Sample records for aa geomagnetic index

  1. Maximum Entropy Spectral Analysis of the Geomagnetic Activity Index aa Over a 107Year Interval

    Microsoft Academic Search

    V. Courtillot; J. L. Le Mouël; P. N. Mayaud

    1977-01-01

    Maximum entropy spectral analysis (Mesa) of a time series consisting of 107 annual mean values of the geomagnetic activity index aa and analysis of subsets of this time series yield interesting results concerning both the maximum entropy method itself and periodicities in geo- magnetic activity. The influence of removing a trend from the original data is found to have an

  2. IHV: a new long-term geomagnetic index

    NASA Astrophysics Data System (ADS)

    Svalgaard, Leif; Cliver, Edward W.; Le Sager, Philippe

    2004-01-01

    We derive a new daily index of geomagnetic activity, the Inter-Hour Variability index (IHV), for investigations of the long-term variability of the solar wind-magnetosphere system. The IHV index is used to successfully reconstruct yearly-averages of the range indices am, ap, and aa from 1959 through 2000. When we attempt to reconstruct the aa index back to 1901, however, the reconstructed aa lies above the observed aa for years before 1957, with the difference between the two curves being the greatest (˜5-10 nT) during the first two decades of the 20th century.

  3. New Geomagnetic Index (idv) Measuring Magnitude of Interplanetary Magnetic Field

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.; Cliver, E. W.

    2003-12-01

    We present a new long-term geomagnetic index (the IDV index) which has the property that it is a proxy of the magnitude of the interplanetary magnetic field at the Earth. The index is constructed (for any given station) as the monthly (or yearly) average of the differences (taken without regard to sign) of the hourly mean values of the hour following local midnight between two consecutive days. It is similar to the classical u-measure except that the differences are between one-hour values rather than daily means. The IDV index has a strong correlation (r=0.88) with the magnitude, B, of the IMF, but is uncorrelated (r=0.09) with the solar wind speed, V. Because other indices (e.g. aa and our own IHV) are strongly correlated with BV**2, the IDV index fords a way of separating the influence of B and V and thus determining both.

  4. Kp-index and real geomagnetic activity based on the magnetospheric energy budget model

    Microsoft Academic Search

    L. Gromova; L. Dremukhina; A. Levitin; V. Popov

    2003-01-01

    Geomagnetic activity becomes apparent in different way in the various Earth's areas. Therefore it is difficult to find quantitative description of the real geomagnetic activity characterizing the magnetic field total situation throughout the Earth surface. Usually planetary Kp-index of the geomagnetic activity is used to analyze daily geomagnetic disturbances. Kp-index yearly variations determine the geomagnetic activity seasonal variations. The well-known

  5. Interhourly variability index of geomagnetic activity and its use in deriving the long-term variation of solar wind speed

    NASA Astrophysics Data System (ADS)

    Svalgaard, Leif; Cliver, Edward W.

    2007-10-01

    We describe the detailed derivation of the interhourly variability (IHV) index of geomagnetic activity. The IHV index for a given geomagnetic element is mechanically derived from hourly values or means as the sum of the unsigned differences between adjacent hours over a 7-hour interval centered on local midnight. The index is derived separately for stations in both hemispheres within six longitude sectors spanning the Earth using only local night hours. It is intended as a long-term index and available data allows derivation of the index back well into the 19th century. On a timescale of a 27-day Bartels rotation, IHV averages for stations with corrected geomagnetic latitude less than 55° are strongly correlated with midlatitude range indices (R2 = 0.96 for the am index since 1959; R2 = 0.95 for the aa index since 1980). We find that observed yearly averages of aa before the year 1957 are ˜3 nT too small compared to values calculated from IHV using the regression constants based on 1980-2004. We interpret this discrepancy as an indication that the calibration of the aa index is in error before 1957. There is no systematic discrepancy between observed and similarly calculated ap values back to 1932. Bartels rotation averages of IHV are also strongly correlated with solar wind parameters (R2 = 0.79 with BV2). On a timescale of a year combining the IHV index (giving BV2 with R2 = 0.93) and the recently developed interdiurnal variability (IDV) index (giving interplanetary magnetic field magnitude, B, with R2 = 0.74) allows determination of solar wind speed, V, from 1890 to present. Over the ˜120-year series, the yearly mean solar wind speed varied from a low (inferred) of 303 km/s in 1902 to a high (observed) value of 545 km/s in 2003. The calculated yearly values of the product BV using B and V separately derived from IDV and IHV agree quantitatively with (completely independent) BV values derived from the amplitude of the diurnal variation of the horizontal component in the polar caps since 1926 (and sporadically further back).

  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. 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.

  8. 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.

  9. INTERPRETATION OF Kp INDEX AND M-REGION GEOMAGNETIC STORMS

    Microsoft Academic Search

    A. J. Dessler; Fejer J. A

    1963-01-01

    It is argued that the traditional interpretation of the K\\/sub p\\/ index ; is no longer tenabie. The K\\/sub p\\/ index, generally taken to be a measure of the ; strength of the solar-wind flux, may be more acceptably interpreted as a measure ; of the time rate of change of the sum of plasma plus magnetic pressure acting on

  10. 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 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.

  11. Occurrence of AE and Dst Geomagnetic Index Levels and the Selection of the Quietest Days in a Year

    Microsoft Academic Search

    Wallace H. Campbell

    1979-01-01

    Three groups of indices were studied as indicators for quiet day geomagnetic field level determinations: one was the AE index, and the other two were the positive and negative value groups of the Dst index. A comparison of the behaviors of these three indices for 17 years showed their solar cycle changes and the differences in distribution of index levels

  12. 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.

  13. 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.

  14. 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.

  15. Correlation Between Particle Injections Observed at Geosynchronous Orbit and the Dst Index During Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Moon, G.; Ahn, B.; Kamide, Y.; Reeves, G. D.

    2004-12-01

    To understand the relationship between geomagnetic storms and substorms, we examine the correlation between dispersionless proton injections observed by geosynchronous satellites and the Dst index during geomagnetic storms. We utilize geomagnetic storms occurred during the period of 1997-2002, categorizing them into four classes according to the minimum Dst value, Dstmin; Severe (Dstmin < -200 nT), intense (-200 nT ? Dstmin <-100 nT), moderate (-100 nT ? Dstmin <-50 nT), and weak (-50 nT ? Dstmin <-30 nT) storms. We use the proton flux with the energy range from 50 keV to 670 keV observed by the LANL geosynchronous satellites located in the dark hemisphere from 1800 LT to 0600 LT. It is not possible to deduce the amount of the total energy injection into the inner magnetosphere from measurements only by one or two satellites. Nonetheless, we may obtain a quantity that is proportional to the true injection rate during magnetic storms by estimating the flux increase expressed in terms of the flux ratio (fmax/fpre\\ave) and the number of injections, where fpre\\ave and fmax represent the average flux of pre-storm level and onset level, respectively. Thus, we propose to introduce a parameter, ør¡Ætotal energy injection parameter (TEIP)ør¡_, defined by the product of the flux ratio and the number of injections, as an indicator of the energy injected into the inner magnetosphere. To determine the phase dependence of the substorm contribution to the development of geomagnetic storm, we examine this quantity for the main and recovery phases separately. Several interesting points are noted particularly for the main phase of storms. First, the number of particle injections tends to increase with the storm size. Second, the flux ratio (fmax/fpre\\ave) also tends to increase with the storm size. The correlation coefficient between Dstmin and the flux ratio is high, for example, 0.84 for the 50 ˜75 keV energy channel. Third, there is also a significantly high correlation between TEIP and Dstmin. Particularly, the correlation coefficients are very high, above 0.85, for those channels of energy, 50 ˜400 keV, which represent the typical energy range of ring current particles. These results indicate that the substorm expansion activity is higher during the main phase than the recovery phase, suggesting that the substorm expansion activity seems to be closely associated with the development of magnetic storms. Fourth, particle injections during the recovery phase of a storm tend to make the storm last longer. This tendency is particularly prominent for more intense storms.

  16. Correlation between particle injections observed at geosynchronous orbit and the Dst index during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Moon, Ga-Hee; Ahn, B.-H.; Kamide, Y.; Reeves, G. D.

    2004-10-01

    To understand the relationship between geomagnetic storms and substorms, we examine the correlation between dispersionless proton injections observed by geosynchronous satellites and the Dst index during geomagnetic storms. It is not possible to deduce the amount of the total energy injection into the inner magnetosphere from measurements only by one or two satellites. Nonetheless, we may obtain a quantity that is proportional to the true injection rate during magnetic storms by estimating the flux increase expressed in terms of the flux ratio (fmax/fpre_ave) and the number of injections, where fpre_ave and fmax represent the average flux of prestorm level and onset level, respectively. Thus we propose to introduce a parameter, "total energy injection parameter" (TEIP), defined by the product of the flux ratio and the number of injections, as an indicator of the energy injected into the inner magnetosphere. Several interesting points are noted, particularly for the main phase of storms. First, the number of particle injections tends to increase with the storm size. Second, the flux ratio (fmax/fpre_ave) also tends to increase with the storm size. Third, there is also a significantly high correlation between TEIP and Dstmin. In particular, the correlation coefficients are very high, above 0.85, for those channels of energy, 50-400 keV, which represent the typical energy range of ring current particles. These results indicate that the substorm expansion activity is higher during the main phase than the recovery phase, suggesting that the substorm expansion activity seems to be closely associated with the development of magnetic storms.

  17. The Relationship Between Particle Injection Rate Observed at Geosynchronous Orbit and Dst Index during Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Moon, Ga-Hee; Ahn, Byung-Ho

    2003-06-01

    To examine the causal relationship between geomagnetic storm and substorm, we investigate the correlation between dispersionless particle injection rate of proton flux observed from geosynchronous satellites, which is known to be a typical indicator of the substorm expansion activity, and Dst index during magnetic storms. We utilize geomagnetic storms occurred during the period of 1996˜2000 and categorize them into three classes in terms of the minimum value of the Dst index (Dstmin); intense (--200 nT ? Dstmin? -100 nT), moderate (--100 nT ? Dstmin? -50 nT), and small (--50 nT ? Dstmin? -30 nT) storms. We use the proton flux of the energy range from 50 keV to 670 keV, the major constituents of the ring current particles, observed from the LANL geosynchronous satellites located within the local time sector from 18:00 MLT to 04:00 MLT. We also examine the flux ratio (fmax/fave) to estimate particle energy injection rate into the inner magnetosphere, with fave and fmax being the flux levels during quiet and onset levels, respectively. The total energy injection rate into the inner magnetosphere can not be estimated from particle measurements by one or two satellites. However, the total energy injection rate should be at least proportional to the flux ratio and the injection frequency. Thus we propose a quantity, ``total energy injection parameter (TEIP)", defined by the product of the flux ratio and the injection frequency as an indicator of the injected energy into the inner magnetosphere. To investigate the phase dependence of the substorm contribution to the development of magnetic storm, we examine the correlations during the two intervals, main and recovery phase of storm separately. Several interesting tendencies are noted particularly during the main phase of storm. First, the average particle injection frequency tends to increase with the storm size with the correlation coefficient being 0.83. Second, the flux ratio (fmax/fave) tends to be higher during large storms. The correlation coefficient between Dstmin and the flux ratio is generally high, for example, 0.74 for the 75˜113 keV energy channel. Third, it is also worth mentioning that there is a high correlation between the TEIP and Dstmin with the highest coefficient (0.80) being recorded for the energy channel of 75˜113 keV, the typical particle energies of the ring current belt. Fourth, the particle injection during the recovery phase tends to make the storms longer. It is particularly the case for intense storms. These characteristics observed during the main phase of the magnetic storm indicate that substorm expansion activity is closely associated with the development of mangetic storm.

  18. 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.

  19. Hemispheric asymmetry of the sun suggested by the annual variation of the aa index

    Microsoft Academic Search

    J. Oksman; E. Kataja

    1986-01-01

    The annual variation of Mayaud's (1973) aa index has been discovered to exhibit unequal spring and fall maxima, the relative dominance of the two equinoxes varying in a quasi-periodic way. This finding suggests that one magnetic hemisphere of the sun might predominate slightly over the other for several years in succession, the dominance then switching over in a quasi-periodic way.

  20. Solar magnetic polarity dependency of geomagnetic storm seasonal occurrence

    NASA Astrophysics Data System (ADS)

    Oh, S. Y.; Yi, Y.

    2011-06-01

    For nearly a century it has been known that the tendency for geomagnetic activity is, on average, higher at the equinoxes than at the solstices. Previous studies on semiannual geomagnetic activity were performed mainly for geomagnetic indices such as am, aa, U, and AL. Thus, we need to understand the seasonal variation of geomagnetic activity defined by the Dst index over the long term. It is also necessary to test the solar magnetic polarity dependence of geomagnetic activity. This paper is a statistical analysis of the geomagnetic storms defined by the Dst index. Our storm data consists of two sets of storm data for 5 years at each solar minimum during the four solar cycles (19-22) from 1962 through 1998 for two of each solar magnetic polarity. The storms are divided into two groups defined by Dst index (Dst(min) < -50 nT, ?Dst? > 70 nT; Dst(min) < -50 nT, ?Dst? > 90 nT). Monthly occurrences of these storms are compared. Storms of ?Dst? > 90 nT and of ?Dst? > 70 nT occurred 153 and 238 times, respectively, during the testing periods. Storms occurred more frequently during the spring and fall seasons for all solar cycle minima, regardless of solar magnetic polarity.

  1. 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.

  2. Long-term geomagnetic activity: Recent problems, developments and consequences for space climate

    NASA Astrophysics Data System (ADS)

    Mursula, K.

    2008-05-01

    Geomagnetic activity forms one of the most reliable and versatile ways to study the long-term change in the Sun and heliosphere, i.e., space climate. Continuous measurements of geomagnetic activity exist since the mid-19th century, covering more than 160 years. In addition to the long-term trend, geomagnetic activity depicts persistent patterns and periodicities, the most dominant of which are the solar cycle variation and the semiannual variation. Other significant fluctuations include the annual variation, 1.3-1.8-year variation and the 22-year variation. All these variations reflect some fundamental properties of the Sun and the Sun-Earth connection. Interestingly, although some of these patterns are known for a long time (e.g., the semiannual variation for nearly 150 years), they are properly understood only since recently. The overall level of geomagnetic activity has increased during the last 100 years although the exact amount of increase is still under debate. Also, the estimates based on geomagnetic activity about the long-term change of various solar and heliospheric parameters, like the intensity of the heliospheric magnetic field, the solar wind speed and the total solar irradiance, vary considerably. These differences are caused by problems in the quality of archival data, by inhomogeneities and errors in geomagnetic indices and by the unsatisfactory level of understanding the relations between solar, heliospheric and geomagnetic parameters. E.g., it has been noted recently that errors in archival data may lead to seriously flawed estimates of the centennial trend. Also, it is known that the longest and most used long-term geomagnetic index, the aa index, is inhomogeneous and depicts an excessively large centennial increase. Accordingly, all estimates based on the aa index yield excessively large centennial changes and need to be corrected. Taking into account the crucial role of the Sun for, e.g., the global climate, the long-term change in solar activity has considerable social interest and should be evaluated as reliably as possible. Recently, new indices of long- term geomagnetic activity have been developed based on digitally available hourly values of the geomagnetic field. These indices allow for a detailed examination of their properties, being therefore more straightformward and more reliable than earlier indices. One group of these new indices follows the traditional definition of the 3- hourly K index method, another measures hourly variability in the night sector only. Here I will review the principles and status of the traditional and new indices of geomagnetic activity, discuss the present understanding of the various systematic patterns depicted by geomagnetic activity, including the centennial change of geomagnetic activity and its implications about the long-term change of the Sun.

  3. The Semiannual Variation of Great Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.; Cliver, E. W.; Ling, A. G.

    2001-12-01

    The occurrence frequency of the largest geomagnetic storms as measured by the aa index from 1868-present exhibits a well-defined semiannual modulation with 2.4 times as many great storms occurring during equinoctial months than at the solstices. We show that most, but not all, of this variation can be attributed to an equinoctial hypothesis whereby energy transfer from the solar wind to the magnetosphere is modulated by psi, the angle between the solar wind flow direction and Earth's dipole axis. After normalizing aa for the seasonal/daily variation of psi, the imbalance in great storm counts between equinoctial and solstitial months is reduced to a factor of 1.4.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Wilson, Robert M.; Hathaway, David H.

    2008-06-01

    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.

  6. Evidence for a Dominant Russell-McPherron/Rosenberg-Coleman Origin of the Semiannual Variation of Geomagnetic Activity in 1954 and 1996

    NASA Astrophysics Data System (ADS)

    Cliver, E. W.; Svalgaard, L.; Ling, A. G.

    2002-12-01

    Occasionally, the semiannual variation of geomagnetic activity is so pronounced that one can readily identify it in daily averages of the aa index during the year. The solar minimum years of 1954 and 1996 were two such intervals. Using solar eclipse data and the Svalgaard polarity index for 1954 and solar magnetic field and solar wind data for 1996, we show that the six-month wave in geomagnetic activity during these years was primarily due to a flattened current sheet resulting in a strong Rosenberg-Coleman effect (an axial polarity effect), which in turn produced a strong Russell-McPherron response in aa. When we normalize the aa data for these years for the equinoctial effect (based on the angle between the solar wind flow direction and Earth's dipole), we remove approximately 30% of the amplitude of the semiannual variation, implying a dominant axial/Russell-McPherron origin. When we perform this normalization for the entire 1868-1998 aa data set, we remove 75% of the six-month wave, indicating that, in general, the equinoctial effect is primarily responsible for the semiannual variation of geomagnetic activity.

  7. SUBJECT INDEX absolute-any (AA) critical criterion 134, 141, 152

    E-print Network

    Triantaphyllou, Evangelos

    230-232 common characteristic 74 common comparisons 105-112 complete pairwise comparisons 88 conflict among criteria 1 concordance index 14, see also TOPSIS (fuzzy and crisp) concordance matrix 16, see also scales 45-47 class 2 scales 45, 48-49 Closest Discrete Pairwise (CDP) matrix 32-43, 80, 98, 145, 202, 251

  8. What is a geomagnetic storm?

    NASA Technical Reports Server (NTRS)

    Gonzalez, W. D.; Joselyn, J. A.; Kamide, Y.; Kroehl, H. W.; Rostoker, G.; Tsurutani, B. T.; Vasyliunas, V. M.

    1994-01-01

    After a brief review of magnetospheric and interplanetary phenomena for intervals with enhanced solar wind-magnetosphere interaction, an attempt is made to define a geomagnetic storm as an interval of time when a sufficiently intense and long-lasting interplanetary convection electric field leads, through a substantial energization in the magnetosphere-ionosphere system, to an intensified ring current sufficiently strong to exceed some key threshold of the quantifying storm time Dst index. The associated storm/substorm relationship problem is also reviewed. Although the physics of this relationship does not seem to be fully understood at this time, basic and fairly well established mechanisms of this relationship are presented and discussed. Finally, toward the advancement of geomagnetic storm research, some recommendations are given concerning future improvements in monitoring existing geomagnetic indices as well as the solar wind near Earth.

  9. 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.

  10. On the local Hurst exponent of geomagnetic field fluctuations: Spatial distribution for different geomagnetic activity levels

    NASA Astrophysics Data System (ADS)

    Michelis, Paola De; Consolini, Giuseppe

    2015-04-01

    This study attempts to characterize the spatial distribution of the scaling features of the short time scale magnetic field fluctuations obtained from 45 ground-based geomagnetic observatories distributed in the Northern Hemisphere. We investigate the changes of the scaling properties of the geomagnetic field fluctuations by evaluating the local Hurst exponent and reconstruct maps of this index as a function of the geomagnetic activity level. These maps permit us to localize the different latitudinal structures responsible for disturbances and related to the ionospheric current systems. We find that the geomagnetic field fluctuations associated with the different ionospheric current systems have different scaling features, which can be evidenced by the local Hurst exponent. We also find that in general, the local Hurst exponent for quiet magnetospheric periods is higher than that for more active periods suggesting that the dynamical processes that are activated during disturbed times are responsible for changes in the nature of the geomagnetic field fluctuations.

  11. Canadian National Geomagnetism Program

    NSDL National Science Digital Library

    The Canadian National Geomagnetism Program provides excellent resources for keeping track of the Earth's ever-changing magnetic field throughout Canada. The information here covers "time-scales ranging from seconds to decades." Data include short- and long-term magnetic activity forecasts, and plots of one-minute variations of the geomagnetic field. Also, an in-depth geomagnetic hazards section discusses effects of magnetic storms on power systems, pipelines, and communication cables.

  12. 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.

  13. 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.

  14. The semiannual variation of great geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.; Cliver, E. W.; Ling, A. G.

    2002-08-01

    The occurrence frequency of the largest geomagnetic storms from 1868-1998 exhibits a well-defined semiannual modulation with more than twice as many storms occurring during equinoctial months than at the solstices. To examine the cause of this seasonal imbalance, we empirically obtained a new geomagnetic index aam that has the same seasonal and Universal Time variation as the am index. In effect, this extends the am index backward in time to 1868. By normalizing the aam time series for ?, the angle between the solar wind flow direction and Earth's dipole, we removed 75% of the amplitude of the six-month wave in monthly averages of aam and ~75% of the seasonal discrepancy in the numbers of great storms. We obtained similar percentages for the (unmodified) am index over the shorter 1959-1998 interval. These results indicate that most, though not all, of the discrepancy in storm counts between the equinoxes and solstices is due to an equinoctial effect.

  15. 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.

  16. 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).

  17. On correlations between the North Atlantic Oscillation, geopotential heights, and geomagnetic activity

    Microsoft Academic Search

    Peter Thejll; Bo Christiansen

    2003-01-01

    We investigate correlations between geomagnetic activity indices, the North Atlantic Oscillation (NAO), and stratospheric geopotential heights. It is shown that the correlation between the geomagnetic index Ap and the NAO index is high and significant since about 1970, that it is significant during winter only, that it was not significant before about 1970, and that the correlations are dominated by

  18. 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.

  19. 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.

  20. Dependence of geomagnetic activity on solar wind parameters - A statistical approach

    NASA Technical Reports Server (NTRS)

    Maezawa, K.

    1978-01-01

    A statistical analysis of a large body of data is used to give a visual representation of the relative influence of each solar wind/IMF parameter on geomagnetic activity. In addition an attempt is made to determine whether geomagnetic indices differ in their response to various solar wind/IMF parameters and to discuss the physical implications of these differences. It is recommended that ample care should be taken about what kind of geomagnetic index is to be used.

  1. 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).

  2. Hydromagnetic Theory of Geomagnetic Storms

    Microsoft Academic Search

    A. J. Dessler; E. N. Parker

    1959-01-01

    A hydromagnetic theory is presented which explains the average characteristics of geomagnetic storms. The magnetic storm is caused by a sudden increase in the intensity of the solar wind. Stresses are then set up in the geomagnetic field by the solar plasma impinging upon the geomagnetic field and becoming trapped in it. These stresses, which are propagated to the earth

  3. The Geomagnetic Storm on September 2000: a Clue to Sun-Earth Interaction

    Microsoft Academic Search

    E. Saiz; Y. Cerrato; C. Cid

    2006-01-01

    Reconnection is assumed as the most efficient physical mechanism involved in geomagnetic activity Then an intense southern and long duration interplanetary magnetic field provides to terrestrial magnetosphere energy enough to produce a geomagnetic storm event In this work we analyze the event on September 2000 where Dst index reaches -201 nT at 0 hours of doy 262 Theoretical models based

  4. Singificant relationship between perinatal geomagnetic field activity and anxiety levels in females

    Microsoft Academic Search

    K.-P. Ossenkopp; J. N. Nobrega

    1979-01-01

    The relationship between geomagnetic activity around the time of birth to subsequent responding on an anxiety test was examined in 13–16 year old high school students. The students were given a questionnaire designed to measure “state” and “trait” anxiety, and the scores on this questionnaire were correlated with daily geomagnetic activity measures (Ap index) for an 11 day period centered

  5. Introduction to Geomagnetic Fields

    Microsoft Academic Search

    William J. Hinze

    2003-01-01

    Coincidentally, as I sat down in late October 2003 to read and review the second edition of Wallace H. Campbell's text, Introduction to Geomagnetic Fields, we received warnings from the news media of a massive solar flare and its possible effect on power supply systems and satellite communications. News programs briefly explained the source of Sun-Earth interactions. If you are

  6. Enhancement in Surface Atmospheric Pressure Variability Associated with a Major Geomagnetic Storm

    E-print Network

    A. M. Selvam; S. Fadnavis; S. U. Athale; M. I. R. Tinmaker

    1998-07-03

    Observational studies indicate that there is a close association between geomagnetic storm and meteorological parameters. Geomagnetic field lines follow closely the isobars of surface pressure . A Physical mechanism linking upper atmospheric geomagnetic storm disturbances with tropospheric weather has been proposed by the author and her group where it is postulated that vertical mixing by turbulent eddy fluctuations results in the net transport upward of positive charges originating from lower levels accompanied simultaneously by downward flow of negative charges from higher levels. The present study reports enhancement of high frequency (pressure during March 1989 in association with major geomagnetic storm (Ap index = 246) on 13 march 1989.

  7. Introduction to Geomagnetic Fields

    NASA Astrophysics Data System (ADS)

    Hinze, William J.

    Coincidentally, as I sat down in late October 2003 to read and review the second edition of Wallace H. Campbell's text, Introduction to Geomagnetic Fields, we received warnings from the news media of a massive solar flare and its possible effect on power supply systems and satellite communications. News programs briefly explained the source of Sun-Earth interactions. If you are interested in learning more about the physics of the connection between sun spots and power supply systems and their impact on orbiting satellites, I urge you to become acquainted with Campbell's book. It presents an interesting and informative explanation of the geomagnetic field and its applications to a wide variety of topics, including oil exploration, climate change, and fraudulent claims of the utility of magnetic fields for alleviating human pain. Geomagnetism, the study of the nature and processes of the Earth's magnetic fields and its application to the investigation of the Earth, its processes, and history, is a mature science with a well-developed theoretical foundation and a vast array of observations. It is discussed in varied detail in Earth physics books and most entry-level geoscience texts. The latter treatments largely are driven by the need to discuss paleomagnetism as an essential tool in studying plate tectonics. A more thorough explanation of geomagnetism is needed by many interested scientists in related fields and by laypersons. This is the objective of Campbell's book. It is particularly germane in view of a broad range of geomagnetic topics that are at the forefront of today's science, including environmental magnetism, so-called ``jerks'' observed in the Earth's magnetic field, the perplexing magnetic field of Mars, improved satellite magnetic field observations, and the increasing availability of high-quality continental magnetic anomaly maps, to name only a few.

  8. An Introduction to Geomagnetism

    NSDL National Science Digital Library

    Sten Odenwald

    This tutorial introduces students to geomagnetism, the Earth's magnetic field, and its changes through time and space. Topics include the properties of Earth's magnetic field, how it makes a compass work, and why Earth has a magnetic field. There is also discussion of magnetic reversals, a set of links to additional reading and resources, and a set of classroom activities on the basic properties of magnetic fields and Earth's changing magnetic field.

  9. Geomagnetic Field During a Reversal

    NASA Technical Reports Server (NTRS)

    Heirtzler, J. R.

    2003-01-01

    It has frequently been suggested that only the geomagnetic dipole, rather than higher order poles, reverse during a geomagnetic field reversal. Under this assumption the geomagnetic field strength has been calculated for the surface of the Earth for various steps of the reversal process. Even without an eminent a reversal of the field, extrapolation of the present secular change (although problematic) shows that the field strength may become zero in some geographic areas within a few hundred years.

  10. 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.

  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. Long-term occurrence probabilities of intense geomagnetic storm events

    Microsoft Academic Search

    K. Tsubouchi; Y. Omura

    2007-01-01

    A quantitative assessment of the occurrence probability of intense geomagnetic storms (peak Dst < -100 nT) has been investigated by analyzing the Dst index time series database from 1957 to 2001. The main purpose was to derive two parameters, the probable intensity S T and the occurrence frequency lambda t , that can act as proxies for long-term space weather

  13. On the geomagnetic effects of solar wind interplanetary magnetic structures

    Microsoft Academic Search

    E. Echer; W. D. Gonzalez; M. V. Alves

    2006-01-01

    We present in this work a statistical study of the geoeffectiveness of the solar wind magnetic interplanetary structures over the entire observational period (1964–2003). The structures studied were magnetic clouds (MCs, 170 events), corotating interaction regions (CIRs, 727 events) and interplanetary shocks (830 events). The geoeffectiveness was assessed in terms of the geomagnetic index Kp, AE, and Dst peak values

  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. Geomagnetic Temporal Spectrum Catherine Constable 1 GEOMAGNETIC TEMPORAL SPECTRUM

    E-print Network

    Constable, Catherine G.

    as a result of dayside solar heating. Lightning generates high frequency Schumann resonances in the Earth of geomagnetic variations. The power spectral density S(f) is a measure of the power in geomagnetic field variations at frequency f. When integrated over all frequencies it measures the total variance

  16. Evolution of Solar and Geomagnetic Activity Indices, and Their Relationship: 1960 - 2001

    NASA Astrophysics Data System (ADS)

    Verbanac, G.; Mandea, M.; Vršnak, B.; Sentic, S.

    2011-07-01

    We employ annually averaged solar and geomagnetic activity indices for the period 1960 - 2001 to analyze the relationship between different measures of solar activity as well as the relationship between solar activity and various aspects of geomagnetic activity. In particular, to quantify the solar activity we use the sunspot number R s, group sunspot number R g, cumulative sunspot area Cum, solar radio flux F10.7, and interplanetary magnetic field strength IMF. For the geomagnetic activity we employ global indices Ap, Dst and Dcx, as well as the regional geomagnetic index RES, specifically estimated for the European region. In the paper we present the relative evolution of these indices and quantify the correlations between them. Variations have been found in: i) time lag between the solar and geomagnetic indices; ii) relative amplitude of the geomagnetic and solar activity peaks; iii) dual-peak distribution in some of solar and geomagnetic indices. The behavior of geomagnetic indices is correlated the best with IMF variations. Interestingly, among geomagnetic indices, RES shows the highest degree of correlation with solar indices.

  17. SEMIANNUAL VARIATION OF GEOMAGNETIC ACTIVITY

    Microsoft Academic Search

    C.T. Russell; R. L. McPherron

    1973-01-01

    The semiannual variation in geomagnetic activity is well established in geomagnetic data Its explanation has remained elusive, however. We propose, simply, that it 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

  18. Federal support of geomagnetism

    NASA Astrophysics Data System (ADS)

    Cain, Joseph C.; Lund, Steve; Lanzerotti, L. J.

    Recent pressures to reduce federal agency support in several scientific areas of national interest have motivated the AGU GP Section to review the present status of geomagnetism in federal agencies. Federal GP activities are currently spread over four agencies (the National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA), U.S. Geological Survey (USGS), and Naval Oceanographic Office), two of which have in-house research efforts. Partly because of recent budget reductions, the support and encouragement that each of these groups receives for scientific research has waned severely.

  19. Deterministic chaos in geomagnetic reversals

    NASA Astrophysics Data System (ADS)

    Sidorovskaia, N.; Richter, C.; Rypina, I.

    2013-12-01

    In a recent publication Gissinger (Eur. Phys. J. B 85,137, 2012) proposed a new deterministic chaos model for the generation of the Earth's magnetic field and an explanation of the observed statistics of geomagnetic pole reversal occurrences. The new model is described by a system of three coupled non-linear differential equations limited to quadratic terms. If such a low degree of freedom system is adequate for the description of Earth's geomagnetic dynamo, it has to reflect in statistics and non-linear dynamic characteristics of the temporal interval between geomagnetic reversals. We present the results of the extended statistical analysis of the 2012 compilation of magnetic reversal data spanning the last 170 m.yr. We calculate the Grassberger-Procaccia correlation dimension in the context of a single-variable dataset of waiting times between measured geomagnetic reversals in paleomagnetic records to predict the complexity of the underlying geomagnetic dynamo system. First, we inspect if the time series of geomagnetic reversals has the same or a different correlation dimension than a random time series with the same number of points. This allows us to determine whether geomagnetic reversals are indistinguishable from a stochastic process, or are described by a chaotic rather than stochastic process. Next, higher-dimensional vectors are constructed from the time series of geomagnetic reversals, and correlation dimension is calculated for these higher-dimensional vectors to find out if the correlation dimension has a convergence limit as we increase the vector space dimension. If the convergence limit is revealed from the experimental dataset, then the geomagnetic reversals are chaotic rather than stochastic and are described by a system with limited number of degrees of freedom determined by the correlation dimension. If one expects to describe the geomagnetic dynamo by a low-order system of non-linear differential equations, the system should have a low dimension (self-organized) strange attractor in its phase space indicated by a low correlation dimension of observable data.

  20. 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.

  1. 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.

  2. 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

  3. Proterozoic Geomagnetic Field Geometry

    NASA Astrophysics Data System (ADS)

    Panzik, J. E.; Evans, D. A.

    2011-12-01

    Pre-Mesozoic continental reconstructions and paleoclimatic inferences from paleomagnetism rely critically upon the assumption of a time-averaged geocentric axial dipole (GAD) magnetic field. We have been testing the GAD assumption and localized non-dipole components in a different manner, by observing directional variations within the Matachewan, Mackenzie and Franklin dyke swarms. Large dyke swarms, commonly emplaced within a few million years, provide the necessary broad areal coverage to perform a test of global geomagnetic field geometry. Our analysis varies the quadrupole and octupole values of the generalized paleolatitude equation to determine a minimal angular dispersion and maximum precision of paleopoles from each dyke swarm. As a control, paleomagnetic data from the central Atlantic magmatic province (CAMP) show the sensitivities of our method to non-GAD contributions to the ancient geomagnetic field. Within the uncertainties, CAMP data are consistent with independent estimates of non-GAD contributions derived from global tectonic reconstructions (Torsvik & Van der Voo, 2002). Current results from the three Proterozoic dyke swarms all have best fits that are non-dipolar, but they differ in their optimal quadrupole/ octupole components. Treated together under the hypothesis of a static Proterozoic field geometry, the data allow a pure GAD geodynamo within the uncertainty of the method. Current results were performed using Fisherian statistics, but Bingham statistics will be included to account for the ellipticity of data.

  4. 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

  5. Secular trends in storm-level geomagnetic activity

    USGS Publications Warehouse

    Love, J.J.

    2011-01-01

    Analysis is made of K-index data from groups of ground-based geomagnetic observatories in Germany, Britain, and Australia, 1868.0-2009.0, solar cycles 11-23. Methods include nonparametric measures of trends and statistical significance used by the hydrological and climatological research communities. Among the three observatory groups, German K data systematically record the highest disturbance levels, followed by the British and, then, the Australian data. Signals consistently seen in K data from all three observatory groups can be reasonably interpreted as physically meaninginful: (1) geomagnetic activity has generally increased over the past 141 years. However, the detailed secular evolution of geomagnetic activity is not well characterized by either a linear trend nor, even, a monotonic trend. Therefore, simple, phenomenological extrapolations of past trends in solar and geomagnetic activity levels are unlikely to be useful for making quantitative predictions of future trends lasting longer than a solar cycle or so. (2) The well-known tendency for magnetic storms to occur during the declining phase of a sunspot-solar cycles is clearly seen for cycles 14-23; it is not, however, clearly seen for cycles 11-13. Therefore, in addition to an increase in geomagnetic activity, the nature of solar-terrestrial interaction has also apparently changed over the past 141 years. ?? Author(s) 2011.

  6. Geomagnetic variation related to Sakurajima volcano eruption

    NASA Astrophysics Data System (ADS)

    Kim, K.; Lee, C. W.

    2014-12-01

    Geomagnetic field has been studied for measuring precursor signals to understand earthquake events by geoscientists. Furthermore, analysis of geomagnetic data helps detect symptom of volcanic eruption. In this study, we process geomagnetic data for Sakurajima volcano case which erupted on Aug 18, 2013 with a large scale of eruption in Japan. This volcanic activity has an effect on geomagnetic data not only geomagnetic observatory in Japan but also in Korea. This study carries out that the geomagnetic variation has been analyzed using geomagnetic data from Cheongyang observatory in Korea and several geomagnetic observatories in Japan. First, we compared the geomagnetic data directly from each component, then searching the difference by volcanic eruption. Secondly, we execute wavelet based semblance from geomagnetic data in order to confirm the correlation between geomagnetic data and effect from volcano activity. As a result, geomagnetic diurnal variation is generally about 50 nT. However, It hardly shows geomagnetic variation on z component and displays about 15 nT on total component before Sakurajima volcano eruption at Kanoya geomagnetic observatory. Moreover, we could confirm uncorrelated event by wavelet based semblance analysis what estimated to volcano activity. This study conducted to confirm geomagnetic variation related to volcano activity getting meaningful result.

  7. Dependence of Quiet Time Geomagnetic Activity Seasonal Variation on the Solar Magnetic Polarity

    NASA Astrophysics Data System (ADS)

    Oh, Suyeon

    2013-03-01

    The geomagnetic activity shows the semiannual variation stronger in vernal and autumnal equinoxes than in summer and winter solstices. The semiannual variation has been explained by three main hypotheses such as Axial hypothesis, Equinoctial hypothesis, and Russell-McPherron Effect. Many studies using the various geomagnetic indices have done to support three main hypotheses. In recent, Oh & Yi (2011) examined the solar magnetic polarity dependency of the geomagnetic storm occurrence defined by Dst index. They reported that there is no dependency of the semiannual variation on the sign of the solar polar fields. This study examines the solar magnetic polarity dependency of quiet time geomagnetic activity. Using Dxt index (Karinen & Mursula 2005) and Dcx index (Mursula & Karinen 2005) which are recently suggested, in addition to Dst index, we analyze the data of three-year at each solar minimum for eight solar cycles since 1932. As a result, the geomagnetic activity is stronger in the period that the solar magnetic polarity is anti-parallel with the Earth's magnetic polarity. There exists the difference between vernal and autumnal equinoxes regarding the solar magnetic polarity dependency. However, the difference is not statistically significant. Thus, we conclude that there is no solar magnetic polarity dependency of the semiannual variation for quiet time geomagnetic activity.

  8. 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.

  9. 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.

  10. 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.

  11. Probing Geomagnetic Jerks combining Geomagnetic and Earth Rotation Observations (Invited)

    NASA Astrophysics Data System (ADS)

    Holme, R. T.; de Viron, O.

    2013-12-01

    Geomagnetic jerks, first observed in the late 1970s, are the most rapid variations in the observed geomagnetic field that are believed to be of internal origin. Their occurence has been correlated with a number of different geophysical phenomena. Here we consider simultaneous features in variations in Earth's length of day. Recently, we have provided a simple description of non-atmospheric variations in length of day (LOD), consisting of 3 components: a slowly varying decadal trend, a 5.9-year oscillation, and occasional sudden jumps. Both of the shorter period parts of this correlate with geomagnetic jerks, with peaks in the LOD oscillation being contemporaneous with well-known jerk occurances (for example in 1969, 1972, 1978 and 1982), and jumps in the LOD fitting a jerk observed in satellite data in 2003.5. The simultaneous observation of these two features constrains Earth structure, in particular limiting the electric conductivity of the deep mantle. However, the nature of the LOD changes also may change the paradigm for the study of jerk timings. it is customarily assumed that the jerks represent features in the geomagnetic field that are continuous in the secular variation, but discontinuous in its derivative, the secular acceleration. However, a jump in LOD suggested by the modelling of the data would correspond also to a jump in SV, thus invalidating standard methods for temporal location of a jerk (which will consider the intersection of best-fit straight lines to the secular variation before and after). Olsen and Mandea have localised a jerk in satellite virtual observatory data using flow modelling; this seems the most promising method to investigate whether jerks could have discontinuous secular variation. We apply similar methods to time series of virtual geomagnetic obseratories from satellite data to further explore geomagnetic jerks and their rotational links in the geomagnetic satellite era.

  12. The sub- and quasi- centurial cycles in solar and geomagnetical data series /(s2)

    E-print Network

    Komitov, B; Duchlev, P; Dechev, M; Penev, K; Koleva, K

    2010-01-01

    The subject of this paper is the existence and stability of solar cycles with duration in the range of 20-250 years. Five type of data series are used: 1) The Zurich series (1749-2009), the mean annual International sunspot number Ri; 2) The Group sunspot number series Rh (1610-1995); 3) The simulated extended sunspot Rsi number from Extended time series of Solar Activity Indices (ESAI) (1090- 2002); 4) The simulated extended geomagnetic aa-index from ESAI (1099-2002); 5) The Meudon filament series (1919-1991) (it is used only particularly). Data series are smoothed over 11 years and supercenturial trends are removed. Two principally independent methods of time series analysis are used: the T-R periodogram analysis (both in the standard and "scanning window" regimes) and the wavelet-analysis. The obtained results are very similar. It is found that in all series a strong cycle with mean duration of 55-60 years exists. It is very well expressed in the 18th and the 19th centuries. It is less pronounced during th...

  13. The sub- and quasi-centurial cycles in solar and geomagnetic activity data series

    E-print Network

    Komitov, Boris; Duchlev, Peter; Dechev, Momchil; Penev, Kaloyan; Koleva, Kostadinka

    2010-01-01

    The subject of this paper is the existence and stability of solar cycles with durations in the range of 20-250 years. Five types of data series are used: 1) The Zurich series (1749-2009 AD), the mean annual International sunspot number Ri, 2) The Group sunspot number series Rh (1610-1995 AD), 3) The simulated extended sunspot Rsi number from Extended time series of Solar Activity Indices (ESAI) (1090-2002 AD), 4) The simulated extended geomagnetic aa-index from ESAI (1099-2002 AD), 5) The Meudon filament series (1919-1991 AD) (it is used only particularly). Data series are smoothed over 11 years and supercenturial trends are removed. Two principally independent methods of time series analysis are used: the T-R periodogram analysis (both in the standard and "scanning window" regimes) and the wavelet-analysis. The obtained results are very similar. It is found that in all series a strong cycle with mean duration of 55-60 years exists. It is very well expressed in the 18th and the 19th centuries. It is less pron...

  14. 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.

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

    Microsoft Academic Search

    S. Y. Waghmare

    2009-01-01

    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

  16. Interplanetary origin of multiple-dip geomagnetic storms

    Microsoft Academic Search

    J. Zhang; I. G. Richardson; D. F. Webb

    2008-01-01

    In this paper, we have systematically investigated the interplanetary drivers of major dips during intense (Dst ? ?100 nT) geomagnetic storms in 1996–2006. A major dip is defined as a temporary decrease in Dst index with amplitude larger than 14.5 nT. Multiple dips result in a storm if regions of geoeffective solar wind with strong southward magnetic fields are separated

  17. 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

  18. On statistical relationship of solar, geomagnetic and human activities.

    PubMed

    Alania, M V; Gil, A; Modzelewska, R

    2004-01-01

    Data of galactic cosmic rays, solar and geomagnetic activities and solar wind parameters on the one side and car accident events (CAE) in Poland on the other have been analyzed in order to reveal the statistical relationships among them for the period of 1990-2001. Cross correlation and cross spectrum of the galactic cosmic ray intensity, the solar wind (SW) velocity, Kp index of geomagnetic activity and CAE in Poland have been carried out. It is shown that in some epochs of the above-mentioned period there is found a reliable relationship between CAE and solar and geomagnetic activities parameters in the range of the different periodicities, especially, 7 days. The periodicity of 7 days revealed in the data of the CAE has the maximum on Friday without any exception for the minimum and maximum epochs of solar activity. However, the periodicity of 7 days is reliably revealed in other parameters characterizing galactic cosmic rays, SW, solar and geomagnetic activities, especially for the minimum epoch of solar activity. The periodicity of 3.5 days found in the series of CAE data more or less can be completely ascribed to the social effects, while the periodicity of 7 days can be ascribed to the social effect or/to the processes on the Sun, in the interplanetary space and in the Earth's magnetosphere and atmosphere. PMID:15880899

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Kotzé, 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.

