaker was Julie Comerford (University of Colorado Boulder), who told us about SDSS J1126+2944, a galaxy that was shown by Chandra X-ray detections to contain not just one, but two supermassive black holes. This is a sign of a recent merger between two galaxies, which can result in one new, larger galaxy with two nuclei for a while. The second black hole is surrounded by only a small sphere of stars. This may be because the rest have been stripped away in the process of the merger but its also possible that the second black hole is an elusive intermediate mass black hole of only 100-1,000,000 solar masses! Heres the press release.The second speaker was Eric Schlegel (University of Texas, San Antonio), who spoke about the galaxy NGC 5195. Eric discussed an interesting problem: we know that star formation ends in galaxies after a time, but the gas must be cleared out of the galaxy for the star formation to halt. What process does this? Schlegels collaboration found evidence in NGC 5195 for a burping supermassive black hole the shock from the black holes outflow sweeps up the hydrogen gas and blows it out of the galactic center. Heres the press release.NuSTAR image of Andromeda, inset on a UV image by NASAs Galaxy Evolution Explorer. Click for a better look! [NASA/JPL-Caltech/GSFC]Next up was Daniel Wik (NASA/Goddard SFC), who discussed recent high-energy X-ray observations of Andromeda galaxy with NASAs NuSTAR. As Wik described it, NuSTAR is like a CSI detective, working to identify what fraction of the compact remnants in X-ray binaries of Andromeda are neutron stars, and what fraction are black holes. Since X-ray binaries play a crucial role in heating gas in protogalaxies, shaping galaxy formation, its important that we learn more about this population and how it evolves over time. Heres the press release.The final speaker was grad studentSamuel Grunblatt (University of Hawaii Institute for Astronomy), who spoke about measuring the mass of exoplanets around active stars. In radial velocity studies of exoplanets, a planet orbiting its star causes the star to wobble. This signal for an Earth-like planet is as tiny as 9 cm/s! Unfortunately, activity of the star can cause radial velocity noise of 1-10 m/s so to detect Earth-like planets, we need to find a way of subtracting off the noise. Grunblatt talked about an intriguing new method for determining planet masses that controls for the signature of their hosts activity. Heres his paper.Annie Jump Cannon Award Lecture: On the Dynamics of Planets, Stars and Black Holes (by Erika Nesvold)This year, the Annie Jump Cannon Award was given to Smadar Naoz, an assistant professor at UCLA. The Cannon Award is given every year to a young (less than 5 years since PhD), female astronomer for outstanding work in her field. Traditionally, the Cannon Award recipient delivers a lecture on her research, so this year we were lucky to see a dynamic and engaging talk by Smadar Naoz about her research in dynamical theory.You may have heard the common career advice that you should focus on becoming the expert on one particular facet of astronomy: a particular type of object, an observational technique, a type of instrument, etc. Naoz has managed to follow that advice while still managing to study a huge range of astronomical topics, from exoplanets to cosmology. She studies hierarchical triples, systems of three gravitational bodies in which two of the bodies orbit one another very closely, while the third orbits the other two from a much greater distance. For example, a planet in a tight orbit around a star, with a brown dwarf orbiting hundreds of AU away, make up a hierarchical triple system. So does a system in which two black holes orbit each other closely, with a third black hole orbiting farther away. The physics of these systems are all the same, so by studying the equations that govern a hierarchical triple system, Naoz can study a huge variety of astronomical objects.In particular, Naoz studies a mechanism called the Kozai-Lidov mechanism, named after the two researchers who discovered it independently. If the outer body in a hierarchical triple orbits at a high enough inclination to the inner body ( 40 degrees), the Kozai-Lidov mechanism will excite the inclination and eccentricity of the inner body. In fact, the inclination and eccentricity will oscillate opposite one another: as the inclination increases, the eccentricity will decrease, and vice versa. In the course of her research, Naoz discovered a flaw in Kozais original derivations of this mechanism, and derived a more accurate, general set of equations describing the Kozai-Lidov mechanism. These new equations indicate that the eccentricity of the inner object can become extremely high, and that the inclination can become so high that the objects orbit can flip from prograde to retrograde! In other words, the object can start orbiting in the opposite direction around the central body.Wondering how Naoz found the error in Kozai? I happen to know she rederives all the equations in every paper she reads. Wow. #aas227 Erika Nesvold (@erikanesvold) January 5, 2016This work has applications in many different types of systems. For example, over the past decade, observers have discovered a large number of retrograde hot Jupiters, gas giant planets orbiting very close to their star, in the opposite direction from the stars spin. Naoz showed that the new, correct Kozai-Lidov mechanism can explain the orbits of these exoplanets, because it increases the planets eccentricity until its orbit approaches very close to the star, and it flips the inclination into a retrograde orbit. Naoz: A puzzle: how to explain retrograde planets? Kozai mechanism can do that! #aas227 Peter Edmonds (@PeterDEdmonds) January 5, 2016Naoz also showed applications of the Kozai-Lidov mechanisms to dark matter halos around black holes, triple black hole systems, and so-called blue stragglers: main-sequence stars in clusters that are brighter and bluer than they should be. Her body of work is an excellent example of how theorists can adapt general physics theories to a wonderful variety of astronomical problems.holy styrofoam planets batman naoz just explained everything. #aas227 August Muench (@augustmuench) January 5, 2016Harassment in the Astronomical Sciences Town Hall(by Caroline Morley)The Town Hall on Harassment in the Astronomical Sciences involved a sobering panel discussion on the current state on workplace climate in astronomy and the current steps that the AAS and federal agencies are taking to improve it. Christina Richey kicked it off by presenting preliminary results from the CSWA Survey on workplace climate. This survey involved 426 participants, and reveals that many people, especially junior members of the field, experience harassment including both verbal and physical harassment. These results will be published this year. Next up, Dara Norman, a Councilor of the AAS and a member of the AAS Ethics Task Force, spoke about the proposed changes to the current AAS Ethics Statement. These changes will focus on corrective policies to improve the state of the field; they will solicit community feedback this Spring and vote on the changes at the Summer AAS meeting. Last, Jim Ulvestad, representing the federal agencies including NSF, NASA, and the DOE, spoke about the current policies for reporting to federal funding agencies. He reminds us that if an institution accepts money from the federal government, they are required by law to follow laws such as Title VI (covering racial harassment) and Title IX (covering sexual harassment), and that breaches can be reported to the funding agency.Tools and Tips for Better Software (aka Pain Reduction for Code Authors)(by Caroline Morley)This afternoon breakout session included a drinking-from-the-firehose set of short talks that covered everything from source-code management and software testing to building communities that create sustainable code. First, Kenza Arraki discussed software such as Git to do version control to keep track of code changes. (Version Control is my (science) New Years Resolution, so I was happy to learn that there is aCodeAcademy tutorial for Git!). Next up, AdrianPrice-Whelan described the merits of software testing and suggests that we actually do Test-driven development where we write tests for the code first, then write code, run tests and debug until tests all pass. Erik Tollerud spoke on Why Document code and how you might convince yourself to do so (documenting code is another good science New Years Resolution!) The most important rule is to always document as you code because you wont ever go back! Bruce Berriman described the best practices for code release, including, importantly, licensing it and describing it well (with tutorials, examples). Matthew Turk reminded us the importance of building community around code development. Robert Nemiroff ended the talks with a discussion of what to do withdeadcodes. The lowest bar? Put it in your Dropbox and share it with your collaborators and students!For more info on all of these topics and more, consider attending a Software Carpentry workshop.

  7. Mid-latitude Geomagnetic Field Analysis Using BOH Magnetometer: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Hwang, Jun-Ga; Choi, Kyu-Cheol; Lee, Jae-Jin; Park, Young-Deuk; Ha, Dong-Hun

    2011-09-01

    Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Mt. Bohyun Observatory to measure the Earth's magnetic field variations in South Korea. We, in 2007, installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we provide the preliminary and the first statistical analysis using the BOH magnetometer installed at Mt. Bohyun Observatory. By superposed analysis, we find that daily variations of H, D, and Z shows similar tendency, that is, about 30 minutes before the meridian (11:28) a minimum appears and the time after about 3 hours and 30 minutes (15:28) a maximum appears. Also, a quiet interval start time (19:06) is near the sunset time, and a quiet interval end time (06:40) is near the sunrise time. From the sunset to the sunrise, the value of H has a nearly constant interval, that is, the sun affects the changes in H values. Seasonal variations show similar dependences to the sun. Local time variations show that noon region has the biggest variations and midnight region has the smallest variations. We compare the correlations between geomagnetic variations and activity indices as we expect the geomagnetic variation would contain the effects of geomagnetic activity variations. As a result, the correlation coefficient between H and Dst is the highest (r = 0.947), and other AL, AE, AU index and showed a high correlation. Therefore, the effects of geomagnetic storms and geomagnetic substorms might contribute to the geomagnetic changes significantly.

  8. Quantitative increases in temporal lobe symptoms in human males are proportional to postnatal geomagnetic activity: verification by canonical correlation.

    PubMed

    Hodge, K A; Persinger, M A

    1991-04-29

    Enhanced geomagnetic activity during episodes of biochemical stress has been correlated with inferences of increased liability within deep temporal lobe structures. Because adult limbic epilepsy is frequently associated with perinatal hypoxia or metabolic disruption within this region, a weak positive correlation was expected between possible signs of mesiobasal temporal lobe lability in normal adults and perinatal geomagnetic activity. Canonical correlation demonstrated that young adult males (n = 243) displayed a positive (r = 0.31) relationship between the intensity of geomagnetic disturbance the day after birth only and a history of subjective depersonalization, anomalous visual and olfactory experiences. The effects was very clear when aa values exceeded 30 nT (gamma). Temporal lobe signs for these males were similar to those reported by normal young adult females (n = 313) who did not display any consistent correlation between these measures and perinatal geomagnetic disturbance. The results suggest that interactions between perinatal neurochemistry and the correlates of geomagnetic activity might permanently alter portions of the male limbic system. PMID:1881599

  9. Geomagnetic activity and local modulations of cosmic rays circa 1 GV

    NASA Technical Reports Server (NTRS)

    Ely, J. T. A.; Huang, T. C.

    1987-01-01

    Solar-sector synchronous modulations of the particulate cosmic radiation reaching the earth's atmosphere have been studied using low altitude satellite and surface data. The flux in the broad maximum of the galactic cosmic ray differential spectrum (near GV rigidity) exhibits an intermittent north-south asymmetry (NSA) in mid and high geomagnetic latitudes. During the 1964 and 1965 years of sunspot minimum, this modulation had a negative rigidity dependence and strong correlations with geomagnetic disturbance index (ap) and interplanetary magnetic field direction. Taken together with other features, this ap dependence is consistent with the hypothesis that reconnection of the interplanetary and geomagnetic fields should produce a local NSA independent of much larger scale NSAs associated with cosmic ray gradients in the heliosphere. This finding is also consistent with suggestions that solar activity influence on atmospheric processes may be mediated by the resulting modulations of upper tropospheric ionization.

  10. foF2 correlation studies with solar and geomagnetic indices for two equatorial stations

    NASA Astrophysics Data System (ADS)

    Joshua, E. O.; Nzekwe, N. M.

    2012-05-01

    The analysis of the contributions of solar and geomagnetic indices on the critical frequency of the ionospheric F2 layer (foF2)-, for different seasons and two Nigerian equatorial stations- Ibadan (Lat. 7.4N, Long. 3.9N) and Ilorin (Lat. 8.5N, Long. 4.55E)- are presented. The data set was randomly sampled across three solar cycles of periods of low, moderate and high solar activities. Solar indices used in this work are Coviten solar flux (F10.7 cm), daily solar radio flux (dF10.7), International Sunspot Number (ISSN), Smoothen Sunspot Number (SmSSN), and Sun Spot Number (SSN). The geomagnetic indices used are planetary indices Am, Aa, Ap, C9, Cp, and Kp. foF2 showed a non-linear trend with an average coefficient (R) of 0.70 across the various seasons. Regression lines for polynomials of degree n=1 to n=6 was fitted, for each data set. Am, Ap, Aa, SSN, ISSN, F10.7 cm, and dF10.7 with R values of 0.71,0.74,0.61,0.59,0.72,0.80, and 0.86, for the various geomagnetic and solar indices, had the highest contributions. We therefore advocate for SSN, ISSN, F10.7 cm, dF10.7 and Am, Ap or Aa in modeling foF2 for the African equatorial ionosphere. The results of this work are in line with the results of other works carried out at different equatorial stations.

  11. AAS Publishing News: Astronomical Software Citation Workshop

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-07-01

    Do you write code for your research? Use astronomical software? Do you wish there were a better way of citing, sharing, archiving, or discovering software for astronomy research? You're not alone! In April 2015, AAS's publishing team joined other leaders in the astronomical software community in a meeting funded by the Sloan Foundation, with the purpose of discussing these issues and potential solutions. In attendance were representatives from academic astronomy, publishing, libraries, for-profit software sharing platforms, telescope facilities, and grantmaking institutions. The goal of the group was to establish “protocols, policies, and platforms for astronomical software citation, sharing, and archiving,” in the hopes of encouraging a set of normalized standards across the field. The AAS is now collaborating with leaders at GitHub to write grant proposals for a project to develop strategies for software discoverability and citation, in astronomy and beyond. If this topic interests you, you can find more details in this document released by the group after the meeting: http://astronomy-software-index.github.io/2015-workshop/ The group hopes to move this project forward with input and support from the broader community. Please share the above document, discuss it on social media using the hashtag #astroware (so that your conversations can be found!), or send private comments to julie.steffen@aas.org.

  12. On the watch for geomagnetic storms

    USGS Publications Warehouse

    Green, Arthur W.; Brown, William M., III

    1997-01-01

    Geomagnetic storms, induced by solar activity, pose significant hazards to satellites, electrical power distribution systems, radio communications, navigation, and geophysical surveys. Strong storms can expose astronauts and crews of high-flying aircraft to dangerous levels of radiation. Economic losses from recent geomagnetic storms have run into hundreds of millions of dollars. With the U.S. Geological Survey (USGS) as the lead agency, an international network of geomagnetic observatories monitors the onset of solar-induced storms and gives warnings that help diminish losses to military and commercial operations and facilities.

  13. Strategic Change in AAS Publishing

    NASA Astrophysics Data System (ADS)

    Steffen, Julie

    2015-08-01

    The American Astronomical Society has embarked on a process of strategic change in its publishing program. The process has incuded authors, AAS leaders, editors, publishing experts, librarians, and data scientists. This session will outline the still ongoing process and present some both upcoming and already available new AAS Publishing features and services to the global astronomy community.

  14. Geomagnetic storms, super-storms, and their impacts on GPS-based navigation systems

    NASA Astrophysics Data System (ADS)

    Astafyeva, E.; Yasyukevich, Yu.; Maksikov, A.; Zhivetiev, I.

    2014-07-01

    Using data of GPS receivers located worldwide, we analyze the quality of GPS performance during four geomagnetic storms of different intensity: two super-storms and two intense storms. We show that during super-storms the density of GPS Losses-of-Lock (LoL) increases up to 0.25% at L1 frequency and up to 3% at L2 frequency, and up to 0.15% (at L1) and 1% (at L2) during less intense storms. Also, depending on the intensity of the storm time ionospheric disturbances, the total number of total electron content (TEC) slips can exceed from 4 to 40 times the quiet time level. Both GPS LoL and TEC slips occur during abrupt changes of SYM-H index of geomagnetic activity, i.e., during the main phase of geomagnetic storms and during development of ionospheric storms. The main contribution in the total number of GPS LoL was found to be done by GPS sites located at low and high latitudes, whereas the area of numerous TEC slips seemed to mostly correspond to the boundary of the auroral oval, i.e., region with intensive ionospheric irregularities. Our global maps of TEC slips show where the regions with intense irregularities of electron density occur during geomagnetic storms and will let us in future predict appearance of GPS errors for geomagnetically disturbed conditions.

  15. Magnetic clouds, geomagnetic disturbances, and cosmic ray decreases

    NASA Technical Reports Server (NTRS)

    Zhang, G.; Burlaga, L. F.

    1988-01-01

    Nineteen magnetic clouds are identified in the years from 1978 through 1982 and studied using superposed epoch analysis. The magnetic-field intensity, proton density and proton temperature are enhanced ahead of magnetic clouds that are preceded by shock, while strong magnetic-field intensity and low proton temperature are observed within the clouds. A relatively large (about 2.5 percent) decrease in cosmic-ray intensity is associated with magnetic clouds that are preceded by a shock, perhaps caused by the turbulent sheath behind an interplanetary shock ahead of the magnetic cloud, whereas only a small (0.5 percent) decrease in intensity is associated with the magnetic cloud itself. Magnetic clouds can produce geomagnetic activity with a decrease in Dst index of the order 100 gamma. The magnitude of the change in the Dst index for the case when southward fields arrive first is comparable to that for the case when northward fields arrive first, and the phase is such that geomagnetic activity is associated with southward fields.

  16. Frequency of Proterozoic geomagnetic superchrons

    NASA Astrophysics Data System (ADS)

    Driscoll, Peter E.; Evans, David A. D.

    2016-03-01

    Long-term geodynamo evolution is expected to respond to inner core growth and changing patterns of mantle convection. Three geomagnetic superchrons, during which Earth's magnetic field maintained a near-constant polarity state through tens of Myr, are known from the bio/magnetostratigraphic record of Phanerozoic time, perhaps timed according to supercontinental episodicity. Some geodynamo simulations incorporating a much smaller inner core, as would have characterized Proterozoic time, produce field reversals at a much lower rate. Here we compile polarity ratios of site means within a quality-filtered global Proterozoic paleomagnetic database, according to recent plate kinematic models. Various smoothing parameters, optimized to successfully identify the known Phanerozoic superchrons, indicate 3-10 possible Proterozoic superchrons during the 1300 Myr interval studied. Proterozoic geodynamo evolution thus appears to indicate a relatively narrow range of reversal behavior through the last two billion years, implying either remarkable stability of core dynamics over this time or insensitivity of reversal rate to core evolution.

  17. Intense geomagnetic storms: A study

    NASA Astrophysics Data System (ADS)

    Silbergleit, Virginia

    In the pipes and the lines of the transmission of the electrical energy, the route of the currents through them, causes a diminution of the life utility of the same one. The intense storms are studied, because these are induced quickly to the ionospheric systems that they change, obtaining great induced telluric currents (or GICs). Also the Akasofs parameter based on the time for periods of strong and moderate magnetic storms during the last 10 years is calculated. The method also standardizes the parameters of the storm: electron flow between 30-300 KeV, z component of the magnetic field (Bz), the solar Wind velocity (v), indices AE and AL. Also, the decay time of the ring current (which is different during the main and the recovery phase from of the geomagnetic disturbances) are calculated.

  18. Major geomagnetic storms and cosmic rays, 1. search of features in CR what can be used for forecasting

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Mavromichalaki, H.; Pustilnik, L. A.; Sternlieb, A.; Zukerman, I. G.

    2001-08-01

    According to NOAA Space Weather Scales, geomagnetic storms of scales G5 (3-hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) are dangerous for people technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others. To prevent these serious damages will be very important to forecast dangerous geomagnetic storms. In many papers it was shown that in principle for this forecasting can be used data on CR intensity and CR anisotropy changing before SC of major geomagnetic storms accompanied by sufficient Forbush-decreases (e.g., Dorman et al., 1995, 1999). In this paper we consider over 100 major geomagnetic storms and for each case we analyze hourly data of many NM for 8 days with SC in the 4-st day of 8-days period (that before SC we have at least 3 full days). We determine what part of major geomagnetic storms is accompanied CR intensity and CR anisotropy changing before SC, and what part of major geomagnetic storms does not show any features what can be used for forecasting. We estimate also how these parts depend from the index of geomagnetic activity Kp. REFERNECES Yudakhin K.F., Bavassano B., Ptitsyna N.G., Tyasto M.I., "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, Vol. 49A, pp. 136-144. (1995). L.I.Dorman, N.Iucci, N.G.Ptitsyna, G.Villoresi, Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their prediction , Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, Vol. 6, p. 476-479, (1999).

  19. AAS 227: Day 3

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    Editors Note:This week were at the 227th AAS Meeting in Kissimmee, FL. Along with several fellow authors from astrobites.com, I will bewritingupdates on selectedevents at themeeting and posting at the end of each day. Follow along here or atastrobites.com, or catch ourlive-tweeted updates from the@astrobites Twitter account. The usual posting schedule for AAS Nova will resumenext week.Welcome to Day 3 of the winter American Astronomical Society (AAS) meeting in Kissimmee! Several of us are attending the conference this year, and we will report highlights from each day here on astrobites. If youd like to see more timely updates during the day, we encourage you to follow @astrobites on twitter or search the #aas227 hashtag.Henry Norris Russell Lecture: Viewing the Universe with Infrared Eyes: The Spitzer Space Telescope (by Erika Nesvold)The Henry Norris Russell Award is the highest honor given by the AAS, for a lifetime of eminence in astronomy research. This years award went to Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics. Fazio became a leader in gamma ray astronomy before switching mid-career to the study of infrared astronomy, and he gave his award lecture on the latter subject, specifically on the Spitzer Space Telescope, one of the most successful infrared telescopes of all time.Artists rendering of the Spitzer space telescope. [NASA/JPL-Caltech]Spitzer has been operating for more than twelve years, and has resulted in over six thousand papers in refereed journals in that time. The telescope sits in an Earth-trailing orbit around the Sun, and is now farther from the Earth (1.4 AU) than the Earth is from the Sun. Fazio gave the audience a fascinating overview of the science done by Spitzer over more than a decade. One of the most productive areas of research for Spitzer is the study of exoplanets, which hadnt even been discovered when the Spitzer Telescope was first conceived. Spitzers high sensitivity and ability to observe exoplanets over many orbits has made it a powerhouse for learning about the temperatures, atmospheres, and orbits of exoplanets. The list of examples that Fazio provided included the first global temperature map of an exoplanet (HD 189733b), the detection of the closest transiting exoplanet (HD 219134b), and the measurement of thermal emission from a super-Earth (55 Cnc e). Spitzers large distance from the Earth (specifically, the ground-based telescopes on Earth) even allowed astronomers to observe an exoplanet via gravitational microlensing using a special technique called space-based parallax.Spitzer has also been extremely useful for observing everything from Solar System scales (such as the enormous infrared dust ring around Saturn) to galactic structures. Comparing images of galaxies observed at visible wavelengths with Spitzer images of the same galaxies at infrared wavelengths has allowed us to probe the structure and composition of galaxies at a new level.Astronomers have also used Spitzer to explore the evolution of stars. Thanks to its infrared detectors, Spitzer can look through large clouds of dust that are opaque at visible wavelengths, and observe young stellar objects in their birth environments. Cosmologists can use Spitzer to study the early universe and the formation of galaxies over twelve billion years ago. Fazio used all of these examples and more to demonstrate that Spitzer has truly changed our understanding of the universe.Climate Change for Astronomers (Meredith Rawls)Every astronomer at #aas227 wants to learn about climate change! WOW this room is ridiculously full. pic.twitter.com/ud9an0gLJG Meredith Rawls (@merrdiff) January 7, 2016The second half of the session was a presentation by Doug Duncan featuring an activity from his 101-level college course. He uses climate change as a way to teach critical thinking and scientific reasoning. Members of the audience were walked through an exercise that included interpreting plots of changing surface temperatures, think-pair-share style clicker questions, and comparing excerpts from scientific articles and the media. Eventually, students discover that the Earths overall temperature is going up, but observations can vary from year to year because heat is moving between the atmosphere and the oceans.Press Conference: Fermis Vision, First Stars, Massive Galaxy Cluster, and Dark Energy (by Susanna Kohler)Todays afternoon press conference was an exciting assortment of results, difficult to categorize under a single umbrella.First up was Marco Ajello (Clemson University), who spoke about 2FHL, the second Fermi-LAT catalog of high-energy sources. LAT stands for Large Area Telescope, an instrument on board the Fermi gamma-ray space observatory that scans the entire sky every three hours. Ajello described the contents of the 2FHL catalog: 360 gamma-ray sources, of which 75% are blazars (distant galactic nuclei with jets pointed toward us), 11% are sources within the galaxy, and the remaining 14% are unknown. With this catalog, Fermi has expanded into higher energies than ever before, providing the first map of the 50 GeV 2 TeV sky. Heres the press release.OMeara: Im a lowly spectroscopist so I dont have fun pictures to show you, just squiggly lines. #aas227 astrobites (@astrobites) January 7, 2016Next to speak, John OMeara (St. Michaels College) told us about the discovery of a gas cloud that may be a remnant from the first population of stars. OMeara showed us the emission spectrum from a distant quasar, which displays abrupt absorption by a cloud of gas located at a redshift of z~3.5. Absorption by gas clouds is not unusual but what is unusual is that this cloud is extremely metal-poor, with only 1/2500th solar metallicity. This is the lowest heavy-element content ever measured, and a sign that the cloud might have been enriched by Population III stars the theoretical first population of stars, which were born when gas in the universe was still pristine. Heres the press release.Cluster IDCS J1426.5+3508. [NASA, European Space Agency, University of Florida, University of Missouri, and University of California]Mark Brodwin (University of Missouri, Kansas City) was up next, discussing the most distant massive galaxy cluster that has ever been discovered. The cluster IDCS J1426.5+3508, weighing in at several trillion solar masses (as measured by three independent techniques!), is located at a redshift of z=1.75. Since clusters take several billion years to form, and its redshift corresponds to a time when the universe was only 3.8 billion years old, were probably seeing it at a very early age. This combination of mass and youth is unique! Brodwin also pointed out another interesting feature: the clusters core isnt centered, which means it probably underwent a major merger with another cluster within the last 500 million years. Heres the press release.The final speaker was Sukanya Chakrabarti (Rochester Institute of Technology), who gave a very interesting talk about a topic Id never heard of: galactoseismology. Galactoseismology involves observing waves in the disk of a galaxy to learn about the properties of dwarf galaxies that caused the perturbations. In this case, Chakrabarti evaluated ripples in the outer disk of our galaxy, and used these to predict the location of a dwarf galaxy that must have skimmed the outskirts of our galaxy a few hundred million years ago, causing the waves. This is a cool technique for learning about dwarf galaxies whether or not theyre visible, since theyll cause ripples even if theyre dominated by dark matter. Chakrabarti showed an awesome simulation of this dwarfs interaction with the Milky Way, which you can check out on her website. Heres the press release.

  20. A new way to study geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Hutchinson, J. A.; Wright, D. M.; Milan, S. E.; Grocott, A.; Boakes, P. D.

    2011-08-01

    James Hutchinson and colleagues describe a novel radar technique to study geomagnetic storms: superposed latitude-time-velocity plots. This is a summary of the poster winning a Rishbeth Prize at the NAM/UKSP/MIST meeting in April.

  1. How the geomagnetic field vector reverses polarity

    USGS Publications Warehouse

    Prevot, M.; Mankinen, E.A.; Gromme, C.S.; Coe, R.S.

    1985-01-01

    A highly detailed record of both the direction and intensity of the Earth's magnetic field as it reverses has been obtained from a Miocene volcanic sequence. The transitional field is low in intensity and is typically non-axisymmetric. Geomagnetic impulses corresponding to astonishingly high rates of change of the field sometimes occur, suggesting that liquid velocity within the Earth's core increases during geomagnetic reversals. ?? 1985 Nature Publishing Group.

  2. Geomagnetic main field modeling using magnetohydrodynamic constraints

    NASA Technical Reports Server (NTRS)

    Estes, R. H.

    1985-01-01

    The influence of physical constraints are investigated which may be approximately satisfied by the Earth's liquid core on models of the geomagnetic main field and its secular variation. A previous report describes the methodology used to incorporate nonlinear equations of constraint into the main field model. The application of that methodology to the GSFC 12/83 field model to test the frozen-flux hypothesis and the usefulness of incorporating magnetohydrodynamic constraints for obtaining improved geomagnetic field models is described.

  3. Geomagnetic disturbance effects on power systems

    SciTech Connect

    Albertson, V.D.; Bozoki, B.; Feero, W.E.; Kappenman, J.G.; Larsen, E.V.; Nordell, D.E.; Ponder, J.; Prabhakara, F.S.; Thompson, K.; Walling, R.

    1993-07-01

    In the northern hemisphere, the aurora borealis is visual evidence of simultaneous fluctuations in the earth's magnetic field (geomagnetic field). These geomagnetic disturbances (GMD's), or geomagnetic storms, can affect a number of man-made systems, including electric power systems. The GMD's are caused by the electromagnetic interaction of the solar wind plasma of protons and electrons with the geomagnetic field. These dynamic impulses in the solar wind are due to solar flares, coronal holes, and disappearing filaments, and reach the earth from one to six days after being emitted by a solar event. Instances of geomagnetic storms affecting telegraph systems were noted in England in 1846, and power system disturbances linked to GMD's were first reported in the United States in 1940. This Working Group report is a summary of the state of knowledge and research activity to the present time, and covers the GMD/Geomagnetically-induced currents (GIC) phenomena, transformer effects, the impact on generators, protective relay effects, and communication system effects. It also summarizes modeling and predicting GIC, measuring and monitoring GIC, mitigation methods, system operating guidelines during GMD's, and alerting and forecasting procedures and needs for the power industry.

  4. Spectral characteristics of geomagnetic field variations at low and equatorial latitudes

    USGS Publications Warehouse

    Campbell, W.H.

    1977-01-01

    Geomagnetic field spectra from eight standard observations at geomagnetic latitudes below 30?? were studied to determine the field characteristics unique to the equatorial region. Emphasis was placed upon those variations having periods between 5 min and 4 hr for a selection of magnetically quiet, average, and active days in 1965. The power spectral density at the equator was about ten times that the near 30?? latitude. The initial manifestation of the equatorial electrojet as evidenced by the east-west alignment of the horizontal field or the change in vertical amplitudes occurred below about 20?? latitude. Induced current effects upon the vertical component from which the Earth conductivity might be inferred could best be obtained at times and latitudes unaffected by the electrojet current. Values of about 1.6 ?? 103 mhos/m for an effective skin depth of 500-600 km were determined. The spectral amplitudes increased linearly with geomagnetic activity index, Ap. The spectral slope had a similar behavior at all latitudes. The slope changed systematically with Ap-index and showed a diurnal variation, centered on local noon, that changed form with geomagnetic activity.

  5. Synchronization of heart rate indices of human and Pc5 pulsations in the geomagnetic quiet conditions

    NASA Astrophysics Data System (ADS)

    Zenchenko, Tatiana

    Geomagnetic pulsations with duration of the period over 150 seconds (Pc5-6) are present in the magnetosphere almost constantly. Unlike other types of geomagnetic pulsations, they are characterized by high amplitudes reaching in auroral latitudes 30-100 nT, and even 300 - 600 nT in time of significant geomagnetic disturbances [1]. To date, it is generally accepted that the classic morning and afternoon Pc5 pulsations in the magnetosphere are toroidal Alfven resonance vibrations of the geomagnetic field lines [2, 3]. It was revealed that the basic oscillation periods, presented in heart rate variability of healthy subjects, in conditions of rest, at each time point substantially coincide with the periods of oscillation of the X-vector components of the geomagnetic field in the frequency range of Pc5-6 pulsations. Synchronization effect was observed in approximately 60% of cases [4]. The above statement is based on the results of more than 100 experiments (recording time from 60 to 200 min), conducted in the period 2011-2013 in various research groups [4]. In total, 37 volunteers in the age range 18-65 yrs took part in the experiments. Experiments were performed in Pushchino and Khimki (Moscow region), Arkhangelsk, Tomsk, Sofia (Bulgaria), as well as at the station Starorusskaya (Leningrad region). The geomagnetic data were obtained from INTERMAGNET network (http://ottawa.intermagnet.org/Welcom_e.php). From a biophysical point of view, the observed effects of timing fluctuations of heart rate of healthy subjects with the oscillations of the magnetic induction vector of the GMF could be an effective tool for solving one of the most actual problems in heliobiophysics, namely the identification of specific physiological mechanisms of biosystems response to low-intensity variations external factors. 1. Pilipenko V.A., Kleimenova N.G., Kozyreva O.V., Yumoto K., Bitterly G. Geomagnetism and aeronomy, 1997, V. 37, ?.3, P. 64-76 2. Chen L. and Hasegawa A. J.Geophys. Res. 1974. Vol.79,P.1024-1032 3. Southwood D.J. Planet. Space Sci. 1974. Vol.22, P.483-491. 4.Zenchenko T.A., Medvedeva A.A., Khorseva N.I., Breus T.K. // Geophysical Processes and Biosphere. 2013. V. 12. ? 4. P. 73-84

  6. On the seismogenic increase of the ratio of the ULF geomagnetic field components

    NASA Astrophysics Data System (ADS)

    Masci, Fabrizio

    2011-07-01

    Following the paper by Fraser-Smith et al. (1990), many scientists have focused their research on the ULF geomagnetic field pulsations in the hope of finding possible anomalous signals caused by the seismic activity. Thereafter, many papers have reported ULF geomagnetic field polarization ratio increases which have been claimed to be related to the occurrence of moderate and strong earthquakes. Even if there is no firm evidence of correlation between the polarization ratio increase and seismic events, these publications maintain that these "anomalous" increases are without doubt precursors of pending earthquakes. Furthermore, several researchers suggest that these seismogenic signals may be considered a promising approach towards the possibility of developing short-term earthquake prediction capabilities based on electromagnetic precursory signatures. On the contrary, a part of the scientific community emphasizes the lack of validation of claimed seismogenic anomalies and doubt their association with the seismic activity. Since earthquake prediction is a very important topic of social importance, the authenticity of earthquake precursors needs to be carefully checked. The aim of this paper is to investigate the reliability of the ULF magnetic polarization ratio changes as an earthquakes' precursor. Several polarization ratio increases of the geomagnetic field, which previous researchers have claimed to have a seismogenic origin, are put into question by a qualitative investigation. The analysis takes into account both the temporal evolution of the geomagnetic field polarization ratio reported in previous papers, and the global geomagnetic activity behaviour. Running averages of the geomagnetic index Kp are plotted onto the original figures from previous publications. Moreover, further quantitative analyses are also reported. Here, nine cases are investigated which include 17 earthquakes. In seven cases it is shown that the suggested association between the geomagnetic field polarization ratio increases and the earthquake preparation process seems to be rather doubtful. More precisely, the claimed seismogenic polarization ratio increases are actually closely related to decreases in the geomagnetic activity level. Furthermore, the last two investigated cases seem to be doubtful as well, although a close correspondence between polarization ratio and geomagnetic activity cannot be unambiguously demonstrated.

  7. Relationship Between Human Physiological Parameters And Geomagnetic Variations Of Solar Origin

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.

    This study attempts to assess the influence of increased geomagnetic activity on some human physiological parameters. The blood pressure, heart rate and general well-being of 86 volunteers were measured (the latter by means of a standardized questionnaire) on work days in autumn 2001 (01/10 to 09/11) and in spring 2002 (08/04 to 28/05). These periods were chosen because of maximal expected geomagnetic activity. Altogether, 2799 recordings were obtained and analysed. MANOVA was employed to check the significance of the influence of three factors on the physiological parameters under consideration. The three factors were the following: 1) planetary geomagnetic activity level estimated by Ap-index and divided into five levels; 2) gender - males and females; 3) blood pressure degree - persons in the group examined were divided into hypotensive, normotensive and hypertensive. Post hoc analysis was performed to elicit the significance of differences in the factors' levels. The average arterial blood pressure of the group was found to increase significantly with the increase of geomagnetic activity level. The average increment of systolic and diastolic blood pressure reached 9%, which deserves attention from a medical point of view. This effect was present irrespectively of gender. Results obtained suppose that hypertensive persons have the highest sensitivity and the hypotensive persons have the lowest sensitivity of the arterial blood pressure to increase of geomagnetic activity. The results did not show significant changes in the heart rate. The percentage of the persons who reported subjective psycho-physiological complaints was also found to increase significantly with the geomagnetic activity increase. During severe geomagnetic storms 30% of the persons examined reported subjective complaints and the highest sensitivity was revealed for the hypertensive females. The results obtained add further evidence that blood pressure seems to be affected by geomagnetic variations of solar origin. The examinations and analyses performed show that space weather prediction may be utilized for the purpose of pharmacological and regime measures to limit the adverse physiological reactions to geomagnetic storms.

  8. Effect of severe geomagnetic storm conditions on atomic oxygen greenline dayglow emission in mesosphere

    NASA Astrophysics Data System (ADS)

    Bag, T.; Sunil Krishna, M. V.; Gahlot, Shilpa; Singh, Vir

    2014-04-01

    Severe geomagnetic storms and their effects on the 557.7 nm dayglow emission are studied in mesosphere. This study is primarily based on photochemical model with the necessary input obtained from a combination of experimental observations and empirical models. The model results are presented for a low latitude station Tirunelveli (8.7°N, 77.8°E). The volume emission rates are calculated using MSISE-90 and NRLMSISE-00 neutral atmospheric models. A comparison is made between the results obtained from these two models. A positive correlation amongst volume emission rate (VER), O, O2 number densities and Dst index has been found. The present results indicate that the variation in emission rate is more for MSISE-90 than in NRLMSISE-00 model. The maximum depletion in the VER of greenline dayglow emission is found to be about 30% at 96 km during the main phase of the one of the geomagnetic storms investigated in the case of MSISE-90 (which is strongest with Dst index -216 nT). The O2 density decreases about 22% at 96 km during the main phase of the same geomagnetic storm.The NRLSMSISE-00 model does not show any appreciable change in the number density of O during any of the two events. The present study also shows that the altitude of peak emission rate is unaffected by the geomagnetic storms. The effect of geomagnetic storm on the greenline nightglow emission has also been studied. It is found that almost no correlation can be established between the Dst index and variations in the volume emission rates using the NRLMSISE-00 neutral model atmosphere. However, a positive correlation is found in the case of MSISE-90 and the maximum depletion in the case of nightglow is about 40% for one of the storms. The present study shows that there are significant differences between the results obtained using MSISE-90 and NRLMSISE-00.

  9. Magnetic clouds, cosmic ray decreases, and geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Ifedili, S. O.

    2006-05-01

    The relationship between magnetic clouds, cosmic ray decreases and geomagnetic storms has been investigated by using some cosmic ray hourly intensities recorded with ground-based monitors at Alert, Deep River and Mount Washington, as well as the geomagnetic activity Dst index, and the interplanetary magnetic field (IMF) and the solar wind plasma (SWP) bulk-speed, density and temperature in the near-Earth space, on 28-30 September 1978, 24-26 April 1979, 13-15 January 1967, 3-5 January 1978, and 27-29 November 1989. Due to the interplanetary coronal mass ejection (ICME) impacting on slow solar wind, there is a sheath upstream of the ICME led by a fast forward shock. And the large IMF variations in this sheath, which sustain the depressions in the cosmic ray intensity during Forbush decreases (FDs), were found not to influence the main phase storm, but rather the southward IMF in the said sheath and magnetic cloud was the major source in triggering geomagnetic storms, by allowing a strong coupling between the solar wind and the magnetosphere. It was also observed that the initial set of the main phase storm always began in the sheath where, and when, the sustained southward-oriented IMF first occurred, but ceased when the IMF was rotated to a strong northward-orientation, only to resume at subsequent sustained southward-oriented IMF within the sheath and the leading (i.e., front) region of the magnetic cloud. The front boundary of the magnetic cloud was found to be well defined by the relatively high (? 10 nT) rms of the IMF components, which prominently separates both the Lull region of the sheath and the onset of the second decrease of the two-step FD, from the magnetic cloud. There were some instances where a two-step main phase storm, caused by the combination of a sheath and cloud structure, occurred, the two steps sometimes both starting in the sheath itself. Also, in some cases, the sheath and the leading region of the magnetic cloud together produced a single-step storm. In addition, enhanced IMF south latitude and IMF intensity in the sheath and magnetic cloud during the IMF sustained southern orientation, were each observed to produce enhanced geomagnetic activity, even for intense storms. And high SWP bulk speed was found to reduce the depth of the Dst index. Therefore, it appears that when the magnetosphere is exposed to a sustained southward-oriented IMF in the magnetic cloud and the sheath preceding it, a valve (i.e., valve-like IMF direction) opens and allows direct transfer of energy between the solar wind and the magnetosphere to trigger the geomagnetic storms, such that the stronger the sustained IMF south-ward orientation, the wider the valve opens, the higher the SWP bulk speed, the narrower the opening in the valve becomes. And the more the IMF strength during the IMF southern orientation, the larger is the solar wind energy density that is available for transfer through the valve. The valve closes when the IMF is rotated to a strong northward-orientation, and the geomagnetic storms cease.

  10. Long periods (1 -10 mHz) geomagnetic pulsations variation with solar cycle in South Atlantic Magnetic Anomaly

    NASA Astrophysics Data System (ADS)

    Rigon Silva, Willian; Schuch, Nelson Jorge; Guimares Dutra, Severino Luiz; Babulal Trivedi, Nalin; Claudir da Silva, Andirlei; Souza Savian, Fernando; Ronan Coelho Stekel, Tardelli; de Siqueira, Josemar; Espindola Antunes, Cassio

    The occurrence and intensity of the geomagnetic pulsations Pc-5 (2-7 mHz) and its relationship with the solar cycle in the South Atlantic Magnetic Anomaly -SAMA is presented. The study of geomagnetic pulsations is important to help the understanding of the physical processes that occurs in the magnetosphere region and help to predict geomagnetic storms. The fluxgate mag-netometers H, D and Z, three axis geomagnetic field data from the Southern Space Observatory -SSO/CRS/INPE -MCT, So Martinho da Serra (29.42 S, 53.87 W, 480m a.s.l.), RS, Brasil, a were analyzed and correlated with the solar wind parameters (speed, density and temperature) from the ACE and SOHO satellites. A digital filtering to enhance the 2-7 mHz geomagnetic pulsations was used. Five quiet days and five perturbed days in the solar minimum and in the solar maximum were selected for this analysis. The days were chosen based on the IAGA definition and on the Bartels Musical Diagrams (Kp index) for 2001 (solar maximum) and 2008 (solar minimum). The biggest Pc-5 amplitude averages differences between the H-component is 78,35 nT for the perturbed days and 1,60nT for the quiet days during the solar maximum. For perturbed days the average amplitude during the solar minimum is 8,32 nT, confirming a direct solar cycle influence in the geomagnetic pulsations intensity for long periods.

  11. Space weather and dangerous phenomena on the Earth: principles of great geomagnetic storms forcasting by online cosmic ray data

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.

    2005-11-01

    According to NOAA space weather scales, geomagnetic storms of scales G5 (3-h index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) are dangerous for satellites, aircrafts, and even for technology on the ground (influence on power systems, on spacecraft operations, on HF radio-communications and others). We show on the basis of statistical data, that these geomagnetic storms, mostly accompanied by cosmic ray (CR) Forbush-decreases, are also dangerous for people's health on spacecraft and on the ground (increasing the rate of myocardial infarctions, brain strokes and car accident road traumas). To prevent these serious damages it is very important to forecast dangerous geomagnetic storms. Here we consider the principles of using CR measurements for this aim: to forecast at least 10-15h before the sudden commencement of great geomagnetic storms accompanied by Forbush-decreases, by using neutron monitor muon telescope worldwide network online hourly data. We show that for this forecast one may use the following features of CR intensity variations connected with geomagnetic storms accompanied by Forbush-decreases: 1) CR pre-increase, 2) CR pre-decrease, 3) CR fluctuations, 4) change in the 3-D CR anisotropy.

  12. [Chronic inflammation and AA amyloidosis].

    PubMed

    Blank, N; Schönland, S O

    2013-09-01

    Systemic AA amyloidosis is a severe complication of chronic inflammatory diseases. Renal involvement is the predominant organ manifestation. Patients who are at risk for developing AA amyloidosis should be screened for microalbuminuria. The goal of therapy is an effective control of the acute phase reaction. A well controlled blood pressure and nephroprotective treatment contribute to the maintenance of renal function. In case of progressive amyloidosis dialysis is required. Renal transplantation can be performed if the underlying disease is well controlled. PMID:24006165

  13. Geomagnetically trapped anomalous cosmic rays

    SciTech Connect

    Selesnick, R.S.; Cummings, A.C.; Cummings, J.R.

    1995-06-01

    Since its launch in July 1992, the polar-orbiting satellite SAMPEX has been collecting data on geomagnetically trapped heavy ions, predominantly O, N, and Ne, at energies {ge}15 MeV/nucleon and in a narrow L shell range L = 2. Their location, elemental composition, energy spectra, pitch angle distribution, and time variations all support the theory that these particles originated as singly ionized interplanetary anomalous cosmic rays that were stripped of electrons in the Earth`s upper atmosphere and subsequently trapped. The O are observed primarily at pitch angles outside the atmospheric loss cones, consistent with a trapped population, and their distribution there is nearly isotropic. The abundances relative to O of the N, possible Ne, and especially C are lower than the corresponding interplanetary values, which may be indicative of the trapping efficiencies. The distributions of trapped N, O, and Ne in energy and L shell suggest that most of the ions observed at the SAMPEX altitude of {approximately}600 km are not fully stripped when initially trapped. A comparison of the trapped intensity with the much lower interplanetary intensity of anomalous cosmic rays provides model-dependent estimates of the product of the trapping probability and the average trapped particle lifetime against ionization losses in the residual atmosphere for particles that mirror near the SAMPEX altitude. 36 refs., 13 figs., 1 tab.

  14. On Geomagnetism and Paleomagnetism I

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2000-01-01

    A partial description of Earth's broad scale, core-source magnetic field has been developed and tested three ways. The description features an expected, or mean, spatial magnetic power spectrum that is approximately inversely proportional to horizontal wavenumber atop Earth's core. This multipole spectrum describes a magnetic energy range; it is not steep enough for Gubbins' magnetic dissipation range. Temporal variations of core multipole powers about mean values are to be expected and are described statistically, via trial probability distribution functions, instead of deterministically, via trial solution of closed transport equations. The distributions considered here are closed and neither require nor prohibit magnetic isotropy. The description is therefore applicable to, and tested against, both dipole and low degree non-dipole fields. In Part 1, a physical basis for an expectation spectrum is developed and checked. The description is then combined with main field models of twentieth century satellite and surface geomagnetic field measurements to make testable predictions of the radius of Earth's core. The predicted core radius is 0.7% above the 3480 km seismological value. Partial descriptions of other planetary dipole fields are noted.

  15. Geomagnetic substorm association of plasmoids

    SciTech Connect

    Moldwin, M.B.; Hughes, W.J. )

    1993-01-01

    The relationship of geomagnetic substorms and plasmoids is examined by determining the correlation of the 366 plasmoids identified by Moldwin and Hughes (1992) with ground auroral zone magnetograms and geosynchronous particle data signatures of substorm onsets. Over 84% of the plasmoid events occurred between 5 and 60 min after a substorm onset. We also find near one-to-one correlation between large isolated substorm signatures in the near-Earth region and signatures consistent with a passing plasmoid in the distant tail (i.e., a traveling compression region, or an actual plasmoid observation). However, there does not appear to be an absolute correspondence of every substorm onset to a plasmoid signature in the deep tail especially, for periods of prolonged disturbance that have multiple substorm insets. A correlation of inter-planetary magnetic field B. south with plasmoid observations was also found. The locations of the near- and far-Earth reconnection sites are estimated using the time of flight of the plasmoids from substorm onset to their observation at ISEE 3. The estimates of the near- and far-Earth reconnection sites are highly variable and range from 10 to 140 RE, 32 refs., 4 figs. 2 tabs.

  16. Local Geomagnetic Indices and the Prediction of Auroral Power

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Gjerloev, J. W.

    2014-12-01

    As the number of magnetometer stations and data processing power increases, just how auroral power relates to geomagnetic observations becomes a quantitatively more tractable question. This paper compares Polar UVI auroral power observations during 1997 with a variety of geomagnetic indices. Local time (LT) versions of the SuperMAG auroral electojet (SME) are introduced and examined, along with the corresponding upper and lower envelopes (SMU and SML). Also, the East-West component, BE, is investigated. We also consider whether using any of the local indices is actually better at predicting local auroral power than a single global index. Each index is separated into 24 LT indices based on a sliding 3-h MLT window. The ability to predict - or better reconstruct - auroral power varies greatly with LT, peaking at 1900 MLT, where about 75% of the variance (r2) can be predicted at 1-min cadence. The aurora is fairly predictable from 1700 MLT - 0400 MLT, roughly the region in which substorms occur. Auroral power is poorly predicted from auroral electrojet indices from 0500 MLT - 1500 MLT, with the minima at 1000-1300 MLT. In the region of high predictability, the local variable which works best is BE, in contrast to long-standing expectations. However using global SME is better than any local variable. Auroral power is best predicted by combining global SME with a local index: BE from 1500-0200 MLT, and either SMU or SML from 0300-1400 MLT. In the region of the diffuse aurora, it is better to use a 30 min average than the cotemporaneous 1-min SME value, while from 1500-0200 MLT the cotemporaneous 1-min SME works best, suggesting a more direct physical relationship with the auroral circuit. These results suggest a significant role for discrete auroral currents closing locally with Pedersen currents.

  17. Relationship between human physiological parameters and geomagnetic variations of solar origin

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.

    Results presented concern influence of increased geomagnetic activity on some human physiological parameters. The blood pressure and heart rate of 86 volunteers were measured on working days in autumn 2001 (01/10 09/11) and in spring 2002 (08/04 28/05). These periods were chosen because of maximal expected geomagnetic activity. Altogether 2799 recordings were obtained and analysed. Questionnaire information about subjective psycho-physiological complaints was also gathered. MANOVA was employed to check the significance of the influence of three factors on the physiological parameters under consideration. The factors were the following: (1) planetary geomagnetic activity level estimated by Ap-index and divided into five levels; (2) gender males and females; (3) blood pressure degree persons in the group examined were divided into hypotensive, normotensive and hypertensive. Post hoc analysis was performed to elicit the significance of differences in the factors levels. The average arterial blood pressure of the group was found to increase significantly with the increase of geomagnetic activity level. The average increment of systolic and diastolic blood pressure of the group examined reached 9%. This effect was present irrespectively of gender. Results obtained suppose that hypertensive persons have the highest sensitivity and the hypotensive persons have the lowest sensitivity of the arterial blood pressure to increase of geomagnetic activity. The results did not show significant changes in the heart rate. The percentage of the persons who reported subjective psycho-physiological complaints was also found to increase significantly with the geomagnetic activity increase and the highest sensitivity was revealed for the hypertensive females.

  18. Major geomagnetic storms and cosmic rays, 2. methods of CR using for forecasting

    NASA Astrophysics Data System (ADS)

    Belov, A. V.; Dorman, L. I.; Eroshenko, E. A.; Gushchina, R. T.; Iucci, N.; Mavromichalaki, H.; Pustilnik, L. A.; Sternlieb, A.; Villoresi, G.; Yanke, V. G.; Zukerman, I. G.

    2001-08-01

    We present developing of methods (e.g., Dorman et al., 1995, 1999) to forecast on the basis of NM hourly on-line data (as well as on-line muon telescopes hourly data from different directions) geomagnetic storms of scales G5 (3-hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) (according to NOAA Space Weather Scales). These geomagnetic storms are dangerous for people technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others). We show that for especially dangerous geomagnetic storms can be used global-spectrographic method if on-line will be available 35-40 NM and muon telescopes. In this case for each hour can be determined CR anisotropy vector, and the specifically behavior of this vector before SC of geomagnetic storms G5, G4 or G3 (according to NOAA Space Weather Scales) can be used as important factor for forecast. The second factor what can be used for SC forecast is specifically behavior of CR density (CR intensity) for about 30-15 hours before SC (caused mainly by galactic CR particles acceleration during interaction with shock wave moved from the Sun). We demonstrate developing methods on several examples of major geomagnetic storms. REFERENCES Dorman L.I., Villoresi G., Belov A.V., Eroshenko E.A., Iucci N., Yanke V.G., Yudakhin K.F., Bavassano B., Ptitsyna N.G., Tyasto M.I., "Cosmic-ray forecasting features for big Forbushdecreases". Nuclear Physics B, Vol. 49A, pp. 136(1995). L.I.Dorman, N.Iucci, N.G.Ptitsyna, G.Villoresi, 1999. Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their prediction , Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, Vol. 6, p.

  19. On the geomagnetic jerk of 1969

    NASA Technical Reports Server (NTRS)

    Mcleod, M. G.

    1985-01-01

    Courtillot et al. (1978) have first reported a sudden change in the slope of the first time derivatives of the geomagnetic field components which occurred around 1970. It was found that the change took place in a large part of the northern hemisphere. Malin and Hodder (1982) reported on studies which were conducted to determine whether this 1970 step change in the second time derivative of the geomagnetic field components, which they termed a geomagnetic 'jerk', was of internal or external origin. It was concluded that internal sources can give rise to changes in secular variation on time scales as short as one or two years and that these were the major factor in the geomagnetic jerk which occurred around 1970. The present paper provides new supporting evidence for the existence of a worldwide geomagnetic jerk, its (average) time of occurrence, and its internal nature. New estimates are given of the spherical harmonic coefficients of the jerk and of the pre-1969 and post-1969 secular acceleration.

  20. The causes of recurrent geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Lepping, R. P.

    1976-01-01

    The causes of recurrent geomagnetic activity were studied by analyzing interplanetary magnetic field and plasma data from earth-orbiting spacecraft in the interval from November 1973 to February 1974. This interval included the start of two long sequences of geomagnetic activity and two corresponding corotating interplanetary streams. In general, the geomagnetic activity was related to an electric field which was due to two factors: (1) the ordered, mesoscale pattern of the stream itself, and (2) random, smaller-scale fluctuations in the southward component of the interplanetary magnetic field Bz. The geomagnetic activity in each recurrent sequence consisted of two successive stages. The first stage was usually the most intense, and it occurred during the passage of the interaction region at the front of a stream. These large amplitudes of Bz were primarily produced in the interplanetary medium by compression of ambient fluctuations as the stream steepened in transit to 1 A.U. The second stage of geomagnetic activity immediately following the first was associated with the highest speeds in the stream.

  1. On the influence of DC railway noise on variation data from Belsk and Lviv geomagnetic observatories

    NASA Astrophysics Data System (ADS)

    Neska, Anne; Reda, Jan; Neska, Mariusz; Sumaruk, Yuri

    2013-04-01

    Geomagnetic variation data from the observatories in Belsk (BEL, Poland) and Lviv (LVV, Ukraine) significantly suffer from disturbances caused by direct current (DC) electric railways. The aim of this study is to quantify the impact of these disturbances on quantities derived from such data, as the K index of magnetic activity and the induction arrow used in the geomagnetic deep sounding method to indicate lateral contrasts of electric conductivity in the solid earth. Therefore, undisturbed data have been reconstructed by means of a frequency-domain transfer function that relates the horizontal magnetic field components of the observatory to the ones synchronously recorded at a noise-free reference station. The comparison of the K index derived from original and reconstructed data shows an increase of quiet time segments by 29% for LVV and by 14% for BEL due to our noise removal procedure. Furthermore, the distribution of the corrected K indices agrees well with the one from the Niemegk observatory in Germany.

  2. Global matrix of thermospheric density values for selected solar/geomagnetic conditions and spacecraft orbital attitudes

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1984-01-01

    Presented are selected thermospheric/exospheric global mean and extreme density values computed between 130 and 1100 km altitude. These values were generated from the MSFC/J70 reference orbital atmospheric model using different input conditions of solar flux and geomagnetic index, ranging from low to peak. Typical magnitudes of day-night density changes are presented, as an example, for use in space vehicle orbital analyses.

  3. Quantifying Power Grid Risk from Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Homeier, N.; Wei, L. H.; Gannon, J. L.

    2012-12-01

    We are creating a statistical model of the geophysical environment that can be used to quantify the geomagnetic storm hazard to power grid infrastructure. Our model is developed using a database of surface electric fields for the continental United States during a set of historical geomagnetic storms. These electric fields are derived from the SUPERMAG compilation of worldwide magnetometer data and surface impedances from the United States Geological Survey. This electric field data can be combined with a power grid model to determine GICs per node and reactive MVARs at each minute during a storm. Using publicly available substation locations, we derive relative risk maps by location by combining magnetic latitude and ground conductivity. We also estimate the surface electric fields during the August 1972 geomagnetic storm that caused a telephone cable outage across the middle of the United States. This event produced the largest surface electric fields in the continental U.S. in at least the past 40 years.

  4. International Geomagnetic Reference Field: the third generation.

    USGS Publications Warehouse

    Peddie, N.W.

    1982-01-01

    In August 1981 the International Association of Geomagnetism and Aeronomy revised the International Geomagnetic Reference Field (IGRF). It is the second revision since the inception of the IGRF in 1968. The revision extends the earlier series of IGRF models from 1980 to 1985, introduces a new series of definitive models for 1965-1976, and defines a provisional reference field for 1975- 1980. The revision consists of: 1) a model of the main geomagnetic field at 1980.0, not continuous with the earlier series of IGRF models together with a forecast model of the secular variation of the main field during 1980-1985; 2) definitive models of the main field at 1965.0, 1970.0, and 1975.0, with linear interpolation of the model coefficients specified for intervening dates; and 3) a provisional reference field for 1975-1980, defined as the linear interpolation of the 1975 and 1980 main-field models.-from Author

  5. An introduction to quiet daily geomagnetic fields

    USGS Publications Warehouse

    Campbell, W.H.

    1989-01-01

    On days that are quiet with respect to solar-terrestrial activity phenomena, the geomagnetic field has variations, tens of gamma in size, with major spectral components at about 24, 12, 8, and 6 hr in period. These quiet daily field variations are primarily due to the dynamo currents flowing in the E region of the earth's ionosphere, are driven by the global thermotidal wind systems, and are dependent upon the local tensor conductivity and main geomagnetic field vector. The highlights of the behavior and interpretation of these quiet field changes, from their discovery in 1634 until the present, are discussed as an introduction to the special journal issue on Quiet Daily Geomagnetic Fields. ?? 1989 Birkha??user Verlag.

  6. Scaling laws from geomagnetic time series

    USGS Publications Warehouse

    Voros, Z.; Kovacs, P.; Juhasz, A.; Kormendi, A.; Green, A.W.

    1998-01-01

    The notion of extended self-similarity (ESS) is applied here for the X - component time series of geomagnetic field fluctuations. Plotting nth order structure functions against the fourth order structure function we show that low-frequency geomagnetic fluctuations up to the order n = 10 follow the same scaling laws as MHD fluctuations in solar wind, however, for higher frequencies (f > l/5[h]) a clear departure from the expected universality is observed for n > 6. ESS does not allow to make an unambiguous statement about the non triviality of scaling laws in "geomagnetic" turbulence. However, we suggest to use higher order moments as promising diagnostic tools for mapping the contributions of various remote magnetospheric sources to local observatory data. Copyright 1998 by the American Geophysical Union.

  7. AAS Publishing News: Astronomical Software Citation Workshop

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-01-01

    Do you write code for your research? Use astronomical software? Do you wish there were a better way of citing, sharing, archiving, or discovering software for astronomy research?Youre not alone! In April 2015, AASs publishing team joined other leaders in the astronomical software community in a meeting funded by the Sloan Foundation, with the purpose of discussing these issues and potential solutions. In attendance were representatives from academic astronomy, publishing, libraries, for-profit software sharing platforms, telescope facilities, and grantmaking institutions.The goal of the group was to establish protocols, policies, and platforms for astronomical software citation, sharing, and archiving, in the hopes of encouraging a set of normalized standards across the field.The AAS is now collaborating with leaders at GitHub to write grant proposals for a project to develop strategies for software discoverability and citation, in astronomy and beyond.If this topic interests you, you can find more details in this document released by the group after the meeting: http://astronomy-software-index.github.io/2015-workshop/The group hopes to move this project forward with input and support from the broader community. Please share the above document, comment on it, discuss it on social media using the hashtag #astroware (so that your conversations can be found!), or send private comments to julie.steffen@aas.org.

  8. Long-term variation in the upper atmosphere as seen in the geomagnetic solar quiet daily variation

    NASA Astrophysics Data System (ADS)

    Shinbori, Atsuki; Koyama, Yukinobu; Nose, Masahito; Hori, Tomoaki; Otsuka, Yuichi; Yatagai, Akiyo

    2014-12-01

    Characteristics of long-term variation in the amplitude of solar quiet (Sq) geomagnetic field daily variation have been investigated using 1-h geomagnetic field data obtained from 69 geomagnetic observation stations within the period of 1947 to 2013. The Sq amplitude observed at these geomagnetic stations showed a clear dependence on the 10- to 12-year solar activity cycle and tended to be enhanced during each solar maximum phase. The Sq amplitude was the smallest around the minimum of solar cycle 23/24 in 2008 to 2009. The relationship between the solar F10.7 index and Sq amplitude was approximately linear but about 53% of geomagnetic stations showed a weak nonlinear relation to the solar F10.7 index. In order to remove the effect of solar activity seen in the long-term variation of the Sq amplitude, we calculated a linear or second-order fitting curve between the solar F10.7 index and Sq amplitude during 1947 to 2013 and examined the residual Sq amplitude, which is defined as the deviation from the fitting curve. As a result, the majority of trends in the residual Sq amplitude that passed through a trend test showed negative values over a wide region. This tendency was relatively strong in Europe, India, the eastern part of Canada, and New Zealand. The relationship between the magnetic field intensity at 100-km altitude and residual Sq amplitude showed an anti-correlation for about 71% of the geomagnetic stations. Furthermore, the residual Sq amplitude at the equatorial station (Addis Ababa) was anti-correlated with the absolute value of the magnetic field inclination. This implies movement of the equatorial electrojet due to the secular variation of the ambient magnetic field.

  9. Empirical STORM-E model: II. Geomagnetic corrections to nighttime ionospheric E-region electron densities

    NASA Astrophysics Data System (ADS)

    Mertens, Christopher J.; Xu, Xiaojing; Bilitza, Dieter; Mlynczak, Martin G.; Russell, James M.

    2013-02-01

    Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region electron densities. The empirical model is called STORM-E and will be incorporated into the 2012 release of the International Reference Ionosphere (IRI). The proxy for characterizing the E-region response to geomagnetic forcing is NO+(v) Volume Emission Rates (VER) derived from the TIMED/SABER 4.3 μm channel limb radiance measurements. The storm-time response of the NO+(v) 4.3 μm VER is most sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO+(v) 4.3 μm VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known nighttime quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. Part I of this series gives a detailed description of the algorithms and methodologies used to derive NO+(v) VER from SABER 4.3 μm limb emission measurements. In this paper, Part II of the series, the development of the E-region electron density storm-time correction factor is described. The STORM-E storm-time correction factor is fit to a single geomagnetic index. There are four versions of the STORM-E model, which are currently independent of magnetic local time. Each version is fit to one of the following indices: HP, AE, Ap, or Dst. High-latitude Incoherent Scatter Radar (ISR) E-region electron density measurements are compared to STORM-E predictions for various geomagnetic storm periods during solar cycle 23. These comparisons show that STORM-E significantly improves the prediction of E-region electron density enhancements due to auroral particle precipitation, in comparison to the nominal IRI model or to the quiet-time baseline electron density concentrations measured by ISR. The STORM-E/ISR comparisons indicate that the STORM-E fits to the Ap-, AE-, and HP-indices are comparable in both absolute accuracy and relative dynamical response. Contrarily, the Dst-index does not appear to be a suitable input driver to parameterize the E-region electron density response to geomagnetic activity.

  10. First geomagnetic measurements in the Antarctic region

    NASA Astrophysics Data System (ADS)

    Raspopov, O. M.; Demina, I. M.; Meshcheryakov, V. V.

    2014-05-01

    Based on data from literature and archival sources, we have further processed and analyzed the results of geomagnetic measurements made during the 1772-1775 Second World Expedition by James Cook and the 1819-1821 overseas Antarctic Expedition by Russian mariners Bellingshausen and Lazarev. Comparison with the GUFM historical model showed that there are systematic differences in the spatial structure of both the declination and its secular variation. The results obtained can serve as a basis for the construction of regional models of the geomagnetic field for the Antarctic region.

  11. Ivory coast microtektites and geomagnetic reversals

    NASA Astrophysics Data System (ADS)

    Schneider, David A.; Kent, Dennis V.

    1990-02-01

    The reported association of the Ivory Coast microtektite occurrence with the onset of the Jaramillo normal polarity subchron has given support to the notion that impact events can give rise to geomagnetic reversals. We re-evaluate the paleomagnetic stratigraphy of two critical deep-sea sediment cores bearing Ivory Coast microtektites (K9-57 and V27-239) and show that this event likely occurred during the Jaramillo subchron approximately 30 kY after its onset and 40 kY before its termination. This new result thus argues against any causal relationship between the Ivory Coast tektite-producing event and a geomagnetic polarity reversal.

  12. Large Geomagnetic Storms: Introduction to Special Section

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.

    2010-01-01

    Solar cycle 23 witnessed the accumulation of rich data sets that reveal various aspects of geomagnetic storms in unprecedented detail both at the Sun where the storm causing disturbances originate and in geospace where the effects of the storms are directly felt. During two recent coordinated data analysis workshops (CDAWs) the large geomagnetic storms (Dst < or = -100 nT) of solar cycle 23 were studied in order to understand their solar, interplanetary, and geospace connections. This special section grew out of these CDAWs with additional contributions relevant to these storms. Here I provide a brief summary of the results presented in the special section.

  13. Satellite data for geomagnetic field modeling

    NASA Astrophysics Data System (ADS)

    Langel, R. A.; Baldwin, R. T.

    1992-06-01

    Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.

  14. Satellite Data for Geomagnetic Field Modeling

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Baldwin, R. T.

    1992-01-01

    Satellite measurements of the geomagnetic fields began with the launch of Sputnik 3 in May of 1958 and have continued sporadically. Spacecraft making significant contributions to main field geomagnetism will be reviewed and the characteristics of their data discussed, including coverage, accuracy, resolution and data availability. Of particular interest are Vanguard 3; Cosmos 49, Ogo's -2, -4, and -6; Magsat; DE-2; and POGS. Spacecraft make measurements on a moving platfrom above the ionosphere as opposed to measurements from fixed observatories and surveys, both below the ionosphere. Possible future missions, such as Aristoteles and GOS are reviewed.

  15. Time scheduling of magnetic surveys in mid-latitudes with respect to forecasting geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Hejda, Pavel; Bochníček, Josef; Horáček, Josef; Nejedlá, Jaroslava

    2006-06-01

    The quality of magnetic surveys is essentially influenced by the geomagnetic activity. As the in situ measurements are usually limited to very short time period, they must be compared with observatory continuous registrations. When reducing measurements one makes an assumption that diurnal variations of the magnetic field are identical at both the station and the reference observatory. During magnetically quite periods, this assumption is satisfied to an acceptable extent. However, under high geomagnetic activity, the error may easily exceed the acceptable limit. Our analysis indicates that, in mid-latitudes, magnetic surveys should not be made, if some of the Kp values are over 5. Long-term and medium-term forecasts of geomagnetic activity are based on known periodicities (11-year, half-year and 27-day). Short-term forecasts are based on the knowledge of the actual conditions on the Sun, in the solar wind and in the interplanetary magnetic field. Regional Warning Centres, associated in the International Space Environment Service (ISES) deal with forecasts of geomagnetic activity. Links to all 12 centres can be obtained through http://www.ises-spaceweather.org/about_ises/index.html.

  16. Local geomagnetic indices and the prediction of auroral power

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Gjerloev, J. W.

    2014-12-01

    The aurora has been related to magnetometer observations for centuries and to geomagnetic indices for decades. As the number of stations and data processing power increases, just how auroral power (AP) relates to geomagnetic observations becomes a more tractable question. This paper compares Polar ultraviolet imager AP observations during 1997 with a variety of indices. Local time (LT) versions of the SuperMAG auroral electrojet (SME) are introduced and examined, along with the corresponding upper and lower envelopes (SMU and SML). Also, the east-west component, BE, is investigated. We also consider whether using any of the local indices is actually better at predicting local AP than a single global index. Each index is separated into 24 LT indices with a sliding 3 h magnetic local time (MLT) window. The ability to predict AP varies greatly with LT, peaking at 19:00 MLT, where about 75% of the variance (r2) is predicted at 1 min cadence. The aurora is fairly predictable from 17:00 MLT to 04:00 MLT, roughly the region in which substorms occur. AP is poorly predicted from auroral electrojet indices from 05:00 MLT to 15:00 MLT, with the minimum at 10:00-13:00 MLT. In the region of high predictability, the local index which works best is BE (east-west), in contrast to long-standing expectations. However, using global SME is better than any local index. AP is best predicted by combining global SME with a local index: BE from 15:00 to 03:00 MLT and either SMU or SML from 03:00 to 15:00 MLT. In the region of the diffuse aurora, it is better to use a 30 min average than the cotemporaneous 1 min SME value, while from 15:00 to 02:00 MLT, the cotemporaneous 1 min SME works best, suggesting a more direct physical relationship with the auroral circuit. These results suggest a significant role for discrete auroral currents closing locally with Pedersen currents.

  17. Geomagnetic transmission of solar energetic protons during the geomagnetic disturbances of October 1989

    NASA Technical Reports Server (NTRS)

    Boberg, P. R.; Tylka, A. J.; Adams J. H., JR.; Flueckiger, E. O.; Kobel, E.

    1995-01-01

    Orbit-averaged geomagnetic transmission measurements during the large solar energetic particle events of October 1989 are presented using proton data from the NOAA-10 and GOES-7 satellies. The measurements are compared to geomagnetic transmission calculations determined by tracing particle trajectories through the combination of the International Geomagnetic Reference Field (IGRF) model and the 1989 Tsyganenko magnetospheric magnetic field model. The effective 'ring current' parameter in the 1989 Tsyganenko model based on the Dst data. Results are compared to calculations employing only the IGRF and to a parameterization of geomagnetically quiet-time cutoff rigidities derived from Cosmos/intercosmos observations. The 3-hour orbit-averaged results have approximately 15% accuracy during the October 1989 events.

  18. Observations in the South Atlantic Geomagnetic Anomaly with Intercosmos-Bulgaria-1300 during a geomagnetic storm

    SciTech Connect

    Gogoshev, M.M.; Gogosheva, TS.N.; Kostadinov, I.N.; Markova, T.I.; Kisovski, S.

    1985-01-01

    The region of South Atlantic Geomagnetic Anomaly was investigated by the Intercosmos-Bulgaria-1300 satellite, launched on August 7, 1981. On the basis of data obtained from 15 orbits during increased geomagnetic activity in August 1981, a map of the Anomaly was elaborated. Two centers of activity were identified. By means of the EMO-5 electrophotometer on board the Intercosmos-Bulgaria-1300 satellite, the atmosphere glow in lines 5577 A, 6300 A and 4278 A was studied. 11 references.

  19. Modeling geomagnetic cutoffs for space weather applications

    NASA Astrophysics Data System (ADS)

    Kress, B. T.; Hudson, M. K.; Selesnick, R. S.; Mertens, C. J.; Engel, M.

    2015-07-01

    Access of solar and galactic cosmic rays to the Earth's magnetosphere is quantified in terms of geomagnetic cutoff rigidity. Numerically computed grids of cutoff rigidities are used to model cosmic ray flux in Earth's atmosphere and in low Earth orbit. In recent years, the development of more accurate dynamic geomagnetic field models and an increase in computer power have made a real-time data-driven geomagnetic cutoff computation extending over the inner magnetosphere possible. For computational efficiency, numerically computed cutoffs may be scaled to different altitudes and directions of arrival using the known analytic variation of cutoff in a pure dipole magnetic field. This paper is a presentation of numerical techniques developed to compute effective cutoff rigidities for space weather applications. Numerical tests to determine the error associated with scaling vertical cutoff rigidities with altitude in a realistic geomagnetic field model are included. The tests were performed to guide the development of spatial grids for modeling cosmic ray access to the inner magnetosphere and to gain a better understanding of the accuracy of numerically modeled cutoffs.

  20. F2-region response to geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Danilov, A. D.

    2001-03-01

    The F2-region response to a geomagnetic storm usually called a ionospheric storm is a rather complicated event. It consists of the so-called positive an negative phases, which have very complicated spatial and temporal behavior. During the recent decade there was significant progress in understanding this behavior. The principal features of the positive and negative phase distribution and variations have been explained on the basis of the principal concept: during a geomagnetic disturbance there is an input of energy into the polar ionosphere, which changes thermospheric parameters, such as composition, temperature and circulation. Composition changes directly influence the electron concentration in the F2 region. The circulation spreads the heated gas to lower latitudes. The conflict between the storm-induced circulation and the regular one determines the spatial distribution of the negative and positive phases in various seasons. There are still problems unsolved. The most acute ones are: the appearance of positive phases before the beginning of a geomagnetic disturbance, the occurence of strong negative phases at the equator, the role of vibrationally excited nitrogen in forming the negative phase, and the relation of positive phases to the dayside cusp. There are indications that the foF2 long-term trends revealed during the recent years may be explained by long-term trends of the number of negative ionospheric disturbances due to secular variations of the geomagnetic activity.

  1. Space radiation enhancement linked to geomagnetic disturbances.

    PubMed

    Tomita, F; Den, M; Doke, T; Hayashi, T; Nagaoka, T; Kato, M

    1997-12-01

    Space radiation dosimetry measurements have been made on board the Space Shuttle. A newly developed active detector called "Real-time Radiation Monitoring Device (RRMD)" was used (Doke et al., 1995; Hayashi et al., 1995). The RRMD results indicate that low Linear Energy Transfer (LET) particles steadily penetrate around the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent and some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions (Doke et al., 1996). We also have been analyzing the space weather during the experiment, and found that the anomalous high-energy particle enhancement was linked to geomagnetic disturbance due to the high speed solar wind from a coronal hole. Additional analysis and other experiments are necessary for clarification of these phenomena. If a penetration of high-energy particles into the low altitude occurs by common geomagnetic disturbances, the prediction of geomagnetic activity becomes more important in the next Space Station's era. PMID:11541771

  2. Space radiation enhancement linked to geomagnetic disturbances.

    PubMed

    Tomita, F; Den, M; Doke, T; Hayashi, T; Nagaoka, T; Kato, M

    1998-01-01

    Space radiation dosimetry measurements have been made on board the Space Shuttle. A newly developed active detector called "Real-time Radiation Monitoring Device (RRMD)" was used (Doke et al., 1995; Hayashi et al., 1995). The RRMD results indicate that low Linear Energy Transfer (LET) particles steadily penetrate around the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent and some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions (Doke et al., 1996). We also have been analyzing the space weather during the experiment, and found that the anomalous high-energy particle enhancement was linked to geomagnetic disturbance due to the high speed solar wind from a coronal hole. Additional analysis and other experiments are necessary for clarification of these phenomena. If a penetration of high-energy particles into the low altitude occurs by common geomagnetic disturbances, the prediction of geomagnetic activity becomes more important in the next Space Station's era. PMID:11541929

  3. Modelling of geomagnetic induction in pipelines

    NASA Astrophysics Data System (ADS)

    Trichtchenko, L.; Boteler, D. H.

    2002-07-01

    Geomagnetic field variations induce telluric currents in pipelines, which modify the electrochemical conditions at the pipe/soil interface, possibly contributing to corrosion of the pipeline steel. Modelling of geomagnetic induction in pipelines can be accomplished by combining several techniques. Starting with geomagnetic field data, the geoelectric fields in the absence of the pipeline were calculated using the surface impedance derived from a layered-Earth conductivity model. The influence of the pipeline on the electric fields was then examined using an infinitely long cylinder (ILC) model. Pipe-to-soil potentials produced by the electric field induced in the pipeline were calculated using a distributed source transmission line (DSTL) model. The geomagnetic induction process is frequency dependent; therefore, the calculations are best performed in the frequency domain, using a Fourier transform to go from the original time domain magnetic data, and an inverse Fourier transform at the end of the process, to obtain the pipe-to-soil potential variation in the time domain. Examples of the model calculations are presented and compared to observations made on a long pipeline in the auroral zone.

  4. What do we mean by accuracy in geomagnetic measurements?

    USGS Publications Warehouse

    Green, A.W., Jr.

    1990-01-01

    High accuracy is what distinguishes measurements made at the world's magnetic observatories from other types of geomagnetic measurements. High accuracy in determining the absolute values of the components of the Earth's magnetic field is essential to studying geomagnetic secular variation and processes at the core mantle boundary, as well as some magnetospheric processes. In some applications of geomagnetic data, precision (or resolution) of measurements may also be important. In addition to accuracy and resolution in the amplitude domain, it is necessary to consider these same quantities in the frequency and space domains. New developments in geomagnetic instruments and communications make real-time, high accuracy, global geomagnetic observatory data sets a real possibility. There is a growing realization in the scientific community of the unique relevance of geomagnetic observatory data to the principal contemporary problems in solid Earth and space physics. Together, these factors provide the promise of a 'renaissance' of the world's geomagnetic observatory system. ?? 1990.

  5. CO2 laser welding of aluminium shipbuilding industry alloys: AA 5083, AA 5383, AA 5059, and AA 6082

    NASA Astrophysics Data System (ADS)

    Ancona, Antonio; Daurelio, G.; De Filippis, L. A. C.; Ludovico, A. D.; Spera, A. M.

    2003-11-01

    Aluminum alloys are interesting in many and many industrial applications, from the classical aircraft industry to rail and road vehicles manufacturing (High Speed Train, Car Structure and Body). Recently much more attention for Aluminum Alloys, 5000 and 6000 Series, has been carried out by Shipbuilding Industry, especially for using in the H.S.L.C. (High Speed Light Craft). Therefore the aim of this experimental work has been to study, develop and test a reproducible CO2 laser welding procedure and technique of four specific alloys, that is AA 5083, AA 5383, AA 5059 (Al-Mg Alloys), and AA 6082 (Al-Mg-Si Alloy). Different techniques, methodologies, covering gases, nozzles, focusing lenses and mirrors, welding speed range, laser power range (1000 and 2500 W) have been carefully experimented. The melted zones properties have been evaluated by cross sections, and some visual inspections by a NIKON LUCIA Imaging System correlating each experimental test, results and evaluations to the adopted process parameters and to the thermo-physical properties of the tested alloys.

  6. Comment on "Possible association between anomalous geomagnetic variations and the Molise Earthquakes at Central Italy during 2002" by Takla et al. (2011)

    NASA Astrophysics Data System (ADS)

    Masci, Fabrizio

    2012-08-01

    Takla et al. (2011) documented the observation of seismogenic precursory signals in the geomagnetic field components of L'Aquila station (LAQ) which occurred before the 2002 Molise earthquakes. Here, these claims are reviewed taking into account the geomagnetic index ?Kp time-series and by means of data coming from the Geomagnetic Observatory of L'Aquila where the LAQ station is located. This review shows that before the Molise earthquakes the anomalous behaviour of LAQ geomagnetic field components was actually caused by a possible thermal drift of the instrumentation. In conclusion there is no firm relation between the earthquakes occurrence and the observed magnetic anomalous signatures documented by Takla et al. (2011).

  7. The Effect of Helio-Geomagnetic Activity on the Proceedings in the Emergency Department of Two Greek Hospitals

    NASA Astrophysics Data System (ADS)

    Preka-Papadema, P.; Moussas, X.; Noula, M.; Katranitsa, H.; Theodoropoulou, A.; Katsavrias, Ch.; Vasiliou, Ch.; Kontogeorgou, E.; Tsaliki, S.-M.; Kailas, K.; Papadima, Th.

    2010-01-01

    Study of the solar and geomagnetic activity influence on the emergency proceedings in Greece, for selected months of solar cycle 23 and especially for the year 2005 is presented. We examined the time association between the magnetic storms (Dst geomagnetic index), daily numbers of solar flares and Coronal Mass Ejections (CMEs) with the emergency proceedings. The sample of about 30000 cases from two Greek hospitals (The General Hospital of the town of Lamia and The General Hospital of the town of Veria) analyzed according to diagnoses. The cardiological, neurological, accidents (multitrauma and burns) and oncological patients as well as in partially pathological/surgical patients showed an increase during periods of high helio-geomagnetic activity. In order to strengthen this result, more data need to be collected and analyzed.

  8. Geomagnetic field evolution during the Laschamp excursion

    NASA Astrophysics Data System (ADS)

    Leonhardt, Roman; Fabian, Karl; Winklhofer, Michael; Ferk, Annika; Laj, Carlo; Kissel, Catherine

    2009-02-01

    Since the last geomagnetic reversal, 780,000 years ago, the Earth's magnetic field repeatedly dropped dramatically in intensity. This has often been associated with large variations in local field direction, but without a persistent global polarity flip. The structure and dynamics of geomagnetic excursions, and especially the difference between excursions and polarity reversals, have remained elusive so far. For the best documented excursion, the Laschamp event at 41,000 years BP, we have reconstructed the evolution of the global field morphology by using a Bayesian inversion of several high-resolution palaeomagnetic records. We have obtained an excursion scenario in which inverse magnetic flux patches at the core-mantle boundary emerge near the equator and then move poleward. Contrary to the situation during the last reversal (Leonhardt, R., Fabian, K., 2007. Paleomagnetic reconstruction of the global geomagnetic field evolution during the Matuyama/Brunhes transition: Iterative Bayesian inversion and independent verification. Earth Planet. Sci. Lett. 253, 172-195), these flux patches do not cross the hydrodynamic boundary of the inner-core tangent cylinder. While the last geomagnetic reversal began with a substantial increase in the strength of the non-dipolar field components, prior to the Laschamp excursion, both dipolar and non-dipolar field decay at the same rate. This result suggests that the nature of an upcoming geomagnetic field instability can be predicted several hundred years in advance. Even though during the Laschamp excursion the dipolar field at the Earth's surface was dominant, the reconstructed dynamic non-dipolar components lead to considerable deviations among predicted records at different locations. The inverse model also explains why at some locations no directional change during the Laschamp excursion is observed.

  9. What causes geomagnetic activity during sunspot minimum?

    NASA Astrophysics Data System (ADS)

    Kirov, B.; Asenovski, S.; Georgieva, K.; Obridko, V. N.

    2015-12-01

    It is well known that the main drivers of geomagnetic disturbances are coronal mass ejections whose number and intensity are maximum in sunspot maximum, and high speed solar wind streams from low latitude solar coronal holes which maximize during sunspot declining phase. But even during sunspot minimum periods when there are no coronal mass ejections and no low latitude solar coronal holes, there is some "floor" below which geomagnetic activity never falls. Moreover, this floor changes from cycle to cycle. Here we analyze the factors determining geomagnetic activity during sunspot minimum. It is generally accepted that the main factor is the thickness of the heliospheric current sheet on which the portion of time depends which the Earth spends in the slow and dense heliospheric current sheet compared to the portion of time it spends in the fast solar wind from superradially expanding polar coronal holes. We find, however, that though the time with fast solar wind has been increasing in the last four sunspot minima, the geomagnetic activity in minima has been decreasing. The reason is that the parameters of the fast solar wind from solar coronal holes change from minimum to minimum, and the most important parameter for the fast solar wind's geoeffectivityits dynamic pressurehas been decreasing since cycle 21. Additionally, we find that the parameters of the slow solar wind from the heliospheric current sheet which is an important driver of geomagnetic activity in sunspot minimum also change from cycle to cycle, and its magnetic field, velocity and dynamic pressure have been decreasing during the last four minima.

  10. Surface electromagnetic impedance and geomagnetic activity: results of long term observation

    NASA Astrophysics Data System (ADS)

    Lemperger, Istvn; Menvielle, Menvielle; Wesztergom, Viktor; Bencze, Pl; Szendr?i, Judit; Novk, Attila; Kis, rpd; Szalai, Sndor

    2014-05-01

    The magnetotelluric (MT) method is one of the most useful geophysical tool to discover even the deep subsurface structures. The target function of the MT data processing is the surface electromagnetic (EM) impedance. In case of practical MT exploration the surface EM impedance is computed based on a simplification related to the nature of the ionospheric source of the surface EM signals. Assuming that the ionospheric current systems result in homogeneous surface electromagnetic variations, the uncertainty of the computed surface electromagnetic impedance tensor depends only the duration of the EM observation. However the surface EM field can only be approached by plane waves in certain time periods and besides given uncertainty. The EM impedance may be sensitive to magnetospheric and -indirectly- interplanetary circumstances and solar activity. Four years continuous observation of telluric and surface geomagnetic components allowed to perform a representative survey to discover if geomagnetic activity has any effect on observed EM impedance tensor. Geomagnetic indices (Dst, ULF-index, ASY-H, SYM-H) have been used to classify dates according to geomagnetic activity. Processing to estimate the mean surface EM impedance tensor has been performed in each dataset, each class separately. The sensitivity and the characteristics of the answer of the EM impedance tensor to the geomagnetic disturbances seems to be definite. This presentation aims to briefly summarize the preliminary results of our study based on the unique dataset of the Szchenyi Istvn Geophysical Obsevatory (Intermagnet code:NCK). In addition, pointing out the limitations of the routine way of practical MT data processing and interpretation is an important duty of this study. This study was supported by the TAMOP-4.2.2.C-11/1/KONV-2012-0015 (Earth-system) project sponsored by the EU and European Social Foundation.

  11. A study of OI 844.6 nm dayglow emission under geomagnetic storm conditions

    NASA Astrophysics Data System (ADS)

    Dharwan, Maneesha; Singh, Vir

    2015-06-01

    A comprehensive model is developed to study 844.6 nm dayglow emission. The Solar2000 EUV (extreme ultraviolet) flux model, neutral atmosphere model (NRLMSISE-00) and latest available cross-sections are incorporated in this model. The present model is used to study the effects of geomagnetic storm on the 844.6 nm dayglow emission at a low latitude station Tirunelveli (8.7°N, 77.8°E). Three geomagnetic storms which occurred during 23rd-27th August 2005, 13th-17th April 2006 and 1st-5th February 2008 are chosen in the present study. It is found that the volume emission rate (VER) shows a negative correlation with the Dst index for all the three geomagnetic storms. The present study also shows that the altitude of the peak emission rate does not vary with the activity of geomagnetic storm. The model predicts a positive correlation between the zenith intensity of 844.6 nm dayglow emission and atomic oxygen number density. The consistency of atomic oxygen number density obtained from the NRLMSISE-00 model during a geomagnetic storm is checked using the satellite measurements of Earle et al. (2013). It is found that the atomic oxygen number density given by NRLMSISE-00 model is significantly lower than the measured values. Consequently, the effect of atomic oxygen number density abundance on 844.6 nm dayglow emission is further studied by treating the atomic oxygen number density as a variable parameter in the present model. An increase of more than 50% in the zenith intensity above the normal level (before the onset of the storm) is found when the atomic oxygen number density which is obtained from NRLMSISE-00 model is doubled (under the limits of measurements).

  12. Near real-time geomagnetic data for space weather applications in the European sector

    NASA Astrophysics Data System (ADS)

    Johnsen, M. G.; Hansen, T. L.

    2012-12-01

    Troms Geophysical Observatory (TGO) is responsible for making and maintaining long time-series of geomagnetic measurements in Norway. TGO is currently operating 3 geomagnetic observatories and 11 variometer stations from southern Norway to Svalbard . Data from these 14 locations are acquired, processed and made available for the user community in near real-time. TGO is participating in several European Union (EU) and European Space Agency (ESA) space weather related projects where both near real-time data and derived products are provided. In addition the petroleum industry is benefiting from our real-time data services for directional drilling. Near real-time data from TGO is freely available for non-commercial purposes. TGO is exchanging data in near real-time with several institutions, enabling the presentation of near real-time geomagnetic data from more than 40 different locations in Fennoscandia and Greenland. The open exchange of non real-time geomagnetic data has been successfully going on for many years through services such as the world data center in Kyoto, SuperMAG, IMAGE and SPIDR. TGO's vision is to take this one step further and make the exchange of near real-time geomagnetic data equally available for the whole community. This presentation contains an overview of TGO, our activities and future aims. We will show how our near real-time data are presented. Our contribution to the space weather forecasting and nowcasting effort in the EU and ESA will be presented with emphasis on our real-time auroral activity index and brand new auroral activity monitor and electrojet tracker.

  13. No covariation between the geomagnetic activity and the incidence of acute myocardial infarction in the polar area of northern Sweden.

    PubMed

    Messner, T; Hggstrm, I; Sandahl, I; Lundberg, V

    2002-05-01

    This study was undertaken to investigate whether there was any relation between the aurora borealis (measured as the geomagnetic activity) and the number of acute myocardial infarctions (AMI) in the northern, partly polar, area of Sweden. The AMI cases were collected from The Northern Sweden MONICA (multinational MONItoring of trends and determinants of CArdiovascular disease) AMI registry between 1985 and 1998, inclusive, and the information on the geomagnetic activity from continuous measurements at the Swedish Institute of Space Physics, Kiruna. In the analyses, both the relation between the individual AMI case and ambient geomagnetic activity, and the relation between the mean daily K index and the daily number of AMI cases were tested. We found no statistically significant relation between the number of fatal or non-fatal AMI cases, the number of sudden deaths or the number of patients with chest pain without myocardial damage, and geomagnetic activity. Our data do not support a relation between the geomagnetic activity and AMI. PMID:12135204

  14. Monitoring the ionospheric total electron content variations over the Korean Peninsula using a GPS network during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Choi, Byung-Kyu; Lee, Sang-Jeong; Park, Jong-Uk

    2011-06-01

    We have established a regional ionospheric model (RIM) for investigating changes in the total electron content (TEC) over South Korea using 38 Korean GPS reference stations. The inverse distance weighted (IDW) interpolation method was applied to create a two-dimensional ionospheric map of vertical TEC units (TECU) based on a grid. To examine the diurnal patterns of ionospheric TEC over South Korea, we first processed the GPS data from a geomagnetically quiet period of 10 days. In a second step, we compared the estimated GPS-TEC variations with the changes in geomagnetic activity indices (the K p and D st indices) and the auroral electrojet index (AE) as a function of universal time (UT) on 4 and 20 November, 2003. The GPS-TEC responses for those storm events were proportional to the geomagnetic activity at this mid-latitude location. The sudden increases in ionospheric TEC (SITEC) caused by the geomagnetic storms were detected. The variations in GPS-TEC may help reveal the processes of ionospheric disturbances caused by geomagnetic storms.

  15. Global empirical model of TEC response to geomagnetic activity: Short-term (24 hours ahead) prediction model

    NASA Astrophysics Data System (ADS)

    Andonov, Borislav

    2013-04-01

    A global empirical model of the rTEC=(TECobs-TECmed)/TECmed depending on the geomagnetic activity (described by the Kp-index) and at a given moment is built by using global TEC data for full 13 years between 1999 and 2011.The data are downloaded from the CODE (Center for Orbit Determination in Europe) database in the Astronomical Institute, University of Bern. By using a 2D cross-correlation analysis it is found that the ionospheric response to the geomagnetic activity revealed both positive and negative phases of the response. The both phases of the ionospheric response have different duration and time delay with respect to the geomagnetic storm. It was found that these two parameters of the ionospheric response depend on the season, geographical/geomagnetic coordinates and local time. The rTEC response is represented by 2D (longitude-time) sine waves with different zonal wavenumbers and periods being harmonics of the diurnal period. The input data for the current and predicted geomagnetic activity are obtained from the MAK model developed in NIGGG-BAS, which uses the solar wind measurements from the ACE satellite. The background condition is defined by the recent CODE TEC maps. For each current hour the model provides predicted global TEC maps in geographic frame for the next 24 hours.

  16. Cosmic Ray Monitoring and Space Dangerous Phenomena, 1. Search of Features In Cosmic Rays What Can Be Used For Forecasting of Major Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Pustil'Nik, L. A.; Sternlieb, A.; Zukerman, I. G.

    According to NOAA Space Weather Scales, geomagnetic storms of scales G5 (3- hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) are dangerous for people technology and health (influence on power systems, on spacecraft oper- ations, on HF radio-communications and others). To prevent these serious damages will be very important to forecast dangerous geomagnetic storms. In many papers it was shown that in principle for this forecasting can be used data on CR intensity and CR anisotropy changing before SC of major geomagnetic storms accompanied by sufficient Forbush-decreases (e.g., Dorman et al., 1995, 1999). In this paper we con- sider over 100 major geomagnetic storms and for each case we analyze hourly data of many NM for 8 days with SC in the 4-st day of 8-days period (that before SC we have at least 3 full days). We determine what part of major geomagnetic storms is accompanied CR intensity and CR anisotropy changing before SC, and what part of major geomagnetic storms does not show any features what can be used for forecast- ing. We estimate also how these parts depend from the index of geomagnetic activ- ity Kp. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, Vol. 49A, pp. 136-144. (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their prediction", Proc. of 26-th Intern. Cos- mic Ray Conference, Salt Lake City, Vol. 6, p. 476-479, (1999).

  17. Circulation changes in the winter lower atmosphere and long-lasting solar/geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Bochn?ek, J.; Davdkovov, H.; Hejda, P.; Huth, R.

    2012-12-01

    The paper describes the association between high long-lasting solar/geomagnetic activity and geopotential height (GPH) changes in the winter lower atmosphere, based on their development in the Northern Hemisphere in the winter periods (December-March) of 1950-1969 and 1970-2002. Solar/geomagnetic activity is characterised by the 60-day mean of the sunspot number R/by the 60-day mean of the daily sum of the Kp index. The GPH distributions in the lower atmosphere are described by 60-day anomalies from their long-term daily average at 20 hPa/850 hPa. The data have been adopted from the NCEP/NCAR reanalysis. The 60-day mean values of solar/geomagnetic activity and GPH anomalies were calculated in five-day steps over the whole winter period. The analysis was carried out using composite maps which represent their distribution of the GPH anomalies during high solar activity (R ? 100) and high geomagnetic activity (?Kp ? 20). Analysis has shown that the distribution of GPH anomalies depends on solar activity, geomagnetic activity and the phase of winter period (early or late winter). The nature of this relationship then depends on the time interval involved, i.e. 1950-1969 or 1970-2002. Positive anomalies in the polar stratosphere (20 hPa) were detected during the whole winter periods of the years 1950-1969. Significant anomalies were detected in the lower troposphere (850 hPa) during the second half of the winter period. The distribution of GPH anomalies on the maps compiled with regard to solar activity was similar to the distribution on maps compiled with regard to geomagnetic activity. In the interval 1970-2002, significant negative GPH anomalies were detected in the stratosphere at high latitudes, and positive anomalies were detected in the region of low latitudes. The distribution of GPH anomalies in the lower troposphere was substantially affected by situations in which, together with high solar activity, also high geomagnetic activity occurred.

  18. Empirical modeling of the storm time geomagnetic indices: a comparison between the local K and global Kp indices

    NASA Astrophysics Data System (ADS)

    Uwamahoro, Jean; Habarulema, John Bosco

    2014-12-01

    This paper describes a neural network-based model developed to predict geomagnetic storms time K index as measured at a magnetic observatory located in Hermanus (3425 S; 1913 E), South Africa. The parameters used as inputs to the neural network were the solar wind particle density N, the solar wind velocity V, the interplanetary magnetic field (IMF) total average field B t as well as the IMF B z component. Averaged hourly OMNI-2 data comprising storm periods extracted from solar cycle 23 (SC23) were used to train the neural network. The prediction performance of this model was tested on some moderate to severe storms (with K?5) that were not included in the training data set and the results are compared to the prediction of the global geomagnetic Kp index. The model results show a good predictability of the Hermanus storm time K index with a correlation coefficient of 0.8.

  19. Environmental and geomagnetic factors in relation to self-destructive ideation and behaviour

    NASA Astrophysics Data System (ADS)

    Bergiannaki, J. D.; Psarros, C.; Nastos, P. Th.; Paparigopoulos, T.; Paliatsos, A. G.; Tritakis, V. P.; Stefanis, C. N.

    2001-09-01

    Besides the individual factors such as the reaction to conflicts, several exogenous factors environmental and social may exert a pathogenic influence on suicidal behavior, suicide attempts and complete suicide on predisposed individuals. In the turn of the century many reports accord for the seasonality of suicides, which seems to have a bimodal distribution with a major peak around the spring-summer (April-May) and a second minor in autumn. On the other hand, the seasonal variation of environmental factors (daylight, sunlight duration, weather, temperature, air pressure, humidity, geomagnetism, solar activity, etc), of biological factors (melatonin, serotonin, serotonin precursors, etc) as also of sociological factors (ethnic events, major holidays, weekends etc) possibly influences the seasonal pattern of self-destructive behavior. Bimodal seasonal variation is also reported for biochemical parameters (L-tryptophan, serotonin, endorphin I fraction) that matches seasonal pattern in the prevalence of violent suicide in the total population and also in the incidence of the affective disorders. The aim of this study is to investigate the relation of environmental factors expressed by the Discomfort Index (DI) and geomagnetic factors expressed by the geomagnetic field Index DST in relation to suicidal behavior. The total number (4803) of patients recorded in the Ambulance of a Phychiatric Hospital (Eginition) throughout 1994 was used along with the records of 2750 patients of the year 1989. The Index DI is a function of dry and wet-bulb temperature. DST is probably one of the geomagnetic indices that expresses and monitors with the greatest accuracy the equatorial ring current variations. Our results show that there is a seasonal variation of suicidal behavior (Fourier analysis) with a major peak during summer (July) and a minor one during spring. A difference in the occurrence of the peaks was observed among genders. A relation of self-destructive behavior and the daily changes of the geomagnetic index DST was found. This was significant with a latency of three days. As reported in the literature, serotonin, which is involved in the presence of suicide, was found to be magnetosensitive with a latency of three days. The contextual influence of the above factors in suicidal behavior will be discussed.

  20. Solar Flares and Proton Events driving particle precipitation at higher latitudinal geomagnetic environment

    NASA Astrophysics Data System (ADS)

    Tripathi, S. C.; Khan, P. A.; Gwal, A. K.; Purohit, P. K.

    2013-12-01

    Solar flares, a solar transient producing radiation storm, are thought to be produced at the corona due to magnetic reconnection at solar corona and Solar Energetic particles, another solar transient, are the shower of high energy charged particles and are hazardous to the space environment have good association in their genesis. Spectral analysis of the solar flares associated with the solar proton events make us infer that the solar protons are produced in association with those solar flares which has SHH spectral behavior. These solar protons after interaction with earth's magnetic environment precipitate at the higher latitudinal magnetic environment and have good association with the high latitudinal geomagnetic index PC and its growth rate, which shows that the disturbances in the high latitudinal geomagnetic environment have the close connection with the solar energetic particle events. For the present study 50 solar energetic particle events and their associated flares of 23 solar cycle have been taken into consideration.

  1. Geomagnetic storm's precursors observed from 2001 to 2007 with the Global Muon Detector Network (GMDN)

    NASA Astrophysics Data System (ADS)

    Rockenbach, M.; Dal Lago, A.; Gonzalez, W. D.; Munakata, K.; Kato, C.; Kuwabara, T.; Bieber, J.; Schuch, N. J.; Duldig, M. L.; Humble, J. E.; Al Jassar, H. K.; Sharma, M. M.; Sabbah, I.