  1. 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.; Häggström, 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.

  2. What is a geomagnetic storm?

    Microsoft Academic Search

    W. D. Gonzales; J. A. Joselyn; Y. Kamide; H. W. Kroehl; G. Rostoker; B. T. Tsurutani; V. M. Vasyliunas

    1994-01-01

    The authors present a review of geomagnetic storm research. They examine the interaction of the solar wind with the magnetosphere. They argue that a storm results from the extended interaction of the solar wind\\/magnetosphere when a strong convection electric field is generated, which is able to perturb the ring current above some threshold level, triggering the event. They touch on

  3. A two-satellite study of the neutral atmosphere response to a major geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Trinks, H.; Chandra, S.; Spencer, N. W.; Von Zahn, U.

    1976-01-01

    Simultaneous measurements of neutral composition from both Esro 4 and Aeros-A have provided a complementary set of data for studying the temporal and spatial characteristics of the thermosphere during a major geomagnetic storm. From the correlative studies of Ar and N2 number densities, the magnetic index Aps, and ground-based magnetograms, it is found that the Ap index only reflects the gross features of atmospheric disturbances. Superposed on the global component are localized regions of 'hot spots' which appear correlated with ground-based magnetograms. Because of these localized disturbances, the interpretation of the atmospheric response to geomagnetic storms becomes ambiguous.

  4. Semiannual Variation of Geomagnetic Activity: Protons or Photons?

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.; Schulz, M.; Cliver, E. W.

    2004-12-01

    The cause(s) of the semiannual variation (SAV) of geomagnetic activity is a problem of long standard ( ˜100 years). The various mechanisms put forward can be divided into 'excitations' and 'modulations'. Using 45 years of the am-index, we show that the SAV is a modulation of existing activity. The modulation is a function of the angle between the Earth's dipole moment and either (1) the aberrated solar wind velocity and/or (2) the sun-Earth line, causing both time of year and time of day (UT) variations. Here we examine the correlation of geomagnetic activity with directions (1) and (2). Mechanisms involving interaction between the solar wind and the magnetopause would correlate best with direction (1). Mechanisms involving ionospheric conductance would correlate best with direction (2).

  5. Modeling Longitudinal Hemispheric Differences during Geomagnetic Storm Times

    NASA Astrophysics Data System (ADS)

    Greer, K.; Immel, T. J.; Ridley, A. J.

    2014-12-01

    Work by Immel and Mannucci [2013] has indicated that geomagnetic storms causes a larger effect on the ionospheric TEC (Total Electron Count) in the American sector than anywhere else on the planet, suggesting that there is a longitude dependent (UT) effect which is important for correctly understanding the impact, structure and timing of geomagnetic storms. Here we examine the extent to which numerical models appropriately reproduce the observed results. Using Global Ionosphere-Thermosphere Model (GITM) [Ridley et al., 2006] coupled with realistic transport to examine the underlying mechanisms of the longitude-dependent storm enhancements and whether these mid-latitude enhancements are connected to high-latitude changes. TEC measurements, the Dst index, and are used in conjunction with model output.

  6. Solar wind and geomagnetism: toward a standard classification of geomagnetic activity from 1868 to 2009

    E-print Network

    Zerbo, J. L.

    We examined solar activity with a large series of geomagnetic data from 1868 to 2009. We have revisited the geomagnetic activity classification scheme of Legrand and Simon (1989) and improve their scheme by lowering the ...

  7. 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.

  8. 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.

  9. 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.

  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. Effect of precipitating electrons on middle atmospheric ozone during enhanced geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Daae, Marianne; Kleinknecht, Nora H.; Espy, Patrick; Clilverd, Mark

    We will investigate the solar influence on the destruction of middle atmospheric ozone by looking at ozone variations with respect to the Kp and Dst indices. A microwave radiometer developed at the British Antarctic Survey has provided 30-min temporal and 8-km vertical resolution ozone profiles between 30 and 80 km deep within the Antarctic vortex at Troll Station (72S, 2.5E, L=4.76). The Kp-index provides a measure of the geomagnetic depression at mid-latitudes occurring during enhanced geomagnetic activity, and the Dst-index indicates the geomagnetic depression at equator due to pronounced and prolonged geomagnetic activity. The number of precipitating electrons increases with increasing geomagnetic activity and thus these indices provide an indicator of the number of NO+ and HOx produced by these electrons in the upper atmosphere. The lifetime of HOx and its associated ozone destruction is short, whilst NO+ can form long-lived NOx, which will affect ozone over a wider temporal and spatial range due to transport. By doing a superposed epoch analysis of night-time ozone variations as a function of the Kp and Dst indices, we will present a statistical measure of the effect and efficiency of upper atmospheric NOx and HOx destruction of ozone.

  12. On the limitations of geomagnetic measures of interplanetary magnetic polarity

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    The maximum attainable accuracy in inferring the interplanetary magnetic polarity from polar cap magnetograms is about 88%. This is achieved in practice, when high-latitude polar cap stations are used during local summer months, and the signature in the ground records is strong. An attempt by Svalgaard (1972) to use this effect to infer an index of interplanetary magnetic polarity back to 1926 has not been so successful. Furthermore, some of the properties of the index have changed with time. Prior to 1963, the inferred polarities are strongly dependent on geomagnetic activity, while after this time they are not. Thus, this index should not be used to separate solar-magnetic from solar-activity effects prior to 1963.

  13. Statistics of extreme geomagnetically induced current events

    Microsoft Academic Search

    A. Pulkkinen; R. Pirjola; A. Viljanen

    2008-01-01

    In this work, space weather events associated with extreme geoelectric field and geomagnetically induced current (GIC) magnitudes are investigated. The geoelectric field and consequent GIC are computed using geomagnetic field recordings over an extended time period and ground conductivity and technological system configurations favorable for large GIC. The statistics are derived for both overall occurrence of the geoelectric field and

  14. Geomagnetic cutoff rigidity variation of cosmic rays and their relation with the interplanetary parameters during the disturbance of September 2005

    NASA Astrophysics Data System (ADS)

    Vernova, Elena; Tyasto, Marta; Danilova, Olga; Sdobnov, Valerii

    2015-04-01

    The storm September 7-15, 2005 was characterized by two strong perturbations of the solar wind speed that reached up to 1000 km/s. We investigated the relations of the theoretical and experimental cutoff rigidities with the geomagnetic Dst-index and the interplanetary parameters during the geomagnetic storm September 7-15, 2005. Theoretical vertical effective geomagnetic thresholds have been calculated by the trajectory tracing method in the magnetic field of the disturbed magnetosphere Tsyganenko (TS01) model and the experimental cutoff rigidities have been obtained by the spectrographic global survey technique using the data from the global network of neutron monitors. Combined analysis of temporal variations of the theoretical and experimental geomagnetic thresholds was performed.

  15. 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.

  16. Modeling of severe geomagnetic storms of solar cycle 23 by means of artificial neural networks

    NASA Astrophysics Data System (ADS)

    Revallo, Milos; Valach, Fridrich; Hejda, Pavel; Bochnicek, Josef

    2015-04-01

    We set up a model for strong geomagnetic storms of solar cycle 23 using the method of artificial neural networks combined with an empirical model of the solar wind magnetosphere interaction. The set of solar wind data obtained from the ACE satellite is considered and the corresponding geomagnetic response is modeled and compared with real data. The discontinuity in magnetic field at the magnetopause is shown to play a key role in this study. The geomagnetic response is evaluated in terms of the Dst index. To assess the model performance, we compute the skill scores, namely the correlation coefficient and the prediction efficiency. We compare the model with previously known similar models based on artificial neural networks.

  17. 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.

  18. Magnetic local time dependence of geomagnetic disturbances contributing to the AU and AL indices

    NASA Astrophysics Data System (ADS)

    Tomita, S.; Nosé, M.; Iyemori, T.; Toh, H.; Takeda, M.; Matzka, J.; Bjornsson, G.; Saemundsson, T.; Janzhura, A.; Troshichev, O.; Schwarz, G.

    2011-04-01

    The Auroral Electrojet (AE) indices, which are composed of four indices (AU, AL, AE, and AO), are calculated from the geomagnetic field data obtained at 12 geomagnetic observatories that are located in geomagnetic latitude (GMLAT) of 61.7°-70°. The indices have been widely used to study magnetic activity in the auroral zone. In the present study, we examine magnetic local time (MLT) dependence of geomagnetic field variations contributing to the AU and AL indices. We use 1-min geomagnetic field data obtained in 2003. It is found that both AU and AL indices have two ranges of MLT (AU: 15:00-22:00 MLT, ~06:00 MLT; and AL: ~02:00 MLT, 09:00-12:00 MLT) contributing to the index during quiet periods and one MLT range (AU: 15:00-20:00 MLT, and AL: 00:00-06:00 MLT) during disturbed periods. These results are interpreted in terms of various ionospheric current systems, such as, Sqp, Sq, and DP2.

  19. Centennial to millennial geomagnetic field variations

    NASA Astrophysics Data System (ADS)

    Korte, Monika; Muscheler, Raimund

    2012-06-01

    Reconstructions of the geomagnetic field in the past represent a useful tool not only to investigate the geodynamo process, but also to estimate the effect of geomagnetic shielding for any studies on cosmogenic radionuclides and galactic cosmic rays. A number of new millennial-scale geomagnetic field reconstructions have been published over the last years, based on improved global archeo- and paleomagnetic data compilations. Here we review several spherical harmonic models and compare their dipole field predictions to reconstructions based on virtual axial dipole moments and virtual geomagnetic poles. Dipole intensity estimates from cosmogenic radionuclide production records, with suitable filtering to minimise the solar influence, have also been included in the comparison to provide independent information about variations in the strength of the geomagnetic field. However, due to differences among geomagnetic models and between 14C and 10Be production records this comparison is fairly inconclusive with respect to multi-centennial variations. Different geomagnetic dipole tilt reconstructions agree well for much of the Holocene, but dipole moment estimates still differ substantially. Recent spherical harmonic models for the past 3 and 10 kyrs have improved considerably compared to earlier versions. Nevertheless at present we recommend to test if any interpretation depends on the choice of model.

  20. 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.

  1. 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. 7.4°N, Long. 3.9°N) and Ilorin (Lat. 8.5°N, Long. 4.55°E)- 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.

  2. Numerical Modeling of Auroral and Equatorial Electrojet Behavior during Geomagnetic Storm Sequence on September 9-14, 2005

    NASA Astrophysics Data System (ADS)

    Klimenko, Maxim; Klimenko, Vladimir

    In Klimenko et al., 2006 the model of electric field and zonal current in the Earth's ionosphere has been presented. This model has been included into the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) developed in WD IZMIRAN (Namgaladze et al., 1988). The modified GSM TIP model has allowed to describe more correctly the behavior of electric field and different ionospheric parameters at low latitudes, and also to investigate the behavior of auroral and equatorial electrojets. In the given research we present the calculation results of behavior of auroral and equatorial electrojets during geomagnetic storm sequence on September 9-14, 2005. The calculations have been executed with use of the modified GSM TIP model. At that the model input parameters, such as the potential difference through polar caps, field-aligned currents of second region and particle precipitation fluxes and energy were set as function of AE-and Kp-indices of geomagnetic activity according to different empirical models Feshchenko and Maltsev, 2003; Zhang and Paxton, 2008 and morphological representations Cheng et al., 2008. Furthermore, at the storm sudden commencement phase we taken into account the shift of field-aligned currents of the second region into the lower latitudes as by Sojka et al., 1994 and 30 min. time delay of variations of the field-aligned currents of the second region relative to the variations of the potential drop through polar caps. Also, we taken into account the ionospheric effects of solar flares, which were taken place during the considered period. The calculation results are analyzed according to known morphological representations about auroral and equatorial electrojet behavior during geomagnetic storms. This study is supported by RFBR grant 08-05-00274. References Cheng Z.W., Shi J.K., Zhang T.L., Dunlop M. and Liu Z.X. Relationship between FAC at plasma sheet boundary layers and AE index during storms from August to October, 2001. Sci. China Ser. E-Tech. Sci., 2008, Vol. 51, No. 7, 842-848. Feshchenko E.Yu., Maltsev Yu.P. Relations of the polar cap voltage to the geophysical activity. Physics of Auroral Phenomena: XXVI Annual Seminar (February 25-28, 2003): Proc./PGI KSC RAS. Apatity, 2003, 59-61. Klimenko M.V., Klimenko V.V., Bryukhanov V.V. Numerical Simulation of the Electric Field and Zonal Current in the Earth's Ionosphere: The Dynamo Field and Equatorial Electrojet. Geomagn. Aeron. 2006, Vol. 46, No. 4, 457-466. Namgaladze A.A., Korenkov Yu.N., Klimenko V.V., Karpov I.V., Bessarab F.S., Surotkin V.A., Glushenko T.A., Naumova N.M. Global model of the thermosphere-ionosphere-protonosphere system. Pure and Applied Geophysics (PAGEOPH), 1988, Vol. 127, No. 2/3, 219-254. Sojka J.J., Schunk R.W., Denig W.F. Ionospheric response to the sustained high geomagnetic activity during the March '89 great storm. J. Geophys. Res., 1994, Vol. 99, No. A11, 21341-21352. Zhang Y., Paxton L.J. An empirical Kp-dependent global auroral model based on TIMED/GUVI FUV data. J. Atmos. Solar-Terr. Phys., 2008, Vol. 70, 1231-1242.

  3. Reconstructing the Holocene geomagnetic field

    NASA Astrophysics Data System (ADS)

    Korte, Monika; Constable, Catherine; Donadini, Fabio; Holme, Richard

    2011-12-01

    Knowledge of the Holocene evolution of Earth's magnetic field is important for understanding geodynamo processes in the core, is necessary for studying long-term solar-terrestrial relationships, and can provide useful age constraints for archeologicaland stratigraphic applications. Continuous time-varying global field models based on archeo- and paleomagnetic data are useful tools in this regard. We use a comprehensive data compilation and recently refined modelling strategies to produce CALS10k.1b, the first time-varying spherical harmonic geomagnetic field model spanning 10 ky. The model is an average obtained from bootstrap sampling to take account of uncertainties in magnetic components and ages in the data (and hence has version number 1b instead of 1). This model shows less spatial and temporal resolution than earlier versions for 0-3 ka, and particularly aims to provide a robust representation of the large-scale field at the core-mantle boundary (CMB). We discuss the geomagnetic dipole evolution and changes in Holocene magnetic field morphology at the CMB as shown by the new reconstruction. The results are compatible with earlier models ( CALS3k.3 and CALS3k.4) for 0-3 ka, but reveal some clear deficiencies in the 0-7 ka CALS7K.2 model prior to 3 ka. CALS10k.1b is able to resolve mobile and structurally-evolving high latitude radial field flux lobes at the CMB in both hemispheres, as well as persistent non-zonal structure, in the 10 ky average. Contributions to the average field from time-varying structures in the equatorial Indonesian-Australian region are particularly striking.

  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. The Geomagnetic Field: Frequently Asked Questions

    NSDL National Science Digital Library

    This is a group of frequently asked questions and answers about Earth's magnetic field and poles, the magnetic compass, magnetic reversals, and geomagnetic models. Links to maps and illustrations are embedded in the text.

  6. 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.

  7. 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.

  8. Dependence of Geomagnetic Storms on Their Associated Halo CME Parameters

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Ok; Moon, Y.-J.; Lee, Kyoung-Sun; Kim, R.-S.

    2014-06-01

    We compare the geoeffective parameters of halo coronal mass ejections (CMEs). We consider 50 front-side full-halo CMEs (FFH CMEs), which are from the list of Michalek, Gopalswamy, and Yashiro ( Solar Phys. 246, 399, 2007), whose asymmetric-cone model parameters and earthward-direction parameter were available. For each CME we use its projected velocity [ V p], radial velocity [ V r], angle between cone axis and sky plane [ ?] from the cone model, earthward-direction parameter [ D], source longitude [ L], and magnetic-field orientation [ M] of its CME source region. We make a simple linear-regression analysis to find out the relationship between CME parameters and Dst index. The main results are as follows: i) The combined parameters [( V r D)1/2 and V r ?] have higher correlation coefficients [cc] with the Dst index than the other parameters [ V p and V r]: cc=0.76 for ( V r D)1/2, cc=0.70 for V r ?, cc=0.55 for V r, and cc=0.17 for V p. ii) Correlation coefficients between V r ? and Dst index depend on L and M; cc=0.59 for 21 eastern events [E], cc=0.80 for 29 western events [W], cc=0.49 for 17 northward magnetic-field events [N], and cc=0.69 for 33 southward magnetic-field events [S]. iii) Super geomagnetic storms (Dst?-200 nT) only appear in the western and southward magnetic-field events. The mean absolute Dst values of geomagnetic storms (Dst?-50 nT) increase with an order of E+N, E+S, W+N, and W+S events; the mean absolute Dst value (169 nT) of W+S events is significantly larger than that (75 nT) of E+N events. Our results demonstrate that not only do the cone-model parameters together with the earthward-direction parameter improve the relationship between CME parameters and Dst index, but also the longitude and the magnetic-field orientation of a FFH CME source region play a significant role in predicting geomagnetic storms.

  9. 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.

  10. Ionosphere response to recurrent geomagnetic activity in 1974

    NASA Astrophysics Data System (ADS)

    Fang, Tzu-Wei; Forbes, Jeffrey M.

    2012-01-01

    The 9 day variation of Earth's thermosphere neutral density in 2005 and 2006 is known to have been influenced by rotating solar coronal holes and the quasiperiodic solar wind high-speed streams (HSSs) and by the concomitant recurrent geomagnetic activity that they induce. The corresponding responses in ion temperature, ionospheric electron density, and total electron content have also been reported during the same period. In 1974, a significant 13.5 day periodicity in geomagnetic activity was created by the quasiperiodic HSS associated with two major solar coronal hole regions separated by about 180°. In the present paper, ionospheric F-region peak plasma density (NmF2) and height (hmF2) in the daytime and nighttime from 12 ionosonde stations are analyzed to delineate the responses to this epoch of HSS forcing of the geospace system. Results show that the ionospheric responses to this 13.5 day periodic forcing are similar in some ways to responses to the 9 day periodicity. For instance, in middle and high latitudes, daytime and nighttime NmF2 is mostly out of phase with the fluctuations in the daily mean Kp index (Kp¯), while the daytime hmF2 are in phase with the Kp¯ fluctuations. Empirical model results confirm the important role of thermal expansion in connecting thermospheric and ionospheric changes driven by high-speed streams and recurrent geomagnetic activity. At low latitudes, the 13.5 day signatures are not as straightforward as those at middle and high latitudes, and significant spectral energy thought to be connected with planetary waves and perhaps other lower-atmosphere influences exists at periods of less than 13.5 days.

  11. 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.

  12. Rederivation of Dst Index

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.

    2005-12-01

    Derivation of the Dst geomagnetic index involves removing the quiet diurnal variation (Sq) caused by thermal winds and tides in the ionosphere maintained by solar EUV radiation. The standard procedure has been to fit average, smoothed curves to the Sq computed from the five internationally quietest days of each month and to use these curves on all days to remove Sq from the observed values of the horizontal component of the geomagnetic field for three stations in the northern hemsphere and one station in the southern hemisphere, then to average the resulting values (weigthed by latitude) into a global Dst index. This procedure is problematic because 1) the day-to-day variability of the regular diurnal variation (Sr) is as large as the variation itself and 2) an annual variation of the level of horizontal component is not properly compensated for by using an unequal number of northern and southern stations. We show how these problems can be avoided by using only nighttime values and by using an equal number of stations in both hemispheres and calculate a new index Dsv back to 1930 (potentially back to 1900 or beyond). Using this new index, the long-term trend, semiannual variation, and average storm signature (superposed epoch around SSCs) are studied.

  13. 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.

  14. INFLUENCE OF INTERPLANETARY MAGNETIC FIELD AND PLASMA ON GEOMAGNETIC ACTIVITY DURING QUIET-SUN CONDITIONS

    Microsoft Academic Search

    John M. Wilcox; Kenneth H. Schatten; Norman F. Ness

    1967-01-01

    Observations by the IMP 1 satellite of the interplanetary magnetic field and plasma have been compared with the 3-hour geomagnetic activity index K. The average Kis approximately a linear function of the interplanetary field magnitude B in gammas (i -- (0.33 =k 0.02)B =k 0.2). It appears significant that this relation betweenand field magnitude passes through the origin, whereas the

  15. Geomagnetic navigation reference map preparation and statistical analysis

    NASA Astrophysics Data System (ADS)

    Wu, Meng; Ma, Jie; Tian, Jin Wen

    2009-10-01

    Geomagnetic field is the basic physics field of the Earth, which can't be destroyed or changed in the foreseeable future. Geomagnetic field don't require special service, therefore, it can be considered as a solid source of navigation information. The key technologies of geomagnetic navigation are still looking for high accuracy mapping and high accuracy geomagnetic field measurement on board aircraft, The article analyses some kinds of geomagnetic models. according to the character of the geomagnetic models, The NGDC-720 model is used as reference map preparation. The model with Kriging method give birth to the reference maps which include geomagnetic seven vectors' map (X, Y, Z, F, D, I, H). Using the reference maps, The geomagnetic vectors'statistical characters have been analyzed. According to the statistical characters, some changeable obviously statistical characters can be used as matching characteristic values.

  16. Modeling of Ionosphere Effects of Geomagnetic Storm Sequence on September 9-14, 2005 in View of Solar Flares and Dependence of Model Input Parameters from AE-and Kp-indices

    NASA Astrophysics Data System (ADS)

    Klimenko, Maxim; Klimenko, Vladimir; Ratovsky, Konstantin; Goncharenko, Larisa

    Earlier by Klimenko et al., 2009 under carrying out the calculations of the ionospheric effects of storm sequence on September 9-14, 2005 the model input parameters (potential difference through polar caps, field-aligned currents of the second region and particle precipitation fluxes and energy) were set as function of Kp-index of geomagnetic activity. The analyses of obtained results show that the reasons of quantitative distinctions of calculation results and observations can be: the use of 3 hour Kp-index at the setting of time dependence of model input parameters; the dipole approach of geomagnetic field; the absence in model calculations the effects of the solar flares, which were taken place during the considered period. In the given study the model input parameters were set as function of AE-and Kp-indices of geomagnetic activity according to different empirical models and morphological representations Feshchenko and Maltsev, 2003; Cheng et al., 2008; Zhang and Paxton, 2008. At that, we taken into account the shift of field-aligned currents of the second region to the lower latitudes as by Sojka et al., 1994 and 30 min. time delay of variations of the field-aligned currents of second region relative to the variations of the potential difference through polar caps at the storm sudden commencement phase. Also we taken into account the ionospheric effects of solar flares. Calculation of ionospheric effects of storm sequence has been carried out with use of the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) developed in WD IZMIRAN (Nam-galadze et al., 1988). We carried out the comparison of calculation results with experimental data. This study is supported by RFBR grant 08-05-00274. References Cheng Z.W., Shi J.K., Zhang T.L., Dunlop M. and Liu Z.X. Relationship between FAC at plasma sheet boundary layers and AE index during storms from August to October, 2001. Sci. China Ser. E-Tech. Sci., 2008, Vol. 51, No. 7, 842-848. Feshchenko E.Yu., Maltsev Yu.P. Relations of the polar cap voltage to the geophysical activity. Physics of Auroral Phenomena: XXVI Annual Seminar (February 25-28, 2003): Proc./PGI KSC RAS. Apatity, 2003, 59-61. Klimenko M.V., Klimenko V.V., Ratovsky K.G., and Goncharenko L.P. Numerical modeling of ionospheric parameters during sequence of geomagnetic storms on September 9-14, 2005. Physics of Auroral Phenomena: XXXII Annual Seminar (March 3-6, 2009): Proc./PGI KSC RAS. Apatity, 2009, 162-165. Namgaladze A.A., Korenkov Yu.N., Klimenko V.V., Karpov I.V., Bessarab F.S., Surotkin V.A., Glushenko T.A., Naumova N.M. Global model of the thermosphere-ionosphere-protonosphere system. Pure and Applied Geophysics (PAGEOPH), 1988, Vol. 127, No. 2/3, 219-254. Sojka J.J., Schunk R.W., Denig W.F. Ionospheric response to the sustained high geomagnetic activity during the March '89 great storm. J. Geophys. Res., 1994, Vol. 99, No. A11, 21341-21352. Zhang Y., Paxton L.J. An empirical Kp-dependent global auroral model based on TIMED/GUVI FUV data. J. Atmos. Solar-Terr. Phys., 2008, Vol. 70, 1231-1242.

  17. 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.

  18. Ergodic property of the recent geomagnetic field

    NASA Astrophysics Data System (ADS)

    Qamili, E.; De Santis, A.; Cianchini, G.

    2012-04-01

    The study of the geomagnetic field allows us to understand the peculiar processes of Earth's interior, which act in the outer core and produce the main field. To know whether the field is ergodic, i.e. time averages are equivalent to phase space averages, is an important question since, if this were true, it will be a further evidence for the strong spatio-temporal coupling among the contributions composing the dynamical system that produces and maintains the geomagnetic field. Another consequence would be that many computations, usually undertaken with many difficulties in the phase space, could be made in the conventional time domain. Here, we show the exponential temporal divergence of the errors between several couples of predictive (IGRF and WMM) - definitive (CM4 and POMME) global geomagnetic models from 1965 to 2010, confirming the present state of a chaotic geomagnetic field with no reliable prediction after around 6 years. Also going back in time (using GUFM1 model) we found the same results. These analyses establish the ergodicity of the field and could be used to improve the representation of the geomagnetic field with more detailed secular variation and acceleration.

  19. Multiday thermospheric density oscillations associated with variations in solar radiation and geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Xu, Jiyao; Wang, Wenbin; Zhang, Shunrong; Liu, Xiao; Yuan, Wei

    2015-05-01

    Thermospheric densities observed by Challenging Minisatellite Payload and Gravity Recovery and Climate Experiment satellites during 2002-2010 and the globally averaged thermospheric densities from 1967 to 2007 have been used to investigate latitudinal, longitudinal, and height dependences of the multiday oscillations of thermospheric densities. The data show that the main multiday oscillations in thermospheric densities are 27, 13.5, 9, and 7 day oscillations. The high-correlation coefficients between the density oscillations and the F10.7 or Ap index indicate that these oscillations are externally driven. The 27 day density oscillation, being the strongest, is induced by variations in solar radiation, as well as recurrent geomagnetic activity that is the result of corotating interaction regions (CIRs) and high-speed solar wind streams of coronal hole origin. Density oscillations at periods of 13.5, 9, and 7 days at solar minimum and during the declining phase are stronger than those at solar maximum. These oscillations are mainly associated with recurrent geomagnetic activity due to coronal hole high-speed streams and CIRs. The multiday, periodic oscillations of thermospheric density exhibit strong latitudinal and longitudinal variations in the geomagnetic coordinate and oscillate synchronously at different heights. Oscillations with zonal wave number 0 oscillate globally, whereas those with nonzero wave numbers are strong at high geomagnetic latitudes, and hemispherically asymmetric. They are stronger in the Southern Hemisphere. The spectral distributions of thermospheric densities at different heights have almost the same latitude and longitude structures, but the spectral magnitudes increase with height.

  20. Estimation of geomagnetically induced current levels from different input data

    Microsoft Academic Search

    Antti Pulkkinen; Ari Viljanen; Risto Pirjola

    2006-01-01

    Pragmatic schemes for estimating geomagnetically induced current (GIC) values using different levels of knowledge about the physical quantities associated with the geomagnetic induction process are studied. The fundamental idea behind the proposed schemes is that as the knowledge about the detailed behavior of the relevant physical quantities decreases, the lack of knowledge is compensated by statistical characteristics of the geomagnetic

  1. Determination of the Croatian geomagnetic observatory location

    NASA Astrophysics Data System (ADS)

    Verbanac, Giuliana; Vuji?, Eugen

    2012-04-01

    Ground survey within the Nature Park Lonjsko Polje, placed in the middle-northern Croatia was performed during the time interval 2007-2010 in order to find the best location for installing the geomagnetic observatory. The total magnetic field has been measured a few times using the Overhauser proton magnetometers. The horizontal and vertical gradients of the total field, and its temporal behaviour were investigated over the restricted region that we estimated as suitable for the observatory. The results obtained from thoroughly conducted measurements allowed us to find definitive positions for the instrument pillars. These results are in agreement with previously suggested location found based on combination of Comprehensive CM4 model prediction and measurements conducted from 2003 to 2005. This study contributes to the development of geomagnetism in Croatia and paves a way to install the first geomagnetic observatory in Croatia.

  2. 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.

  3. 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.

  4. Geomagnetic storm fields near a synchronous satellite.

    NASA Technical Reports Server (NTRS)

    Kawasaki, K.; Akasofu, S. I.

    1971-01-01

    An apparent early recovery of the main phase of geomagnetic storms at the distance of the synchronous satellite is examined in terms of changing electric current distributions in the magnetosphere during magnetic storms. It is suggested that a rapid recession of the edge of the plasma sheet (after the advance toward the earth during an early epoch of the main phase) is partly responsible for the early recovery. Relevant plasma sheet variations during geomagnetic storms are found to be in agreement with the inferred variations.

  5. 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.

  6. 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.

  7. 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.

  8. INSTRUCTION MANUAL MODEL AA-2010

    E-print Network

    Bayindir, Mehmet

    INSTRUCTION MANUAL . MODEL AA-2010 MODEL AA-2015 MODEL AA-2020 MODEL AA-2025 SINGLE CHANNEL NUCLEAR of the interaction of nuclear radiations with matter: The photo electric effect, in which all the energy of the gamma in a three unit assembly: detector, amplifier-analyzer, and scaler. Specifically, these units are: the Model

  9. Nonlinear Behavior of the Geomagnetic Fluctuations Recorded in Different Geomagnetic Latitudes

    NASA Astrophysics Data System (ADS)

    Kovacs, P.; Heilig, B.; Koppan, A.; Vadasz, G.; Echim, M.

    2014-12-01

    The paper concerns with the nonlinear properties of geomagnetic variations recorded in different geomagnetic latitudes, in the years of solar maximum and minimum. For the study, we use the geomagnetic time-series recorded by some of the stations of the EMMA quasi-meridional magnetometer network, established for pulsation study, in September 2001. The stations are located approx. along the magnetic meridian of 100 degree, and the sampling frequency of the series is 1 Hz. It is argued that the geomagnetic field exhibits nonlinear intermittent fluctuations in certain temporal scale range. For quantitatively investigating the scaling ranges and the variation of intermittent properties with latitude and time, we analyse the higher order moments of the time records (probability density function or structure function analyses). The multifractal or self-similar scaling of the fluctuations is investigated via the fitting of the P model to structure function scaling exponents. We also study the power-law behaviour of the power-spectral density functions of the series in order to evaluate the possible inertial frequency (and temporal) range of the geomagnetic field and compare them with the scaling ranges of structure functions. The range where intermittent geomagnetic variation is found falls typically between 100 and 20.000 s, i.e. covers the temporal range of the main phases of geomagnetic storms. It is shown that the intensity of intermittent fluctuations increases from solar minimum to solar maximum. The expected increase in the level of intermittency with the geomagnetic latitude can be evidenced only in the years of solar minimum. The research leading to these results has received funding from the European Community's Seventh Framework Programme ([FP7/2007-2013]) under grant agreement n° 313038/STORM.

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

    PubMed

    Messner, T; Häggström, 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

  11. 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.

  12. 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).

  13. Geomagnetic reversals from impacts on the Earth

    Microsoft Academic Search

    Richard A. Muller; Donald E. Morris

    1986-01-01

    The impact of a large extraterrestrial object on the Earth can produce a geomagnetic reversal through the following mechanism: dust from the impact crater and soot from fires trigger a climate change and the beginning of a little ice age. The redistribution of water near the equator to ice at high latitudes alters the rotation rate of the crust and

  14. Geomagnetic effects on the average surface temperature

    Microsoft Academic Search

    P. Ballatore

    2004-01-01

    Several results have previously shown as the solar activity can be related to the cloudiness and the surface solar radiation intensity (Svensmark and Friis-Christensen, J. Atmos. Sol. Terr. Phys., 59, 1225, 1997; Veretenenkoand Pudovkin, J. Atmos. Sol. Terr. Phys., 61, 521, 1999). Here, the possible relationships between the averaged surface temperature and the solar wind parameters or geomagnetic activity indices

  15. Geomagnetic referencing in the arctic environment

    USGS Publications Warehouse

    Podjono, Benny; Beck, Nathan; Buchanan, Andrew; Brink, Jason; Longo, Joseph; Finn, Carol A.; Worthington, E. William

    2011-01-01

    Geomagnetic referencing is becoming an increasingly attractive alternative to north-seeking gyroscopic surveys to achieve the precise wellbore positioning essential for success in today's complex drilling programs. However, the greater magnitude of variations in the geomagnetic environment at higher latitudes makes the application of geomagnetic referencing in those areas more challenging. Precise, real-time data on those variations from relatively nearby magnetic observatories can be crucial to achieving the required accuracy, but constructing and operating an observatory in these often harsh environments poses a number of significant challenges. Operational since March 2010, the Deadhorse Magnetic Observatory (DED), located in Deadhorse, Alaska, was created through collaboration between the United States Geological Survey (USGS) and a leading oilfield services supply company. DED was designed to produce real-time geomagnetic data at the required level of accuracy, and to do so reliably under the extreme temperatures and harsh weather conditions often experienced in the area. The observatory will serve a number of key scientific communities as well as the oilfield drilling industry, and has already played a vital role in the success of several commercial ventures in the area, providing essential, accurate data while offering significant cost and time savings, compared with traditional surveying techniques.

  16. Long-term changes in indices of geomagnetic activity at the auroral station Sodankylä

    NASA Astrophysics Data System (ADS)

    Martini, D.; Mursula, K.; Ulich, T.; Pandey, V. S.; Kim, K.-H.; Lee, D.-H.

    2012-09-01

    Here we compare the traditional analog measure of geomagnetic activity, Ak, with the more recent digital indices of IHV and Ah based on hourly mean data, and their derivatives at the auroral station Sodankylä. By this selection of indices we study the effects of (i) analog vs. digital technique, and (ii) full local-time vs. local night-time coverage on quantifying local geomagnetic activity. We find that all other indices are stronger than Ak during the low-activity cycles 15-16 suggesting an excess of very low scalings in Ak at this time. The full-day indices consistently depict stronger correlation with the interplanetary magnetic field strength, while the night-time indices have higher correlation with solar wind speed. The Ak index correlates better with the digital indices of full-day coverage than with any night-time index. However, Ak depicts somewhat higher activity levels than the digital full-day indices in the declining phase of the solar cycle, indicating that, due to their different sampling rates, the latter indices are less sensitive to high-frequency variations driven by the Alfvén waves in high-speed streams. On the other hand, the night-time indices have an even stronger response to solar wind speed than Ak. The results strongly indicate that at auroral latitudes, geomagnetic indices with different local time coverage reflect different current systems, which, by an appropriate choice of indices, allows studying the century-scale dynamics of these currents separately.

  17. 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 (34°25 S; 19°13 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Visualization of geomagnetic field for education and outreach

    NASA Astrophysics Data System (ADS)

    Hatakeyama, T.

    2010-12-01

    Since April 2007 in the project "MAGE" (Mapping Applications to Geomagnetic Environments) we publish tools for visualization of the geomagnetic field on the web. Now five kinds of the geomagnetic field flucuation (from observations and paleomagnetic results) and geodynamo models are freely downloadable from our website, http://mage-p.org/. Access the webpage, download the KML files and open them from Google Earth, then you can experience changing geomagnetic field lines and observations, inclinations, declination, field strength and others, on the Earth's surface. One of our actions in the project is preparation of the documentations of the geomagnetic field and its fluctuations for education and outreach. Especially in Japan, there are poor treatments in the education during elementary and high schools, and the expository writing of the geomagnetic field and concerned articles are also scarce. Moreover, we provide the movie files and stereoscopic visions for the user experiences of the 3D images.

  3. Isolated sleep paralysis, vivid dreams and geomagnetic influences: II.

    PubMed

    Conesa, J

    1997-10-01

    This report describes a test of the hypothesis that significant changes in the ambient geomagnetic field are associated with altered normal nighttime dream patterns. Specifically, it was predicted that there would be a greater incidence of isolated sleep, paralysis or vivid dreams with abrupt rises and falls of geomagnetic activity. The author's (JC) and a second subject's (KC) daily reports of dream-recall were analyzed in the context of daily fluctuations of geomagnetic activity (K indices). Two analyses of variance indicated (i) significantly higher geomagnetic activity three days before a recorded isolated sleep paralysis event and (ii) significantly lower geomagnetic activity three days before an unusually vivid dream took place. Conversely, geomagnetic activity did not fluctuate significantly for randomly selected days. Testing a large sample over time is required for confirmation and extension of this work. PMID:9347546

  4. Trapping of strangelets in the geomagnetic field

    SciTech Connect

    Paulucci, L.; Horvath, J. E.; Medina-Tanco, G. A. [Instituto de Fisica-Universidade de Sao Paulo, Rua do Matao, Travessa R, 187, 05508-090, Cidade Universitaria, Sao Paulo SP (Brazil); Instituto de Astronomia, Geofisica e Ciencias Atmosfericas-Universidade de Sao Paulo, Rua do Matao, 1226, 05508-900, Cidade Universitaria, Sao Paulo SP (Brazil); Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico A.P. 70-543, C.U. Mexico D.F. (Mexico)

    2008-02-15

    Strangelets arriving from the interstellar medium are an interesting target for experiments searching for evidence of this hypothetical state of hadronic matter. We entertain the possibility of a trapped strangelet population, quite analogous to ordinary nuclei and electron belts. For a population of strangelets to be trapped by the geomagnetic field, these incoming particles would have to fulfill certain conditions, namely, having magnetic rigidities above the geomagnetic cutoff and below a certain threshold for adiabatic motion to hold. We show in this work that, for fully ionized strangelets, there is a narrow window for stable trapping. An estimate of the stationary population is presented and the dominant loss mechanisms discussed. It is shown that the population would be substantially enhanced with respect to the interstellar medium flux (up to 2 orders of magnitude) due to quasistable trapping.

  5. Planetary waves during a moderate geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Demissie, T.; Daae, M.; Kleinknecht, N.; Espy, P.

    2012-04-01

    Nightly averaged measurements of the ozone mixing ratio profile obtained from Troll station (72° 1'S, 2° 32'E) in Antarctica have been used to investigate the presence and vertical profile of the 2-day planetary wave in stratosphere and mesosphere (40 to 80 km) during a moderate geomagnetic storm in July 2009. Nightly averaged mesospheric temperature derived from the hydroxyl nightglow at Rothera station (67° 34'S, 68° 08'W) are used to extend the wave identification up to 87 km. The variations of planetary waves with the changes in ozone mixing ratio and temperature are discussed, and the phase and amplitude variation of the 2-day wave before, during and after the moderate geomagnetic storm will be presented.

  6. 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.

  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. Complex classification of global geomagnetic disturbances

    Microsoft Academic Search

    N. A. Barkhatov; A. E. Levitin; S. E. Revunov

    2006-01-01

    Based on the Kohonen algorithm, a self-training neural network is constructed which allows one to classify geomagnetic disturbances\\u000a using the data on parameters of the solar wind and interplanetary magnetic field. Such an approach permits one to consider\\u000a the suggested classification simultaneously as space and physical, since the space origin of disturbances of different kinds\\u000a is considered within the framework

  9. Ground observations of chorus following geomagnetic storms

    Microsoft Academic Search

    A. J. Smith; R. B. Horne; N. P. Meredith

    2004-01-01

    It has been suggested that whistler mode chorus waves play a role in acceleration and loss of radiation belt electrons during geomagnetic storms. In this paper we present data from a complete solar cycle (1992–2002) of nearly continuous (>95%) VLF\\/ELF observations from the VLF\\/ELF Logger Experiment (VELOX) instrument at Halley station, Antarctica (76°S, 27°W, L = 4.3), to determine whether

  10. Power spectrum analysis of geomagnetic indices

    Microsoft Academic Search

    R P Kane

    1986-01-01

    Using the method of maximum entropy spectral analysis (MESA) by Burg and the least-squares linear prediction (lslp) (also calledFABNE) by Barrodale and Erickson, the spectra of geomagnetic indices Ap, AN, AS, AE, AU, AL, Dst and cosmic ray neutron intensity\\u000a at Deep River are obtained for 1965 and 1969 from daily means and for longer periods from monthly means. A

  11. Long-lived geomagnetic storms and coronal mass ejections

    Microsoft Academic Search

    H. Xie; N. Gopalswamy; P. K. Manoharan; A. Lara; S. Yashiro; S. Lepri

    2006-01-01

    Coronal mass ejections (CMEs) are major solar events that are known to cause large geomagnetic storms (Dst < ?100 nT). Isolated geomagnetic storms typically have a main phase of 3–12 hours and a recovery phase of around 1 day. However, there are some storms with main and recovery phases exceeding ?3 days. We trace the origin of these long-lived geomagnetic

  12. Wavelet-based index of magnetic storm activity P. Kokoszka,1

    E-print Network

    Kokoszka, Piotr

    Wavelet-based index of magnetic storm activity A. Jach,1 P. Kokoszka,1 J. Sojka,2 and L. Zhu2] A wavelet-based method of computing an index of storm activity is put forward. The new index can be computed of geomagnetic storm events and requires only the most recent magnetogram records, e.g., the 2 months including

  13. 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

  14. 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..

  15. Effects of thermosphere total density perturbations on a LEO orbit during severe geomagnetic conditions (oct - nov 2003) using DORIS and SLR data

    Microsoft Academic Search

    P. Willis; F. Deleflie; F. Barlier; Y. E. Bar-Sever; L. J. Romans

    2004-01-01

    We are now indeed in the descending phase of the solar cycle with its previous maximum in 2000. However, an exceptional solar activity event occurred at the end of October 2003. On October 29th, seven groups of solar spots were visible on the Sun surface and the geomagnetic index Kp reaches the extreme value of 9 leading to beautiful auroras.

  16. Origins of the semiannual variation of geomagnetic activity in 1954 and 1996

    NASA Astrophysics Data System (ADS)

    Cliver, E.; Svalgaard, L.; Ling, A.

    2004-01-01

    . We investigate the cause of the unusually strong semiannual variation of geomagnetic activity observed in the solar minimum years of 1954 and 1996. For 1996 we separate the contributions of the three classical modulation mechanisms (axial, equinoctial, and Russell-McPherron) to the six-month wave in the index and find that all three contribute about equally. This is in contrast to the longer run of geomagnetic activity (1868-1998) over which the equinoctial effect accounts for 70% of the semiannual variation. For both 1954 and 1996, we show that the Russell-McPherron effect was enhanced by the Rosenberg-Coleman effect (an axial polarity effect) which increased the amount of the negative (toward Sun) [positive (away from Sun)] polarity field observed during the first [second] half of the year; such fields yield a southward component in GSM coordinates. Because this favourable condition occurs only for alternate solar cycles, the marked semiannual variation in 1954 and 1996 is a manifestation of the 22-year cycle of geomagnetic activity. The 11-year evolution of the heliospheric current sheet (HCS) also contributes to the strong six-month wave during these years. At solar minimum, the streamer belt at the base of the HCS is located near the solar equator, permitting easier access to high speed streams from polar coronal holes when the Earth is at its highest heliographic latitudes in March and September. Such an axial variation in solar wind speed was observed for 1996 and is inferred for 1954.

  17. 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.

  18. Modeling Ionospheric Convection During a Major Geomagnetic Storm on October 22-23, 1981

    NASA Technical Reports Server (NTRS)

    Moses, J. J.; Slavin, J. A.; Aggson, T. L.; Heelis, R. A.; Winningham, J. D.

    1994-01-01

    Following the passage of an interplanetary shock at approximately 0500 UT, a major geomagnetic storm developed on October 22-23, 1981. Numerous auroral substorms occurred during this storm leading to an AE index greater than 1000 nT. We have used the expanding/contracting polar cap (ECPC) model (Moses et al., 1989) and data from the Dynamics Explorer 2 spacecraft to study the ionospheric electric fields for 12 consecutive traversals of the polar regions. The ECPC model can determine the voltage drops across the dayside merging and nightside reconnection gaps. We determined the relationship of the AL index (i.e., the intensity of the westward electrojet) to the nightside reconnection potential drop. An excellent linear correlation was found between the nightside reconnection gap voltage drop and the AL index. These results show that the solar wind strongly drives the magnetosphere-ionosphere system throughout the geomagnetic storm. A substantial level of dayside merging seems to occur throughout the event. Nightside reconnection varies from satellite pass to satellite pass and within the substorm recovery phase. We find that tail reconnection is an important feature of the recovery phase of substorms.

  19. 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

  20. On the scaling features of high-latitude geomagnetic field fluctuations during a large geomagnetic storm

    NASA Astrophysics Data System (ADS)

    De Michelis, Paola; Federica Marcucci, Maria; Consolini, Giuseppe

    2015-04-01

    Recently we have investigated the spatial distribution of the scaling features of short-time scale magnetic field fluctuations using measurements from several ground-based geomagnetic observatories distributed in the northern hemisphere. We have found that the scaling features of fluctuations of the horizontal magnetic field component at time scales below 100 minutes are correlated with the geomagnetic activity level and with changes in the currents flowing in the ionosphere. Here, we present a detailed analysis of the dynamical changes of the magnetic field scaling features as a function of the geomagnetic activity level during the well-known large geomagnetic storm occurred on July, 15, 2000 (the Bastille event). The observed dynamical changes are discussed in relationship with the changes of the overall ionospheric polar convection and potential structure as reconstructed using SuperDARN data. This work is supported by the Italian National Program for Antarctic Research (PNRA) - Research Project 2013/AC3.08 and by the European Community's Seventh Framework Programme ([FP7/2007-2013]) under Grant no. 313038/STORM and

  1. Improved dynamic geomagnetic rigidity cutoff modeling: Testing predictive accuracy

    Microsoft Academic Search

    Mark A. Clilverd; Craig J. Rodger; Tracy Moffat-Griffin; Pekka T. Verronen

    2007-01-01

    In the polar atmosphere, significant chemical and ionization changes occur during solar proton events (SPEs). The access of solar protons to this region is limited by the dynamically changing geomagnetic field. In this study, we have used riometer absorption observations to investigate the accuracy of a model to predict Kp-dependent geomagnetic rigidity cutoffs, and hence the changing proton fluxes. The

  2. Improved dynamic geomagnetic rigidity cutoff modeling: Testing predictive accuracy

    Microsoft Academic Search

    Mark A. Clilverd; Craig J. Rodger; Tracy Moffat-Griffin; Pekka T. Verronen

    2007-01-01

    In the polar atmosphere, significant chemical and ionization changes occur during solar proton events (SPEs). The access of solar protons to this region is limited by the dynamically changing geomagnetic field. In this study, we have used riometer absorption observations to investigate the accuracy of a model to predict K p-dependent geomagnetic rigidity cutoffs, and hence the changing proton fluxes.

  3. Solstitial and Hemispherical Asymmetry in the Response of Geomagnetic Field

    Microsoft Academic Search

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

    1984-01-01

    We show 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 three-month period around June solstice than in the interval around the December solstice. Further, an asymmetry

  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. Precursors of geomagnetic storms observed by the muon detector network

    Microsoft Academic Search

    Kazuoki Munakata; John W. Bieber; Shin-ichi Yasue; Chihiro Kato; Morikazu Koyama; Shigenobu Akahane; Kazuhiko Fujimoto; Zenjiro Fujii; John E. Humble; Marcus L. Duldig

    2000-01-01

    We report the first systematic survey of cosmic ray precursors of geomagnetic storms. Our data set comprises the 14 ``major'' geomagnetic storms (peak Kp>=8-) identified by Gosling et al. [1990] together with 25 large storms (peak Kp>=7-) observed from 1992 through 1998. After eliminating events for which the muon detector network had poor coverage of the sunward interplanetary magnetic field

  6. Geomagnetically Induced Currents / Telluric Currents and Potential for Power

    E-print Network

    Schrijver, Karel

    Network Also Increases GIC Risk by 7 Times! #12;Geomagnetic Storms & Transformer Failures ­ Historic Trends IEEE Survey of GSU Transformer Failures #12;1989-1991 IEEE Survey of GSU Transformer Failures DataGeomagnetically Induced Currents / Telluric Currents and Potential for Power System Impacts from

  7. Gravitational dynamos and the low-frequency geomagnetic secular variation

    E-print Network

    Olson, Peter L.

    -frequency end of this range (9, 10), and a slow drift of the dipole moment amplitude defines the low to the geomagnetic field. The magnetic variability is driven by the Lorentz force and is characterized by an inverse drift, polarity reversals, and excursions. geodynamo geomagnetic polarity reversals gravitational dynamo

  8. Geomagnetic background events observed by Uhuru

    NASA Technical Reports Server (NTRS)

    Schwartz, D. A.

    1974-01-01

    Problems due to sporadic background events observed by Uhuru (Small Astronomy Satellite - A) do not compromise the study of discrete X-ray sources. Nevertheless, direct particle effects and auroral type X-ray events in the atmosphere may occasionally occur. Therefore, even on the geomagnetic equator, an experiment must be prepared to recognize and eliminate such events when the ultimate level of sensitivity is desired. The test equipment contained in the satellite and the orbital mechanics of Small Astronomy Satellite - A are described. The sporadic events which were observed by the satellite are analyzed.

  9. Imaging core flow from geomagnetic secular variation: Consequences for core-mantle interactions and geomagnetic dipole moment changes

    E-print Network

    Amit, Hagay

    and geomagnetic dipole moment changes by Hagay Amit A dissertation submitted to The Johns Hopkins University variation data, time-dependent core flow, and dipole moment time-evolution equations to identify mech- anisms of geomagnetic dipole moment change between 1895-1985. Meridional advection and radial magnetic

  10. Geomagnetically induced currents in the New Zealand power network

    NASA Astrophysics Data System (ADS)

    Marshall, R. A.; Dalzell, M.; Waters, C. L.; Goldthorpe, P.; Smith, E. A.

    2012-08-01

    Adverse space weather conditions have been shown to be directly responsible for faults within power networks at high latitudes. A number of studies have also shown space weather to impact power networks at lower latitudes, although most of these studies show increases in GIC activity within networks not directly related to hardware faults. This study examines a GIC event that occurred in New Zealand's South Island power network on 6th November 2001. A transformer failure that occurred during this day is shown to be associated with a change in the solar wind dynamic pressure of nearly 20 nPa. Measurements of GICs recorded on the neutral lines of transformers across the Transpower network during this event show good correlation with a GIC-index, a proxy for the geoelectric field that drives GIC. Comparison of this event with GIC activity observed in the Transpower network during large space weather storms such as the "2003 Halloween storm," suggests that solar wind shocks and associated geomagnetic sudden impulse (SI) events may be as hazardous to middle latitude power networks as GIC activity occurring during the main phase of large storms. Further, this study suggests that the latitudinal dependence of the impacts of SI events on power systems differs from that observed during large main phase storms. This study also highlights the importance of operating procedures for large space weather events, even at middle latitude locations.

  11. AAS Job Register

    NSDL National Science Digital Library

    The Job Register of the American Astronomical Society has been updated for the month of November. It provides a list of current fellowships, postdoctoral, assistant, and faculty positions, for the current and previous months. At the Website, the user will also find additional resources such as descriptions of resume services, in the Editorial section; a Web Submission Form for posting jobs; and information on the AAS Job Center.

  12. An assessment study of the wavelet-based index of magnetic storm activity (WISA) and its comparison to the Dst index

    E-print Network

    Kokoszka, Piotr

    of magnetic storm activity (WISA) and its comparison to the Dst index Zhonghua Xu a,Ã, Lie Zhu a , Jan Sojka: Geomagnetic indices Ring current Magnetic storms Wavelet transform a b s t r a c t A wavelet-based index of storm activity (WISA) has been recently developed [Jach, A., Kokoszka, P., Sojka, L., Zhu, L., 2006

  13. Geomagnetic control of polar mesosphere summer echoes

    NASA Astrophysics Data System (ADS)

    Bremer, J.; Hoffmann, P.; Hansen, T. L.

    2000-02-01

    Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E) from 1994 until 1997 polar mesosphere summer echoes (PMSE) have been investigated in dependence on geomagnetic K indices derived at the Auroral Observatory Tromsø (69.66°N, 18.94°E). During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR) of the radar results and the geomagnetic K indices could be detected with a maximum correlation near midnight. The correlation becomes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E) and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV variation, however, has no significant influence on the PMSE during the observation period.

  14. Maximum Coronal Mass Ejection Speed as an Indicator of Solar and Geomagnetic Activities

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

    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.

  15. 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.

  16. Geoeffectiveness of corotating interaction regions as measured by Dst index

    Microsoft Academic Search

    M. V. Alves; E. Echer; W. D. Gonzalez

    2006-01-01

    Corotating interaction regions (CIRs) are structures formed when high-speed solar wind streams overtake slow solar wind streams as they propagate outward. These structures produce regions of enhanced density and magnetic field strength in the solar wind near the ecliptic plane. In this paper, the geoeffectiveness of CIRs, as measured by the geomagnetic Dst index, is assessed during the solar wind

  17. Characteristics of precipitating energetic electron fluxes relative to the plasmapause during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Whittaker, Ian C.; Clilverd, Mark A.; Rodger, Craig J.

    2014-11-01

    In this study we investigate the link between precipitating electrons from the Van Allen radiation belts and the dynamical plasmapause. We consider electron precipitation observations from the Polar Orbiting Environmental Satellite (POES) constellation during geomagnetic storms. Superposed epoch analysis is performed on precipitating electron observations for the 13 year period of 1999 to 2012 in two magnetic local time (MLT) sectors, morning and afternoon. We assume that the precipitation is due to wave-particle interactions and our two MLT sectors focus on chorus (outside the plasmapause) and plasmaspheric hiss (inside the plasmapause) waves. We generate simple expressions based on the geomagnetic index, Dst, which reproduce the chorus-driven observations for the >30 keV precipitating electron flux magnitudes. Additionally, we find expressions for the fitted spectral index to describe the flux variation with energy, allowing a full energy reproduction as a function of distance from the plasmapause. The hiss-driven precipitating flux occurs inside the plasmapause but is independent of distance from the plasmapause. In the POES observations the hiss-induced electron precipitation is only detectable above the instrument noise in the >300 keV and P6 (>800 keV) channels of the flux detection instrument. We have derived expressions for the storm time variation in flux inside the plasmapause using Dst as a proxy. The observations show that there is little evidence for >800 keV electron precipitation occurring outside of the plasmapause, in the MLT sectors studied.

  18. 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.

  19. Trimpi occurrence and geomagnetic activity: Analysis of events detected at Comandante Ferraz Brazilian Antarctic Station (L = 2.25)

    NASA Astrophysics Data System (ADS)

    Fernandez, J. H.; Rizzo Piazza, L.; Kaufmann, P.

    2003-01-01

    We present an analysis of the occurrence of Trimpi events observed at Comandante Ferraz Brazilian Antarctic Station (EACF), at L = 2.25, as observed by the amplitude of very low frequency (VLF) signals transmitted from Hawaii (NPM 21.4 kHz) from April 1996 to August 1999. The event parameters (total duration, amplitude variation, time incidence, and type (negative or positive)) were analyzed for 4394 events detected in the first year (solar minimum and relatively low Trimpi activity). The Trimpi occurrence was compared with geomagnetic activity for the whole period. A higher incidence of Trimpi events was observed near the equinoxes, with minima at the solstices following the same behavior as the Ap indices annual variation. During the day, their incidence peaked at ˜0700 and ˜1045 UT in accordance with the occurrence of lightning flashes in the geomagnetic conjugate regions but apparently not in agreement to the daily mean geomagnetic variation (Kp index) found to be peaked (in entire years sampling average) at 0300 UT and weaker at 0900 UT for the whole 4-year period. The relationship between Trimpi occurrence and rise in solar activity for cycle 23 is discussed. A sudden strong incidence of Trimpi events around 5 May 1998 and 27 August 1998 was attributed to pronounced magnetic storms (Dst index).

  20. 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

  1. Responses of the lower thermospheric temperature to the 9 day and 13.5 day oscillations of recurrent geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Jiang, Guoying; Wang, Wenbin; Xu, Jiyao; Yue, Jia; Burns, Alan G.; Lei, Jiuhou; Mlynczak, Martin G.; Rusell, James M.

    2014-06-01

    Responses of the lower thermospheric temperature to the 9 day and 13.5 day oscillations of recurrent geomagnetic activity and solar EUV radiation have been investigated using neutral temperature data observed by the TIMED/SABER (Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) instrument and numerical experiments by the NCAR-TIME-GCM (National Center for Atmospheric Research-thermosphere-ionosphere-mesosphere electrodynamics-general circulation model). The TIMED/SABER data analyzed were for the period from 2002 to 2007 during the declining phase of solar cycle 23. The observations show that the zonal mean temperature in the lower thermosphere oscillated with periods of near 9 and 13.5 days in the height range of 100-120 km. These oscillations were more strongly correlated with the recurrent geomagnetic activity than with the solar EUV variability of the same periods. The 9 day and 13.5 day oscillations of lower thermospheric temperature had greater amplitudes at high latitudes than at low latitudes; they also had larger amplitudes at higher altitudes, and the oscillations could penetrate down to ~105 km, depending on the strength of the recurrent geomagnetic activity for a particular time period. The data further show that the periodic responses of the lower thermospheric temperature to recurrent geomagnetic activity were different in the two hemispheres. In addition, numerical experiments have been carried out using the NCAR-TIME-GCM to investigate the causal relationship between the temperature oscillations and the geomagnetic activity and solar EUV variations of the same periods. Model simulations showed the same periodic oscillations as those seen in the observations when the real geomagnetic activity index, Kp, was used to drive the model. These numerical results show that recurrent geomagnetic activity is the main cause of the 9 day and 13.5 day variations in the lower thermosphere temperature, and the contribution from solar EUV variations is minor. Furthermore, we also found that consecutive coronal mass ejection events could cause long-duration enhancements in the lower thermospheric temperature that strengthen the 9 day and 13.5 day signals, and this kind of phenomenon mostly occurred between 2002 and 2005 during the declining phase of solar cycle 23.

  2. Responses of the lower thermospheric temperature to the 9 day and 13.5 day oscillations of recurrent geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Jiang, Guoying; Wang, Wenbin; Xu, Jiyao; Yue, Jia; Burns, Alan G.; Lei, Jiuhou; Mlynczak, Martin G.; Rusell, James M., III

    2015-04-01

    Responses of the lower thermospheric temperature to the 9 day and 13.5 day oscillations of recurrent geomagnetic activity and solar EUV radiation have been investigated using neutral temperature data observed by the TIMED/SABER (Thermosphere IonosphereMesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) instrument and numerical experiments by the NCAR-TIME-GCM (National Center for Atmospheric Research-thermosphere-ionosphere-mesosphere electrodynamics-general circulation model). The TIMED/SABER data analyzed were for the period from 2002 to 2007 during the declining phase of solar cycle 23. The observations show that the zonal mean temperature in the lower thermosphere oscillated with periods of near 9 and 13.5 days in the height range of 100-120 km. These oscillations were more strongly correlated with the recurrent geomagnetic activity than with the solar EUV variability of the same periods. The 9 day and 13.5 day oscillations of lower thermospheric temperature had greater amplitudes at high latitudes than at low latitudes; they also had larger amplitudes at higher altitudes, and the oscillations could penetrate down to ~105 km, depending on the strength of the recurrent geomagnetic activity for a particular time period. The data further show that the periodic responses of the lower thermospheric temperature to recurrent geomagnetic activity were different in the two hemispheres. In addition, numerical experiments have been carried out using the NCAR-TIME-GCM to investigate the causal relationship between the temperature oscillations and the geomagnetic activity and solar EUV variations of the same periods. Model simulations showed the same periodic oscillations as those seen in the observations when the real geomagnetic activity index, Kp, was used to drive the model. These numerical results show that recurrent geomagnetic activity is the main cause of the 9 day and 13.5 day variations in the lower thermosphere temperature, and the contribution from solar EUV variations is minor. Furthermore, we also found that consecutive coronal mass ejection events could cause long-duration enhancements in the lower thermospheric temperature that strengthen the 9 day and 13.5 day signals, and this kind of phenomenon mostly occurred between 2002 and 2005 during the declining phase of solar cycle 23.

  3. MMAASSTTEERR OOFF SSCCIIEENNCCEE GGRR AA DD UU AA TT EE PPRR OO GG RR AA MM II NN

    E-print Network

    Puglisi, Joseph

    MMAASSTTEERR OOFF SSCCIIEENNCCEE GGRR AA DD UU AA TT EE PPRR OO GG RR AA MM II NN EEPP II DD EE MM II OO LL OO GG YY SSTTAANNFFOORRDD UUNNIIVVEERRSSIITTYY IInnffoorrmmaattiioonn aanndd-Arnold #12;222 EE PP II DD EE MM II OO LL OO GG YY AA TT SS TT AA NN FF OO RR DD :: AA NN II NN TT RR OO DD

  4. MMAASSTTEERR OOFF SSCCIIEENNCCEE GGRR AA DD UU AA TT EE PPRR OO GG RR AA MM II NN

    E-print Network

    Puglisi, Joseph

    MMAASSTTEERR OOFF SSCCIIEENNCCEE GGRR AA DD UU AA TT EE PPRR OO GG RR AA MM II NN EEPP II DD EE MM II OO LL OO GG YY SSTTAANNFFOORRDD UUNNIIVVEERRSSIITTYY IINNFFOORRMMAATTIIOONN AANNDD. French-Arnold #12;3 EE PP II DD EE MM II OO LL OO GG YY AA TT SS TT AA NN FF OO RR DD :: AA NN II NN TT

  5. 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.

  6. Long-term seafloor geomagnetic station in the northwest Pacific: A possible candidate for a seafloor geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    Toh, H.; Hamano, Y.; Ichiki, M.

    2006-06-01

    For two years, geomagnetic variations have been measured at the seafloor in the northwest Pacific. The seafloor data consist of the geomagnetic vector field measured by a three-component fluxgate magnetometer and the absolute scalar total force measured by an Overhauser (1953) magnetometer with attitude measurements for both orientation and tilt. Using the attitude data, the geomagnetic data at a site in the northwest Pacific (41o06'08?N, 159°57'47?E, -5580 m), hereafter referred to as NWP, were converted into the same reference frame as land and satellite measurements. Short-period variations of the converted vector data were examined by Hamano's (2002) global time domain analysis method, which showed compatibility of the seafloor geomagnetic observatory data with the existing land observatory network. The smooth and gradual change of the Earth's main field (i.e., the geomagnetic secular variation) was also found consistent with those predicted by the latest International Geomagnetic Reference Field (IGRF-10; IAGA, 2005) and by Ørsted Satellite (Olsen, 2002) for not only the scalar field but also the vector field. This means that observation of the geomagnetic vector secular variation is now feasible on the seafloor.

  7. Major Geomagnetic Storms in Solar Cycle 24 and Challenges in Forecasting Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Zheng, Yihua

    2014-05-01

    Solar Cycle 24 has produced 11 major geomagnetic storms (where Dstmin < -100 nT) with three in 2011, six in 2012 and two in 2013 (as of 15 January 2014). Detailed analysis of each event will be given in terms of its solar driver(s): CME, coronal hole high speed solar wind stream (HSS), multiple CMEs or interactions between CME and HSS. While some of these storms are associated with a fast and wide CME, the several cases involving slow or common CMEs and interactions with HSS are particularly interesting. These events pose great challenges for accurate space weather forecasting, since operationally the slower or average CMEs tend to receive less attention and are sometimes overlooked altogether. In addition, cases (e.g., the CME associated with the X1.2 flare on 7 January 2014) where seemingly potent/geoeffective CMEs (fast and wide) result in yet weak geomagnetic disturbances will be presented. What has been done at CCMC/SWRC (http://ccmc.gsfc.nasa.gov and http://swrc.gsfc.nasa.gov) and multitude of challenges in geomagnetic storm forecasting will be discussed.

  8. AA PPENDIXPPENDIX II AA DDITIONALDDITIONAL II NSTRUCTIONNSTRUCTION PP IPELINEIPELINE

    E-print Network

    Smith, Marc L.

    AA PPENDIXPPENDIX II AA DDITIONALDDITIONAL II NSTRUCTIONNSTRUCTION PP IPELINEIPELINE TT OPICSOPICS]). A reservation table is a timing diagram that shows the flow of data through a pipeline and indicates which resources are needed at each time interval by an instruction flowing through the pipeline. Reservation

  9. A&AA Faculty & Student Services. Date: ______________

    E-print Network

    A&AA Faculty & Student Services. Date: ______________ Date: ______________ Office Use: ____________ Added to authorization list ____________ Printed updated list A&AA Faculty & Student Services. Date list A&AA Faculty & Student Services. Date: ______________ Date: ______________ Office Use

  10. Sunward Electric Current In The Geomagnetic Tail

    NASA Astrophysics Data System (ADS)

    Israelevich, P.; Ershkovich, A.; Tsyganenko, N.

    Analysis of Geotail magnetic data enables us to reveal the antisunward electric cur- rent flowing along the tail axis. Distributions of the magnetic field and electric current density (along with their dependencies on the tilt angle of the Earth's dipole and com- ponents of the interplanetary magnetic field) have been derived directly from Geotail data, without any ad hoc assumptions. Analysis of the electric current density distri- bution shows that, in addition to currents associated with the geomagnetic tail flaring, there is a current (tentatively identified as the Hall current) flowing antisunward along the tail axis. The total strength of this current is of the order of 1 MA. It closes through the midnight sector of the auroral zone resulting in field-aligned currents in the region of the Harang discontinuity.

  11. Protection against lightning on the geomagnetic observatory

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    The Sinji Vrh Geomagnetic Observatory was built on the brow of the mountain Gora, above Ajdovš?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.

  12. Historical records of the geomagnetic field

    NASA Astrophysics Data System (ADS)

    Arneitz, Patrick; Heilig, Balázs; Vadasz, Gergely; Valach, Fridrich; Dolinský, 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 Kremsmünster 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.

  13. Geomagnetism and paleomagnetism 1979-1983

    NASA Astrophysics Data System (ADS)

    Fuller, M.

    My function, in writing these notes, is to bring you up to date in Geomagnetism and Paleomagnetism, in as painless a manner as possible—without tears, as the French language texts for tourists used to promise. In writing this account of progress in the past quadrennium, I must first acknowledge that it is a personal and subjective viewpoint;; another reporter would surely emphasize other developments. Yet, there is some virture in writing of things, about which one knows something, so I leave to future reporters the task of redresssing the balance in matters covered.At the outset, one very sad event must be recorded. On April 3, 1981, Sir Edward Bullard died. His published work alone marks him as one of the leaders of geomagnetism in our times. Yet his contribution was much greater; many an American geophysicist, as well as a whole generation of British colleagues, have felt the benefit of his perceptive advice on their research. To those who saw him in the last few months of his life, his courage in the face of his illness was a remarkable example of fortitude. It is by now well known that the definitive paper, which he wrote with Malin, on secular variation at London, was only completed immediately before his death. The transmittal letter had been typed, but death prevented him from signing it. Bullard returned in this final paper to a topic to which he had contributed much. In it, he notes the role of Halley, who first described the phenomenon of westward drift, to which Bullard gave a new numerical precision, two and a half centuries later. I seem to remember Bullard saying in a lecture years ago that, while the Newtons of this world seem other than mortal, Halley was a scientist whose life and acheivements could encourage one's own efforts. Bullard, like Halley, inspires and encourages us.

  14. 77 FR 64935 - Reliability Standards for Geomagnetic Disturbances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-24

    ...outside nominal voltage design values, saturating the transformer core with magnetic flux...that, depending on the transformer health, design, geology and geomagnetic...approach that will include transformer design, condition,...

  15. The geomagnetic secularvariation timescale in observations and numerical dynamo models

    E-print Network

    Aubert, Julien

    Lhuillier,1 Alexandre Fournier,1 Gauthier Hulot,1 and Julien Aubert1 Received 3 March 2011; accepted 29. Fournier, G. Hulot, and J. Aubert (2011), The geomagnetic secularvariation timescale in observa- tions

  16. Magnetospheric Energy Input during Intense Geomagnetic Storms in SC23

    NASA Astrophysics Data System (ADS)

    Besliu-Ionescu, Diana; Maris Muntean, Georgeta; Dobrica, Venera; Mierla, Marilena

    2015-04-01

    Geomagnetic storm connections to solar eruptive phenomena in solar cycle 23 (SC23) have been intensively studied and it is a subject of great importance because of their various effects in our day-to-day life. We analyse the energy transfer from the solar wind into the magnetosphere during intense geomagnetic storms defined by Dst ? -150 nT. There were 29 intense storms during SC23. We will use the Akasofu parameter (Akasofu, 1981) to compute the ? function and study its time profile. We compute the energy input efficiency during the main phase of the geomagnetic storm. We compute the magnetospheric energy input using the formula introduced by Wang et al. (2014) and compare these results with the ? function for the geomagnetic storms of October 29-30, 2003.

  17. 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.

  18. Altitude Dependence of Neutral Density Geomagnetic Storm Response

    Microsoft Academic Search

    F. A. Marcos; C. Lin; M. Noah; W. J. Burke; S. B. Cable; J. O. Wise; E. K. Sutton

    2010-01-01

    New formulations for satellite neutral density response to geomagnetic activity developed for the Jacchia-Bowman 2008 empirical model were based on data at GRACE altitudes and are applicable for large geomagnetic storms (ap>75). Storm response from the Jacchia-Bowman 2008 and NRLMSIS empirical models are tested at low satellite altitudes using a unique historic set of accelerometer neutral density data from satellites

  19. Tsunami effects on the Z component of the geomagnetic field

    E-print Network

    Klausner, Virginia; Mendes, Odim; Papa, Andres R R

    2011-01-01

    The vertical component (Z) of the geomagnetic field observed by ground-based observatories of the INTERMAGNET network has been used to analyze the effects of the movement of electrically conducting sea water through the geomagnetic field due to a propagation of a tsumani. The purpose of this work is to study the geomagnetic variations induced by the tsunamis occurred at 26 December, 2004, 27 February, 2010 and 11 March, 2011. For each case study, we selected four magnetic stations belonging to the INTERMAGNET programme that were influenced or more direct affected by the tsumani. To detect these disturbances in the geomagnetic data, the discrete wavelet technique have been used in four levels of decomposition. We were able to detect the localized behavior of the geomagnetic variations induced by the movement of electrically conducting sea-water through the geomagnetic field, i. e., the identification of transients related to the tsunamis. As well, using the minutely magnetogram data, it was able to localize th...

  20. Some properties of the Svalgaard A/C index. [of polar cap magnetic variations

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Several properties of the A/C index of polar cap variations introduced by L. Svalgaard in 1972 have been found to vary with time. In the presatellite era, C days, as measured by the Ap index, are almost twice as geomagnetically active as A days, while in the modern epoch they have essentially identical activity. Prior to 1962 there were over 40% more A days than C days per year, while during the modern epoch there are essentially equal numbers of A days and C days. In view of this strong bias to assigning a 'toward' classification on geomagnetically active days it is recommended that the Svalgaard A/C classification not be used in studies of geomagnetic activity. It is also recommended that a full and thorough documentation of the index be prepared and/or that others undertake to compile such a classification separately.

  1. Discrete Scale Invariance in Geomagnetic Data

    NASA Astrophysics Data System (ADS)

    Jonkers, A.

    2005-12-01

    The geomagnetic field has recently been shown to exhibit scale-invariant features, most notably in terms of power laws, e.g., in power spectra and ranked intervals between dipole reversals. However, these scaling laws are merely a first approximation, leaving substantial residuals unexplained. With the aid of a novel technique (in principle applicable to any time series of sufficient length), additional information may be extracted that quantifies the characteristic scales of the studied process, that is, the preferred size(s) of the most important fluctuations and their associated timings. This so-called discrete scale invariance (DSI) betrays its presence by a logperiodic modulation of the underlying power law, and can be detected through a bootstrapping approach. Given an observed gamut of fluctuations over a studied period, a set of linearly incremental thresholds of absolute change is first defined, and the associated intervals between successive exceedances recorded, to be ranked by size on a log-log scale (thus yielding as many new datasets as there are thresholds). To all sets satisfying certain basic quality criteria, a power law fit is performed (negative gradient), and its residuals (unequally spaced on a log-scale) subjected to Lomb spectral analysis, which exploits this uneven spread. If a significant, coherent modulation is found, matrix inversion will yield the remaining wave parameters, and the associated topmost scaling stratum can then be identified as the highest point where the modulation intersects the power law from below. This level is stored with the set's (log-scaled) threshold, contributing to a meta-dataset that associates these preferred timings with their fluctuation threshold. After additional quality control of this set, a new power law fit is performed (positive gradient), and its residuals subjected to Lomb analysis and inversion. The resulting wave parameters yield the preferred scaling levels of the original observable and the associated timings. An additional feature of this approach is its potential predictive power above and below the observed range. Three independent geomagnetic datasets were examined to look for signatures of discrete scale invariance: the sequence of dipole reversal intervals from the Mesozoic to the present day (161-0 Ma, Gradstein & Ogg 1996); fluctuations in relative intensity over the last 2 Ma (SINT2000 dipole excursions, Valet, Meynadier & Guyodo 2005); and secular variation as captured by the historical field map gufm1 (1590-1990 A.D., Jackson, Jonkers & Walker 2000). Not only does each set exhibit significant DSI, but the recorded characteristic scales of both reversals and secular variation (individually) are quite well predicted by each of the other two datasets.

  2. Geomagnetic Field -- From Paleomagnetism to Dynamo Theory

    NASA Astrophysics Data System (ADS)

    Kono, M.

    2008-05-01

    Since 1995, self-consistent models of the geodynamo became available. There are certain problems, but some of these models have shown behaviors quite similar to those observed by paleomagnetism, including polarity reversals (Kono and Roberts, 2002). There is thus a hope that the combination of paleomagnetism and dynamo theory may provide us a very comprehensive understanding of the geomagnetic field. In this paper, I will try to highlight the possibilities and limitations in such studies. From satellite observations, it was shown that the power of the magnetic field contained in each degree is nearly the same if measured at the core-mantle boundary (CMB). The core field can be seen only to degree 13 or 14 where the field power is about (10 nT)2. Beyond that, the crustal magnetization dominates and the core signal is lost. The value of 10 nT is far larger than the accuracy of the present-day instruments, but much smaller than the resolution obtainable by paleomagnetic observations. We may safely assume that the error in paleomagnetic measurements (in direction) is of the order of 10 degrees. This error corresponds to the resolution of about 1/5. The relative powers of the low degree terms in the magnetic field at the surface are 1.0, 0.033, 0.019, 0.0055 (Langel and Estes, 1982). This means that only the degrees 1 to 3 terms may be distinguished by paleomagnetic data. From the combination of dipole, quadrupole, and octupole, what we can deduce about the fundamental properties of the geomagnetic field? Here are some of the possibilities, which may give important clues when we compare with dynamo simulation results. (1) The current dipole power is several times larger than the value expected from the trend line produced by degrees 2--13. Is this a persistent feature or transient? (2) In PSV analysis, the angular standard deviation increases with latitude. Kono and Tanaka (1995) showed that it is possible only if the (2,1) (degree, order) or (3,2) term is very large. But the present field does not show such features. What is the solution of this difference? (3) If the dynamo is very simple, the dynamo modes may be divided into two distinct groups (dipole family and quadrupole family) due to the selection rules (Roberts and Stix, 1972). McFadden et al. (1988) derived a paleosecular variation model based on this separation. Is it a real feature?

  3. Forecasting Dst index using CME expansion speed

    NASA Astrophysics Data System (ADS)

    Dal Lago, A.; Stekel, T. R. C.; Braga, C. R.; Vieira, L. E. A.; Balmaceda, L. A.; Rawat, R.; Echer, E.; Gonzalez, W. D.

    2014-12-01

    It is well known that solar eruptive phenomena, in particular coronal mass ejections (CMEs), their corresponding interplanetary counterparts (ICMEs) and driven shocks are the main origins of southward-directed Bz, which drive geomagnetic disturbances. The ability to predict geomagnetic storms, however, is still a big challenge because details on this Bz fields are difficult to be obtained with a lead time of tens of hours to days. If estimates of Bz and solar wind speed at 1AU are available, it is possible to derive the peak Disturbance Storm-Time Dst index using Burton et al. (1975) formula. Previous works have addressed empirical methods to obtain Bz from total magnetic field strength and solar wind velocity inside interplanetary magnetic clouds. Empirical estimates of ICME speeds at 1AU from CME speeds measured in coronagraphs have also been proposed. In this work, an attempt is made to forecast the geomagnetic Dst index using observations of coronal mass ejection (CME) expansion speed observed in coronagraphs. Only those cases in which a CME was associated with a magnetic cloud at 1 AU are addressed.

  4. Analisys of interplanetary structures associated with cosmic ray precursory anisotropies and intense geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Savian, J. F.; da Silva, M. R.; Signori, M. R.; Andrioli, V. F.; dal Lago, A.; Eduardo, L.; Vieira, A.; Munakata, K.; Gonzalez, W. D.; Schuch, N. J.

    Throughout the 11 year solar cycle a number of energetic phenomena such as "flares" and coronal mass ejections (CME) give rise at earth to the so-called magnetic storms. These storms are characterized by a decrease in the H component of terrestrial magnetic field, lasting some dozens of hours. They are associated to interplanetary structures whose interplanetary magnetic field component in the Z direction (Bz) is southward, i.e., antiparalell to the earth's magnetic field direction. Thus, the interplanetary magnetic field interconnects with the geomagnetic field causing energy to be transported inwards. Some of these structures are associated with precursory anisotropy observed in ground cosmic ray data (muons). The objective of this work is to use a set of intense geomagnetic storm events (Dst<-100nT), already studied by Munakata et al (2000) in terms of cosmic ray signatures, and identify their interplanetary structures using observations made by ACE, Wind and IMP-8 satellites. We use the following interplanetary data: plasma (solar wind speed , density and temperature of protons), interplanetary magnetic field (B, Bx, By, Bz), observed by IMP-8, WIND and ACE satellites, and Dst index from Kyoto to characterize the storms.

  5. Two-step forecast of geomagnetic storm using coronal mass ejection and solar wind condition

    NASA Astrophysics Data System (ADS)

    Kim, R.-S.; Moon, Y.-J.; Gopalswamy, N.; Park, Y.-D.; Kim, Y.-H.

    2014-04-01

    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.

  6. Equatorial Thermospheric Responses to Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Earle, G. D.; Davidson, R.; Heelis, R. A.; Coley, W. R.; Weimer, D. R.; Makela, J. J.; Fisher, D. J.

    2012-12-01

    Low latitude observations by the C/NOFS-CINDI satellite mission reveal marked neutral density enhancements commencing a few hours after the onset of geomagnetic storms. These perturbations are consistent with increases in atmospheric scale heights driven by thermospheric heating at altitudes below the C/NOFS observation height. The time lags between storm onsets and observed scale height increases near the equator are consistent with propagation times for traveling ionospheric disturbances (TIDs) from high to low latitudes. We examine several storms from fall 2011 and spring/summer 2012 and compare the gross features of thermospheric heating and perturbation winds that arise in each case. On average we find the density perturbations near 400 km altitude to be about 50% of the background, with perturbation winds near 150 m/s in the equatorward direction. These observations are in good agreement with empirical model predictions based on the CHAMP and GRACE missions. Simultaneous ground-based observations at lower altitudes are found to compare favorably to the in-situ measurements during storm periods.

  7. Injection boundary dynamics during a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Konradi, A.; Semar, C. L.; Fritz, T. A.

    1976-01-01

    A series of proton and electron injections were observed by Explorer 45 associated with several substorms during the main phase of the Feb. 24, 1972 geomagnetic storm. The 1- to 290-keV protons and 1- to 560-keV electrons were observed in the evening quadrant up to L of about 5.2. A model distorted dipole magnetic field and McIlwain's E3 convection electric field were used to backtrack the energy-dispersed electron and proton fluxes to their source at the time of injection. The source turns out to be a region extending over several earth radii outside an injection boundary. In the night magnetosphere, the inferred injection boundary is displaced inward with each successive substorm. The energy dispersion plot of the particles injected during orbit 314 indicates that as the energy of the observed particles decreases there is a smooth transition to the position of the plasmapause. This suggests that for that substorm the injection boundary and the plasmapause were one and the same. The proton 'noses' reported by Smith and Hoffman (1974) are discussed.

  8. Relativistic Electron Acceleration and Loss During Small Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Anderson, B.; Millan, R. M.; Reeves, G. D.; Friedel, R. H. W.

    2014-12-01

    Relativistic electron precipitation events were detected by early BARREL (Balloon Array for Radiation-belt Relativistic Electron Losses) payloads during small geomagnetic storms (minimum DST greater than -50nT), coincident with significant enhancement of relativistic electron fluxes at geosynchronous as measured by GOES. Such small geomagnetic storms have not been studied as in depth as larger storms, even though they are capable of pumping-up or depleting the radiation belts equally as extremely as their larger counterparts, this study finds. Since much of the past few years has been quiet, it is necessary to extend previous studies to include smaller storms. We perform a statistical analysis of relativistic electron flux response at geosynchronous to small geomagnetic storms over an 11 year period (1989-2000) using LANL satellite data, similar to previous studies of larger geomagnetic storms. We investigate changes in relativistic electron flux response with various solar wind parameters, as well as extend the statistical analysis of small and large geomagnetic storms with data sets now available from the Van Allen Probes.

  9. 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.

  10. Geomagnetically induced currents in a power grid of northeastern Spain

    NASA Astrophysics Data System (ADS)

    Torta, J. Miquel; Serrano, LluíS.; Regué, J. Ramon; SáNchez, Albert M.; RoldáN, Elionor

    2012-06-01

    Using the geomagnetic records of Ebro geomagnetic observatory and taking the plane wave assumption for the external current source and a homogeneous Earth conductivity, a prediction of the effects of the geomagnetic activity on the Catalonian (northeastern Spain) power transmission system has been developed. Although the area is located at midlatitudes, determination of the geoelectric field on the occasion of the largest geomagnetic storms during the last solar cycles indicates amplitudes that are higher than those recorded in southern Africa, where some transformer failures on large transmission systems have been reported. A DC network model of the grid has been constructed, and the geomagnetically induced current (GIC) flows in the power network have been calculated for such extreme events using the electric field at Ebro as a regional proxy. In addition, GICs have been measured at one transformer neutral earthing of the power grid, so that there the accuracy of the model has been assessed. Although the agreement is quite satisfactory, results indicate that better knowledge of the ground conductivity structure is needed. This represents the first attempt to study and measure GICs in southern European power grids, a region considered to have low GIC-risk up to the present.

  11. The solar and geomagnetic inputs into the JB2008 thermospheric density model for use by CIRA08 and ISO 14222

    NASA Astrophysics Data System (ADS)

    Tobiska, W. Kent

    Solar and geomagnetic indices are described for use in the Jacchia-Bowman 2008 thermospheric density model (JB2008). There are four solar and two geomagnetic indices used by JB2008. The F10.7, S10.7, M10.7, and Y10.7 solar indices are formed using the JB2006 methodology and they map energy from specific solar irradiance sources to major thermospheric layers. Energy that is deposited to the lower thermosphere and mesopause (85-100 km) is now provided. These solar proxies and indices are compliant with the ISO International Standard 21348 for determining solar irradiances. Reference values of the solar indices and proxies for short-term, intermediate-term, solar cycle, and 25-year periods from solar cycle 23 examples are provided for users who want reference values for planning and tests. The ap geomagnetic and Dst ring current indices are used in a two-index formulation that captures both low/unsettled activity and substorms/storms to represent changes to the neutral thermospheric densities as a result of high-latitude Joule heating and charged particle precipitation. The storm effects change the rate of exospheric temperature change, dTc, which affects satellite orbits. Reference values for ap, Dst, and dTc are provided using an example storm of November 20-21, 2003 for users who want reference values for planning and tests. Use of these solar, geomagnetic, and ring current indices in the JB2008 model produces significant improvements in empirical thermospheric density modeling. JB2008 provides standard deviations of approximately 9-10 percent at 400 km, which is a significant decrease from 16 percent 1-sigma uncertainty previously obtained using the Jacchia 70 model.

  12. In search of a new ULF wave index: Comparison of Pc5 power with dynamics of geostationary relativistic electrons

    Microsoft Academic Search

    O. Kozyreva; V. Pilipenko; M. J. Engebretson; K. Yumoto; J. Watermann; N. Romanova

    2007-01-01

    A new ULF wave index, characterizing the turbulent level of the geomagnetic field, has been calculated and applied to the analysis of relativistic electron enhancements during space weather events in March–May 1994 and September 1999. This global wave index has been produced from the INTERMAGNET, MACCS, CPMN, and Greenland dense magnetometer arrays in the northern hemisphere. A similar ULF wave

  13. Considerations on the Time Consistency of the Large-Scale Composite Geomagnetic Maps

    Microsoft Academic Search

    L. Besutiu

    2008-01-01

    Beyond its undoubtedly success, the recently achieved World Digital Magnetic Anomaly Map (WDMAM) has raised again the issue of the consistency of the large-scale composite geomagnetic images based on raw data gathered within distinct geomagnetic surveys carried out during a long time-span. As it can be noticed, no geomagnetic epoch has been assigned to the world model provided. That came

  14. 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).

  15. Role of centennial geomagnetic changes in local atmospheric ionization

    NASA Astrophysics Data System (ADS)

    Usoskin, Ilya; Korte, Monika; Kovaltsov, Gennady

    Many studies of solar-terrestrial relation are based on globally (or hemispherically) averaged quantities, including the average cosmic ray flux. However, regional effects of cosmic ray induced ionization due to geomagnetic changes may be comparable to or even dominate over the solar signal at mid-latitudes on centennial-to-millennial time scales. We show that local changes of the tropospheric ionization due to fast migration of the geomagnetic axis are crucial on centennial time scale, and the use of global averages may smear an important effect. We conclude that changes of the regional tropospheric ionization at midlatitudes are defined by both geomagnetic changes and solar activity, and none of the two processes can be neglected. This substantiates a necessity for a careful analysis of the regional, not global, indices at mid-latitudes and offers a new possibility to disentangle direct (solar radiation) and indirect (via cosmic rays) effects in the solar-terrestrial relations.

  16. 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.

  17. F layer positive response to a geomagnetic storm - June 1972

    NASA Technical Reports Server (NTRS)

    Miller, N. J.; Grebowsky, J. M.; Mayr, H. G.; Harris, I.; Tulunay, Y. K.