    2011-08-01

    We use complementary observations from the prototype and expanded Global Muon Detector Network (GMDN) and the Advanced Composition Explorer (ACE) satellite to identify precursors of geomagnetic storm events. The GMDN was completed and started operation in March 2006 with the addition of the Kuwait detector, complementing the detectors at Nagoya, Hobart, and So Martinho da Serra. Analyzed geomagnetic storms sorted by their intensity as measured by the Disturbance storm-time (Dst) index. Between March 2001 and December 2007, 122 Moderate Storms (MS), 51 Intense Storms (IS), and 8 Super Storms (SS) were monitored by the GMDN. The major conclusions are (i) the percentage of the events accompanied by the precursors prior to the Sudden Storm Commencement (SSC) increases with increasing peak Dst, (ii) 15% of MSs, 30% of ISs, and 86% of SSs are accompanied by cosmic ray precursors observed on average 7.2 hours in advance of the SSC.

  2. [A comprehensive analysis of incidence of myocardial infarction in Vladikavkaz depending on solar and geomagnetic activity].

    PubMed

    Botoeva, N K; Khetarugova, l G; Rapoport, S I

    2013-01-01

    The data on myocardial infarction morbidity in Vladikavkaz for 2007-2010 were analysed with reference to solar and geomagnetic activity. Time series of morbidity in men and women were constructed and their seasonal constituent was distinguished. It was found that the number of myocardial infarctions increases on day with enhanced geomagnetic activity especially among subjects aged 50-69 years. Regression analysis of the relationship between the number of sunspots and myocardial infarctions yielded the equation of piecewise linear regression showing that 42% of the cases were due to the changes in the number of sunspots. Medium strength negative correlation was found between the number of myocardial infarctions and the recurrence index of Bz-component of the interplanetary magnetic field. It suggests an important role of chaotic dynamics of external factors in the development of myocardial infarction. PMID:25696947

  3. Cross-spectral coherence between geomagnetic disturbance and human cardiovascular variables at non-societal frequencies.

    PubMed

    Watanabe, Y; Hillman, D C; Otsuka, K; Bingham, C; Breus, T K; Cornlissen, G; Halberg, F

    1994-01-01

    A 35-year-old cardiologist monitored himself with an automatic ABPM-630 (Colin Electronics) monitor, mostly at 15-minute intervals around-the-clock for three years with a few interruptions. In this subject with a family history of high blood pressure and stroke, a cross-spectral analysis revealed a statistically significant coherence at 27.7 days between systolic and diastolic blood pressure and heart rate vs. the geomagnetic disturbance index, Kp. A lesser peak in coherence was found for systolic blood pressure with Kp at a trial period of 4.16 days (P = 0.046). These results suggest that changes in geomagnetism may influence the human circulation, at least in the presence of familial cardiovascular disease risk, and they may do so at frequencies that have no precise human-made cyclic worldwide match. PMID:7729242

  4. Steady induction effects in geomagnetism. Part 1A: Steady motional induction of geomagnetic chaos

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    1992-01-01

    Geomagnetic effects of magnetic induction by hypothetically steady fluid motion and steady magnetic flux diffusion near the top of Earth's core are investigated using electromagnetic theory, simple magnetic earth models, and numerical experiments with geomagnetic field models. The problem of estimating a steady fluid velocity field near the top of Earth's core which induces the secular variation indicated by broad-scale models of the observed geomagnetic field is examined and solved. In Part 1, the steady surficial core flow estimation problem is solved in the context of the source-free mantle/frozen-flux core model. In the first paper (IA), the theory underlying such estimates is reviewed and some consequences of various kinematic and dynamic flow hypotheses are derived. For a frozen-flux core, fluid downwelling is required to change the mean square normal magnetic flux density averaged over the core-mantle boundary. For surficially geostrophic flow, downwelling implies poleward flow. The solution of the forward steady motional induction problem at the surface of a frozen-flux core is derived and found to be a fine, easily visualized example of deterministic chaos. Geomagnetic effects of statistically steady core surface flow may well dominate secular variation over several decades. Indeed, effects of persistent, if not steady, surficially geostrophic core flow are described which may help explain certain features of the present broad-scale geomagnetic field and perhaps paleomagnetic secular variation.

  5. Polarity transition records and the geomagnetic dynamo.

    PubMed

    Hoffman, K A

    1977-06-17

    The Parker-Levy approach to reversals of the geomagnetic field predicts meridional transitional paths of the virtual geomagnetic pole (VGP) which pass either through the site of observation or through its antipode, depending upon the site location and the sense of the polarity transition. Comparison with the most detailed transitional VGP path records presently available gives some indication of the above behavior as predicted by the Parker-Levy model. Discrepancies may be due to complexities in the distribution of cyclonic convection cells in the core not considered in the formal mathematical treatment. The predicted variation in transitional field intensity experienced at any given site also is compatible with several reported transition records. PMID:17831750

  6. Geomagnetic and Solar Indices Data at NGDC

    NASA Astrophysics Data System (ADS)

    Mabie, J. J.

    2012-12-01

    The National Geophysical Data Center, Solar and Terrestrial Physics Indices program is a central repository for global indices derived at numerous organizations around the world. These datasets are used by customers to drive models, evaluate the solar and geomagnetic environment, and to understand space climate. Our goal is to obtain and disseminate this data in a timely and accurate manner, and to provide the short term McNish-Lincoln sunspot number prediction. NGDC is in partnership with the NOAA Space Weather Prediction Center (SWPC), University Center for Atmospheric Sciences (UCAR), the Potsdam Helmholtz Center (GFZ), the Solar Indices Data Center (SIDC), the World Data Center for Geomagnetism Kyoto and many other organizations. The large number of available indices and the complexity in how they are derived makes understanding the data one of the biggest challenges for the users of indices. Our data services include expertise in our indices and related datasets to provide feedback and analysis for our global customer base.

  7. Lower mantle superplume growth excites geomagnetic reversals

    NASA Astrophysics Data System (ADS)

    Amit, Hagay; Peter, Olson

    2015-04-01

    Seismic images of the lower mantle reveal two large-scale, low shear wave velocity provinces beneath Africa and the Pacific that are variously interpreted as superplumes, plume clusters or piles of dense mantle material associated with the D" layer. Here we show that time variations in the height of these structures produce variations in heat flux across the core-mantle boundary that can control the rate at which geomagnetic polarity reversals occur. Superplume growth increases the mean core-mantle boundary heat flux and its lateral heterogeneity, thereby stimulating polarity reversals, whereas piles collapse decreases the mean core-mantle boundary heat flux and its lateral heterogeneity, inhibiting polarity reversals. Our results suggest that the long, stable polarity geomagnetic superchrons such as occurred in the Cretaceous, Permian, and earlier in the geologic record were initiated and terminated by the collapse and growth of lower mantle superplumes, respectively.

  8. Lower mantle superplume growth excites geomagnetic reversals

    NASA Astrophysics Data System (ADS)

    Amit, Hagay; Olson, Peter

    2015-03-01

    Seismic images of the lower mantle reveal two large-scale, low shear wave velocity provinces beneath Africa and the Pacific that are variously interpreted as superplumes, plume clusters or piles of dense mantle material associated with the D? layer. Here we show that time variations in the height of these structures produce variations in heat flux across the core-mantle boundary that can control the rate at which geomagnetic polarity reversals occur. Superplume growth increases the mean core-mantle boundary heat flux and its lateral heterogeneity, thereby stimulating polarity reversals, whereas superplume collapse decreases the mean core-mantle boundary heat flux and its lateral heterogeneity, inhibiting polarity reversals. Our results suggest that the long, stable polarity geomagnetic superchrons such as occurred in the Cretaceous, Permian, and earlier in the geologic record were initiated and terminated by the collapse and growth of lower mantle superplumes, respectively.

  9. Geomagnetic modeling by optimal recursive filtering

    NASA Technical Reports Server (NTRS)

    Gibbs, B. P.; Estes, R. H.

    1981-01-01

    The results of a preliminary study to determine the feasibility of using Kalman filter techniques for geomagnetic field modeling are given. Specifically, five separate field models were computed using observatory annual means, satellite, survey and airborne data for the years 1950 to 1976. Each of the individual field models used approximately five years of data. These five models were combined using a recursive information filter (a Kalman filter written in terms of information matrices rather than covariance matrices.) The resulting estimate of the geomagnetic field and its secular variation was propogated four years past the data to the time of the MAGSAT data. The accuracy with which this field model matched the MAGSAT data was evaluated by comparisons with predictions from other pre-MAGSAT field models. The field estimate obtained by recursive estimation was found to be superior to all other models.

  10. Free core nutation and geomagnetic jerks

    NASA Astrophysics Data System (ADS)

    Malkin, Z.

    2013-12-01

    Variations in free core nutation (FCN) are associated with different processes in the Earth's fluid core and core-mantle coupling. The same processes are generally caused the variations in the geomagnetic field (GMF) particularly the geomagnetic jerks (GMJs), which are rapid changes in GMF secular variations. Therefore, the joint investigation of variations in FCN and GMF can elucidate the Earth's interior and dynamics. In this paper, we investigated the FCN amplitude and phase variations derived from VLBI observations. Comparison of the epochs of the changes in the FCN amplitude and phase with the epochs of the GMJs indicated that the observed extremes in the FCN amplitude and phase variations were closely related to the GMJ epochs. In particular, the FCN amplitude begins to grow one to three years after the GMJs. Thus, processes that cause GMJs are assumed as sources of FCN excitation.

  11. Recent Developments in Paleomagnetism and Geomagnetism

    NASA Astrophysics Data System (ADS)

    Elming, S.-Å.; Pesonen, L. J.

    2009-12-01

    Sixth Nordic Paleomagnetic Workshop; Luleå, Sweden, 15-22 September 2009; The Sixth Nordic Paleomagnetic Workshop was held in northern Sweden. The meeting focused on discussion of recent developments in paleomagnetism/geomagnetism, covering topics including thousand-year-scale geomagnetic field variations, paleoclimate of the Holocene (˜10,000 years ago to the present), Phanerozoic (˜545 million years ago to the present) plate reconstructions, and Precambrian (more than ˜545 million years ago) supercontinents. The workshop series began in 1986 in Espoo, Finland, in connection with the European Geotraverse Project. Since then, workshops have occurred every 4-5 years: the second in Sweden (1990), the third in Norway (1994), the fourth in Denmark (1999), and the fifth in Finland (2005). A total of 23 paleomagnetists and geomagnetists representing 12 countries (Australia, Brazil, Canada, Denmark, Estonia, India, Finland, Norway, Switzerland, Sweden, United Kingdom, and United States) participated in the sixth workshop.

  12. Short-term forecasting regional model to predict M(3000)F2 over the European sector: Comparisons with the IRI model during moderate, disturbed, and very disturbed geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Pietrella, M.

    2014-07-01

    The hourly measurements of M(3000)F2 (M(3000)F2meas) and the hourly quiet-time values of M(3000)F2 (M(3000)F2QT) relative to the ionospheric observatories of Poitiers, Lannion, Dourbes, Slough, Rome, Juliusruh, Kaliningrad, Uppsala, Lyckesele, Sodankyla, and Kiruna as well as the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap (ap(?), were considered during the period January 1957-December 2003 and used for the development of 11 short-term forecasting local models (STFLM) of M(3000)F2. Under the assumption that the ionospheric disturbance index ln(M(3000)F2meas/M(3000)F2QT) is correlated to the integrated geomagnetic index ap(?), a set of regression coefficients were established over 12 months and 24 h for each of the 11 observatories under consideration and used as input to calculate the short-term ionospheric forecasting of M(3000)F2 for three different ranges of geomagnetic activity. The 11 short-term forecasting local models all together constitute a single short-term forecasting regional model (STFRM) of M(3000)F2. The monthly median predictions of M(3000)F2 provided by the IRI model at the 11 local stations were used to make some comparisons with the predictions of M(3000)F2 carried out by the STFRM. The results showed that: (1) under moderate geomagnetic activity there are no significantly differences between STFRM and IRI performance because quiet geomagnetic conditions are not so diverse from moderate geomagnetic conditions; (2) under disturbed geomagnetic activity, performances of STFRM significantly better than IRI emerge only in some cases; (3) the STFRM's performances are always significantly better than those provided by IRI under very disturbed geomagnetic activity, consequently the operative use of the STFRM could be valuable in providing short-term forecasting maps of M(3000)F2 over the European area during very disturbed geomagnetic conditions.

  13. OI 630.0 nm Night Airglow Observations during the Geomagnetic Storm on November 20, 2003 at Kolhapur (P43)

    NASA Astrophysics Data System (ADS)

    Sharma, A. K.; et al.

    2006-11-01

    sharma_ashokkumar@yahoo.com The ground based photometric observations of OI 630 nm emission line have been carried out from Kolhapur station (Geog. Lat.16.8˚N, Geo. Long 74.2˚E), India during the period of the largest geomagnetic storm of the solar cycle 23 which occurred on 20 November 2003, with minimum Dst index 472 nT occurring around mid-night hours. We observed that on 19 November 2003 which was geomagnetically quiet day, the airglow activity of OI 630 nm emission was subdued and it was decreasing monotonically. However, on the night of November 20, 2003 the enhancement is observed during geomagnetic storm due to the increased electron density at the altitude of the F region which is related to the downward transport of electron from the plasmasphere to the F-region. Airglow intensity at OI 630.0 nm showed increase around midnight on November 21, 2003 but comparatively on a smaller scale. On this night the DST index was about 100 nT. This implies that the effect of the geomagnetic storm persisted on that night also. These observations have been explained by the penetration magnetospheric electric field to the low latitude region and the subsequent modulation of meridional wind during the magnetic disturbance at night.

  14. Local time dependent response of postsunset ESF during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Rama Rao, P. V. S.; Prasad, D. S. V. V. D.; Niranjan, K.; Gopi Krishna, S.; Sridharan, R.; Ravindran, Sudha

    2008-07-01

    Development or inhibition of ESF during magnetically active periods has been an important space weather topic of interest during the recent past in view of its applications in the satellite based navigational systems. Particularly, the postsunset period exhibits significant variability for storm time development of ESF versus longitude. In this paper, we report the results of a multi-instrumental (ground based and space-borne) and multistation study on the development/inhibition of postsunset ESF during five moderate to intense geomagnetic storms occurred during the low and descending phase of the solar activity period, 2004-2006. It has been observed that, the prompt penetration of eastward electric fields into low latitudes and subsequent development of ESF occurred in all longitudinal sectors where the local time corresponds to postsunset hours during the entire main phase of the storm. In this paper, we show the development of plasma bubble irregularities over a wide longitudinal extent of 92° owing to the dusk time penetration of eastward electric fields into low latitudes. Either the sudden increase in AE-index and/or a marked decrease in Sym-H index may be used as proxies to determine the occurrence as well as the time of penetration of electric fields into equatorial and low latitudes. However, in such cases where the AE-index does not represent any sudden increase, the dSymH/dt seems to be the better index to determine the time of penetration. In this paper, is also presented an interesting case where the prompt penetration eastward electric fields dominated the existing strong westward electric fields and subsequently caused the onset of spread-F and scintillations at both VHF (244 MHz) as well as L-band (1.5 GHz) frequencies.

  15. MAGSAT for geomagnetic studies over Indian region

    NASA Technical Reports Server (NTRS)

    Rastogi, R. G.; Bhargava, B. N.; Singh, B. P.; Rao, D. R. K.; Rangarajan, G. K.; Rajaram, R.; Roy, M.; Arora, B. R.; Seth, A. (principal investigators)

    1981-01-01

    Progress in the preparation of software for converting data tapes produced on an IBM system to data readable on a DEC-10 system, in the creation of awareness of the utility of MAGSAT data among users in India, and in making computer programs supplied by NASA operational on the DEC-10 system is reported. Papers presented to Indian users, at the IAGA fourth scientific assembly, at a symposium on interdisciplinary approaches to geomagnetism, and a paper published in Science Today are included.

  16. NOAA Plans for Geomagnetic Storm Observations

    NASA Astrophysics Data System (ADS)

    Diedrich, B. L.; Biesecker, D. A.; Mulligan, P.; Simpson, M.

    2012-12-01

    For many years, NOAA has issued geomagnetic storm watches and warnings based on coronal mass ejection (CME) imagery and in-situ solar wind measurements from research satellites. The NOAA Satellite and Information Service (NESDIS) recognizes the importance of this service to protecting technological infrastructure including power grids, polar air travel, and satellite navigation, so is actively planning to replace these assets to ensure their continued availability. NOAA, NASA, and the US Air Force are working on launching the first operational solar wind mission in 2014, the Deep Space Climate Observatory (DSCOVR), to follow NASA's Advanced Composition Explorer (ACE) in making solar wind measurements at the sun-Earth L1 for 15-60 minute geomagnetic storm warning. For continuing operations after the DSCOVR mission, one technology NOAA is looking at is solar sails that could greatly improve the lead time of geomagnetic storm warnings by stationkeeping closer to the sun than L1. We are working with NASA and private industry on the Sunjammer solar sail demonstration mission to test making solar wind measurements from a solar sail in the sun-Earth L1 region. NOAA uses CME imagery from the NASA/ESA Solar and Heliospheric Observatory (SOHO) and the NASA Solar Terrestrial Relations Observatory (STEREO) satellites to issue 1-3 day geomagnetic storm watches. For the future, NOAA worked with the Naval Research Laboratory (NRL) to develop a Compact Coronagraph (CCOR) through Phase A, and is studying ways to complete instrument development and test fly it for use in the future.

  17. Domino model for geomagnetic field reversals.

    PubMed

    Mori, N; Schmitt, D; Wicht, J; Ferriz-Mas, A; Mouri, H; Nakamichi, A; Morikawa, M

    2013-01-01

    We solve the equations of motion of a one-dimensional planar Heisenberg (or Vaks-Larkin) model consisting of a system of interacting macrospins aligned along a ring. Each spin has unit length and is described by its angle with respect to the rotational axis. The orientation of the spins can vary in time due to spin-spin interaction and random forcing. We statistically describe the behavior of the sum of all spins for different parameters. The term "domino model" in the title refers to the interaction among the spins. We compare the model results with geomagnetic field reversals and dynamo simulations and find strikingly similar behavior. The aggregate of all spins keeps the same direction for a long time and, once in a while, begins flipping to change the orientation by almost 180 degrees (mimicking a geomagnetic reversal) or to move back to the original direction (mimicking an excursion). Most of the time the spins are aligned or antialigned and deviate only slightly with respect to the rotational axis (mimicking the secular variation of the geomagnetic pole with respect to the geographic pole). Reversals are fast compared to the times in between and they occur at random times, both in the model and in the case of the Earth's magnetic field. PMID:23410284

  18. Why utilities respect geomagnetically induced currents

    NASA Astrophysics Data System (ADS)

    Molinski, Tom S.

    2002-11-01

    It has been well known for more than 50 years that electric utilities in northern latitudes can have geomagnetically induced currents (GICs) flowing in their transmission lines and transformer ground points, and that these are caused by geomagnetic storms. Initially, these GICs were considered harmless and very little attention was paid to them. However, in the last 40 years it was realized that large GICs can flow in power systems and become problematic and even severe enough to cause a complete system shutdown. Utilities susceptible to GIC do not expect to rely on luck that the geomagnetic storm will not affect them, or if it does, the loading conditions at the time will allow enough margin to ride through it. This is precisely why many utilities today are studying the cause, effect, and mitigation of GICs and why utilities respect GICs. This paper presents a detailed discussion on how electric utilities are affected by GICs and what can be accomplished to mitigate the harmful effects.

  19. Drift shell splitting by internal geomagnetic multipoles.

    NASA Technical Reports Server (NTRS)

    Roederer, J. G.; Hilton, H. H.; Schulz, M.

    1973-01-01

    Computations on an 80-coefficient model of the earth's field illustrate the 'topography' of the magnetic equatorial surface and the geometry of the drift shells of geomagnetically trapped particles. Individual terms in the spherical harmonic expansion of the geomagnetic scalar potential V(r, theta, phi) are either even or odd in cos theta, where theta = 90 deg denotes the dipole equator. Terms that are even in cos theta tend to 'warp' the equatorial surface, but do not (in first order) distort particle drift shells radially nor split the drift shells of particles having different equatorial pitch angles. Azimuthally asymmetric terms that are odd in cos theta do cause shell splitting in first order. Shell splitting at large L values (neglecting deformation of the earth's field by the solar wind) is found to be dominated by the geomagnetic octupole. At L approximately equal to 1, shell splitting is strongly enhanced by the South American and South African anomalies. When combined with pitch angle diffusion caused by atmospheric scattering, these results may be able to account for anomalous radial diffusion of inner zone electrons.

  20. Disturbances in the US electric grid associated with geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Schrijver, Carolus J.; Mitchell, Sarah D.

    2013-05-01

    Large solar explosions are responsible for space weather that can impact technological infrastructure on and around Earth. Here, we apply a retrospective cohort exposure analysis to quantify the impacts of geomagnetic activity on the US electric power grid for the period from 1992 through 2010. We find, with more than 3? significance, that approximately 4% of the disturbances in the US power grid reported to the US Department of Energy are attributable to strong geomagnetic activity and its associated geomagnetically induced currents.

  1. Geomagnetic effects on cosmic ray propagation for different conditions

    NASA Astrophysics Data System (ADS)

    Masas-Meza, Jimmy J.; Bertou, Xavier; Dasso, Sergio

    2012-07-01

    The geomagnetic field (Bgeo ) sets a lower cutoff rigidity (Rc ) to the entry of cosmic particles to Earth which depends on the geomagnetic activity. From numerical simulations of the trajectory of a proton (performed with the MAGCOS code) in the Bgeo , we use backtracking to analyze particles arriving at the Auger Observatory location. We determine the asymptotic trajectories and the values of Rc in different incidence directions. Simulations were done using several models of Bgeo that emulate different geomagnetic conditions.

  2. Study of the recovery phase of the extreme geomagnetic storms from 1859 to 1989

    NASA Astrophysics Data System (ADS)

    Saiz, Elena; Cid, Consuelo; Palacios, Judith; Aguado, Jesus; Cerrato, Yolanda; Guerrero, Antonio

    2013-04-01

    The Dst index is used as a proxy of energy ring current content. In a storm event, the enhancement of the current appears as a depression of the index. To know in advance the minimum value that will reach the index and the time in which it will happen are usually the main aims in the forecasting scheme. However, the knowledge of the time remaining for the magnetosphere to reach again quiet time, or at least 'non-dangerous time' is an important input for many technological systems. These predictions are even more relevant for severe geomagnetic storms. In a previous study, we analyzed the recovery phase of intense geomagnetic storms (Dst ? - 100 nT) in the period 1963-2003 [Aguado et al., 2010]. The results obtained showed that the decay of the Dst index follows a hyperbolic law, which recovery time depends linearly on the intensity of the storm. Now, we study the recovery phase of the largest storms even recorded [Tsurutani et al., 2003]. These events provide an extraordinary opportunity for two goals: (1) to validate the hyperbolic model for disturbances at terrestrial surface as severe as the Carrington event, or that related to the Hydro-Quebec blackout, and (2) to check if the linear relationship between the recovery time and the intensity of the storm still remains.

  3. Geomagnetic field models incorporating physical constraints on the secular variation

    NASA Technical Reports Server (NTRS)

    Constable, Catherine; Parker, Robert L.

    1993-01-01

    This proposal has been concerned with methods for constructing geomagnetic field models that incorporate physical constraints on the secular variation. The principle goal that has been accomplished is the development of flexible algorithms designed to test whether the frozen flux approximation is adequate to describe the available geomagnetic data and their secular variation throughout this century. These have been applied to geomagnetic data from both the early and middle part of this century and convincingly demonstrate that there is no need to invoke violations of the frozen flux hypothesis in order to satisfy the available geomagnetic data.

  4. Geomagnetic effects modelling for the PJM interconnection system. Part 2; Geomagnetically induced current study results

    SciTech Connect

    Prabhakara, F.S.; Hannett, L.N.; Ringlee, R.J. ); Ponder, J.Z. )

    1992-05-01

    The development of a computer program for calculation of geomagnetically induced current (GIC) and a GIC power system model for the Pennsylvania-New Jersey-Maryland Interconnection is described in this paper. Results of GIC for three different ionospheric source configurations are shown. A new method is presented for estimating GIC in unmetered parts of the system based on a few measurements and precalculated geomagnetic disturbance conditions. The use of an interactive, menu driven GIC program to study mitigation concepts including the effects of line outages, line series capacitors, transformer neutral blocking resistors and transformer neutral blocking capacitors is also presented.

  5. CIRA Solar Irradiances and Solar/Geomagnetic Indices

    NASA Astrophysics Data System (ADS)

    Tobiska, W. Kent

    Solar and geomagnetic inputs are required for use in empirical thermospheric density models. The constituent species in the thermosphere absorb spectrally resolved solar irradiances from soft X-ray (XUV) to Far Ultraviolet (FUV) wavelengths which deposit their energy at varying optical depths. In the high latitude regions, Joule heating and particle precipitation contribute secondary heating, which can be transported to lower latitudes by meridional winds. However, empirical models generally do not use the sophistication of spectrally resolved solar irradiances or Joule heating and particle precipitation. Instead, simplification of an energy input is accomplished in the form solar and geomagnetic surrogates, i.e., proxies and indices. A proxy is a substitute for a distinctly different energy input while an index expresses the activity level of an energy input. Recently, in addition to the traditional 10.7-cm flux (F10.7) that is a proxy for solar Extreme Ultraviolet (EUV) irradiances, a new solar irradiance index (S10.7) and a new proxy (M10.7) have been developed for use in empirical thermospheric density models. These three solar indices and proxies best represent the complex interaction between the solar emission source (photosphere, chromosphere, corona) with the irradiances' penetration into the thermosphere (unit optical depth in the middle and lower thermosphere) and the length of time for energy transfer between thermospheric layers (thermal process of molecular conduction or kinetic process of molecular diffusion). The S10.7 index (previously called SEUV) accounts for the majority of the daily density variability with a 1-day lag, is reported in units of F10.7, is the chromospheric EUV energy between 26-34 nm as measured by the SOHO SEM instrument, and is deposited above 200 km. The M10.7 proxy accounts for the next significant factor of the daily density variability with a 5-day lag and is the Mg II core-to-wing ratio reported in units of F10.7. It is used as a substitute for the FUV Schumann-Runge Continuum (SRC) energy dominated by the 145-165 nm range that has a unit optical depth in the lower thermosphere and is the main source of thermospheric molecular oxygen dissociation that is not historically included in Jacchiaand MSIS-type models. The F10.7 proxy accounts for a minority of the daily density variability with a 1-day lag and represents the transition region/coronal XUV/EUV energy less than 121 nm with a unit optical depth throughout the thermosphere. We describe the use of these three solar irradiance indices and proxies in research and operational empirical thermospheric density models. We also describe the use of Ap and Dst geomagnetic indices as applied to thermospheric density modeling.

  6. NM-MT network and space dangerous phenomena, 2. Examples of cosmic ray using for forecasting of major geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Belov, A.; Dorman, L.; Eroshenko, E.; Iucci, N.; Parisi, M.; Pustil Nik, L.; Sternlieb, A.; Villoresi, G.; Yanke, V.; Zukerman, I.

    We present developing of methods (e.g., Dorman et al., 1995, 1999) for forecasting on the basis of neutron monitor hourly on-line data (as well as on-line muon telescopes hourly data from different directions) geomagnetic storms of scales G5 (3- hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) (according to NOAA Space Weather Scales). These geomagnetic storms are dangerous for people technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others). We show that for especially dangerous geomagnetic storms can be used global-spectrographic method if on-line will be available 35-40 NM and muon telescopes. In this case for each hour can be determined CR anisotropy vector, and the specifically behavior of this vector before SC of geomagnetic storms G5, G4 or G3 (according to NOAA Space Weather Scales) can be used as important factor for forecast. The second factor what can be used for SC forecast is specifically behavior of CR density (CR intensity) for about 30-15 hours before SC (caused mainly by galactic CR particles acceleration during interaction with shock wave moved from the Sun). The third factor is effect of cosmic ray pre-decreasing, caused by magnetic connection of the Earth with the region behind the shock wave. We demonstrate developing methods on several examples of major geomagnetic storms. This research is partly supported by the INTAS grant 00-0810. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, 49A, 136-144 (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their prediction", Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, 6, 476-479 (1999).

  7. Laboratory Astrophysics Division of the AAS (LAD)

    NASA Technical Reports Server (NTRS)

    Salama, Farid; Drake, R. P.; Federman, S. R.; Haxton, W. C.; Savin, D. W.

    2012-01-01

    The purpose of the Laboratory Astrophysics Division (LAD) is to advance our understanding of the Universe through the promotion of fundamental theoretical and experimental research into the underlying processes that drive the Cosmos. LAD represents all areas of astrophysics and planetary sciences. The first new AAS Division in more than 30 years, the LAD traces its history back to the recommendation from the scientific community via the White Paper from the 2006 NASA-sponsored Laboratory Astrophysics Workshop. This recommendation was endorsed by the Astronomy and Astrophysics Advisory Committee (AAAC), which advises the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA), and the U.S. Department of Energy (DOE) on selected issues within the fields of astronomy and astrophysics that are of mutual interest and concern to the agencies. In January 2007, at the 209th AAS meeting, the AAS Council set up a Steering Committee to formulate Bylaws for a Working Group on Laboratory Astrophysics (WGLA). The AAS Council formally established the WGLA with a five-year mandate in May 2007, at the 210th AAS meeting. From 2008 through 2012, the WGLA annually sponsored Meetings in-a-Meeting at the AAS Summer Meetings. In May 2011, at the 218th AAS meeting, the AAS Council voted to convert the WGLA, at the end of its mandate, into a Division of the AAS and requested draft Bylaws from the Steering Committee. In January 2012, at the 219th AAS Meeting, the AAS Council formally approved the Bylaws and the creation of the LAD. The inaugural gathering and the first business meeting of the LAD were held at the 220th AAS meeting in Anchorage in June 2012. You can learn more about LAD by visiting its website at http://lad.aas.org/ and by subscribing to its mailing list.

  8. Laboratory Astrophysics Division of The AAS (LAD)

    NASA Astrophysics Data System (ADS)

    Salama, Farid; Drake, R. P.; Federman, S. R.; Haxton, W. C.; Savin, D. W.

    2012-10-01

    The purpose of the Laboratory Astrophysics Division (LAD) is to advance our understanding of the Universe through the promotion of fundamental theoretical and experimental research into the underlying processes that drive the Cosmos. LAD represents all areas of astrophysics and planetary sciences. The first new AAS Division in more than 30 years, the LAD traces its history back to the recommendation from the scientific community via the White Paper from the 2006 NASA-sponsored Laboratory Astrophysics Workshop. This recommendation was endorsed by the Astronomy and Astrophysics Advisory Committee (AAAC), which advises the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA), and the U.S. Department of Energy (DOE) on selected issues within the fields of astronomy and astrophysics that are of mutual interest and concern to the agencies. In January 2007, at the 209th AAS meeting, the AAS Council set up a Steering Committee to formulate Bylaws for a Working Group on Laboratory Astrophysics (WGLA). The AAS Council formally established the WGLA with a five-year mandate in May 2007, at the 210th AAS meeting. From 2008 through 2012, the WGLA annually sponsored Meetings in-a-Meeting at the AAS Summer Meetings. In May 2011, at the 218th AAS meeting, the AAS Council voted to convert the WGLA, at the end of its mandate, into a Division of the AAS and requested draft Bylaws from the Steering Committee. In January 2012, at the 219th AAS Meeting, the AAS Council formally approved the Bylaws and the creation of the LAD. The inaugural gathering and the first business meeting of the LAD were held at the 220th AAS meeting in Anchorage in June 2012. You can learn more about LAD by visiting its website at http://lad.aas.org/ and by subscribing to its mailing list.

  9. The Microjet of AA Tau

    NASA Astrophysics Data System (ADS)

    Cox, A. W.; Hilton, G. M.; Williger, G. M.; Grady, C. A.; Woodgate, B.

    2005-12-01

    The microjet of AA Tau A.W. Cox (Atholton High School, Columbia MD), G.M. Hilton (SSAI and GSFC), G.M. Williger (JHU and U. Louisville), C.A. Grady (Eureka Scientific and GSFC) B.Woodgate (NASA's GSFC) AA Tau is a classical T Tauri star with a spatially resolved disk viewed at approximately 70 degrees from pole-on. Photo-polarimetric variability of the star has been interpreted as being caused by the stellar magnetic field being inclined at 30 degrees with respect to the stellar rotation axis, producing a warp in the inner disk. Under these conditions, any jet should be less collimated than typical of T Tauri microjets, and should show signs of the jet axis precessing around the stellar rotation axis. When compared with the microjets imaged in the HST/STIS coronagraphic imaging survey, the AA Tau jet has an opening half-angle of approximately 10-15 degrees rather than the 3-5 degrees typical of the other T Tauri stars which have been coronagraphically imaged by HST/STIS. Using the HST data with ultra-narrowband imagery and long slit spectroscopy obtained with the Goddard Fabry-Perot and the Dual Imaging Spectrograph at the Apache Point Observatory 3.5m telescope, we derive the jet inclination, knot ejection epochs, and ejection frequency. We also compare the jet opening angle with model predictions. Apache Point Observatory observations with the Goddard Fabry-Perot were made through a grant of Director's Discretionary Time. Apache Point Observatory is operated by the Astrophysical Research Consortium. The GFP was supported under NASA RTOP 51-188-01-22 to GSFC. Grady is supported under NASA contract NNH05CD30C to Eureka Scientific.

  10. Statistical Analysis of TEC Enhancements during Geomagnetic Disturbances in Extreme Solar Conditions

    NASA Astrophysics Data System (ADS)

    Su, F.

    2014-12-01

    In the past decades, a remarkable set of comprehensive studies and review articles enriched theresearch of the Earth's ionospheric response to geomagnetic disturbances[Prolss, 1995; Buonsanto,1999; Mendillo, 2006]. However, comparative studies of TEC response during geomagnetic disturbances in solar minimum and solar maximum have not been reported yet. Here we present some new results of TEC enhancements during geomagnetic disturbancesin extreme solar maximum and deep solar minimum. The JPL TEC maps from 12/01/2000 to 12/31/2003 during high solar activity and from 01/01/2007 to 12/31/2010 during low solar activity are used. The deviation of TEC is defined as the differences between TEC and TECq, which represents the 27-day sliding smooth median. The geomagnetic disturbances selected have peaks of geomagnetic index Ap>20. We found that the winter anomaly appears in both extreme solar cycle conditions and has longer-lived patterns than other seasons.The nighttime enhancement is more significant in solar maximum than solar minimum. The mean duration of TEC enhancements is longer in solar minimum than solar maximum. The mean delay at the beginning of positive anomaly responds fastest at around 1500 LT and slowest at around midnight during solar minimum.The mean intensity of enhancements is stronger at higher latitudes and weaker at lower latitudes, and the mean delay is smaller at higher latitudes and larger at lower latitudes in both extreme solar cycle conditions. Acknowledgments: Thiswork was supportedby the National Natural Science Foundation of China under Grants 41204107. We thank JPL and Word Data Center for Geomagnetism at Kyoto University for making available the data. Prolss, G. W., Ionospheric F region storms, in Handbook of Atmospheric Electrodynamics, vol. 2, edited by H. Volland, pp. 195 - 248, CRC Press,Boca Raton, Fla., 1995. Buonsanto, M., Ionospheric storm: A review,Space Science Review, vol. 88, pp. 563 - 601, 1999. Mendillo, M.: Storms in the ionosphere: Patterns and processes for total electron content, Rev. Geophys., 44, RG4001, 2006..

  11. Geomagnetic storm effects in the ionospheric E- and F-regions

    NASA Astrophysics Data System (ADS)

    Gordienko, G. I.; Vodyannikov, V. V.; Yakovets, A. F.

    2011-08-01

    Ground-based ionosonde data obtained at Alma-Ata station [φ=43.25°N, λ=76.92°E, Φ=33.47°N, L=1.44) were analysed to study the ionospheric responses of nine intense (Kp≥8, Dst<-100 nT) geomagnetic storms with storm sudden commencement (ssc). The collected data show that the ionospheric responses to the geomagnetic storms are highly complex and variable; however, negative ionospheric disturbances are a common feature of the responses. The occurrence of normal night E2-, E-, F1- and auroral type r (retardation) sporadic Es-layers, which are unusual for Alma-Ata, was observed during most active phase in the Dst index. Employing the International Reference Ionosphere (IRI), the night-time E region electron density Ne was estimated for “quiet” conditions on the epochs of the storm time periods. A direct comparison of the “quiet” and “storm” electron density in the 110-200 km altitude range shows a significant storm-induced increase in Ne that reaches a factor of approximately 10 at the 110 km altitude. The interaction of precipitating energetic neutralised ring current particles with the upper atmosphere during geomagnetic disturbances is assumed to be a possible explanation for the observed night events at this latitude sector.

  12. Predicting geomagnetic storms from solar-wind data using time-delay neural networks

    NASA Astrophysics Data System (ADS)

    Gleisner, H.; Lundstedt, H.; Wintoft, P.

    1996-07-01

    We have used time-delay feed-forward neural networks to compute the geomagnetic-activity index Dst one hour ahead from a temporal sequence of solar-wind data. The input data include solar-wind density n, velocity V and the southward component Bz of the interplanetary magnetic field. Dst is not included in the input data. The networks implement an explicit functional relationship between the solar wind and the geomagnetic disturbance, including both direct and time-delayed non-linear relations. In this study we especially consider the influence of varying the temporal size of the input-data sequence. The networks are trained on data covering 6600 h, and tested on data covering 2100 h. It is found that the initial and main phases of geomagnetic storms are well predicted, almost independent of the length of the input-data sequence. However, to predict the recovery phase, we have to use up to 20 h of solar-wind input data. The recovery phase is mainly governed by the ring-current loss processes, and is very much dependent on the ring-current history, and thus also the solar-wind history. With due consideration of the time history when optimizing the networks, we can reproduce 84% of the Dst variance.

  13. Transmission of systemic AA amyloidosis in animals.

    PubMed

    Murakami, T; Ishiguro, N; Higuchi, K

    2014-03-01

    Amyloidoses are a group of protein-misfolding disorders that are characterized by the deposition of amyloid fibrils in organs and/or tissues. In reactive amyloid A (AA) amyloidosis, serum AA (SAA) protein forms deposits in mice, domestic and wild animals, and humans that experience chronic inflammation. AA amyloid fibrils are abnormal ?-sheet-rich forms of the serum precursor SAA, with conformational changes that promote fibril formation. Extracellular deposition of amyloid fibrils causes disease in affected animals. Recent findings suggest that AA amyloidosis could be transmissible. Similar to the pathogenesis of transmissible prion diseases, amyloid fibrils induce a seeding-nucleation process that may lead to development of AA amyloidosis. We review studies of possible transmission in bovine, avian, mouse, and cheetah AA amyloidosis. PMID:24280941

  14. Indexing Images.

    ERIC Educational Resources Information Center

    Rasmussen, Edie M.

    1997-01-01

    Focuses on access to digital image collections by means of manual and automatic indexing. Contains six sections: (1) Studies of Image Systems and their Use; (2) Approaches to Indexing Images; (3) Image Attributes; (4) Concept-Based Indexing; (5) Content-Based Indexing; and (6) Browsing in Image Retrieval. Contains 105 references. (AEF)

  15. Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field

    USGS Publications Warehouse

    Peddie, N.W.

    1992-01-01

    The secular variation of the main geomagnetic field during the periods 1980-1985 and 1985-1990 was analyzed in terms of spherical harmonics up to the eighth degree and order. Data from worldwide magnetic observatories and the Navy's Project MAGNET aerial surveys were used. The resulting pair of secular-variation models was used to update the Definitive Geomagnetic Reference Field (DGRF) model for 1980, resulting in new mainfield models for 1985.0 and 1990.0. These, along with the secular-variation model for 1985-1990, were proposed for the 1991 revision of the International Geomagnetic Reference Field (IGRF). -Author

  16. Historical variation of the geomagnetic axial dipole

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher C.

    2008-09-01

    The geomagnetic axial dipole (hereinafter denoted g10) is the largest component of our planet's magnetic field. Its magnitude determines the morphology of solar-terrestrial electrical current systems and it is the most fundamental diagnostic property of the core-generated geodynamo. Elucidating past and future variations of g10(t) is consequently of central importance in geomagnetism. Previous historical geomagnetic field models, such as gufm1 of Jackson et al. [Jackson, A., Jonkers, A.R.T., Walker, M.R., 2000. Four centuries of geomagnetic secular variation from historical records. Philos. Trans. R. Soc. Lond. A 358, 957-990], used direct observations to constrain g10(t) only after 1840 A.D.; before this time a crude linear extrapolation of the post-1840 A.D. rate of change (15 nT/year) was employed. In this contribution I construct historical field models with g10(t) instead constrained from 1590 A.D. to 1840 A.D. by an archaeointensity dataset compiled by Korte et al. [Korte, M., Genevey, A., Constable, C.G., Frank, U., Schnepp, E., 2005. Continuous geomagnetic field models for the past 7 millennia. 1. A new global data compilation. Geochem. Geophys. Geosyst. 6, doi:10.1029/2004GC000800]. A range of possible linear models of the form g10(t)=g10(1840)+β(t-1840) are first explored; β=2.74±42.32 nT/year is found to explain the archaeointensity dataset with maximum likelihood, consistent with the recent findings of Gubbins et al. [Gubbins, D., Jones, A.L., Finlay, C.C., 2006. Fall in Earth's magnetic field is erratic. Science 312, 900-902]. Relaxing the linear constraint in an effort to find more physically plausible models, I find it is necessary to artificially increase the weight given to the archaeointensity data in order to obtain acceptable models. Despite satisfactorily explaining both the historical and archaeointensity data, and possessing reasonable spatial and temporal complexity, such free evolution models perform worse than the simpler linearly constrained models when tested against the independent dataset of Gallet et al. [Gallet, Y., Genevey, A., Fluteau, F., 2005. Does Earth's magnetic field secular variation control centennial climate change? Earth Plan. Sci. Lett. 236, 159-173]. Bayesian model comparison techniques indicate that a model ( gufm1-g10c) involving no change in g10(t) between 1590 A.D. and 1840 A.D. is most probable given the presently available data and current modelling techniques. I propose that this new, empirically derived, constraint on the evolution of the geomagnetic axial dipole be incorporated into the next generation of historical field models.

  17. Geomagnetic field effect on cardiovascular regulation.

    PubMed

    Gmitrov, Juraj; Gmitrova, Anna

    2004-02-01

    The goal of the present research was try to explain the physiological mechanism for the influence of the geomagnetic field (GMF) disturbance, reflected by the indices of the geomagnetic activity (K, K(p), A(k), and A(p) indices), on cardiovascular regulation. One hundred forty three experimental runs (one daily) comprising 50 min hemodynamic monitoring sequences were carried out in rabbits sedated by pentobarbital infusion (5 mg/kg/h). We examined the arterial baroreflex effects on the short term blood pressure and heart rate (HR) variabilities reflected by the standard deviation (SD) of the average values of the mean femoral arterial blood pressure (MAP) and the HR. Baroreflex sensitivity (BRS) was estimated from blood pressure/HR response to intravenous (i.v.) bolus injections of vasoconstrictor (phenylephrine) and vasodilator (nitroprusside) drugs. We found a significant negative correlation of increasing GMF disturbance (K(p)) with BRS (P = 0.008), HR SD (P =0.022), and MAP SD (P = 0.002) signifying the involvement of the arterial baroreflex mechanism. The abrupt change in geomagnetic disturbance from low (K = 0) to high (K = 4-5) values was associated with a significant increase in MAP (83 +/- 5 vs. 99 +/- 5 mm Hg, P = 0.045) and myocardial oxygen consumption, measured by MAP and HR product (24100 +/- 1800 vs. 31000 +/- 2500 mm Hg. bpm, P = 0.034), comprising an additional cardiovascular risk. Most likely, GMF affects brainstem and higher neural cardiovascular regulatory centers modulating blood pressure and HR variabilities associated with the arterial baroreflex. PMID:14735558

  18. Some data about the relationship between ths human state and external perturbations of geomagnetic field

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.; Stoilova, I.; Yanev, T.

    The influence of solar activity changes and related to them geomagnetic field variations on human health is confirmed in a lot of publications but the investigations in this area are still sporadic and incomplete because of the fact that it is difficult to separate the geomagnetic influence from the environmental factor complex, which influence the human life activity. That is why we have studied the influence of changes in geomagnetic activity on human physiological, psycho-physiological parameters and behavioural reactions. In this article we looked for influence of changes in GMA on the systolic and diastolic blood pressure and pulse-rate. We examined 54 volunteers. 26 persons of them had some cardio-vascular or blood pressure disturbances. The registrations were performed every day at one and the same time for each person during the period 1.10 - 10.11.2001. Four-way analysis of variance (MANOVA method) with factors: GMA, day, sex and cardiovascular pathology was performed. GMA was divided into four levels according to the Kp- and Ap-index values. The days examined were divided into six levels in relation to the day with increased GMA. Factor "cardiovascular pathology" was divided into two levels: healthy subjects and subjects that had some cardio -vascular or blood pressure disturbances. When we employed four-way analysis of variance, the influence of some of the factors on the physiological parameters examined turned out to be statistically significant at p<0.05. Our investigations indicate that most of the persons examined irrespectively to their status could be sensitive to the geomagnetic disturbances.

  19. Relationship between the Northern Hemisphere Joule heating and geomagnetic activity in the southern polar cap

    NASA Astrophysics Data System (ADS)

    Ballatore, P.; Lanzerotti, L. J.; Lu, G.; Knipp, D. J.

    2000-12-01

    One of the most important effects from the coupling of the solar wind to the magnetosphere-ionosphere system is the Joule heating (JH) of the atmosphere that is produced by the energy dissipation of ionospheric currents and geomagnetic field-aligned precipitating particles. At present, the most commonly used technique to estimate the global JH rate is the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. Here we describe a study of the relationship of the Northern Hemisphere JH and the Southern Hemisphere polar geomagnetic index AES-80 during a magnetic storm on October 18-23, 1995 (when both quantities are available). The purpose is to study the effects of the Northern-Southern Hemispherical asymmetry on the correlation between JH and geomagnetic indices. Our results confirm a higher contribution to JH from regions associated with eastward currents. Moreover, we find that the best correspondence between the northern JH and the AES-80 occurs during negative interplanetary magnetic field (IMF) Bz and By conditions. We discuss how this result is in agreement with the magnetospheric-ionospheric model that considers, during negative IMF Bz and By, an increase of conductance in the regions associated with eastward currents in the Northern Hemisphere. Our observations related to the best estimation of Southern Hemisphere JH are in agreement with the same model too. We also find a ``saturation'' effect for large values of northern JH: the JH-AES-80 correlation breaks down for intervals with JH>190gigawatt (GW), during the highest geomagnetic perturbations, and a negative IMF Bz that exceeds -20 nT. This ``saturation'' is in part attributed to the onset of hemispherical asymmetry due to the solar wind pressure with respect to the Earth-dipole orientation under severe storm conditions.

  20. Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation

    NASA Astrophysics Data System (ADS)

    Gmitrov, Juraj

    2007-03-01

    Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K p indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (ΔBRS with ΔMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow ( K-index with ΔMPPG; r s=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect.

  1. Geomagnetic field modulates artificial static magnetic field effect on arterial baroreflex and on microcirculation.

    PubMed

    Gmitrov, Juraj

    2007-03-01

    Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity, reflected by K and K ( p ) indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors. Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment in microvascular blood flow (DeltaBRS with DeltaMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted SMF-induced increment in microcirculatory blood flow (K-index with DeltaMPPG; r (s)=-0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial magnetic fields biological effect and should be taken into consideration in the assessment of the final effect. PMID:16983578

  2. Associations of geomagnetic activity with plasma sheet thinning and expansion: A statistical study

    SciTech Connect

    Hones,Jr., E.W.; Pytte, T.; West,Jr., H.I.

    1984-07-01

    Associations of geomagnetic activity in the auroral zone with thinnings and expansions of the magnetotail plasma sheet are examined statistically in this paper. We first identified many plasma sheet thinnings and expansions in plasma and particle data from VELA satellites and from OGO 5 without reference to the ground magnetic data. These events were grouped according to the location of the detecting satellite in the magnetotail. For each such group the times of thinning or expansion were then used as fiducial times in a superposed-epoch analysis of the geomagnetic AL index values that were recorded in 8-hour intervals centered on the event times. The results show that many plasma sheet thinnings and expansions are related to discrete negative bay structures that are the classical signature of substorms. Furthermore, they support earlier findings that plasma sheet thinning and expansion at the VELA orbit (rroughly-equal18 R/sub E/) tend to be associated with the onset of the auroral zone negative bay and the beginning of its subsidence, respectively. Earthward of rroughly-equal13-15 R/sub E/, plasma sheet expansion occurs near the time of the onset of the negative bay, again in agreement with earlier findings. A large fraction of plasma sheet expansions to half thicknesses of > or approx. =6 R/sub E/ at the VELA orbit are associated not with a baylike geomagnetic disturbance but with subsidence of a prolonged interval of disturbance. The study also shows that many plasma sheet expansions are related simply to generally enhanced geomagnetic activity showing no baylike or other distinctive features.

  3. The effect of precipitating particles on middle atmospheric night time ozone during enhanced geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Daae, M.; Espy, P. J.; Newnham, D.; Kleinknecht, N.; Clilverd, M.

    2010-12-01

    We have investigated the effect of precipitating particles on middle atmospheric ozone during a moderate geomagnetic storm in July 2009. It is expected that the number of precipitating particles increases with increasing geomagnetic activity, and that these precipitated particles will subsequently enhance the production of nitrosonium (NO+) and odd hydrogen (HOx) in the upper atmosphere. The lifetime of HOx and its associated ozone (O3) destruction is short, whilst NO+ can form long-lived odd nitrogen during times of high geomagnetic activity, (NOx), which can affect ozone over a longer time span, and hence a wider spatial range due to transport. We use the National Oceanic and Atmospheric Administration (NOAA) satellite data to identify and analyze the particles that precipitated over Antarctica during the moderate geomagnetic storm. To analyze the subsequent nitric oxide (NO) enhancement and O3 depletion we use a microwave radiometer stationed at Troll, Antarctica (72°S, 2.5°E, L=4.76). This microwave radiometer operating at 250 GHz gives high temporal and vertical resolution of the NO and O3 column. The Atmospheric Radiation Transfer Simulator (ARTS) and QPack have been employed to perform the inversions of the spectra. During the July storm that reached -79 nT on the Dst index, we observe radiation-belt particle precipitation over Troll, an NO increase, and a direct O3 depletion of 30% between 60 and 80 km altitude. This O3 depletion lasted for 9 days, and its centroid descended to 55 km altitude at a vertical velocity of 1-3 m/s. This work shows that moderate storms, which are common-place and occur even during solar minimum, can cause a significant and direct effect in the middle atmospheric ozone distribution.

  4. Search for correlation between geomagnetic disturbances and mortality

    NASA Technical Reports Server (NTRS)

    Lipa, B. J.; Barnes, C. W.; Sturrock, P. A.; Feinleib, M.; Rogot, E.

    1975-01-01

    Statistical evaluation of death rates in the U.S.A. from heart diseases or stroke did not show any correlation with measured geomagnetic pulsations and thus do not support a claimed relationship between geomagnetic activity and mortality rates to low frequency fluctuations of the earth's magnetic field.

  5. [Exacerbation of hypertension and disturbances of the geomagnetic field].

    PubMed

    Vershinina, N I; Petrochenko, N A; Shumilov, I S

    1997-01-01

    The authors consider relationships between emergence of acute episodes of essential hypertension (hospital admittances) and disturbance of the geomagnetic field. The authors report male- and female-specific ranges of the geomagnetic field variations which are threatening for hypertensive subjects. PMID:9229606

  6. Interplanetary magnetic field and geomagnetic Dst variations.

    NASA Technical Reports Server (NTRS)

    Patel, V. L.; Desai, U. D.

    1973-01-01

    The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

  7. Halo Coronal Mass Ejections and Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

    In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth. Key words: Coronal mass ejections, geomagnetic storms, geoeffectiveness, halo CMEs.

  8. Geophysical variables and behavior: C. Increased geomagnetic activity on days of commercial air crashes attributed to computer or pilot error but not mechanical failure.

    PubMed

    Fournier, N M; Persinger, M A

    2004-06-01

    Global geomagnetic activity (aa values) for the days of crashes of airplanes and for each of the three days before and after the crashes were compared for 373 events (years 1940 through 2002) attributed to unknown factors, mechanical errors, electronic/computer failures or pilot errors. Interactions between days and classifications of the crashes were due to the significantly greater geomagnetic activity on the days of crashes attributed to pilot or computer error but not to mechanical or unknown factors. Successive temporal analyses indicated that the elevated activity on the days of crashes attributed to pilot error have not changed over time, but there was an increase in those attributed to electronic errors after 1965. No more than 9% of the variance in geomagnetic activity on the days of the crashes was associated with the type of crash. These results are consistent with our hypothesis that some factor or factors associated with relative increases in geomagnetic activity may affect complex electronic systems composed of either silica (computer) or carbon (brain) aggregates. PMID:15291208

  9. Observed high-latitude GNSS disturbances during a less-than-minor geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Andalsvik, Y. L.; Jacobsen, K. S.

    2014-12-01

    This paper presents the effects of a weak geomagnetic storm event on 17 January 2013. While the Kp index reached a maximum of only 4, this event still caused severe disturbances for Global Navigation Satellite Systems (GNSS)-based positioning services at high latitudes. We present data from the Norwegian Mapping Authority's Real Time Ionospheric Monitor, based on a dense network of geodetic receivers and scintillation indices from scintillation receivers located in Norway. In northern parts of Norway, the centimeter positioning service was severely disturbed for hours. Service-monitoring measurements showed that the effect was significantly worse for a receiver far away from the nearest network reference station.

  10. The CM4 model prediction of ground variation of the geomagnetic diurnal field away from quiet time

    NASA Astrophysics Data System (ADS)

    Onovughe, Elvis; Holme, Richard

    2015-12-01

    We analyse the geomagnetic diurnal variation for days away from quiet time to see how well the comprehensive model (CM4) can reasonably predict ground variation of the diurnal field. To do this, we compared ground observatory hourly means to predictions given by the CM4 model for days away from quiet time. Our results show that, away from quiet time, the CM4 model is producing more reasonable predictions than expected, despite the lack of active data in the original model dataset. However, the CM4 model is not doing so well predicting short term features during period of rapid variations, especially for the X component of the geomagnetic diurnal variation field. When comparing the different modelled diurnal variation field maps of the CM4 model and the observatory data, our results show that the model to data fitness increases as we increase the spherical harmonic degrees. From our results we could see that the inability of the CM4 model to accurately predict the geomagnetic diurnal field for days away from quiet time, during time of rapid variations, may be due to the fact that the external field descriptions included in the CM4 model could not sufficiently explain the field contributions for days away from quiet time. This is seen in the low coherence, agreement and correlation in the comparison and cross correlation coefficient between the X component of the observatory data and the Dst index (which allows CM4 model to respond to active conditions outside of the original geomagnetic activity remit).

  11. Solar and Interplanetary Disturbances Causing Moderate Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Pratap Yadav, Mahendra; Kumar, Santosh

    2003-07-01

    The effect of solar and interplanetary disturbances on geomagnetospheric conditions leading to one hundred twenty one moderate geomagnetic storms (MGSs) with planetary index, Ap ? 20 and horizontal component of earth's magnetic field, H ? 250? have been investigated using solar geophysical data (SGD), solar wind plasma (SWP) and interplanetary magnetic field (IMF) data during the period 1978-99. It is observed statistically that 64%, 36%, MGSs have occurred during maximum and minimum phase of solar cycle 21st and 22nd respectively. Further, it is observed that H?, X-ray solar flares and active prominences and disapp earing filaments (APDFs) have occurred within lower helio latitude region associated with larger number of MGSs. No significant correlation between the intensity of GMSs and importance of H?, X-ray solar flares have been observed. Maximum number of MGSs are associated with solar flares of lower importance of solar flare faint (SF). The lower importance in association with some specific characteristics i.e. location, region, duration of occurrence of event may also cause MGSs. The correlation coefficient between MGSs and sunspot numbers (SSNs) using Karl Pearson method, has been obtained 0.37 during 1978-99.

  12. Multifunctional cellulolytic auxiliary activity protein HcAA10-2 from Hahella chejuensis enhances enzymatic hydrolysis of crystalline cellulose.

    PubMed

    Ghatge, Sunil S; Telke, Amar A; Waghmode, Tatoba R; Lee, Yuno; Lee, Keun-Woo; Oh, Doo-Byoung; Shin, Hyun-Dong; Kim, Seon-Won

    2015-04-01

    The modular auxiliary activity (AA) family of proteins is believed to cause amorphogenesis in addition to oxidative cleavage of crystalline cellulose although the supporting evidence is limited. HcAA10-2 is a modular AA10 family protein (58 kDa) composed of a AA10 module and a family two carbohydrate binding module (CBM2), joined by a long stretch of 222 amino acids of unknown function. The protein was expressed in Escherichia coli and purified to homogeneity. Scanning electron microscopy and X-ray diffraction analysis of Avicel treated with HcAA10-2 provided evidence for the disruption of the cellulose microfibrils ("amorphogenesis") and reduction of the crystallinity index, resulting in a twofold increase of cellulase adsorption on the polysaccharide surface. HcAA10-2 exhibited weak endoglucanase-like activity toward soluble cellulose and cello-oligosaccharides with an optimum at pH 6.5 and 45 C. HcAA10-2 catalyzed oxidative cleavage of crystalline cellulose released native and oxidized cello-oligosaccharides in the presence of copper and an electron donor such as ascorbic acid. Multiple sequence alignment indicated that His1, His109, and Phe197 in the AA10 module formed the conserved copper-binding site. The reducing sugar released from Avicel by the endoglucanase Cel5 and Celluclast accompanying HcAA10-2 was increased by four- and sixfold, respectively. Moreover, HcAA10-2 and Celluclast acted synergistically on pretreated wheat straw biomass resulting in a threefold increase in reducing sugar than Celluclast alone. Taken together, these results suggest that HcAA10-2 is a novel multifunctional modular AA10 protein possessing amorphogenesis, weak endoglucanase, and oxidative cleavage activities useful for efficient degradation of crystalline cellulose. PMID:25301584

  13. Geomagnetic storm effects on GPS based navigation

    NASA Astrophysics Data System (ADS)

    Rama Rao, P. V. S.; Gopi Krishna, S.; Vara Prasad, J.; Prasad, S. N. V. S.; Prasad, D. S. V. V. D.; Niranjan, K.

    2009-05-01

    The energetic events on the sun, solar wind and subsequent effects on the Earth's geomagnetic field and upper atmosphere (ionosphere) comprise space weather. Modern navigation systems that use radio-wave signals, reflecting from or propagating through the ionosphere as a means of determining range or distance, are vulnerable to a variety of effects that can degrade the performance of the navigational systems. In particular, the Global Positioning System (GPS) that uses a constellation of earth orbiting satellites are affected due to the space weather phenomena. Studies made during two successive geomagnetic storms that occurred during the period from 8 to 12 November 2004, have clearly revealed the adverse affects on the GPS range delay as inferred from the Total Electron Content (TEC) measurements made from a chain of seven dual frequency GPS receivers installed in the Indian sector. Significant increases in TEC at the Equatorial Ionization anomaly crest region are observed, resulting in increased range delay during the periods of the storm activity. Further, the storm time rapid changes occurring in TEC resulted in a number of phase slips in the GPS signal compared to those on quiet days. These phase slips often result in the loss of lock of the GPS receivers, similar to those that occur during strong(>10 dB) L-band scintillation events, adversely affecting the GPS based navigation.

  14. Continental scale modelling of geomagnetically induced currents

    NASA Astrophysics Data System (ADS)

    Viljanen, Ari; Pirjola, Risto; Wik, Magnus; dm, Antal; Prcser, Ern; Sakharov, Yaroslav; Katkalov, Juri

    2012-09-01

    The EURISGIC project (European Risk from Geomagnetically Induced Currents) aims at deriving statistics of geomagnetically induced currents (GIC) in the European high-voltage power grids. Such a continent-wide system of more than 1500 substations and transmission lines requires updates of the previous modelling, which has dealt with national grids in fairly small geographic areas. We present here how GIC modelling can be conveniently performed on a spherical surface with minor changes in the previous technique. We derive the exact formulation to calculate geovoltages on the surface of a sphere and show its practical approximation in a fast vectorised form. Using the model of the old Finnish power grid and a much larger prototype model of European high-voltage power grids, we validate the new technique by comparing it to the old one. We also compare model results to measured data in the following cases: geoelectric field at the Nagycenk observatory, Hungary; GIC at a Russian transformer; GIC along the Finnish natural gas pipeline. In all cases, the new method works reasonably well.

  15. Geomagnetic excursions reflect an aborted polarity state

    NASA Astrophysics Data System (ADS)

    Valet, Jean-Pierre; Plenier, Guillaume; Herrero-Bervera, E.

    2008-10-01

    Geomagnetic excursions represent short episodes of a few thousand years at most during which the field considerably exceeds its normal range of variability during a polarity state. Paleomagnetic records have now been obtained with extremely high temporal resolution which have improved our knowledge of these short events. We have compiled the most detailed records of excursions that had occurred during the Brunhes and Matuyama chrons. We show that virtual geomagnetic poles (VGPs) of at least one record of each event are able to reach the opposite polarity. In the next step, we have computed different simulations of excursions during which the dipole progressively vanishes before growing back without reversing. This scenario produces very few reversed directions which are only visible at some latitudes. We infer that it is impossible to reach the ratio of reversed to intermediate VGPs present in the paleomagnetic records if the excursions were not associated with a short period of reversed dipole field. Therefore, excursions should be regarded as two successive reversals bracketing an aborted polarity interval. We propose that the same underlying mechanisms prevail in both situations (excursions or reversals) and that below a certain strength the field reaches an unstable position which preludes either the achievement of a reversal or its return to the former polarity.

  16. Lower Mantle Superplume Growth Stimulates Geomagnetic Reversals

    NASA Astrophysics Data System (ADS)

    Olson, P.; Amit, H.

    2014-12-01

    Seismic images of the lower mantle heterogeneity consistently show two large-scale, low shear wave velocity provinces beneath Africa and the Pacific that are variously interpreted as superplumes, plume clusters, or piles of dense mantle material associated with the D" boundary layer. Hotspot reconstructions and mantle general circulation models indicate these structures have persisted for 100 Ma or longer. Here we demonstrate that time variations in the height of these structures perturbs the thickness of the D" thermal boundary layer and the heat flow across the core-mantle boundary, thereby altering the rate at which geomagnetic polarity reversals occur in the core. First we show that superplume growth increases the average heat flow on the core-mantle boundary as well as its lateral heterogeneity. We then use numerical dynamos to demonstrate that this increased core-mantle boundary heat flow stimulates magnetic polarity reversals, and conversely, that reduced core-mantle boundary heat flow associated with superplume collapse tends to inhibit polarity reversals. Our results suggest that the long, stable polarity geomagnetic superchrons such as occurred in the Cretaceous, Permian, and earlier in the geologic record may have begun and ended, respectively, by collapse and growth of one or more lower mantle superplumes.

  17. Atmospheric helium and geomagnetic field reversals.

    NASA Technical Reports Server (NTRS)

    Sheldon, W. R.; Kern, J. W.

    1972-01-01

    The problem of the earth's helium budget is examined in the light of recent work on the interaction of the solar wind with nonmagnetic planets. It is proposed that the dominant mode of helium (He4) loss is ion pumping by the solar wind during geomagnetic field reversals, when the earth's magnetic field is very small. The interaction of the solar wind with the earth's upper atmosphere during such a period is found to involve the formation of a bow shock. The penetration altitude of the shock-heated solar plasma is calculated to be about 700 km, and ionization rates above this level are estimated for a cascade ionization (electron avalanche) process to average 10 to the 9th power ions/sq cm/sec. The calculated ionization rates and the capacity of the solar wind to remove ionized helium (He4) from the upper atmosphere during geomagnetic dipole reversals are sufficient to yield a secular equilibrium over geologic time scales. The upward transport of helium from the lower atmosphere under these conditions is found to be adequate to sustain the proposed loss rate.

  18. Source effects in mid-latitude geomagnetic transfer functions

    NASA Astrophysics Data System (ADS)

    Araya Vargas, Jaime; Ritter, Oliver

    2016-01-01

    Analysis of more than 10 yr of vertical magnetic transfer function (VTF) estimates obtained at 12 mid-latitude sites, located in different continents and tectonic settings, reveals significant temporal variations for a period range between approximately 250 and 2000 s. The most ubiquitous pattern is a seasonal modulation of the VTF element that relates the vertical to the horizontal north-south magnetic components (Tx), which shows a high peak around the June solstice (and a low peak around the December solstice) regardless of the location of the site. To quantify the influence of this source effect on the amplitude of VTFs, we modelled the temporal variations of VTFs using a function with dependence on season and magnetic activity indexes. The model shows that differences between VTF estimates obtained at seasonal peaks can reach 0.08 of Tx absolute values and that the effect increases with latitude and period. Seasonal variations are observed also in the VTF component relating vertical to horizontal east-west magnetic components (Ty), but here the pattern with respect to the geographic distribution is less clear. In addition to seasonal trends, we observe long-term modulations correlating with the 11-yr solar cycle at some sites. The influence of these external source effects should be taken into account, before attempting a geological interpretation of the VTFs. It can be misleading, for example, to combine or compare VTFs obtained from long-period geomagnetic data acquired at different seasons or years. An effective method to estimate and remove these source effects from VTFs is by comparison with temporal variations of VTFs from synchronously recorded data at sites located at similar latitude (<5° of difference) and longitude (<10° of difference). Source effects in temporal variations of VTFs can be identified as those patterns that exhibit similar amplitudes and significant correlation with the geomagnetic activity at all compared sites. We also provide a second-order polynomial which can be used to estimate the amplitude of the seasonal variations in the Tx component globally as a function of latitude.

  19. Magnetic Flux Transport and Pressure Variations at Magnetotail Plasma Flow Bursts during Geomagnetically Quiet Times

    NASA Astrophysics Data System (ADS)

    Nowada, M.; Fu, S.-Y.; Parks, G. K.; Pu, Z.-Y.; Angelopoulos, V.; Carlson, C. W.; Auster, H.-U.

    2012-04-01

    The fast plasma flows in the geomagnetotail are observed during both geomagnetically active and quiet times. However, it has been unclear about the fundamental difference in the plasma fast flows between at two different geomagnetic conditions, that is, the generation mechanism of, and pictures of the energy transport and balance at the fast plasma flows. Magnetic reconnection in the magnetotail has been believed as one of the most possible mechanisms to generate the fast plasma flows regardless of the geomagnetic conditions. Recently, Nowada et al. [2012], however, demonstrated that the magnetotail magnetic reconnection does not always contribute to the generation of the fast plasma flows at geomagnetically quiet times based on the THEMIS measurements. It is very important to reveal how the energy transport and balance in the magnetotail in association with these plasma fast flows are on obtaining a clue to elucidate an essential difference in the plasma fast flows between during active and quiet geomagnetic conditions. Based on three events of the magnetotail plasma flow bursts, which are transient fast plasma flows with the durations between 1 and 2 minutes, during geomagnetically quiet times, observed by THEMIS, we examined detailed variations of the electric field as a proxy of the flux transport aspect, and associated pressure. The main characteristics of these events are shown as follows; 1) the GSM-X component of the plasma velocity (Vx) was higher than 300 km/s 2) associated parallel (V//) and perpendicular (V?) velocities to the local magnetic field line were higher than 200 km/s 3) the flow bursts were observed during which AL and AU indices were lower than 40 nT, and simultaneous Kp index range was between -1 and 1. For almost events, the parallel (E//) and perpendicular (E?) components of the electric field to the local magnetic field line were much stronger than the dawn-dusk electric field component (Ey). This result implies that a larger amount of the magnetic flux was transported into the parallel and perpendicular directions to the local magnetic field line than the dawn-dusk direction at the flow bursts. However, in the Ey component, the contribution from the dawn-to-dusk electric field (VxBz) was much greater than that from the dusk-to-dawn component (VzBx). Furthermore, for two events, significant reduction of the plasma pressure, and enhancement of the north-south magnetic field component (Bz) were observed at/near the flow bursts. Simultaneous total pressure was well-balanced, indicating that the magnetotail during the plasma flow bursts was in the state of equilibrium. Based on these results, "bubble" might play a crucial role for generating the plasma flow bursts at geomagnetically quiet times. Reference: Nowada, M., S. -Y. Fu, G. K. Parks, Z. -Y. Pu, V. Angelopoulos, C. W. Carlson, H. -U. Auster (2012), Plasma flow bursts in the magnetotail during geomagnetically quiet times 2: Relation to the magnetic reconnection and substorm process, to be submitted to Journal of Geophysical Research -Space Physics-. Corresponding Author : Motoharu Nowada nowada@pku.edu.cn

  20. Endothelin-1, oxidative stress and endogenous ANGII: mechanisms of AT1-AA-enhanced Renal and Blood Pressure Response during pregnancy

    PubMed Central

    Brewer, Justin; Liu, Ruisheng; Lu, Yan; Scott, Jeremy; Wallace, Kedra; Wallukat, Gerd; Moseley, Janae; Herse, Florian; Dechend, Ralf; Martin, James N.; LaMarca, Babbette

    2013-01-01

    Hypertension during preeclampsia is associated with increased maternal vascular sensitivity to angiotensin II (ANGII). This study was designed to determine mechanisms whereby agonistic autoantibodies to the ANGII type I receptor (AT1-AA) enhance blood pressure (MAP) and renal vascular sensitivity to ANGII during pregnancy. First, we examined MAP and renal artery resistance index (RARI) in response to chronic administration of ANGII or AT1-AA or AT1-AA+ANGII in pregnant rats compared to control pregnant rats. In order to examine mechanisms of heightened sensitivity in response to AT1-AA during pregnancy we examined the role of endogenous ANGII in AT1-AA infused pregnant rats, Endothelin-1 and oxidative stress in AT1-AA+ANGII treated rats. Chronic ANGII increased MAP from 95 +/?2 in NP rats to 115 +/?2 mmHg. Chronic AT1-AA increased MAP to 118+/?1 mmHg in NP rats which further increased to 123+/?2 with AT1-AA+ANGII. Increasing ANGII from (10?11-10?8) decreased Af-Art diameter 15-20% but sharply decreased Af-Art diameter 60% in AT1-AA pretreated vessels. RARI increased from 0.67 in NP rats to 0.70 with AT1-AA infusion, which was exacerbated to 0.74 in AT1-AA + ANGII infused rats. AT1-AA-induced hypertension decreased with Enalapril but was not attenuated. Both tissue ET-1 and ROS increased with AT1-AA+ANGII compared to AT1-AA alone and blockade of either of these pathways had significant effects on MAP or RARI. These data support the hypothesis that AT1-AA, via activation of ET-1 and oxidative stress and interaction with endogenous ANGII, are important mechanisms whereby MAP and renal vascular responses are enhanced during preeclampsia. PMID:24041954

  1. Interface Formation During Fusion™ Casting of AA3003/AA4045 Aluminum Alloy Ingots

    NASA Astrophysics Data System (ADS)

    Di Ciano, Massimo; Caron, E. J. F. R.; Weckman, D. C.; Wells, M. A.

    2015-12-01

    Fusion™ casting is a unique Direct Chill continuous casting process whereby two different alloys can be cast simultaneously, producing a laminated ingot for rolling into clad sheet metal such as AA3003/AA4045 brazing sheet. Better understanding of the wetting and interface formation process during Fusion™ casting is required to further improve process yields and also explore use of other alloy systems for new applications. In this research, AA3003-core/AA4045-clad ingots were cast using a well-instrumented lab-scale Fusion™ casting system. As-cast Fusion™ interfaces were examined metallurgically and by mechanical testing. Computational fluid dynamic analyses of the FusionTM casts were also performed. It was shown that the liquid AA4045-clad alloy was able to successfully wet and create an oxide-free, metallurgical, and mechanically sound interface with the lightly oxidized AA3003-core shell material. Based on the results of this study, it is proposed that the bond formation process at the alloys interface during casting is a result of discrete penetration of AA4045 liquid at defects in the preexisting AA3003 oxide, dissolution of underlying AA3003 by liquid AA4045, and subsequent bridging between penetration sites. Spot exudation on the AA3003 chill cast surface due to remelting and inverse segregation may also improve the wetting and bonding process.

  2. A new versatile method for modelling geomagnetic induction in pipelines

    NASA Astrophysics Data System (ADS)

    Boteler, D. H.

    2013-04-01

    Geomagnetic induction drives telluric currents in pipelines and creates fluctuations in pipe-to-soil potentials (PSP) that interfere with pipeline surveys and create conditions where corrosion is more likely to occur. To understand the process of geomagnetic induction and determine the severity and location of troublesome effects requires the ability to model geomagnetic induction in realistic pipeline networks. Previous modelling work, based on transmission line theory, has provided some insights into the process but has to be customized for each situation. This paper presents a new versatile modelling technique that can be easily applied to any pipeline network. The essential part of the new method is the development of an equivalent-pi circuit for geomagnetic induction in a pipeline section. A complex pipeline network can then be represented as a set of equivalent-pi circuits that are combined to form a nodal admittance network comprising connections between nodes and to ground from each node. The nodal admittance matrix method is then used to determine the voltages everywhere in the pipeline system. Sample results are presented for geomagnetic induction in an example pipeline. It is shown how the modelling results can be combined with electric fields calculated from geomagnetic observatory data to determine the PSP variations that occur during geomagnetic disturbances.

  3. MAXIMUM CORONAL MASS EJECTION SPEED AS AN INDICATOR OF SOLAR AND GEOMAGNETIC ACTIVITIES

    SciTech Connect

    Kilcik, A.; Yurchyshyn, V. B.; Abramenko, V.; Goode, P. R.; Gopalswamy, N.; Ozguc, A.; Rozelot, J. P.

    2011-01-20

    We investigate the relationship between the monthly averaged maximal speeds of coronal mass ejections (CMEs), international sunspot number (ISSN), and the geomagnetic Dst and Ap indices covering the 1996-2008 time interval (solar cycle 23). Our new findings are as follows. (1) There is a noteworthy relationship between monthly averaged maximum CME speeds and sunspot numbers, Ap and Dst indices. Various peculiarities in the monthly Dst index are correlated better with the fine structures in the CME speed profile than that in the ISSN data. (2) Unlike the sunspot numbers, the CME speed index does not exhibit a double peak maximum. Instead, the CME speed profile peaks during the declining phase of solar cycle 23. Similar to the Ap index, both CME speed and the Dst indices lag behind the sunspot numbers by several months. (3) The CME number shows a double peak similar to that seen in the sunspot numbers. The CME occurrence rate remained very high even near the minimum of the solar cycle 23, when both the sunspot number and the CME average maximum speed were reaching their minimum values. (4) A well-defined peak of the Ap index between 2002 May and 2004 August was co-temporal with the excess of the mid-latitude coronal holes during solar cycle 23. The above findings suggest that the CME speed index may be a useful indicator of both solar and geomagnetic activities. It may have advantages over the sunspot numbers, because it better reflects the intensity of Earth-directed solar eruptions.

  4. Ionospheric, protonospheric and total electron content in quiet geomagnetic conditions and during geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Nosikov, Igor; Klimenko, Maxim; Klimenko, Vladimir

    This report presents the results of studies the ionospheric, plasmaspheric and total electron content during recent minimum of solar activity in quiet geomagnetic condition and for geomagnetic storm on 26 September 2011. A comparison of the calculation results obtained using the GSM TIP model, with observational data of the mid- and high-latitude ionospheric sounding stations, as well as estimation of the plasmaspheric reservoir contribution into the total electron content obtained from GPS TEC measurements, COSMIC radio-occultation experiment and incoherent scatter radars were presented. The particular attention is given to the global distribution of the O+/H+ transition height in order to determine the top and low boundary for ionospheric and protonospheric electron content, respectively. This work was supported by Grant of Russian President ???-4866.2014.5, ?14-05-00578, and Program 22 RAS.

  5. ILK Index and Regrowth in Alopecia Areata.

    PubMed

    Stallings, Alicia M; Velez, Mara Weinstein; Fiessinger, Lori A; Piliang, Melissa P; Mesinkovska, Natasha A; Kyei, Angela; Bergfeld, Wilma F

    2015-11-01

    There is insufficient data in the literature concerning optimal intralesional kenalog (ILK) dosing for the treatment of alopecia areata (AA). The purpose of this pilot study was to evaluate the utility of using the ratio of ILK received to initial Severity of Alopecia Tool (SALT) score to guide ILK dosing in patients with AA. Using photographic data from patients at baseline and 4-months follow-up, hair loss in 15 patients treated with AA was retrospectively graded using the SALT scores. The ILK received/initial SALT score (ILK index) was calculated for each patient, and the mean ILK index for patients who experienced significant (?50%) and suboptimal (<50%) hair regrowth at 4 months follow-up were compared. Patients who experienced suboptimal hair regrowth had a lower ILK index on average than patients who experienced significant improvement. Although the difference did not meet significance (<0.1), the trend suggests that the ILK index, a novel calculation, may be a useful tool for guiding ILK dosing in the treatment of AA. PMID:26551947

  6. Geomagnetic activity and north-south asymmetry of cosmic rays circa 1 GV. Final report, 1 March 1977-30 September 1984

    SciTech Connect

    Ely, J.T.; Huang, T.C.

    1986-09-26

    Various features of solar-sector synchronous modulations of the particulate cosmic radiation reaching the earth's atmosphere have been studied using satellite and surface data. The flux in the broad maximum of the galactic cosmic-ray differential spectrum (near 1 GV rigidity) exhibits an intermittent north-south asymmetry in mid and high geomagnetic latitudes. This modulation exhibited a strong association with the geomagnetic disturbance index and interplanetary magnetic field direction during the 1964 and 1965 years of sunspot minimum. Such correlations are consistent with the predictions of a theory that attributes the north south asymmetry to reconnection of the interplanetary and geomagnetic fields. This finding is also consistent with suggestions that the solar-activity influence on atmospheric processes may be mediated by the resulting modulations of upper tropospheric ionization.

  7. Is motivation influenced by geomagnetic activity?

    PubMed

    Starbuck, S; Cornélissen, G; Halberg, F

    2002-01-01

    To eventually build a scientific bridge to religion by examining whether non-photic, non-thermic solar effects may influence (religious) motivation, invaluable yearly world wide data on activities from 1950 to 1999 by Jehovah's Witnesses on behalf of their church were analyzed chronobiologically. The time structure (chronome) of these archives, insofar as it is able to be evaluated in yearly means for up to half a century, was assessed. Least squares spectra in a frequency range from one cycle in 42 to one in 2.1 years of data on the average number of hours per month spent in work for the church, available from 103 different geographic locations, as well as grand totals also including other sites, revealed a large peak at one cycle in about 21 years. The non-linear least squares fit of a model consisting of a linear trend and a cosine curve with a trial period of 21.0 years, numerically approximating that of the Hale cycle, validated the about 21.0-year component in about 70% of the data series, with the non-overlap of zero by the 95% confidence interval of the amplitude estimate. Estimates of MESOR (midline-estimating statistic of rhythm, a rhythm (or chronome) adjusted mean), amplitude and period were further regressed with geomagnetic latitude. The period estimate did not depend on geomagnetic latitude. The about 21.0-year amplitude tends to be larger at low and middle than at higher latitudes and the resolution of the about 21.0-year cycle, gauged by the width of 95% confidence intervals for the period and amplitude, is higher (the 95% confidence intervals are statistically significantly smaller) at higher than at lower latitudes. Near-matches of periods in solar activity and human motivation hint that the former may influence the latter, while the dependence on latitude constitutes evidence that geomagnetic activity may affect certain brain areas involved in motivation, just as it was earlier found that it is associated with effects on the electrocardiogram and anthropometry. PMID:12653182

  8. Aurorae boreales and geomagnetic inclinations as aids to archaeomagnetic dating

    NASA Astrophysics Data System (ADS)

    Liritzis, Yiannis

    1988-08-01

    Geomagnetic virtual pole positions (VGPs) determined from archaeomagnetic directional data have been compared with three ancient accounts of low latitude observations of the Aurorae borealis from the 384-322 BC period, the period from 55 BC to 40 AD, and from 1138 AD. The geomagnetic latitudes of the VGPs obtained were found to range from 65 to 70 deg. The present results are consistent with the earlier observations, confirming the inclination of the geomagnetic pole toward the observing sites. Auroral types are discussed, along with severe aurora related to magnetic storms.

  9. Geomagnetic storms: Potential economic impacts on electric utilities

    SciTech Connect

    Barnes, P.R.; Van Dyke, J.W.

    1991-03-20

    Geomagnetic storms associated with sunspot and solar flare activity can disturb communications and disrupt electric power. A very severe geomagnetic storm could cause a major blackout with an economic impact of several billion dollars. The vulnerability of electric power systems in the northeast United States will likely increase during the 1990s because of the trend of transmitting large amounts of power over long distance to meet the electricity demands of this region. A comprehensive research program and a warning satellite to monitor the solar wind are needed to enhance the reliability of electric power systems under the influence of geomagnetic storms. 7 refs., 2 figs., 1 tab.

  10. Search for correlation between geomagnetic disturbances and mortality

    NASA Technical Reports Server (NTRS)

    Lipa, B. J.; Sturrock, P. A.; Rogot, F.

    1976-01-01

    A search is conducted for a possible correlation between solar activity and myocardial infarction and stroke in the United States. A statistical analysis is performed using data on geomagnetic activity and the daily U.S. mortality due to coronary heart disease and stroke for the years 1962 through 1966. None of the results are found to yield any evidence of a correlation. It is concluded that correlations claimed by Soviet workers between geomagnetic activity and the incidence of various human diseases are probably not statistically significant or probably are not due to a causal relation between geomagnetic activity and disease.

  11. A new look at the origins of geomagnetic pulsations

    NASA Astrophysics Data System (ADS)

    Gulelmi, A. V.

    1985-04-01

    The physical mechanisms involved in the generation of geomagnetic pulsations and MHD waves are discussed. Consideration is given to the interaction of the solar wind with the magnetosphere; the relationship between Pc3 micropulsations adn the solar wind plasma; and some possible reasons for the differences observed in geomagnetic pulsations at the North and South poles. The patterns of MHD waves in the magnetospheres of Jupiter, Venus, and Mercury are also discussed on the basis of satellite observations. The possibility of using geomagnetic pulsations for induction sounding of the earth core is considered.

  12. Chronomics, neuroendocrine feedsidewards and the recording and consulting of nowcasts--forecasts of geomagnetics.

    PubMed

    Jozsa, R; Halberg, F; Cornlissen, G; Zeman, M; Kazsaki, J; Csernus, V; Katinas, G S; Wendt, H W; Schwartzkopff, O; Stebelova, K; Dulkova, K; Chibisov, S M; Engebretson, M; Pan, W; Bubenik, G A; Nagy, G; Herold, M; Hardeland, R; Hther, G; Pggeler, B; Tarquini, R; Perfetto, F; Salti, R; Olah, A; Csokas, N; Delmore, P; Otsuka, K; Bakken, E E; Allen, J; Amory-Mazaudin, C

    2005-10-01

    A multi-center four-hourly sampling of many tissues for 7 days (00:00 on April 5-20:00 to April 11, 2004), on rats standardized for 1 month in two rooms on antiphasic lighting regimens happened to start on the day after the second extremum of a moderate double magnetic storm gauged by the planetary geomagnetic Kp index (which at each extremum reached 6.3 international [arbitrary] units) and by an equatorial index Dst falling to -112 and -81 nT, respectively, the latter on the first day of the sampling. Neuroendocrine chronomes (specifically circadian time structures) differed during magnetically affected and quiet days. The circadian melatonin rhythm had a lower MESOR and lower circadian amplitude and tended to advance in acrophase, while the MESOR and amplitude of the hypothalamic circadian melatonin rhythm were higher during the days with the storm. The circadian parameters of circulating corticosterone were more labile during the days including the storm than during the last three quiet days. Feedsidewards within the pineal-hypothalamic-adrenocortical network constitute a mechanism underlying physiological and probably also pathological associations of the brain and heart with magnetic storms. Investigators in many fields can gain from at least recording calendar dates in any publication so that freely available information on geomagnetic, solar and other physical environmental activity can be looked up. In planning studies and before starting, one may gain from consulting forecasts and the highly reliable nowcasts, respectively. PMID:16275503

  13. Stochastic resonance in geomagnetic polarity reversals.

    PubMed

    Consolini, Giuseppe; De Michelis, Paola

    2003-02-01

    Among noise-induced cooperative phenomena a peculiar relevance is played by stochastic resonance. In this paper we offer evidence that geomagnetic polarity reversals may be due to a stochastic resonance process. In detail, analyzing the distribution function P(tau) of polarity residence times (chrons), we found the evidence of a stochastic synchronization process, i.e., a series of peaks in the P(tau) at T(n) approximately (2n+1)T(Omega)/2 with n=0,1,...,j and T(omega) approximately 0.1 Myr. This result is discussed in connection with both the typical time scale of Earth's orbit eccentricity variation and the recent results on the typical time scale of climatic long-term variation. PMID:12633403

  14. CME Link to the Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

    The coronal mass ejection (CME) link to geomagnetic storms stems from the southward component of the interplanetary magnetic field contained in the CME flux ropes and in the sheath between the flux rope and the CME-driven shock. A typical storm-causing CME is characterized by (i) high speed, (ii) large angular width (mostly halos and partial halos), and (iii)solar source location close to the central meridian. For CMEs originating at larger central meridian distances, the storms are mainly caused by the sheath field. Both the magnetic and energy contents of the storm-producing CMEs can be traced to the magnetic structure of active regions and the free energy stored in them.

  15. Protection against lightning on the geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    ?op, R.; Milev, G.; Deeljin, D.; Kosma?, J.

    2014-04-01

    The Sinji Vrh Geomagnetic Observatory was built on the brow of the mountain Gora, above Ajdov?ina, and all over Europe one may hardly find an area which is more often struck by lightning than this south-western part of Slovenia. When the humid air masses of a storm front hit the edge of Gora, they rise up more than 1000 m in a very short time, and this causes the additional electrical charge of stormy clouds. The reliability of operations performed in the every building of observatory could be increased by understanding the formation of lightning in the thunderstorm cloud, the application of already proven methods of protection against a strike of lightning and against its secondary effects. To reach this goal the following groups of experts have to co-operate: the experts in the field of protection against lightening phenomenon, the constructors and manufacturers of equipment and the observatory managers.

  16. Protection against lightning at a geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    ?op, R.; Milev, G.; Deeljin, D.; Kosma?, J.

    2014-08-01

    The Sinji Vrh Geomagnetic Observatory was built on the brow of Gora, the mountain above Ajdov?ina, which is a part of Trnovo plateau, and all over Europe one can hardly find an area which is more often struck by lightning than this southwestern part of Slovenia. When the humid air masses of a storm front hit the edge of Gora, they rise up more than 1000 m in a very short time, and this causes an additional electrical charge of stormy clouds. The reliability of operations performed in every section of the observatory could be increased by understanding the formation of lightning in a thunderstorm cloud and the application of already-proven methods of protection against a stroke of lightning and against its secondary effects. To reach this goal the following groups of experts have to cooperate: experts in the field of protection against lightning, constructors and manufacturers of equipment and observatory managers.

  17. Geomagnetic Effect Caused by 1908 Tunguska Event

    NASA Astrophysics Data System (ADS)

    Losseva, T. V.; Kuzmicheva, M. Y.

    2010-12-01

    The analysis of the magnetograms of Irkutsk observatory on the 30th June 1908 showed that the explosion of Tunguska bolide was accompanied by variations of the Earths magnetic field, which were being continued for several hours [1]. Irkutsk geophysical observatory is located approximately in 950 km to the southeast from the point of Tunguska explosion and it was nearest point, where the continuous recording of the components of the geomagnetic field was in progress. We suppose that it was caused by magnetic field of the current system, generated in the E-layer of ionosphere by gas dynamical flow after the Tunguska explosion [2]. Plunging through the atmosphere, cosmic body forms a hot rarefied channel behind it; the hydrostatic equilibrium of pressure in the channel becomes broken. The particles of the body vapor and atmospheric air, involved in the motion, lift along this channel upward (so-called plume). In the rarefied layers of the atmosphere they move along the ballistic trajectories in the gravitational field. While falling down gas loses its kinetic energy in dense layers of the atmosphere, which is converted into thermal energy. Then the reflected shock wave is formed. The gas heated in it rises up and all these processes repeat. The effects of heating and ionization of gas at height of 100 km, caused by the oscillations in the atmosphere, can lead to a distortion of the existing current system in ionosphere and generation of new ones. Since the Tunguska body had an oblique trajectory, the plume was ejected in the direction opposite to motion of Tunguska body and provided ionized region at the distance about 700 km from the epicenter at time moment 400 seconds after explosion. Gas dynamical simulation and estimates of the plume parameters have been fulfilled to calculate conductivity profiles and the electric field. Magnetic field of the induced current system has been obtained by the numerical simulation of Maxwells equations. Analysis of calculation results of this current system shows that an unique azimuth of trajectory of the body exists, for which the variations of all three components of the geomagnetic field do not contradict to the observation data. This azimuth is equal to 306 degrees, while other estimates are in the range of 290-344 degrees. This idea of the atmospheric plume ejected along the trajectory and ionization in the upper atmosphere, caused by the following atmospheric oscillations, could explain the geomagnetic effect both in general and locally in Irkutsk observatory: the time delay and the variations of all magnetic field components. Binding of simulation results of observation data also allows us to select the unique trajectory azimuth for Tunguska body. References: [1] Ivanov K.G. The Geomagnetic phenomena, which were being observed on the Irkutsk magnetic observatory, following the explosion of the Tunguska meteorite //Meteoritika. 1961. Iss. XXI. P.46-49 (in Russian). [2] Losseva T., Merkin V., Nemtchinov I. Estimations of the Aeronomical and Electromagnetic Disturbances in the E-layer of the Ionosphere, caused by Tunguska Event // AGU Fall Meeting. 1999. SA32A-09.

  18. Historical records of the geomagnetic field

    NASA Astrophysics Data System (ADS)

    Arneitz, Patrick; Heilig, Balzs; Vadasz, Gergely; Valach, Fridrich; Dolinsk, Peter; Hejda, Pavel; Fabian, Karl; Hammerl, Christa; Leonhardt, Roman

    2014-05-01

    Records of historical direct measurements of the geomagnetic field are invaluable sources to reconstruct temporal variations of the Earth's magnetic field. They provide information about the field evolution back to the late Middle Age. We have investigated such records with focus on Austria and some neighbouring countries. A variety of new sources and source types are examined. These include 19th century land survey and observatory records of the Imperial and Royal "Centralanstalt f. Meteorologie und Erdmagnetismus", which are not included in the existing compilations. Daily measurements at the Imperial and Royal Observatory in Prague have been digitized. The Imperial and Royal Navy carried out observations in the Adriatic Sea during several surveys. Declination values have been collected from famous mining areas in the former Austro-Hungarian Empire. In this connection, a time series for Banska Stiavnica has been compiled. In the meteorological yearbooks of the monastery Kremsmnster regular declination measurements for the first half of the 19th century were registered. Marsigli's observations during military mapping works in 1696 are also included in our collection. Moreover, compass roses on historical maps or declination values marked on compasses, sundials or globes also provide information about ancient field declination. An evaluation of church orientations in Lower Austria and Northern Germany did not support the hypothesis that church naves had been aligned along the East-West direction by means of magnetic compasses. Therefore, this potential source of information must be excluded from our collection. The gathered records are integrated into a database together with corresponding metadata, such as the used measurement instruments and methods. This information allows an assessment of quality and reliability of the historical observations. The combination of compilations of historical measurements with high quality archeo- and paleomagnetic data in a single database enables a reliable joint evaluation of all types of magnetic field records from different origins. This collection forms the basis for a combined inverse modelling of the geomagnetic field evolution.

  19. Do ambient electromagnetic fields affect behaviour? A demonstration of the relationship between geomagnetic storm activity and suicide.

    PubMed

    Berk, Michael; Dodd, Seetal; Henry, Margaret

    2006-02-01

    The relationship between ambient electromagnetic fields and human mood and behaviour is of great public health interest. The relationship between Ap indices of geomagnetic storm activity and national suicide statistics for Australia from 1968 to 2002 was studied. Ap index data was normalised so as to be globally uniform and gave a measure of storm activity for each day. A geomagnetic storm event was defined as a day in which the Ap index was equal to or exceeded 100 nT. Suicide data was a national tally of daily male and female death figures where suicide had been documented as the cause of death. A total of 51 845 males and 16 327 females were included. The average number of suicides was greatest in spring for males and females, and lowest in autumn for males and summer for females. Suicide amongst females increased significantly in autumn during concurrent periods of geomagnetic storm activity (P = .01). This pattern was not observed in males (P = .16). This suggests that perturbations in ambient electromagnetic field activity impact behaviour in a clinically meaningful manner. The study furthermore raises issues regarding other sources of stray electromagnetic fields and their effect on mental health. PMID:16304696

  20. Graded response of heart rate variability, associated with an alteration of geomagnetic activity in a subarctic area.

    PubMed

    Oinuma, S; Kubo, Y; Otsuka, K; Yamanaka, T; Murakami, S; Matsuoka, O; Ohkawa, S; Cornlissen, G; Weydahl, A; Holmeslet, B; Hall, C; Halberg, F

    2002-01-01

    It is becoming recognized that geomagnetic activity may influence biological processes, including the incidence of various human diseases. There is evidence that heart rate variability (HRV) may serve not only as an index of autonomic coordination of the circulation, but also as a powerful predictor of risk in apparently healthy subjects. This study focuses on the effects of geomagnetic disturbance on HRV, by comparing different indices of HRV of young, healthy men living in a subarctic area on days of low (Ap; 0-7), middle (Ap; 7-20), and high (Ap; 20-45) geomagnetic activity. The effect of geomagnetic disturbance on HRV is examined on the basis of 7-day records by Holter ECG, obtained longitudinally on 5 clinically healthy men, 21-31 years of age, in Alta, Norway (70 degree N). Frequency- and time-domain measures of HRV were analyzed for each subject on separate 24-hour spans. A graded alteration of HRV endpoints was found in association with increased geomagnetic activity. As time-domain measures of HRV, SDNNIDX and the 90% length of the Lorenz plot decreased statistically significantly on days with increased geomagnetic disturbance (p = 0.0144 and p = 0.0102, respectively). A graded decrease in frequency-domain HRV measures was also validated statistically for the total spectral power (decrease of 18.1% and 31.6% on days when 7 < Ap < 20 and 20 < Ap < 45 versus days when Ap < 7; p = 0.0013). The decrease in spectral power was mainly found at frequencies below 0.04 Hz, in the "ultra-low-frequency" (0.0001-0.003 Hz; 18.1% and 27.5% decrease, respectively; p = 0.0102) and "very-low-frequency" (0.003-0.04 Hz; 12.9% and 28.6% decrease, respectively; p = 0.0209) regions of the spectrum. The decrease in spectral power was much less pronounced around 10.5 sec ("low frequency"; N.S.) and around 3.6 sec ("high frequency"; N.S.). Evidence is provided here that HRV decreases on magnetically disturbed days, and that it does so in a dose-dependent fashion, HRV being depressed more on days when 20 < Ap < 45 than on days when 7 < Ap < 20, by comparison with days when Ap < 7. This graded response of HRV to geomagnetic activity should encourage us to search for human magnetoreceptors and for a better understanding of putative mechanisms of magnetoreception. PMID:12653181

  1. A Windshear Hazard Index

    NASA Technical Reports Server (NTRS)

    Proctor, Fred H.; Hinton, David A.; Bowles, Roland L.

    2000-01-01

    An aircraft exposed to hazardous low-level windshear may suffer a critical loss of airspeed and altitude, thus endangering its ability to remain airborne. In order to characterize this hazard, a nondimensional index was developed based oil aerodynamic principals and understanding of windshear phenomena, 'This paper reviews the development and application of the Bowles F-tactor. which is now used by onboard sensors for the detection of hazardous windshear. It was developed and tested during NASA/I:AA's airborne windshear program and is now required for FAA certification of onboard radar windshear detection systems. Reviewed in this paper are: 1) definition of windshear and description of atmospheric phenomena that may cause hazardous windshear. 2) derivation and discussion of the F-factor. 3) development of the F-factor hazard threshold, 4) its testing during field deployments, and 5) its use in accident reconstructions,

  2. Human physiological reaction to geomagnetic disturbances of solar origin

    NASA Astrophysics Data System (ADS)

    Dimitrova, Sv.; Stoilova, I.

    2002-12-01

    During the last two decades publications about the influence of geomagnetic activity on human health increase but there are not still strong evidences for this relationship. We performed measurements and observations of 86 working volunteers during the period of autumn and spring equinox. We examined systolic, diastolic blood pressure and pulse rate. We also collected data for some personal health condition complaints. Four-way analyses of variance (MANOVA method) were employed and the influence of factors geomagnetic activity level, sequence of the days of measurements with respect to the increased geomagnetic activity, medicaments and sex was investigated. We also performed three-way analyses of variance and investigated influence of atmospheric pressure, medicaments and sex on the physiological parameters under consideration. Our investigations indicate that most of the persons examined irrespectively to their health status could be sensitive to the geomagnetic changes, which influence directly self-confidence and working ability.

  3. Conference explores relationship between geomagnetic storms and substorms

    NASA Astrophysics Data System (ADS)

    Sharma, A. Surjalal; Lakhina, Gurbax S.; Kamide, Yohsuke

    The terrestrial magnetosphere is strongly disturbed by solar plasma, especially during periods of increased solar activity These disturbances constitute geomagnetic storms and substorms and may damage many technological systems, depending on the intensity of the geomagnetic activity Substorms have long been considered to be essential components of geomagnetic storms, but recent studies of the solar windmagnetosphere system are leading to a rethinking of their relationship.About 100 scientists from around the world gathered near Mumbai, India, last March for the AGU Chapman Conference on Storm-Substorm Relationships, to assess current understanding of the relationship between these two major components of geomagnetic activity. The recent data from space missions and ground-based observations and developments in theory and modeling were extensively reviewed and critically examined to assess the advances and to identify key future directions.

  4. A model of geomagnetic secular variation for 1980-1983

    USGS Publications Warehouse

    Peddie, N.W.; Zunde, A.K.

    1987-01-01

    We developed an updated model of the secular variation of the main geomagnetic field during 1980 through 1983 based on annual mean values for that interval from 148 worldwide magnetic observatories. The model consists of a series of 80 spherical harmonics, up to and including those of degree and order 8. We used it to form a proposal for the 1985 revision of the International Geomagnetic Reference Field (IGRF). Comparison of the new model, whose mean epoch is approximately 1982.0, with the Provisional Geomagnetic Reference Field for 1975-1980 (PGRF 1975), indicates that the moment of the centered-dipole part of the geomagnetic field is now decreasing faster than it was 5 years ago. The rate (in field units) indicated by PGRF 1975 was about -25 nT a-1, while for the new model it is -28 nT a-1. ?? 1987.

  5. Geomagnetic quiet time (Sq) variations at high latitudes

    NASA Astrophysics Data System (ADS)

    Detrick, D. L.; Lanzerotti, L. J.

    The availability of geomagnetic data from two Antarctic Geophysical Observatories (AGOs P5 and P6; invariant geomagnetic latitudes 87 and 85S) in the deep southern hemisphere polar cap allows for the first time the study of the geomagnetic quiet time variations (Sq) at the highest latitudes possible. We present analyses of the Sq variations at these two AGO sites for data obtained in 1997, and compare them with model predictions. We find strong evidence that the Sq variations near 90S geomagnetic latitude are considerably larger (factor of two or more) than would be expected from the model, independent of season. Comparison of the measurements of the vertical components to the model suggests that there may be large differences in the Earth's deep mantle conductivity under the Antarctic ice cap at the two locations. These observations highlight the need for incorporating high latitude data into Sq models.