    1979-01-01

    A circulation model of neutral thermosphere-ionosphere coupling is used to interpret in situ spacecraft measurements taken during a topside midlatitude ionospheric storm. The data are measurements of electron density taken along the circular polar orbit of Ariel 4 at 550 km during the geomagnetically disturbed period June 17-18, 1972. It is inferred that collisional momentum transfer from the disturbed neutral thermosphere to the ionosphere was the dominant midday process generating the positive F-layer storm phase in the summer hemisphere. In the winter hemisphere the positive storm phase drifted poleward in the apparent response to magnetospheric E x B drifts. A summer F-layer positive phase developed at the sudden commencement and again during the geomagnetic main phase; a winter F-layer positive phase developed only during the geomagnetic main phase. The observed seasonal differences in both the onsets and the magnitudes of the positive phases are attributed to the interhemispheric asymmetry in thermospheric dynamics.

  18. A source for the geomagnetic storm main phase ring current

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.; Williams, D. J.

    1980-01-01

    The paper considers a proposed source for the geomagnetic storm main phase ring current. It is shown that the flux increases of trapped ions and electrons observed by Explorer 45 at L below 4 during two large geomagnetic storms can be explained by inward radial displacement of the preexisting trapped particle distribution. The proposed source requires only the acceleration of the previously entrapped particle population by inward displacement under conservation of the first two adiabatic invariants. It is suggested that a significant difference between large geomagnetic storms and typical substorm activity may be the inward convection occurring over a large longitude range during storms, but only over a small longitude range during typical substorms.

  19. 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.

  20. Effects of Dipole Tilt Angle on Geomagnetic Activities

    NASA Astrophysics Data System (ADS)

    Nowada, M.; Shue, J.; Russell, C. T.

    2007-12-01

    Relationships between the clock angle of the interplanetary magnetic field (IMF) and each of the AL and AU indices are examined under various Earth's dipole tilt angles using the observational data for a period of 1978 to 1988. This study is performed by correlating the interplanetary magnetic field data obtained from the IMP 8 satellite, the AL and AU indices with the corrected seasonal variations, and the dipole tilt angle. It is found that for any value of the IMF clock angle, the values of AL and AU decrease when the dipole tilt angle becomes larger. It suggests that the geomagnetic activities strongly depend on the dipole tilt angle. Furthermore, our results are consistent with the semiannual variation of the geomagnetic activity and the predicted relationships between the geomagnetic activity, the IMF clock angle, and the dipole tilt angle, derived from the MHD simulation.

  1. 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.

  2. Statistical properties of geomagnetic measurements as possible precursors for magnetic storms

    E-print Network

    Andres R. R. Papa; Lilian P. Sosman

    2006-05-30

    Records of geomagnetic measurements have been analyzed looking for evidences of possible precursors for magnetic storms. With this objective, the main magnetic storms in the period 1998-2002 have been located in Dst index record. Periods immediately before storms and periods well before them were studied by applying a method recently introduced in the literature. Statistical properties of both types of periods have been compared. One of the compared quantities was the slope of the power laws that have been found for some relevant distributions. A systematic deviation between slope distributions was found. This might be the fingerprint of a non self-organized component in records. There has also been found a correlation between slope values and the corresponding storm intensities, which could serve as a probabilistic approach to magnetic storms forecasting. Data is from the low latitude Vassouras Magnetic Observatory.

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

    NASA Astrophysics Data System (ADS)

    Jacobsen, Knut Stanley; Schäfer, 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.

  4. Kristian Birkeland's pioneering investigations of geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Egeland, A.; Burke, W. J.

    2010-04-01

    More than 100 years ago Kristian Birkeland (1967-1917) addressed questions that had vexed scientists for centuries. Why do auroras appear overhead while the Earth's magnetic field is disturbed? Are magnetic storms on Earth related to disturbances on the Sun? To answer these questions Birkeland devised terrella simulations, led coordinated campaigns in the Arctic wilderness, and then interpreted his results in the light of Maxwell's synthesis of laws governing electricity and magnetism. After analyzing thousands of magnetograms, he divided disturbances into 3 categories: 1. Polar elementary storms are auroral-latitude disturbances now called substorms. 2. Equatorial perturbations correspond to initial and main phases of magnetic storms. 3. Cyclo-median perturbations reflect enhanced solar-quiet currents on the dayside. He published the first two-cell pattern of electric currents in Earth's upper atmosphere, nearly 30 years before the ionosphere was identified as a separate entity. Birkeland's most enduring contribution toward understanding geomagnetic disturbances flowed from his recognition that field-aligned currents must connect the upper atmosphere with generators in distant space. The existence of field-aligned currents was vigorously debated among scientists for more than 50 years. Birkeland's conjecture profoundly affects present-day understanding of auroral phenomena and global electrodynamics. In 1896, four years after Lord Kelvin rejected suggestions that matter passes between the Sun and Earth, and two years before the electron was discovered, Birkeland proposed current carriers are "electric corpuscles from the Sun" and "the auroras are formed by corpuscular rays drawn in from space, and coming from the Sun". It can be reasonably argued that the year 1896 marks the founding of space plasma physics. Many of Birkeland's insights were rooted in observations made during his terrella experiments, the first attempts to simulate cosmic phenomena within a laboratory. Birkeland's ideas were often misinterpreted or dismissed, but were verified when technology advances allowed instrumented spacecraft to fly in space above the ionosphere.

  5. Geomagnetic inverse problem and data assimilation: a progress report

    NASA Astrophysics Data System (ADS)

    Aubert, Julien; Fournier, Alexandre

    2013-04-01

    In this presentation I will present two studies recently undertaken by our group in an effort to bring the benefits of data assimilation to the study of Earth's magnetic field and the dynamics of its liquid iron core, where the geodynamo operates. In a first part I will focus on the geomagnetic inverse problem, which attempts to recover the fluid flow in the core from the temporal variation of the magnetic field (known as the secular variation). Geomagnetic data can be downward continued from the surface of the Earth down to the core-mantle boundary, but not further below, since the core is an electrical conductor. Historically, solutions to the geomagnetic inverse problem in such a sparsely observed system were thus found only for flow immediately below the core mantle boundary. We have recently shown that combining a numerical model of the geodynamo together with magnetic observations, through the use of Kalman filtering, now allows to present solutions for flow throughout the core. In a second part, I will present synthetic tests of sequential geomagnetic data assimilation aiming at evaluating the range at which the future of the geodynamo can be predicted, and our corresponding prospects to refine the current geomagnetic predictions. Fournier, Aubert, Thébault: Inference on core surface flow from observations and 3-D dynamo modelling, Geophys. J. Int. 186, 118-136, 2011, doi: 10.1111/j.1365-246X.2011.05037.x Aubert, Fournier: Inferring internal properties of Earth's core dynamics and their evolution from surface observations and a numerical geodynamo model, Nonlinear Proc. Geoph. 18, 657-674, 2011, doi:10.5194/npg-18-657-2011 Aubert: Flow throughout the Earth's core inverted from geomagnetic observations and numerical dynamo models, Geophys. J. Int., 2012, doi: 10.1093/gji/ggs051

  6. 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.

  7. 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.

  8. 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.

  9. Correlations between SAR arc intensity and solar and geomagnetic activity

    E-print Network

    Paris-Sud XI, Université de

    Correlations between SAR arc intensity and solar and geomagnetic activity V. V. Lobzin, A. V a study of statistical relation- ships between SAR arc intensities acquired by the Paci®c Northwest correlation coecients depend on the time oset, t, between the time of SAR arc intensity observations

  10. Shape of the Geomagnetic Field Solar Wind Boundary

    Microsoft Academic Search

    Gilbert D. Mead; David B. Beard

    1964-01-01

    The shape of the boundary of the geomagnetic field in a solar wind has been calculated by a self-consistent method in which, in first order, approximate magnetic fields are used to calculate a boundary surface. The electric currents in this boundary produce mag- netic fields, which can be calculated once the first surface is known. These are added to the

  11. Long-term occurrence probabilities of intense geomagnetic storm events

    Microsoft Academic Search

    K. Tsubouchi; Y. Omura

    2007-01-01

    A quantitative assessment of the occurrence probability of intense geomagnetic storms (peak Dst 280 nT) storms. The mathematical tool to determine this type of PDF is the extreme value modeling, which exhibits more accurate statistics for extreme behavior. Our results estimate S60 ? 589, indicating that the March 1989 storm (the event with the largest ?Dst? in the database) corresponds

  12. 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.

  13. Model simulation of thermospheric response to recurrent geomagnetic forcing

    Microsoft Academic Search

    Liying Qian; Stanley C. Solomon; Martin G. Mlynczak

    2010-01-01

    We assess model capability in simulating thermospheric response to recurrent geomagnetic forcing driven by modulations in the solar wind speed and the interplanetary magnetic field. Neutral density and nitric oxide (NO) cooling rates are simulated for the declining phase of solar cycle 23. The simulated results are compared to neutral density derived from satellite drag and to NO cooling measured

  14. 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.

  15. New insights on geomagnetic storms from observations and modeling

    SciTech Connect

    Jordanova, Vania K [Los Alamos National Laboratory

    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.

  16. Response of the topside ionosphere to recurrent geomagnetic activity

    Microsoft Academic Search

    Jing Liu; Libo Liu; Biqiang Zhao; Weixing Wan; Roderick A. Heelis

    2010-01-01

    In the present study we investigate the solar activity, local time, and latitudinal dependence of the topside ionosphere response to recurrent geomagnetic activity, using 8 years (1998–2005) of data on total ion density (Ni) retrieved from Defense Meteorological Satellites Program observations at about 840 km altitude. It is the first attempt to explore the presence of oscillations in the topside

  17. Some characteristics of intense geomagnetic storms and their energy budget

    Microsoft Academic Search

    Geeta Vichare; S. Alex; G. S. Lakhina

    2005-01-01

    The present study analyses nine intense geomagnetic storms (?Dst? > 175 nT) with the aid of ACE satellite measurements and ground magnetic field values at Alibag Magnetic Observatory. The study confirms the crucial role of southward IMF in triggering the storm main phase as well as controlling the magnitude of the storm. The main phase interval shows clear dependence on

  18. Geomagnetically Induced Currents in European High-Voltage Power Systems

    Microsoft Academic Search

    Risto J. Pirjola; David H. Boteler

    2006-01-01

    Geomagnetically induced currents (GIC) in power systems are a ground manifestation of space weather arising from solar activity. Most of the research on GIC done in Europe so far refers to Scandinavian power grids. A power outage due to GIC occurred in southern Sweden in October 2003. The principal reason that similar GIC problems as in Sweden have not occurred

  19. Study of Thermosphere Temperature Response to Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Suresh, P.; Swenson, C.

    2014-12-01

    The response to geomagnetic storm forcing in the MLT(Mesosphere and Lower Thermosphere) region of the Earth's atmosphere is yet to be completely understood. The kinetic temperture measurements made by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument onboard the TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite provides an unprecedented long-term dataset to advance our understanding of the MLT region. We use this dataset to understand the geomagnetic storm forcing and it's effect on the dynamics of this region. However, in order to deduce the geomagnetic storm response from these kinetic temperature measurements, background effects like seasonal trends and tidal forcing need to be isolated. We present a technique for isolating these background effects and present the resulting geomagnetic storm response in this paper. This analysis has been carried out as a function of latitude, altitude and storm intensity for numerous storm conditions. We also present a comparison of physics and empirical models for a few select storm periods.

  20. Vehicle supervision system based on MEMS geomagnetic sensor

    Microsoft Academic Search

    Jin Wang; Guofeng Li; Yiyi Liu; Yi Lu; Xianhu Gao; Yong Zhang; Ke Tao

    2009-01-01

    Following the economy of our country rapidly develops in recent years, more and more people possess vehicles of their own, and the number of urban vehicle is increasing fast as well. All of these directly challenge the management of urban traffic and normalization of driving behavior. According to actual request for urban traffic, Vehicle Supervision System Based on MEMS Geomagnetic

  1. The Physics of Geomagnetic-Field Transduction in Animals

    Microsoft Academic Search

    Michael Winklhofer

    2009-01-01

    Birds, fish, sea turtles, and various other animals have been reported to sense the geomagnetic field and to use it for orientation, navigation, and homing. In recent years, exciting progress has been made towards elucidating the physical and structural basis of this remarkable phenomenon. This paper focuses on the two hypotheses that drive current research into magnetoreception. One proposal relies

  2. Geomagnetic control of polar mesosphere summer echoes , P. Homann1

    E-print Network

    Boyer, Edmond

    ) of the radar results and the geomagnetic K indices could be detected with a maxi- mum correlation near midnight of this phenomenon have been made with dierent radars at dierent places. However even 20 years after the detection / Accepted: 7 September 1999 Abstract. Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N

  3. Investigation of the geomagnetic field polarity during the Jurassic

    Microsoft Academic Search

    Maureen B. Steiner

    1980-01-01

    A large number of sedimentary rock formation the Colorado Plateau and in the Wyoming foreland have been investigated paleomagnetically in an attempt to determine the geomagnetic polarity during the Middle and the early Late Jurassic, a period frequently postulated to have been of constant normal polarity. A survey of published paleomagnetic litature shows this postulate to be without grounds. A

  4. 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.

  5. Cosmic rays flux and geomagnetic field variations at midlatitudes

    NASA Astrophysics Data System (ADS)

    Morozova, Anna; Ribeiro, Paulo; Tragaldabas Collaboration Team

    2014-05-01

    It is well known that the cosmic rays flux is modulated by the solar wind and the Earth's magnetic field. The Earth's magnetic field deflects charged particles in accordance with their momentum and the local field strength and direction. The geomagnetic cutoffs depend both on the internal and the external components of the geomagnetic field, therefore reflecting the geodynamo and the solar activity variations. A new generation, high performance, cosmic ray detector Tragaldabas was recently installed at the University of Santiago de Compostela (Spain). The detector has been acquiring test data since September 2013 with a rate of about 80 events/s over a solid angle of ~5 srad. around the vertical direction. To take full advantage of this new facility for the study of cosmic rays arriving to the Earth, an international collaboration has been organized, of about 20 researchers from 10 laboratories of 5 European countries. The Magnetic Observatory of Coimbra (Portugal) has been measuring the geomagnetic field components for almost 150 years since the first measurements in 1866. It is presently equipped with up-to-date instruments. Here we present a preliminary analysis of the global cosmic ray fluxes acquired by the new Tragaldabas detector in relation to the geomagnetic field variations measured by the Coimbra observatory. We also compare the data from the new cosmic rays detector with results obtained by the Castilla-La Mancha Neutron Monitor (CaLMa, Gadalajara, Spain) that is in operation since October 2011.

  6. Introducing the AAS Education Office Online

    NASA Astrophysics Data System (ADS)

    Duncan, D. K.; Brissenden, G.; Slater, T. F.

    1998-12-01

    The AAS Education Office has just placed its new interactive web site online. The web site features resources to support AAS members creating effective Education and Public Outreach plans, an interactive database to search and add high-quality educational resources useful to AAS members, an annotated bibliography of research in astronomy education, an automated name exchange to link astronomers interested in education with teachers needing partner scientists, and reports and programs from the AAS Education Office.

  7. Outcomes of AA for Special Populations

    Microsoft Academic Search

    Christine Timko

    This chapter reviews research examining outcomes of Alcoholics Anonymous (AA) for special populations. It begins by discussing what is meant by the term “special populations” and why the question of if and how AA is beneficial for special populations needs to be considered. The chapter then examines studies of outcomes of AA participation among women, adolescents, and the elderly, racial

  8. major code major conc codeconcentration program code program degree coll dept AA Associate of Arts NONE No Concentration AA-AA Associate of Arts AA GC WP

    E-print Network

    Dyer, Bill

    NONE No Concentration AA-AA Associate of Arts AA GC WP ABLR Abused Land Rehabilitation NONE Educ - Relations BS AG AGED AMER American Studies NONE No Concentration AMER-BA American Studies BA LS LS ANTH Anthropology NONE No Concentration ANTH-BS Anthropology BS LS SOC ANUR Nursing NONE

  9. 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.

  10. Neural net forecasting for geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Hernandez, J. V.; Tajima, T.; Horton, W.

    1993-01-01

    We use neural nets to construct nonlinear models to forecast the AL index given solar wind and interplanetary magnetic field (IMF) data. We follow two approaches: (1) the state space reconstruction approach, which is a nonlinear generalization of autoregressive-moving average models (ARMA) and (2) the nonlinear filter approach, which reduces to a moving average model (MA) in the linear limit. The database used here is that of Bargatze et al. (1985).

  11. A Superposed Epoch Analysis of Geomagnetic Storms over a Solar Cycle: Geomagnetic and Solar Wind Data, Radar Backscatter & Auroral Imagery

    Microsoft Academic Search

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

    2010-01-01

    Geomagnetic storms - episodes of intense solar wind-magnetosphere coupling usually associated with extreme conditions in the solar wind such as coronal mass ejections (CMEs) or co-rotating interaction regions (CIRs) - cause large global disturbances in the Earth's magnetosphere. During such storms, large amounts of energy are deposited in the magnetotail and inner magnetosphere, producing an enhanced ring current and energising

  12. The Mono Lake geomagnetic excursion recorded in loess: Its application as time marker and implications for its geomagnetic nature

    Microsoft Academic Search

    U. Hambach; M. Hark; C. Zeeden; B. Reddersen; L. Zöller; M. Fuchs

    2009-01-01

    One of the youngest and worldwide documented geomagnetic excursions in the Brunhes Chron is the Mono Lake excursion (MLE). It has been detected in marine and terrestrial sedimentary archives as well as in lavas. Recent age determinations and age estimates for the MLE centre around an age interval of approximately 31 - 34 ka. Likewise the Laschamp excursion the MLE

  13. 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…

  14. 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. González, 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.

  15. Particle precipitation during ICME-driven and CIR-driven geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Longden, N.; Denton, M. H.; Honary, F.

    2008-06-01

    Interplanetary coronal mass ejections (ICME) and corotating interaction regions (CIR) alter the parameters of the solar wind and interplanetary magnetic field (IMF) that affect conditions in the Earth's magnetosphere and particle precipitation in the auroral zone. We perform a superposed epoch study of the effects of ICME-dominated and CIR-dominated solar wind on particle precipitation during geomagnetic storms. We use data from a set of 38 CIR events and 33 ICME events. Particle precipitation is inferred from cosmic noise absorption (CNA) recorded by the riometer at Abisko. The electron flux intensity at geosynchronous orbit close to the location of the riometer is taken from the synchronous orbit particle analyzer (SOPA) onboard the Los Alamos National Laboratory (LANL) satellite LANL-01A. The results show that mean CNA is more intense during the main phase of ICME-driven storms. In contrast, mean CNA remains elevated for a much longer period during CIR-driven storms indicating prolonged periods of particle precipitation. Enhanced CNA over a sustained period of time is observed during CIR-driven storms that are categorized as only weak or moderate in terms of the response that they drive in the Dst index (Dst >-100 nT). This result indicates that events which may be considered geomagnetically ineffective have a significant effect on particle precipitation in the auroral zone. The elevated CNA observed during CIR-driven storms is accompanied by elevated electron flux intensity, measured at geosynchronous orbit, over all channels in the 50-500 keV range at all local times.

  16. 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

  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. 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.

  19. Geomagnetic field excursions occurred often during the last million years

    NASA Astrophysics Data System (ADS)

    ODP Leg 172 Scientific Party; Lund, Steve P.; Acton, Gary; Clement, Brad; Hastedt, Margaret; Okada, Mokoto; Williams, Trevor

    Scientists studying western North Atlantic Ocean deep-sea sediments have discovered that the Earth's magnetic field underwent 14 local excursions since the last global magnetic-field polarity reversal 780,000 years ago. These excursions coincide with similar excursions identified elsewhere on the planet—leading to the conclusion that excursions are global in nature, occur a significant portion of the time, and are an integral part of geomagnetic field secular variation between reversals. Excursions are defined [Verosub and Banerjee, 1977] as anomalous magnetic field directions whose equivalent virtual geomagnetic poles (VGPs) are more than 45° away from the North Geographic Pole, while VGPs within 45° of the North Geographic Pole are considered to be typical secular variation. (VGPs are calculated from local magnetic field directions which locate the magneticfield North Pole by assuming that the directions are caused by a simple dipole or bar magnet situated at the center of the Earth.)

  20. 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.

  1. 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.

  2. MAGE Project: 4D Visualization of geomagnetic field

    NASA Astrophysics Data System (ADS)

    Yamagishi, Y.; Hatakeyama, T.

    2010-12-01

    We have developed productions for 3D (spatial) + 1D (temporal) visualization of geomagnetic field (magnetic field lines and observed components on the surface of the Earth) in the Google Earth framework. This project, MAGE (Mapping Applications to Geomagnetic Environments), has three targets, [1] for helping researcher's inspiration, [2] for educational application and [3] for outreach. Now we released KML files showing the fields calculated from several published secular variation models (including a reversal field model) and from a geodynamo simulated model. Moreover we demonstrate a new usage of Google Earth for paleomagnetism and rock magnetism, in which direction data are plotted on the Earth as a unit sphere. Since April 2007, our products, KML files, have been released on the website http://mage-p.org/ for free. Here we introduce the released KML files and show examples of usage of the KML files for researches.

  3. 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.

  4. Do geomagnetic disturbances of solar origin affect arterial blood pressure?

    Microsoft Academic Search

    S Ghione; L Mezzasalma; CDel Seppia; F Papi

    1998-01-01

    Objective: Episodic reports suggest that geomagnetic disturbances of solar origin are associated with biological and clinical events, including increased arterial blood pressure (BP). We reassessed this aspect by relating solar activity levels to ambulatory BP measured in our out-patient population.Patients and methods: The ambulatory BP measurements of 447 consecutive untreated patients attending a hypertension out-patient clinic who did a monitoring

  5. Geomagnetic Reversals and Crustal Spreading Rates During the Miocene

    Microsoft Academic Search

    Richard J. Blakely

    1974-01-01

    Statistical analysis of the geomagnetic time scale suggests that the rate of reversals was anomalously low during the Miocene. To determine whether undetected reversals actually occurred in the Miocene, 14 magnetic profiles from a survey of the northeast Pacific by NOAA are analyzed by signal-averaging techniques. The data suggest that during the time period 7.3 to 22.7 m.y., eight short-wavelength

  6. 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.

  7. Geomagnetic secular variation and the statistics of palaeomagnetic directions

    NASA Astrophysics Data System (ADS)

    Deenen, Martijn H. L.; Langereis, Cor G.; van Hinsbergen, Douwe J. J.; Biggin, Andrew J.

    2011-08-01

    In this study, we examine the role of palaeosecular variation (PSV) in the use of statistics for palaeomagnetic studies, and we provide new reliability criteria for palaeomagnetic poles or directions. We first conclude that Fisher statistics should not be applied to average palaeomagnetic directions but to virtual geomagnetic pole (VGP) distributions instead. Secondly, we strongly advocate that typical properties of geomagnetic field behaviour are taken into account in the assessment of palaeomagnetic data sets. The latitude-dependent properties (E, S, k) provide useful guidelines for the reliability of a palaeomagnetic data set. A reliable assessment of these properties depends on the (sufficient) number of palaeomagnetic samples being taken. Therefore, as an additional instrument of assessing data sets, we provide a N-dependent A95 envelope, bounded by an upper limit A95max, and a lower limit A95min that helps to ascertain whether or not a distribution has sufficiently well-sampled PSV and therefore geomagnetic field behaviour. Applying these criteria is indispensable for studies of geomagnetic behaviour, or for studies aiming at using TK03.GAD for inclination error correction through the elongation/inclination (E/I) method. For palaeomagnetic studies aimed at geological reconstructions, they form helpful guidelines and increase the confidence in the rocks having faithfully recorded the field. An analysis of published Eastern Mediterranean data shows that the vast majority of studies do not conform to the Van der Voo criteria, in particular with respect to N and A95. We have provided criteria that are on the one hand more lenient (lower N may still provide relevant information), and on the other hand more strict (for high N the criterion of A95 < 16° should be adapted to a requirement of lower A95, e.g. A95 < 5° for N > 80).

  8. Wavelet analysis of relative geomagnetic paleointensity at ODP Site 983

    Microsoft Academic Search

    Yohan Guyodo; Philippe Gaillot; James E. T. Channell

    2000-01-01

    We performed spectral analysis of the record of relative geomagnetic paleointensity obtained at ODP Site 983, covering the time interval 0–1.1 Ma. The results confirm the presence of significant power at frequencies corresponding to the earth orbital parameters (eccentricity, obliquity, precession). The construction of the evolutionary spectrum allowed us to establish the non-stationarity of the signal at those frequencies. The

  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. The flywheel effect: Ionospheric currents after a geomagnetic storm

    Microsoft Academic Search

    W. Deng; T. L. Killeen; A. G. Burns; R. G. Roble

    1991-01-01

    In the period following a geomagnetic storm the high-latitude, magnetospheric-driven convection pattern is normally weak. However, the neutral circulation, set up by ion-neutral momentum coupling during the main phase of the storm, may continue for several hours after the storm has ended. This persistent neutral circulation has the potential to drive Hall currents for some hours. In this paper the

  11. 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.

  12. Geomagnetic responses to the solar wind and to solar activity

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1974-01-01

    A unified overview of present knowledge of the geomagnetic response to the dynamic solar wind is reported. The formation of the magnetosphere and the magnetospheric tail is discussed the importance of electric fields is stressed, and the magnetospheric convection of plasma and frozen-in magnetic field lines under the influence of large scale magnetospheric electric fields is outlined. Ionospheric electric fields and currents are intimately related to electric fields and currents in the magnetosphere and the strong coupling between the two regions is discussed. The energy input of the solar wind to the magnetosphere and upper atmosphere is discussed in terms of the reconnection model where interplanetary magnetic field lines merge or connect with the terrestrial field on the sunward side of the magnetosphere. The merging model emphasizes the importance of the interplanetary magnetic field and especially the north-south component. The solar sector structure with its organized magnetic field and embeeded high speed plasma streams is identified as the source of recurrent geomagnetic disturbances while flare associated interplanetary shock waves are the source of most violet and sporadic geomagnetic storms.

  13. Recent developments in the global geomagnetic observatory network

    NASA Astrophysics Data System (ADS)

    Chulliat, A.

    2011-12-01

    Magnetic observatories provide precise and continuous measurements of geomagnetic variations over time scales ranging from one second to more than a century. They have been an essential observational infrastructure for geomagnetic research for about 170 years. A large fraction of magnetic observatories belong to INTERMAGNET (International Real-time Magnetic Observatory Network), a global network founded in the late 1980s which now includes about 115 observatories in 45 countries. INTERMAGNET magnetic observatories comply with strict data quality and timeliness standards and distribute their data through an integrated data information system. Recent years have seen a rapid expansion of the global network: new observatories have been installed in remote locations, such as oceanic islands (St Helena, Easter Island, Tristan da Cunha) or Antarctica (Dome C); ancient observatories have been upgraded to international standards (for example in China and Siberia). This has been prompted by the need to have a more geographically homogeneous network. In parallel, new data products (one second data and quasi-definitive data) are being made available, addressing a wide variety of research needs, and real timeliness is being improved for operational purposes such as space weather monitoring and forecasting. This presentation will provide an overview of these recent developments, focusing on those most relevant to the geomagnetic modeling community, and discuss their expected scientific benefits.

  14. Development of a Systematic Model for Study on the Phenomena of Ionospheric and Geomagnetic Variations

    NASA Astrophysics Data System (ADS)

    Pyo, Yoo Surn; Rhee, Hwang-Jae; Kim, Min-Geun; Kim, Eunhwa; Song, Sung-Hee; Lee, Jinny; Lee, Dong-Hun

    1999-12-01

    Solar activities ejecting high energy particles influence satellites and satellite communications as well as perturb geomagnetic fields. To understand space environments near the Earth being influenced by the Sun, we must study about the magnetosphere, the ionosphere, and the atmosphere beforehand. To study this issue, we investigate some ionospheric models, atmospheric models and geomagnetic field models : IRI(International Reference Ionosphere), PIM(Parameterized Ionospheric Model) and IGRF(International Geomagnetic Reference Field). We develop the models and build a web site to serve IRI, PIM and IGRF model on the internet so that one can easily get information of daily and global ionospheric and geomagnetic variations.

  15. 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).

  16. DIVISION CATEGORY DESCRIPTION ITEM DESCRIPTION AA Advertise Advertising for courses

    E-print Network

    Rainforth, Emma C.

    and Printing Marketing Plan for nationwide on-line course delivery AA Advertising and Printing Marketing and Printing Marketing/advertising/recruitment for all programs AA All Other Salaries On-line course stipends Professional Development AA Other Expenses On-line Courses AA Other Expenses Guest speakers AA Other Expenses

  17. AA1 ? : A DYNAMIC INCREMENTAL NETWORK THAT LEARNS BY DISCRIMINATION

    E-print Network

    Martinez, Tony R.

    AA1 ? : A DYNAMIC INCREMENTAL NETWORK THAT LEARNS BY DISCRIMINATION Christophe Giraud­Carrier Tony network. It receives inputs and produces an output as the data flow asynchronously and in parallel through­ gorithm (AA) 1 [10], AA2 [8] and AA3 [9]. AA2 inductively constructs a logic circuit consistent

  18. Immigration Index

    NSDL National Science Digital Library

    Striving to become the "immigration resource directory on the net," the Immigration Index is a newly launched Website dedicated to news and information about immigration worldwide. Along with breaking headlines from a variety of news sources about immigration-related issues such as asylum, migration, trafficking and women, and much more, the site contains a fully annotated collection of links to immigration materials all around the World Wide Web. Only a month old, some of the categories in the Index's hierarchy still need some filling in. In time, however, the Immigration Index promises to become an invaluable resource for interested parties.

  19. Coronal Mass Ejections And Disturbances In Solar Wind Plasma Parameters In Relation With Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Verma, P. L.; Singh, Puspraj; Singh, Preetam

    2014-05-01

    Coronal Mass Ejections (CMEs) are the drastic solar events in which huge amount of solar plasma materials are ejected into the heliosphere from the sun and are mainly responsible to generate large disturbances in solar wind plasma parameters and geomagnetic storms in geomagnetic field. We have studied geomagnetic storms, (Dst <=-75nT) observed during the period of 1997-2007 with Coronal Mass Ejections and disturbances in solar wind plasma parameters (solar wind temperature, velocity, density and interplanetary magnetic field) .We have inferred that most of the geomagnetic storms are associated with halo and partial halo Coronal Mass Ejections (CMEs).The association rate of halo and partial halo coronal mass ejections are found 72.37 % and 27.63 % respectively. Further we have concluded that geomagnetic storms are closely associated with the disturbances in solar wind plasma parameters. We have determined positive co-relation between magnitudes of geomagnetic storms and magnitude of jump in solar wind plasma temperature, jump in solar wind plasma density, jump in solar wind plasma velocity and jump in average interplanetary magnetic field with co-relation co-efficient 0 .35 between magnitude of geomagnetic storms and magnitude of jump in solar wind plasma temperature, 0.19 between magnitude of geomagnetic storms and magnitude of jump in solar wind density, 0.34 between magnitude of geomagnetic storms and magnitude of jump in solar wind plasma velocity, 0.66 between magnitude of geomagnetic storms and magnitude of jump in average interplanetary magnetic field respectively. We have concluded that geomagnetic storms are mainly caused by Coronal Mass Ejections and disturbances in solar wind plasma parameters that they generate.

  20. 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.

  1. UK Index

    NSDL National Science Digital Library

    The UK Index provides a searchable index of resources in or about the United Kingdom. The Quick Reference section offers links to News Resources in the UK such as the BBC, weather information, UK record charts, and UK related USENET newsgroups. The Foreign & Commonwealth Office provides good advice for travelers. The search engine allows the selection of categories such as arts or business to restrict the search to pages included in one category or a combination of categories.

  2. Characteristics of the ionospheric variability as a function of season, latitude, local time, and geomagnetic activity

    Microsoft Academic Search

    E. A. Araujo-Pradere; T. J. Fuller-Rowell; M. V. Codrescu; D. Bilitza

    2005-01-01

    An ionospheric F2 critical frequency database has been assembled to determine the variability of the F region as a function of local time, latitude, season, and geomagnetic activity. The database comprises observations from 75 ionosonde stations covering a range of geomagnetic latitude and includes 43 storm intervals. The database was previously used to develop the Storm-Time Empirical Ionospheric Correction Model

  3. Bias Corrections for Regional Estimates of the Time-averaged Geomagnetic Field

    Microsoft Academic Search

    C. Constable; C. L. Johnson

    2009-01-01

    We assess two sources of bias in the time-averaged geomagnetic field (TAF) and paleosecular variation (PSV): inadequate temporal sampling, and the use of unit vectors in deriving temporal averages of the regional geomagnetic field. For the first temporal sampling question we use statistical resampling of existing data sets to minimize and correct for bias arising from uneven temporal sampling in

  4. Anomaly geomagnetic field in the center part of the Balcan Peninsula

    NASA Astrophysics Data System (ADS)

    Delipetrev, Marjan; Doneva, Blagica; Delipetrov, Todor; Dimov, Gorgi

    2014-05-01

    An analysis of the structure geomagnetic field from the geomagnetic measurements performed in the last decade in the territory of the Republic of Macedonia. The research area is in the center of the Balkan Peninsula. Geological processes led to complex structure both at the surface of the terrain, and below the surface. The diversity of the rocks produce clear differences in the measurements of the magnetic field in this area. The magnetic field is presented how the sum of two components: Normal and anomalous geomagnetic field. Regional terrain observations implemented from 15 repeat stations, allows us to define both the normal geomagnetic field and the anomalous geomagnetic field from regional aspect. Observation net is not dense, so it is not sufficient to define the local anomalies of the geomagnetic field. The Correlation between maps of regional local anomaly geomagnetic field and the conclusions are also presented. Regarding the former, there is a good correlation between regional anomalous geomagnetic field and neotectonic regionalization in the area differentiating three zones: Western Macedonian zone, Vardar zone and Eastern Macedonian zone.

  5. Geomagnetic secular variation in the Cretaceous Normal Superchron and in the Jurassic

    Microsoft Academic Search

    Andrew J. Biggin; Douwe J. J. van Hinsbergen; Cor G. Langereis; Gijs B. Straathof; Martijn H. L. Deenen

    2008-01-01

    It is now widely thought that geomagnetic polarity reversals occur spontaneously as a result of normal dynamo action rather than being externally triggered. If this is the case, then it may well be that periods of time in which the geomagnetic reversal frequency was dramatically different were characterised by different styles of secular variation. Two such periods were the Cretaceous

  6. Observations of the geomagnetic field by Polar Patrol Balloon (PPB) experiment in Antarctica

    Microsoft Academic Search

    Fumio Toyama; Ryoichi Fujii; Masaki Ejiri; Nobuyuki Yajima

    1993-01-01

    Two scientific balloon experiments of the Polar Patrol Balloon (PPB) project were performed by the 32nd Japanese Antarctic Research Expedition in December 1990 to January 1991. Proton precession magnetometers were used to measure the total intensity of the geomagnetic field for studying the underground magnetic structure by detecting magnetic anomalies and geomagnetic variations like pulsations. The first balloon (PPB-1) showed

  7. PARTICLE TRAJECTORIES IN MODEL CURRENT SHEETS. 2. APPLICATIONS TO AURORAS USING A GEOMAGNETIC TAIL MODEL

    Microsoft Academic Search

    T. W. Speiser

    1967-01-01

    Individual particle trajectories are determined analytically and numerically in two possible configurations of electric and magnetic fields in the geomagnetic tail. The models are based on reconnection models incorporating a neutral point with associated neutral or current sheet and on the observed neutral sheet in the geomagnetic tail. Both models contain magnetic field lines oppositely directed on either side of

  8. Tracking Sun-Earth-Connection Chain Events of Major Geomagnetic Storms

    Microsoft Academic Search

    J. Zhang; W. Poomvises

    2005-01-01

    We address the issues in observing and understanding the chain Sun-Earth connection activities that result in major geomagnetic storms, one of severe space weather phenomena. From 1996 to 2004, there are 77 major geomagnetic storms (defined as Dst <= -100). A systematic multi-step process is carried out to identify the event chain for each of the major events. It is

  9. 1. Introduction Field-aligned currents have a significant effect on geomagnetic disturbances at mid lat-

    E-print Network

    Nakano, Shin'ya

    1. Introduction Field-aligned currents have a significant effect on geomagnetic disturbances at mid caused by field-aligned currents (e.g., Nakano and Iyemori, 2003a). In particular, east-west geomagnetic disturbances D at mid latitudes are mainly attributed to field-aligned currents (e.g., Sun et al., 1984). Since

  10. Relations Among Sunspots, CMEs and Geomagnetic Storms in Solar Cycle 23

    Microsoft Academic Search

    Su-Lyun Rho; Heon-Young Chang

    2009-01-01

    We compare the relation among the annual distribution of sunspots, coronal mass ejections (CMEs) and geomagnetic storms and North-South asymmetry during solar cycle 23. For this purpose, we calculate correlation coefficients between (i) annual distribution and N-S asymmetry of CMEs - sunspots (ii) distribution of CMEs - occurrence number of geomagnetic storms (iii) distribution of sunspots - occurrence number of

  11. Risk Analysis and Forecast Service for Geomagnetically Induced Currents in Europe

    Microsoft Academic Search

    Magnus Wik; Risto Pirjola; Ari Viljanen; Henrik Lundstedt

    2010-01-01

    Geomagnetically induced currents (GIC), occurring during magnetic storms, pose a widespread natural disaster risk to the reliable operation of electric power transmission grids, oil and gas pipelines, telecommunication cables and railway systems. The solar magnetic activity is the cause of GIC. Solar coronal holes can cause recurrent inter-vals of raised geomagnetic activity, and coronal mass ejections (CME) at the Sun,

  12. Motions of the Earth's Core and Mantle, and Variations of the Main Geomagnetic Field

    Microsoft Academic Search

    Raymond Hide

    1967-01-01

    Theoretical work on the magnetohydrodynamics of the earth's liquid core indicates (a) that horizontal variations in the properties of the core-mantle interface that would escape detection by modern seismological methods might nevertheless produce measurable geomagnetic effects; (b) that the rate of drift, relative to the earth's surface, of nonaxisymmetric features of the main geomagnetic field might be much faster than

  13. Geomagnetic dipole strength and reversal rate over the past two million years

    Microsoft Academic Search

    Jean-Pierre Valet; Laure Meynadier; Yohan Guyodo

    2005-01-01

    Independent records of relative magnetic palaeointensity from sediment cores in different areas of the world can be stacked together to extract the evolution of the geomagnetic dipole moment and thus provide information regarding the processes governing the geodynamo. So far, this procedure has been limited to the past 800,000years (800kyr ref. 3), which does not include any geomagnetic reversals. Here

  14. 2 Geomagnetic dipole moment collapse by convective mixing in the core 3 Lijun Liu1

    E-print Network

    Olson, Peter L.

    2 Geomagnetic dipole moment collapse by convective mixing in the core 3 Lijun Liu1 and Peter Olson2 of the geomagnetic dipole. Here we 8 determine rates of dipole moment decrease as a function of 9 magnetic Reynolds rate 20 of dipole moment decrease on century time scales is weakly 21 sensitive to the mixing flow

  15. Detection of explosive events by monitoring acoustically-induced geomagnetic perturbations

    Microsoft Academic Search

    J P Lewis; D R Rock; D L Shaeffer; S I Warshaw

    1999-01-01

    The Black Thunder Coal Mine (BTCM) near Gillette, Wyoming was used as a test bed to determine the feasibility of detecting explosion-induced geomagnetic disturbances with ground-based induction magnetometers. Two magnetic observatories were fielded at distances of 50 km and 64 km geomagnetically north from the northernmost edge of BTCM. Each observatory consisted of three separate but mutually orthogonal magnetometers, Global

  16. Modeling impacts of geomagnetic field variations on middle atmospheric ozone responses to solar proton

    E-print Network

    Wehrli, Bernhard

    Modeling impacts of geomagnetic field variations on middle atmospheric ozone responses to solar variations on middle atmospheric ozone responses to solar proton events on long timescales, J. Geophys. Res charged particles of solar and cosmic origin. Therefore variations of the geomagnetic field occurring

  17. Variations of low-latitude geomagnetic fields and Dst index caused by magnetospheric substorms

    Microsoft Academic Search

    Chao-Song Huang; J. C. Foster; L. P. Goncharenko; G. D. Reeves; J. L. Chau; K. Yumoto; K. Kitamura

    2004-01-01

    We present observations of periodic magnetospheric substorms and corresponding ionospheric disturbances. Since the periodic substorms occur during a stable interplanetary magnetic field, we are able to identify which ionospheric signatures are caused solely by substorms. We find that the low-latitude ionospheric electric field perturbation after substorm onsets is eastward on the dayside and westward on the nightside and that the

  18. GPS phase scintillation and proxy index at high latitudes during a moderate geomagnetic storm

    E-print Network

    Prikryl, P.

    The amplitude and phase scintillation indices are customarily obtained by specialised GPS Ionospheric Scintillation and TEC Monitors (GISTMs) from L1 signal recorded at the rate of 50 Hz. The scintillation indices S[subscript ...

  19. Dynamic Geomagnetic Hazard Maps in Space Weather Operations

    NASA Astrophysics Data System (ADS)

    Rigler, E. J.; Pulkkinen, A. A.; Balch, C. C.; Wiltberger, M. J.

    2014-12-01

    Traditionally, the use of geomagnetic data in space weather operations has been limited to specific geographic coordinates (i.e., magnetic observatories), or to global indices that average magnetic measurements into latitudinal bands of relatively general space weather interest (e.g., Dst, Kp, AE). However, modern technological systems (e.g., power grids, directional drilling platforms) are beginning to require and request information about ground magnetic variations that is more tailored to a specific locale. One solution is to simply install magnetic observatories near every newly built technological system, but this is both economically and operationally impractical. We have chosen instead to adopt an optimal interpolation scheme that inverts for spherical elementary current systems (SECS, Amm-1997), which in turn are used to fill gaps between magnetic observatories. The SECS technique has undergone extensive scientific vetting over the last decade-and-a-half, and will soon be implemented operationally over the continental U.S. as a joint NASA-NOAA-USGS space weather data product, disseminated by the Space Weather Prediction Center (SWPC). Because it will employ a relatively sparse array of high-quality geomagnetic observatories as input, it is important to characterize its ability to reproduce spatial variations in geomagnetic field at sub-continental scales, so the Lyon-Fedder-Mobarry (LFM) global geospace model is used to generate realistic synthetic observations. These include virtual magnetic observatories as input, and a regular geographic grid to serve as a proxy for "ground truth". We look specifically at LFM output for the Whole Heliosphere Interval (WHI) in order to obtain statistically valid performance measures for a variety of quiet-to-moderate space weather conditions.

  20. Complexity and Geomagnetic Activity: A Nonlinear Dynamical Analogue Model Approach

    NASA Astrophysics Data System (ADS)

    Currenti, G.; del Negro, C.; Fortuna, L.

    It is clear that if changes in the local magnetic field attributable to the dynamics of a volcano are ever going to be detected, it will require stable, high resolution EarthSs magnetic field readings from a network of sensitive instruments and effective data pro- cessing to reduce the magnetic signal to the level of a few nanotesla which is the ap- parent upper limit of detectability of magnetic anomalies associated with the volcanic activity. With the introduction of the Overhauser proton precession magnetometers, the long-term stability, high sensitivity and fast response to the changing magnetic field for measurements are no longer a problem. On the contrary, the problem of elim- inating from measurements of the total intensity the natural geomagnetic fluctuations of external origin, which may be of the order of several tens of nanotesla, is only partially overcome. Even if data reduction processes are properly employed, however, we often see geomagnetic variations regardless of the state of the volcanic activity. External sources of fluctuations include electric current systems within EarthSs mag- netosphere, which belongs to the class of dissipative chaotic systems. For this reason we propose a method for nonlinear dynamical system identification from measured data. We describe the geomagnetic activity in terms of a relatively simple nonlinear dynamical analogue circuit. The parameters of the circuit are determined in such a way that the electric signal best fits the data acquired by magnetic network installed on Mt. Etna. The synchronization is used to compel the circuit to follow a state trajec- tory that is identical to the one of the magnetic signal. The parameters of system are identified by formulating a global optimization problem.