  6. Auroral Zone E-Region Electron Density Geomagnetic Storm Enhancements Predicted by the Empirical STORM-E Model

    NASA Astrophysics Data System (ADS)

    Mertens, Christopher; Bilitza, Dieter; Xu, Xiaojing

    2012-07-01

    Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region electron densities. The empirical model is called STORM-E. The proxy for characterizing the E-region response to geomagnetic forcing is NO+(v) volume emission rates (VER) derived from the TIMED/SABER 4.3 um channel limb radiance measurements. The storm-time response of the NO+(v) 4.3 um VER is most sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO+(v) 4.3 um VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. In this paper, the development of the E-region electron density storm-time correction factor is described. The STORM-E storm-time correction factor is fit to a single geomagnetic index. There are four versions of the STORM-E model. Each version is fit to one of the following indices: HP-, AE-, Ap-, or Dst. High-latitude incoherent scatter radar (ISR) E-region electron density measurements are compared to STORM-E predictions for various geomagnetic storm periods during solar cycle 23. These comparisons show that STORM-E significantly improves the prediction of E-region electron density enhancements due to auroral particle precipitation, in comparison to the nominal International Reference Ionosphere (IRI) model or to the quiet-time baseline electron density concentrations measured by ISR. The version of the STORM-E model based on the fit to the Ap-index is now incorporated into the 2012 release of the IRI.

  7. Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

    NASA Astrophysics Data System (ADS)

    Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

    2013-04-01

    In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

  8. Detection and characterization of geomagnetic pulsations using HF ionospheric heating

    SciTech Connect

    Lee, H.S.; Ferraro, A.J.; Olson, J.V. Alaska Univ., Fairbanks )

    1990-12-01

    This paper describes the geomagnetic pulsations observed in the high-latitude ionosphere during an experiment dealing with the ionospheric generation of ELF/VLF EM waves in June and October 1987. There was clear evidence of geomagnetic pulsations intermixed with the ELF/VLF signals in both the magnitude and phase data. A simple simulation model is introduced to facilitate the interpretation of the data, and a procedure for characterizing the pulsation is described. 5 refs.

  9. The Geomagnetic Field and Radiation in Near-Earth Orbits

    NASA Technical Reports Server (NTRS)

    Heirtzler, J. R.

    1999-01-01

    This report shows, in detail, how the geomagnetic field interacts with the particle flux of the radiation belts to create a hazard to spacecraft and humans in near-Earth orbit. It illustrates the geometry of the geomagnetic field lines, especially around the area where the field strength is anomalously low in the South Atlantic Ocean. It discusses how the field will probably change in the future and the consequences that may have on hazards in near space.

  10. Auroral activities observed by SNPP VIIRS day/night band during a long period geomagnetic storm event on April 29-30, 2014

    NASA Astrophysics Data System (ADS)

    Shao, Xi; Cao, Changyong; Liu, Tung-chang; Zhang, Bin; Wang, Wenhui; Fung, Shing F.

    2015-10-01

    The Day/Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPP represents a major advancement in night time imaging capabilities. The DNB senses radiance that can span 7 orders of magnitude in one panchromatic (0.5-0.9 μm) reflective solar band and provides imagery of clouds and other Earth features over illumination levels ranging from full sunlight to quarter moon. When the satellite passes through the day-night terminator, the DNB sensor is affected by stray light due to solar illumination on the instrument. With the implementation of stray light correction, stray light-corrected DNB images enable the observation of aurora occurred in the high latitude regions during geomagnetic storms. In this paper, DNB observations of auroral activities are analyzed during a long period (> 20 hours) of geomagnetic storm event occurred on Apr. 29-30, 2014. The storm event has the Bz component of interplanetary magnetic field (IMF) pointing southward for more than 20 hours. During this event, the geomagnetic storm index Dst reached -67 nT and the geomagnetic auroral electrojet (AE) index increased and reached as high as 1200 nT with large amplitude fluctuations. The event occurred during new moon period and DNB observation has minimum moon light contamination. During this event, auroras are observed by DNB for each orbital pass on the night side (~local time 1:30am) in the southern hemisphere. DNB radiance data are processed to identify regions of aurora during each orbital pass. The evolution of aurora is characterized with time series of the poleward and equatorward boundary of aurora, area, peak radiance and total light emission of the aurora in DNB observation. These characteristic parameters are correlated with solar wind and geomagnetic index parameters. It is found that the evolution of total area-integrated radiance of auroral region over the southern hemisphere correlated well with the ground geomagnetic AE index with correlation coefficient = 0.71. DNB observations of aurora help understand the relations among solar wind variation, auroral activities and geomagnetic responses.

  11. Statistical analysis of geomagnetic storms, coronal mass ejections and solar energetic particle events in the framework of the COMESEP project

    NASA Astrophysics Data System (ADS)

    Malandraki, Olga

    2013-04-01

    Geomagnetic storms and Solar Energetic Particle (SEP) radiation storms are hazards in space. It is important to mitigate the effects space weather phenomena may have on technology and human life. The aim of the EU FP7 COMESEP (Coronal Mass Ejections and Solar Energetic Particles) project is to develop forecasting tools both for geomagnetic and SEP storms, and relies on both models and data. This includes a statistical analysis of geomagnetic storms and SEP events during the SOHO era. The goal is to connect the impact of these phenomena with the associated Coronal Mass Ejection (CME) and/or solar flare characteristics. Results of these analyses are being implemented into the COMESEP space weather alert system that is being built based on the produced tools. For the analysis of geomagnetic storms, a representative subset of CMEs from the LASCO/SOHO catalog is selected, and includes associations with Dst index values. The main objective is to determine the probability distributions of Dst and other relationships depending on the CME and flare characteristics. The effect of multiple CME occurrences on the probability of large Dst index values and the treatment of semiannual variations of storms are also evaluated. The analysis of SEP events focuses on the quantification of SEP occurrence probabilities and on the identification of correlations between SEPs and solar events. Both quantities depend on the flare heliographic location, soft X-ray intensity, the CME speed and width. The SEP parameters studied include peak fluxes, fluences, spectral fit parameters and enhancements in heavy ion fluxes. A preliminary estimation of false alarms for our system based on the statistical analysis used is under progress to asses the validity of the alerts. This work has received funding from the European Commission FP7 Project COMESEP (263252).

  12. Long-duration geomagnetic storm effects on the D region of the ionosphere: Some case studies using VLF signal

    NASA Astrophysics Data System (ADS)

    Choudhury, Abhijit; De, Barin Kumar; Guha, Anirban; Roy, Rakesh

    2015-01-01

    present work investigates the effects of long-duration geomagnetic storms on VLF signal during ionospheric sunrise time, commonly known as D Layer Preparation Time (DLPT) depth. The VLF signal at 19.8 kHz transmitted from Northwest Cape, Australia, and received at a low-latitude station, Tripura, India, is used for the present analysis. The data for the analysis are selected from November 2008 to October 2011. In the active period of the geomagnetic storms, the average DLPT depth is found to have a negative correlation coefficient of 0.91 with geomagnetic Ap index. It is also found that with each 10 unit increase of Ap index, the DLPT depth (the day and night asymmetry level) changes by 1.25 dB. The results are supported with modeled International Reference Ionosphere (IRI) electron density data and DLPT depth at 71 km height for the three positions, namely, receiver position, signal hop position, and the transmitter position along the total Great Circle Path. It is found that the receiver position electron density is the main controlling factor for DLPT depth. The correlation between IRI electron density and DLPT depth increases from -0.13 at transmitter position to -0.33 at the first hop position, to -0.46 at the receiver position, respectively. The percentage change of post storm electron density, at 71 km height, is found to increase by more than 100% at the receiver position. The results are discussed on the basis of the electron density changes over the signal propagation path, mainly caused by the geomagnetic storms.

  13. Frequency-modulated solar rotational periodicity of geomagnetic indices

    NASA Astrophysics Data System (ADS)

    Chang, Heon-Young

    2014-10-01

    Many attempts have been made to search for various timescales in the power spectrum of geomagnetic indices so that common periodicities in the solar activity and geomagnetic activity indices are identified. The spectral behavior of geomagnetic activity parameters may also provide invaluable information about physical processes involved. In this study we attempt to demonstrate that the frequency modulation associated with a long-term variation may cause extra sidelobes around the principal peak with a periodicity of 27 d in the observed power spectrum of geomagnetic activity indices, and/or may even split the peak into two adjacent peaks. We employ a straightforward model of an oscillation frequency-modulated by an arbitrary agent to consider the solar rotational periodicity of geomagnetic indices. As a result, we have found that the peak with the periodicity of 27 d in the observed power spectrum of geomagnetic indices seems likely frequency-modulated by the amount of 0.0026 d-1 which corresponds to a 1 yr period. We thus suggest that the fundamental period of the periodic perturbative agent is much longer than a year according to our analysis. Finally, we conclude by discussing the implications of what we have found.

  14. Study of Proton cutoffs during geomagnetically disturbed times

    NASA Astrophysics Data System (ADS)

    Kanekal, S. G.; Looper, M. D.; Baker, D. N.; Blake, J. B.

    2005-12-01

    It is currently believed that solar energetic particles (SEP) may be accelerated at solar flares and/or at interplanetary shocks driven by coronal mass ejections (CMEs). CMEs also cause intense geomagnetic storms during which the geomagnetic field can be highly distorted.SEP fluxes penetrate the terrestrial magnetosphere and reach specific regions depending upon the geomagnetic field configuration. The cutoff latitude is a well defined latitude below which a charged particle of a given rigidity (momentum per unit charge) arriving from a given direction cannot penetrate. SEP cutoff location can therefore be potentially useful in determining the geomagnetic field configuration. This paper reports on the measurements of solar energetic proton cutoffs made by two satellites, SAMPEX and Polar during geomagnetically disturbed times. We study select SEP events and compare our measurements with cutoffs calculated by a charged particle tracing code which utilizes several currently used models of the geomagnetic field. The measured SEP proton cutoffs cover a wide range of rigidities and are obtained at high-altitudes by the HIST detector onboard Polar and at low-altitudes by the PET detctor onboard SAMPEX.

  15. Globally strong geomagnetic field intensity circa 3000 years ago

    NASA Astrophysics Data System (ADS)

    Hong, Hoabin; Yu, Yongjae; Lee, Chan Hee; Kim, Ran Hee; Park, Jingyu; Doh, Seong-Jae; Kim, Wonnyon; Sung, Hyongmi

    2013-12-01

    High-fidelity geomagnetic field intensity determination was carried out using 191 baked fragments collected from 20 kilns or hearths with ages ranging between ∼1200 BC and ∼AD 1725 in South Korea. Geomagnetic field intensity variation displayed three narrow minima at ∼800-700 BC, ∼AD 700, and ∼AD 1600 and two maxima at ∼1200-1100 BC and ∼AD 1000-1100. In most time intervals, virtual axial dipole moment (VADM) variation is confined within 20% of the present VADM. However, geomagnetic field intensity circa 3000 yr ago is nearly 40% larger than the present value. Such high VADMs circa 3000 yr ago are in phase with those in other longitudinal bands in northern hemisphere centered at 5E (France), 30E (the Middle East) and 200E (Hawaii). Although strong geomagnetic field intensity circa 3000 yr ago is globally synchronous, the highest VADM occurs at slightly different time intervals in different locations. Hence it is possible that the globally strong geomagnetic field intensity circa 3000 yr ago reflects the migration of persistent hemispheric flux in northern hemisphere or an episode of geomagnetic field hemispheric asymmetry.

  16. Are migrating raptors guided by a geomagnetic compass?

    USGS Publications Warehouse

    Thorup, Kasper; Fuller, Mark R.; Alerstam, T.; Hake, M.; Kjellen, N.; Standberg, R.

    2006-01-01

    We tested whether routes of raptors migrating over areas with homogeneous topography follow constant geomagnetic courses more or less closely than constant geographical courses. We analysed the routes taken over land of 45 individual raptors tracked by satellite-based radiotelemetry: 25 peregrine falcons, Falco peregrinus, on autumn migration between North and South America, and seven honey buzzards, Pernis apivorus, and 13 ospreys, Pandion haliaetus, on autumn migration between Europe and Africa. Overall, migration directions showed a better agreement with constant geographical than constant geomagnetic courses. Tracks deviated significantly from constant geomagnetic courses, but were not significantly different from geographical courses. After we removed movements directed far from the mean direction, which may not be migratory movements, migration directions still showed a better agreement with constant geographical than constant geomagnetic courses, but the directions of honey buzzards and ospreys were not significantly different from constant geomagnetic courses either. That migration routes of raptors followed by satellite telemetry are in closer accordance with constant geographical compass courses than with constant geomagnetic compass courses may indicate that geographical (e.g. based on celestial cues) rather than magnetic compass mechanisms are of dominating importance for the birds' long-distance orientation.

  17. A Quaternary Geomagnetic Instability Time Scale

    NASA Astrophysics Data System (ADS)

    Singer, B. S.

    2013-12-01

    Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought. Rather, during the Quaternary period, they occur nearly three times as often as full polarity reversals. I will address analytical issues, including the size and consistency of system blanks, that have led to the recognition of minor (1%) discrepencies between the 40Ar/39Ar age for a particular reversal or excursion and the best astrochronologic estimates from ODP sediment cores. For example, re-analysis of lava flows from Haleakala volcano, Maui that record in detail the Matuyama-Brunhes polarity reversal have been undertaken with blanks an order of magntitude smaller and more stable than was common a decade ago. Using the modern astrochronologic calibration of 28.201 Ma for the age of the Fish Canyon sanidine standard, results thus far yield an 40Ar/39Ar age of 772 11 ka for the reversal that is identical to the most precise and accurate astrochronologic age of 773 2 ka for this reversal from ODP cores. Similarly, new dating of sanidine in the Cerro Santa Rosa I rhyolite dome, New Mexico reveals an age of 932 5 ka for the excursion it records, in perfect agreement with astrochronologically dated ODP core records. Work underway aims at refining the 40Ar/39Ar ages that underpin the entire GITS by further eliminating the bias between the radioisotopic and astrochronologically determined ages for several reversals and excursions.

  18. Results of Russian geomagnetic observatories in the 19th century: magnetic activity, 1841-1862

    NASA Astrophysics Data System (ADS)

    Nevanlinna, H.; Hkkinen, L.

    2010-04-01

    Hourly (spot readings) magnetic data (H- and D-components) were digitized from Russian yearbook tables for the years 1850-1862 from four observatories. The pdf pictures for digitization were taken by a normal digital camera. The database obtained consists of about 900 000 single data points. The time series of hourly magnetic values reveal slow secular variations (declination only) as well as transient and regular geomagnetic variations of external origin. The quality and homogeneity of the data is satisfactory. Daily Ak-indices were calculated using the index algorithm that has been earlier applied to 19th century data from Helsinki (Finland) as well as modern magnetic observatory recordings. The activity index series derived from the Russian data is consistent with earlier activity index series for 1850-1862. The digitized index data series derived in this study was extended back to 1841 by including magnetic C9 activity index data available from a Russian observatory (St. Petersburg). Magnetic data rescued here is well suitable for various reconstructions for studies of the long-term variation of the space weather in the 19th century.

  19. Local time dependant response of Indian equatorial ionosphere to the moderate geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Tulasi Ram, S.; Rama Rao, P. V. S.; Prasad, D. S. V. V. D.; Niranjan, K.; Sridharan, R.; Devasia, C. V.; Ravindran, Sudha

    The electrodynamics and neutral dynamics of the equatorial ionosphere undergo significant changes during geo-magnetically disturbed periods as a result of the high and low latitude electro-dynamical coupling. These changes may sometimes trigger the plasma instabilities that lead to the onset of spread-F and scintillations even at the L-band frequencies. The response of the equatorial ionosphere-thermosphere system over the Indian sector to moderate geomagnetic storms of 11th Feb 2004 and 9th Mar 2004 has been studied using the ground based measurements from the Indian equatorial and low latitude region. A large vertical drift of the equatorial F-layer followed by nearly simultaneous onset of Spread-F on ionograms and scintillations at VHF (244 MHz) and L-band (1.5 GHz) frequencies, have been observed during the early evening periods that correspond to the time of rapid decrease (-25 to -30 nT/h) in Sym-H index due to prompt penetration of eastward electric fields into equatorial and low latitudes. The Spread-F and scintillations continued to exist for longer durations up to post-midnight to pre-dawn hours, possibly due to the combined action of prompt penetration and long-lived Disturbance Dynamo electric fields. Due to prolonged geomagnetic activity during the subsequent days (morning-to-noon hours), strong reversal in the Equatorial ElectroJet current is observed and the Equatorial Ionization Anomaly (EIA) is significantly suppressed under the influence of westward disturbance dynamo electric fields. The post-sunset enhancements in the vertical drift of the equatorial F-layer are also reduced significantly from their quiet day patterns and the subsequent occurrence of Spread-F and scintillations is inhibited.

  20. Propagation of the 7 January 2014 CME and Resulting Geomagnetic Non-event

    NASA Astrophysics Data System (ADS)

    Mays, M. L.; Thompson, B. J.; Jian, L. K.; Colaninno, R. C.; Odstrcil, D.; Mstl, C.; Temmer, M.; Savani, N. P.; Collinson, G.; Taktakishvili, A.; MacNeice, P. J.; Zheng, Y.

    2015-10-01

    On 2014 January 7 an X1.2 flare and coronal mass ejection (CME) with a radial speed ?2500 km s?1 was observed from near an active region close to disk center. This led many forecasters to estimate a rapid arrival at Earth (?36 hr) and predict a strong geomagnetic storm. However, only a glancing CME arrival was observed at Earth with a transit time of ?49 hr and a KP geomagnetic index of only 3?. We study the interplanetary propagation of this CME using the ensemble Wang-Sheeley-Arge (WSA)ENLIL+Cone model, that allows a sampling of CME parameter uncertainties. We explore a series of simulations to isolate the effects of the background solar wind solution, CME shape, tilt, location, size, and speed, and the results are compared with observed in situ arrivals at Venus, Earth, and Mars. Our results show that a tilted ellipsoid CME shape improves the initial real-time prediction to better reflect the observed in situ signatures and the geomagnetic storm strength. CME parameters from the Graduated Cylindrical Shell model used as input to WSAENLIL+Cone, along with a tilted ellipsoid cloud shape, improve the arrival-time error by 14.5, 18.7, 23.4 hr for Venus, Earth, and Mars respectively. These results highlight that CME orientation and directionality with respect to observatories play an important role in understanding the propagation of this CME, and for forecasting other glancing CME arrivals. This study also demonstrates the importance of three-dimensional CME fitting made possible by multiple viewpoint imaging.

  1. Investigation of a strong positive ionospheric storm during geomagnetic disturbances occurred in the Brazilian sector

    NASA Astrophysics Data System (ADS)

    de Abreu, A. J.; Sahai, Y.; Fagundes, P. R.; de Jesus, R.; Bittencourt, J. A.; Pillat, V. G.

    2012-12-01

    In this paper, we have investigated the responses of the ionospheric F region at equatorial and low latitude regions in the Brazilian sector during the super geomagnetic storm on 15-16 May 2005. The geomagnetic storm reached a minimum Dst of -263 nT at 0900 UT on 15 May. In this paper, we present vertical total electron content (vTEC) and phase fluctuations (in TECU/min) from Global Positioning System (GPS) observations obtained at Belm (BELE), Braslia (BRAZ), Presidente Prudente (UEPP), and Porto Alegre (POAL), Brazil, during the period 14-17 May 2005. Also, we present ionospheric parameters h'F, hpF2, and foF2, using the Canadian Advanced Digital Ionosonde (CADI) obtained at Palmas (PAL) and So Jos dos Campos (SJC), Brazil, for the same period. The super geomagnetic storm has fast decrease in the Dst index soon after SSC at 0239 UT on 15 May. It is a good possibility of prompt penetration of electric field of magnetospheric origin resulting in uplifting of the F region. The vTEC observations show a trough at BELE and a crest above UEPP, soon after SSC, indicating strengthening of nighttime equatorial anomaly. During the daytime on 15 and 16 May, in the recovery phase, the variations in foF2 at SJC and the vTEC observations, particularly at BRAZ, UEPP, and POAL, show large positive ionospheric storm. There is ESF on the all nights at PAL, in the post-midnight (UT) sector, and phase fluctuations only on the night of 14-15 May at BRAZ, after the SSC. No phase fluctuations are observed at the equatorial station BELE and low latitude stations (BRAZ, UEPP, and POAL) at all other times. This indicates that the plasma bubbles are generated and confined on this magnetically disturbed night only up to the low magnetic latitude and drifted possibly to west.

  2. The influence of manmade noise and geomagnetic fluctuations on seismo-magnetic signatures

    NASA Astrophysics Data System (ADS)

    Prattes, G.; Schwingenschuh, K.; Eichelberger, H. U.; Magnes, W.; Berghofer, G.; Stachel, M.; Besser, B.; Wolbang, D.; Vellante, M.; Villante, U.; Nenovski, P.

    2012-04-01

    In the frame of the South European Geomagnetic Array (SEGMA) chain we investigate the magnetic background with the scientific goal to identify and characterise seismo-magnetic signals. Therefore it is mandatory to differentiate between exogenic (atmospheric / ionospheric / magnetospheric) and endogenic (lithospheric) sources of magnetic variations together with instrumental behaviour. The SEGMA chain consists of five stations spread over mid- and south Europe, data are continuously provided for the last 10 years. The experience has shown that the signal-to-noise ratio of the individual stations depends both on location and time where manmade noise sources have to be considered carefully. Beside the local environments at the SEGMA stations we are considering several geomagnetic indices, e.g. AP-, KP- and DST index. In addition to various geomagnetic signals the possible seismic part of the variations has to be characterised. Reliable results are achieved through the multi-station SEGMA approach in combination with alternative datasets, e.g. from seismic and electromagnetic networks. Earthquake magnitude and distance to the sensors are the most important parameters, the ground conductivity profile is whenever possible, i.e. reliable measurements are available, considered. Long term observations and station comparisons have shown the quality figure of each SEGMA station. The S/N of the L'Aquila station (Italy) was sufficiently high to detect magnetic variations related to the L'Aquila magnitude M=6.3 earthquake, April 6, 2009. In comparison no seismic signals were detected on the other SEGMA stations. We conclude that possible seismic signals can be detected with the SEGMA multi-station network approach if the environmental conditions can be characterised.

  3. [Vulnerability to atmospheric and geomagnetic factors of the body functions in healthy male dwellers of the Russian North].

    PubMed

    Markov, A L; Zenchenko, T A; Solonin, Iu G; Bo?ko, E R

    2013-01-01

    In April 2009 through to November 2011, a Mars-500 satellite study of Russian Northerners (Syktyvkar citizens) was performed using the standard ECOSAN-2007 procedure evaluating the atmospheric and geomagnetic susceptibility of the main body functional parameters. Seventeen essentially healthy men at the age of 25 to 46 years were investigated. Statistical data treatment included correlation and single-factor analysis of variance. Comparison of the number of statistical correlations of the sum of all functional parameters for participants showed that most often they were sensitive to atmospheric pressure, temperature, relative humidity and oxygen partial pressure (29-35 %), and geomagnetic activity (28 %). Dependence of the functional parameters on the rate of temperature and pressure change was weak and comparable with random coincidence (11 %). Among the hemodynamic parameters, systolic pressure was particularly sensitive to space and terrestrial weather variations (29 %); sensitivity of heart rate and diastolic pressure were determined in 25 % and 21 % of participants, respectively. Among the heart rate variability parameters (HRV) the largest number of statistically reliable correlations was determined for the centralization index (32 %) and high-frequency HRV spectrum (31 %); index of the regulatory systems activity was least dependable (19 %). Life index, maximal breath-holding and Ckibinskaya's cardiorespiratory index are also susceptible. Individual responses of the functional parameters to terrestrial and space weather changes varied with partidpants which points to the necessity of individual approach to evaluation of person's reactions to environmental changes. PMID:23814894

  4. Semiannual Variation of Pc-Index for North and South Polar Caps

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Tamara

    Though the semiannual variation of geomagnetic activity with peaks near equinoxes has long been established, its cause is open for discussion. We have suggested earlier a new mechanism for the variation to explain (Adv. Space Res, v. 47, 2011). Phase of the semiannual variation is determined by the annual variation of the geomagnetic moment component My (GSE) caused by sinusoidal oscillations of the moment M at the yz interaction plane during annual motion: extrema at equinoxes (My<0 for the first half of year, My>0 for the second one) and My=0 at the solstices. Amplitude of the annual variation is modulated by the solar wind electric field Ez=VBy. By the other words, annual variation of the My makes extrema at equinoxes that produces maxima of the dawn-dusk component Emv=VByMy at the yz plane at spring equinox for toward polarity of the IMF (By<0, Bx>0) and at fall equinox for away one (By>0, Bx<0). It is logically to search for the semiannual variation of PC-index for north and south polar caps. As is known, the PC index is a measure of the strength of the solar wind electric field derived from magnetic variations measured at a single station near a magnetic pole. We use PC index of south cap Ps, which we could get from the AARS www-page for years 1995, 1998, and Danish north cap Pn for 1975-2012 (Thule. We also use data of the IMF B and wind velocity V measured at 1 a.u. near ecliptic plane for the same years. We show that mean value of E=1 mV/m and mean IMF described by Parker's spiral lies at ecliptic plane. The semiannual variations of both Pn and Ps does not differ from ones of the other indexes (Kp, AA, Dst): smoothed maxima near equinoxes and minima near solstices. As for the other indexes, the spring equinox peak is higher than the fall equinox one. We also obtained annual variations of Ps and Pn for various signs of By. We show that the semiannual variation of both Pn and Ps is determined by the By component. Both Pn and Ps has peak in February-May during the first half of year for By<0, the peak in August-October during the second half one for By>0. The same phase of the statistical semiannual variations of all the indexes is explained by the semiannual variation of the effective dawn-dusk Emv component, which does not depend from ionosphere conductivity and terrestrial induction effects. This Emv variation in turn is caused by the variation of mutual orientation of large-scale electric field E=[VxB] and magnetic moment M in the interaction plane during annual motion of the Earth.

  5. Equatorial airglow and the ionospheric geomagnetic anomaly.

    NASA Technical Reports Server (NTRS)

    Chandra, S.; Reed, E. I.; Troy, B. E., Jr.; Blamont, J. E.

    1973-01-01

    Ogo 4 observations of the O I (6300-A) emissions have revealed a global pattern hitherto undetected from the ground-based observations. It is seen that the postsunset emission of O I (6300 A) in October 1967 is very asymmetrical with respect to the geomagnetic equator in certain longitude regions and shows poor correlation with the electron density measured simultaneously from the same spacecraft. This asymmetry is less marked in the UV airglow, O I (1356 A), which appears to vary as the square of the maximum electron density in the F region. The horizon scan data of the 6300-A airglow reveal that the latitudinal asymmetry is associated with asymmetry in the height of the O I (6300-A) emission and hence with the altitude of the F2 peak. From the correlative studies of the airglow and the ionospheric measurements the mechanisms of the UV and the 6300 A emissions are discussed in terms of the processes involving radiative and dissociative recombination. Theoretical expressions are developed which relate the airglow data to the ionospheric parameters.

  6. Periodic substorm activity in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Huang, C. Y.; Eastman, T. E.; Frank, L. A.; Williams, D. J.

    1983-01-01

    On 19 May 1978 an anusual series of events is observed with the Quadrispherical LEPEDEA on board the ISEE-1 satellite in the Earth's geomagnetic tail. For 13 hours periodic bursts of both ions and electrons are seen in all the particle detectors on the spacecraft. On this day periodic activity is also seen on the ground, where multiple intensifications of the electrojets are observed. At the same time the latitudinal component of the interplanetary magnetic field shows a number of strong southward deflections. It is concluded that an extended period of substorm activity is occurring, which causes repeated thinnings and recoveries of the plasma sheet. These are detected by ISEE, which is situated in the plasma sheet boundary layer, as periodic dropouts and reappearances of the plasma. Comparisons of the observations at ISEE with those at IMP-8, which for a time is engulfed by the plasma sheet, indicate that the activity is relatively localized in spatial extent. For this series of events it is clear that a global approach to magnetospheric dynamics, e.g., reconnection, is inappropriate.

  7. History of the Munich-Maisach-Fürstenfeldbruck Geomagnetic Observatory

    NASA Astrophysics Data System (ADS)

    Soffel, H. C.

    2015-07-01

    The Munich-Maisach-Fürstenfeldbruck Geomagnetic Observatory is one of the observatories with the longest recordings of the geomagnetic field. It started with hourly measurements on 1 August 1840. The founder of the observatory in Munich was Johann von Lamont (1805-1879), the Director of the Royal Bavarian Astronomical Observatory. He had been stimulated to build his own observatory by the initiative of the Göttingen Magnetic Union founded in 1834 by Alexander von Humboldt (1769-1859) and Carl Friedrich Gauss (1777-1855). Before 1840 fewer than five observatories existed; the most prominent ones were those in London and Paris. At the beginning Lamont used equipment delivered by Gauss in Göttingen, but soon started to build instruments of his own design. Among them was a nonmagnetic theodolite which allowed precise geomagnetic measurements to be made also in the field. During the 1850s Lamont carried out geomagnetic surveys and produced geomagnetic maps for Germany and many other European countries. At the end of the nineteenth century accurate geomagnetic measurements in Munich became more and more disturbed by the magnetic stray fields from electric tramways and industry. During this period the quality of the data suffered and the measurements had to be interrupted several times. After a provisional solution in Maisach, a village 25 km west of Munich, a final solution could be found in the vicinity of the nearby city of Fürstenfeldbruck. Here the measurements started again on 1 January 1939. Since the 1980s the observatory has been part of INTERMAGNET, an organization providing almost real-time geomagnetic data of the highest quality.

  8. Solar wind RAM pressure and the geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Vats, H. O.; Sawant, H. S.; Sharma, S.

    The solar flares coronal holes and the coronal mass ejections are the main source of geomagnetic activity The main role is attributed mainly to coronal mass ejections -CMEs There is no simple association between CMEs and flares there are large CMEs without flares and big flares without CMEs Flares and CMEs seem to be part of a single phenomenon a solar eruption and neither one is the cause of the other There have been a number of detailed analyses of geomagnetic contributions due to different solar wind sources and also on the classification of geomagnetic activity according to each solar wind structure Observations from Skylab Helios Ulysses ACE and SOHO have been very useful for the understanding of the Sun - Earth system A set of recent solar events were selected and using the ACE data and geomagnetic observation in the form of Ap Kp and Dst we performed a detailed study of the control of IMF and solar wind parameters on the enhancements of geomagnetic activity It is found that there are three types of events for the enhancement in geomagnetic activity associated with 1 negative or southward Bz 2 oscillatory variation in Bz and 3 positive or northward Bz Here these observations and their implications will be discussed The solar wind RAM pressure on logarithmic scale show almost linear relationship with Kp and not so with other geomagnetic indices The slope of the line is found to be different from event to event Kp enhancement varies from 2 to 6 for a tenfold increase in the solar wind RAM pressure during different solar events

  9. Chaotic appearance of the AE index

    NASA Technical Reports Server (NTRS)

    Shan, L.-H.; Hansen, P.; Goertz, C. K.; Smith, R. A.

    1991-01-01

    Results are reported from a stochastic analysis of a 5-day time series of the geomagnetic AE index during an active period. The original data, the power spectrum, and the autocorrelation function are shown, and the steps in the analysis are described in detail. It is found that the autocorrelation time scale is about 50 min, giving a correlation dimension (for the construction of a time series of m-dimensional vectors) of 2.4. This result is consistent with either colored-noise or deterministic-chaos magnetosphere models, indicating the need for further investigation.

  10. Analyzing the variation of embedding dimension of solar and geomagnetic activity indices during geomagnetic storm time

    NASA Astrophysics Data System (ADS)

    Mirmomeni, M.; Lucas, C.

    2009-02-01

    Cyclic solar activity as one of the natural chaotic phenomena has significant effects on Earth, climate, and satellites. Rapid changes in the near-Earth space environment can affect the performance and reliability of both spacecraft and ground-based systems. This can imply major problems due to communication and satellite operational anomalies. Therefore, it is meaningful to analyze solar activity and geomagnetic indices to elicit the behavior of sun as the origin of most of these chaotic phenomena. One of the most important tools for analyzing the chaotic trends is the "Embedding Dimension" (ED). In this paper, the variation of ED for solar activity indices especially during storm time for two well-known storms is considered. The first storm is the super-storm on 13 March 1989, which shuts down the power supply system in Qubec, Canada and the second one is the storm caused by Coronal Mass Ejection on 11 January 1997 which causes the failure of Telstar 401 satellite. The method of this paper is based on the fact that the reconstructed dynamics of an attractor should be a smooth map, i.e. with no self intersection in the reconstructed attractor. It is shown that the Embedding Dimension (and other chaotic characteristics) of some solar and geomagnetic activity indices during these storms varies rapidly.

  11. Direct-Chill Co-Casting of AA3003/AA4045 Aluminum Ingots via Fusion Technology

    NASA Astrophysics Data System (ADS)

    Caron, Etienne J. F. R.; Pelayo, Rosa E. Ortega; Baserinia, Amir R.; Wells, Mary A.; Weckman, David C.; Barker, Simon; Gallerneault, Mark

    2014-06-01

    Laboratory-scale experiments were conducted to cast AA3003/AA4045 clad ingots via Fusion Technology, a novel process developed by Novelis Inc. for the production of aluminum clad materials such as brazing sheet. Experimental results were used to validate a steady-state thermofluids model of the Fusion Technology co-casting process. The numerical model was able to accurately predict the temperature field within the AA3003/AA4045 clad ingot as well as the shape of the AA3003 liquid sump. The model was also used to quantify the temperature, fraction solid, and velocity fields in a clad ingot cast with an asymmetrical molten metal-feeding system. Feeding of core and clad molten metals at opposite corners of the mold was found to reduce the risks of hot spots and liquid metal breakthrough from the core sump to the clad side of the Fusion Technology mold. The use of a diffuser for the AA3003 core molten metal and of a vertical feeding tube for the AA4045 clad produced different flow patterns and liquid sump shapes on either side of the mold. The quality of the metallurgical bond at the core/clad interface appeared good near the clad inlet and at the ingot centerline, but poor near the edges of the ingot. SEM-EDS analysis of the chemical composition across the interface showed that a 1 to 20- ?m-deep penetration of silicon from the AA4045 clad into the AA3003 core had occurred at visually acceptable interfaces, whereas silicon diffusion across poor interfaces was very limited. A study of the model-predicted fraction solid history at different points along the interface indicated that reheating of the AA3003 core is not required to form a visually acceptable metallurgical bond. However, a sufficient amount of interaction time between the solid AA3003 core shell and the silicon-rich AA4045 clad liquid is required to chemically dissolve the surface of the core and form a good metallurgical bond. An approximate dissolution depth of 750 to 1000 ?m was observed along the visually good interface. Partial dissolution of the Mn-rich AA3003 core led to the formation of Al(Mn,Fe)Si intermetallic particles in the AA4045 clad and an increased manganese concentration near the core/clad interface.

  12. INDEX OF ENGLISH EQUIVALENTS FOR THE BASIC (SPOKEN) GERMAN WORD LIST.

    ERIC Educational Resources Information Center

    PFEFFER, J. ALAN

    THIS BOOK WAS PREPARED TO PROVIDE AN INDEX OF ENGLISH EQUIVALENTS FOR THE BASIC SPOKEN GERMAN WORD LIST BY THE AUTHOR. THE ENGLISH MEANINGS OF EACH GERMAN TERM ARE PRESENTED IN ORDER OF DECREASING FREQUENCY. THIS BOOK WAS PUBLISHED BY PRENTICE-HALL INC., ENGLEWOOD CLIFFS, NEW JERSEY 07632, 1965, 107 PAGES. RELATED REPORTS ARE AA 000 101 AND AA 000…

  13. Variations of the mid-latitude ionosphere during strong geomagnetic storms: Observational results

    NASA Astrophysics Data System (ADS)

    Gordiyenko, Galina; Vodyannikov, Victor; Yakovets, Artur

    The ground-based ionosonde data obtained at Alma-Ata station [ϕ = 43.250N, λ = 76.920E, Φ = 33.470N, L = 1.44) are analyzed to study ionospheric responses at fourteen intense (Kp ≥ 8) geomagnetic storms with storm sudden commencement (ssc). The collected data show that ionospheric responses to intensive geomagnetic storms (Dst < -100nT ) are very complex with a great degree of variability; however, negative ionospheric disturbances are a common feature of the responses. The time delay between storm ssc and beginning of the negative ionospheric disturbances shows a tendency to be noticeably larger in winter events than the summer events. Positive ionospheric effects are observed during storm recovery phases or when the Dst almost fully recovered; an enhanced eastward electric field occurred at low and equatorial latitudes after ssc is assumed to be a possible reason for the effects. The occurrence of the unusual for Alma-Ata location night E, F1 layers and auroral type r (retardation) sporadic Es layers is observed during developing or around main phases in Dst index. Employing the International Reference Ionosphere 2001 (IRI-2001), the nighttime E region electron density has been estimated for

  14. Geomagnetic lunar and solar daily variations during the last 100 years

    NASA Astrophysics Data System (ADS)

    Yamazaki, Y.; Kosch, M. J.

    2014-08-01

    This paper describes long-term changes in the geomagnetic lunar (L) and solar (S) daily variations. We analyze the eastward component of the geomagnetic field observed at eight midlatitude stations during 1903-2012. The amplitude and phase for the semidiurnal component of the L and S variations are examined. Both L and S amplitudes correlate with the solar activity index F10.7, revealing a prominent 11 year solar cycle. In both cases, the correlation is slightly better with √(F10.7) than F10.7. The sensitivity of the L variation to solar activity is comparable with that of the S variation. The solar cycle effect is also found in the phase of the S variation but not apparent in the phase of the L variation. The ratio in the amplitude of the L to S variation shows a long-term decrease (approximately 10% per century), which may be due to a reduction in lunar tidal waves from the lower atmosphere to the upper atmosphere in association with climate change.

  15. Associations by signatures and coherences between the human circulation and helio- and geomagnetic activity.

    PubMed

    Watanabe, Y; Cornlissen, G; Halberg, F; Otsuka, K; Ohkawa, S I

    2001-01-01

    Helio-geomagnetic influences on the human circulation are investigated on the basis of an 11-year-long record from a clinically healthy cardiologist, 35 years of age at the start of monitoring. He measured his blood pressure and heart rate around the clock with an ambulatory monitor programmed to inflate an arm cuff, mostly at intervals of 15-30 minutes, with only few interruptions, starting in August 1987. While monitoring is continuing, data collected up to July 1998 are analyzed herein by cosinor rhythmometry and cross-spectral coherence with matching records of solar activity, gauged by Wolf numbers (WN) and of the geomagnetic disturbance index, Kp. A direct association between heart rate (HR) and WN is found to be solar cycle stage-dependent, whereas an inverse relationship between heart rate variability (HRV) and WN is found consistently. An inverse relation is also observed between WN and the variability in systolic blood pressure (SBP), and to a lesser extent, diastolic blood pressure (DBP). Moreover, HR is cross-spectrally coherent with WN at a frequency of one cycle in about 7.33 months. The results support previously reported associations on morbidity and mortality statistics, extending their scope to human physiology monitored longitudinally. PMID:11774871

  16. Statistical analysis of the ionospheric response during geomagnetic storm conditions over South Africa using ionosonde and GPS data

    NASA Astrophysics Data System (ADS)

    Matamba, Tshimangadzo Merline; Habarulema, John Bosco; McKinnell, Lee-Anne

    2015-09-01

    This paper presents a statistical analysis of ionospheric response over ionosonde stations Grahamstown (33.3°S, 26.5°E, geographic) and Madimbo (22.4°S, 30.9°E, geographic), South Africa, during geomagnetic storm conditions which occurred during the period 1996-2011. Such a climatological study is important in establishing local ionospheric behavior trend which later forms a basis for accurate modeling and forecasting electron density and critical frequency of the F2 layer (foF2) useful for high-frequency communication. The analysis was done using foF2 and total electron content (TEC), and to identify the geomagnetically disturbed conditions, the Dst index with a storm criterion of Dst ≤ nT was used. Results show a strong solar cycle dependence with negative ionospheric storm effects following the solar cycle and positive ionospheric storm effects occurring most frequently during solar minimum. Seasonally, negative and positive ionospheric storm effects occurred most in summer (63.24%) and in winter (53.62%), respectively. An important finding is that only negative ionospheric storms were observed during great geomagnetic storm activity (Dst ≤ nT). For periods when both foF2 and TEC data (from colocated ionosonde and GPS receiver stations) were available, a similar response in terms of variational trend was observed. Hence, GPS data can be used to effectively identify the ionospheric response in the absence of ionosonde data.

  17. Low Latitude Pulsations Associated with Different Phases of Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Bulusu, J.; Vankayala, R. C.; Sinha, A. K.; Vichare, G.; Thomas, N.

    2014-12-01

    During geomagnetic storm lot of free energy is available in the magnetosphere and this energy can act as feeder to electromagnetic waves in different frequency bands. A classical geomagnetic storm consists mainly of four phases i.e. SSC (Sudden Storm commencement), initial Phase, main phase and recovery phase. In this paper, we investigate the characteristics of electromagnetic waves in ULF (ultra low frequency) band associated with different phases of geomagnetic storms. Electromagnetic waves in ULF band (Period~ 10-100s) in the Earth's magnetosphere are generally termed as geomagnetic pulsations. A detailed statistical analysis has been performed over ten years of geomagnetic data from low latitude ground stations in Indian and Japanese sectors. The study reveals that storms in general, are accompanied with continuous pulsations of different frequency bands during different phases. In particular, the main phase of 91 % of intense storms was accompanied with pulsations in Pc5 band (frequency~ 2-7 mHz). However, the occurrence of these pulsations was less frequent during main phase of weak to moderate storms. Further, the amplitude of these pulsations increased with the intensity of storm.

  18. The Geomagnetic Control Concept of The Ionospheric Long- Term Trends

    NASA Astrophysics Data System (ADS)

    Mikhailov, A. V.

    The geomagnetic control concept has been developed to explain long-term trends of the electron concentration in the F2 and E ionospheric regions. Periods with negative and positive foF2, hmF2 and foE trends correspond to the periods of increasing or decreasing geomagnetic activity with the turning points around the end of 1950s, 1960s, and 1980s where trends change their signs. Strong latitudinal and diurnal variations revealed for the foF2 and hmF2 trends can be explained by neutral composition, temperature and thermospheric wind changes. Particle precipitation is important in the auroral zone. The newly proposed concept proceeds from a natural origin of the F2-layer trends rather than an artificial one related to the greenhouse effect. Using the proposed method a very long-term foF2 and foE trends related with general increase of geomagnetic activity in the 20th century has been revealed for the first time. The firstly revealed relationship of the foE trends with geomagnetic activity is due to nitric oxide variations at the E-region heights. This "natural" relationship of the foE trends with geomagnetic activity breaks down around 1970 on many stations presumably due to chemical polution of the upper atmosphere. The increasing rate of rocket and satellite launchings in the late 1960s is considered as a reason.

  19. Study of Proton cutoffs during geomagnetically disturbed times

    NASA Astrophysics Data System (ADS)

    Kanekal, S. G.; Looper, M. D.; Baker, D. N.; Blake, J. B.

    Solar energetic particles SEP are currently classified into impulsive and gradual events The former are understood be accelerated at solar flares and the latter at interplanetary shocks driven by coronal mass ejections CMEs It is well known that CMEs also cause intense geomagnetic storms during which the geomagnetic field can be highly distorted During these times SEP fluxes penetrate the terrestrial magnetosphere and reach regions which may not be normally accessible to them The SEP access is of course controlled by the geomagnetic field configuration The cutoff latitude is a well defined latitude below which a charged particle of a given rigidity momentum per unit charge arriving from a given direction cannot penetrate SEPs constitute a radiation hazard to spacecraft and humans and measurement and prediction of the cutoff location are an important aspect of space weather This paper reports on the measurements of solar energetic proton cutoffs made by two satellites SAMPEX and Polar during geomagnetically disturbed times We study select SEP events occuring during the period 1996 to 2005 when both SAMPEX and Polar provide high quality data We will compare our measurements with cutoffs calculated by a charged particle tracing code which utilizes several currently used models of the geomagnetic field The measured SEP proton cutoffs cover a range of rigidities and are obtained at high-altitudes by the HIST detector onboard Polar and at low-altitudes by the PET and HILT detctors onboard SAMPEX

  20. The AAS: Its Next 100 Years

    NASA Astrophysics Data System (ADS)

    Wolff, S.

    1999-05-01

    The AAS: Its Next Hundred Years "We are probably nearing the limit of all we can know about astronomy."-- Simon Newcomb, 1888. The best way to celebrate the centennial of the AAS is to look forward, not backward, and to begin planning for the next 100 years. However, predicting the future is even more difficult than it was in Newcomb's time. We live in an era characterized by an unprecedented rate of change in the kinds of scientific questions we ask, the tools we use to answer them, and the way we communicate our results. This talk will highlight some of the issues that we will face as a community during the next 10--but not the next 100!--years and suggests that the AAS has a fundamental role to play in shaping the community response to these issues.

  1. Airport geomagnetic surveys in the United States

    USGS Publications Warehouse

    Berarducci, A.

    2006-01-01

    The Federal Aviation Administration (FAA) and the United States military have requirements for design, location, and construction of compass calibration pads (compass roses), these having been developed through collaboration with US Geological Survey (USGS) personnel. These requirements are detailed in the FAA Advisory Circular AC 150/5300-13, Appendix 4, and in various military documents, such as Handbook 1021/1, but the major requirement is that the range of declination measured within 75 meters of the center of a compass rose be less than or equal to 30 minutes of arc. The USGS Geomagnetism Group has developed specific methods for conducting a magnetic survey so that existing compass roses can be judged in terms of the needed standards and also that new sites can be evaluated for their suitability as potentially new compass roses. First, a preliminary survey is performed with a total-field magnetometer, with differences over the site area of less than 75nT being sufficient to warrant additional, more detailed surveying. Next, a number of survey points are established over the compass rose area and nearby, where declination is to be measured with an instrument capable of measuring declination to within 1 minute of arc, such as a Gurley transit magnetometer, DI Flux theodolite magnetometer, or Wild T-0. The data are corrected for diurnal and irregular effects of the magnetic field and declination is determined for each survey point, as well as declination range and average of the entire compass rose site. Altogether, a typical survey takes about four days to complete. ?? 2006 Springer.

  2. Dynamical similarity of geomagnetic field reversals.

    PubMed

    Valet, Jean-Pierre; Fournier, Alexandre; Courtillot, Vincent; Herrero-Bervera, Emilio

    2012-10-01

    No consensus has been reached so far on the properties of the geomagnetic field during reversals or on the main features that might reveal its dynamics. A main characteristic of the reversing field is a large decrease in the axial dipole and the dominant role of non-dipole components. Other features strongly depend on whether they are derived from sedimentary or volcanic records. Only thermal remanent magnetization of lava flows can capture faithful records of a rapidly varying non-dipole field, but, because of episodic volcanic activity, sequences of overlying flows yield incomplete records. Here we show that the ten most detailed volcanic records of reversals can be matched in a very satisfactory way, under the assumption of a common duration, revealing common dynamical characteristics. We infer that the reversal process has remained unchanged, with the same time constants and durations, at least since 180 million years ago. We propose that the reversing field is characterized by three successive phases: a precursory event, a 180° polarity switch and a rebound. The first and third phases reflect the emergence of the non-dipole field with large-amplitude secular variation. They are rarely both recorded at the same site owing to the rapidly changing field geometry and last for less than 2,500 years. The actual transit between the two polarities does not last longer than 1,000 years and might therefore result from mechanisms other than those governing normal secular variation. Such changes are too brief to be accurately recorded by most sediments. PMID:23038471

  3. Quasi-biennial geomagnetic variation caused by the sun

    NASA Technical Reports Server (NTRS)

    Sugiura, M.

    1976-01-01

    Clear evidence for the existence of a quasi-biennial geomagnetic variation is shown by an analysis of annual averages of the horizontal (H) component of the geomagnetic field observed at five observatories. The analysis uses a numerical filter, which is equivalent to taking the second order time derivative of the time series. The cause for the variation is external to the earth because its amplitude depends on magnetic activity. The second order time derivative of H is well correlated with the corresponding time derivatives of the relative sunspot number and 10.7 cm solar flux. It is suggested that quasi-biennial oscillations observed in the geomagnetic field, cosmic rays, stratospheric zonal wind and temperature, total ozone, and other meteorological parameters could be produced by a common cause on the sun.

  4. The component compensation of geomagnetic field vector measurement system

    NASA Astrophysics Data System (ADS)

    Pang, Hongfeng; Zhu, Xue Jun; Pan, Mengchun; Zhang, Qi; Wan, Chengbiao; Luo, Shitu; Chen, Jinfei; Li, Ji; Lv, Yunxiao; Chen, Dixiang

    2015-05-01

    Magnetic field distortion of INS is the major factor influencing the accuracy of geomagnetic field information measurement system. Simulation and experiment results show that traditional scalar compensation methods are disabled for component compensation. A component compensation method is proposed, in which parallelepiped frame and perpendicular platform are used with designed operation process. Comparing with traditional methods, the component compensation method is effective for distortion parameter estimation, and it shows better component compensation performance. Experimental test result demonstrates that distortion field components of INS are suppressed approximately two orders after compensation, and the North, Vertical and East component measurement error of the geomagnetic field are reduced to 2.3%, 3.3% and 4.5% of the former values respectively. Declination error is reduced from 7.074° to 0.331° (4.6% of the former value). This compensation method contributes to the accuracy improvement of geomagnetic field vector measurement system.

  5. Anomalous propagation of Omega VLF waves near the geomagnetic equator

    NASA Astrophysics Data System (ADS)

    Ohtani, A.; Kikuchi, T.; Nozaki, K.; Kurihara, N.; Kuratani, Y.; Ohse, M.

    1983-09-01

    Omega HAIKU, REUNION, and LIBERIA signals were received and anomalous propagation characteristics were obtained near the geomagnetic equator. Short-period fluctuations were found in the phase of the HAIKU 10.2 kHz signal in November 1979 and in the phase and amplitude of the HAIKU 13.6 kHz signal in November 1981. These cyclic fluctuations are in close correlation with the phase cycle slippings, which occur most frequently when the receiver is located at 6 S geomagnetic latitude. On the basis of anisotropic waveguide mode theory indicating much less attenuation in WE propagation than in EW propagation at the geomagnetic equator, it is concluded that the short-period fluctuations in the phase and amplitude are due to interference between the short-path and the long-path signals.

  6. Geomagnetic observations on tristan da cunha, south atlantic ocean

    USGS Publications Warehouse

    Matzka, J.; Olsen, N.; Maule, C.F.; Pedersen, L.W.; Berarducci, A.M.; Macmillan, S.

    2009-01-01

    Few geomagnetic ground observations exist of the Earth's strongest core field anomaly, the South Atlantic Anomaly (SAA). The geomagnetic repeat station on the island Tristan da Cunha, located half-way between South Africa and South America at 37?? 05' S, 12?? 18' W, is therefore of crucial importance. We have conducted several sets of repeat station measurements during magnetically quiet conditions (Kp 2o or less) in 2004. The procedures are described and the results are compared to those from earlier campaigns and to the predictions of various global field models. Features of the local crustal bias field and the solar quiet daily variation are discussed. We also evaluate the benefit of continuous magnetic field recordings from Tristan da Cunha, and argue that such a data set is a very valuable addition to geomagnetic satellite data. Recently, funds were set up to establish and operate a magnetometer station on Tristan da Cunha during the Swarm magnetic satellite mission (2011-2014).

  7. Application of copper slag in geomagnetic archaeointensity research

    NASA Astrophysics Data System (ADS)

    Ben-Yosef, E.; Ron, H.; Tauxe, L.; Agnon, A.; Genevey, A.; Levy, T. E.; Avner, U.; Najjar, M.

    2008-08-01

    Paleointensity and archaeointensity studies since the 1950s have produced numerous geomagnetic intensity data for the last seven millennia. As a consequence of different experiments and materials, there is a complex and internally inconsistent picture of the geomagnetic field behavior. In this study we present data using a recently developed experimental design on a heretofore unexploited recording medium: copper slag deposits. Our results, based on hundreds of specimens from various archaeometallurgical sites of the Southern Levant, demonstrate the applicability of copper slag material for archaeointensity studies. In addition to frequently exhibiting good experimental behavior, slag has further advantages such as dense multilayer deposits and in cases embedded charcoals, which open the door to data sets with excellent age control and resolution. The data presented here augment the high quality database from the Middle East and support previously observed periods of rapid change of the intensity of the geomagnetic field.

  8. Solstitial and hemispherical asymmetry in the response of geomagnetic field

    NASA Technical Reports Server (NTRS)

    Shah, G. N.; Kaul, R. K.; Kaul, C. L.; Razdan, H.; Merryfield, W. J.; Wilcox, J. M.

    1984-01-01

    It is shown that the geomagnetic field is more prone to disturbances around the June solstice than around the December solstice, as evidenced from a larger enhancement in geomagnetic activity indices, ap, an, and as, following the onset of transient solar disturbances occurring in the thee-month period around June solstice than in the interval around the December solstice. Further, an asymmetry between the northern and southern hemisphere geomagnetic activity is shown to exist, independent of the level of the activity. This asymmetry, represented by (an - as)/(an + as)/2 shows a regular annual variation with a maximum of 60 percent around the June solstice and is almost absent around the December solstice.

  9. Thermospheric heating away from the auroral oval during geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Burns, A. G.; Killeen, T. L.; Roble, R. G.

    1992-01-01

    The data on the morphology of the changes in the heating of thermosphere in the middle and high latitudes during geomagnetic storms, collected by the DE-2 satellite between July 1981 and February 1983 are compared with the NCAR-Thermosphere-Ionosphere General Circulation Model simulation of the November 24, 1982 storm on a one-on-one basis for an individual orbit in the middle of this storm. Good agreement was found for the winter hemisphere. A thermodynamic diagnostic processor was then used to investigate the mechanism by which geomagnetic storms cause temperature increases at lower latitudes. It was found that the pattern of heating during geomagnetic storms is complex, indicative of the complex nature of the physical processes that alter the thermal structure of the thermosphere at these times. Model predictions indicated that the greatest temperature increase at 40 deg N occurs in the morning, in agreement with results of Proelss (1984).

  10. SMART analysis of geomagnetic data observed in Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Liu, J. Y.; Yang, W. H.; Yen, H. Y.; Hattori, K.; Lin, C. R.; Yeh, Y. H.

    In this paper, 3-component geomagnetic fields recorded by a fluxgate magnetometer are employed in examining 181 ML ≧ 4.0 earthquakes around the Taiwan area from 2002 to 2005. To search anomalies, the singular value decomposition (SVD) is used to extract the declinations and inclinations of the principal components from the geomagnetic field every 900 s for each 5-day period and the entire four years. Six reference angles of surface magnetic anomaly reference tip (SMART) are employed to readjust the azimuth of anomalous polarizations for unifying earthquakes. A bootstrap method is further applied to find whether the anomalies are significant or not. Meanwhile, the odds proportions between the inward and outward geomagnetic field on the earth’s surface reveal the associated anomalous inclinations. With the anomalous inclinations and declinations observed 10 days before earthquakes, SMART and the polarizations of the anomalous field can be located and described, respectively.

  11. Report of geomagnetic pulsation indices for space weather applications

    USGS Publications Warehouse

    Xu, Z.; Gannon, Jennifer L.; Rigler, Erin J.

    2013-01-01

    The phenomenon of ultra-low frequency geomagnetic pulsations was first observed in the ground-based measurements of the 1859 Carrington Event and has been studied for over 100 years. Pulsation frequency is considered to be ultra low when it is lower than the natural frequencies of the plasma, such as the ion gyrofrequency. Ultra-low frequency pulsations are considered a source of noise in some geophysical analysis techniques, such as aeromagnetic surveys and transient electromagnetics, so it is critical to develop near real-time space weather products to monitor these geomagnetic pulsations. The proper spectral analysis of magnetometer data, such as using wavelet analysis techniques, can also be important to Geomagnetically Induced Current risk assessment.

  12. Solar coronal holes as sources of recurrent geomagnetic disturbances

    NASA Technical Reports Server (NTRS)

    Neupert, W. M.; Pizzo, V.

    1974-01-01

    Observations of the solar corona by Oso 7 have been used in a superposed epoch analysis to study the relationships between classes of coronal features and geomagnetic activity. Both bright coronal regions and regions of less than average brightness were investigated. It was found that for the period from January 1972 through January 1973, a significant enhancement in geomagnetic activity occurred 2-3 days after central meridian passage of large coronal holes that extended to within 5 deg of the solar subearth point when they were on the meridian. Large coronal holes appear to satisfy the requirements for 'M regions' which were hypothesized to be responsible for recurrent geomagnetic disturbances (Bartels, 1934). If solar wind high-speed streams originate preferentially in these regions, their velocity at the base of the corona will be substantially higher than that expected from an axisymmetric solar wind model.

  13. Extreme geomagnetic disturbances due to shocks within CMEs

    NASA Astrophysics Data System (ADS)

    Lugaz, N.; Farrugia, C. J.; Huang, C.-L.; Spence, H. E.

    2015-06-01

    We report on features of solar wind-magnetosphere coupling elicited by shocks propagating through coronal mass ejections (CMEs) by analyzing the intense geomagnetic storm of 6 August 1998. During this event, the dynamic pressure enhancement at the shock combined with a simultaneous increase in the southward component of the magnetic field resulted in a large earthward retreat of Earth's magnetopause, which remained close to geosynchronous orbit for more than 4 h. This occurred despite the fact that both shock and CME were weak and relatively slow. Another similar example of a weak shock inside a slow CME resulting in an intense geomagnetic storm is the 30 September 2012 event, which strongly depleted the outer radiation belt. We discuss the potential of shocks inside CMEs to cause large geomagnetic effects at Earth, including magnetopause shadowing.

  14. The geomagnetic elements in Denmark 1928-1980

    NASA Astrophysics Data System (ADS)

    Hansen, H. A.

    Geomagnetic surveys in Denmark from 1928 till 1980 are reported. The Danish Meteorological Institute initiated a new, geomagnetic survey of Denmark in 1928 by the establishment of 10 repeat statins for observation of the geomagnetic, secular variation. The stations were visited again in 1930 and since then every fifth year. The general survey was started in 1939 and continued during the years 1946 to 1957 with the mapping of Northern Jutland. In 1967 the survey taken with a coarser spacing of the measured points during the following years succeeded in completing the mapping of the country with primary consideration to the declination. The observations on the repeat stations during the time 1928-1980 allowed development of mathematical formulas for the secular change of the magnetic elements D, H and Z at any arbitrary point in the country.

  15. Stratospheric warmings and the geomagnetic lunar tide: 1958-2007

    NASA Astrophysics Data System (ADS)

    Yamazaki, Y.; Richmond, A. D.; Yumoto, K.

    2012-04-01

    A quantitative comparison of the geomagnetic lunar tide and lower stratospheric parameters (zonal mean air temperature T and zonal mean zonal wind U) is carried out for the period 1958-2007. The correlation between the amplitude of the geomagnetic lunar tide at an equatorial station, Addis Ababa, and the lower stratospheric parameters from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis is examined. It is found that the lunar tidal amplitude tends to be positively and negatively correlated with the stratospheric T and U, respectively, in high latitudes of the Northern Hemisphere during December and January. High correlations are observed in approximately 70% of stratospheric sudden warming (SSW) events. The results suggest that variability of the geomagnetic lunar tide during the northern winter is closely linked with dynamical changes in the lower stratospheric parameters associated with SSWs.

  16. 77 FR 22312 - Geomagnetic Disturbances to the Bulk-Power System; Notice of Technical Conference

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-13

    ... Energy Regulatory Commission Geomagnetic Disturbances to the Bulk-Power System; Notice of Technical... Conference on Geomagnetic Disturbances to the Bulk-Power System on Monday, April 30, 2012, from 11 a.m. to 4... issues related to reliability of the Bulk-Power System as affected by geomagnetic disturbances....

  17. Investigations on geomagnetic secular variation anomalies through tectonomagnetic monitoring in the seismoactive zone of the Narmada-Son Lineament, Central India

    NASA Astrophysics Data System (ADS)

    Waghmare, S. Y.

    2009-12-01

    Data from repeated geomagnetic observations at exactly same location on the five profiles i.e. Katangi-Mandla (AA'), Mandla-Lakhnadon (BB'), Lakhnadon-Narsimhapur (CC'), Narsimhapur-Jabalpur (DD') and Jabalpur-Seoni (EE') have revealed secular variation of the total geomagnetic field in the tectonically/seismically active zone of the Narmada-Son Lineament (NSL), Central India. The seismicity in NSL, associated with the activation of boundary fault near Jabalpur, might have been responsible for the release of stress accumulated due to continuous northward movement of the Indian plate. The external magnetic field contributions (ionospheric/magnetospheric currents) as well as internal (secular trend of main field due to Earth's core electric currents) have been eliminated due to the operation of the reference base station within study area at Seismic Observatory Jabalpur. Proton Precession Magnetometers (PPMs) with sensitivity 0.1 nT were used simultaneously for measuring the total geomagnetic field intensity at the repeated-survey stations and reference station. The survey sites were visited annually wherein seven cycles of repeated observations were performed from 2003 to 2009. The simple difference method was used in data analysis and the residuals have been calculated as secular variations of the total geomagnetic field with values ranging from 0.1 nT/yr to 9.5 nT/yr at different stations. However, measurable seismic activity was not registered during the repeated survey period. It is proposed that secular changes originate from stress and tension on the NSL fault system and crustal blocks as a tectonomagnetic effect. However, the Geomagnetic Depth Sounding (GDS) experiment in Jabalpur area revealed high electrical conductivity anomaly (Satpura conductor) which has been interpreted due to fluids/saline water in the crust. There is a possibility for the fluids to flow through the porous rocks thereby generating electric currents to produce the electrokinetic effect, which may also have contributed to anomalies in the secular variation. The remarkable changes in the total intensity of the geomagnetic field observed on five profiles indicate the piezomagnetic and/or electrokinetic effect or, both these mechanisms seem to be operative for the secular variation anomalies in the seismoactive zone of NSL.

  18. Observed effects of a geomagnetic storm on an RTK positioning network at high latitudes

    NASA Astrophysics Data System (ADS)

    Jacobsen, Knut Stanley; Schfer, Sebastian

    2012-08-01

    At high latitudes, above 60 N, in the vicinity of the auroral oval, the ionosphere frequently experiences disturbed conditions that impact GNSS-based services. The Norwegian Mapping Authority (NMA) is operating a national real-time kinematic (RTK) positioning network and an ionosphere monitoring software. This paper presents the ionospheric observations during a geomagnetic storm, and the observed consequences for the positioning service. Significant disruptions that can be clearly related to the ionospheric disturbances were observed. They tend to occur in roughly longitudinal bands, which is expected for disturbances caused by the particle and energy precipitation in the auroral oval. The position error is found to increase exponentially with increasing rate of TEC index (ROTI). The disturbances are compared to auroral electrojet measurements and results from an operational auroral oval forecasting model. The disturbances are found to be strongly related to auroral electrojet currents.

  19. Observation of low energy protons in the geomagnetic tail at lunar distances. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Hardy, D. A.

    1974-01-01

    Three suprathermal ion detectors stationed on the moon were used to detect a region of plasma flowing antisunward along the ordered field lines of the geomagnetic tail, exterior to the plasma sheet. The particle flow displays an integral flux, a bulk velocity, temperatures, and number densities uniquely different from the other particle regimes traversed by the moon. No consistent deviation in the field was found to correspond with the occurrence of the events, which have an angular distribution extending between 50 and 100 deg and a spatial distribution over a wide region in both the Y sub sm and Z sub sm directions. The duration of observable particles varies widely between tail passages, with an apparent correlation between the number of hours of observation and the Kp index averages over these times. It is proposed that these particles may have entered through the cusp region.

  20. Investigation of the responses of the general circulation at 700 mb to solar-geomagnetic disturbance

    NASA Technical Reports Server (NTRS)

    Stolov, H. L.; Shapiro, R.

    1973-01-01

    The Northern Hemisphere 700 mb contour heights from 20 N to 70 N for the period 1947-1970 are studied in conjunction with 272 key days, where the daily increase of the Ci index equals or exceeds 1.0. The superposed epoch method is applied from 33 days before to 66 days after the key day for a variety of zonal and meridional indices. It is shown that the 700 mb height difference between 20 N and 55 N increases significantly in winter 4 days following geomagnetic disturbance (in summer a less prominent but statistically significant increase is found 2 days earlier). The effect is most clear in winter in the quadrant 90-175 W and corresponds to a 7% increase in the mean geostrophic westerly flow. The statistical significance of the results is established by applying Student's t-test to the difference of each daily mean from the continuum.

  1. Geomagnetic, cosmogenic and climatic changes across the last geomagnetic reversal from Equatorial Indian Ocean sediments

    NASA Astrophysics Data System (ADS)

    Valet, Jean-Pierre; Bassinot, Franck; Bouilloux, Alexandra; Bourls, Didier; Nomade, Sbastien; Guillou, Valry; Lopes, Fernand; Thouveny, Nicolas; Dewilde, Fabien

    2014-07-01

    High-resolution records of beryllium (10Be) production and relative paleointensity have been obtained across the Matuyama-Brunhes (M-B) reversal from the equatorial Indian Ocean (Maldives area). Both magnetic and geochemical analyses were performed from the same discrete samples to avoid any artificial depth offset. The authigenic 10Be concentrations were normalized with respect to 9Be in order to correct for potential environmental effects, while the relative paleointensity was derived from the remanent magnetization intensity after accounting for changes in magnetic concentration within the sediment. The relative paleointensity and the 10Be/9Be records are both characterized by large deviations, which culminate in the middle of the reversal. In contrast to most previous studies, and despite relative high deposition rate (4.7 cm/ka), we observed a perfect synchronism between the 10Be/9Be peak, the lowest value of relative paleointensity and the switch in direction, which indicates that bioturbation and post-depositional processes did not affect the magnetic record. This leaves no ambiguity for the stratigraphic position of the reversal located within Marine Isotopic Stage 19 as revealed by the planktonic ?18O record from the same core. The magnetic data depict a two-phase process with a precursory event preceding the rapid polarity switch, while only the second phase is present in the 10Be record, similarly to other low latitude records from the Indonesian area. Using an orbitally-tuned age model, we obtain an age of 772 ka5 ka for the middle of the transition, while the precursory event occurred almost 20 ka before. We believe that the bimodal distribution emerging from the compilations of the ages of the M-B reversal results from the succession of these two events. Microtektites from the Australasian impact were found at 0.6 m below the transition (790 ka5 ka B.P.) and confirm that this large event occurred 12 ka prior to the polarity transition. The distribution of tektite abundance was used to deconvolve the 10Be/9Be signal. The results confirm that the beryllium changes are concentrated during the transitional period, thus likely in presence of a multipolar geomagnetic field (or in the vicinity of a geomagnetic pole) that favored the penetration of cosmic rays and consequently increased the 10Be production. The absence of 10Be during the precursor indicates that the present site and the Indonesian ones were far away from a geomagnetic pole and that interlatitudinal atmospheric mixing was limited. The geomagnetic pole positions above the Indonesian sites during the precursor would thus be incompatible with the corresponding inclined dipolar field during this period, and suggest the dominance of low-degree harmonics.

  2. Evidence for a new geomagnetic jerk in 2014

    NASA Astrophysics Data System (ADS)

    Torta, J. Miquel; Pavón-Carrasco, F. Javier; Marsal, Santiago; Finlay, Christopher C.

    2015-10-01

    The production of quasi-definitive data at Ebre observatory has enabled us to detect a new geomagnetic jerk in early 2014. This has been confirmed by analyzing data at several observatories in the European-African and Western Pacific-Australian sectors in the classical fashion of looking for the characteristic V shape of the geomagnetic secular variation trend. A global model produced with the latest available satellite and observatory data supports these findings, giving a global perspective on both the jerk and a related secular acceleration pulse at the core-mantle boundary. We conclude that the jerk was most visible in the Atlantic and European sectors.

  3. Secular Variations of the Geomagnetic Field in Europe

    NASA Astrophysics Data System (ADS)

    Sas-Uhrynowski, A.; Welker, E.

    2009-09-01

    The international project MagNetE (Magnetic Net For Europe) was undertaken in 2003. The project has been accepted by the International Association of Geomagnetism and Aeronomy of the IUGG. The common research on the geomagnetic field space and time distribution in Europe, as well as collecting data and its analysis, constitutes the grounds for theoretical works on geomagnetic field models and their parameters. It is also the basis for studying the genesis of the geomagnetic field secular variations and its mechanism. The results of the project enable to increase the accuracy of models on the global, regional, and also on local scale. It has a vital meaning for the regions where the geomagnetic data are not available or, where the existing data, because of their low accuracy, cannot be used. Information about the secular variations of the geomagnetic field makes it possible to update the magnetic data, which is needed in navigation, topography, telecommunication, geology and geophysics and other domains. The enclosed maps of isopors presented have been compiled using the results of measuring campaigns in the years 2004-2006 together with the archive data. They show the secular variations of the magnetic declination D, the length H of the horizontal intensity vector and the lenght F of the total intensity vector of the geomagnetic field, in the intervals 1995-2000 and 2000-2005. The maps of isopors for Europe have been worked out using data from not only the magnetic observatories, but also from some hundred magnetic secular variation stations (repeated stations), located in 23 European countries. The secular variation differences between data obtained from terrestrial surveys and data from the IGRF model (International Geomagnetic Reference Field) have been presented in the form of maps and histograms. In several regions of Europe the unexpectedly large secular variation anomalies are visible. Anomalies of so high frequency and large amplitude cannot exist. They are probably caused by data errors, which may have different sources. Their existence cannot be explained by now. Therefore the MagNetE project should be continued.

  4. H-alpha response to geomagnetic disturbed activity at Arecibo.

    NASA Astrophysics Data System (ADS)

    Santos, Pedrina; Kerr, R.; Noto, J.; Brum, Christiano; Gonzalez, Sixto

    Configured with a spectral resolution of 0.0086 nm at 6563A, the low resolution Fabry-Perot Interferometer (FPI) installed at Arecibo Observatory sampled the geocoronal Balmer-alpha emission for sixty nights during new moon periods from September 2006 to September 2007. In this work two of these periods are analyzed according to the variability with the geomagnetic activity. With this purpose, the effect of the shadow height, local time and solar flux depen-dencies were found and isolated and only the possible variations due the geomagnetic activity were evaluated. The residuos of the relative H-alpha intensity and temperature are analyzed.

  5. IMF sector behavior estimated from geomagnetic data at South Pole

    SciTech Connect

    Matsushita, S.; Xu, W.h.

    1981-05-01

    IMF sector behavior which has previously been estimated from the geomagnetic data at Godhavn is confirmed by study of the data at South Pole for 1959--1970 with the same estimation technique, taking the difference between northern and southern hemispheres into consideration. A method to improve (about 18%) the agreement between assigned and actual sector structures by study of the data at the two stations is suggested. Geomagnetic disturbance effects on sector estimation are discussed, and reversed sector effects in winter are given special emphasis.

  6. GEOMAGNETIC REVERSALS DRIVEN BY ABRUPT SEA LEVEL CHANGES

    SciTech Connect

    Muller, R.A.; Morris, D.E.

    1986-10-01

    Changes in the moment of inertia of the earth, brought about by the redistribution of ocean water from the tropics to ice at high latitudes, couple energy from the spin of the earth into convection in the liquid core. This mechanism may help provide the driving energy for the earth's dynamo. Sufficiently rapid ocean level changes can disrupt the dynamo, resulting (in half of the cases) in a geomagnetic field reversal. The model can account for the previously mysterious correlation reported between geomagnetic reversals and mass extinctions.

  7. Very large geomagnetic disturbance during sunspot cycle 21: A prediction

    NASA Technical Reports Server (NTRS)

    Sargent, H. H., III

    1979-01-01

    Evidence is presented which suggests that very large geomagnetic disturbances (350 gammas or greater at an invariant magnetic latitude of 50 degrees) occur once or twice per sunspot cycle, on the average. There is also some tendency for these disturbances to group in large odd numbered sunspot cycles similar to the current cycle, cycle 21. No such disturbance was noted during the past cycle although a series of major solar flares was observed in August 1972. At least one very large geomagnetic disturbance is expected during the current cycle; a prediction with perhaps serious consequences for electric power companies.

  8. Poloidal and toroidal fields in geomagnetic field modeling

    NASA Astrophysics Data System (ADS)

    Backus, G.

    1986-02-01

    The application of surface operator theory to poloidal and toroidal fields in geomagnetic field modeling is described. Surface operators are obtained for the dimensionless surface gradient; the dimensionless surface curl; the dimensionless surface Laplacian, as well as for the Funk-Hecke operators, integral operators, and axisymmetric kernels. Methods are given for interpreting satellite measurements of the geomagnetic field B, assuming B is can vary significantly and rapidly with time, and there are electric fields in the sample. Approximation schemes for ionospheric currents are also described.

  9. Geomagnetic storms, the Dst ring-current myth and lognormal distributions

    USGS Publications Warehouse

    Campbell, W.H.

    1996-01-01

    The definition of geomagnetic storms dates back to the turn of the century when researchers recognized the unique shape of the H-component field change upon averaging storms recorded at low latitude observatories. A generally accepted modeling of the storm field sources as a magnetospheric ring current was settled about 30 years ago at the start of space exploration and the discovery of the Van Allen belt of particles encircling the Earth. The Dst global 'ring-current' index of geomagnetic disturbances, formulated in that period, is still taken to be the definitive representation for geomagnetic storms. Dst indices, or data from many world observatories processed in a fashion paralleling the index, are used widely by researchers relying on the assumption of such a magnetospheric current-ring depiction. Recent in situ measurements by satellites passing through the ring-current region and computations with disturbed magnetosphere models show that the Dst storm is not solely a main-phase to decay-phase, growth to disintegration, of a massive current encircling the Earth. Although a ring current certainly exists during a storm, there are many other field contributions at the middle-and low-latitude observatories that are summed to show the 'storm' characteristic behavior in Dst at these observatories. One characteristic of the storm field form at middle and low latitudes is that Dst exhibits a lognormal distribution shape when plotted as the hourly value amplitude in each time range. Such distributions, common in nature, arise when there are many contributors to a measurement or when the measurement is a result of a connected series of statistical processes. The amplitude-time displays of Dst are thought to occur because the many time-series processes that are added to form Dst all have their own characteristic distribution in time. By transforming the Dst time display into the equivalent normal distribution, it is shown that a storm recovery can be predicted with remarkable accuracy from measurements made during the Dst growth phase. In the lognormal formulation, the mean, standard deviation and field count within standard deviation limits become definitive Dst storm parameters.

  10. Systemic AA amyloidosis: epidemiology, diagnosis, and management

    PubMed Central

    Real de Asúa, Diego; Costa, Ramón; Galván, Jose María; Filigheddu, María Teresa; Trujillo, Davinia; Cadiñanos, Julen

    2014-01-01

    The term “amyloidosis” encompasses the heterogeneous group of diseases caused by the extracellular deposition of autologous fibrillar proteins. The global incidence of amyloidosis is estimated at five to nine cases per million patient-years. While amyloid light-chain (AL) amyloidosis is more frequent in developed countries, amyloid A (AA) amyloidosis is more common in some European regions and in developing countries. The spectrum of AA amyloidosis has changed in recent decades owing to: an increase in the median age at diagnosis; a percent increase in the frequency of primary AL amyloidosis with respect to the AA type; and a substantial change in the epidemiology of the underlying diseases. Diagnosis of amyloidosis is based on clinical organ involvement and histological evidence of amyloid deposits. Among the many tinctorial characteristics of amyloid deposits, avidity for Congo red and metachromatic birefringence under unidirectional polarized light remain the gold standard. Once the initial diagnosis has been made, the amyloid subtype must be identified and systemic organ involvement evaluated. In this sense, the 123I-labeled serum amyloid P component scintigraphy is a safe and noninvasive technique that has revolutionized the diagnosis and monitoring of treatment in systemic amyloidosis. It can successfully identify anatomical patterns of amyloid deposition throughout the body and enables not only an initial estimation of prognosis, but also the monitoring of the course of the disease and the response to treatment. Given the etiologic diversity of AA amyloidosis, common therapeutic strategies are scarce. All treatment options should be based upon a greater control of the underlying disease, adequate organ support, and treatment of symptoms. Nevertheless, novel therapeutic strategies targeting the formation of amyloid fibrils and amyloid deposition may generate new expectations for patients with AA amyloidosis. PMID:25378951

  11. Systemic AA amyloidosis: epidemiology, diagnosis, and management.

    PubMed

    Real de Asa, Diego; Costa, Ramn; Galvn, Jose Mara; Filigheddu, Mara Teresa; Trujillo, Davinia; Cadianos, Julen

    2014-01-01

    The term "amyloidosis" encompasses the heterogeneous group of diseases caused by the extracellular deposition of autologous fibrillar proteins. The global incidence of amyloidosis is estimated at five to nine cases per million patient-years. While amyloid light-chain (AL) amyloidosis is more frequent in developed countries, amyloid A (AA) amyloidosis is more common in some European regions and in developing countries. The spectrum of AA amyloidosis has changed in recent decades owing to: an increase in the median age at diagnosis; a percent increase in the frequency of primary AL amyloidosis with respect to the AA type; and a substantial change in the epidemiology of the underlying diseases. Diagnosis of amyloidosis is based on clinical organ involvement and histological evidence of amyloid deposits. Among the many tinctorial characteristics of amyloid deposits, avidity for Congo red and metachromatic birefringence under unidirectional polarized light remain the gold standard. Once the initial diagnosis has been made, the amyloid subtype must be identified and systemic organ involvement evaluated. In this sense, the (123)I-labeled serum amyloid P component scintigraphy is a safe and noninvasive technique that has revolutionized the diagnosis and monitoring of treatment in systemic amyloidosis. It can successfully identify anatomical patterns of amyloid deposition throughout the body and enables not only an initial estimation of prognosis, but also the monitoring of the course of the disease and the response to treatment. Given the etiologic diversity of AA amyloidosis, common therapeutic strategies are scarce. All treatment options should be based upon a greater control of the underlying disease, adequate organ support, and treatment of symptoms. Nevertheless, novel therapeutic strategies targeting the formation of amyloid fibrils and amyloid deposition may generate new expectations for patients with AA amyloidosis. PMID:25378951

  12. A method of predictions geomagnetic activity based on a coronal model of relations between solar and geomagnetic activities

    NASA Technical Reports Server (NTRS)

    Halenka, J.

    1979-01-01

    A method developed to predict both disturbed and quiet geomagnetic periods is described. The method uses solar situations along the CM with the key role of filaments, giving indirect evidence of types of directly unobservable coronal structures above them. The time lag, not to be interpreted in terms of propagation speed, between the CM activity and the commencement of the geomagnetic response is about one to two days. Solar phenomena serve as indicators within approximately 10 deg of the CM and up to the zone of high latitude filaments.

  13. Diurnal variations of cosmic ray geomagnetic cut-off threshold rigidities

    NASA Technical Reports Server (NTRS)

    Dvornikov, V. M.; Sdobnov, V. E.; Sergeev, A. V.; Danilova, O. A.; Tyasto, M. I.

    1985-01-01

    The spectrographic global survey method was used to investigate the rigidity variations Rc of geomagnetic cut-off as a function of local time and the level of geomagnetic disturbance for a number of stations of the world wide network. It is shown that geomagnetic cut-off threshold rigidities undergo diurnal variations. The diurnal wave amplitude decreases with increasing threshold rigidity Rc, and the wave maximum occurs at 2 to 4 hr LT. The amplitude of diurnal variations increases with increasing geomagnetic activity. The results agree with those from trajectory calculations made for an asymmetric model of the magnetosphere during different geomagnetic disturbance conditions.

  14. 7 CFR 51.596 - U.S. Grade AA.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Grades 51.596 U.S. Grade AA. U.S. Grade AA shall consist of stalks of celery of similar varietal characteristics, which are...

  15. 7 CFR 51.596 - U.S. Grade AA.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Grades 51.596 U.S. Grade AA. U.S. Grade AA shall consist of stalks of celery of similar varietal characteristics, which are...

  16. Processing and Optimization of Dissimilar Friction Stir Welding of AA 2219 and AA 7039 Alloys

    NASA Astrophysics Data System (ADS)

    Venkateswarlu, D.; Nageswara rao, P.; Mahapatra, M. M.; Harsha, S. P.; Mandal, N. R.

    2015-12-01

    The present paper discusses the optimization of dissimilar friction stir welding of AA 2219 and AA 7039 alloys with respect to tool design issues including microstructural study of weld. The optimized ultimate tensile strength was ~280 MPa, and % elongation was ~11.5. It was observed that the extent of tool shoulder flat surface and tool rotational speed influenced the weld quality significantly. A mathematical model was also developed using response surface regression analysis to predict the effects of tool geometry and process variables on dissimilar AA 2219 and AA 7039 alloys welds. The microstructure evolution and mechanical properties were investigated by employing electron backscatter diffraction technique, Vickers microhardness, and tensile testing, respectively. The microstructural observations indicated that the grain size obtained at advancing side (AA 2219 alloy side) was much finer compared to the retreating side (AA 7039 alloy side). Hardness distribution in the stir zone was inhomogeneous, which might be due to inadequate mixing of weld zone material. The hardness values observed at the weld zone were lower than that in the base materials.

  17. Processing and Optimization of Dissimilar Friction Stir Welding of AA 2219 and AA 7039 Alloys

    NASA Astrophysics Data System (ADS)

    Venkateswarlu, D.; Nageswara rao, P.; Mahapatra, M. M.; Harsha, S. P.; Mandal, N. R.

    2015-11-01

    The present paper discusses the optimization of dissimilar friction stir welding of AA 2219 and AA 7039 alloys with respect to tool design issues including microstructural study of weld. The optimized ultimate tensile strength was ~280 MPa, and % elongation was ~11.5. It was observed that the extent of tool shoulder flat surface and tool rotational speed influenced the weld quality significantly. A mathematical model was also developed using response surface regression analysis to predict the effects of tool geometry and process variables on dissimilar AA 2219 and AA 7039 alloys welds. The microstructure evolution and mechanical properties were investigated by employing electron backscatter diffraction technique, Vickers microhardness, and tensile testing, respectively. The microstructural observations indicated that the grain size obtained at advancing side (AA 2219 alloy side) was much finer compared to the retreating side (AA 7039 alloy side). Hardness distribution in the stir zone was inhomogeneous, which might be due to inadequate mixing of weld zone material. The hardness values observed at the weld zone were lower than that in the base materials.

  18. Surface electric fields for North America during historical geomagnetic storms

    USGS Publications Warehouse

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  19. Possible helio-geomagnetic activity influence on cardiological cases

    NASA Astrophysics Data System (ADS)

    Katsavrias, Christos

    Eruptive solar events as flares and coronal mass ejections (CMEs) occur during solar activ-ity periods. Energetic particles, fast solar wind plasma and electromagnetic radiation pass through interplanetary space, arrive on Earth's ionosphere-magnetosphere and produce various disturbances. It is well known the negative influence of geomagnetic substorms on the human technological applications on geospace. During the last 25 years, many studies concerning the possible influence on the human health are published. Increase of the Acute Coronary Syn-dromes and disorders of the Cardiac Rhythm, increase of accidents as well as neurological and psychological disorders (e.g. increase of suicides) during or near to the geomagnetic storms time interval are reported. In this study, we research the problem in Greece, focusing on patients with Acute Myocardial Infraction, hospitalized in the 2nd Cardiological Department of the General Hospital of Nikaea (Piraeus City), for the time interval 1997-2007 (23rd solar cycle) and also to the arrival of emergency cardiological cases to Emergency Department of two greek hospitals, the General Hospital of Lamia City and the General Hospital of Veria City during the selected months, with or without helio-geomagnetic activity, of the 23rd solar cycle. Increase of cases is recorded during the periods with increase helio-geomagnetic activity. The necessity of continuing the research for a longer period and with a bigger sample is high; so as to exact more secure conclusions.

  20. (abstract) A Geomagnetic Contribution to Climate Change in this Century

    NASA Technical Reports Server (NTRS)

    Feynman, J.; Ruzmaikin, A.; Lawrence, J.

    1996-01-01

    There is a myth that all solar effects can be parameterized by the sun spot number. This is not true. For example, the level of geomagnetic activity during this century was not proportional to the sunspot number. Instead there is a large systematic increase in geomagnetic activity, not reflected in the sunspot number. This increase occurred gradually over at least 60 years. The 11 year solar cycle variation was superimposed on this systematic increase. Here we show that this systematic increase in activity is well correlated to the simultaneous increase in terrestrial temperature that occurred during the first half of this century. We discuss these findings in terms of mechanisms by which geomagnetics can be coupled to climate. These mechanisms include possible changes in weather patterns and cloud cover due to increased cosmic ray fluxes, or to increased fluxes of high energy electrons. We suggest that this systematic increase in geomagnetic activity contributed (along with anthropogenic effects and possible changes in solar irradiance) to the changes in climate recorded during this period.

  1. New insights on geomagnetic storms from observations and modeling

    SciTech Connect

    Jordanova, Vania K

    2009-01-01

    Understanding the response at Earth of the Sun's varying energy output and forecasting geomagnetic activity is of central interest to space science, since intense geomagnetic storms may cause severe damages on technological systems and affect communications. Episodes of southward (Bzgeomagnetic conditions are associated either with coronal mass ejections (CMEs) and possess long and continuous negative IMF Bz excursions, or with high speed solar wind streams (HSS) whose geoeffectiveness is due to IMF Bz profiles fluctuating about zero with various amplitudes and duration. We show examples of ring current simulations during two geomagnetic storms representative of each interplanetary condition with our kinetic ring current atmosphere interactions model (RAM), and investigate the mechanisms responsible for trapping particles and for causing their loss. We find that periods of increased magnetospheric convection coinciding with enhancements of plasma sheet density are needed for strong ring current buildup. During the HSS-driven storm the convection potential is highly variable and causes small sporadic injections into the ring current. The long period of enhanced convection during the CME-driven storm causes a continuous ring current injection penetrating to lower L shells and stronger ring current buildup.

  2. Geomagnetic storms and their impact on power systems

    SciTech Connect

    Kappenman, J.G.

    1996-05-01

    This article examines the lessons learned for solar cycle 22 and the application of these to solar cycle 23. The topics of the article include a review of the characteristics of the current solar cycle, the power system reliability threat, geomagnetically induced currents (GIC) as the cause of transformer failures, and magnetic storm forecast improvements.

  3. 78 FR 30747 - Reliability Standards for Geomagnetic Disturbances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-23

    ... for Geomagnetic Disturbances, Notice of Proposed Rulemaking, 77 FR 64,935 (Oct. 24, 2012), 141 FERC...-cycle saturation'' of high-voltage Bulk-Power System transformers, which can lead to increased... electromagnetic pulses on the Bulk-Power System in January 2010.\\10\\ NERC issued the HILF Report on...

  4. Solar Activity, Different Geomagnetic Activity Levels and Acute Myocardial Infarction

    NASA Astrophysics Data System (ADS)

    Dimitrova, Svetla; Jordanova, Malina; Stoilova, Irina; Taseva, Tatiana; Maslarov, Dimitar

    Results on revealing a possible relationship between solar activity (SA) and geomagnetic activity (GMA) and acute myocardial infarction (AMI) morbidity are presented. Studies were based on medical data covering the period from 1.12.1995 to 31.12.2004 and concerned daily distribution of patients with AMI diagnose (in total 1192 cases) from Sofia region on the day of admission at the hospital. Analysis of variance (ANOVA) was applied to check the significance of GMA intensity effect and the type of geomagnetic storms, those caused by Magnetic Clouds (MC) and by High Speed Solar Wind Streams (HSSWS), on AMI morbidity. Relevant correlation coefficients were calculated. Results revealed statistically significant positive correlation between considered GMA indices and AMI. ANOVA revealed that AMI number was signifi- cantly increased from the day before (-1st) till the day after (+1st) geomagnetic storms with different intensities. Geomagnetic storms caused by MC were related to significant increase of AMI number in comparison with the storms caused by HSSWS. There was a trend for such different effects even on -1st and +1st day.

  5. Surface electric fields for North America during historical geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Wei, Lisa H.; Homeier, Nicole; Gannon, Jennifer L.

    2013-08-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic stormsthe 1989 "Quebec" storm and the 2003 "Halloween" storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  6. An empirical model of the quiet daily geomagnetic field variation

    USGS Publications Warehouse

    Yamazaki, Y.; Yumoto, K.; Cardinal, M.G.; Fraser, B.J.; Hattori, P.; Kakinami, Y.; Liu, J.Y.; Lynn, K.J.W.; Marshall, R.; McNamara, D.; Nagatsuma, T.; Nikiforov, V.M.; Otadoy, R.E.; Ruhimat, M.; Shevtsov, B.M.; Shiokawa, K.; Abe, S.; Uozumi, T.; Yoshikawa, A.

    2011-01-01

    An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp ??? 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity. Copyright 2011 by the American Geophysical Union.

  7. The Use of Dispersion Relations For The Geomagnetic Transfer Functions

    NASA Astrophysics Data System (ADS)

    Marcuello, A.; Queralt, P.; Ledo, J. J.

    The magnetotelluric responses are complex magnitudes, where real and imaginary parts contain the same information on the geoelectrical structure. It seems possible, from very general hypotheses on the geoelectrical models (causality, stability and passivity), to apply the Kramers-Krnig dispersion relations to the magnetotelluric responses (impedance, geomagnetic transfer functions,...). In particular, the applica- bility of these relations to the impedance is a current point of discussion, but there are not many examples of their application to the geomagnetic transfer functions (tipper). The aim of this paper is to study how the relations of dispersion are applied to the real and imaginary part of the geomagnetic transfer functions, and to check its validity. For this reason, we have considered data (or responses) from two- and three-dimensional structures, and for these data, we have taken two situations: 1.- Responses that have been synthetically generated from numerical modelling, that allows us to control the quality of the data. 2.- Responses obtained from fieldwork, that are affected by exper- imental error. Additionally, we have also explored the use of these relations to extrap- olate the geomagnetic transfer functions outside the interval of measured frequencies, in order to obtain constrains on the values of these extrapolated data. The results have shown that the dispersion relations are accomplished for the geomag- netic transfer functions, and they can offer information about how these responses are behaved outside (but near) the range of measured frequencies.

  8. Geomagnetic cutoffs: a review for space dosimetry applications.

    PubMed

    Smart, D F; Shea, M A

    1994-10-01

    The earth's magnetic field acts as a shield against charged particle radiation from interplanetary space, technically described as the geomagnetic cutoff. The cutoff rigidity problem (except for the dipole special case) has "no solution in closed form". The dipole case yields the Stormer equation which has been repeatedly applied to the earth in hopes of providing useful approximations of cutoff rigidities. Unfortunately the earth's magnetic field has significant deviations from dipole geometry, and the Stormer cutoffs are not adequate for most applications. By application of massive digital computer power it is possible to determine realistic geomagnetic cutoffs derived from high order simulation of the geomagnetic field. Using this technique, "world-grids" of directional cutoffs for the earth's surface and for a limited number of satellite altitudes have been derived. However, this approach is so expensive and time consuming it is impractical for most spacecraft orbits, and approximations must be used. The world grids of cutoff rigidities are extensively used as lookup tables, normalization points and interpolation aids to estimate the effective geomagnetic cutoff rigidity of a specific location in space. We review the various options for estimating the cutoff rigidity for earth-orbiting satellites. PMID:11540027

  9. Predicting the Size of Sunspot Cycle 24 on the Basis of Single- and Bi-Variate Geomagnetic Precursor Methods

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2009-01-01

    Examined are single- and bi-variate geomagnetic precursors for predicting the maximum amplitude (RM) of a sunspot cycle several years in advance. The best single-variate fit is one based on the average of the ap index 36 mo prior to cycle minimum occurrence (E(Rm)), having a coefficient of correlation (r) equal to 0.97 and a standard error of estimate (se) equal to 9.3. Presuming cycle 24 not to be a statistical outlier and its minimum in March 2008, the fit suggests cycle 24 s RM to be about 69 +/- 20 (the 90% prediction interval). The weighted mean prediction of 11 statistically important single-variate fits is 116 +/- 34. The best bi-variate fit is one based on the maximum and minimum values of the 12-mma of the ap index; i.e., APM# and APm*, where # means the value post-E(RM) for the preceding cycle and * means the value in the vicinity of cycle minimum, having r = 0.98 and se = 8.2. It predicts cycle 24 s RM to be about 92 +/- 27. The weighted mean prediction of 22 statistically important bi-variate fits is 112 32. Thus, cycle 24's RM is expected to lie somewhere within the range of about 82 to 144. Also examined are the late-cycle 23 behaviors of geomagnetic indices and solar wind velocity in comparison to the mean behaviors of cycles 2023 and the geomagnetic indices of cycle 14 (RM = 64.2), the weakest sunspot cycle of the modern era.

  10. Detection of Geomagnetic variation related to some micro-earthquake events in the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Kim, K.; Oh, S.; Noh, M.; Ji, Y.

    2011-12-01

    This study depicts some values of newly proposed approach to detect the earthquake related geomagnetic variation with real data. Wavelet-based semblance, restoration and prediction by Principal Component analysis (PCA), and eigen-value analysis were applied to detection of geomagnetic variation which is believed to be related with some micro-earthquakes in the seismically inactive Korean Peninsula. For totally ten earthquake events which had occurred between 2009 and 2011, significant correlation of geomagnetic variation was observed before each event, and at least concurrently. For the analysis, restored geomagnetic data by PCA method were compared with the observed original geomagnetic time series, using wavelet-based semblance technique, and eigen-value analysis for three components of geomagnetic data was applied. And for the clarity, geomagnetic observation from two or three different observatories was used for analysis of each event.

  11. On the Possibilities of Predicting Geomagnetic Secular Variation with Geodynamo Modeling

    NASA Technical Reports Server (NTRS)

    Kuang, Wei-Jia; Tangborn, Andrew; Sabaka, Terrance

    2004-01-01

    We use our MoSST core dynamics model and geomagnetic field at the core-mantle boundary (CMB) continued downward from surface observations to investigate possibilities of geomagnetic data assimilation, so that model results and current geomagnetic observations can be used to predict geomagnetic secular variation in future. As the first attempt, we apply data insertion technique to examine evolution of the model solution that is modified by geomagnetic input. Our study demonstrate that, with a single data insertion, large-scale poloidal magnetic field obtained from subsequent numerical simulation evolves similarly to the observed geomagnetic variation, regardless of the initial choice of the model solution (so long it is a well developed numerical solution). The model solution diverges on the time scales on the order of 60 years, similar to the time scales of the torsional oscillations in the Earth's core. Our numerical test shows that geomagnetic data assimilation is promising with our MoSST model.

  12. 7 CFR 51.596 - U.S. Grade AA.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false U.S. Grade AA. 51.596 Section 51.596 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Consumer Standards for Celery Stalks Grades § 51.596 U.S. Grade AA. U.S. Grade AA shall consist of...

  13. Early Cretaceous geomagnetic behaviour compared to a computer model

    NASA Astrophysics Data System (ADS)

    Iorio, M.; Tarling, D. H.; D'Argenio, B.

    2001-12-01

    Twelve patterns of geomagnetic dipole behaviour, recurring five times, are recorded in a 88 m bore-core penetrating some 3.2 Ma of shallow water carbonates around 127 Ma (Early Cretaceous of Southern Italy). Each pattern sequence represents a complete reversal cycle that lasts for c. 660 ka, formed of c. 300 ka of predominantly normal polarity and c. 330 ka of mainly reversed polarity. Virtual Geomagnetic Pole (VGP) excursions, mostly lasting 5-25 ka, are initially of lower amplitude; these become increasingly common and of larger amplitude until a reversal is completed. The succession of excursions, within the reversed sequences, appears to occur as harmonics of about 20, 44 and 64 ka. These are comparable to the Earth's orbital frequencies (precession and obliquity). Long-term orbital eccentricity cycles have been identified in the intensity of oceanic magnetic anomalies of the same age (Iorio, M., Tarling, D.H., D'Argenio, B. 1998b, Periodicity of magnetic intensities in magnetic anomaly profiles: the Cretaceous of the Central Pacific. Geophysical Journal International 133, 233-244). Geomagnetic behaviour predicted from 3-D computer simulations by Glatzmaier et al. (Glatzmaier, G.A., Coe, R.S., Hongre, L., Roberts, P.H., 1999. The role of the Earth's mantle in controlling the frequency of geomagnetic reversals. Nature 401, 885-890), based on the geophysical properties of the present-day core-mantle boundary, has very close similarities to that observed in the bore-core remanence. In particular, oscillations in the location and intensity of the computed geomagnetic dipole occur on almost identical time-scales to those previously determined for the bore-core VGP and intensity.

  14. Probabilistic forecasting analysis of geomagnetic indices for southward IMF events

    NASA Astrophysics Data System (ADS)

    Zhang, X.-Y.; Moldwin, M. B.

    2015-03-01

    Geomagnetic disturbances that drive space weather impacts such as ground-induced currents and radiation belt enhancements are usually driven by strong southward interplanetary magnetic field (IMF) intervals. However, current heliospheric models either do not predict or provide low-accuracy forecasts of IMF Bz. Here we examine the probability distribution function of geomagnetic activity indices for southward IMF intervals. We analyze the in situ plasma and magnetic field measurements long-duration large-amplitude southward IMF intervals (called Bs events). The statistical profiles of other solar wind and IMF parameters show significant differences during the periods 1 day before the Bs events for different solar wind transients (such as interplanetary coronal mass ejections and stream interaction regions). As is well known, we find that the solar wind speed is positively correlated with geomagnetic indices and that strong southward IMF is the key in storm triggering but not necessarily for substorms. We find that the solar wind density weakly affects geomagnetic field activity, but the response depends on the type of solar wind transient that includes the strong Bs events. We also find that magnetospheric ultralow-frequency waves are induced by both strong southward IMF and solar wind dynamic pressure disturbances. We suggest that strong Bs events could be predicted from the preceding characteristics of solar wind and IMF changes and that probabilistic forecasting of geomagnetic activity occurrence is potentially useful in space weather forecasting. We present preliminary analysis to demonstrate the out-of-sample ability to predict IMF Bs events with in situ solar wind data.

  15. Geomagnetic Storms and Acute Myocardial Infarctions Morbidity in Middle Latitudes

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.; Babayev, E. S.; Mustafa, F. R.; Stoilova, I.; Taseva, T.; Georgieva, K.