  1. Continuous global geomagnetic field models for the past 3000 years

    NASA Astrophysics Data System (ADS)

    Korte, Monika; Constable, Catherine

    2003-11-01

    Several global geomagnetic field models exist for recent decades, but due to limited data availability models for several centuries to millennia are rare. We present a continuous spherical harmonic model for almost 3 millennia from 1000 b.c. to 1800 a.d., based on a dataset of directional archaeo- and paleomagnetic data and axial dipole constraints. The model, named Continuous Archaeomagnetic and Lake Sediment Geomagnetic Model for the last 3k years (CALS3K.1), can be used to predict both the field and secular variation. Comparisons and tests with synthetic data lead to the conclusion that CALS3K.1 gives a good general, large-scale representation of the geomagnetic field, but lacks small-scale structure due to the limited resolution of the sparse dataset. In future applications the model can be used for comparisons with additional, new data for that time span. For better resolved regions, the agreement of data with CALS3K.1 will provide an idea about the general compatibility of the data with the field and secular variation in that region of the world. For poorly covered regions and time intervals we hope to iteratively improve the model by comparisons with and inclusion of new data. Animations and additional snapshot plots of model predictions as well as the model coefficients and a FORTRAN code to evaluate them for any time can be accessed under http://www.mahi.ucsd.edu/cathy/Holocene/holocene.html. The whole package is also stored in the Earthref digital archive at http://www.earthref.org/...

  2. Ionosphere response to recurrent geomagnetic activity: local time dependency

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.; Lei, J.; Thayer, J. P.; Forbes, J. M.

    2009-12-01

    Observations of global positioning system total electron content (TEC) and in-situ electron densities at altitudes of ~350-370 km from the CHAMP satellite are used to illustrate the local time and latitude dependence of 9-day periodicities due to recurring high-speed solar wind streams and geomagnetic activity in the ionosphere during 2005. A local time dependence is found, with nighttime TEC oscillations concentrated at high-latitudes and close to ±40 percent of background levels. The largest oscillations in daytime TEC occur at mid-latitudes and are ±25 percent of background levels. Furthermore, the daytime response is generally symmetric about the geomagnetic equator with anti-correlation between high- and low-latitudes, whereas at night the high-latitude Northern Hemisphere is generally in-phase with low-latitudes and anti-correlated with the high-latitude Southern Hemisphere. A combination of enhanced equatorial neutral winds and changes in neutral composition are thought to be the primary mechanisms responsible for the observed ionospheric response. Although similar mechanisms are driving the response, the local time dependency arises due to the presence (lack) of photoionization during the daytime (nighttime). Similar trends are observed in CHAMP in-situ electron densities; however, the oscillations at a near constant altitude are ~10-15 percent larger than the TEC oscillations. Additionally, the CHAMP observations reveal possible variations in the strength of the equatorial ionization anomaly, indicating that disturbance dynamo electric fields may also contribute to the ionospheric response to recurrent geomagnetic activity. The results presented are the first to reveal the significant differences between the daytime and nighttime response of the ionosphere to periodic forcing from solar wind high-speed streams.

  3. Ionosphere response to recurrent geomagnetic activity: Local time dependency

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.; Lei, J.; Thayer, J. P.; Forbes, J. M.

    2010-02-01

    Observations of global positioning system total electron content (TEC) and in situ electron densities at altitudes of ˜350-370 km from the CHAMP satellite are used to illustrate the local time and latitude dependence of 9 day periodicities in the ionosphere due to recurring high-speed solar wind streams and geomagnetic activity during 2005. A local time dependence is found, with nighttime TEC oscillations concentrated at high latitudes and close to ±40% of background levels. The largest oscillations in daytime TEC occur at midlatitudes and are ±25% of background levels. Furthermore, the daytime response is generally symmetric about the geomagnetic equator with anticorrelation between high and low latitudes, whereas at night the high-latitude Northern Hemisphere is generally in-phase with low latitudes and anticorrelated with the high-latitude Southern Hemisphere. A combination of enhanced equatorward neutral winds and changes in neutral composition are thought to be the primary mechanisms responsible for the observed ionospheric response. Although similar mechanisms are driving the response, the local time dependency arises because of the presence (lack) of photoionization during the daytime (nighttime). Similar trends are observed in CHAMP in situ electron densities; however, the oscillations at a near-constant altitude are ˜10-15% larger than the TEC oscillations. Additionally, the CHAMP observations reveal possible variations in the strength of the equatorial ionization anomaly, indicating that disturbance dynamo electric fields may also contribute to the ionospheric response to recurrent geomagnetic activity. The results presented are the first to reveal the significant differences between the daytime and nighttime response of the ionosphere to periodic forcing from solar wind high-speed streams.

  4. Modelling the geomagnetic field from syntheses of paleomagnetic data

    NASA Astrophysics Data System (ADS)

    Constable, Catherine G.

    2011-08-01

    This review examines results from time-varying geomagnetic field models that span several thousand years, and from variations in dipole moment strength up to million year time scales. For the past 400 years, twin magnetic flux lobes bordering the inner core tangent cylinder in both northern and southern hemispheres dominate the geomagnetic field and appear more or less fixed in location. In contrast, the millennial scale view shows that such features are quite mobile and subject to morphological changes on time scales of a few centuries to a thousand years, possibly reflecting large scale reorganization of core flow. The lobes rarely venture into the Pacific hemisphere, and average fields over various time scales generally reveal two or three sets of lobes, of diminished amplitude. Thus millennial scale models are suggestive of thermal core-mantle coupling generating a weak bias in the average field rather than a strong inhibition of large scale field changes. The recovery of variations in dipole moment on million year time scales allows frequency domain analyses to search for characteristic time scales for core dynamics that might be associated with excursion and reversal rate, time taken for reversals, or any signs of control by Earth's orbital parameters. The spectrum is characteristically red for the time interval 0-160 Ma, suggesting non-stationarity associated with average reversal rate changes, probably reflecting the impact of superchrons and a continually evolving core. Distinct regimes of power law decay with frequency may reflect different physical processes contributing to the secular variation. Evidence for non-stationarity at shorter time-scales is also present in dipole moment variations over 0-2 Ma with average growth rate faster than the decay process. Rates of change of dipole moment and rapid local field variations found in the paleomagnetic record are evaluated in the context of the 400 year historical record and the spectrum of geomagnetic variations for 0-160 Ma.

  5. An overset grid method for global geomagnetic induction

    NASA Astrophysics Data System (ADS)

    Weiss, Chester J.

    2014-07-01

    A new finite difference solution to the global geomagnetic induction problem is developed and tested, based on a modified Lorenz gauge of the magnetic vector and electric scalar potentials and implementing a novel, overset `Yin-Yang' grid that avoids unnecessary mesh refinement at the geographic poles. Previously used in whole-earth mantle convection models, the overset grid is built from a pair of partially overlapping mid-latitude latitude-longitude (lat/lon) grids, one of which is rotated with respect to the other for complete coverage of the sphere. Because of this symmetry, only one set of finite difference templates is required for global discretization of the governing Maxwell equations, a redundancy that is exploited for computational efficiency and multithreaded parallelization. Comparisons between solutions obtained by the proposed method show excellent agreement with those obtained by independent integral equation methods for 1-D, 2-D and 3-D problem geometries. The computational footprint of the method is minimized through a (non-symmetric) matrix-free BiCG-STAB iterative solver which computes finite difference matrix coefficients `on the fly' as needed, rather than pulling stored values from memory. Scaling of the matrix-free BiCG-STAB algorithm with problem size shows behaviour similar to that seen with the (symmetric) QMR algorithm used in the Cartesian case from which the present algorithm is based. The proposed method may therefore provide a competitive addition to the existing body of global-scale geomagnetic induction modelling algorithms, allowing for resource-efficient forward modelling as the kernel for large-scale computing such as inversion of geomagnetic response functions, computational hypothesis testing and parametric studies of mantle geodynamics and physiochemical state.

  6. High-latitude geomagnetic disturbances during ascending solar cycle 24

    NASA Astrophysics Data System (ADS)

    Peitso, Pyry; Tanskanen, Eija; Stolle, Claudia; Berthou Lauritsen, Nynne; Matzka, Jürgen

    2015-04-01

    High-latitude regions are very convenient for study of several space weather phenomena such as substorms. Large geographic coverage as well as long time series of data are essential due to the global nature of space weather and the long duration of solar cycles. We will examine geomagnetic activity in Greenland from magnetic field measurements taken by DTU (Technical University of Denmark) magnetometers during the years 2010 to 2014. The study uses data from 13 magnetometer stations located on the east coast of Greenland and one located on the west coast. The original measurements are in one second resolution, thus the amount of data is quite large. Magnetic field H component (positive direction towards the magnetic north) was used throughout the study. Data processing will be described from calibration of original measurements to plotting of long time series. Calibration consists of determining the quiet hour of a given day and reducing the average of that hour from all the time steps of the day. This normalizes the measurements and allows for better comparison between different time steps. In addition to the full time line of measurements, daily, monthly and yearly averages will be provided for all stations. Differential calculations on the change of the H component will also be made available for the duration of the full data set. Envelope curve plots will be presented for duration of the time line. Geomagnetic conditions during winter and summer will be compared to examine seasonal variation. Finally the measured activity will be compared to NOAA (National Oceanic and Atmospheric Administration) issued geomagnetic space weather alerts from 2010 to 2014. Calculations and plotting of measurement data were done with MATLAB. M_map toolbox was used for plotting of maps featured in the study (http://www2.ocgy.ubc.ca/~rich/map.html). The study was conducted as a part of the ReSoLVE (Research on Solar Long-term Variability and Effects) Center of Excellence.

  7. IAGA Geomagnetic Data Analysis format - Analysis_IAGA

    NASA Astrophysics Data System (ADS)

    -Emilian Toader, Victorin; Marmureanu, Alexandru

    2013-04-01

    Geomagnetic research involves a continuous Earth's magnetic field monitoring and software for processing large amounts of data. The Analysis_IAGA program reads and analyses files in IAGA2002 format used within the INTERMAGNET observer network. The data is made available by INTERMAGNET (http://www.intermagnet.org/Data_e.php) and NOAA - National Geophysical Data Center (ftp://ftp.ngdc.noaa.gov/wdc/geomagnetism/data/observatories/definitive) cost free for scientific use. The users of this software are those who study geomagnetism or use this data along with other atmospheric or seismic factors. Analysis_IAGA allows the visualization of files for the same station, with the feature of merging data for analyzing longer time intervals. Each file contains data collected within a 24 hour time interval with a sampling rate of 60 seconds or 1 second. Adding a large number of files may be done by dividing the sampling frequency. Also, the program has the feature of combining data files gathered from multiple stations as long as the sampling rate and time intervals are the same. Different channels may be selected, visualized and filtered individually. Channel properties can be saved and edited in a file. Data can be processed (spectral power, P / F, estimated frequency, Bz/Bx, Bz/By, convolutions and correlations on pairs of axis, discrete differentiation) and visualized along with the original signals on the same panel. With the help of cursors/magnifiers time differences can be calculated. Each channel can be analyzed separately. Signals can be filtered using bandpass, lowpass, highpass (Butterworth, Chebyshev, Inver Chebyshev, Eliptic, Bessel, Median, ZeroPath). Separate graphics visualize the spectral power, frequency spectrum histogram, the evolution of the estimated frequency, P/H, the spectral power. Adaptive JTFA spectrograms can be selected: CSD (Cone-Shaped Distribution), CWD (Choi-Williams Distribution), Gabor, STFT (short-time Fourier transform), WVD (Wigner-Ville Distribution). A special filter eliminates spikes over a threshold amplitude / duration without modifying the rest of the signal. File discontinuities (missing data, samples with the same timestamp, and overlapping periods of time) are signaled and corrected by repeating the last value. Data can be saved in the IAG2002 format (corrected file, files concatenated in time for the same station), SAC bin - Unix (a file for every channel) and PC - SUDS (one file with all channels). This feature allows other software to analyze geomagnetic data associated with other atmospheric phenomena. Analysis_IAGA is a LabVIEW application with GNU (General Public License) license.

  8. Active experiments in the ionosphere and geomagnetic field variations

    NASA Astrophysics Data System (ADS)

    Sivokon, V. P.; Cherneva, N. V.; Khomutov, S. Y.; Serovetnikov, A. S.

    2014-11-01

    Variations of ionospheric-magnetospheric relation energy, as one of the possible outer climatology factors, may be traced on the basis of analysis of natural geophysical phenomena such as ionosphere artificial radio radiation and magnetic storms. Experiments on active impact on the ionosphere have been carried out for quite a long time in Russia as well. The most modern heating stand is located in Alaska; it has been used within the HAARP Program. The possibility of this stand to affect geophysical fields, in particular, the geomagnetic field is of interest.

  9. Two-scale model of a geomagnetic field variation

    NASA Technical Reports Server (NTRS)

    Braginsky, S. I.; Le Mouel, J. L.

    1993-01-01

    The effect of the vertical scale is investigated by considering a simple kinematic two-scale model of fluid flow inducing a variable magnetic field. Depending on the time constant, the induced magnetic field displays a variety of behaviors and geometries. In the high-frequency case, for example, a strong magnetic field tangential to the core mantle boundary, and hidden in the Delta layer, can be generated. A detailed computation and description of this magnetic field are presented. Some possible features of the secular variation of the actual geomagnetic field are discussed in the light of the model proposed here.

  10. Geomagnetic polarity epochs: new data from Olduvai Gorge, Tanganyika

    USGS Publications Warehouse

    Gromme, C.S.; Hay, R.L.

    1967-01-01

    The lower lava flow of Bed I in Olduvai Gorge, Tanganyika, carries natural remanent magnetization (NRM) having normal polarity. Thermal demagnetization experiments demonstrate the stability of this NRM. Thus the Olduvai geomagnetic polarity event, which was originally named from the upper lava flow in Bed I, is represented in its type locality by two normally magnetized lavas. These lavas have been shown to be 1.9 m.y. old, and although they are distinct from each other in composition and surface structure, their eruptions appear to have been closely spaced in time. ?? 1967.

  11. Nighttime ionosphere thermosphere coupling observed during an intense geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Fagundes, P. R.; Muella, M. T. A. H.; Bittencourt, J. A.; Sahai, Y.; Lima, W. L. C.; Guarnieri, F. L.; Becker-Guedes, F.; Pillat, V. G.; Ferreira, A. S.; Lima, N. S.

    The electrodynamics of the ionosphere in the tropical region presents various scientific aspects, which remain subject of intensive investigations and debates by the scientific community. During the year 2002, in a joint project between the Universidade do Vale do Paraíba (UNIVAP) and Universidade Luterana do Brasil (ULBRA), a chain of three Canadian Advanced Digital Ionosondes (CADIs) was established nearly along the geomagnetic meridian direction, for tropical ionospheric studies, such as, changes and response due to geomagnetic disturbances and thermosphere ionosphere coupling and the generation and dynamics of ionospheric irregularities, in the Brazilian sector. The locations of the three ionosondes stations are São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S under the southern crest of equatorial ionospheric anomaly), Palmas (10.2°S, 48.2°W, dip latitude 5.5°S near the magnetic equator) and Manaus (2.9°S, 60.0°W, dip latitude 6.4°N between the geographic and geomagnetic dip equators). It should be pointed out that Palmas and Manaus are located on the opposite sides of the magnetic equator but both are south of the geographic equator. The three CADIs work in time-synchronized mode and obtain ionograms every 5 min. This configuration of the ionospheric sounding stations allowed us to study the F-region dynamics during geomagnetically disturbed period in the meridional direction. Just after the installation and testing of the three CADIs, on September 05, 2002 a coronal mass ejection (CME) left the Sun and about 2 days after the CME left the Sun, it reached the Earth’s magnetosphere and complex and multi step events took place during the period September 07 09. In the study we note that the equatorial stations located north (Manaus, dip latitude 6.4°N) and south (Palmas, dip latitude 5.5°S) of the dip equator presented significant F-layer height asymmetries during the storm main phase. In addition, the low-latitude station SJC (dip latitude 17.6°S) presented decrease in the F-layer densities (negative phase), whereas Palmas presented increase in the F-layer densities (positive phase) during the main phase. This was followed by positive phase at both the stations. During the first night of the recovery phase a strong formation and evolution of large-scale ionospheric irregularities (equatorial spread-F (ESF)) was observed, but on the second night of the recovery phase, there was strong and almost simultaneous sporadic E (Es) formation at all three stations. During the presence of Es, spread-F formation is not observed, indicating the suppression of spread-F, possibly by sporadic E.

  12. Influence of geomagnetic perturbation on resonant gravitational wave detector

    E-print Network

    Ianovski, V; Ianovski, Valeri; Okunev, Igor

    1996-01-01

    The level of background signals in modern cryogenic resonant mass gravitational wave antenna is discussed caused by (a) the geomagnetic field pulsations and (b) an atmosferic of very low frequency band, generated by a lightning flash. The analysis of our results show that the signals of this origin will generally exceed the signals from the gravitational wave sources. To suppress these artifacts in such gravitational antenna, it is necessary to use the magnetometer included as anti-coincidence protection and a system of magnetic screens.

  13. Latitude dependence of long-term geomagnetic activity and its solar wind drivers

    NASA Astrophysics Data System (ADS)

    Myllys, M.; Partamies, N.; Juusola, L.

    2015-05-01

    To validate the usage of global indices in studies of geomagnetic activity, we have examined the latitude dependence of geomagnetic variations in Fennoscandia and Svalbard from 1994 to 2010. Daily standard deviation (SD) values of the horizontal magnetic field have been used as a measure of the ground magnetic disturbance level. We found that the timing of the geomagnetic minimum depends on the latitude region: corresponding to the minimum of sunspot cycle 22 (in 1996), the geomagnetic minimum occurred between the geomagnetic latitudes 57-61° in 1996 and at the latitudes 64-67° in 1997, which are the average auroral oval latitudes. During sunspot cycle 23, all latitude regions experienced the minimum in 2009, a year after the sunspot minimum. These timing differences are due to the latitude dependence of the 10 s daily SD on the different solar wind drivers. In the latitude region of 64-67°, the impact of the high-speed solar wind streams (HSSs) on the geomagnetic activity is the most pronounced compared to the other latitude groups, while in the latitude region of 57-61°, the importance of the coronal mass ejections (CMEs) dominates. The geomagnetic activity maxima during ascending solar cycle phases are typically caused by CME activity and occur especially in the oval and sub-auroral regions. The strongest geomagnetic activity occurs during the descending solar cycle phases due to a mixture of CME and HSS activity. Closer to the solar minimum, less severe geomagnetic activity is driven by HSSs and mainly visible in the poleward part of the auroral region. According to our study, however, the timing of the geomagnetic activity minima (and maxima) in different latitude bands is different, due to the relative importance of different solar wind drivers at different latitudes.

  14. Linear filters as a method of real-time prediction of geomagnetic activity

    SciTech Connect

    McPherron, R.L.; Baker, D.N.; Bargatze, L.F.

    1985-01-01

    Important factors controlling geomagnetic activity include the solar wind velocity, the strength of the interplanetary magnetic field (IMF), and the field orientation. Because these quantities change so much in transit through the solar wind, real-time monitoring immediately upstream of the earth provides the best input for any technique of real-time prediction. One such technique is linear prediction filtering which utilizes past histories of the input and output of a linear system to create a time-invariant filter characterizing the system. Problems of nonlinearity or temporal changes of the system can be handled by appropriate choice of input parameters and piecewise approximation in various ranges of the input. We have created prediction filters for all the standard magnetic indices and tested their efficiency. The filters show that the initial response of the magnetosphere to a southward turning of the IMF peaks in 20 minutes and then again in 55 minutes. After a northward turning, auroral zone indices and the midlatitude ASYM index return to background within 2 hours, while Dst decays exponentially with a time constant of about 8 hours. This paper describes a simple, real-time system utilizing these filters which could predict a substantial fraction of the variation in magnetic activity indices 20 to 50 minutes in advance.

  15. Correlations between sunspot numbers, interplanetary parameters and geomagnetic trends over solar cycles 21-23

    NASA Astrophysics Data System (ADS)

    Arora, Kusumita; Chandrasekhar, N. Phani; Nagarajan, Nandini; Singh, Ankit

    2014-07-01

    We have analysed correlations between sunspot numbers, solar wind, ion density, interplanetary magnetic field vis-à-vis magnetic activity. Planetary geomagnetic index (Ap) and local residual measure of magnetic activity (I?H) from low-latitude Magnetic Observatory, CSIR-NGRI, Hyderabad (IMO-HYB) spanning solar cycles 21-23 are used for this study. Using correlation coefficients between and wavelet decomposition of sunspot numbers, interplanetary parameters and measures of magnetic activity, the complex and time varying nature of these inter-relationships are brought out. The overall influence of sunspot number could be separated and combined episodic effects of other solar parameters could be distinguished. The demonstrated correlation or lack of it, between measures of magnetic activity (Ap and I?H), and all the parameters of solar activity, presented here corroborate established mechanisms as well as delineated clearly the relative impact of different solar mechanisms over phases of three solar cycles. The possible role of non-sunspot related activity from high latitude regions of the sun is indicated.

  16. Jung Index

    NSDL National Science Digital Library

    1999-01-01

    Compiled by Matthew Clapp of the University of Georgia, the Jung Index is a collection of more than 300 online resources about and related to the life and work of Carl Jung, the Swiss psychologist and psychiatrist who founded analytic psychology. Resources are indexed into ten major topic areas and include sections such as Research Resources, Jungian Psychology, and Psychoanalysis, among others. A What's New? section, a What's Cool? section, and the JungNet Newsletter keep frequent visitors up to date on the latest and greatest resources in analytic psychology. In addition, the site provides a glossary of Jungian terms, a gallery of Jungian images, and a moderated forum for Jungian discussion.

  17. Auroral particle instrument onboard the INDEX satellite

    NASA Astrophysics Data System (ADS)

    Asamura, K.; Tsujita, D.; Tanaka, H.; Saito, Y.; Mukai, T.; Hirahara, M.

    The INDEX satellite is a microsatellite which will be inserted into a low-altitude (650-800km) polar orbit by an H2A rocket as a piggyback payload. A low-energy plasma particle instrument, which consists of two sensor heads (ion/electrons sensors; ISA/ESA), and a multi-spectral auroral camera (MAC) will be installed in the INDEX in order to investigate formation mechanisms of fine-scale structures of optical auroral arc emissions. Because of the low-altitude orbit, the satellite velocity is relatively fast (7.5km/s). A high time-resolution, therefore, is necessary for the plasma measurement. The time resolution of the plasma instruments onboard the INDEX is 20ms, which corresponds to a spatial scale of 150m. The sensor heads are top-hat type analyzers with a planar field-of-view (FOV) which can cover basically 360 degrees in the azimuthal direction in case of no obstacles. Therefore, during the measurements, the attitude of the satellite will be controlled to include a geomagnetic field line within the planar FOV of the plasma instruments. At the same time with the auroral particle observations, the FOV of the optical auroral camera will be pointed to a footprint of the corresponding geomagnetic field line. In this case, pitch-angle distributions of auroral particles can be obtained with the time resolution determined only by a period of internal energy scan, namely, 20ms. Since the instrument is designed to perform the measurement of high-time resolution, the instrument should be able to handle the high count rate. For this purpose, we apply an MCP detector with a position sensitive anode on the basis of a measurement of signal transmission time on the anode pattern. With this detector system, the instrument can handle 106 -107 counts per second.

  18. Reconstructing the Geomagnetic Field of the Past 10 kyrs

    NASA Astrophysics Data System (ADS)

    Korte, M. C.; Constable, C.; Holme, R.; Donadini, F.; Frank, U.

    2009-12-01

    We present an extension of spherical harmonic field reconstructions of the geomagnetic field to span the past 10 kyrs. The new model follows the strategy used in our earlier models CALS3k.3 and CALS7K.2 for the past 3 and 7 kyrs respectively. However, we have introduced some improvements to the method, and the data coverage is better. About 10 new sedimentary sequences are included. Tests with similarly distributed synthetic data indicate that it is possible to recover large-scale field evolution over 10 kyrs. The reliability of archeo- and paleomagnetic data depends not only on the data quality, but also on the accuracy of dating. It is not straightforward to take age uncertainties into account in the modeling, and for our new model we estimated the contribution of age uncertainty to data uncertainty by evaluating local secular variation based on a pilot model. Characteristic geomagnetic field features revealed by the model are discussed, including dipole strength, motion of the dipole axis and changes in field morphology at the core-mantle boundary.

  19. Thermosphere Response to Geomagnetic Variability during Solar Minimum Conditions

    NASA Astrophysics Data System (ADS)

    Forbes, Jeffrey; Gasperini, Federico; Zhang, Xiaoli; Doornbos, Eelco; Bruinsma, Sean; Haeusler, Kathrin; Hagan, Maura

    2015-04-01

    The response of thermosphere mass density to variable geomagnetic activity at solar minimum is revealed as a function of height utilizing accelerometer data from GRACE near 480 km, CHAMP near 320 km, and GOCE near 260 km during the period October-December, 2009. The GOCE data at 260 km, and to some degree the CHAMP measurements at 320 km, reveal the interesting feature that the response maximum occurs at low latitudes, rather than at high latitudes where the geomagnetic energy input is presumed to be deposited. The latitude distribution of the response is opposite to what one might expect based on thermal expansion and/or increase in mean molecular weight due to vertical transport of N2 at high latitudes. We speculate that what is observed reflects the consequences of an equatorward meridional circulation with downward motion and compressional heating at low latitudes. A numerical simulation using the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Mesosphere Electrodynamics General Circulation Model (TIME-GCM) is used to assist with this diagnosis. At 480 km GRACE reveals maximum density responses at high southern (winter) latitudes, consistent with recent interpretations in terms of compositional versus temperature effects near the oxygen-helium transition altitude during low solar activity.

  20. Ionospheric Effects Observed by Radio Tomography during Severe Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Andreeva, Elena S.; Kunitsyn, Vyacheslav E.; Tereshchenko, Evgeniy D.; Nazarenko, Marina O.; Nesterov, Ivan A.; Tumanova, Yuila S.

    2014-05-01

    The geomagnetic storms are an important element of space weather. As known, the distributions of all ionospheric parameters are determined by the interplay of many complex diverse processes of solar-terrestrial coupling. The intervals of geomagnetic storms are marked by dramatic changes in the dynamics of the ionosphere, whose parameters experience significant disturbances. The ionospheric signatures of geomagnetic perturbations are highly diverse in both spatiotemporal scales, ranging from a few seconds to few days and from a few meters to dozen thousand kilometers, and intensity. The methods of GNSS-based radio tomography (RT) are suitable for diagnosing the spatiotemporal structure of ionospheric disturbances caused by different space-weather factors. GNSS comprise the first-generation satellite navigation systems such as low-orbiting (LO) Russian Tsikada and American Transit satellites and second-generation satellite systems such as high-orbiting GPS and GLONASS constellations. The LORT methods reconstruct two-dimensional (2D) structure of the ionospheric electron density distribution in the vertical (altitude-latitude) plane within a spatial sector spanning a few thousand km and a time interval of 10-15 min. The horizontal and vertical resolution of LORT is typically 15-25 km and 25-30 km, respectively. The HORT methods use radio transmissions from HO satellites recorded at the receiving ground network of the International Geodetic Service (IGS), which currently comprises about 2000 receivers. The HORT methods are capable of reconstructing the four-dimensional (4D) (three spatial coordinates and time) structure of the ionosphere. Generally, HORT has a spatial resolution of 100 km at best and a time step of 60-20 min. In the regions covered by dense receiving networks (e.g., in Europe, Alaska, USA), the resolution can be improved to 30-50 and the time step reduced to 30-10 min. The resolution of 10-30 km in space and up to 2 min in time is only achievable in Japan and California, where the receiving networks are very dense. We present the results of HORT and LORT imaging of the ionosphere during the periods of geomagnetic storms of 2003-2013 in different regions of the world -- in the European part of Russia and North America. Different factors acting during the storm time make the ionosphere complexly structured. Radio tomography reveals multi-extremal distributions of the ionospheric plasma with the spots of enhanced ionization, wall-like steep gradients of electron concentration; a complex structure of the ionization trough with the polar wall shifted equatorwards is observed. Many reconstructions show various wavelike structures, travelling ionospheric disturbances, wave effects caused by corpuscular emissions, etc. We demonstrate the comparisons of radio tomography with the ionosonde measurements. In contrast to the ionosondes, which use short radio waves, the RT methods are suitable for diagnosing the ionosphere even during the periods of strong geomagnetic storms, since absorption can typically be neglected in the RT problems due to the high frequencies used. The work was supported by the Russian Foundation for Basic Research (grants 14-05-00855 and 13-05-01122). We are grateful to the North-West Research Associates (NWRA) for providing the experimental relative TEC data from the RT system in Alaska.

  1. Population Index

    NSDL National Science Digital Library

    Two excellent bibliographic resources for population studies are the "Population Index" from the Office of Population Research at Princeton University, and "Population Organizations: Finder's Guide" from the Center for Demography and Ecology at the University of Wisconsin-Madison. "Population Index" is a quarterly publication that has been available since 1935. It "covers all fields of interest to demographers, including fertility, mortality, population size and growth, migration, nuptiality and the family, research methodology, projections and predictions, historical demography, and demographic and economic interrelations. Input is derived from original publications including monographs, journal articles, other serial publications, working papers, doctoral dissertations, machine-readable data files, and relevant acquisitions lists and bibliographies." About 3,500 citations are produced annually. Full text for the Index is available at the "Population Index" Web site for 1986-present (Vol. 52-present). Indexes can be searched by author, subject matter, geographical region, or publication year. There is now an experimental free text search capability for the 1994-present issues. "Population Organizations: Finder's Guide" is a no frills "practical tool for population professionals who need a single source for the quick location of organizations that publish and distribute or post population or family planning documents." It contains hundreds of citations, providing organization addresses, phone and FAX numbers, and Internet addresses when available. The Guide is updated every six months and is maintained by Ruth Sandor, Director of the Library of the Center for Demography and Ecology. Office of Population Research, Princeton University: http://opr.princeton.edu/ "Population Organizations: Finder's Guide": gopher://cde2.ssc.wisc.edu:70/00/addazlis gopher to: cde2.ssc.wisc.edu select: Population Organizations: Finder's Guide Center for Demography and Ecology, University of Wisconsin-Madison: http://www.ssc.wisc.edu/cde/

  2. Information Theory Approach to Evaluate the Geomagnetic and Ionospheric Response to Solar Wind Parameters

    NASA Astrophysics Data System (ADS)

    Seemala, G. K.; R, S.; Bhaskara, V.; Ramesh, D. S.

    2014-12-01

    The importance of space weather and understanding onset o geomagnetic storms is increasing day by day as the space missions increase. It is known from the ground-based and space-borne observations that a geomagnetic storm is a temporary disturbance of earth's magnetosphere caused by a solar wind and/or solar eruptions. Geomagnetic storms are more disruptive now than in the past because of our greater dependence on technical systems that can be affected by electric currents and energetic particles high in the Earth's magnetosphere. It is known that number of phenomena occurs during the space weather events; and there are many un-solved questions like solar wind coupling with magnetosphere and ionosphere, relationship between geomagnetic storms & sub-storms etc. To evaluate contribution of various interplanetary parameters that have major role in the geomagnetic storm/geomagnetic variations, the information theory approach is used. In information theory, the measure of uncertainty or randomness of a signal can be quantified by using Shannon entropy or entropy for short. And Transfer entropy is capable of quantifying the directional flow of information between two signals. Thus the Transfer entropy is capable of distinguishing effectively driving and responding signals. In this study, we use Transfer entropy function on Solar wind parameters and ground magnetic data to derive the drivers and relations between them, and also study their contributed effect on ionospheric TEC. In this presentation, we will evaluate and present the results obtained, and discuss about the driving forces on the geomagnetic field disturbances.

  3. Compass roses on the Book of Navigation ( Kitab-? Bahriye): Declination data source for geomagnetic field models

    NASA Astrophysics Data System (ADS)

    Yilmaz, Ibrahim; Gullu, Mevlut; Yilmaz, Mustafa; Dereli, Mehmet A.

    2010-10-01

    The Earth is surrounded by a geomagnetic field that is generated by dynamo processes in the core like a gigantic magnet. The Earth's geomagnetic field shifts with time and location. There has been a comprehensive effort for modelling the geomagnetic field of the Earth at regional and global scales by several researchers in the recent decades. The magnetic data from historical sources have a great importance in geomagnetic field modelling. The declination was the first measured geomagnetic field element with the early use of compasses for navigation. In this study the declination values estimated from compass roses drawn on the Book of Navigation ( Kitab-? Bahriye) that are georeferenced by an artificial neural network are compared to the declination values based on the geomagnetic field models CALS3K.3 and SCHA.DIF.3K. The results show that the compass roses drawn on the portolan charts of Kitab-? Bahriye can be used as declination data sources for regional or global geomagnetic field models.

  4. Effects on the geomagnetic tail at 60 earth radii of the geomagnetic storm of April 9, 1971.

    NASA Technical Reports Server (NTRS)

    Burke, W. J.; Rich, F. J.; Reasoner, D. L.; Colburn, D. S.; Goldstein, B. E.

    1973-01-01

    A geomagnetic storm beginning with an sc occurred on Apr. 9, 1971. During the storm the charged particle lunar environment experiment at the Apollo 14 site, the solar wind spectrometer experiment at the Apollo 12 site, and the Ames magnetometers on Explorer 35 took data in the magnetosheath, at the magnetopause, in the plasma sheet, and in the high-latitude geomagnetic tail. The MIT Faraday cup and Ames magnetometers on board Explorer 33 monitored the solar wind. The data show that the storm was caused by a corotating tangential discontinuity in the solar wind, the magnetopause position is strongly dependent on the attack angle of the solar wind, and the tail field strength was indirectly measured to increase from 10 to 14 gamma after the sc. During the main phase the field strength in the tail was observed to increase to between 28 and 34 gamma. This increase is consistent with a thermal and magnetic compression of the tail radius from about 26 to about 16 earth radii.

  5. Fourier power spectra of the geomagnetic field for circular paths on the Earth's surface.

    USGS Publications Warehouse

    Alldredge, L.R.; Benton, E.R.

    1986-01-01

    The Fourier power spectra of geomagnetic component values, synthesized from spherical harmonic models, have been computed for circular paths on the Earth's surface. They are not found to be more useful than is the spectrum of magnetic energy outside the Earth for the purpose of separating core and crustal sources of the geomagnetic field. The Fourier power spectra of N and E geomagnetic components along nearly polar great circle paths exhibit some unusual characteristics that are explained by the geometric perspective of Fourier series on spheres developed by Yee. -Authors

  6. Relevance of geomagnetic storms to relativistic electron flux enhancements at geosynchronous orbit

    NASA Astrophysics Data System (ADS)

    Kim, H. J.; Pinto, V. A.; Wang, C. P.; Lyons, L. R.

    2014-12-01

    While examining why only some geomagnetic storms accompany relativistic electron flux enhancements, we found evidence that storms are indeed irrelevant to the occurrence of large flux enhancement at geosynchronous orbit. With the analysis of solar wind parameters and >2MeV geosynchronous electron fluxes, we identify the solar wind conditions that are critical for the large flux enhancements. Along with the observations of flux enhancements without a geomagnetic storm, the observations that only the geomagnetic storms that are associated with such characteristic solar wind conditions accompany the flux enhancements indicate that a storm itself is irrelevant to the occurrence of flux enhancements.

  7. [The behavior of male Danio rerio after exposure of fish embryos to a simulated geomagnetic storm].

    PubMed

    Romanovski?, A V; Pesnia, D S; Izvekov, E I; Krylov, V V; Nepomniashchikh, V A

    2014-01-01

    Embryos of the zebrafish, Danio rerio, were exposed to a simulated geomagnetic storm during 24 hours. Fish, developed from these embryos, left a start chamber to an aquarium more readily in comparison to those reared in a normal geomagnetic field. On the other hand, general locomotor activity in fish was not essentially different between the two groups. We hypothesize that an exposure to a geomagnetic storm during embryonic period results in enhanced tolerance to stress caused by a novel environment. A low level stress is in turn a subject to further exploration. PMID:25715624

  8. Do geomagnetic storms change the behaviour of the stingless bee guiruçu ( Schwarziana quadripunctata)?

    NASA Astrophysics Data System (ADS)

    Esquivel, Darci M. S.; Wajnberg, E.; Do Nascimento, F. S.; Pinho, M. B.; de Barros, H. G. P. Lins; Eizemberg, R.

    2007-02-01

    Six behavioural experiments were carried out to investigate the magnetic field effects on the nest-exiting flight directions of the honeybee Schwarziana quadripunctata ( Meliponini). No significant differences resulted during six experiment days under varying geomagnetic field and the applied static inhomogeneous field (about ten times the geomagnetic field) conditions. A surprising statistically significant response was obtained on a unique magnetic storm day. The magnetic nanoparticles in these bees, revealed by ferromagnetic resonance, could be involved in the observed effect of the geomagnetic storm.

  9. Corotating solar wind streams and recurrent geomagnetic activity: A review

    NASA Astrophysics Data System (ADS)

    Tsurutani, Bruce T.; Gonzalez, Walter D.; Gonzalez, Alicia L. C.; Guarnieri, Fernando L.; Gopalswamy, Nat; Grande, Manuel; Kamide, Yohsuke; Kasahara, Yoshiya; Lu, Gang; Mann, Ian; McPherron, Robert; Soraas, Finn; Vasyliunas, Vytenis

    2006-07-01

    Solar wind fast streams emanating from solar coronal holes cause recurrent, moderate intensity geomagnetic activity at Earth. Intense magnetic field regions called Corotating Interaction Regions or CIRs are created by the interaction of fast streams with upstream slow streams. Because of the highly oscillatory nature of the GSM magnetic field z component within CIRs, the resultant magnetic storms are typically only weak to moderate in intensity. CIR-generated magnetic storm main phases of intensity Dst < -100 nT (major storms) are rare. The elongated storm "recovery" phases which are characterized by continuous AE activity that can last for up to 27 days (a solar rotation) are caused by nonlinear Alfven waves within the high streams proper. Magnetic reconnection associated with the southward (GSM) components of the Alfvén waves is the solar wind energy transfer mechanism. The acceleration of relativistic electrons occurs during these magnetic storm "recovery" phases. The magnetic reconnection associated with the Alfvén waves cause continuous, shallow injections of plasma sheet plasma into the magnetosphere. The asymmetric plasma is unstable to wave (chorus and other modes) growth, a feature central to many theories of electron acceleration. It is noted that the continuous AE activity is not a series of substorm expansion phases. Arguments are also presented why these AE activity intervals are not convection bays. The auroras during these continuous AE activity intervals are less intense than substorm auroras and are global (both dayside and nightside) in nature. Owing to the continuous nature of this activity, it is possible that there is greater average energy input into the magnetosphere/ionosphere system during far declining phases of the solar cycle compared with those during solar maximum. The discontinuities and magnetic decreases (MDs) associated with interplanetary Alfven waves may be important for geomagnetic activity. In conclusion, it will be shown that geomagnetic storms associated with high-speed streams/CIRs will have the same initial, main, and "recovery" phases as those associated with ICME-related magnetic storms but that the interplanetary causes are considerably different.

  10. AA-CSIA-derived Regional Comparison

    E-print Network

    Hawai'i at Manoa, University of

    @hawaii.edu) Brian N. Popp Jeffrey C. Drazen Elizabeth Gier, Peter Davidson, Adrian Flynn, Joel Hoffman, Jennifer McClain, Todd Miller, Steve Ross, Tracey Sutton© MBARI #12;What is the AA-CSIA method? Compound-specific isotope

  11. Two successful geomagnetic-field-line tracing experiments.

    NASA Technical Reports Server (NTRS)

    Wescott, E. M.; Nielsen, H. C. S.; Murcray, W. B.; Davis, T. N.; Peek, H. M.; Jensen, R. J.

    1972-01-01

    Two field-line tracing experiments were conducted on an L = 1.26 magnetic flux tube over Kauai, Hawaii. Barium vapor was created by the detonation of a highly explosive shaped charge aligned with the geomagnetic field at a 467-km altitude. Barium ions traveled along the field line to the conjugate ionosphere in a tube 3 to 5 km in diameter, producing a visible streak along the entire 6900-km path length. Electric fields perpendicular to the magnetic field caused the ions to drift away from the true conjugate during transit, but extrapolation from subsequent ion drift rates allowed the conjugate to be identified and compared with several field models. Differing ion drift rates and directions at the conjugate points indicated that the electric field is not transferred unattenuated along field lines.

  12. Geomagnetic Field Effects on the Imaging Air Shower Cherenkov Technique

    NASA Astrophysics Data System (ADS)

    Commichau, S. C.; Biland, A.; Kranich, D.; et al.

    Imaging Air Cherenkov Telescopes (IACTs) detect the Cherenkov light flashes of Extended Air Showers (EAS) triggered by VHE gamma-rays impinging on the Earth's atmosphere. Due to the overwhelming background from hadron induced EAS, the discrimination of the rare gamma-like events is rather difficult, in particular at energies below 100 GeV. The influence of the Geomagnetic Field (GF) on the EAS development can further complicate this discrimination and, in addition, also systematically affect the gamma-efficiency and energy resolution of an IACT. Here we present the results from dedicated Monte Carlo (MC) simulations for the MAGIC telescope site, show the GF effects on real data as well as possible corrections for these effects.

  13. Effects of dipole tilt angle on geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Nowada, M.; Shue, J.-H.; Russell, C. T.

    2009-09-01

    The relationship between the orientation of the interplanetary magnetic field (IMF), represented by the clock angle which is the angle defined by IMF-By and -Bz components, and the AL and AU indices is examined at various dipole tilt angles for the period of 1978-1988. We use the IMF data obtained from the IMP 8 satellite, AL and AU indices with corrected seasonal variations, and the dipole tilt angle, which is the dipole magnetic latitude of the subsolar point calculated as a function of the day of year and universal time. For both positive (dipole tilted to the Sun) and negative dipole tilt angles, the values of |AL| and AU decrease as the IMF clock angle moves away from 180?, becoming more northward. The indices also tend to become smaller for larger dipole tilt angle, either toward or away from the Sun. This dependence on dipole tilt angle enhances the semiannual variation of geomagnetic activity.

  14. A new trajectory concept for exploring the earth's geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Farquhar, R. W.; Dunham, D. W.

    1981-01-01

    An innovative trajectory technique for a magnetotail mapping mission is described which can control the apsidal rotation of an elliptical earth orbit and keep its apogee segment inside the tail region. The required apsidal rotation rate of approximately 1 deg/day is achieved by using the moon to carry out a prescribed sequence of gravity-assist maneuvers. Apogee distances are alternately raised and lowered by the lunar-swingby maneuvers; several categories of the 'sun-synchronous' swingby trajectories are identified. The strength and flexibility of the new trajectory concept is demonstrated by using real-world simulations showing that a large variety of trajectory shapes can be used to explore the earth's geomagnetic tail between 60 and 250 R sub E.

  15. A new trajectory concept for exploring the earth's geomagnetic tail

    NASA Astrophysics Data System (ADS)

    Farquhar, R. W.; Dunham, D. W.