    2009-12-01

    Results of collaborative studies on revealing a possible relationship between solar activity (SA) and geomagnetic activity (GMA) and pre-hospital acute myocardial infarction (AMI) morbidity are presented. Studies were based on medical data from Bulgaria and Azerbaijan. Bulgarian data, covering the period from 01.12.1995 to 31.12.2004, concerned daily distribution of number of patients with AMI diagnose (in total 1192 cases) from Sofia Region on the day of admission at the hospital. Azerbaijani data contained 4479 pre-hospital AMI incidence cases for the period 01.01.2003-31.12.2005 and were collected from 21 emergency and first medical aid stations in Grand Baku Area (including Absheron Economical Region with several millions of inhabitants). Data were "cleaned" as much as possible from social and other factors and were subjected to medical and mathematical/statistical analysis. Medical analysis showed reliability of the used data. Method of ANalysis Of VAriance (ANOVA) was applied to check the significance of GMA intensity effect and the type of geomagnetic storms - those caused by magnetic clouds (MC) and by high speed solar wind streams (HSSWS) - on AMI incidences. Relevant correlation coefficients were calculated. Results were outlined for both considered data. Results obtained for the Sofia data showed statistically significant positive correlation between considered GMA indices and AMI occurrence. ANOVA revealed that AMI incidence number was significantly increased from the day before till the day after geomagnetic storms with different intensities. Geomagnetic storms caused by MC were related to significant increase of AMI number in comparison with the storms caused by HSSWS. There was a trend for such different effects even on -1st and +1st day for the period 1995-2004. Results obtained for the Baku data revealed trends similar to those obtained for Sofia data. AMI morbidity increment was observed on the days with higher GMA intensity and after these days as well as on the days of geomagnetic storms caused by MC and after these days.

  16. Physical Meaning of the Equinoctial Effect for Seasonal Variation of Geomagnetic Activity

    NASA Astrophysics Data System (ADS)

    Yoshida, A.

    2008-12-01

    The general tendency for magnetic disturbances to be more stormy at equinoxes than at solstices has been recognised for more than 150 years. To explain the seasonal variation three principal hypotheses have been proposed; the axial hypothesis (Cortie, 1912), the equinoctial hypothesis (Bartels, 1932; McIntosh, 1959), and the Russell and McPherron (RM) hypothesis (Russell and McPherron, 1973). The RM hypothesis, which is based on the recognition that the magnetic field in the solar equatorial plane tends to have the largest southward component in geocentric solar magnetospheric (GSM) coordinates in early April and October, has been largely accepted for many years. However, recent studies have confirmed that the RM effect accounts for only a subordinate proportion of the seasonal variation of geomagnetic activity, and that the larger part of the phenomenon is attributable to the equinoctial effect in which the angle between the solar wind flow and the dipole axis of the Earth plays an essential role (Cliver, Kamide and Ling, 2000; Cliver, Kamide, Ling and Yokoyama, 2001; O'Brien and McPherron, 2002). In this paper physical meaning of the equinoctial effect is investigated based on the data of three-hourly am index and solar wind parameters acquired by the ACE satellite. The am indices are well correlated with BsVxVx, where Bs is the southward component of the interplanetary magnetic field (IMF) and Vx is the solar wind velocity in the sun-earth direction. It is found, however, that the am - BsVxVx relation depends on the range of VxVx: The am in higher ranges of VxVx tends to be larger than am in lower ranges of VxVx for both equinoctial and solstitial epochs for the same value of BsVxVx. Using the data sets of the same VxVx range, it is shown that distribution of points in the am - BsVxVx diagram at the solstitial epochs overlaps with that at the equinoctial epochs and the average am values in each BsVxVx bin in solstitial epochs are almost equal to those in equinoctial epochs, if VxVx for each point at solstices are reduced to VxVx sin (c) where c is the geomagnetic colatitude of the sub-solar point. This finding indicates that the emergence of the geomagnetic disturbance is regulated by the component of the solar wind velocity perpendicular to the dipole axis of the geomagnetic field. The magnitude of the perpendicular velocity component varies seasonally even if the solar wind velocity remains constant. This appears to be the long-missed key factor causing the equinoctial effect. It is interesting to note that both the RM and equinoctial effects are related to seasonal changes in the efficiency of solar wind - magnetosphere coupling caused by changes in the geometric configuration between the sun and the geomagnetic dipole field, one in relation to Bs of the IMF, and the other in relation to the component of solar wind velocity perpendicular to the dipole axis.

  17. Observed geomagnetic induction effect on Dst-related magnetic observations under different disturbance intensities of the magnetospheric ring current

    NASA Astrophysics Data System (ADS)

    Xu, Dan; Chen, Huaran; Gao, Mengtan

    2015-12-01

    Based on the spherical harmonic expansion of geomagnetic disturbance observed on the mid-latitude surface of the Earth, external and internal field separation is conducted in which the external component is magnetic disturbance caused by the magnetospheric ring current and the internal component is that raised by the correspondingly induced currents within the Earth. The objectives are to evaluate the influences of the induced internal field on the surface magnetic observations and to reveal the response performance of internal geomagnetic induction under different strengths of magnetospheric ring current fluctuations for better understanding of the disturbance storm time ( Dst) index variations. The results show that the ratio of the internal component to surface observation does not remain constant in storm time. During the main phase of the storm, the ratio variation follows the pattern of logarithmic growth with storm evolution up to the top value at the Dst-minimum; then, the ratio slowly decreases in the long recovery phase. Multiple small logarithmic growths are superimposed on the traces of internal ratios, corresponding to temporary ring current intensification during the storm main phase and amplifying the effect of this intensification on surface magnetic observations. With the intensification of magnetospheric storms from the level of (-200 nT, - 100 nT) to (-300 nT, - 200 nT) and (-500 nT, - 300 nT) classified with the Dst-minimum, the top value of the ratio averaged for each storm group in the superposed epoch analysis method increases from the value of 0.295 ± 0.014 to 0.300 ± 0.016 and 0.308 ± 0.015, respectively. It is demonstrated that the geomagnetic induction exceeds the linear relation with the intensification of the external field, which is physically reasonable and coincident with the Faraday's law of induction. Due to the effects of high induction of the oceans and lateral heterogeneity of electric conductivity distribution in the upper mantle of the Earth, the geomagnetic induction and its contribution to surface geomagnetic disturbance vary significantly among observatories. This factor should be considered in the research of magnetospheric current systems.

  18. 40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for CH4 and N2O

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Factors for CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment ENVIRONMENTAL... Manufacturing Pt. 98, Subpt. AA, Table AA -2 Table AA-2 to Subpart AA of Part 98Kraft Lime Kiln and Calciner... coke 0.0027 0 aNA aNA Other Fuels See Table C-2 0 See Table C-2 See Table C-2 a Emission factors...

  19. The Effectiveness of the AAS REU Program

    NASA Astrophysics Data System (ADS)

    Hemenway, M. K.; Boyce, P. B.; Milkey, R. W.

    1996-05-01

    In an attempt to address the particular needs of astronomy faculty and undergraduate students, in 1991 the Education Office of the American Astronomical Society approached the National Science Foundation with a unique proposal for funding through the Research Experiences for Undergraduates program. The goals of the AAS program were to "slow the hemorrhage of students out of science...", extend the REU program to non-NSF-funded scientists, to reach under-represented women and minority students particularly in small educational institutions, and to encourage research scientists there to mentor students. As this grant has now expired, the AAS has surveyed the 44 mentors and their students to assess the program's effect on the mentor and the mentor's career; the educational institution; and the student's education and career choices. More than half the mentors responded by the abstract deadline. The program clearly had an effect upon the individuals involved. The greatest effect (in 85% of the cases) was to develop more interest in the mentor's research project both among the students and among the mentor's faculty colleagues. The mentors rated the grant to be a medium or strong factor in their student's decision to pursue graduate study, which 90% of them did. All but one of the AAS-REU students attended an AAS meeting and 3/4 of those gave a paper on their project research. Over 90% of the mentors felt that the research experience strongly promoted a greater interest in science, a greater understanding of science and a desire to continue in science. According to the mentors, this was a very positive and beneficial program for the students as well as for themselves.

  20. A profile of Keith AA Fox, cardiologist and researcher.

    PubMed

    Fox, Keith A A; Telfer, Caroline

    2014-01-01

    Professor Keith AA Fox speaks to Caroline Telfer, Commissioning Editor. Professor Keith AA Fox is the British Heart Foundation and the Duke of Edinburgh Professor of Cardiology at the University of Edinburgh (UK). He is a founding fellow of the European Society of Cardiology and is currently Chair of the Programme of the European Society of Cardiology. In addition, he was President of the British Cardiovascular Society from 2009 to 2012. Professor Fox gave the State-of-the-Art lecture on acute coronary syndromes at the American Heart Association, as well as the 2009 Plenary lecture at the European Society of Cardiology-American College of Cardiology Symposium, the Lord Rayner lecture of the Royal College of Physicians (London, UK) and the Sir Stanley Davidson Lecture of the Royal College (Edinburgh, UK). He was awarded the Silver Medal of the European Society of Cardiology in 2010. Professor Fox's major research interest lies in the mechanisms and manifestations of acute coronary arterial disease; his work extends from underlying biological mechanisms to in vitro and in vivo studies and clinical trials. He is the author of more than 587 scientific papers (H-index Web of Science 73, Citations: 30,261 to March 2013). Professor Fox is chairman of the RITA program, co-chairman of ROCKET-AF and OASIS program, and chair of the GRACE program (the largest multinational study in acute coronary syndromes), and a lead investigator for studies on novel antithrombins, anticoagulants and antiplatelets. He is an International Associate Editor of the European Heart Journal and a member of the editorial boards of a number of journals. His current areas of research include the inhibition of coronary thrombosis and the role of platelets and inflammation in acute coronary syndromes. PMID:24344658

  1. Data Behind the Figures in AAS Journals

    NASA Astrophysics Data System (ADS)

    Biemesderfer, Chris

    2013-01-01

    Substantial amounts of digital data are produced in the scientific enterprise, and much of it is carefully analyzed and processed. Often resulting from a good deal of intellectual effort, many of these highly-processed products are published in the scholarly literature. Many of these data - or more precisely, representations of these data - are committed to the scholarly record in the forms of figures and tables that appear within articles: the AAS journals publish more than 30,000 figures and nearly 10,000 tables each year. For more than a decade, the AAS journals have accepted machine-readable tables that provide the data behind (some of) the tables, and recently the journals have started to encourage the submission of the data behind figures. (See the related poster by Greg Schwarz.) During this time, the journals have been refining techniques for acquiring and managing the digital data that underlie figures and tables. In 2012 the AAS was awarded a grant by the US NSF so that the journals can extend the methods for providing access to these data objects, through a deeper collaboration with the VO and with organizations like DataCite, and by spearheading discussions about the formats and metadata that will best facilitate long-term data management and access. An important component of these activities is educating scientists about the importance and benefits of making such data sets available.

  2. Processing Electronic Abstracts for AAS Meetings

    NASA Astrophysics Data System (ADS)

    Dalterio, H.

    1993-05-01

    The AAS has accepted abstracts for its last three meetings via electronic mail. On balance, this experiment has been well-received by the community (over 80% of the abstracts for this meeting were taken via email), even though the AAS only accepts electronic abstracts prepared with a specific template. Despite an enhanced number of submissions close to the deadline, abstract processing at the Executive Office is considerably more expedient as compared with an all-paper system. The error rate among electronic submissions is quite tractable. The use of a well-defined template arises from the need for consistent tags to identify elements of information. The AAS template uses a \\LaTeX\\ command syntax to mark up the abstract and the supporting data (payment method, session type, etc.) for several reasons. Even though \\LaTeX\\ is widely thought of as a typesetting system, its value in electronic submission is as a descriptive markup tool that permits all parties to identify an article's structure. It is important for authors to understand that formatting-oriented instructions interfere with this process.

  3. Introducing the AAS Astronomy Ambassadors Program

    NASA Astrophysics Data System (ADS)

    Gurton, S.; Fienberg, R. T.; Fraknoi, A.; Prather, E. E.

    2013-04-01

    Newly established by the American Astronomical Society (AAS), the Astronomy Ambassadors program is designed to support early-career AAS members with training in resources and techniques for effective outreach to students and/or the public. A pilot Astronomy Ambassadors workshop will be held at the January 2013 AAS meeting. Workshop participants will learn to communicate effectively with public and school audiences; find outreach opportunities and establish ongoing partnerships with local schools, science centers, museums, parks, and/or community centers; reach audiences with personal stories, hands-on activities, and jargon-free language; identify strategies and techniques to improve their presentation skills; gain access to a menu of outreach resources that work in a variety of settings; and become part of an active community of astronomers who do outreach. Applications are welcome from advanced undergraduates (those doing research and committed to continuing in astronomy), graduate students, and postdocs and new faculty in their first two years after receipt of the PhD. We especially encourage applications from members of groups that are presently underrepresented in science.

  4. Geomagnetic field behavior during the Iceland Basin and Laschamp geomagnetic excursions: A simple transitional field geometry?

    NASA Astrophysics Data System (ADS)

    Laj, Carlo; Kissel, Catherine; Roberts, Andrew P.

    2006-03-01

    We present four new records of the Iceland Basin Excursion (IBE) and five new records of the Laschamp Excursion (LE) obtained from rapidly deposited marine sediments in the North Atlantic Ocean, the Nordic Seas, the Gulf of Mexico, the South China Sea, and the southern Indian Ocean. Marked minima in relative paleointensity correspond with the paleomagnetic directional changes associated with all of the excursion records. The virtual geomagnetic pole (VGP) paths of the four IBE records are all similar. The VGPs move southward over Europe and Africa, reaching the southern hemisphere (three reach Antarctica), and then move to more eastern longitudes before returning northward over Australia and east Asia, describing a large counterclockwise loop. The same VGP pattern is observed in other published records. The VGP paths observed for the LE are similar to those of the IBE; however, they loop clockwise instead of counterclockwise. Despite the different sense of looping, the marked similarity among the paths for the two excursions suggests that a similar, relatively simple geometry dominated the transitional field during both the IBE and the LE. Similar dynamo mechanisms must therefore have been active in the Earth's core for both excursions. The duration of the excursions is estimated at <2,000 years, which supports the suggestion that a difference exists between the mechanisms for excursions and reversals. However, the coincidence of the longitudinal bands for VGPs associated with excursions compared to some reversal paths could also indicate an inherent link between the mechanisms for reversals and excursions.

  5. Ionospheric current source modeling and global geomagnetic induction using ground geomagnetic observatory data

    NASA Astrophysics Data System (ADS)

    Sun, J.; Kelbert, A.; Egbert, G. D.

    2015-10-01

    Long-period global-scale electromagnetic induction studies of deep Earth conductivity are based almost exclusively on magnetovariational methods and require accurate models of external source spatial structure. We describe approaches to inverting for both the external sources and three-dimensional (3-D) conductivity variations and apply these methods to long-period (T≥1.2 days) geomagnetic observatory data. Our scheme involves three steps: (1) Observatory data from 60 years (only partly overlapping and with many large gaps) are reduced and merged into dominant spatial modes using a scheme based on frequency domain principal components. (2) Resulting modes are inverted for corresponding external source spatial structure, using a simplified conductivity model with radial variations overlain by a two-dimensional thin sheet. The source inversion is regularized using a physically based source covariance, generated through superposition of correlated tilted zonal (quasi-dipole) current loops, representing ionospheric source complexity smoothed by Earth rotation. Free parameters in the source covariance model are tuned by a leave-one-out cross-validation scheme. (3) The estimated data modes are inverted for 3-D Earth conductivity, assuming the source excitation estimated in step 2. Together, these developments constitute key components in a practical scheme for simultaneous inversion of the catalogue of historical and modern observatory data for external source spatial structure and 3-D Earth conductivity.

  6. Modelling total electron content during geomagnetic storm conditions using empirical orthogonal functions and neural networks

    NASA Astrophysics Data System (ADS)

    Uwamahoro, Jean Claude; Habarulema, John Bosco

    2015-12-01

    It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, TEC modelling was performed over Sutherland (32.38°S, 20.81°E, 41.09°S geomagnetic), South Africa, during storm conditions, using a combination of empirical orthogonal function (EOF) and regression analyses techniques. The neural network (NN) technique was also applied to the same TEC data set, and its output was compared with TEC modeled using the EOF model. TEC was derived from GPS observations, and a geomagnetic storm was defined for Dst≤-50 nT. The hour of the day and the day number of the year, F10.7p and A indices, were chosen as inputs for the modeling techniques to take into account diurnal and seasonal variation of TEC, solar, and geomagnetic activities, respectively. Both EOF and NN models were developed using GPS TEC data for storm days counted from 1999 to 2013 and tested on different storms. For interpolation, the EOF and NN models were validated on storms that occurred during high and low solar activity periods (storms of 2000 and 2006), while for extrapolation the validation was done for the storms of 2014 and 2015, identified based on the provisional Dst index data. A comparison of the modeled TEC with the observed TEC showed that both EOF and NN models perform well for storms with nonsignificant ionospheric TEC response and storms that occurred during period of low solar activity. For storms with significant TEC response, TEC magnitude is well captured during the nighttime and early morning, but short-term features, TEC enhancement, and depression are not sufficiently captured by the models. Statistically, the NN model performs 12.79% better than the EOF model on average, over all storm periods considered. Furthermore, it has been shown that the EOF and NN models developed for a specific station can be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7° and 10.6°, respectively. This is an important result as it reduces the data dimensionality problem for computational purposes.

  7. Behavior of the ionosphere over Europe during two geomagnetic storms which caused tongues of ionization over North America.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Bouza, Marta; Herraiz, Miguel; Rodriguez-Caderot, Gracia; Radicella, Sandro M.

    2015-04-01

    This work presents the effect of two geomagnetic storms on the ionospheric total electron content (TEC) over Europe. Those geomagnetic storms occurred on July 14th, 2013 and February 19th, 2014 and originated a tongue of ionization over North America. Following the criteria of Gonzalez et al.(1994), the July storm can be classified as a moderate one because the Dst index reached a value of -72nT, whereas the February storm as an intense event considering that Dst index dropped to -112nT. For this study we have used RINEX files obtained from GNSS stations belonging to International GPS Service, IGS, EUREF Permanent Network, and University Navstar Consortium, UNAVCO, networks. The data has been divided into two groups in function of the region: Europe or North America. For each group we have used all the available stations. The RINEX files have been processed using a technique developed by Ciraolo (2012) which assumes the ionospheric thin shell model to obtain the vertical total electron content (vTEC) from the slant total electron content (sTEC) at the Ionospheric Pierce Point, IPP, the point where the line-of-sight between the satellite and the ground receiver intersects the ionosphere. The data were obtained at 1 minute sampling in periods of geomagnetic storms and quiet days close to them. In both storms a tongue of ionization, ToI, appeared over North America from afternoon to dusk (between 19:00 and 3:00 GMT). The behavior of the ionosphere over Europe was very different in eachcase. In July, the TEC decreased respect the quiet days during the ToI time. In the February storm the behavior of the ionosphere over Europe was similar to that of a quiet day but the following day appeared a phenomenom similar to the ToI. Ciraolo, L. (2012). Ionospheric Total Electron Content (TEC) from Global Positioning System. Personal Communication. Gonzlez, W.D., Joselyn, J. A., Kamide, Y., Kroehl, H. W., Rostoker, G., Tsurutani, B. T., Vasyliunas, V. M. (1994). What is a Geomagnetic Storm?. J. Geophys. Res., 99, 5771-5792, doi:10.1029/93JA02867.

  8. Seasonal dependence of magnetic field variations from subauroral latitude to the magnetic equator during geomagnetic sudden commencements

    NASA Astrophysics Data System (ADS)

    Shinbori, A.; Tsuji, Y.; Kikuchi, T.; Araki, T.; Ikeda, A.; Uozumi, T.; Solovyev, S. I.; Shevtsov, B.; Otadoy, R. S.; Utada, H.; Nagatsuma, T.; Hayashi, H.; Tsuda, T.; Yumoto, K.; Iugonet Project Team

    2010-12-01

    Seasonal dependence of diurnal variation of the main impulse (MI) of geomagnetic sudden commencements (SCs) has been investigated using the long-tern geomagnetic field data with high time resolution of 1 sec within a period from 1996 to 2008 provided from the NSWM [Kikuchi et al., 2008] and CPMN [Yumoto and the CPMN group, 2001] chains and the WDC for Geomagnetism, Kyoto. In the present analysis, we used the geomagnetic field data obtained from the 10 stations. In this study, we defined an SC phenomenon as a rapid increase of the SYM-H value with more than 5 nT and time variation in the SYM-H index. Then, we identified 3163 events of SCs in a period from January 1996 to 2008, which has no Pi 2 signature around 10 minutes at the SC onset. Moreover, the SC amplitude obtained at the above 10 stations has been normalized by that in the SYM-H index with latitude correction in order to minimize the different contribution of the rapid change in solar wind dynamic pressure. As a result, in sub-auroral (ZYK) and middle latitudes (MMB) tends to be larger in summer than in winter in all the magnetic local time. The peak-to-peak amplitude in the daytime sector strongly depends on solar zenith angle. These result imply that ionospheric currents (ICs) and field-aligned currents (FACs) generated during the MI phase of SC are enhanced due to the increase of ionospheric conductivity in summer. This feature suggests that SC current system is the voltage generator. On the other hand, the sesonal variation of SC amplitude in both the low latitude and magnetic equator showed quite a different signature from that in the sub-auroral and middle latitudes. The remarkable feature is that the equatorial enhancement of SC amplitude due to an intensification of the Pedersen currents via the Cowling effect tends to become smaller in summer, compared with that in winter. This tendency suggests that ionospheric conductivity does not depend on only the solar zenith angle. One of the implications of the equatorial seasonal dependence is that the ionospheric conductivity in the low latitude and at the magnetic equator modifies the variation of ionospheric structure around the E-region due to neutral drag of the ionospheric plasma along the magnetic field line via interaction between the meridional neutral wind and ionospheric E-region plasmas. Therefore, in order to verify the existence of the neutral wind and its seasonal dependence, we will need to analyze the thermospheric wind data obtained from the MF and meteor radars provided from the IUGONET database.

  9. Tree-stem diameter fluctuates with the lunar tides and perhaps with geomagnetic activity.

    PubMed

    Barlow, Peter W; Mikulecký, Miroslav; Střeštík, Jaroslav

    2010-11-01

    Our initial objective has been to examine the suggestion of Zürcher et al. (Nature 392:665–666, 1998) that the naturally occurring variations in stem diameter of two experimental trees of Picea alba were related to near simultaneous variations in the lunisolar tidal acceleration. The relationship was positive: Lunar peaks were roughly synchronous with stem diameter peaks. To extend the investigation of this putative relationship, additional data on stem diameter variations from six other tree species were gathered from published literature. Sixteen sets of data were analysed retrospectively using graphical representations as well as cosinor analysis, statistical cross-correlation and cross-spectral analysis, together with estimated values of the lunisolar tidal acceleration corresponding to the sites, dates and times of collection of the biological data. Positive relationships were revealed between the daily variations of stem diameter and the variations of the lunisolar tidal acceleration. Although this relationship could be mediated by a 24.8-h lunar rhythm, the presence of a solar rhythm of 24.0 h could not be ruled out. Studies of transpiration in two of the observed trees indicated that although this variable was not linked to stem diameter variation, it might also be subject to lunisolar gravitational regulation. In three cases, the geomagnetic Thule index showed a weak but reciprocal relationship with stem diameter variation, as well as a positive relationship with the lunisolar tidal force. In conclusion, it seems that lunar gravity alone could influence stem diameter variation and that, under certain circumstances, additional regulation may come from the geomagnetic flux. PMID:20393759

  10. Two-step forecast of geomagnetic storm using coronal mass ejection and solar wind condition

    PubMed Central

    Kim, R-S; Moon, Y-J; Gopalswamy, N; Park, Y-D; Kim, Y-H

    2014-01-01

    To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz ≤ −5 nT or Ey ≥ 3 mV/m for t≥ 2 h for moderate storms with minimum Dst less than −50 nT) and a Dst model developed by Temerin and Li (2002, 2006) (TL model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90%) than the forecasts based on the TL model (87%). However, the latter produces better forecasts for 24 nonstorm events (88%), while the former correctly forecasts only 71% of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80%) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81%) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪), all geomagnetic storms are correctly forecasted. PMID:26213515

  11. Quantitative maps of geomagnetic perturbation vectors during substorm onset and recovery

    PubMed Central

    Pothier, N M; Weimer, D R; Moore, W B

    2015-01-01

    We have produced the first series of spherical harmonic, numerical maps of the time-dependent surface perturbations in the Earth's magnetic field following the onset of substorms. Data from 124 ground magnetometer stations in the Northern Hemisphere at geomagnetic latitudes above 33° were used. Ground station data averaged over 5 min intervals covering 8 years (1998–2005) were used to construct pseudo auroral upper, auroral lower, and auroral electrojet (AU*, AL*, and AE*) indices. These indices were used to generate a list of substorms that extended from 1998 to 2005, through a combination of automated processing and visual checks. Events were sorted by interplanetary magnetic field (IMF) orientation (at the Advanced Composition Explorer (ACE) satellite), dipole tilt angle, and substorm magnitude. Within each category, the events were aligned on substorm onset. A spherical cap harmonic analysis was used to obtain a least error fit of the substorm disturbance patterns at 5 min intervals up to 90 min after onset. The fits obtained at onset time were subtracted from all subsequent fits, for each group of substorm events. Maps of the three vector components of the averaged magnetic perturbations were constructed to show the effects of substorm currents. These maps are produced for several specific ranges of values for the peak |AL*| index, IMF orientation, and dipole tilt angle. We demonstrate an influence of the dipole tilt angle on the response to substorms. Our results indicate that there are downward currents poleward and upward currents just equatorward of the peak in the substorms' westward electrojet. Key Points Show quantitative maps of ground geomagnetic perturbations due to substorms Three vector components mapped as function of time during onset and recovery Compare/contrast results for different tilt angle and sign of IMF Y-component PMID:26167445

  12. Underlying scaling relationships between solar activity and geomagnetic activity revealed by multifractal analyses

    NASA Astrophysics Data System (ADS)

    Yu, Zu-Guo; Anh, Vo; Eastes, Richard

    2014-09-01

    This paper identifies some scaling relationships between solar activity and geomagnetic activity. We examine the scaling properties of hourly data for two geomagnetic indices (ap and AE), two solar indices (solar X-rays Xl and solar flux F10.7), and two inner heliospheric indices (ion density Ni and flow speed Vs) over the period 1995-2001 by the universal multifractal approach and the traditional multifractal analysis. We found that the universal multifractal model (UMM) provides a good fit to the empirical K(q) and ?(q) curves of these time series. The estimated values of the Lvy index ? in the UMM indicate that multifractality exists in the time series for ap, AE, Xl, and Ni, while those for F10.7 and Vs are monofractal. The estimated values of the nonconservation parameter H of this model confirm that these time series are conservative which indicate that the mean value of the process is constant for varying resolution. Additionally, the multifractal K(q) and ?(q) curves, and the estimated values of the sparseness parameter C1 of the UMM indicate that there are three pairs of indices displaying similar scaling properties, namely ap and Xl, AE and Ni, and F10.7 and Vs. The similarity in the scaling properties of pairs (ap,Xl) and (AE,Ni) suggests that ap and Xl, AE and Ni are better correlatedin terms of scalingthan previous thought, respectively. But our results still cannot be used to advance forecasting of ap and AE by Xl and Ni, respectively, due to some reasons.

  13. Trends of ionospheric irregularities over African low latitude region during quiet geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Mungufeni, Patrick; Habarulema, John Bosco; Jurua, Edward

    2016-02-01

    The occurrence patterns of ionospheric irregularities during quiet geomagnetic conditions over the African low latitude region were analysed. GNSS-derived Total Electron Content of the ionosphere data during the period 2001-2012 were used. The data were obtained from Libreville, Gabon (0.35°N, 9.68°E, geographic, 8.05°S, magnetic), Mbarara, Uganda (0.60°S, 30.74°E, geographic, 10.22°S, magnetic), and Malindi, Kenya (2.99°S, 40.19°E, geographic, 12.42°S, magnetic). The rate of change of total electron content index greater than 0.5 TECU/Min were considered as severe ionospheric irregularities. For most of the time, the strength of ionospheric irregularities in March equinox were greater than those during September equinox over East Africa and an opposite observation was made over West Africa. These asymmetries might be due to the direction of the meridional winds during equinoxes over the different stations. Severity of ionospheric irregularity reduced from west towards the east. This might have been related to the decreasing geomagnetic field strength from east towards the west. This is the first study that reveals the equinoctial asymmetry is different in the West and East African sectors. Moreover, the importance of this study lies in the fact that it has used extensive data to examine the isolated and un-explained earlier observations of equinoctial asymmetry and longitudinal variation of ionospheric irregularities over the African low latitude region.

  14. Preliminary Analysis on the Interplanetary Cause of Geomagnetically Induced Current and Its Effect on Power Systems

    NASA Astrophysics Data System (ADS)

    Wang, Kai-Rang; Liu, Lian-Guang; Li, Yan

    2015-01-01

    Using the detected events of geomagnetically induced current (GIC) in the Ling'ao nuclear power plant from 2004 to 2005, and focusing on the interplanetary cause of GIC and its effect on power systems, we have analyzed the corresponding solar driving sources and interplanetary solar wind structures, and performed spectral analysis on the most intense GIC event by means of wavelet transform. The results of this study show that: (1) Most GIC events were driven mainly by the halo coronal mass ejections, the interplanetary cause of GIC events includes the shock sheath, magnetic cloud, and multiplex interplanetary solar wind structure. (2) Based on the strongest GIC event on 2001 November 9, we find that the fluctuation of GIC in the earlier stage was related to the magnetic cloud boundary layer, and the variation of GIC intensity in the later stage was caused by magnetic cloud itself. (3) Compared to the frequency of the power system (50 Hz), the GIC can be equivalent to a quasi direct current. The energy of the GIC is embodied in the two time intervals in the wavelet power spectrum: the first interval is shown as an impulsive type and with a weaker intensity, and the second one is stronger. Regarding to the cumulative time of the transformer temperature rise caused by GIC, the second interval has a longer duration than the first one. Hence, during the second interval, it is more harmful to the power systems and devices. (4) With a correlation analysis, the correlations of the SYM-H index and dBx/dt with the GIC are significantly stronger than those of other geomagnetic indices with the GIC.

  15. 40 CFR Appendix A to Subpart Aa of... - Applicability of General Provisions (40 CFR Part 63, Subpart A) to Subpart AA

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (40 CFR Part 63, Subpart A) to Subpart AA A Appendix A to Subpart AA of Part 63 Protection of... Hazardous Air Pollutants From Phosphoric Acid Manufacturing Plants Pt. 63, Subpt. AA, App. A Appendix A to Subpart AA of Part 63—Applicability of General Provisions (40 CFR Part 63, Subpart A) to Subpart AA 40...

  16. 40 CFR Appendix A to Subpart Aa of... - Applicability of General Provisions (40 CFR Part 63, Subpart A) to Subpart AA

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (40 CFR Part 63, Subpart A) to Subpart AA A Appendix A to Subpart AA of Part 63 Protection of... Subpart AA of Part 63Applicability of General Provisions (40 CFR Part 63, Subpart A) to Subpart AA 40 CFR...) Compliance with Opacity/VE Standards No Subpart AA does not include VE/opacity standards. 63.6(i)(1)...

  17. 40 CFR Appendix A to Subpart Aa of... - Applicability of General Provisions (40 CFR Part 63, Subpart A) to Subpart AA

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... (40 CFR Part 63, Subpart A) to Subpart AA A Appendix A to Subpart AA of Part 63 Protection of... Subpart AA of Part 63Applicability of General Provisions (40 CFR Part 63, Subpart A) to Subpart AA 40 CFR...) Compliance with Opacity/VE Standards No Subpart AA does not include VE/opacity standards. 63.6(i)(1)...

  18. An empirical probability density distribution of planetary ionosphere storms with geomagnetic precursors

    NASA Astrophysics Data System (ADS)

    Gulyaeva, Tamara; Stanislawska, Iwona; Arikan, Feza; Arikan, Orhan

    The probability of occurrence of the positive and negative planetary ionosphere storms is evaluated using the W index maps produced from Global Ionospheric Maps of Total Electron Content, GIM-TEC, provided by Jet Propulsion Laboratory, and transformed from geographic coordinates to magnetic coordinates frame. The auroral electrojet AE index and the equatorial disturbance storm time Dst index are investigated as precursors of the global ionosphere storm. The superposed epoch analysis is performed for 77 intense storms (Dst?-100 nT) and 227 moderate storms (-100index and Dst index. It is found that AE index better suits to serve as a precursor of the ionosphere storm than Dst index with onset of the average auroral AE storm occurring 6 h before the equatorial Dst storm onset for intense storms and 3 h in advance of moderate Dst storm. The similar space zones advancement of the ionosphere storm is observed with W index (pW+ and pW-) depicting maximum localized in the polar magnetic zone and minimum at magnetic equator. An empirical relation for pW+ and pW- with AE storm precursor is derived which enables the probability of occurrence of the ionosphere storm to be predicted with leading time of 1-2 h for the positive ionosphere storm and 9-10 h for the negative ionosphere storm. The ionosphere storm probability model is validated using data for 2 intense and 20 moderate geomagnetic storms occurred during 2013. Results are discussed in the paper. This study is supported by the joint grant of TUBITAK 112E568 and RFBR 13-02-91370-CT_a.

  19. Scintillation Monitoring Using Asymmetry Index

    NASA Astrophysics Data System (ADS)

    Shaikh, Muhammad Mubasshir; Mahrous, Ayman; Abdallah, Amr; Notarpietro, Riccardo

    Variation in electron density can have significant effect on GNSS signals in terms of propagation delay. Ionospheric scintillation can be caused by rapid change of such delay, specifically, when they last for a longer period of time. Ionospheric irregularities that account for scintillation may vary significantly in spatial range and drift with the background plasma at speeds of 45 to 130 m/sec. These patchy irregularities may occur several times during night, e.g. in equatorial region, with the patches move through the ray paths of the GNSS satellite signals. These irregularities are often characterized as either large scale (which can be as large as several hundred km in East-West direction and many times that in the North-South direction) or small scale (which can be as small as 1m). These small scale irregularities are regarded as the main cause of scintillation [1,2]. In normal solar activity conditions, the mid-latitude ionosphere is not much disturbed. However, during severe magnetic storms, the aurora oval extends towards the equator and the equator anomaly region may stretched towards poles extending the scintillation phenomena more typically associated with those regions into mid-latitudes. In such stormy conditions, the predicted TEC may deviate largely from the true value of the TEC both at low and mid-latitudes due to which GNSS applications may be strongly degraded. This work is an attempt to analyze ionospheric scintillation (S4 index) using ionospheric asymmetry index [3]. The asymmetry index is based on trans-ionospheric propagation between GPS and LEO satellites in a radio occultation (RO) scenario, using background ionospheric data provided by MIDAS [4]. We attempted to simulate one of the recent geomagnetic storms (NOAA scale G4) occurred over low/mid-latitudes. The storm started on 26 September 2011 at UT 18:00 and lasted until early hours of 27 September 2011. The scintillation data for the storm was taken from an ionospheric station in Cairo, Egypt (lat= 29.8641 , long= 31.3172 ). It was observed that the level of asymmetry was significantly increased during the main phase of the geomagnetic storm. This was due to the changes in ionization, which in turn produced large gradients along occulted ray path in the ionosphere. A very good correlation was found between the evaluated ionospheric asymmetry index and the S4 scintillation index. Additionally, the correlation between evaluated ionospheric asymmetry and errors related to the RO inversion products such as peak electron density (delta NmF2) and Vertical TEC (delta VTEC) estimates also showed promising results. This work is carried out under the framework of the TRANSMIT project (Training Research and Applications Network to Support the Mitigation of Ionospheric Threats - www.transmit-ionosphere.net). [1]Basu Sa. and Basu Su., (1981), Equatorial Scintillation - A Review, Journal of Atmospheric and Solar-Terrestrial Physics, 43, p. 473. [2]Davies K., (1990), Ionospheric Radio, IEEE Electromagnetic Waves Series 31, Peter Peregrinus Ltd. [3]Spencer, P., Mitchell, C.N., (2007) Imaging of fast moving electron-density structures in the polar cap, Annals of Geophysics, vol. 50, no. 3, pp. 427-434. [4]Shaikh, M.M., Notarpietro, R., Nava, B., (2013) The Impact of Spherical Symmetry Assumption on Radio Occultation Data Inversion in the Ionosphere: An Assessment Study, Advances in Space Research, doi: http://dx.doi.org/10.1016/j.asr.2013.10.025.

  20. Steady induction effects in geomagnetism. Part 1C: Geomagnetic estimation of steady surficial core motions: Application to the definitive geomagnetic reference field models

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    1993-01-01

    In the source-free mantle/frozen-flux core magnetic earth model, the non-linear inverse steady motional induction problem was solved using the method presented in Part 1B. How that method was applied to estimate steady, broad-scale fluid velocity fields near the top of Earth's core that induce the secular change indicated by the Definitive Geomagnetic Reference Field (DGRF) models from 1945 to 1980 are described. Special attention is given to the derivation of weight matrices for the DGRF models because the weights determine the apparent significance of the residual secular change. The derived weight matrices also enable estimation of the secular change signal-to-noise ratio characterizing the DGRF models. Two types of weights were derived in 1987-88: radial field weights for fitting the evolution of the broad-scale portion of the radial geomagnetic field component at Earth's surface implied by the DGRF's, and general weights for fitting the evolution of the broad-scale portion of the scalar potential specified by these models. The difference is non-trivial because not all the geomagnetic data represented by the DGRF's constrain the radial field component. For radial field weights (or general weights), a quantitatively acceptable explication of broad-scale secular change relative to the 1980 Magsat epoch must account for 99.94271 percent (or 99.98784 percent) of the total weighted variance accumulated therein. Tolerable normalized root-mean-square weighted residuals of 2.394 percent (or 1.103 percent) are less than the 7 percent errors expected in the source-free mantle/frozen-flux core approximation.

  1. Comparison between ARB and CARB processes on an AA5754/AA6061 composite

    NASA Astrophysics Data System (ADS)

    Verstraete, K.; Helbert, A.-L.; Brisset, F.; Baudin, T.

    2014-08-01

    The present work aims to compare two processes: Accumulative Roll Bonding and Cross Accumulative Roll Bonding (CARB). Both processes consist in the repetition of rolling but the second technique adds a 90° rotation of the sheet around its normal direction between each rolling. Microstructure, mechanical properties and texture were compared for both processes on an AA5754/AA6061 composite. As a result a thinner and less elongated microstructure was obtained in the CARB process leading to an isotropy and an improvement of the mechanical properties. Besides, the texture was characterized by the rotated Cube component for both processes but for CARB it is of less strength.

  2. International Geomagnetic Reference Field: the 12th generation

    NASA Astrophysics Data System (ADS)

    Thébault, Erwan; Finlay, Christopher C.; Beggan, Ciarán D.; Alken, Patrick; Aubert, Julien; Barrois, Olivier; Bertrand, Francois; Bondar, Tatiana; Boness, Axel; Brocco, Laura; Canet, Elisabeth; Chambodut, Aude; Chulliat, Arnaud; Coïsson, Pierdavide; Civet, François; Du, Aimin; Fournier, Alexandre; Fratter, Isabelle; Gillet, Nicolas; Hamilton, Brian; Hamoudi, Mohamed; Hulot, Gauthier; Jager, Thomas; Korte, Monika; Kuang, Weijia; Lalanne, Xavier; Langlais, Benoit; Léger, Jean-Michel; Lesur, Vincent; Lowes, Frank J.; Macmillan, Susan; Mandea, Mioara; Manoj, Chandrasekharan; Maus, Stefan; Olsen, Nils; Petrov, Valeriy; Ridley, Victoria; Rother, Martin; Sabaka, Terence J.; Saturnino, Diana; Schachtschneider, Reyko; Sirol, Olivier; Tangborn, Andrew; Thomson, Alan; Tøffner-Clausen, Lars; Vigneron, Pierre; Wardinski, Ingo; Zvereva, Tatiana

    2015-12-01

    The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth's magnetic field.

  3. Linking CMEs-ICMEs-Geomagnetic Storms during 1996 - 2012

    NASA Astrophysics Data System (ADS)

    Camelia Talpeanu, Dana; Stan, Lucian; Mierla, Marilena; Rodriguez, Luciano; Zhukov, Andrei; Besliu-Ionescu, Diana

    2014-05-01

    During the period 1996 - 2012 there were 401 coronal mass ejections (CMEs) which arrived at the Earth (see the on-line catalogue of Richardson and Cane). The solar counterpart of these interplanetary CMEs (ICMEs) was found for 379 events and for 22 the identification was not possible because of the data gaps. Out of the identified events, the CMEs with sources towards solar west are more numerous compared with the ones having sources at east. Also, there are more CMEs, correlated with ICMEs, that are coming from the northern hemisphere, compared with the ones coming from the southern hemisphere. It was found that majority of the ICMEs produced minor or no geomagnetic storms. The intense geomagnetic storms are associated with CMEs coming from regions closer to the central meridian as seen from the Earth. A study of these events separated on different phases of the solar cycle is also done.

  4. Exploiting the geomagnetic distortion of inclined atmospheric showers

    NASA Astrophysics Data System (ADS)

    Billoir, Pierre; Settimo, Mariangela; Blanco, Miguel

    2016-02-01

    We propose a novel approach to the determination of the nature of ultra-high energy cosmic rays by exploiting the geomagnetic deviation of muons in nearly horizontal showers. The distribution of muons at ground level is well described by a simple parameterization providing a few shape parameters tightly correlated to Xmax?, the depth of maximal muon production, which is a mass indicator tightly correlated to the usual parameter Xmax, the depth of maximal development of the shower. We show that some constraints can be set on the predictions of hadronic models, especially by combining the geomagnetic distortion with standard measurements of the longitudinal profile. We discuss the precision needed to obtain significant results, and we propose a schematic layout of a detector.

  5. Plasmapause location under quiet geomagnetic conditions (Kp ? 1): THEMIS observations

    NASA Astrophysics Data System (ADS)

    Kwon, H.-J.; Kim, K.-H.; Jee, G.; Park, J.-S.; Jin, H.; Nishimura, Y.

    2015-09-01

    We statistically examined the plasmapause location (Lpp) under quiet geomagnetic conditions (Kp ? 1) using the electron density inferred from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft potential for 2 year period (2008 and 2009). Five hundred forty-three Lpp samples were identified under steady quiet conditions with Kp values ? 1 during 12 h prior to the plasmapause crossing. From our large data set, we determined the medians and means of Lpp in L and magnetic local time (MLT). They are located near geosynchronous orbit and nearly circular. The Lpp medians show a slight bulge located in postdusk sector. Comparing with previous models, our median or mean Lpp is extended 1-2 L from the Earth than the model Lpp along the local time from 0800 to 2400 MLT. That is, Lpp locations in the previous models are underestimated during quiet geomagnetic conditions.

  6. The geomagnetic secular variation S parameter: A mathematical artifact

    NASA Astrophysics Data System (ADS)

    Linder, J. M.; Gilder, S. A.

    2011-12-01

    Secular variation, the change in the Earth's magnetic field through time, reflects the energy state of the geodynamo. Secular variation is commonly quantified by the standard deviation of the angular distances of the virtual geomagnetic poles to their mean pole, known as the S value. The S value has long been thought to exhibit latitude dependence [S(?)] whose origin is widely attributed to a combination of time-varying dipole and non-dipole components. The slope, magnitude and uncertainty of S(?) are taken as a basis to model the geomagnetic field and understand its evolution. Here we show that variations in S stem from a mathematical aberration of the conversion from directions to poles. A new method to quantify secular variation is proposed.

  7. Simulating Geomagnetically Induced Currents in the Irish Power Network

    NASA Astrophysics Data System (ADS)

    Jones, A. G.; Blake, S. P.; Gallagher, P.; McCauley, J.; Hogg, C.; Beggan, C.; Thomson, A. W. P.; Kelly, G.; Walsh, S.

    2014-12-01

    Geomagnetic storms are known to cause geomagnetically induced currents (GICs) which can damage or destroy transformers on power grids. Previous studies have examined the vulnerability of power networks in countries such as the UK, New Zealand, Canada and South Africa. Here we describe the application of a British Geological Survey (BGS) thin-sheet conductivity model to compute the geo-electric field from the variation of the magnetic field, in order to better quantify the risk of space weather to Ireland's power network. This was achieved using DIAS magnetotelluric data from across Ireland. As part of a near-real-time warning package for Eirgrid (who oversee Ireland's transmission network), severe storm events such as the Halloween 2003 storm and the corresponding GIC flows at transformers are simulated.

  8. Low-altitude trapped protons at the geomagnetic equator

    NASA Technical Reports Server (NTRS)

    Guzik, T. G.; Miah, M. A.; Mitchell, J. M.; Wefel, J. P.

    1989-01-01

    Geomagnetically trapped protons in the 0.6- to 9-MeV energy range were measured at latitudes near the geomagnetic equator by the Phoenix 1 experiment on board the S81-1 mission from May to November 1982. The protons show a distribution in latitude along the line of minimum magnetic field strength with a full width at half maximum of about 10 deg but with no appreciable longitudinal variation. Between 170 and 290 Km the peak proton flux shows a fifth-power altitude dependence, in contrast to previous measurements at higher altitudes, possibly demonstrating source attenuation. The efficiency of the telescope is calculated as a function of particle pitch angle and used to investigate the time dependence (1969-1982) of the intensity.

  9. Observations of interactions between interplanetary and geomagnetic fields

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Magnetospheric effects associated with variations of the north-south component of the interplanetary magnetic field are examined in light of recent recent experimental and theoretical results. Although the occurrence of magnetospheric substorms is statistically related to periods of southward interplanetary magnetic field, the details of the interaction are not understood. In particular, attempts to separate effects resulting directly from the interaction between the interplanetary and geomagnetic fields from those associated with substorms have produced conflicting results. The transfer of magnetic flux from the dayside to the nightside magnetosphere is evidenced by equatorward motion of the polar cusp and increases of the magnetic energy density in the lobes of the geomagnetic tail. The formation of a macroscopic X-type neutral line at tail distances less than 35 R sub E appears to be a substorm phenomenon.

  10. Spectral Study of Polarity Reversals in the Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Valbuena, C.; Gomez Perez, N.

    2013-05-01

    Self-consistent models of the dynamo process in the Earth's core have reached a state where they can be used to understand specific morphological and temporal properties of the geomagnetic field. In this work we study numerical dynamos in terms of the multipole components before, during and after polarity reversals. The numerical algorithm (MagIC 3.47) uses the Boussinesq approximation and was originally developed by G. Glatzmaier and most recently optimized by J. Wicht. Paleomagnetic studies provide limited information on the duration, intensity, geometry and orientation of the field during reversals and excursions. We will show how the magnitude of multipole components evolves in time. We will present how multipolar term magnitudes are correlated with the occurrence of geomagnetic reversals and excursions.

  11. Study of Tatun Volcanoes by Fluxgate Geomagnetic Data

    NASA Astrophysics Data System (ADS)

    Yang, D.; Yen, H. Y.; Chen, C. H.

    2014-12-01

    Tatun volcanoes, located at northern Taipei city, the capital city of Taiwan, are still active according to the previous studies. Thus, construct the geometry of the volcanic structures of Tatun volcanoes is necessary. We used 3-component geomagnetic data from two temporal fluxgate magnetometers and YMM(Yangming mountain) a permanent station from April to August 2014. The susceptibility of igneous rock is generally larger than metamorphic and sedimentary rocks, thus we use the Parkinson vectors derived from 3-component geomagnetic data through the magnetic transfer function to find out the location and geometry of the igneous rock under Tatun volcanoes. In order to know the depth of the anomalies, we used the magnetotelluric data of previous study that are in the vicinity of three stations to compute the skin depth, which show the relationship between frequency and the penetration depth of the electromagnetic wave. Then, we use the magnetic transfer function to calculate the azimuth of the anomalies at a specific depth.

  12. Transient cosmic ray increase associated with a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Kudo, S.; Wada, M.; Tanskanen, P.; Kodama, M.

    1985-01-01

    On the basis of worldwide network data of cosmic ray nucleonic components, the transient cosmic ray increase due to the depression of cosmic ray cutoff rigidity during a severe geomagnetic storm was investigated in terms of the longitudinal dependence. Multiple correlation analysis among isotropic and diurnal terms of cosmic ray intensity variations and Dst term of the geomagnetic field is applied to each of various station's data. It is shown that the amplitude of the transient cosmic ray increase associated with Dst depends on the local time of the station, and that its maximum phase is found in the evening sector. This fact is consistent with the theoretical estimation based on the azimuthally asymmetric ring current model for the magnetic DS field.

  13. Acceleration and loss of relativistic electrons during small geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Anderson, B. R.; Millan, R. M.; Reeves, G. D.; Friedel, R. H. W.

    2015-12-01

    Past studies of radiation belt relativistic electrons have favored active storm time periods, while the effects of small geomagnetic storms (Dst > -50 nT) have not been statistically characterized. In this timely study, given the current weak solar cycle, we identify 342 small storms from 1989 through 2000 and quantify the corresponding change in relativistic electron flux at geosynchronous orbit. Surprisingly, small storms can be equally as effective as large storms at enhancing and depleting fluxes. Slight differences exist, as small storms are 10% less likely to result in flux enhancement and 10% more likely to result in flux depletion than large storms. Nevertheless, it is clear that neither acceleration nor loss mechanisms scale with storm drivers as would be expected. Small geomagnetic storms play a significant role in radiation belt relativistic electron dynamics and provide opportunities to gain new insights into the complex balance of acceleration and loss processes.

  14. Effects of geomagnetically-induced currents on HVDC converter operation

    SciTech Connect

    Mohan, N.; Albertson, V.D.; Bahrman, M.P.; Kappenman, K.G.; Speak, T.J.