    1981-04-01

    An innovative trajectory technique for a magnetotail mapping mission is described which can control the apsidal rotation of an elliptical earth orbit and keep its apogee segment inside the tail region. The required apsidal rotation rate of approximately 1 deg/day is achieved by using the moon to carry out a prescribed sequence of gravity-assist maneuvers. Apogee distances are alternately raised and lowered by the lunar-swingby maneuvers; several categories of the 'sun-synchronous' swingby trajectories are identified. The strength and flexibility of the new trajectory concept is demonstrated by using real-world simulations showing that a large variety of trajectory shapes can be used to explore the earth's geomagnetic tail between 60 and 250 R sub E.

  16. Study of Ring Current Dynamics During Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Jordanova, Vania K.

    2000-01-01

    This research program considered modeling the dynamical evolution of the ring current during several geomagnetic storms. The first year (6/01/1997-5/31/1998) of this successful collaborative research between the University of New Hampshire (UNH) and the University of California Los Angeles (UCLA) was supported by NASA grant NAG5-4680. The second and third years (6/01/1998-5/31/2000) were funded at UNH under NASA grant NAG5-7368. Research work at UNH concentrated on further development of a kinetic model to treat all of the important physical processes that affect the ring current ion population during storm conditions. This model was applied to simulate ring current development during several International Solar-Terrestrial Physics (ISTP) events, and the results were directly compared to satellite observations. A brief description of our major accomplishments and a list of the publications and presentations resulting from this effort are given.

  17. UT variations of geomagnetic activity as a basis for understanding the magnetic state and dynamics of planetary magnetospheres

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T.; Laptukhov, A.

    This paper deals with the effect of the mutual orientation of the vectors of the dipole magnetic moment, the IMF and the solar wind electric field on the terrestrial magnetosphere in case of the reconnection between the dipole magnetic field and an IMF of arbitrary orientation. Our results can be applied to any magnetosphere, when analyzing the data measured in vicinity of the planets. Results of studies of UT variations of geomagnetic activity are still controversial. We examine the UT variations in Kp index for the period from 1964-1996. We are concerned with not only the UT variation but also how it is controlled by the solar wind and IMF and use the IMF and plasma data for the same period. We attract for the studies a reconnection model elaborated by us. The mo el describes a reconnection betweend the Earth's magnetic field and an IMF of arbitrary orientation taking into account annual and daily motions of the Earth. We use the data to study invariant parameters (independent from a choice of a coordinate system) derived from our model that determine the reconnection. 1)cos(BM), where (BM) is angle between vectors of the IMF B and geomagnetic moment M; 2)vector of electric field of the solar wind E presented by its projections along and across the M vector (Em and Emv). Functional relation of mean Kp-index and cos(BM) is obtained from the analyzed data. The correlation coefficient Cc=0.98 between the data from different years. The Kp has functional dependencies with the parameters Em and Emv too; Cc have the same high values from year to year. These parameters calculated from the data for 33 years taking into account the UT orientation of the vectors show clearly that geomagnetic activity has essential repeated component. Derived functions Kp=F(Emv) and Kp=f(Em) (Kp changes from 0 to 9) show essentially different behavior and differs from the discussed earlier. We use the derived connections for our analysis of the UT course in Kp (daily and annual). Special study was done to quantitative valuations of different mechanisms suggested earlier. We study effectiveness of the models that explain the UT variations on the angle between the Earth's dipole and the solar wind velocity, these variations give 10-15%; the evaluation of effect of Russell and McPherron is presented too. Our parameter cos(BM) can account for 50-60% variations of Kp (in all range of Kp changes: 0-9). The other model parameters Em and Emv explain changes in Kp up to its maximal value 9. The other results concerning the UT variations of geomagnetic activity, its influence on magnetosphere state and dynamics are presented and discussed.

  18. Origins of the Wolf Sunspot Number Series: Geomagnetic Underpinning

    NASA Astrophysics Data System (ADS)

    Cliver, E. W.; Svalgaard, L.

    2007-12-01

    The Wolf or International sunspot number (SSN) series is based on the work of Swiss astronomer Rudolf Wolf (1816-1893). Following the discovery of the sunspot cycle by Schwabe in 1843, Wolf culled sunspot counts from journals and observatory reports and combined them with his own observations to produce a SSN series that extended from 1700-1893. Thereafter the SSN record has been maintained by the Zurich Observatory and, since 1981, by the Royal Observatory of Belgium. The 1700-1893 SSN record constructed by Wolf has not been modified since his death. Here we show that Wolf's SSNs were not based solely on reports of sunspots but were calibrated by reference to geomagnetic range observations which closely track the sunspot number. Nor were these corrections small; for example Wolf multiplied the long series (1749-1796) of sunspot counts obtained by Staudacher by factors of 2.0 and 1.25, in turn, to obtain the numbers in use today. It is not surprising then that a competing SSN series obtained by Hoyt and Schatten based on group sunspot numbers is different, generally lower than that of Wolf. Comparison of the International number with current magnetic range observations indicates that, as Wolf found, the magnetic range (specifically, the average annual Y-component of mid-latitude stations) can be used as an independent check on the validity and stability of the SSN series. Moreover, the geomagnetic range series, which in itself is a long-term proxy of solar EUV emission, can be used to resolve discrepancies between the Wolf and Group SSN series during the 19th century.

  19. Comparison of methods for modelling geomagnetically induced currents

    NASA Astrophysics Data System (ADS)

    Boteler, D. H.; Pirjola, R. J.

    2014-09-01

    Assessing the geomagnetic hazard to power systems requires reliable modelling of the geomagnetically induced currents (GIC) produced in the power network. This paper compares the Nodal Admittance Matrix method with the Lehtinen-Pirjola method and shows them to be mathematically equivalent. GIC calculation using the Nodal Admittance Matrix method involves three steps: (1) using the voltage sources in the lines representing the induced geoelectric field to calculate equivalent current sources and summing these to obtain the nodal current sources, (2) performing the inversion of the admittance matrix and multiplying by the nodal current sources to obtain the nodal voltages, (3) using the nodal voltages to determine the currents in the lines and in the ground connections. In the Lehtinen-Pirjola method, steps 2 and 3 of the Nodal Admittance Matrix calculation are combined into one matrix expression. This involves inversion of a more complicated matrix but yields the currents to ground directly from the nodal current sources. To calculate GIC in multiple voltage levels of a power system, it is necessary to model the connections between voltage levels, not just the transmission lines and ground connections considered in traditional GIC modelling. Where GIC flow to ground through both the high-voltage and low-voltage windings of a transformer, they share a common path through the substation grounding resistance. This has been modelled previously by including non-zero, off-diagonal elements in the earthing impedance matrix of the Lehtinen-Pirjola method. However, this situation is more easily handled in both the Nodal Admittance Matrix method and the Lehtinen-Pirjola method by introducing a node at the neutral point.

  20. Nighttime thermospheric-ionospheric coupling during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Fagundes, P. R.; Muella, M. T. A. H.; Bittencourt, J. A.; Sahai, Y.; Lima, W. L. C.; Becker-Guedes, F.; Pillat, V. G.

    The electrodynamics of the ionosphere in the tropical region presents various scientific aspects which remain subject of intensive investigations and debates by the scientific community During the year 2002 in a joint project between Universidade do Vale do Para i ba UNIVAP and Universidade Luterana do Brasil ULBRA a chain of three Canadian Digital Ionosondes CADIs was established nearly along the geomagnetic meridian direction for tropical ionospheric studies such as the generation and dynamics of ionospheric irregularities changes and response due to geomagnetic disturbances and thermosphere-ionosphere coupling in the Brazilian sector The locations of the three ionosonde stations are S a o Jos e dos Campos 23 2 o S 45 9 o W dip latitude 17 6 o S - under the Equatorial Ionospheric Anomaly Palmas 10 2 o S 48 2 o W dip latitude 5 5 o S -- near the magnetic equator and Manaus 2 9 o S 60 0 o W dip latitude 6 4 o N -- near the magnetic equator It should be pointed out that Palmas and Manaus are located on opposite side of the magnetic equator but both are south of the geographic equator The three CADIs work in time-synchronized mode and obtain ionograms every 5 minutes This unique configuration of the ionospheric sounding stations allowed us to study the F-region dynamics during disturbed periods in the months of August and September 2002 Then an extension of the servo model was used to infer the magnetic meridional component of the thermospheric neutral winds over the low latitude

  1. Calibration of historical geomagnetic observations from Prague-Klementinum

    NASA Astrophysics Data System (ADS)

    Hejda, Pavel

    2015-04-01

    The long tradition of geomagnetic observations on the Czech territory dates back to 1839, when regular observations were started by Karl Kreil at the Astronomical Observatory Prague-Klementinum. Observations were carried out manually, at the beginning more than ten times per day and the frequency later decreased to 5 daily observations. Around the turn of century the observations became to be disturbed by the increasing urban magnetic noise and the observatory was closed down in 1926. The variation measurements were completed by absolute measurements carried out several times per year. Thanks to the diligence and carefulness of Karl Kreil and his followers all results were printed in the yearbooks Magnetische und meteorologische Beobachtungen zu Prag and have thus been saved until presence. The entire collection is kept at the Central Library of the Czech Academy of Sciences. As the oldest geomagnetic data have been recently recognized as an important source of information for Space Weather studies, digitization and analysis of the data have been now started. Although all volumes have been scanned with the OCR option, the low quality of original books does not allow for an automatic transformation to digital form. The data were typed by hand to Excel files with a primary check and further processed. Variation data from 1839 to 1871 were published in measured units (scales of divisions). Their reduction to physical units was not as straight forward as we are used in recent observatories. There were several reasons: (i) the large heavy magnetic rods were not as stable as recent systems, (ii) the absolute measurements of horizontal components were carried out by the genius but rather complicated Gauss method, (iii) the intervals between absolute measurements was on the scale of months and eventual errors were not recognized timely. The presentation will discuss several methods and give examples how to cope with the problem.

  2. Impressions of Alcoholics Anonymous (AA) Group Cohesion: A Case for a Nonspecific Factor Predicting Later AA Attendance

    Microsoft Academic Search

    Samara Lloyd Rice; J. Scott Tonigan

    2011-01-01

    Social support for abstinence in Alcoholics Anonymous (AA) has been reported to be a consistent factor accounting for AA benefit. However, the nonspecific or unintended effects of such support remain poorly understood and rarely investigated. This prospective study investigated how one nonspecific factor—perceived AA group cohesiveness—predicted increased practice of AA-related behaviors. Findings indicated that impressions of AA group cohesion predicted

  3. Intermolecular interaction between Cry2Aa and Cyt1Aa and its effect on larvicidal activity against Culex quinquefasciatus.

    PubMed

    Bideshi, Dennis K; Waldrop, Greer; Fernandez-Luna, Maria Teresa; Diaz-Mendoza, Mercedes; Wirth, Margaret C; Johnson, Jeffrey J; Park, Hyun-Woo; Federici, Brian A

    2013-08-01

    The Cyt1Aa protein of Bacillus thuringiensis susbp. israelensis elaborates demonstrable toxicity to mosquito larvae, but more importantly, it enhances the larvicidal activity of this species Cry proteins (Cry11Aa, Cry4Aa, and Cry4Ba) and delays the phenotypic expression of resistance to these that has evolved in Culex quinquefasciatus. It is also known that Cyt1Aa, which is highly lipophilic, synergizes Cry11Aa by functioning as a surrogate membrane-bound receptor for the latter protein. Little is known, however, about whether Cyt1Aa can interact similarly with other Cry proteins not primarily mosquitocidal; for example, Cry2Aa, which is active against lepidopteran larvae, but essentially inactive or has very low toxicity to mosquito larvae. Here we demonstrate by ligand binding and enzyme-linked immunosorbent assays that Cyt1Aa and Cry2Aa form intermolecular complexes in vitro, and in addition show that Cyt1Aa facilitates binding of Cry2Aa throughout the midgut of C. quinquefasciatus larvae. As Cry2Aa and Cry11Aa share structural similarity in domain II, the interaction between Cyt1Aa and Cry2Aa could be a result of a similar mechanism previously proposed for Cry11Aa and Cyt1Aa. Finally, despite the observed interaction between Cry2Aa and Cyt1Aa, only a 2-fold enhancement in toxicity resulted against C. quinquefasciatus. Regardless, our results suggest that Cry2Aa could be a useful component of mosquitocidal endotoxin complements being developed for recombinant strains of B. thuringiensis subsp. israelensis and B. sphaericus aimed at improving the efficacy of commercial products and avoiding resistance. PMID:23727800

  4. Experimental evidence in support of Joule heating associated with geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Devries, L. L.

    1971-01-01

    High resolution accelerometer measurements in the altitude region 140 to 300 km from a satellite in a near-polar orbit during a period of extremely high geomagnetic activity indicate that Joule heating is the primary source of energy for atmospheric heating associated with geomagnetic activity. This conclusion is supported by the following observational evidence: (1) There is an atmospheric response in the auroral zone which is nearly simulataneous with the onset of geomagnetic activity, with no significant response in the equatorial region until several hours later; (2) The maximum heating occurs at geographic locations near the maximum current of the auroral electrojet; and (3) There is evidence of atmospheric waves originating near the auroral zone at altitudes where Joule heating would be expected to occur. An analysis of atmospheric response time to this heat shows time delays are apparently independent of altitude but are strongly dependent upon geomagnetic latitude.

  5. Inferring the interplanetary magnetic field by observing the polar geomagnetic field.

    NASA Technical Reports Server (NTRS)

    Wilcox, J. M.

    1972-01-01

    Svalgaard (1968, 1972) and Mansurov (1969) have shown that it is possible to infer the polarity of the interplanetary magnetic field quite reliably from observations of the diurnal variation of polar geomagnetic fields. The effect is most prominent in the vertical component of geomagnetic observatories near the geomagnetic poles during several hours near noon. The interplanetary magnetic field observed with spacecraft near the earth is very similar to the mean solar magnetic field (i.e., the sun observed as though it were a star); thus the fact that observations of the polar geomagnetic field have existed without interruption since 1926 at the Danish Meteorological Institute station at Godhavn, Greenland, means that in effect the inferred solar magnetic field during five sunspot cycles is available for analysis.-

  6. On the Latitudinal Dependence of Geomagnetic Storm Dynamical Complexity: An Empirical Mode Decomposition Approach.

    NASA Astrophysics Data System (ADS)

    De Michelis, Paola; Consolini, Giuseppe; Tozzi, Roberta

    2014-05-01

    During geomagnetically disturbed periods the Earth's magnetosphere shows a very complex dynamical character, which manifests in scaling and intermittent magnetic field fluctuations at the smallest timescales. The aim of this work is that of investigating the latitudinal dependence of complexity degree of the short timescale geomagnetic field fluctuations during four intense magnetic storms occurred between 2000 and 2003. This work is based on the analysis of the fluctuations of the horizontal component of the Earth's magnetic field measured at nine permanent geomagnetic observatories approximately with the same magnetic longitude and magnetic latitude ranging between 49N and 87N. We filter the signal via Empirical Mode Decomposition (EMD) and successively apply the Permutation Entropy (PE) analysis. The results point toward a latitudinal dependence of the complex character of geomagnetic field fluctuations indicating the different nature of the processes and phenomena responsible for the observed complex dynamics

  7. Geomagnetic sudden impulses and storm sudden commencements - A note on terminology

    NASA Technical Reports Server (NTRS)

    Joselyn, J. A.; Tsurutani, B. T.

    1990-01-01

    The definitions of and distinctions between storm sudden commencements (SSCs) and geomagnetic sudden impulses (SIs) are examined and present definitions of SIs and SSCs are modernized. Quantitative definitions of the two terms are recommended.

  8. The 1995 revision of the joint US/UK geomagnetic field models - I. Secular variation

    USGS Publications Warehouse

    Macmillan, S.; Barraclough, D.R.; Quinn, J.M.; Coleman, R.J.

    1997-01-01

    We present the methods used to derive mathematical models of global secular variation of the main geomagnetic field for the period 1985 to 2000. These secular-variation models are used in the construction of the candidate US/UK models for the Definitive Geomagnetic Reference Field at 1990, the International Geomagnetic Reference Field for 1995 to 2000, and the World Magnetic Model for 1995 to 2000 (see paper II, Quinn et al., 1997). The main sources of data for the secular-variation models are geomagnetic observatories and repeat stations. Over the areas devoid of these data secular-variation information is extracted from aeromagnetic and satellite data. We describe how secular variation is predicted up to the year 2000 at the observatories and repeat stations, how the aeromagnetic and satellite data are used, and how all the data are combined to produce the required models.

  9. Geomagnetic activity and enhanced mortality in rats with acute (epileptic) limbic lability

    NASA Astrophysics Data System (ADS)

    Bureau, Yves R. J.; Persinger, M. A.

    1992-12-01

    Presumably unrelated behaviors (e.g. psychiatric admissions, seizures, heart failures) have been correlated with increased global geomagnetic activity. We have suggested that all of these behaviors share a common source of variance. They are evoked by transient, dopamine-mediated paroxysmal electrical patterns that are generated within the amygdala and the hippocampus of the temporal lobes. Both the probability and the propagation of these discharges to distal brain regions are facilitated when nocturnal melatonin levels are suppressed by increased geomagnetic activity. In support of this hypothesis, the present study demonstrated a significant correlation of Pearson r=0.60 between mortality during the critical 4-day period that followed induction of libic seizures in rats and the ambient geomagnetic activity during the 3 to 4 days that preceded death; the risk increased when the 24 h geomagnetic indices exceeded 20 nT for more than 1 to 2 days.

  10. Dynamic subauroral ionospheric electric fields observed by the Falkland Islands radar during the course of a geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Milan, S. E.; Baker, J. B. H.; Freeman, M. P.; Lester, M.; Yeoman, T. K.

    2011-11-01

    We present an analysis of ionospheric electric field data observed during a geomagnetic storm by the recently deployed HF radar located on the Falkland Islands. On 3 August 2010 at ˜1800 UT evidence of the onset of a geomagnetic storm was observed in ground magnetometer data in the form of a decrease in the Sym-H index of ˜100 nT. The main phase of the storm was observed to last ˜24 hours before a gradual recovery lasting ˜3 days. On 4 August, during the peak magnetic disturbance of the storm, a high velocity (>1000 m s-1) channel of ionospheric plasma flow, which we interpret as a subauroral ion drift (SAID), located between 53° and 58° magnetic south and lasting ˜6.5 hours, was observed by the Falkland Islands radar in the pre-midnight sector. Coincident flow data from the DMSP satellites and the magnetically near-conjugate northern hemisphere Blackstone HF radar reveal that the SAID was embedded within the broader subauroral polarization streams (SAPS). DMSP particle data indicate that the SAID location closely followed the equatorward edge of the auroral electron precipitation boundary, while remaining generally poleward of the equatorward boundary of the ion precipitation. The latitude of the SAID varied throughout the interval on similar timescales to variations in the interplanetary magnetic field and auroral activity, while variations in its velocity were more closely related to ring current dynamics. These results are consistent with SAID electric fields being generated by localized charge separation in the partial ring current, but suggest that their location is more strongly governed by solar wind driving and associated large-scale magnetospheric dynamics.

  11. Indexing and Querying Avishek Anand

    E-print Network

    Nejdl, Wolfgang

    Indexing and Querying Avishek Anand #12;Avishek Anand Inverted Indexing basics revisited Indexing Static Collections Dictionaries Forward Index Inverted Index Organisation Scalable Indexing Indexing Dynamic Collections Inverted Index Construction and Maintenance 2 #12;Avishek Anand

  12. Solar, interplanetary and geomagnetic phenomena in March 1991 and their association with spacecraft and terrestrial problems

    SciTech Connect

    Smart, D.F.; Shea, M.A.; Fluekiger, E.O.; Sanahuja, B.

    1995-12-31

    The solar activity that occurred on 22 and 23 March 1991 resulted in major interplanetary and geomagnetic disturbances. In spite of measurements in the earth`s magnetosphere, near Venus, and by the Ulysses spacecraft (at 2.48 AU), it is not possible to identify unambiguously the source of each perturbation. A very powerful shock resulted in large geomagnetic disturbances and contributed to the generation of a third radiation belt, as measured by the CRRES spacecraft.

  13. Coronal holes, solar wind streams, and recurrent geomagnetic disturbances: 1973–1976

    Microsoft Academic Search

    N. R. Sheeley; J. W. Harvey; W. C. Feldman

    1976-01-01

    Observations of coronal holes, solar wind streams, and geomagnetic disturbances during 1973–1976 are compared in a 27-day pictorial format which shows their long-term evolution. The results leave little doubt that coronal holes are related to the high-speed streams and their associated recurrent geomagnetic disturbances. In particular, these observations strongly support the hypothesis that coronal holes are the solar origin of

  14. Extended study of extreme geoelectric field event scenarios for geomagnetically induced current applications

    NASA Astrophysics Data System (ADS)

    Ngwira, Chigomezyo M.; Pulkkinen, Antti; Wilder, Frederick D.; Crowley, Geoffrey

    2013-03-01

    Geomagnetically induced currents (GIC) flowing in man-made ground technological systems are a direct manifestation of adverse space weather. Today, there is great concern over possible geomagnetically induced current effects on power transmission networks that can result from extreme space weather events. The threat of severe societal consequences has accelerated recent interest in extreme geomagnetic storm impacts on high-voltage power transmission systems. As a result, extreme geomagnetic event characterization is of fundamental importance for quantifying the technological impacts and societal consequences of extreme space weather. This article reports on the global behavior of the horizontal geomagnetic field and the induced geoelectric field fluctuations during severe/extreme geomagnetic events. This includes (1) an investigation of the latitude threshold boundary, (2) the local time dependency of the maximum induced geoelectric field, and (3) the influence of the equatorial electrojet (EEJ) current on the occurrence of enhanced induced geoelectric fields over ground stations located near the dip equator. Using ground-based and satellite-borne Defense Meteorological Satellite Program measurements, this article confirms that the latitude threshold boundary is associated with the movements of the auroral oval and the corresponding auroral electrojet current system, which is the main driver of the largest perturbations of the ground geomagnetic field at high latitudes. In addition, we show that the enhancement of the EEJ is driven by the penetration of high-latitude electric fields and that the induced geoelectric fields at stations within the EEJ belt can be an order of magnitude larger than that at stations outside the belt. This has important implications for power networks located around the electrojet belt and confirms that earlier observations by Pulkkinen et al. (2012) were not isolated incidences but rather cases that can occur during certain severe geomagnetic storm events.

  15. A decrease in solar and geomagnetic activity from cycle 19 to cycle 24

    NASA Astrophysics Data System (ADS)

    Gvishiani, A. D.; Starostenko, V. I.; Sumaruk, Yu. P.; Soloviev, A. A.; Legostaeva, O. V.

    2015-05-01

    Variations in the solar and geomagnetic activity from cycle 19 to cycle 24 were considered based on data from the magnetic observatories of the Russian-Ukrainian INTERMAGNET segment and international centers of data on solar-terrestrial physics. It has been indicated that activity decreases over the course of time. This is especially evident during the cycle 24 growth phase. The possible causes and consequences of a decrease in geomagnetic activity were analyzed.

  16. Solar energetic particle cutoff variations during the 29-31 October 2003 geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Kress, B. T.; Mertens, C. J.; Wiltberger, M.

    2010-05-01

    At low latitudes to midlatitudes the Earth's magnetic field usually shields the upper atmosphere and spacecraft in low Earth orbit from solar energetic particles (SEPs). During severe geomagnetic storms, distortion of the Earth's field suppresses geomagnetic shielding, allowing SEPs access to the midlatitudes. A case study of the 26-31 October 2003 solar-geomagnetic event is used to examine how a severe geomagnetic storm affects SEP access to the Earth. Geomagnetic cutoffs are numerically determined in model geomagnetic fields using code developed by the Center for Integrated Space Weather Modeling (CISM) at Dartmouth College. The CISM-Dartmouth geomagnetic cutoff model is being used in conjunction with the High Energy and Charge Transport code (HZETRN) at the NASA Langley Research Center to develop a real-time data-driven prediction of radiation exposure at commercial airline altitudes. In this work, cutoff rigidities are computed on global grids and along several high-latitude flight routes before and during the geomagnetic storm. It is found that significant variations in SEP access to the midlatitudes and high latitudes can occur on time scales of an hour or less in response to changes in the solar wind dynamic pressure and interplanetary magnetic field. The maximum suppression of the cutoff is ˜1 GV occurring in the midlatitudes during the main phase of the storm. The cutoff is also significantly suppressed by the arrival of an interplanetary shock. The maximum suppression of the cutoff due to the shock is approximately one half of the maximum suppression during the main phase of the storm.

  17. Error Analysis of Explosion-Height Controlling Method Based on Geomagnetism Information

    Microsoft Academic Search

    Feng Jie; Wang Ming-Hai; Liu Shun cheng; Wu Xiao-lu

    2009-01-01

    A new explosion-height controlling scheme of the ballistic missile based on geomagnetism information was put forward aiming at the deficiency of the traditional explosion-height controlling method. The simplified geomagnetism model was presented in this study for the error analysis and precision calculating. Although the scheme was not feasible yet, it could provide the beneficial reference for the explosion-height controlling system

  18. Transform (60833005, 60573091), 863 2007AA01Z1552009AA011904

    E-print Network

    Transform (60833005, 60573091), 863 2007AA01Z1552009AA011904 200800020002 xfmeng@ruc.edu.cn Transform ( 100872) (wwcd2005@163.com) Algebra-based Transform query optimization strategy Wang Wei 100872) Abstract XQuery/Update defines a special Transform query, which is similar to be hypothetical

  19. Extreme Historic and Solar cycle 23 Geomagnetic Storm events and their Interplanetary characteristics over Indian Sector

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Ram Sudarsanam, Tulasi; Veenadhari, Bhasakara; Kadam, B. D.; Mukherjee, Shyamoli

    Geomagnetic storms are large disturbances in the magnetosphere often persisting for several days or more. During geomagnetic storms the magnetic field measured at the earth’s surface is perturbed by strong electric currents flowing within both the magnetosphere and the ionosphere. Ground magnetic and satellite measurements provide a unique database in understanding space weather. The solar cycle 23 evidenced some major geomagnetic storms. Some severe and moderate geomagnetic storms of solar cycle 23 will be studied using magnetic and satellite data. We performed superposed epoch analysis of these storms to study their ground magnetic and interplanetary characteristics. The geomagnetic data from Colaba Magnetic Observatory (Geog. Long. 72(°) 49’E, Lat. 18(°) 5’ N) consisted of systematic hourly eye observations from 1847 to 1872 in continuation of the earlier series of observations at Colaba since 1841. The extreme space weather events recorded on Colaba observatory will be discussed. We compared solar cycle 23 storms with historical geomagnetic storms recorded at Colaba to estimate their interplanetary characteristics.

  20. 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.

  1. Name: Department: GID #: Index #

    E-print Network

    Maxwell, Bruce D.

    Name: Department: GID #: Index #: (Current Index used to pay salary) In order to participate % of salary from my grant fund(s): % Index #: Beginning (mo./yr.): % Index #: Ending (mo./yr.): % Index #: % Index #: Total % (must have a minimum of 10% FTE to participate in the program) Do you have sufficient

  2. [Assessment of the effect of a geomagnetic storm on the frequency of appearance of acute cardiovascular pathology].

    PubMed

    Gurfinkel', Iu I; Kuleshova, V P; Oraevski?, V N

    1998-01-01

    The massif of data about acute coronary pathology and deaths of Central Railway Hospital (Moscow) is analysed during 1992-1993. The geomagnetic storms are characterised by their intensity and duration. The quantitative values of biotropic of the geomagnetic storms are given to different diseases. It is shown that during geomagnetic storms the number of cases of myocardial infraction increase to 2.5 times, the acute cerebral insult to 2 times, the angina pectoris and cardiac arrhythmia to 1.5 times and deaths to 1.2 times in regarding to the periods without the geomagnetic storms. PMID:9783073

  3. Low frequency 1\\/f-like fluctuations of the AE-index as a possible manifestation of self-organized criticality in the magnetosphere

    Microsoft Academic Search

    V. M. Uritsky; M. I. Pudovkin

    1998-01-01

    Low frequency stochastic variations of the geomagnetic AE-index characterized by 1\\/f b-like power spectrum (where f is a frequency) are studied. Based on the analysis of experimental data we show that the Bz- component of IMF, velocity of solar wind plasma, and the coupling function of Akasofu are insuÅcient factors to explain these behaviors of the AE-index together with the

  4. Largest geomagnetic sudden commencement (SC) and interplanetary shock

    NASA Astrophysics Data System (ADS)

    Araki, Tohru

    2015-04-01

    The long term variation of amplitude of geomagnetic sudden commencements (SCs) is examined by checking old magnetograms at Kakioka (27.5 deg. geomagnetic latitude) and Alibag (10.3 deg.) and SC lists prepared by both stations. We found that the SC occurred on March 24, 1940 was largest since 1868. The amplitude is 310 nT at Alibag and larger than 273 nT at Kakioka. The magnetogram of Cape Town (-33.3 deg) was also available for this event which shows 164 nT amplitude. This SC occurred during the main phase of a large magnetic storm which has been interested as one of space weather events. The statistical analysis shows that the occurrence probability is less than 5 % for SCs with amplitude larger than 50 nT and less than 1 % for SCs larger than 100 nT at both Kakioka and Alibag. Large amplitude SCs tend to occur in the declining phase of the sun spot cycle as is reported for magnetic storms. Siscoe et al. (1968) firstly proposed the relationship for the solar wind dynamic pressure P and SC amplitude, dH as dH = C*d(P^0.5) where d(P^0.5) shows a jump of the square root of P associated with interplanetary shocks. If we take the proportionality constant C as 15 nT/(nPa)^0.5 and the 300 nT SC amplitude (dH) needs pressure jump from 2 nPa (assumed dynamic pressure in front of the shock) to 460 nPa. If the non-linear effect for magnetospheric compression is taken into account, a larger dynamic pressure will be needed for this large amplitude SC. On the other hand, the proportionality constant, C, might become larger for larger amplitude SC because C includes effects of electric currents induced in the earth. Larger amplitude SCs have larger time variation rate by which C becomes larger and the required dynamic pressure increase becomes smaller. We do not know which of the two competing processes is dominant but we consider that the linear estimation of the required dynamic pressure described above may be valid as the first order approximation.

  5. Predicting geomagnetic reversals via data assimilation: a feasibility study

    NASA Astrophysics Data System (ADS)

    Morzfeld, Matthias; Fournier, Alexandre; Hulot, Gauthier

    2014-05-01

    The system of three ordinary differential equations (ODE) presented by Gissinger in [1] was shown to exhibit chaotic reversals whose statistics compared well with those from the paleomagnetic record. We explore the geophysical relevance of this low-dimensional model via data assimilation, i.e. we update the solution of the ODE with information from data of the dipole variable. The data set we use is 'SINT' (Valet et al. [2]), and it provides the signed virtual axial dipole moment over the past 2 millions years. We can obtain an accurate reconstruction of these dipole data using implicit sampling (a fully nonlinear Monte Carlo sampling strategy) and assimilating 5 kyr of data per sweep. We confirm our calibration of the model using the PADM2M dipole data set of Ziegler et al. [3]. The Monte Carlo sampling strategy provides us with quantitative information about the uncertainty of our estimates, and -in principal- we can use this information for making (robust) predictions under uncertainty. We perform synthetic data experiments to explore the predictive capability of the ODE model updated by data assimilation. For each experiment, we produce 2 Myr of synthetic data (with error levels similar to the ones found in the SINT data), calibrate the model to this record, and then check if this calibrated model can reliably predict a reversal within the next 5 kyr. By performing a large number of such experiments, we can estimate the statistics that describe how reliably our calibrated model can predict a reversal of the geomagnetic field. It is found that the 1 kyr-ahead predictions of reversals produced by the model appear to be accurate and reliable. These encouraging results prompted us to also test predictions of the five reversals of the SINT (and PADM2M) data set, using a similarly calibrated model. Results will be presented and discussed. References Gissinger, C., 2012, A new deterministic model for chaotic reversals, European Physical Journal B, 85:137 Valet, J.P., Maynadier,L and Guyodo, Y., 2005, Geomagnetic field strength and reversal rate over the past 2 Million years, Nature, 435, 802-805. Ziegler, L.B., Constable, C.G., Johnson, C.L. and Tauxe, L., 2011, PADM2M: a penalized maximum likelihood moidel of the 0-2 Ma paleomagnetic axial dipole moment, Geophysical Journal International, 184, 1069-1089.

  6. Geospace environment modeling 2008-2009 challenge: Dst index

    NASA Astrophysics Data System (ADS)

    Rastätter, L.; Kuznetsova, M. M.; Glocer, A.; Welling, D.; Meng, X.; Raeder, J.; Wiltberger, M.; Jordanova, V. K.; Yu, Y.; Zaharia, S.; Weigel, R. S.; Sazykin, S.; Boynton, R.; Wei, H.; Eccles, V.; Horton, W.; Mays, M. L.; Gannon, J.

    2013-04-01

    This paper reports the metrics-based results of the Dst index part of the 2008-2009 GEM Metrics Challenge. The 2008-2009 GEM Metrics Challenge asked modelers to submit results for four geomagnetic storm events and five different types of observations that can be modeled by statistical, climatological or physics-based models of the magnetosphere-ionosphere system. We present the results of 30 model settings that were run at the Community Coordinated Modeling Center and at the institutions of various modelers for these events. To measure the performance of each of the models against the observations, we use comparisons of 1 hour averaged model data with the Dst index issued by the World Data Center for Geomagnetism, Kyoto, Japan, and direct comparison of 1 minute model data with the 1 minute Dst index calculated by the United States Geological Survey. The latter index can be used to calculate spectral variability of model outputs in comparison to the index. We find that model rankings vary widely by skill score used. None of the models consistently perform best for all events. We find that empirical models perform well in general. Magnetohydrodynamics-based models of the global magnetosphere with inner magnetosphere physics (ring current model) included and stand-alone ring current models with properly defined boundary conditions perform well and are able to match or surpass results from empirical models. Unlike in similar studies, the statistical models used in this study found their challenge in the weakest events rather than the strongest events.

  7. Variations of the electric field distribution in the sub-auroral latitude and polar ionosphere during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Shinbori, A.; Nishimura, Y.; Ono, T.; Kumamoto, A.; Kikuchi, T.

    2006-12-01

    In order to clarify time and spatial evolutions of the large-scale electric field in the middle-latitude, sub-auroral and polar cap ionosphere during the development of geomagnetic storms, we have performed statistical analysis of the long-term electric field observation of the Akebono satellite for about 7 years from March, 1989 to January 1996. In the present data analysis, we selected 1725 cases of geomagnetic storms during the above period. Here, we defined the phenomena of magnetic disturbances indicating the minimum value of less than -40 nT in the SYM-H index as the geomagnetic storm. Moreover, we defined the periods of dSYM-H/dt<0 and dSYM-H/dt>0 as the main and recovery phases of geomagnetic storms, respectively. We also identified the magnetically quiet condition periods when the SYM-H and Kp indices represent more than -10 nT and less than 2. On the other hand, in the electric field data analysis, we used the mapping method into the ionosphere proposed by Mozer [1970], using the IGRF90 model field. During a magnetically quiet condition, the electric field distribution in the high-latitude region of more than 60o shows a typical structure of the electric field indicating the two-cell convection pattern. In the polar cap region, the dawn-to-dusk electric field appears with the averaged magnitude of 10.0-20.0 mV/m. Moreover, in the auroral zone, the poleward electric field mainly distributes with strong dependence on magnetic local time, which shows that the electric field is directed equatorward and poleward in the local time sectors of 00-12h and 12-24h, respectively. On the other hand, in this case, the potential drop in the polar cap region can be estimated as about 26 kV. During the main phase, the averaged electric field intensity in the auroral zone and polar cap region increases by 2-3 times amplitude and the polar cap region expands into the low-latitude region, compared with that during the magnetically quiet condition. In this case, we can estimate the polar cap potential as about 62 kV. Moreover, a new component of the poleward electric field appears in the sub-auroral region in the local time sector between 18 and 24h with the averaged magnitude of 40-60 mV/m without the azimuthal component. On the other hand, the potential distribution of the electric field shows the negative potential stricture in the dawn sector between 03 and 06h with the potential drop of about 4-6 kV. During the recovery phase, the polar cap boundary moves into the high-latitude region from 70 to 74o and the poleward electric fields clearly appear with the double structure in the auroral zone and sub-auroral region in the dusk sector between 18 and 23h. The poleward electric field in the sub-auroral region can be identified as the SAID/SAPS phenomena. Moreover, in the equatorward region of the poleward electric field, the shielding electric field appears with the magnitude of 5-10 mV/m. The similar electric fields are found in the low-latitude (less than 42 degrees) dawn sector between 02 and 05h.

  8. Addressing Impacts of Geomagnetic Disturbances on the North American Bulk Power System

    NASA Astrophysics Data System (ADS)

    Rollison, Eric; Moura, John; Lauby, Mark

    2011-08-01

    In a joint report issued in June 2010, the North American Electric Reliability Corporation (NERC) and the U.S. Department of Energy (DOE) identified geomagnetic disturbances as a high-impact, low-frequency (HILF) event risk to bulk power system reliability. The potential impact of geomagnetic disturbance events has gained renewed attention as recent studies have suggested that solar storms may be more severe and reach lower geographic latitudes than formerly expected and can affect bulk power system reliability. The most well known power system experience with geomagnetic disturbances in North America was the 13-14 March 1989 storm, which led to the collapse of the Hydro-Québec system in the early morning hours of 13 March 1989, lasting approximately 9 hours. NERC is actively addressing a range of HILF event risks to bulk power system reliability through the efforts of four of its task forces: Geomagnetic Disturbance, Spare Equipment Database, Cyber and Physical Attack, and Severe Impact Resilience. These task forces operate under the direction of three NERC committees: Planning, Operating, and Critical Infrastructure Protection. The NERC Geomagnetic Disturbance Task Force (GMDTF), which was established in September 2010, is charged with investigating the implications of geomagnetic disturbances to the reliability of bulk power systems and developing solutions to help mitigate these risks. The objective of these efforts is to develop models to better understand the nature and effects of coronal mass ejections (CMEs), the vulnerabilities of equipment, bulk power system design considerations, our ability to reduce the operational and real-time impacts of geomagnetic disturbances on the bulk power system, and restoration methods, as well as to inventory long-lead-time equipment. For more information on the current activities of the GMDTF, please visit: www.nerc.com/filez/gmdtf.html

  9. Geomagnetic variations in field tubes crossed by cargo vehicle with operating engine

    NASA Astrophysics Data System (ADS)

    Rakhmatulin, Ravil; Khakhinov, Vitaly; Pashinin, Alexander; Lipko, Yury

    Since 2011, in the framework of the "Radar-Progress" active space experiment, we have studied effects of operating engines of the “Progress” cargo vehicle on the geomagnetic field. We supposed that engine burn can generate geomagnetic disturbances in field tubes crossed by "Progress". These disturbances may be measured at sub-ionospheric magnetoconjugate points where the tubes cross the Earth's surface. Geomagnetic variations measurements are performed as follows. Prior to each experimental session, the cargo vehicle's orbital parameters were used to calculate coordinates of sub-ionospheric magnetoconjugate points. Then we selected a place most suitable for installing the Lemi-30 mobile induction magnetometer. Continuous record of geomagnetic variations starts not less than 2 hours before the cargo vehicle flyby. We used GPS for synchronization with regular measurements performed at all magnetic observatories of Institute of Solar-Terrestrial Physics. After the cargo vehicle flybys with operating engines, an excitation of geomagnetic oscillations with 25 - 160 s periods was recorded. In some cases, we observed a recurrence of the oscillations 6-15 min later. The analysis of the data was carried out taking account of the planetary and local magnetic activity. The April and June 2013 experiments were conducted under quiet and very quiet geomagnetic conditions for both middle and high latitudes. This allowed us to exclude natural sources of the geomagnetic variations. Results of this study were obtained at unique facilities of the common use centre «Angara». The study was supported by the grant 13-05-00456-a and 13-02-00957-a of the Russian Foundation for Basic Research.

  10. Coronal Mass Ejections, Interplanetary Shocks In Relation With Forbush Decreases Associated With Intense Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Verma, P. L.; Patel, Nand Kumar; Prajapati, Mateswari

    2014-05-01

    Coronal mass ejections (CMEs} are the most energetic solar events in which large amount of solar plasma materials are ejected from the sun into heliosphere, causing major disturbances in solar wind plasma, Interplanetary shocks, Forbush decrease(Fds) in cosmic ray intensity and geomagnetic storms. We have studied Forbush decreases associated with intense geomagnetic storms observed at Oulu super neutron monitor, during the period of May 1998-Dec 2006 with coronal mass ejections (CMEs), X-ray solar flares and interplanetary shocks. We have found that all the (100%) Forbush decreases associated with intense geomagnetic storms are associated with halo and partial halo coronal mass ejections (CMEs). The association rate between halo and partial halo coronal mass ejections are found 96.00%and 04.00% respectively. Most of the Forbush decreases associated with intense geomagnetic storms (96.29%) are associated with X-ray solar flares of different categories . The association rates for X-Class, M-Class, and C- Class X -ray solar flares are found 34.62%, 50.00% and 15.38% respectively .Further we have concluded that majority of the Forbush decrease associated with intense geomagnetic storms are related to interplanetary shocks (92.30 %) and the related shocks are forward shocks. We have found positive co-relation with co-relation co-efficient .7025 between magnitudes of Forbush decreases associated with intense geomagnetic storms and speed of associated coronal mass ejections. Positive co-relation with co-relation co-efficient 0.48 has also been found between magnitudes of intense geomagnetic storms and speed of associated coronal mass ejections.

  11. Scripted Finite Element Methods Applied to Global Geomagnetic Induction

    NASA Astrophysics Data System (ADS)

    Ribaudo, J.; Constable, C.

    2007-12-01

    Magnetic field observations from CHAMP, Ø rsted and SAC-C and improved techniques for comprehensive geomagnetic field modeling have generated renewed interest in using satellite and observatory data to study global scale electromagnetic induction in Earth's crust and mantle. The primary external source field derives from variations in the magnetospheric ring current, and recent studies show that over-simplified assumptions about its spatial structure lead to biased estimates of the frequency-dependent electromagnetic response functions generally used in inversions for mantle conductivity. The bias takes the form of local time dependence in the C- response estimates and highlights the need for flexible forward modeling tools for the global induction problem to accommodate 3D time-varying structure in both primary and induced fields. We are developing such tools using FlexPDE, a commercially available script-based finite element method (FEM) package for partial differential equations. Our strategy is to model the vector potential \\mathbf{A}, where \\mathbf{B} = \

  12. Model simulation of thermospheric response to recurrent geomagnetic forcing

    NASA Astrophysics Data System (ADS)

    Qian, Liying; Solomon, Stanley C.; Mlynczak, Martin G.

    2010-10-01

    We assess model capability in simulating thermospheric response to recurrent geomagnetic forcing driven by modulations in the solar wind speed and the interplanetary magnetic field. Neutral density and nitric oxide (NO) cooling rates are simulated for the declining phase of solar cycle 23. The simulated results are compared to neutral density derived from satellite drag and to NO cooling measured by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) sounding of the atmosphere using broadband emission radiometry (SABER) instrument. Model-data comparisons show good agreement between the model and the measurements for multiday oscillations, as well as good agreement for longer-term variations. The simulations demonstrate that the multiday oscillation of density is globally distributed in the upper thermosphere but restricted to high latitudes in the lower thermosphere. The density variation in the upper thermosphere exhibits less latitude dependence than the temperature variation because of the effects of composition changes. Model simulations also show that NO density and temperature play primary roles in the multiday oscillation of NO cooling rates.