    1982-11-01

    Electrons and protons emitted by a solar flare can be captured by the Earth's magnetic field. The resulting transient in the geomagnetic field can produce quasi-dc currents in electric power systems. These geomagnetically-induced currents (GIC) in excess of 100 amps have been measured in the transformer neutral leads. With the practice of using EHV and UHV lines for transmitting ac power over long distances and because the systems are more solidly grounded, the problems posed by GIC have become more severe. This paper presents the consequences of transformer halfcycle saturation on the operation of HVDC converter terminals. A detailed computer simulation of the Square Butte HVDC system reveals that the large values of GIC can cause enough distortion in the ac system voltage at the inverter end to prevent normal system operation. Moreover, the amount of harmonics generated could overload the ac as well as the dc-side filters.

  15. Earth orientation parameters: excitation by atmosphere, oceans and geomagnetic jerks

    NASA Astrophysics Data System (ADS)

    Vondrak, Jan; Ron, Cyril

    2015-08-01

    It is well known that geophysical fluids (atmosphere, oceans) excite Earth orientation. The influence is known to be dominant for polar motion, partly responsible for length-of-day changes, and very small effects are now observable also in nutation. Very recently several authors (Holme and de Viron 2005, Gibert and le Mouel 2008, Malkin 2013) noted that sudden changes of Earth's speed of rotation and phase/amplitude of the free motions of its spin axis (Chandler wobble, Free core nutation) occur near the epochs of geomagnetic jerks (GMJ - rapid changes of the secular variations of geomagnetic field). By using the numerical integration of broad-band Liouville equations (Brzezinski 1994) we demonstrate that if non-periodical bell-like excitations of limited length (app. 1 year) around the epochs of GMJ are added to atmospheric and oceanic excitations, the agreement between observed and calculated Earth orientation parameters is improved significantly.

  16. Ionosphere and atmosphere of the moon in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Daily, W. D.; Barker, W. A.; Parkin, C. W.; Clark, M.; Dyal, P.

    1977-01-01

    The paper presents calculations of the densities and energies of the various constituents of the lunar ionosphere during the time that the moon is in the geomagnetic tail; the surface concentrations of neon and argon are calculated from a theoretical model to be 3,900 and 1,700, respectively. It is found that a hydrostatic model of the ionospheric plasma is inadequate because the gravitational potential energy of the plasma is considerably smaller than its thermal energy. A hydrodynamic model, comparable to that used to describe the solar wind, is developed to obtain plasma densities and flow velocities as functions of altitude. The electromagnetic properties of the quiescent ionosphere are then investigated, and it is concluded that plasma effects on lunar induction can be neglected for quiescent conditions in the geomagnetic tail lobes.

  17. Characteristics of long-term variation in the amlitude of the geomagnetic solar quiet (Sq) daily variation using the Inter-university Upper atmosphere Gobal Observation NETwork (IUGONET) data analysis system

    NASA Astrophysics Data System (ADS)

    Shinbori, A.; Koyama, Y.; Nose, M.; Hori, T.; Otsuka, Y.; Yatagai, A. I.

    2014-12-01

    Characteristics of long-term variation in the amplitude of solar quiet geomagnetic field daily variation (Sq) have been investigated using 1-hour geomagnetic field data obtained from 69 geomagnetic stations in a period of 1947-2013. In the present data analysis, we took advantage of the IUGONET data analysis system. The Sq amplitude clearly showed a 10-12 year solar activity dependence and it tended to enhance during each solar maximum. During the minimum of solar cycle 23/24 in 2008-2009, the Sq amplitude became the smallest in the investigated period. The relationship between the solar F10.7 index and Sq amplitude is approximately linear but 64 percent of geomagnetic stations show a weak nonlinear dependence on the solar F10.7 index. In order to remove the effect of solar activity seen in the long-term variation of the Sq amplitude, we calculated a linear or second order fitting curve between the solar F10.7 index and Sq amplitude during 1947-2013, and examined the residual Sq amplitude, which is defined as the deviation from the fitting curve. As a result, a majority of the trends in the residual Sq amplitude that passed through a trend test showed a negative value in a wide region. This tendency was relatively strong in Europe, India, the eastern part of Canada, and New Zealand. The relationship between the magnetic field intensity and residual Sq amplitude showed an anti-correlation for about 71 percent of geomagnetic stations. On the other hand, the residual Sq amplitude in the equatorial station (Addis Ababa) was anti-correlated with the absolute value of the magnetic field inclination. This implies the movement of the equatorial electrojet due to the secular variation of the ambient magnetic field.

  18. Temporal fluctuations of the geomagnetic field affect pigeons' entire homing flight.

    PubMed

    Schiffner, Ingo; Wiltschko, Roswitha

    2011-07-01

    Tracks of pigeons, recorded with the help of GPS-receivers from two sites 30 km north and south of the Frankfurt loft, were analyzed in view of an influence of irregular fluctuations of the geomagnetic field. The data obtained were correlated with indices characterizing different aspects of these fluctuations. We found the best correlations with the index quantifying the average amplitude of the magnetic disturbance, and with an index that quantifies the average variability of the magnetic field on the day of release: stronger and more variable fluctuations lead to a counter-clockwise shift of the mean headings during the initial phase at the release site and the following departure phase, but not during the final homing phase leading to the loft. The steadiness of flight was not affected during the initial phase; however, during the later parts of the homing flight, stronger fluctuations, as well as higher variability in the magnetic field led to a marked decrease in steadiness. This continuing effect of magnetic fluctuations indicates that magnetic factors not only affect the beginning, but remain an integral part of the pigeons' navigational processes during the entire homing flight. PMID:21451981

  19. Effect of Cross-Correlation on Geomagnetic Forecast Accuracies

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

    Surface geomagnetic observation can determine up to degree L = 14 time-varying spherical harmonic coefficients of the poloidal magnetic field. Assimilation of these coefficients to numerical dynamo simulation could help us understand better the dynamical processes in the Earth's outer core, and to provide more accurate forecast of geomagnetic secular variations (SV). In our previous assimilation studies, only the poloidal magnetic field in the core is corrected by the observations in the analysis. Unobservable core state variables (the toroidal magnetic field and the core velocity field) are corrected via the dynamical equations of the geodynamo. Our assimilation experiments show that the assimilated core state converges near the CMB, implying that the dynamo state is strongly constrained by surface geomagnetic observations, and is pulled closer to the truth by the data. We are now carrying out an ensemble of assimilation runs with 1000 years of geomagnetic and archeo/paleo magnetic record. In these runs the cross correlation between the toroidal and the poloidal magnetic fields is incorporated into the analysis. This correlation is derived from the physical boundary conditions of the toroidal field at the core-mantle boundary (CMB). The assimilation results are then compared with those of the ensemble runs without the cross-correlation, aiming at understanding two fundamental issues: the effect of the crosscorrelation on (1) the convergence of the core state, and (2) the SV prediction accuracies. The constrained dynamo solutions will provide valuable insights on interpreting the observed SV, e.g. the near-equator magnetic flux patches, the core-mantle interactions, and possibly other geodynamic observables.

  20. The geomagnetically trapped radiation environment: A radiological point of view

    NASA Technical Reports Server (NTRS)

    Holly, F. E.

    1972-01-01

    The regions of naturally occurring, geomagnetically trapped radiation are briefly reviewed in terms of physical parameters such as; particle types, fluxes, spectrums, and spatial distributions. The major emphasis is placed upon a description of this environment in terms of the radiobiologically relevant parameters of absorbed dose and dose-rate and a discussion of the radiological implications in terms of the possible impact on space vehicle design and mission planning.

  1. Double streams of protons in the distant geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Villante, U.; Lazarus, A. J.

    1975-01-01

    Two intermingled streams of protons have been observed in the distant geomagnetic tail. The number densities of the two streams are comparable, and their velocity difference tends to lie along the field direction. The lower-velocity stream is probably composed of magnetosheath protons which have diffused through the boundary of the distant tail. The higher-velocity stream appears to originate in the field reversal region.

  2. New evidence for geomagnetically trapped anomalous cosmic rays

    SciTech Connect

    Cummings, J.R.; Cummings, A.C.; Mewaldt, R.A.; Selesnick, R.S.; Stone, E.C. ); Rosenvinge, T.T. von )

    1993-09-15

    This article presents data from the SAMPEX satellite of trapped heavy ions in the ionosphere, with energies greater than 15 MeV/nucleon. The data shows trapped He, N, O, and Ne. These ions are thought to be of cosmic ray origin, and to have been trapped by the geomagnetic field due to the loss of electrons due to scattering events in the upper atmosphere.

  3. Space Weather Monitoring for ISS Geomagnetic Storm Studies

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Parker, Neergaard

    2013-01-01

    The International Space Station (ISS) space environments community utilizes near real time space weather data to support a variety of ISS engineering and science activities. The team has operated the Floating Potential Measurement Unit (FPMU) suite of plasma instruments (two Langmuir probes, a floating potential probe, and a plasma impedance probe) on ISS since 2006 to obtain in-situ measurements of plasma density and temperature along the ISS orbit and variations in ISS frame potential due to electrostatic current collection from the plasma environment (spacecraft charging) and inductive (vxB) effects from the vehicle motion across the Earth s magnetic field. An ongoing effort is to use FPMU for measuring the ionospheric response to geomagnetic storms at ISS altitudes and investigate auroral charging of the vehicle as it passes through regions of precipitating auroral electrons. This work is challenged by restrictions on FPMU operations that limit observation time to less than about a third of a year. As a result, FPMU campaigns ranging in length from a few days to a few weeks are typically scheduled weeks in advance for ISS engineering and payload science activities. In order to capture geomagnetic storm data under these terms, we monitor near real time space weather data from NASA, NOAA, and ESA sources to determine solar wind disturbance arrival times at Earth likely to be geoeffective (including coronal mass ejections and high speed streams associated with coronal holes) and activate the FPMU ahead of the storm onset. Using this technique we have successfully captured FPMU data during a number of geomagnetic storm periods including periods with ISS auroral charging. This presentation will describe the strategies and challenges in capturing FPMU data during geomagnetic storms, the near real time space weather resources utilized for monitoring the space weather environment, and provide examples of auroral charging data obtained during storm operations.

  4. Lunar-Modulated Geomagnetic Orientation by a Marine Mollusk

    NASA Astrophysics Data System (ADS)

    Lohmann, Kenneth J.; Willows, A. O. Dennis

    1987-01-01

    Behavioral experiments indicated that the marine opisthobranch mollusk Tritonia diomedea can derive directional cues from the magnetic field of the earth. The magnetic direction toward which nudibranchs spontaneously oriented in the geomagnetic field showed recurring patterns of variation correlated with lunar phase, suggesting that the behavioral response to magnetism is modulated by a circa-lunar rhythm. The discovery of a magnetic sense in a mollusk with giant, reidentifiable neurons provides a unique opportunity to study the cellular mechanisms underlying magnetic field detection.

  5. Coronal mass ejections - The link between solar and geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.

    1993-01-01

    The phenomenon of coronal mass ejections (CME) is examined with reference to recent work in this field. In particular, attention is given to CMEs close to the sun, CMEs in interplanetary space, solar cycle variations of CMEs, and magnetic field topology and the problem of magnetic flux balance in interplanetary space. It is demonstrated that transient ejections of material from the sun are the cause of almost all large nonrecurrent geomagnetic substorms, as originally suggested by Chapman and his colleagues.

  6. Improving CTIPe neutral density response and recovery during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Fedrizzi, M.; Fuller-Rowell, T. J.; Codrescu, M.; Mlynczak, M. G.; Marsh, D. R.

    2013-12-01

    The temperature of the Earth's thermosphere can be substantially increased during geomagnetic storms mainly due to high-latitude Joule heating induced by magnetospheric convection and auroral particle precipitation. Thermospheric heating increases atmospheric density and the drag on low-Earth orbiting satellites. The main cooling mechanism controlling the recovery of neutral temperature and density following geomagnetic activity is infrared emission from nitric oxide (NO) at 5.3 micrometers. NO is produced by both solar and auroral activity, the first due to solar EUV and X-rays the second due to dissociation of N2 by particle precipitation, and has a typical lifetime of 12 to 24 hours in the mid and lower thermosphere. NO cooling in the thermosphere peaks between 150 and 200 km altitude. In this study, a global, three-dimensional, time-dependent, non-linear coupled model of the thermosphere, ionosphere, plasmasphere, and electrodynamics (CTIPe) is used to simulate the response and recovery timescales of the upper atmosphere following geomagnetic activity. CTIPe uses time-dependent estimates of NO obtained from Marsh et al. [2004] empirical model based on Student Nitric Oxide Explorer (SNOE) satellite data rather than solving for minor species photochemistry self-consistently. This empirical model is based solely on SNOE observations, when Kp rarely exceeded 5. During conditions between Kp 5 and 9, a linear extrapolation has been used. In order to improve the accuracy of the extrapolation algorithm, CTIPe model estimates of global NO cooling have been compared with the NASA TIMED/SABER satellite measurements of radiative power at 5.3 micrometers. The comparisons have enabled improvement in the timescale for neutral density response and recovery during geomagnetic storms. CTIPe neutral density response and recovery rates are verified by comparison CHAMP satellite observations.

  7. Impact of geomagnetic events on atmospheric chemistry and dynamics

    NASA Astrophysics Data System (ADS)

    Suter, I.; Zech, R.; Anet, J. G.; Peter, T.

    2013-12-01

    Geomagnetic events, i.e. short periods in time with much weaker geomagnetic fields and substantial changes in the position of the geomagnetic pole, occurred repeatedly in the Earth's history, e.g. the Laschamp Event about 41 kyr ago. Although the next such event is certain to come, little is known about the timing and possible consequences for the state of the atmosphere and the ecosystems. Here we use the global chemistry climate model SOCOL-MPIOM to simulate the effects of geomagnetic events on atmospheric ionization, chemistry and dynamics. Our simulations show significantly increased concentrations of nitrogen oxides (NOx) in the entire stratosphere, especially over Antarctica (+15%), due to enhanced ionization. Hydrogen oxides (HOx) are also produced in greater amounts (up to +40%) in the tropical and subtropical lower stratosphere, while their destruction by reactions with enhanced NOx prevails over the poles and in high altitudes (by -5%). Stratospheric ozone concentrations decrease globally above 20 km by 1-2% and at the northern hemispheric tropopause by up to 5% owing to the accelerated NOx-induced destruction. A 5% increase is found in the southern lower stratosphere and troposphere. In response to these changes in ozone and the concomitant changes in atmospheric heating rates, the Arctic vortex intensifies in boreal winter, while the Antarctic vortex weakens in austral winter and spring. Surface wind anomalies show significant intensification of the southern westerlies at their poleward edge during austral winter and a pronounced northward shift in spring. This is analogous to today's poleward shift of the westerlies due to the ozone hole. It is challenging to robustly infer precipitation changes from the wind anomalies, and it remains unclear, whether the Laschamp Event could have caused the observed glacial maxima in the southern Central Andes. Moreover, a large impact on the global climate seems unlikely.

  8. Types and Characteristics of Data for Geomagnetic Field Modeling

    NASA Technical Reports Server (NTRS)

    Langel, R. A. (Editor); Baldwin, R. T. (Editor)

    1992-01-01

    Given here is material submitted at a symposium convened on Friday, August 23, 1991, at the General Assembly of the International Union of Geodesy and Geophysics (IUGG) held in Vienna, Austria. Models of the geomagnetic field are only as good as the data upon which they are based, and depend upon correct understanding of data characteristics such as accuracy, correlations, systematic errors, and general statistical properties. This symposium was intended to expose and illuminate these data characteristics.

  9. Transport from chaotic orbits in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Horton, W.; Tajima, T.

    1991-01-01

    The rapid change in direction and magnitude of the magnetic field vector in crossing the quasi-neutral sheet in the geomagnetic tail leads to deterministic Hamiltonian chaos. The finite correlation times in the single particle orbits due to the continuum of orbital frequencies leads to well-defined collisionless transport coefficients. The transport coefficients are derived for plasma trapped in the quasi-neutral sheet.

  10. AAS Special Session: Policy Making in Astronomy

    NASA Astrophysics Data System (ADS)

    Cardelli, J. A.; Massa, D.

    1995-12-01

    The professional astronomical community today is more diverse than at any time in its history. Individuals participating in creative research programs can be found in a wide range of positions. This type of diversity, which mixes research, education, and service (e.g. contract) work, represents the strength of contemporary astronomy. While recognizing the unavoidable reductions in funding and restructuring of organizations like NASA, it is imperative that the significance of the current diversity be considered during these processes. Creative ideas are one of the cornerstones of quality research, and they can originate anywhere. Consequently, it is essential that adequate research resources remain available for free and open competition by all astronomers. Our goal in this session is to bring together officials from the AAS, NASA, and the NSF to discuss how the policy and decision making process operates and whether it should be changed to better serve the general needs of the professional astronomical community. Examples of the issues we believe are important include: In establishing new policy, how can the needs of the average research astronomer be better addressed? How could input from such astronomers be provided to those who craft NASA/NSF policy? How can/should the AAS serve as an interface between policy/decision making bodies and its membership? Should the AAS membership become more actively/effectively involved in the decision making process and, if so, how? More information on this session and related issues can be found at the Association of Research Astronomers Home Page: http://www.phy.vill.edu/astro/faculty/ara/ara_home.htm

  11. Evidence that pigeons orient to geomagnetic intensity during homing.

    PubMed

    Dennis, Todd E; Rayner, Matt J; Walker, Michael M

    2007-05-01

    The influence of the Earth's magnetic field on locomotory orientation has been studied in many taxa but is best understood for homing pigeons (Columba livia). Effects of experimentally induced and naturally occurring perturbations in the geomagnetic field suggest that pigeons are sensitive to changes in geomagnetic parameters. However, whether pigeons use the Earth's magnetic field for position determination remains unknown. Here we report an apparent orientation to the intensity gradient of the geomagnetic field observed in pigeons homing from sites in and around a magnetic anomaly. From flight trajectories recorded by GPS-based tracking devices, we noted that many pigeons released at unfamiliar sites initially flew, in some cases up to several kilometres, in directions parallel and/or perpendicular to the bearing of the local intensity field. This behaviour occurred irrespective of the homeward direction and significantly more often than what was expected by random chance. Our study describes a novel behaviour which provides strong evidence that pigeons when homing detect and respond to spatial variation in the Earth's magnetic field--information of potential use for navigation. PMID:17301015

  12. Geomagnetic Secular Variation Prediction with Thermal Heterogeneous Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Tangborn, Andrew; Jiang, Weiyuan

    2011-01-01

    It has long been conjectured that thermal heterogeneity at the core-mantle boundary (CMB) affects the geodynamo substantially. The observed two pairs of steady and strong magnetic flux lobes near the Polar Regions and the low secular variation in the Pacific over the past 400 years (and perhaps longer) are likely the consequences of this CMB thermal heterogeneity. There are several studies on the impact of the thermal heterogeneity with numerical geodynamo simulations. However, direct correlation between the numerical results and the observations is found very difficult, except qualitative comparisons of certain features in the radial component of the magnetic field at the CMB. This makes it difficult to assess accurately the impact of thermal heterogeneity on the geodynamo and the geomagnetic secular variation. We revisit this problem with our MoSST_DAS system in which geomagnetic data are assimilated with our geodynamo model to predict geomagnetic secular variations. In this study, we implement a heterogeneous heat flux across the CMB that is chosen based on the seismic tomography of the lowermost mantle. The amplitude of the heat flux (relative to the mean heat flux across the CMB) varies in the simulation. With these assimilation studies, we will examine the influences of the heterogeneity on the forecast accuracies, e.g. the accuracies as functions of the heterogeneity amplitude. With these, we could be able to assess the model errors to the true core state, and thus the thermal heterogeneity in geodynamo modeling.

  13. Estimation of cold plasma outflow during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Haaland, S.; Eriksson, A.; André, M.; Maes, L.; Baddeley, L.; Barakat, A.; Chappell, R.; Eccles, V.; Johnsen, C.; Lybekk, B.; Li, K.; Pedersen, A.; Schunk, R.; Welling, D.

    2015-12-01

    Low-energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space where spacecraft attain a positive charge due to solar illumination. Cold ions are therefore shielded from the satellite particle detectors. Furthermore, spacecraft can only cover key regions of ion outflow during segments of their orbit, so additional complications arise if continuous longtime observations, such as during a geomagnetic storm, are needed. In this paper we suggest a new approach, based on a combination of synoptic observations and a novel technique to estimate the flux and total outflow during the various phases of geomagnetic storms. Our results indicate large variations in both outflow rates and transport throughout the storm. Prior to the storm main phase, outflow rates are moderate, and the cold ions are mainly emanating from moderately sized polar cap regions. Throughout the main phase of the storm, outflow rates increase and the polar cap source regions expand. Furthermore, faster transport, resulting from enhanced convection, leads to a much larger supply of cold ions to the near-Earth region during geomagnetic storms.

  14. Midlatitude cooling caused by geomagnetic field minimum during polarity reversal

    PubMed Central

    Kitaba, Ikuko; Hyodo, Masayuki; Katoh, Shigehiro; Dettman, David L.; Sato, Hiroshi

    2013-01-01

    The climatic effects of cloud formation induced by galactic cosmic rays (CRs) has recently become a topic of much discussion. The CRcloud connection suggests that variations in geomagnetic field intensity could change climate through modulation of CR flux. This hypothesis, however, is not well-tested using robust geological evidence. Here we present paleoclimate and paleoenvironment records of five interglacial periods that include two geomagnetic polarity reversals. Marine oxygen isotope stages 19 and 31 contain both anomalous cooling intervals during the sea-level highstands and the MatuyamaBrunhes and Lower Jaramillo reversals, respectively. This contrasts strongly with the typical interglacial climate that has the temperature maximum at the sea-level peak. The cooling occurred when the field intensity dropped to <40% of its present value, for which we estimate >40% increase in CR flux. The climate warmed rapidly when field intensity recovered. We suggest that geomagnetic field intensity can influence global climate through the modulation of CR flux. PMID:23297205

  15. Disappearing solar filaments: A useful predictor of geomagnetic activity

    SciTech Connect

    Joselyn, J.A.; McIntosh, P.S.

    1981-06-01

    Disappearing solar filaments have long been suspected as an indicator of terrestrial magnetic disturbances. However, because filament disappearances are a common solar event and because they failed as a candidate source for M region (recurrent) magnetic disturbances, their potential utility as a forecasting aid for geomagnetic storms has largely been neglected. A search for possible solar sources of geomagnetic storms from June 1976 through June 1979 has revealed that a significant number of the storms, including the two largest, can only be associated with filament disappearances. This result is supported by the many recent papers studying SKYLAB and other observations of coronal transients which always find a strong correlation between those transients and eruptive prominences. By analyzing the physical characteristics of those disapearances which procede magnetic storms and those which do not, some tentative guidelines for forecasting geomagnetic disturbances have been developed based on evidence of a significant restructuring of the implied coronal magnetic field which could release solar wind plasma favorably positioned to impact the earth.

  16. Macroscopic anisotropy in AA5019A sheets

    SciTech Connect

    Choi, S.H.; Brem, J.C.; Barlat, F.; Oh, K.H.

    2000-05-11

    The macroscopic anisotropy for typical texture components in aluminum alloys and AA5019A sheet samples (H48 and O temper conditions) were investigated. In order to simultaneously consider the effects of morphological texture and crystallographic texture on macroscopic anisotropy, predictions of plastic properties were carried out using a full-constraints Taylor model and a visco-plastic self-consistent (VPSC) polycrystal model. The yield stress and r-value (width-to-thickness plastic strain ratio in uniaxial tension) anisotropy predicted using the VPSC model were in good agreement with experimental data.

  17. Variations of solar, interplanetary, and geomagnetic parameters with solar magnetic multipole fields during Solar Cycles 21-24

    NASA Astrophysics Data System (ADS)

    Kim, Bogyeong; Lee, Jeongwoo; Yi, Yu; Oh, Suyeon

    2015-01-01

    In this study we compare the temporal variations of the solar, interplanetary, and geomagnetic (SIG) parameters with that of open solar magnetic flux from 1976 to 2012 (from Solar Cycle 21 to the early phase of Cycle 24) for a purpose of identifying their possible relationships. By the open flux, we mean the average magnetic field over the source surface (2.5 solar radii) times the source area as defined by the potential field source surface (PFSS) model of the Wilcox Solar Observatory (WSO). In our result, most SIG parameters except the solar wind dynamic pressure show rather poor correlations with the open solar magnetic field. Good correlations are recovered when the contributions from individual multipole components are counted separately. As expected, solar activity indices such as sunspot number, total solar irradiance, 10.7 cm radio flux, and solar flare occurrence are highly correlated with the flux of magnetic quadrupole component. The dynamic pressure of solar wind is strongly correlated with the dipole flux, which is in anti-phase with Solar Cycle (SC). The geomagnetic activity represented by the Ap index is correlated with higher order multipole components, which show relatively a slow time variation with SC. We also found that the unusually low geomagnetic activity during SC 23 is accompanied by the weak open solar fields compared with those in other SCs. It is argued that such dependences of the SIG parameters on the individual multipole components of the open solar magnetic flux may clarify why some SIG parameters vary in phase with SC and others show seemingly delayed responses to SC variation.

  18. Cosmic Ray Monitoring and Space Dangerous Phenomena, 2. Methods of Cosmic Ray Using For Forecasting of Major Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Belov, A. V.; Dorman, L. I.; Eroshenko, E. A.; Iucci, N.; Mavromichalaki, H.; Pustil'Nik, L. A.; Sternlieb, A.; Villoresi, G.; Yanke, V. G.; Zukerman, I. G.

    We present developing of methods (e.g., Dorman et al., 1995, 1999) for forecasting on the basis of neutron monitor hourly on-line data (as well as on-line muon tele- scopes hourly data from different directions) geomagnetic storms of scales G5 (3- hour index of geomagnetic activity Kp=9), G4 (Kp=8) and G3 (Kp=7) (according to NOAA Space Weather Scales). These geomagnetic storms are dangerous for peo- ple technology and health (influence on power systems, on spacecraft operations, on HF radio-communications and others). We show that for especially dangerous geo- magnetic storms can be used global-spectrographic method if on-line will be avail- able 35-40 NM and muon telescopes. In this case for each hour can be determined CR anisotropy vector, and the specifically behavior of this vector before SC of ge- omagnetic storms G5, G4 or G3 (according to NOAA Space Weather Scales) can be used as important factor for forecast. The second factor what can be used for SC forecast is specifically behavior of CR density (CR intensity) for about 30-15 hours before SC (caused mainly by galactic CR particles acceleration during interaction with shock wave moved from the Sun). The third factor is effect of cosmic ray pre- decreasing, caused by magnetic connection of the Earth with the region behind the shock wave. We demonstrate developing methods on several examples of major ge- omagnetic storms. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting fea- tures for big Forbush-decreases". Nuclear Physics B, Vol. 49A, pp. 136-144. (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their prediction", Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, Vol. 6, p. 476-479, (1999).

  19. An investigation of ionospheric F region response in the Brazilian sector to the super geomagnetic storm of May 2005

    NASA Astrophysics Data System (ADS)

    de Abreu, A. J.; Sahai, Y.; Fagundes, P. R.; de Jesus, R.; Bittencourt, J. A.; Pillat, V. G.

    2011-10-01

    In this paper, we have investigated the responses of the ionospheric F region at equatorial and low latitude regions in the Brazilian sector during the super geomagnetic storm on 15-16 May 2005. The geomagnetic storm reached a minimum Dst of -263 nT at 0900 UT on 15 May. In this paper, we present vertical total electron content (vTEC) and phase fluctuations (in TECU/min) from Global Positioning System (GPS) observations obtained at Belm, Braslia, Presidente Prudente, and Porto Alegre, Brazil, during the period 14-17 May 2005. Also, we present ionospheric parameters h'F, hpF2, and foF2, using the Canadian Advanced Digital Ionosonde (CADI) obtained at Palmas and So Jos dos Campos, Brazil, for the same period. The super geomagnetic storm has fast decrease in the Dst index soon after SSC at 0239 UT on 15 May. It is a good possibility of prompt penetration of electric field of magnetospheric origin resulting in uplifting of the F region. The vTEC observations show a trough at BELE and a crest above UEPP, soon after SSC, indicating strengthening of nighttime equatorial anomaly. During the daytime on 15 and 16 May, in the recovery phase, the variations in foF2 at SJC and the vTEC observations, particularly at BRAZ, UEPP, and POAL, show large positive ionospheric storm. There is ESF on the all nights at PAL, in the post-midnight (UT) sector, and phase fluctuations only on the night of 14-15 May at BRAZ, after the SSC. No phase fluctuations are observed at the equatorial station BELE and low latitude stations (BRAZ, UEPP, and POAL) at all other times. This indicates that the plasma bubbles are generated and confined on this magnetically disturbed night only up to the low magnetic latitude and drifted possibly to west.

  20. The geomagnetic field - An explanation for the microturbulence in coaxial gun plasmas

    NASA Technical Reports Server (NTRS)

    Mather, J. W.; Ahluwalia, H. S.

    1988-01-01

    The complexity introduced by the geomagnetic field in several regions of a coaxial gun plasma device is described. It is shown that the annihilation of the swept-up geomagnetic flux, trapped within the highly compressed turbulent plasma, provides an explanation for varied performance and experimental results. The results indicate that the device should be aligned along the direction of the local geomagnetic field or enclosed in a mu-metal shield.

  1. Analysis of the 3-7 October 2000 and 15-24 April 2002 geomagnetic storms with an optimized nonlinear dynamical model

    NASA Astrophysics Data System (ADS)

    Horton, W.; Spencer, E.; Mays, L.; Doxas, I.; Kozyra, J.

    A computationally optimized low dimensional nonlinear dynamical model of the magnetosphere-ionosphere system called WINDMI is used to analyze two large geomagnetic storm events 3-7 October 2000 and 15-24 April 2002 These two important storms share common features such as the passage of magnetic clouds shock events from coronal mass ejections triggered substorms and intervals of sawtooth oscillations Sawtooth oscillations resemble periodic substorms but occur in association with strong or building ring current populations and have injection regions that are unusually close to Earth and unusually wide in magnetic local times The April 2002 event includes one of the best examples of sawtooth events ever observed On 18 April 2002 sawtooth oscillations were clearly visible when solar wind conditions IMF Bz density pressure were relatively steady with a slowly varying Dst In this study WINDMI is used to model the 3-7 October 2000 and 15-24 April 2002 geomagnetic activity WINDMI results are evaluated focusing on the sawtooth intervals and the overall prediction of the westward auroral electrojet AL index and Dst index The input to the model is the dynamo driving voltage derived from the fluctuating solar wind plasma and the interplanetary magnetic field measured by the ACE satellite The output of the model is a field aligned current proportional to the AL index and the energy stored in the ring current which is proportional to the Dst index The model parameters are optimized using a genetic algorithm GA to obtain solutions that simultaneously have least mean

  2. The un-uniform observatories location effect in the Dst index

    NASA Astrophysics Data System (ADS)

    Wu, Y.

    2012-12-01

    The Dst index is a major planetary magnetic activity index proposed by Sugiura in 1964, which is designed to depict the temporal development of the magnetic storm and the intensity of the ring current system flowing in the equatorial plane of the magnetosphere at 3 to 8 Earth radii. It is an hourly index derived from the average value of the horizontal component of the geomagnetic field at four low latitudinal observatories (namely, HER, HON, KAK and SJG). For a long time, the Dst index is greatly doubted. Researchers have pointed out that a great proportion of the Dst index is originated from the Substorm Wedge current system, the Cross-tail current and the Partial ring current system [Turner et al., 2000; Liemohn et al., 2001; Ohtani et al., 2001; Rostoker, 2000; Friedrich et al., 1999; Maltsev, 2003; Huang, 2004; Hakkinen et al., 2002]. The ring current system and its disturbed storm-time field (Dst field) take on an enhanced dawn-dusk asymmetry during disturbed time. Therefore, the influence of the non-uniform location of four observatories of the Dst index will enhance. The purpose of this paper is to study the influence of the observatories' location on the Dst index. The hourly data of the horizontal component of the geomagnetic field in the observatories in geomagnetic latitude between 45S and -45N is used, to derive the local-time distribution model of the Dst field by the method of Nature Orthogonal Component and Cubic Polynomial Fitting. Results suggest that the maximum difference to the LT-model with four Dst index stations is about 5% lowness on 16UTmp, 3% highness on 05UTmp, and the minimum difference is around 11UTmp (UTmp corresponds to the universal time of the minimum of the Dst index). It proves some certain extent efficiency afforded by adding observatories in the SYM index.

  3. Study on Fabrication of AA4032/AA6069 Cladding Billet Using Direct Chill Casting Process

    NASA Astrophysics Data System (ADS)

    Han, Xing; Zhang, Haitao; Shao, Bo; Li, Lei; Liu, Xuan; Cui, Jianzhong

    2016-03-01

    AA4032/AA6069 cladding billet in size of φ130 mm/φ110 mm was prepared by the modified direct chill casting process, and the parametric effect on casting performance was investigated using numerical simulation. Microstructures, elements distribution, and mechanical properties of the bonding interface were examined. The results show that metallurgical bonding interface can be obtained with the optimal parameters: the casting speed of 130 to 140 mm/min, the internal liquid level height of 50 to 60 mm, and the contact height of 40 to 50 mm. The metallurgical bonding interface is free of any discontinuities due to the fact that the alloying elements diffused across the interface and formed Ni-containing phase. Tensile strength of the cladding billet reaches 225.3 MPa, and the fracture position was located in AA6069 side, suggesting that the interface bonding strength is higher than the strength of AA6069. The interfacial shearing strength is 159.3 MPa, indicating excellent metallurgical bonding.

  4. A database of synthetic observations for geomagnetic data assimilation practice

    NASA Astrophysics Data System (ADS)

    Fournier, A.; Aubert, J.; Thebault, E.; Schaeffer, N.

    2012-04-01

    Data assimilation aims at producing an optimal estimate of the state of the dynamical system one is interested in by combining two sources of information : physical laws (in the form of a numerical model) and observations. A mandatory step during the development of a data assimilation framework involves a validation phase using synthetic data. In this well-controlled environment, the true dynamical trajectory of the system is known (it results from the integration of the numerical model), and it is used to generate synthetic observations. Those are subsequently used to assess the efficacy, and to highlight possible shortcomings, of the chosen methodology. Data assimilation has recently come to the fore in geomagnetism (e.g. Fournier et al., 2010), a surge motivated by our increased ability to observe the geomagnetic field (thanks to dedicated satellite missions), and by the concurrent progress in the numerical description of core dynamics. Open questions are related to the type of physical models one should resort to, and to the choice of a suitable algorithm, able to integrate the highly heterogeneous geomagnetic record at our disposal, and to deal with the non-linearities of the problem at hand (e.g. Aubert & Fournier, 2011; Fournier et al., 2011). Here we report on the construction of a database of synthetic observations meant at reproducing the heterogeneity of the geomagnetic record (in terms of temporal and spatial coverage). This database relies on two dynamical trajectories: a long-term dynamical trajectory (spanning the equivalent of the past few millenia) computed from a three-dimensional, convection-driven, dynamo model, able to represent accurately the long-term variability of the geomagnetic field a short-term dynamical trajectory (spanning the equivalent of a few decades), computed from a high-resolution three-dimensional model, able to represent interannual to decadal core processes (e.g. Gillet et al., 2011), and whose basic state is determined from the long-term trajectory. These two trajectories are used to generate synthetic observations representative of the current archeomagnetic, historical, observatory and satellite catalogs. For each catalog, we add realistic contributions from other sources (crust, external fields) and noise to the observations, with levels and properties expected for each. We also complement the archeomagnetic, historical and observatory catalog with a corresponding perfect catalog (in terms of the uniformity of the coverage), and with a catalog containing the Gauss coefficients describing the magnetic field at the surface of the Earth (with an arbitrary level of truncation).

  5. On multifractality of high-latitude geomagnetic fluctuations

    NASA Astrophysics Data System (ADS)

    Vrs, Z.

    2000-10-01

    In order to contribute to the understanding of solar wind-magnetosphere interactions the multifractal scaling properties of high-latitude geomagnetic fluctuations observed at the Thule observatory have been studied. Using the local observatory data and the present experimental knowledge only it seems hard to characterize directly the, presumably intermittent, mesoscale energy accumulation and dissipation processes taking place at the magnetotail, auroral region, etc. Instead a positive probability measure, describing the accumulated local geomagnetic signal energy content at the given time scales has been introduced and its scaling properties have been studied. There is evidence for the multifractal nature of the so defined intermittent field , a result obtained by using the recently introduced technique of large deviation multifractal spectra. This technique allows us to describe the geomagnetic fluctuations locally in time by means of singularity exponents , which represent a generalization of the local degree of differentiability and characterize the power-law scaling dependence of the introduced measure on resolution. A global description of the geomagnetic fluctuations is insured by the spectrum of exponents f() which represents a rate function quantifying the deviations of the observed singularities from the expected value. The results show that there exists a multifractal counterpart of the previously reported spectral break and different types of f() spectra describe the fluctuations in direct dissipation or loading-unloading regimes of the solar wind-magnetosphere interaction. On the time scale of substorms and storms the multi-fractal structure of the loading-unloading mode fluctuations seems to be analogous to the simple multiplicative P-model, while the f() spectra in direct dissipation regime are close but not equal to the features of a uniform distribution. Larger deviations from the multiplicative model are observed when the influence of the solar wind fluctuations is examined. On this basis it is expected that an extended multifractal analysis of the singularity structure of near-Earth plasma system fluctuations would lead to improved geomagnetic diagnosis of the magnetospheric dynamics.

  6. The Development of a Dynamic Geomagnetic Cutoff Rigidity Model for the International Space Station

    NASA Technical Reports Server (NTRS)

    Smart, D. F.; Shea, M. A.

    1999-01-01

    We have developed a computer model of geomagnetic vertical cutoffs applicable to the orbit of the International Space Station. This model accounts for the change in geomagnetic cutoff rigidity as a function of geomagnetic activity level. This model was delivered to NASA Johnson Space Center in July 1999 and tested on the Space Radiation Analysis Group DEC-Alpha computer system to ensure that it will properly interface with other software currently used at NASA JSC. The software was designed for ease of being upgraded as other improved models of geomagnetic cutoff as a function of magnetic activity are developed.

  7. Effects of magnetic fields produced by simulated and real geomagnetic storms on rats

    NASA Astrophysics Data System (ADS)

    Martínez-Bretón, J. L.; Mendoza, B.

    2016-03-01

    In this paper we report experiments of arterial pressure (AP) measurements of ten Wistar rats subjected to geomagnetic field changes and to artificially stimulated magnetic field variations. Environmental electromagnetic effects were screened using a semianechoic chamber, which allowed us to discern the effects associated with geomagnetic storms. We stimulated the subjects with a linear magnetic profile constructed from the average changes of sudden storm commencement (SSC) and principal phases of geomagnetic storms measured between 1996 and 2008 with Dst ⩽ -100 nT. Although we found no statistically significant AP variations, statistically significant AP changes were found when a geomagnetic storm occurred during the experimental period. Using the observed geomagnetic storm variations to construct a geomagnetic profile to stimulate the rats, we found that the geomagnetic field variations associated to the SSC day were capable of increasing the subjects AP between 7% and 9% from the reference value. Under this magnetic variation, the subjects presented a notably restless behavior not seen under other conditions. We conclude that even very small changes in the geomagnetic field associated with a geomagnetic storm can produce a measurable and reproducible physiological response.

  8. Toward more reliable long-term indices of geomagnetic activity: Correcting a new inhomogeneity problem in early geomagnetic data

    NASA Astrophysics Data System (ADS)

    Holappa, L.; Mursula, K.

    2015-10-01

    For the time before the space era, our knowledge of the centennial evolution of solar wind (SW) and interplanetary magnetic field (IMF) is based on proxies derived from geomagnetic indices. The reliability of these proxies is dependent on the homogeneity of magnetic field data. In this paper, we study the interhourly (IHV) and interdiurnal (IDV1d) variability indices calculated from the data of two British observatories, Eskdalemuir and Lerwick, and compare them to the corresponding indices of the German Niemegk observatory. We find an excess of about 14 4% (5.8 2%) and 27 10% (15 6%) in the IHV (IDV1d) in the indices of Eskdalemuir and Lerwick in 1935-1969. The timing of this excess accurately coincides with instrument changes made in these observatories, strongly supporting the interpretation that the excess is indeed caused by instrument related inhomogeneities in the data of Eskdalemuir and Lerwick. We show that the detected excess notably modifies the long-term trend of geomagnetic activity and the centennial evolution of IMF strength and solar wind speed estimated using these indices. We note that the detected inhomogeneity problem may not be limited to the data of the two studied observatories but may be quite common to long series of geomagnetic measurements. These results question the reliability of the present measures of the centennial change in solar wind speed and IMF.

  9. Histological study of experimental murine AA amyloidosis.

    PubMed

    Kuroiwa, Mie; Aoki, Kimiko; Izumiyama, Naotaka

    2003-01-01

    The localization of amyloid fibril components and the cells related to the formation and resorption of the fibrils are still controversial. We conducted a time-kinetic study to analyse the process of amyloid fibril deposition in the spleen of an AA amyloidosis animal model immunohistochemically. Murine AA amyloidosis was induced by an emulsion injection composed of Freund's complete adjuvant and Mycobacterium butyricum. The serum amyloid A level was the highest at 3 days after the induction and gradually decreased. The amyloid deposition was first detected in extracellular spaces in the marginal zone of the spleen at 7 days after induction. F4/80 positive red pulp macrophages increased in number after the induction and accumulated near the amyloid deposition areas. Amyloid P component (APC) and chondroitin sulphate proteoglycan (CSPG), which are composed of amyloid fibril, were detected in the cytoplasm of F4/80 positive red pulp macrophages and ER-TR9 positive marginal zone macrophages, respectively, then localized in the amyloid deposition areas. APC was also localized in CSPG positive and F4/80 negative cells, which might be fibroblasts at 3 days. These results suggest a close association of APC positive/ER-TR9 positive macrophages and APC positive/CSPG positive fibroblasts in the formation of amyloid fibrils and F4/80 positive macrophages with the resorption of fibrils. PMID:14599103

  10. Marine Magnetic Anomalies, Oceanic Crust Magnetization, and Geomagnetic Time Variations

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Arkani-Hamed, J.

    2005-12-01

    Since the classic paper of Vine and Matthews (Nature, 1963), marine magnetic anomalies are commonly used to date the ocean floor through comparison with the geomagnetic polarity time scale and proper identification of reversal sequences. As a consequence, the classical model of rectangular prisms bearing a normal / reversed magnetization has been dominant in the literature for more than 40 years. Although the model explains major characteristics of the sea-surface magnetic anomalies, it is contradicted by (1) recent advances on the geophysical and petrologic structure of the slow-spreading oceanic crust, and (2) the observation of short-term geomagnetic time variations, both of which are more complex than assumed in the classical model. Marine magnetic anomalies may also provide information on the magnetization of the oceanic crust as well as short-term temporal fluctuations of the geomagnetic field. The "anomalous skewness", a residual phase once the anomalies have been reduced to the pole, has been interpreted either in terms of geomagnetic field variations or crustal structure. The spreading-rate dependence of anomalous skewness rules out the geomagnetic hypothesis and supports a spreading-rate dependent magnetic structure of the oceanic crust, with a basaltic layer accounting for most of the anomalies at fast spreading rates and an increasing contribution of the deeper layers with decreasing spreading rate. The slow cooling of the lower crust and uppermost mantle and serpentinization, a low temperature alteration process which produces magnetite, are the likely cause of this contribution, also required to account for satellite magnetic anomalies over oceanic areas. Moreover, the "hook shape" of some sea-surface anomalies favors a time lag in the magnetization acquisition processes between upper and lower magnetic layers: extrusive basalt acquires a thermoremanent magnetization as soon as emplaced, whereas the underlying peridotite and olivine gabbro cool slowly and pass through serpentinization to bear a significant magnetization. Our analysis of the amplitude of Anomaly 25 shows a sharp threshold at the spreading rate of 30 km/Ma, which corresponds to the transition between oceanic lithosphere built at axial domes and axial valleys. The twice lower amplitudes are in agreement with a much disrupted and altered basaltic layer at slow rates and a significant contribution from the deeper layers. Oceanic lithosphere created at fast and slow spreading rates therefore exhibits contrasted magnetic structures. High resolution magnetic anomaly measurements carried out with deep tows and submersibles show that the magmatic (fast spreading and parts of the slow spreading) crust is a good recorder of short-term geomagnetic time variations, such as short polarity intervals, excursions, or paleointensity variations. Surface and deep-sea magnetic anomalies therefore help to confirm or infirm geomagnetic findings obtained by other means. Many excursions and paleointensity variations within Brunhes and Matuyama periods are confirmed, but the "saw tooth pattern" inferred from sediment cores - a possible candidate to explain the anomalous skewness - is not, which suggests a bias in the sedimentary approach.

  11. Activity of vegetative insecticidal proteins Vip3Aa58 and Vip3Aa59 of Bacillus thuringiensis against lepidopteran pests.

    PubMed

    Baranek, Jakub; Kaznowski, Adam; Konecka, Edyta; Naimov, Samir

    2015-09-01

    Vegetative insecticidal proteins (Vips) secreted by some isolates of Bacillus thuringiensis show activity against insects and are regarded as insecticides against pests. A number of B. thuringiensis strains harbouring vip3A genes were isolated from different sources and identified by using a PCR based approach. The isolates with the highest insecticidal activity were indicated in screening tests, and their vip genes were cloned and sequenced. The analysis revealed two polymorphic Vip protein forms, which were classified as Vip3Aa58 and Vip3Aa59. After expression of the vip genes, the proteins were isolated and characterized. The activity of both toxins was estimated against economically important lepidopteran pests of woodlands (Dendrolimus pini), orchards (Cydia pomonella) and field crops (Spodoptera exigua). Vip3Aa58 and Vip3Aa59 were highly toxic and their potency surpassed those of many Cry proteins used in commercial bioinsecticides. Vip3Aa59 revealed similar larvicidal activity as Vip3Aa58 against S. exigua and C. pomonella. Despite 98% similarity of amino acid sequences of both proteins, Vip3Aa59 was significantly more active against D. pini. Additionally the effect of proteolytic activation of Vip58Aa and Vip3Aa59 on toxicity of D. pini and S. exigua was studied. Both Vip3Aa proteins did not show any activity against Tenebrio molitor (Coleoptera) larvae. The results suggest that the Vip3Aa58 and Vip3Aa59 toxins might be useful for controlling populations of insect pests of crops and forests. PMID:26146224

  12. Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies

    NASA Technical Reports Server (NTRS)

    Killeen, T. L.; Won, Y.-I.; Niciejewski, R. J.; Burns, A. G.

    1995-01-01

    Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The central polar cap (greater than approx. 80 magnetic latitude) antisunward wind speed is found to be a strong function of both solar and geomagnetic activity. The polar cap temperatures show variations in both solar and geomagnetic activity, with temperatures near 800 K for low K(sub p) and F(sub 10.7) and greater than about 2000 K for high K(sub p) and F(sub 10.7). The observed temperatures are significantly greater than those predicted by the mass spectrometer/incoherent scatter model for high activity conditions. Theoretical analysis based on the NCAR TIGCM indicates that the antisunward upper thermospheric winds, driven by upstream ion drag, basically 'coast' across the polar cap. The relatively small changes in wind velocity and direction within the polar cap are induced by a combination of forcing terms of commensurate magnitude, including the nonlinear advection term, the Coriolis term, and the pressure gradient force term. The polar cap thennospheric thermal balance is dominated by horizontal advection, and adiabatic and thermal conduction terms.

  13. Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Tsurutani, B. T.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Runge, T.

    2013-02-01

    We study solar wind-ionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23) - 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs). The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA) events. The JPL Global Ionospheric Map (GIM) software and the GPS total electron content (TEC) database were used to calculate the vertical TEC (VTEC) and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU) near local noon (12:00 to 14:00 LT) in 2008. In 2009 during the minimum geomagnetic activity (MGA) interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10-22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU). The ionospheric VTEC changes during 2008-2009 were similar but ~60% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed. We use the infrared NO and CO2 emission data obtained with SABER on TIMED as a proxy for the radiation balance of the thermosphere. It is shown that infrared emissions increase during HSS events possibly due to increased energy input into the auroral region associated with HILDCAAs. The 2008-2009 HSS intervals were ~85% less intense than the 2003 early declining phase event, with annual averages of daily infrared NO emission power of ~ 3.3 1010 W and 2.7 1010 W in 2008 and 2009, respectively. The roles of disturbance dynamos caused by high-latitude winds (due to particle precipitation and Joule heating in the auroral zones) and of prompt penetrating electric fields (PPEFs) in the solar wind-ionosphere coupling during these intervals are discussed. A correlation between geoeffective interplanetary electric field components and HSS intervals is shown. Both PPEF and disturbance dynamo mechanisms could play important roles in solar wind-ionosphere coupling during prolonged (up to days) external driving within HILDCAA intervals.

  14. MoSST DAS: The First Working Geomagnetic Data Assimilation System

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

    The Earth possesses an internal magnetic field (geomagnetic field) generated by convection in the outer core (geodynamo). Previous efforts have been focused along two distinct paths: (1) numerical geodynamo modeling to understand the origin of the geomagnetic field, and the mechanisms of geomagnetic secular variations (SV); and (2) geomagnetic field modeling to map the spatial/temporal variations of the field from geomagnetic data, and to derive core properties, e.g. inversion of core flow near the core-mantle boundary (CMB). Geomagnetic data assimilation is a new approach emerged over the past 5 years: surface observations are assimilated with geodynamo models for better understanding of the core dynamical state, and accurately prediction of SV. In collaboration with several geomagnetic research groups, we have developed the first working geomagnetic data assimilation system, Modular, Scalable, Self-consistent, and Three-dimensional (MoSST) DAS, that includes the MoSST numerical dynamo model; 7000 years of geomagnetic field maps from several field models utilizing satellite and ground observatory data, historical magnetic recor