  13. A Gaussian Model for Simulated Geomagnetic Field Reversals

    NASA Astrophysics Data System (ADS)

    Wicht, Johannes; Meduri, Domenico

    2015-04-01

    Reversals are the most spectacular changes in the geomagnetic field but remain little understood. Paleomagnetic data primarily constrain the reversal rate and provide few additional clues. Reversals and excursions are characterized by a dipole moment low that can last for a few 10 kyr. Some paleomagnetic records also suggest that the field decreases much slower before a reversals than it recovers afterwards and that the recovery phase may show an overshoot in field intensity. Here we study dipole moment variations in several extremely long dynamo simulation to statistically explored the reversal and excursion properties. The numerical reversals are characterized by a switch from a high axial dipole moment state to a low axial dipole moment state. When analysing the respective transitions we find that decay and growth have very similar time scales and that there is no overshoot. Other properties are generally similar to paleomagnetic findings. The dipole moment has to decrease to about 30% of its mean to allow for reversals. Grand excursions during which the field intensity drops by a comparable margin are very similar to reversals and likely have the same internal origin. The simulations suggest that both are simply triggered by particularly large axial dipole fluctuations while other field components remain largely unaffected. A model at a particularly large Ekman number shows a second but little Earth-like type of reversals where the total field decays and recovers after some time.

  14. Study of mass density enhancements at high geomagnetic latitudes

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Y.; Leitzinger, Martin; Pfleger, Martin; Sawas, Sami; Temmer, Manuela; Krauss, Sandro; Veronig, Astrid; Lammer, Helmut; Besser, Bruno

    2014-05-01

    We report on mass density deduced from measurements of the accelerometer onboard Gravity Recovery And Climate Experiment (GRACE) satellite. The investigated period starts from the beginning of November 2004 to the end of September 2007. In this time interval maximum mass densities (MMD) have been recorded by GRACE satellite at more than ten occasions. These MMD events are observed when the satellite is located near the auroral regions at high geomagnetic latitudes. We combine the MMD events and radio VLF signals recorded by ICE experiment onboard DEMETER satellite. We principally consider the reception onboard the DEMETER satellite of the VLF signals emitted by ground transmitters in the frequency range between 10 - 40 kHz. The VLF radio signals provide helpful information on the perturbations in the upper-atmosphere/lower-ionosphere layers. We emphasize in this work on the time delay between the observations of the MMS events onboard GRACE satellite in the polar regions and the disturbances of the VLF transmitter signals on DEMETER satellite at sub-polar regions. We discuss the origin of the MMD events by taking into consideration the particle environments in the cusps and auroral regions. Then we attempt to clarify how the maximum mass density events observed close to the polar regions progressed towards the mid-latitude regions and disturbed the detection of the VLF transmitter signals.

  15. Estimation of cold ion outflow rates throughout a geomagnetic storm.

    NASA Astrophysics Data System (ADS)

    Haaland, S.

    2014-12-01

    Low energy ions of ionospheric origin are believed to be a significant contributor to the magnetospheric plasma population. Measuring these low energy ions is challenging, though. Spacecraft charging effects usually prevent direct detection using particle detectors.In this paper we suggest a new approach, based on a combination of modelling, synoptic observations and a novel technique to address these issues. We thereafter use this approach to estimate outflow rates and transport of low energy ions during the October 2002 geomagnetic storm selected by the GEM community to benchmark models.Our results indicate large variations in both outflow rates and transportthroughout the various phases of 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.

  16. Engineered plasma interactions for geomagnetic propulsion of ultra small satellites

    NASA Astrophysics Data System (ADS)

    Palmer, Jeremy A.; Boerner, Jeremiah J.; Hughes, Thomas P.; Bennett, Guy R.

    2013-05-01

    Previous astrophysical studies have explained the orbital dynamics of particles that acquire a high electrostatic charge. In low Earth orbit, the charge collected by a microscopic particle or an ultra-small, low-mass satellite interacts with the geomagnetic field to induce the Lorentz force which, in the ideal case, may be exploited as a form of propellantless propulsion. Efficient mechanisms for negative and positive electrostatic charging of a so-called attosatellite are proposed considering material, geometry, and emission interactions with the ionosphere's neutral plasma with characteristic Debye length. A novel model-based plasma physics study was undertaken to optimize the positive charge mechanism quantified by the system charge-to-mass ratio. In the context of the practical system design considered, a positive charge-to-mass ratio on the order of 1.9x10-9 C/kg is possible with maximum spacecraft potential equal to the sum of the kinetic energy of electrons from active field emission (+43V) and less than +5V from passive elements. The maximum positive potential is less than what is possible with negative electrostatic charging due to differences in thermal velocity and number density of electronic and ionic species. These insights are the foundation of a practical system design.

  17. Geomagnetic field modeling from satellite attitude control magnetometer measurements

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Woo; Hwang, Jong Sun; von Frese, Ralph R. B.; Kim, Hyung Rae; Lee, Seon-Ho

    2007-05-01

    To demonstrate the utility of satellite attitude control magnetometer measurements for mapping main field variations, we analyzed the three-axis magnetometer (TAM) measurements that provide attitude control for the KOMPSAT-1 satellite. Initial processing involved transforming the TAM's magnetic measurements from the Earth-Centered Inertial coordinates (ECI) to the Earth-Centered Earth-Fixed coordinates (ECEF) and then to spherical coordinates. The magnetic field of the satellite body produces symmetric signatures in the ascending and descending orbital measurements and thus can be readily removed. Spectral correlation filtering of the orbital observations helped to eliminate the dynamic external field and solar activity noise components. The ascending and descending data were then spectrally reconstructed to estimate the total magnetic field with minimum track line noise. Correlation coefficients of 0.97 and 0.96 mark the correlation of the KOMPSAT-1 total geomagnetic intensity map with the Ørsted and IGRF2000 core magnetic field models, respectively. Power spectra from Gauss coefficients of KOMPSAT-1 model showed closeness with the models from Ørsted data and IGRF2000 model. The spherical harmonic coefficients calculated from the KOMPSAT-1 model by conjugate gradient inversion are strongly coherent with the Ørsted and IGRF2000 coefficients through degree 9.

  18. Statistical study of interplanetary condition influence on the geomagnetic substorm onset location inferred from SuperMAG auroral electrojet indices

    NASA Astrophysics Data System (ADS)

    Huang, Sheng; Du, Aimin; Cao, Xin

    2015-04-01

    It is well known that the magnetospheric substorm occurs every few hours, in response with the interplanetary condition variation and the increase of energy transfer from the solar wind to the magnetosphere. Since the substorm activity correlated well with the geomagnetic index, Newell and Gjerloev [2011] identified the substorm onset and its contributing station, using the SuperMag auroral electrojet indices. In this study, we investigate the distribution of these substorm onset locations and its response to the varied interplanetary condition. It is surprise that the substorm onset locations show double-peak structure with one peak around pre-midnight sector and the other at the dawn side. The substorm onset tends to occur in pre-midnight sector during non-storm time while it often takes place in late morning sector (~4 MLT) during storm time. Furthermore, substorms, appearing in magnetic storm main phase predominate in late morning. As the geomagnetic index Dst decreases, the substorm onset occurs in late morning more frequently. The substorm onset locations were also classified based on the solar wind parameters. It is shown that the peak number ratio of the substorm onset location in late morning over pre-midnight increases as IMF Bz decreases from positive to negative and the solar wind velocity Vsw enhances. The more intense interplanetary electric field E promotes the substorm onset occurring in late morning. It is widely accepted that both the directly driven (DD) and loading/unloading (LL/UL) processes play an essential role in the energy dispensation from the solar wind into the magnetosphere-ionosphere system. In general, the former one corresponds to the DP2 current system, which consists of the eastward electrojet centered near the dusk and the westward electrojet centered in the dawn, while the latter one corresponds to the DP1 current system, which is dominated by the westward electrojet in the midnight sector. Our statistical results of substorm onset locations imply that the energy from the solar wind tends to deplete in the directly driven process, as the interplanetary electric field is stronger.

  19. The indigenization of AA Interpretations from South India

    Microsoft Academic Search

    JAYASHREE NIMMAGADDA; KALA CHAKRADHAR

    2006-01-01

    With the spread of AA as a social movement and a treatment philosophy within and across nations of the world in dealing with problems of drinking, a growing sensitivity to diversity has emerged. This in turn has created a need to delve into contextually influenced responses to AA and the nuances of culture in responding to AA. The purpose of

  20. He+ dominance in the plasmasphere during geomagnetically disturbed periods: 1. Observational results

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Bailey, G. J.; Wilford, C. R.; Rodger, A. S.; Venkatraman, S.

    2002-04-01

    Observations made by the DMSP F10 satellite during the recovery phase from geomagnetic disturbances in June 1991 show regions of He+ dominance around 830 km altitude at 09:00 MLT. These regions are co-located with a trough in ionisation observed around 55° in the winter hemisphere. Plasma temperature and concentration observations made during the severe geomagnetic storm of 24 March 1991 are used as a case study to determine the effects of geomagnetic disturbances along the orbit of the F10 satellite. Previous explanations for He+ dominance in this trough region relate to the part of the respective flux tubes that is in darkness. Such conditions are not relevant for this study, since the whole of the respective flux tubes are sunlit. A new mechanism is proposed to explain the He+ dominance in the trough region. This mechanism is based on plasma transport and chemical reaction effects in the F-region and topside ionosphere, and on the time scales for such chemical reactions. Flux tubes previously depleted by geomagnetic storm effects refill during the recovery phase from the ionosphere as a result of pressure differences along the flux tubes. Following a geomagnetic disturbance, the He+ ion recovers quickly via the rapid photoionisation of neutral helium, in the F-region and the topside. The recovery of the O+ and H+ ions is less rapid. This is proposed as a result of the respective charge exchange reactions with neutral atomic hydrogen and oxygen. Preliminary model calculations support the proposed mechanism.

  1. Advantage of wavelet technique to highlight the observed geomagnetic perturbations linked to the Chilean tsunami (2010)

    NASA Astrophysics Data System (ADS)

    Klausner, V.; Mendes, Odim; Domingues, Margarete O.; Papa, Andres R. R.; Tyler, Robert H.; Frick, Peter; Kherani, Esfhan A.

    2014-04-01

    The vertical component (Z) of the geomagnetic field observed by ground-based observatories of the International Real-Time Magnetic Observatory Network has been used to analyze the induced magnetic fields produced by the movement of a tsunami, electrically conducting sea water through the geomagnetic field. We focus on the survey of minutely sampled geomagnetic variations induced by the tsunami of 27 February 2010 at Easter Island (IPM) and Papeete (PPT) observatories. In order to detect the tsunami disturbances in the geomagnetic data, we used wavelet techniques. We have observed an 85% correlation between the Z component variation and the tide gauge measurements in period range of 10 to 30 min which may be due to two physical mechanisms: gravity waves and the electric currents in the sea. As an auxiliary tool to verify the disturbed magnetic fields, we used the maximum variance analysis (MVA). At PPT, the analyses show local magnetic variations associated with the tsunami arriving in advance of sea surface fluctuations by about 2 h. The first interpretation of the results suggests that wavelet techniques and MVA can be effectively used to characterize the tsunami contributions to the geomagnetic field and further used to calibrate tsunami models and implemented to real-time analysis for forecast tsunami scenarios.

  2. A search for the interplanetary quantity controlling the development of geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1979-01-01

    An historical account is presented concerning the evolution of our present concept of geomagnetic storms. The present concept was formulated by Chapman (1927) in his magnetic data statistical studies of 'the initial rise' (now termed the initial phase) 'and subsequent larger decrease' (now termed the main phase) in H, followed by 'slow recovery'. The concept introduced by Alfven in 1940 of guiding center motions of a charged particle in a nonuniform magnetic field (ring currents) is also discussed. By 1963 it became quite certain that the ring current, namely a storm-time Van Allen belt, is formed in the magnetosphere during the storm's main phase. The search then began for the solar wind quantity controlling the development of the main phase. The author then gives a personal account of how our concept of geomagnetic storms has advanced and how new findings based on satellite and ground-based observations have made it possible to arrive at a first-approximation expression for the interplanetary quantity controlling the development of geomagnetic storms. Since a geomagnetic storm is a magnetic manifestation of a magnetospheric storm, which is a nonlinear superposition of intense magnetospheric substorms, the main emphasis is shifted toward the understanding of magnetospheric substorms in order to arrive at the parameters controlling the development of geomagnetic storms.

  3. Characteristics of PMSE associated with the geomagnetic disturbance driven by corotating interaction region and high-speed solar wind streams in the declining solar cycle 23

    NASA Astrophysics Data System (ADS)

    Lee, Young-Sook; Kirkwood, Sheila; Kwak, Young-Sil; Shepherd, Gordon G.; Kim, Kyung-Chan; Yang, Tae-Yong; Kero, Antti

    2015-04-01

    We report interannual variations of the correlation between the reflectivity of polar mesospheric summer echoes (PMSEs) and solar wind parameters (speed and dynamic pressure), and AE index as a proxy of geomagnetic disturbances, and cosmic noise absorption (CNA) in the declining phase (2001-2008) of solar cycle 23. PMSEs are observed by 52 MHz VHF radar measurements at Esrange (67.8°N, 20.4°E), Sweden. In approaching the solar minimum years, high-speed solar wind streams emanate from frequently emerging coronal holes, leading to 7, 9, and 13.5 day periodicities in their arrival at Earth. Periodicities of 7 and/or 9 days are found in PMSE reflectivity in 2005-2006 and 2008. Periodicity-resolved correlations at 7 and 9 days of both D region ionization observed by cosmic noise absorption (CNA) and PMSE with solar wind speed and AE index vary from year to year but generally increase as solar minimum is approached. PMSEs have a higher periodicity-resolved correlation with AE index than the solar wind speed. In addition, cross correlation of PMSE reflectivity with AE index is mostly higher than with CNA in solar minimum years (2005-2008). This can signify that high-speed solar wind stream-induced high-energy particles possibly have strong influence on CNA, but not as much as on PMSE, especially for the years of significant periodicities occurring.

  4. 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

  5. AAS Town Meeting James Webb Space Telescope

    E-print Network

    Sirianni, Marco

    JWJWJW AAS Town Meeting James Webb Space Telescope Seattle, January 7, 2003 #12;Presentations;Who was James Webb? · Administrator 2/61-10/68 ­ Formed Office of Space Science · Marine Aviator James E. Webb 1906-1992 #12;Replan Guidelines from HQ · Fit JWST program phases B/C/D within budget

  6. astroph/9808084 A&A manuscript no.

    E-print Network

    Strong, Andrew W.

    , details of the nuclear cross sections, and propagation in the Galaxy. Because they are secondary, anastro­ph/9808084 10 Aug 1998 A&A manuscript no. (will be inserted by hand later) Your thesaurus, 1998 Diffuse Galactic gamma rays, cosmic­ray nucleons and antiprotons I. V. Moskalenko 1;2 , A. W

  7. development index (HDI)

    E-print Network

    HDI rank a Human development index (HDI) value Life expectancy at birth (years) Adult literacy rate per capita (PPP US$) Life expectancy index Education index GDP index GDP per capita (PPP US$) rank development index (HDI) value Life expectancy at birth (years) Adult literacy rate (% aged 15 and above) Com

  8. Observing with HST below 1150{\\AA}: Extending the Cosmic Origins Spectrograph Coverage to 900{\\AA}

    E-print Network

    Osterman, Steve; France, Kevin; Béland, Stéphane; McCandliss, Stephan; McPhate, Jason; Massa, Derck

    2010-01-01

    The far-ultraviolet (FUV) channel of the Cosmic Origins Spectrograph (COS) is designed to operate between 1130{\\AA} and 1850{\\AA}, limited at shorter wavelengths by the reflectivity of the MgF2 protected aluminum reflective surfaces on the Optical Telescope Assembly and on the COS FUV diffraction gratings. However, because the detector for the FUV channel is windowless, it was recognized early in the design phase that there was the possibility that COS would retain some sensitivity at shorter wavelengths due to the first surface reflection from the MgF2 coated optics. Preflight testing of the flight spare G140L grating revealed ~5% efficiency at 1066{\\AA}, and early on-orbit observations verified that the COS G140L/1230 mode was sensitive down to at least the Lyman limit with 10-20 cm^2 effective area between 912{\\AA} and 1070{\\AA}, and rising rapidly to over 1000 cm2 beyond 1150{\\AA}. Following this initial work we explored the possibility of using the G130M grating out of band to provide coverage down to 90...

  9. Sporadic and recurrent geomagnetic disturbances in 1859-1860 according to the archived data from the Russian network of stations

    Microsoft Academic Search

    I. S. Veselovsky; K. Mursula; N. G. Ptitsyna; M. I. Tyasto; O. S. Yakovchouk

    2009-01-01

    Based on an analysis of the available archived data from the Russian network of geomagnetic stations, it has been indicated that the known event of August-September 1859 was the first and the greatest event in the series of the recurrent geomagnetic storms. Similar series were repeatedly observed in the next years. These series are caused by the processes on the

  10. Time variant analysis of geomagnetic signals describes the volcanic activity of Mt. Etna between early 2000 and late 2002

    Microsoft Academic Search

    Maurizio Fedi; Lorenzo Cascone; Ciro Del Negro; Mauro La Manna

    2008-01-01

    Volcanomagnetic anomalies have been mostly observed during strong eruptions. Our aim is to improve the geomagnetic data analysis to evidence the anomalies occurring in a larger time span, especially in the phases preceding the eruptive events. We developed a time variant statistical approach and applied it to the 2000–2002 Etna geomagnetic temporal series. It is based on an algorithm that

  11. Time variant analysis of geomagnetic signals describes the volcanic activity of Mt. Etna between early 2000 and late 2002

    Microsoft Academic Search

    Maurizio Fedi; Lorenzo Cascone; Ciro Del Negro; Mauro La Manna

    2008-01-01

    Volcanomagnetic anomalies have been mostly observed during strong eruptions. Our aim is to improve the geomagnetic data analysis to evidence the anomalies occurring in a larger time span, especially in the phases preceding the eruptive events. We developed a time variant statistical approach and applied it to the 2000 2002 Etna geomagnetic temporal series. It is based on an algorithm

  12. The role of vibrationally excited oxygen and nitrogen in the ionosphere during the undisturbed and geomagnetic storm

    E-print Network

    Boyer, Edmond

    The role of vibrationally excited oxygen and nitrogen in the ionosphere during the undisturbed and geomagnetic storm period of 6±12 April 1990 A. V. Pavlov Institute of Terrestrial Magnetism, Ionosphere-region ionosphere over Millstone Hill during the geomagnetically quiet and storm periods of 6±12 April 1990

  13. Ar/Ar ages from transitionally magnetized lavas on La Palma, Canary Islands, and the geomagnetic instability timescale

    E-print Network

    Singer, Bradley S.

    Ar/Ar ages from transitionally magnetized lavas on La Palma, Canary Islands, and the geomagnetic 2002. [1] A detailed study of 43 lava flows comprising two stratigraphic sequences exposed along geomagnetic events. The Matuyama-Brunhes (M-B) reversal is recorded in five transitionally magnetized lava

  14. Spring-fall asymmetry of substorm strength, geomagnetic activity and solar wind: Implications for semiannual variation and solar hemispheric asymmetry

    Microsoft Academic Search

    K. Mursula; E. Tanskanen; J. J. Love

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993–2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation,

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

    PubMed

    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 (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

  16. 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

  17. Effect of orientation of the solar wind magnetic clouds on the seasonal variation of geomagnetic activity

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    An analysis is made of the causes of seasonal dependence of geomagnetic activity, taking into account orientation of large-scale plasma structures (of the magnetic cloud type) of the solar wind. The contribution of magnetic clouds of different orientation in the periods of equinoxes and solstices is demonstrated. It is established that in equinox periods the geomagnetic activity increases due to ejections with small angles of inclination of their axis to the ecliptic plane, most frequently detected in near-Earth space. In solstice periods, such clouds are not geoeffective structures because of a decreased magnitude of projection of the magnetic field of cloud axis onto the Earth's magnetic dipole during such intervals. This effect reveals itself in a reduced level of geomagnetic activity in summer and winter.

  18. Geomagnetic semiannual variation is not overestimated and is not an artifact of systematic solar hemispheric asymmetry

    NASA Astrophysics Data System (ADS)

    Svalgaard, L.

    2011-08-01

    Mursula et al. (2011, hereafter MTL11) suggest that there is a 22-year variation in solar wind activity that coupled with the variation in heliographic latitude of the Earth during the year, gives rise to an apparent semiannual variation of geomagnetic activity in averages obtained over several solar cycles. They suggest that the observed semiannual variation is seriously overestimated and is largely an artifact of this inferred 22-year variation. We show: (1) that there is no systematically alternating annual variation of geomagnetic activity or of the solar driver, changing with the polarity of the solar polar fields, (2) that the universal time variation of geomagnetic activity at all times has the characteristic imprint of the equinoctial hypothesis rather than that of the axial hypothesis required by the suggestion of MTL11, and (3) that the semiannual variation is not an artifact, is not overestimated, and does not need revision.

  19. Interplanetary Magnetic Field Structure and Geomagnetic Storms during Solar Cycle 24

    NASA Astrophysics Data System (ADS)

    Maris Muntean, Georgeta; Besliu-Ionescu, Diana; Dobrica, Venera

    2015-04-01

    Interplanetary Magnetic Field (IMF) structure, determined by the solar magnetic field and its variability, is responsible for an essential part of the geomagnetic perturbations. IMF in the terrestrial orbital plane is structured into two or four sectors with opposite direction of the magnetic field, "away" and "towards" the Sun so that the Earth is passing through the opposite magnetic structures during a solar rotation (27 days). The magnetic structure of IMF is significantly varying during the 11-yr solar cycle. This paper analyses the IMF sectors in the solar cycle 24 (2009 - 2014) and the geomagnetic variability induced by the sector boundaries. High speed streams of the solar wind coincident with sector boundaries are determined. Geomagnetic storms triggered by such complex heliospheric phenomena are analysed by their main phase morphology (structures) and the energy transferred from solar wind into the terrestrial magnetosphere during the these phases.

  20. The responses of the thermosphere due to a geomagnetic storm: A MHD model

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Chang, S.

    1972-01-01

    A magnetohydrodynamics theory was used to study the dynamic response of the neutral atmosphere to a geomagnetic storm. A full set of magnetohydrodynamic equations appropriate for the present problem is derived and their various orders of approximation are discussed in some detail. In order to demonstrate the usefulness of this theoretical model, the May 1967 geomagnetic storm data were used in the resulting set of nonlinear, time dependent, partial differential magnetohydrodynamic equations to calculate variations of the thermosphere due to the storm. The numerical results are presented for wind speeds, electric field strength, and amount of joule heating at a constant altitude for the data recorded. Data show that the strongest thermospheric responses are at the polar region becoming weaker in the equatorial region. This may lead to the speculation that a thermospheric wave is generated in the polar region due to the geomagnetic storm which propagates towards the equator.

  1. Comparison of drag and mass spectrometer measurements during small geomagnetic disturbances

    NASA Technical Reports Server (NTRS)

    Keating, G. M.; Prior, E. J.; Chang, K.; Nicholson, J. Y., III; Von Zahn, U.

    1977-01-01

    During small geomagnetic disturbances, ESRO 4 and OGO 6 gas analyzer measurements at high altitudes suggest that helium and atomic oxygen concentrations in the lower thermosphere decrease, whereas satellite drag measurements indicate that density increases. This discrepancy is explained by the corresponding temperature increases maximizing at high latitudes. ESRO 4 data suggest that at altitudes where atomic oxygen or helium predominates, the temperature increase compensates for the decrease in lower thermospheric concentrations. This yields a net density increase with geomagnetic disturbances. The Explorer 39 drag satellite measurements verify this conclusion. It is felt that the composition variations associated with minor disturbances indicate the upwelling of the polar atmosphere, circulation towards the equator, and subsidence in the equatorial region. ESRO measurements show that at low latitudes the increases in helium concentrations with geomagnetic disturbances are chiefly caused by the circulation from high latitudes and the subsidence at lower latitudes.

  2. Orbital Noise of the Earth Causes Intensity Fluctuation in the Geomagnetic Field

    NASA Technical Reports Server (NTRS)

    Liu, Han-Shou; Kolenkiewicz, R.; Wade, C., Jr.

    2003-01-01

    Orbital noise of Earth's obliquity can provide an insight into the core of the Earth that causes intensity fluctuations in the geomagnetic field. Here we show that noise spectrum of the obliquity frequency have revealed a series of frequency periods centered at 250-, 1OO-, 50-, 41-, 30-, and 26-kyr which are almost identical with the observed spectral peaks from the composite curve of 33 records of relative paleointensity spanning the past 800 kyr (Sint-800 data). A continuous record for the past two million years also reveals the presence of the major 100 kyr periodicity in obliquity noise and geomagnetic intensity fluctuations. These results of correlation suggest that obliquity noise may power the dynamo, located in the liquid outer core of the Earth, which generates the geomagnetic field.

  3. Daytime electron density at the F1-region in Europe during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Buresova, D.; Lastovicka, J.; Altadill, D.; Miro, G.

    2002-07-01

    This study attempts to demonstrate changes in the ionospheric F1-region daytime ionization during geomagnetic storms. The F1-region is explored using available data from several European middle latitude and lower latitude observatories and a set of geomagnetic storms encompassing a range of seasons and solar activity levels. The results of analysis suggest systematic seasonal and partly latitudinal differences in the F1-region response to geomagnetic storm. The pattern of the response of the F1-region at higher middle latitudes, a decrease in electron density, does not depend on the type of response of the F2-region and on solar activity. A brief interpretation of these findings is presented.

  4. Nonlinear ARMA models for the D(st) index and their physical interpretation

    NASA Technical Reports Server (NTRS)

    Vassiliadis, D.; Klimas, A. J.; Baker, D. N.

    1996-01-01

    Time series models successfully reproduce or predict geomagnetic activity indices from solar wind parameters. A method is presented that converts a type of nonlinear filter, the nonlinear Autoregressive Moving Average (ARMA) model to the nonlinear damped oscillator physical model. The oscillator parameters, the growth and decay, the oscillation frequencies and the coupling strength to the input are derived from the filter coefficients. Mathematical methods are derived to obtain unique and consistent filter coefficients while keeping the prediction error low. These methods are applied to an oscillator model for the Dst geomagnetic index driven by the solar wind input. A data set is examined in two ways: the model parameters are calculated as averages over short time intervals, and a nonlinear ARMA model is calculated and the model parameters are derived as a function of the phase space.

  5. PEGASO . Polar Explorer for Geomagnetic And other Scientific Observation

    NASA Astrophysics Data System (ADS)

    Romeo, G.; Di Stefano, G.; Di Felice, F.; Caprara, F.; Iarocci, A.; Peterzen, S.; Masi, S.; Spoto, D.; Ibba, R.; Musso, I.; Dragoy, P.

    PEGASO (Polar Explorer for Geomagnetic And other Scientific Observation) program has been created to conduct small experiments in as many disciplines on-board of small stratospheric balloons. PEGASO uses the very low expensive pathfinder balloons. Stratospheric pathfinders are small balloons commonly used to explore the atmospheric circumpolar upper winds and to predict the trajectory for big LDBs (Long Duration Balloons). Installing scientific instruments on pathfinder and using solar energy to power supply the system, we have the opportunity to explorer the Polar Regions, during the polar summer, following circular trajectory. These stratospheric small payload have flown for 14 up to 40 days, measuring the magnetic field of polar region, by means of 3-axis-fluxgate magnetometer. PEGASO payload uses IRIDIUM satellite telemetry (TM). A ground station communicates with one or more payloads to download scientific and house-keeping data and to send commands for ballast releasing, for system resetting and for operating on the separator system at the flight end. The PEGASO missions have been performed from the Svalbard islands with the logistic collaboration of the Andoya Rocket Range and from the Antarctic Italian base. Continuous trajectory predictions, elaborated by Institute of Information Science and Technology (ISTI-CNR), were necessary for the flight safety requirements in the north hemisphere. This light payloads (<10 Kg) are realized by the cooperation between the INGV and the Physics department "La Sapienza" University and it has operated five times in polar areas with the sponsorship of Italian Antarctic Program (PNRA), Italian Space Agency (ASI). This paper summarizes important results about stratospheric missions.

  6. An Assessment of Robust Holocene Geomagnetic Field Structures

    NASA Astrophysics Data System (ADS)

    Constable, C.; Korte, M. C.; Panovska, S.

    2014-12-01

    Globally distributed paleomagnetic data from archeological artifacts and young volcanics have been combined with those from lacustrine and marine sediments to produce an increasing number of time-varying regularized geomagnetic field models that span the past 10~000 years. The spatial representation is in spherical harmonics while time variations are parameterised as cubic B-splines, and the model regularization is through quadratic norms, often the Ohmic dissipation norm and the 2nd derivative of the time variations. Results are influenced by global distribution and quality of the data and age constraints and by details of the modeling procedure. The latter include relative weighting according to assigned uncertainties, misfit measure (L1 or L2 norm), and outlier rejection. Calibration of relative paleointensity (RPI) observations and relative declinations is also an important issue, and the results are sensitive to the starting model used for initial data calibrations. It is therefore important to ensure that only absolute observations are used in the initial calibration. The most recent Holocene field models have better uncertainty estimates and improved calibration of both relative declination and RPI data, providing better field representations than earlier generations of models. Our assessment of Holocene field structure is based on an evaluation of selected models derived from essentially the same dataset as that used to produce the CALS10k.1b model. At Earth's surface robust common features among the various models are a north/south hemispheric asymmetry, with stronger average fields in the northern hemisphere and greater overall variability in the southern hemisphere. Longitudinal structure is also present, with greatest variability in the Atlantic hemisphere, but the signal is not entirely consistent across the various models. Nevertheless at the core-mantle boundary a systematic picture is beginning to emerge of the effects of heterogeneous boundary forcing in the 0-10 ka magnetic field. Correlations with seismic structure in the lowermost mantle are discussed.

  7. Pretreatment MMPI profiles of A.A. members and nonmembers.

    PubMed

    Thurstin, A H; Alfano, A M; Sherer, M

    1986-11-01

    Historically, researchers in alcoholism have focused a large amount of energy on the search for "the alcoholic personality." From this effort to identify a particular type of personality prone to the development of alcoholism arose the idea that alcoholics are not a homogeneous group. Subsequently, a number of authors reported the existence of alcoholic subtypes. Recently, research has begun to examine the relationship of personality to treatment outcome. In particular, Alcoholics Anonymous (A.A.) has come under greater scrutiny since high success rates have been ascribed to A.A. attendance. Moreover, the personality characteristics of A.A. members have been compared to alcoholics not attending A.A. Improving on earlier studies, the present research compared the pretreatment Minnesota Multiphasic Personality Inventory (MMPI) profiles of alcoholics who later elected to attend A.A. and those who did not attend. Additionally, alcoholics attending A.A. were sorted by drinking outcome and the MMPI profiles of sober and drinking A.A. members were contrasted. Although no personality differences emerged between A.A. attenders and nonmembers, there were several trends within the A.A. attending group, suggesting that successful A.A. members were less depressed, less anxious and less socially isolated than unsuccessfull A.A. members. PMID:3795961

  8. Influence of electrical conductivity heterogeneity in the D'' layer on geomagnetic jerks

    NASA Astrophysics Data System (ADS)

    Shimizu, H.; Utada, H.

    2012-12-01

    Geomagnetic jerks are known to have occurred globally around 1969, 1978 and 1991, and these are called as global jerks. Also, those occurred around 1999, 2003 and 2007 are identified as local jerks. One of the most prominent features of the 1969 geomagnetic jerk is the differential delay time of its appearance at the Earth's surface: the sudden change of the first derivatives was observed earlier in Europe compared with that in southern Africa. In this study, we suppose that the cause of the difference as large as two years is attributed to the effect of conductivity anomaly in the D'' layer, and a set of 3-d numerical modeling of electromagnetic induction in the mantle was performed to clarify whether main characteristic features of the geomagnetic jerks can be reproduced by the effect of mantle heterogeneity and magnetic field of a single spherical harmonic mode, both poloidal and toroidal, at the CMB. Numerical results suggest that even an extremely high conductive body in the D'' layer cannot generate differential delay time as large as two years at the surface of Earth by either the poloidal or the toroidal magnetic field at the CMB. On the other hand, it is demonstrated that a geomagnetic jerk originated from the toroidal magnetic field at the CMB is possibly observed as a local jerk. Recently we found that global scale geoelectric voltages observed by transoceanic submarine cables in the northwestern Pacific show jerk-like secular variation around 2006.0, and the variation can be related to the local geomagnetic jerk of 2007. Numerical results indicate that the jerk amplitude and differential delay time of the geomagnetic and geoelectric jerks have potential to constrain the electrical conductivity structure in the D'' layer. Preliminary investigation suggests the most preferable D'' structure consists of localized conducting body (which may be corresponding LLVZ) of 10,000 S/m in laterally uniform 100 S/m layer if the thickness of the D'' layer is 100 km.

  9. Loss of Geosynchronous Relativistic Electrons By Emic Wave Scattering Under Quiet Geomagnetic Conditions

    NASA Astrophysics Data System (ADS)

    Kim, K. H.; Hyun, K.; Lee, E.; Lee, D. H.

    2014-12-01

    We have examined relativistic electron flux losses at geosynchronous orbit under quiet geomagnetic conditions. One 3-day period, from 11 to 13 October 2007, was chosen for analysis because geomagnetic conditions were very quiet (3-day average of Kp < 1), and significant losses of geosynchronous relativistic electrons were observed. During this interval, there was no geomagnetic storm activity. Thus, the loss processes associated with geomagnetic field modulations caused by ring current buildup can be excluded. The >2 MeV electron flux at geosynchronous orbit shows typical diurnal variations with a maximum near noon and a minimum near midnight for each day. The flux level of the daily variation significantly decreased from first day to third day for the 3-day period by a factor of >10. The total magnetic field strength (BT) of the daily variation on the third day, however, is comparable to that on the first day. Unlike electron flux decreases, the flux of protons with energies between 0.8 and 4 MeV adiabatically responses to the daily variation of BT. That is, there is no significant decrease of the proton flux when the electron flux decreases. During the interval of quiet geomagnetic conditions, well-defined electromagnetic ion cyclotron (EMIC) waves were detected at geosynchronous spacecraft. Low-altitude polar orbiting spacecraft observed the precipitation of energetic protons and relativistic electrons in the interval of EMIC waves enhancement. From these observations, we suggest that the EMIC waves at geosynchronous orbit cause pitch-angle scattering and electron loss to the atmosphere under quiet geomagnetic conditions.

  10. On Developing a European First Principles Geomagnetically Induced Current Forecasting System

    NASA Astrophysics Data System (ADS)

    Honkonen, Ilja; Viljanen, Ari; Vanhamäki, Heikki

    2013-04-01

    Geomagnetically induced currents (GIC) during space storms pose a risk to power transmission grids across the globe. As part of the European Risk from Geomagnetically Induced Currents (EURISGIC) EU/FP7 project the Finnish Meteorological Institute is developing a first principles based GIC forecasting and warning system. The system is given as input the solar wind plasma parameters measured by the ACE spacecraft and the final output consists of the ground electric field and GIC in a simplified model of European high-voltage power grids. We present the different steps involved in obtaining the final GIC solution and implementation of the required software components.

  11. Simulation of geomagnetic currents induced in a power system by magnetohydrodynamic electromagnetic pulses

    SciTech Connect

    Rackliffe, G.B.; Crouse, J.C.; Legro, J.R.; Kruse, V.J.

    1987-01-01

    This paper quantifies the quasi-dc currents induced on a power system by a simulated magnetohydrodynamic pulse (MHD-EMP). The determination of the quasi-dc currents is based upon the similarity between the effects of MHD-EMP and the impact of geomagnetic storms. The paper highlights how the methodology to calculate geomagnetic-induced currents from solar storms was modified to calculate the currents induced by a MHD-EMP event. After specification of the MHD-EMP environment and the selection of a power system to study, the quasi-dc currents induced in the power system were calculated.

  12. A geomagnetic field model for the Holocene based on archaeomagnetic and lava flow data

    NASA Astrophysics Data System (ADS)

    Pavón-Carrasco, Francisco Javier; Osete, María Luisa; Torta, Joan Miquel; De Santis, Angelo

    2014-02-01

    We propose a new geomagnetic field model for the Holocene period based on archaeomagnetic and lava flow data, avoiding the use of lake sediment data. The source of data comes from the GEOMAGIA50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 yr. The model, called SHA.DIF.14k, allows us to analyse the behaviour of the geomagnetic field for the last 14 000 yr: from 12 000 BC to 1900 AD. For the model construction we use the spherical harmonic analysis in space and the penalized cubic B-splines in time. Both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core-mantle boundary (CMB) to assure the convergence of the model. For the last 3 ka, the model predictions agree with those given by the global model ARCH3k.1 and the European model SCHA.DIF.3k. For older epochs, the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the Holocene. For the last 9 ka, the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 BC and 3000 BC, and the well-known continuous decreasing trend of the geomagnetic field strength for the last millennium and a half. A general view of the time-average evolution of the geomagnetic field flux lobes at the CMB for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum. This lobe vanishes when the dipolar field is decreasing. The north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5.1 km/yr and 3.7 km/yr respectively. The model shows that the geomagnetic field can be averaged as axial dipolar in ˜2000 yr within an error of 5°, the typical uncertainty of the palaeomagnetic studies. Finally, and following the recent definition of archaeomagnetic jerks, we found 8 critical events in the time evolution of the geomagnetic field for the last 8 ka characterized by a maximum in the hemispheric asymmetry of the proposed model. The model is available in the Earth Ref Digital Archive at http://earthref.org/ERDA/1897/.

  13. The relation between the polarity of the interplanetary magnetic field and the polar geomagnetic field

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1973-01-01

    The relation between the azimuthal component of the interplanetary magnetic field and the polar cap geomagnetic field is discussed. The geomagnetic effects can be described as produced by an ionospheric current system encircling the magnetic pole. The sense of the current is clockwise during toward-sectors and reversed during away-sectors. The importance of this very direct solar-terrestrial relation is stressed. A recent magnetic sunspot cycle model is discussed as inferred from this relationship, the basic feature being that the sun reproduces the same sector pattern during every sunspot cycle.

  14. The geomagnetic storm of 1910 May 18 and the tail of Halley's Comet

    NASA Astrophysics Data System (ADS)

    Yan, L.-S.; Li, Z.-Y.; Gu, S.-Y.

    1984-09-01

    On May 18, 1910, the Lu-Kia-Pang Observatory near Shanghai recorded a geomagnetic storm, but it was thought that this storm was not connected with the tail of Halley's comet. In the present paper, it is argued that this storm, rather than originating in some solar activity (coronal hole or solar flare), could have been the result of the interaction of the plasma tail of Halley's comet and the earth's magnetosphere. The time lag between the storm and the transit as calculated by Leuchner (1910) is given, and the characteristic features of cometary tails and the mechanisms by which they produce geomagnetic storms are analyzed.

  15. Corrosion mechanism of laser-melted AA 2014 and AA 2024 alloys

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Chong, P. H.; Butt, A. N.; Skeldon, P.; Thompson, G. E.

    2005-07-01

    The corrosion performance of laser-melted AA 2014-T6 and AA 2024-T351 alloys, using a 2 kW CW CO 2 laser, has been examined to gain insight into the factors influencing pitting corrosion resistance. Examination of laser-melted surfaces in terms of microstructure and phase analysis was performed using scanning electron microscopy (SEM), with associated elemental analysis by energy dispersive X-ray (EDX) spectroscopy, electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Pitting corrosion resistance was evaluated using potentiodynamic anodic polarisation in 1 M NaCl solution. The work revealed that there was an improvement of pitting corrosion resistance for the laser-melted AA 2014-T6 alloy, but no improvement for AA 2024-T351 alloy. It indicated that the refinement of the microstructure, per se, with finer intermetallic particles, did not play an important role in corrosion performance. More importantly, the extension of copper solubility in the ?-Al matrix, leading to an increased corrosion potential, was considered to be the key factor responsible for the corrosion behaviours of the laser-melted aluminium alloys. For the AA 2014-T6 alloy, due to the cathodic nature of the Al 2Cu phase relative to the ?-Al solution, the rise of corrosion potential of the ?-Al solution reduced the galvanic coupling between the Al 2Cu and ?-Al matrix. As a result, the driving force for pitting corrosion in the ?-Al solution was reduced. For the AA 2024-T351 alloy, due to the anodic nature of the Al 2CuMg phase relative to the ?-Al solution, the driving force for pit initiation at the Al 2CuMg phase was enhanced. Therefore, the laser melting promoted the pitting corrosion of the AA 2024-T351 alloy.

  16. Surface electric field variations induced by intense geomagnetic storms of the solar cycle 23, a case study for the European geomagnetic observatory network

    NASA Astrophysics Data System (ADS)

    Demetrescu, Crisan; Dobrica, Venera; Stefan, Cristiana; Greculeasa, Razvan

    2015-04-01

    We present a study of the surface electric field induced by 17 intense (Dst < -150 nT) geomagnetic storms, based on the analysis of the geomagnetic records from the European network of observatories. A comparative view of the results shows the following: (1) the more pronounced geoelectric component is directed East-West; (2) the amplitude difference is of the order of tens of mV/km in case of SUA - an observatory at 45° N, and of thousands of mV/km in case of NUR - an observatory at 60° N; (3) the sudden storm commencements are more pronounced at SUA latitude than at the NUR latitude and produce a significant variation of the electric field at SUA when compared with later storm variations. The amplitude differences reverse in case of NUR, where the effects of auroral currents dominate.

  17. Ionospheric responses to two large geomagnetic storms over Japanese and Indian longitude sectors

    NASA Astrophysics Data System (ADS)

    Uma, G.; Brahmanandam, P. S.; Kakinami, Yoshihiro; Dmitriev, A.; Latha Devi, N. S. M. P.; Uday Kiran, K.; Prasad, D. S. V. V. D.; Rama Rao, P. V. S.; Niranjan, K.; Seshu Babu, Ch.; Chu, Y. H.

    2012-01-01

    The physical processes including the prompt penetration electric field, disturbance dynamo originated electric field, disturbed thermospheric winds and composition changes can play a significant role in restructuring the equatorial, low, mid and high-latitude ionosphere during storm-time. However, it has not yet been revealed that the contribution of individual physical processes, their interactions and impacts on that restructuring (Maruyama et al., 2005) is primarily due to the lack of continuous observational facilities. In this present research, the electric field (measured indirectly) and thermospheric wind (derived from an empirical disturbance wind model) components are effectively utilized as alternate database to ascertain the individual role of physical processes by studying the ionospheric response over Japanese and Indian longitude sectors during two geomagnetic storms occurring on 31 March, 2001 and 20 November, 2003 using ground (ionospheric parameters scaled from ionosondes and global ionospheric maps of total electron content measured by the ground-based GPS receivers) and satellite-borne (in-situ electron density data measured by the Planar Longmuir Probe onboard CHAMP satellite) measurements. It has been found that the equatorial ionization anomaly is expanded and intensified during the main phase of these two storms, which is believed to be caused by the prompt penetration electric field according to the current theory. In addition, the storm associated thermospheric wind is propagating equatorward (with an average velocity of ˜230 m/s) during the recovery phase of these two storms that is responsible for a height rise in the virtual height of the F-layer (h'F) starting from mid to low and equatorial latitudes with a consistent time delay. The empirical model derived winds corroborate the equatorward propagation, suggesting that this wind model data could be used as an alternate database particularly during the space weather events in order to discuss the global dynamical state of the ionosphere. Further, an important observation is that the ionospheric irregularities are found in the electron densities in the form of depletions nearly at anomaly crest region (˜23°N) as measured by the CHAMP satellite over the Japanese longitude sector during the main phase of the 20 November, 2003 storm during the pre mid night period that correspond to the time of rapid decrease (˜-30-35 nT/h) in Sym-H index due to prompt penetration of eastward electric fields into the low latitudes.

  18. High-latitude geomagnetic effects of the main phase of the geomagnetic storm of November 24, 2001 with the Northern direction of IMF

    NASA Astrophysics Data System (ADS)

    Kleimenova, N. G.; Gromova, L. I.; Dremukhina, L. A.; Levitin, A. E.; Zelinsky, N. R.; Gromov, S. V.

    2015-03-01

    The high-latitude geomagnetic events that occurred under extreme space weather conditions during the non-typical development of the main phase of the strong magnetic storm of November 24, 2001 were studied. The development of the main phase was or ceased by a sharp turn of the IMF to the north and the appearance of extremely high (up to about 60 nT) positive IMF Bz values; in this period, high alternating IMF By values were observed (from +40 to -40 nT) against a high dynamic pressure of the solar wind, with sharp bursts up to 50-70 nPa. This resulted in the cessation of nighttime substorms. Magnetic disturbances were recorded on the Earth's surface only in the daytime sector of polar latitudes as a very strong magnetic bay with amplitude of about 2000 nT. According to model calculations, a sharp intensification of field-aligned currents of the NBZ system was noted in that region. The onset of the daytime polar magnetic bay was accompanied by an auroral burst and strong local geomagnetic pulsations in the ˜(2-7) mHz band. Bursts of fluctuations in the solar wind and IMF were not accompanied by simultaneous bursts in ground based high-latitude geomagnetic pulsations, that is, the direct penetration of solar wind and IMF pulsations into the magnetosphere was unlikely to occur. The daytime polar geomagnetic pulsations observed on the Earth's surface could be caused by variations in high-latitude field-aligned currents, which were excited in a turbulent daytime boundary layer as a result of interaction with solar wind inhomogeneities.

  19. Geomagnetic events and relative palaeointensity variations during the past 300?ka as recorded in Kolbeinsey Ridge sediments, Iceland Sea: indication for a strongly variable geomagnetic field

    Microsoft Academic Search

    N. R. Nowaczyk; T. W. Frederichs

    1999-01-01

    Magnetostratigraphic analyses of five sediment cores recovered from the Kolbeinsey Ridge area revealed consistent records\\u000a of several geomagnetic events linked with low relative palaeointensities within the past 300?ka. Interpretation of various\\u000a rock magnetic parameters clearly rule out the possibility that the recorded non-normal polarity directions are linked to a\\u000a deviating magnetomineralogical fraction or a distorted magnetic fabric. Therefore, these directions

  20. Real-time predictions of geomagnetic storms and substorms: Use of the Solar Wind Magnetosphere-Ionosphere System model

    NASA Astrophysics Data System (ADS)

    Mays, M. L.; Horton, W.; Spencer, E.; Kozyra, J.

    2009-07-01

    A low-dimensional, plasma physics-based, nonlinear dynamical model of the coupled magnetosphere-ionosphere system, called Real-Time Solar Wind Magnetosphere-Ionosphere System (WINDMI), is used to predict AL and Dst values approximately 1 h before geomagnetic substorm and storm event. Subsequently, every 10 min ground-based measurements compiled by World Data Center, Kyoto, are compared with model predictions (http://orion.ph.utexas.edu/˜windmi/realtime/). WINDMI model runs are also available at the Community Coordinated Modeling Center (http://ccmc.gsfc.nasa.gov/). The performance of the Real-Time WINDMI model is quantitatively evaluated for 22 storm/substorm event predictions from February 2006 to August 2008. Three possible input solar wind-magnetosphere coupling functions are considered: the standard rectified coupling function, a function due to Siscoe, and a recent function due to Newell. Model AL and Dst predictions are validated using the average relative variance (ARV), correlation coefficient (COR), and root mean squared error (RMSE). The Newell input function yielded the best model AL predictions by all three measures (mean ARV, COR, and RMSE), followed by the rectified, then Siscoe input functions. Model AL predictions correlate at least 1 standard deviation better with the AL index data than a direct correlation between the input coupling functions and the AL index. The mean Dst ARV results show better prediction performance for the rectified input than the Siscoe and Newell inputs. The mean Dst COR and RMSE measures do not readily distinguish between the three input coupling functions.

  1. Modeling geomagnetic storms on prompt and diffusive time scales

    NASA Astrophysics Data System (ADS)

    Li, Zhao

    The discovery of the Van Allen radiation belts in the 1958 was the first major discovery of the Space Age. There are two belts of energetic particles. The inner belt is very stable, but the outer belt is extremely variable, especially during geomagnetic storms. As the energetic particles are hazardous to spacecraft, understanding the source of these particles and their dynamic behavior driven by solar activity has great practical importance. In this thesis, the effects of magnetic storms on the evolution of the electron radiation belts, in particular the outer zone, is studied using two types of numerical simulation: radial diffusion and magnetohydrodynamics (MHD) test-particle simulation. A radial diffusion code has been developed at Dartmouth, applying satellite measurements to model flux as an outer boundary condition, exploring several options for the diffusion coefficient and electron loss time. Electron phase space density is analyzed for July 2004 coronal mass ejection (CME) driven storms and March-April 2008 co-rotating interaction region (CIR) driven storms, and compared with Global Positioning System (GPS) satellite measurements within 5 degrees of the magnetic equator at L=4.16. A case study of a month-long interval in the Van Allen Probes satellite era, March 2013, confirms that electron phase space density is well described by radial diffusion for the whole month at low first invariant <400~MeV/G, but peaks in phase space density observed by the ECT instrument suite at higher first invariant are not reproduced by radial transport from a source at higher L. A 3D guiding center code with plasmasheet injection is used to simulate particle motion in time-dependent MHD fields calculated from the Lyon-Fedder-Mobarry global MHD code, as an extension of the Hudson et al. (2012) study of the Whole Heliosphere Interval of CIR-driven storms in March-April 2008. Direct comparison with measured fluxes at GOES show improved comparison with observations relative to the 2D guiding center test particle simulations and enhancement of flux at >0.6 MeV by an order of magnitude over 24 hours as observed.

  2. Full vector spherical harmonic analysis of the Holocene geomagnetic field

    NASA Astrophysics Data System (ADS)

    Richardson, Marcia

    High-quality time-series paleomagnetic measurements have been used to derive spherical harmonic models of Earth's magnetic field for the past 2,000 years. A newly-developed data compilation, PSVMOD2.0 consists of time-series directional and intensity records that significantly improve the data quality and global distribution used to develop previous spherical harmonic models. PSVMOD2.0 consists of 185 paleomagnetic time series records from 85 global sites, including 30 full-vector records (inclination, declination and intensity). It includes data from additional sites in the Southern Hemisphere and Arctic and includes globally distributed sediment relative paleointensity records, significantly improving global coverage over previous models. PSVMOD2.0 records have been assessed in a series of 7 regional intercomparison studies, four in the Northern Hemisphere and 3 in the southern hemisphere. Comparisons on a regional basis have improved the quality and chronology of the data and allowed investigation of spatial coherence and the scale length associated with paleomagnetic secular variation (PSV) features. We have developed a modeling methodology based on nonlinear inversion of the PSVMOD2.0 directional and intensity records. Models of the geomagnetic field in 100-year snapshots have been derived for the past 2,000 with the ultimate goal of developing models spanning the past 8,000 years. We validate the models and the methodology by comparing with the GUFM1 historical models during the 400-year period of overlap. We find that the spatial distribution of sites and quality of data are sufficient to derive models that agree with GUFM1 in the large-scale characteristics of the field. We use the the models derived in this study to downward continue the field to the core-mantle boundary and examine characteristics of the large-scale structure of the magnetic field at the source region. The derived models are temporally consistent from one epoch to the next and exhibit many of the expected characteristics of the field over time (high-latitude flux lobes, South Atlantic reverse flux patch, north pole reverse or null flux region).

  3. Proterozoic Geomagnetic Field Geometry from Mafic Dyke Swarms

    NASA Astrophysics Data System (ADS)

    Panzik, J. E.; Evans, D. A.

    2012-12-01

    Pre-Mesozoic continental reconstructions and paleoclimatic inferences from paleomagnetism rely critically upon the assumption of a time-averaged geocentric axial dipole (GAD) magnetic field. We have been testing the GAD assumption empirically, by compiling paleomagnetic remanence directional variations among coeval volcanic rock suites distributed over large areas of the Earth's surface. We compute virtual geomagnetic poles (VGPs) from site-mean remanence data using either a pure GAD model, or alternative models with varying amounts of zonal quadrupole or octupole fields. Rastering through quadrupole vs. octupole space, we produce contour plots of precision/dispersion for the mean of VGPs in each computation. Using the 0-5 Ma volcanics global database as a test, our method shows results consistent with the compilations of Schneider & Kent (1990, Rev. Geophys. 28, 71-96) and McElhinny et al. (1996, JGR 101, 25007-25027), notably reproducing the reversal asymmetry in a significant (order 3%) quadrupolar contribution. Performing the same test on ancient mafic dyke swarms, the Karoo-Ferrar large igneous province (ca. 0.18 Ga) and the central Atlantic magmatic province (CAMP) (0.20 Ga) datasets are consistent with a range of models, including both GAD and independent estimates of non-GAD contributions derived from global tectonic reconstructions (Torsvik & Van der Voo, 2002, GJI 151, 771-794). The method is limited by paleolongitudinal restriction of ancient LIPs, for similarly restrictive sub-sampling of the 0-5 Ma volcanic data can generate results that differ dramatically from the global mean (e.g., the far-sided offset of VGPs relative to the spin axis). Analysis of pre-Pangean datasets is limited by the uncertainty of tectonic reconstructions, but within solely the intact North American (Laurentian) craton, the Franklin (ca. 0.72), Mackenzie (ca. 1.27) and Matachewan (2.45 Ga) dyke swarms are used as Pre-Mesozoic targets that have large areal coverage. None of the Precambrian datasets show compelling reason to abandon the GAD assumption, within uncertainties; whereas previous hypotheses of 25-30% octupolar contribution throughout Precambrian time (e.g., Kent and Smethurst, 1998, EPSL 160, 391-402) generate significantly larger dispersion among the VGPs and thus appear invalidated by our test.

  4. Are ceramics and bricks reliable absolute geomagnetic intensity carriers?

    NASA Astrophysics Data System (ADS)

    Morales, Juan; Goguitchaichvili, Avto; Aguilar-Reyes, Bertha; Pineda-Duran, Modesto; Camps, Pierre; Carvallo, Claire; Calvo-Rathert, Manuel

    2011-08-01

    A detailed rock-magnetic and archeointensity study was carried out on materials baked by a western Mexican artisan following traditional techniques to produce faithful reproductions of archeological pieces of the Michoacán region (Western Mesoamerica). The field strength at the site (41.0 ± 0.5 ?T) was measured with a fluxgate magnetometer and the temperature of the furnace during the baking process was monitored continually by means of a thermocouple placed in the middle of the baking cavity. Rock-magnetic experiments performed on the raw material (clay and paste) and on insitu prepared baked ceramics and bricks included measurement of thermomagnetic curves (susceptibility and strong-field magnetization versus temperature), first-order reversal curves (FORC), anisotropy of magnetic susceptibility (AMS) and anisotropy of thermoremanent magnetization (A-TRM). Magnetite and probably hematite are present in the samples as carriers of the remanence. Hysteresis ratios suggest that the samples fall in the pseudo-single-domain grain size region, which may indicate a mixture of multi-domain and a significant amount of single-domain grains. Ceramic pieces and brick fragments were subjected to the Thellier-Coe archeointensity method and to an alternative paleointensity experiment, with a TRIAXE magnetometer, in order to check whether they are faithful recorders of the local geomagnetic field strength. Mean raw-intensity of sample M1 (pottery) overestimates a 7% the expected site intensity, while those corresponding to the brick samples (LQ1 and LQ2) underestimate it 15%. Brick sample LNQ shows a slightly lower intensity (7%), but agrees with the expected site intensity within the experimental uncertainty. The intensity retrieved from the volcanic fragment also included closely reproduces the expected intensity. After A-TRM and cooling-rate corrections, all mean raw values move closer to the expected intensity. Measurement of temperatures at different parts inside the kiln (bottom and upper parts of both central and peripheral parts) revealed the existence of significant thermal gradients, similar to those observed in ovens from other localities. Different cooling rates are then expected in a single oven. The scatter in the intensity determinations observed in this study, retrieved from pieces elaborated together in the same oven, could arise from this differentiated cooling rate within the oven and thus, to an inappropriate cooling rate correction in the archeointensity protocol. As this situation was probably reproduced in the baking of ancient ceramic artifacts, a better knowledge of the temperature distribution inside these types of kiln would be desirable in order to choose the appropriate cooling rate correction.

  5. 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.

  6. 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.

  7. Nucleic acid indexing

    DOEpatents

    Guilfoyle, Richard A. (Madison, WI); Guo, Zhen (Bellevue, WA)

    1999-01-01

    A restriction site indexing method for selectively amplifying any fragment generated by a Class II restriction enzyme includes adaptors specific to fragment ends containing adaptor indexing sequences complementary to fragment indexing sequences near the termini of fragments generated by Class II enzyme cleavage. A method for combinatorial indexing facilitates amplification of restriction fragments whose sequence is not known.

  8. Nucleic acid indexing

    DOEpatents

    Guilfoyle, Richard A. (Madison, WI); Guo, Zhen (Bellevue, WA)

    2001-01-01

    A restriction site indexing method for selectively amplifying any fragment generated by a Class II restriction enzyme includes adaptors specific to fragment ends containing adaptor indexing sequences complementary to fragment indexing sequences near the termini of fragments generated by Class II enzyme cleavage. A method for combinatorial indexing facilitates amplification of restriction fragments whose sequence is not known.

  9. Index Theorem. Nicolae Teleman

    E-print Network

    Paris-Sud XI, Université de

    Local3 Index Theorem. Nicolae Teleman Dipartimento di Scienze Matematiche, Universita' Politecnica Index Theorem. 6 5 K-Theory Local Symbol Index Class. 8 6 Review of Hochschild and Cyclic Homology. 10 6 of H,loc , with Alexander-Spanier Co-homology. . . . . . 18 9 Connes-Moscovici Local Index Theorem. 19

  10. boolean queries Inverted index

    E-print Network

    Lu, Jianguo

    boolean queries Inverted index query processing Query optimization boolean model September 9, 2014 1 / 39 #12;boolean queries Inverted index query processing Query optimization Outline 1 boolean queries 2 Inverted index 3 query processing 4 Query optimization 2 / 39 #12;boolean queries Inverted index

  11. Tools for Printing Indexes

    Microsoft Academic Search

    Jon Louis Bentley; Brian W. Kernighan

    1988-01-01

    SUMMARY This paper describes a set of programs for processing and printing the index for a book or a manual. The input consists of lines containing index terms and page numbers. The programs collect multiple occurrences of the same terms, compress runs of page numbers, create permutations (e.g., 'index, book' from 'book index'), and sort them into proper alphabetic order.

  12. Investigation of geomagnetic field and hydro-geochemical precursors of several earthquakes occurred in the territory of Armenia and Iran

    NASA Astrophysics Data System (ADS)

    Yenanov, M.; Vardanyan, G.; Adibekyan, M.

    The seismic regime observations in the territory of Armenia are performed permanently on the seven geomagnetic and seven geochemical observation stations. The full T-vector and the gases, macro-components, micro-components and some parameters are daily investigated. All the regime geomagnetic field and geo-chemical observations are accompanied with metrological works on all the stages. All observation stations and drills are located in the zones of active faults. Selected location of observation stations and drills allows observing the geomagnetic and geochemical reaction on the earthquakes not only in the territory of Armenia but also in the territory of Turkey, Georgia, Azerbaijan and Iran. The relation between the change of geomagnetic full T-vector time series field and micro- and macro-components in underground waters and the process of strong seismic events preparing is well studied. A large amount of pre-, co-, and post-seismic anomalies of physical and chemical parameters of underground waters are defined, also defined the geomagnetic field peculiarities in the investigating area. With the aim to current seismic hazard assessment in the territory of Armenia and adjacent regions the research of geomagnetic and geochemical data was carried out and earthquake precursors had been distinguished. In this paper the techniques of data processing and results of analysis of geomagnetic field peculiarities and hydro-geochemical earthquake precursors.

  13. Does the arrival index predict physiological stress reactivity in children.

    PubMed

    de Veld, Danielle M J; Riksen-Walraven, J Marianne; de Weerth, Carolina

    2014-09-01

    Knowledge about children's stress reactivity and its correlates is mostly based on one stress task, making it hard to assess the generalizability of the results. The development of an additional stress paradigm for children, that also limits stress exposure and test time, could greatly advance this field of research. Research in adults may provide a starting point for the development of such an additional stress paradigm, as changes in salivary cortisol and alpha-amylase (sAA) over a 1-h pre-stress period in the laboratory correlated strongly with subsequent reactivity to stress task (Balodis et?al., 2010, Psychoneuroendocrinology 35:1363-73). The present study examined whether such strong correlations could be replicated in 9- to 11-year-old children. Cortisol and sAA samples were collected from 158 children (83 girls) during a 2.5-h visit to the laboratory. This visit included a 1-h pre-stress period in which children performed some non-stressful tasks and relaxed before taking part in a psychosocial stress task (TSST-C). A higher cortisol arrival index was significantly and weakly correlated with a higher AUCg but unrelated to cortisol reactivity to the stressor. A higher sAA arrival index was significantly and moderately related to lower stress reactivity and to a lower AUCi. Children's personality and emotion regulation variables were unrelated to the cortisol and sAA arrival indices. The results of this study do not provide a basis for the development of an additional stress paradigm for children. Further replications in children and adults are needed to clarify the potential meaning of an arrival index. PMID:24930802

  14. Geomagnetic secular variation in South America for the past few millennia (Invited)

    NASA Astrophysics Data System (ADS)

    Hartmann, G. A.; Trindade, R. I.; Terra-Nova, F.; Poletti, W.

    2013-12-01

    The so-called South Atlantic Magnetic Anomaly (SAMA) is characterized by the lowest field intensities observed on the globe, and covers nowadays a large region between South America and South Africa. The decrease in dipole moment and the concomitant increase in non-dipolar components are the most important aspects of the SAMA evolution. In particular, the non-dipole field plays an important role in the westward drift of (and intensity decrease at) the SAMA region. Although recent archeomagnetic field models have contributed significantly to our knowledge of the geomagnetic field morphology through the past millennia, the scarcity and poor data coverage in the southern hemisphere poses an enormous problem on tracking the long-term evolution of the SAMA and other large-scale features of the geomagnetic field. Based on the available geomagnetic models, we will present the general evolution of the SAMA for the past few millennia. Then, we discuss the reliability of the models in comparison with an updated archeomagnetic database for South America. These new data show a strong non-dipole field contribution in Brazil over the past few centuries likely due to the occurrence of SAMA that is not tracked by the available versions of geomagnetic field models. With that perspective, we will also discuss our plans for the new archeomagnetic and paleomagnetic data acquisitions in South America.

  15. Geomagnetic Reversal Asymmetry at ˜1.1 Ga: New Tests from Old Rocks

    Microsoft Academic Search

    A. V. Smirnov; J. F. Diehl

    2009-01-01

    One of the most puzzling and still not fully understood phenomena of the Precambrian field is geomagnetic reversal asymmetry, which is manifested in Keweenawan rocks (˜1.1 Ga) that crop out around the Lake Superior. This reversal asymmetry is also observed in rocks from central Arizona and at the Grand Canyon from Unkar Group rocks. Most but not all of the

  16. Geomagnetic palaeointensities during the Cretaceous normal superchron measured using submarine basaltic glass

    Microsoft Academic Search

    Thomas Pick; Lisa Tauxe

    1993-01-01

    High-quality palaeointensity data have been obtained from Thellier-Thellier experiments on recent and Cretaceous submarine basaltic glasses. Whereas the recent samples faithfully yield today's geomagnetic intensity at the site, the palaeointensities for the beginning and end of the Cretaceous normal superchron are only 45% and 25%, respectively, of today's value. The data thus extend the 'Mesozoic dipole low' into the Cretaceous

  17. Derivation of magnetospheric electric fields from whistler data in a dynamic geomagnetic field

    Microsoft Academic Search

    L. P. Block; D. L. Carpenter

    1974-01-01

    The whistler method of determining magnetospheric electric fields has until recently been applied on the assumption of a static dipole geomagnetic field. We consider the effect on the whistler analysis of including both departures of the field from a dipole and temporal variations in the field. Departures from a dipole field appear to have relatively small effects on the analysis

  18. GEOMAGNETIC CONSEQUENCES OF THE SOLAR FLARES DURING THE LAST HALE SOLAR CYCLE (II)

    E-print Network

    radiation. The results are of a high interest not only for solar physics but also for otherGEOMAGNETIC CONSEQUENCES OF THE SOLAR FLARES DURING THE LAST HALE SOLAR CYCLE (II) Georgeta Maris@aira.astro.ro ABSTRACT/RESUME The effects of the solar energetic phenomena cover the entire terrestrial environment, from

  19. Two types of ion energy dispersions observed in the nightside auroral regions during geomagnetically disturbed periods

    Microsoft Academic Search

    M. Hirahara; T. Mukai; T. Nagai; N. Kaya; H. Hayakawa; H. Fukunishi

    1996-01-01

    The Akebono satellite has observed two types of energy dispersion signatures of discrete ion precipitation event in the nightside auroral regions during active geomagnetic conditions. The charged particle experiments and electric and magnetic field detectors on board Akebono provide us with essential clues to characterize the source regions and acceleration and\\/or injection processes associated with these two types of ion

  20. Behavior of Geomagnetically Trapped Electrons Injected by High-Altitude Nuclear Detonations

    Microsoft Academic Search

    J. B. Cladis; M. Walt

    1962-01-01

    This report describes recent investigations of the data obtained by the ; Jason sounding rockets during the Argus nuclear weapon tests. These instrumented ; rockets contained radiation detectors and observed electrons that were injected ; into the geomagnetic field by the decaying fission fragments from the second ; Argus explosion. An earlier analysis of the data has been published. The

  1. Greater electroencephalographic coherence between left and right temporal lobe structures during increased geomagnetic activity.

    PubMed

    Saroka, Kevin S; Caswell, Joseph M; Lapointe, Andrew; Persinger, Michael A

    2014-02-01

    Interhemispheric coherence for 19 channel EEG activity collected over a three year period from 184 men and women who relaxed in a quiet, darkened chamber showed significant increased coherence between caudal temporal regions for the 11 Hz frequency band during increased (>?8 nT) global geomagnetic activity at the time of measurement. Detailed analyses from source-localization indicated that a likely origin was the parahippocampal regions whose net differences at 10, 11 and 12 Hz intervals were significantly correlated with geomagnetic activity. Analyses of residuals to obtain a "purer" measure of parahippocampal contributions indicated that interhemispheric temporal lobe coherence across unit increments between 1 and 40 Hz revealed the most statistically significant peaks at 7.5 Hz and 19.5 Hz. These weak but reliable correlations between global geomagnetic activity and the degree of inter-temporal lobe coherence for normal people relaxing in a dark, quiet area are consistent with the results of multiple studies indicating that intrusive experiences such as "presences" or "hallucinations" are more frequent when global geomagnetic activity increases above ?15-20 nT. PMID:24287380

  2. TEC variations during geomagnetic storm/substorm with Pc5/PI2 pulsation signature

    NASA Astrophysics Data System (ADS)

    Hamada, A. M.; Mahrous, A. M.; Fathy, I.; Ghamry, E.; Groves, K.; Yumoto, K.

    2015-06-01

    The electron density integral along the paths between a GPS satellite and receiver is known as Total Electron Content (TEC), and this parameter is used in studying the ionosphere behaviors. TEC can be obtained by means of many methods. A space-based radio navigation system, such as Global Positioning System (GPS), offers good opportunities for studying the ionosphere. The TEC is calculated from the group path delay and phase advance in GPS satellite signals along the slant paths connecting GPS receivers and satellites at 22,000 km. Locally, a dual frequency GPS receiver was installed in Helwan, Egypt (29.86°N, 31.32°E) in November 2009. Here, GPS data were analyzed to establish a daily observation of Vertical TEC in a region located near to the northern crest of the ionospheric equatorial anomaly. During a moderate geomagnetic storm, observed on 02-05 May 2010, a number of ionospheric/magnetic phenomena were observed. Also, observations for Pc5/Pi2 pulsations were recorded during the geomagnetic storm phases. These geomagnetic observations are taken from MAGDAS-magnetometer station, located at Aswan (23.59°N, 32.51°E). More than 10 TECU increase in the ionospheric TEC values were recorded during the daytime of 02 May, followed by a large reduction during 03 May, reference to the pre-storm conditions. This confirms the enhancement in the geomagnetic H-component peak during the storm's initial phase and its reduction during the main phase.

  3. Brain Cancer Risk and Electromagnetic Fields (EMFs): Assessing the Geomagnetic Component

    Microsoft Academic Search

    Tim E. Aldrich; Kurtis W. Andrews; Abraham R. Liboff

    2001-01-01

    Cancer cluster studies in North Carolina identified several communities in which there existed an elevated risk of brain cancer. These findings prompted a series of case-control studies. The current article, which originated from the results of the 3rd of such studies, is focused on inclusion of the earth's own geomagnetic fields that interact with electromagnetic fields generated from distribution power

  4. Astronomic calibration of the late Oligocene through early Miocene geomagnetic polarity time scale

    E-print Network

    Zachos, James

    Astronomic calibration of the late Oligocene through early Miocene geomagnetic polarity time scale) span the late Oligocene through early Miocene ( f24­16 Ma) at a temporal resolution of f5 ky. Over. In an initial age model, we use the newly derived age of the Oligocene/Miocene (O/M) boundary of 23.0 Ma

  5. Structure, composition and thermal state of the crust in Brazil. [geomagnetic survey

    NASA Technical Reports Server (NTRS)

    Pacca, I. I. G. (principal investigator); Shukowsky, W.

    1981-01-01

    Efforts in support of a geomagnetic survey of the Brazilian area are described. Software to convert MAGSAT data tapes to the Burroughs/B-6700 binary format was developed and tested. A preliminary analysis of the first total intensity anomaly map was performed and methodologies for more intensive analysis were defined. The sources for correlative geological, aeromagnetic, and gravimetric data are described.

  6. Relationship between solar wind low-energy energetic ion enhancements and large geomagnetic storms

    Microsoft Academic Search

    Z. Smith; W. Murtagh; C. Smithtro

    2004-01-01

    It is well established that energetic ion enhancements (an energetic ion enhancement will hereafter be referred to as an EIE) are partly due to acceleration by interplanetary shocks as the shocks propagate towards Earth and that arrivals of these shocks at Earth are well associated with geomagnetic storms. The observation of EIEs at satellites located at L1 is a potential

  7. A Holocene-Late Pleistocene geomagnetic inclination record from Grandfather Lake, SW Alaska

    Microsoft Academic Search

    C. E. Geiss; S. K. Banerjee

    2003-01-01

    SUMMARY Our study of lake sediments from Grandfather Lake in SW Alaska (N59.8181 ? , W158.5597 ? ) yields the first geomagnetic inclination record for Alaska that spans the entire Holocene. The record is based on three overlapping sets of piston cores and is well dated by seven AMS radiocarbon dates. Its magnetic component consists of PSD (5-15 µm) magnetite

  8. Ring current and radiation belt during geomagnetic storms driven by CMEs and CIRs

    Microsoft Academic Search

    Y. S. Miyoshi; R. Kataoka

    2005-01-01

    It has been known that CMEs and CIRs are two major solar wind drivers of geomagnetic storms. The primary parameter to control the ring current evolution is the southward component of the IMF. On the other hand, it is considered that the solar wind speed is a primary parameter to control the formation of the radiation belts. The solar wind

  9. Dissipation of solar wind energy in the earth's upper atmosphere - The geomagnetic activity effect

    Microsoft Academic Search

    G. W. Proelss; M. Roemer; J. W. Slowey

    1988-01-01

    The current status of understanding of solar corpuscular radiation is evaluated; since many disturbance-effect properties in the terrestrial upper atmosphere are determined by the morphology of energy deposition, attention is given to the salient characteristics of the solar wind energy source, and the commonly employed geomagnetic indices are discussed. The thermospheric perturbations experienced at high latitudes during magnetically quiet conditions,

  10. Dynamic Responses of the Earth's Outer Core to Assimilation of Observed Geomagnetic Secular Variation

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Tangborn, Andrew

    2014-01-01

    Assimilation of surface geomagnetic observations and geodynamo models has advanced very quickly in recent years. However, compared to advanced data assimilation systems in meteorology, geomagnetic data assimilation (GDAS) is still in an early stage. Among many challenges ranging from data to models is the disparity between the short observation records and the long time scales of the core dynamics. To better utilize available observational information, we have made an effort in this study to directly assimilate the Gauss coefficients of both the core field and its secular variation (SV) obtained via global geomagnetic field modeling, aiming at understanding the dynamical responses of the core fluid to these additional observational constraints. Our studies show that the SV assimilation helps significantly to shorten the dynamo model spin-up process. The flow beneath the core-mantle boundary (CMB) responds significantly to the observed field and its SV. The strongest responses occur in the relatively small scale flow (of the degrees L is approx. 30 in spherical harmonic expansions). This part of the flow includes the axisymmetric toroidal flow (of order m = 0) and non-axisymmetric poloidal flow with m (is) greater than 5. These responses can be used to better understand the core flow and, in particular, to improve accuracies of predicting geomagnetic variability in future.

  11. A comparison between effects of solar proton events and of geomagnetic storms on the ozone profiles

    Microsoft Academic Search

    Yordan Tassev; Peter I. Y. Velinov; Lachezar Mateev; Dimitrinka Tomova

    2003-01-01

    Short-term variations along the ozone profiles (both in experimental and theoretical aspects) are discussed in the present work. Thus, a selected period of the major Solar Proton Event (SPE) of 14 July 2000, and the ensuing strong geomagnetic storm (Kp=9o) with Sudden Storm Commencement (SSC) is investigated. This SPE is dubbed the “Bastille Event”, after the French national holiday. Ozone

  12. AN EVALUATION OF A GEOMAGNETIC DIRECTION SENSOR FOR VEHICLE GUIDANCE IN PRECISION AGRICULTURE APPLICATIONS By

    Microsoft Academic Search

    E. R. Benson; T. S. Stombaugh; N. Noguchi; J. D. Will; J. F. Reid

    1998-01-01

    Summary: Agricultural vehicle automation has increased in recent years. In this project, a fluxgate magnetometer (geomagnetic direction sensor or GDS) was calibrated on an agricultural tractor to provide heading information. The accuracy of the GDS (1.13 degrees) was within the consistency of the GPS reference (1.32 degrees). A PID steering controller and three guidance controllers (GPS, GPS with a position

  13. Zonal winds in the equatorial upper thermosphere: Decomposing the solar flux, geomagnetic activity, and seasonal dependencies

    Microsoft Academic Search

    Huixin Liu; Hermann Lühr; Shigeto Watanabe; Wolfgang Köhler; Vance Henize; Pieter Visser

    2006-01-01

    Using 3 years (2002-2004), over 16,400 orbits of measurements from the accelerometer on board the CHAMP satellite, we have studied the climatology of the equatorial zonal wind in the upper thermosphere. Several main features are noticed. The most prominent one is that the solar flux significantly influences both the daytime and nighttime winds. It overrides the geomagnetic activity effect, which

  14. The aurora and particle fluxes during the large January 21, 2005 geomagnetic storm

    Microsoft Academic Search

    H. U. Frey; S. B. Mende; T. J. Immel; J. McFadden; D. S. Evans

    2005-01-01

    The geomagnetic storm on January 21, 2005 was special and different from other storms that an unusual large amount of ions were precipitated into the upper atmosphere. The proton aurora imager SI-12 on the NASA IMAGE spacecraft observed the strongest proton aurora signal since the beginning of the mission in May 2000. The storm started at 17:12 when a large

  15. Do migratory flight paths of raptors follow constant geographical or geomagnetic courses?

    Microsoft Academic Search

    Kasper Thorup; Mark Fuller; Thomas Alerstam; Mikael Hake; Nils Kjellén; Roine Strandberg

    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 per- egrinus, on autumn migration between North and South America, and seven honey buzzards, Pernis apivo- rus,

  16. Recordings of geomagnetically induced currents and a nowcasting service of the Finnish natural gas pipeline system

    Microsoft Academic Search

    A. Viljanen; A. Pulkkinen; R. Pirjola; K. Pajunpää; P. Posio; A. Koistinen

    2006-01-01

    The geomagnetically induced currents (GIC) in the Finnish natural gas pipeline have been measured at one site in southern Finland since November 1998. We give an overview of this long and uniform time series covering one sunspot maximum. We also briefly discuss the conventional magnetic activity indices K and Ak, and, additionally, the range of the magnetic field and of

  17. The dynamical responses of the thermosphere due to a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Chang, S. C.; Smith, R. E.

    1974-01-01

    A theoretical model for the dynamic responses to geomagnetic storms in the thermosphere is derived from magnetohydrodynamic theory. The validity claim for this model is based on the assumption that the thermosphere behaves like an electrically conductive fluid. In order to test the proposed model, a numerical example is presented. Recommendations for improving the model are also offered.

  18. PUBLISHED ONLINE: 19 FEBRUARY 2012 | DOI: 10.1038/NGEO1404 Geomagnetic field variability during the

    E-print Network

    Granot, Roi

    during the Cretaceous Normal Superchron Roi Granot* , Jérôme Dyment and Yves Gallet Prolonged periods- vals, the Cretaceous Normal Superchron, lasted from approx- imately 121 to 83 million years ago1 above the oceanic crust formed during this period. The exact behaviour of the geomagnetic field during

  19. Ionospheric and geomagnetic response to the total solar eclipse on 1 August 2008 over Northern Hemisphere

    Microsoft Academic Search

    Mohammad Awad Momani; Baharudin Yatim; Mohamad Alauddin Mohd Ali

    2010-01-01

    The ionospheric and geomagnetic response to the total eclipse of the Sun on 1 August 2008 over Northern Hemisphere has been examined using 14 GPS, three ISR radar, and three magnetometer ground-based stations. Three different approaches were employed to examine the TEC depletion occurrence at the GPS stations: determination of the TEC depletion parameters during the solar eclipse with respect

  20. Prediction of the geomagnetic storm associated Dstindex using an artificial neural network algorithm

    Microsoft Academic Search

    Samuel Kugblenu; Satoshi Taguchi; Takashi Okuzawa

    1999-01-01

    In order to enhance the reproduction of the recovery phase Dstindex of a geomagnetic storm which has been shown by previous studies to be poorly reproduced when compared with the initial and main phases, an artificial neural network with one hidden layer and error back-propagation learning has been developed. Three hourly Dstvalues before the minimum Dstin the main phase in

  1. ULF geomagnetic changes possibly associated with the 2008 Iwate-Miyagi Nairiku earthquake

    NASA Astrophysics Data System (ADS)

    Hattori, Katsumi; Hirano, Takuya

    2010-05-01

    There are many reports on earthquake-related electromagnetic phenomena. Anomalous ULF geomagnetic field changes associated with earthquake is one of the most convincing and promising phenomena due to deeper skin depth. Since ULF signals associated with large earthquakes are weak, effective signal discrimination methods should be required. Several methods for the signal discrimination have been developed so far: which are spectrum density ratio analysis, geomagnetic transfer function analysis, fractal analysis, principal component analysis, direction finding analysis, and so on.?In this study, we investigate ULF geomagnetic changes possibly associated with the 2008 Iwate-Miyagi Nairiku earthquake based on spectral density ratio analysis and fractal analysis. Geomagnetic data observed at Esashi, where the epicentral distance is about 47 km and Kakioka, the distance is about 317 km, and as a reference station have been analyzed. Wavelet transform have been performed for the spectral density analysis instead of the conventional FFT method. Before the earthquake, the variation of spectral density ratio, Sz/Sx and Sz/Sy, at the nearest station of Esashi exhibits an apparent increase from the trend. On the contrary, there are no corresponding significant changes at a remote station of Kakioka. After investigating the singularity of the increase using normalized spectrum density ratio, the enhancement is the most significant in intensity and simultaneously results of fractal analysis show abnormal behavior. The lead time is about 3-4 weeks before the earthquake. These facts suggest the anomalous change is a possible candidate of earthquake-related ULF magnetic change.

  2. Improving the geomagnetic field modeling with a selection of high-quality archaeointensity data

    NASA Astrophysics Data System (ADS)

    Pavon-Carrasco, Francisco Javier; Gomez-Paccard, Miriam; Herve, Gwenael; Osete, Maria Luisa; Chauvin, Annick

    2014-05-01

    Geomagnetic field reconstructions for the last millennia are based on archeomagnetic data. However, the scatter of the archaeointensity data is very puzzling and clearly suggests that some of the intensity data might not be reliable. In this work we apply different selection criteria to the European and Western Asian archaeointensity data covering the last three millennia in order to investigate if the data selection affects geomagnetic field models results. Thanks to the recently developed archeomagnetic databases, new valuable information related to the methodology used to determine the archeointensity data is now available. We therefore used this information to rank the archaeointensity data in four quality categories depending on the methodology used during the laboratory treatment of the samples and on the number of specimens retained to calculate the mean intensities. Results show how the intensity geomagnetic field component given by the regional models hardly depends on the selected quality data used. When all the available data are used a different behavior of the geomagnetic field is observed in Western and Eastern Europe. However, when the regional model is obtained from a selection of high-quality intensity data the same features are observed at the European scale.

  3. Geomagnetic imprinting: A unifying hypothesis of long-distance natal homing in salmon and sea turtles

    E-print Network

    Lohmann, Kenneth J.

    Geomagnetic imprinting: A unifying hypothesis of long-distance natal homing in salmon and sea) Several marine animals, including salmon and sea turtles, disperse across vast expanses of ocean before remained an enduring mystery. Salmon are known to use chemical cues to identify their home rivers

  4. Sun–Earth geometry, geomagnetic activity, and planetary F2 layer ion density

    Microsoft Academic Search

    Chaman-Lal

    2000-01-01

    Our previous quantitative analyses have shown that geomagnetic activity and planetary ion density of the F2 layer of the ionosphere seem to share the same parent cause, the solar wind, whose entry into geospace is controlled by the Sun–Earth geometry. The thrust of this paper is four fold: (a) to establish the reality of this not clearly recognized connection, (b)

  5. Properties of magnetic clouds and geomagnetic storms associated with eruption of coronal sigmoids

    Microsoft Academic Search

    Robert J. Leamon; Richard C. Canfield; Alexei A. Pevtsov

    2002-01-01

    (1) We study 46 solar coronal eruptions associated with sigmoids seen in images from the Yohkoh Soft X-ray Telescope (SXT). We relate the properties of the sigmoids to in situ measurements at 1 AU and geomagnetic storms. Our primary result is that erupting sigmoids tend to produce geoeffective magnetic clouds (MCs): 85% of the erupting sigmoidal structures studied spawned at

  6. Oxygen aurora during the recovery phase of a major geomagnetic storm

    Microsoft Academic Search

    A. W. Stephan; K. F. Dymond; S. A. Budzien; S. E. Thonnard; R. P. McCoy

    2004-01-01

    We have analyzed ultraviolet spectra measured in the postsunset auroral zone on 16 July 2000, during the recovery phase of the major geomagnetic storm of 14–16 July 2000. We find enhanced oxygen ion and neutral line emissions above 300 km in the postsunset sector of the auroral oval during the initial fast recovery phase of the storm, also called the

  7. Zonal winds in the equatorial upper thermosphere: Decomposing the solar flux, geomagnetic activity, and seasonal dependencies

    Microsoft Academic Search

    Huixin Liu; Hermann Lühr; Shigeto Watanabe; Wolfgang Köhler; Vance Henize; Pieter Visser

    2006-01-01

    Using 3 years (2002–2004), over 16,400 orbits of measurements from the accelerometer on board the CHAMP satellite, we have studied the climatology of the equatorial zonal wind in the upper thermosphere. Several main features are noticed. The most prominent one is that the solar flux significantly influences both the daytime and nighttime winds. It overrides the geomagnetic activity effect, which

  8. On the seasonal asymmetry of the diurnal and semidiurnal geomagnetic variations

    Microsoft Academic Search

    A. Chulliat; E. Blanter; J.-L. Le Mouël; M. Shnirman

    2005-01-01

    The diurnal and semidiurnal variations of the geomagnetic field are investigated at 18 observatories using long series of hourly values (up to 97 years at Sitka). The seasonal variations of amplitude of the 12-hour and 24-hour lines are obtained for the H and Z components using a 28-day sliding window. The Fourier analysis is performed using either all days within

  9. Steady flows at the top of earth's core derived from geomagnetic field models

    Microsoft Academic Search

    Coerte V. Voorhies

    1986-01-01

    Select models of the main geomagnetic field and its secular variation are extrapolated to the base of an insulating mantle and used to estimate the adjacent fluid motion of a perfectly conducting outer core. The assumption of steady motion provides formally unique solutions and is tested along with that of no upwelling. The hypothesis of no upwelling is found to

  10. Statistical results for the thermospheric and geomagnetic response to interplanetary coronal mass ejections

    NASA Astrophysics Data System (ADS)

    Temmer, Manuela; Krauss, Sandro; Veronig, Astrid; Baur, Oliver; Lammer, Helmut

    2015-04-01

    During the time range August 2003 - August 2010, we find for 35 disturbances from interplanetary coronal mass ejections (ICMEs) a clear density enhancement in the thermosphere (derived from GRACE and CHAMP accelerometer measurements) by more than 150 percent compared to the pre-event level. For this sample of ICME-thermosphere events, we extract geomagnetic parameters and from the ICME, separately for the sheath and magnetic cloud component, characteristic parameters such as the impact speed, magnetic field orientation as well as strength and disturbance duration. We present a statistical analysis of various ICME parameters and their relation to geomagnetic (Dst, AE, ap, Kp, ...) as well as thermospheric response. We show, among high correlations between geomagnetic and thermospheric quantities, that the strength of the Bz component of the ICME gives the strongest relation to the neutral density enhancement. For most of the events, the strongest negative Bz component is found in the magnetic cloud of the disturbance. Furthermore, the results indicate a shock related intensification of geomagnetic storms and neutral density enhancement due to a larger Bz caused by shock compression.

  11. High paleointensities for the Canary Islands constrain the Levant geomagnetic high

    NASA Astrophysics Data System (ADS)

    de Groot, Lennart V.; Béguin, Annemarieke; Kosters, Martha E.; van Rijsingen, Elenora M.; Struijk, Erzsébet L. M.; Biggin, Andrew J.; Hurst, Elliot A.; Langereis, Cor G.; Dekkers, Mark J.

    2015-06-01

    Understanding the behavior of enigmatic geomagnetic traits such as the Levant intensity high is currently challenged by a lack of full vector records of regional variations in the geomagnetic field. Here we apply the recently proposed multi-method paleointensity approach to a suite of 19 lavas from the Canary Islands dating between ?4000 BC and 1909 AD. Our new record reveals high paleointensities (VADMs >120 ZAm2) coinciding with and shortly after the peak in geomagnetic intensity in the Levant at ?1000 BC. Furthermore our data suggests a westward movement of this geomagnetic phenomenon at a rate of 6.7-12°?per century. In addition to IZZI-Thellier, microwave-Thellier and the multi-specimen method, the calibrated pseudo-Thellier method is an important part of the multi-method paleointensity approach. The calibration of this relative paleointensity method was derived from a suite of Hawaiian lavas; it is improved with the results of the Canarian cooling units. Pseudo-Thellier results from samples with very low Curie temperature (<150 °C), however, cannot be reliably converted to absolute paleointensity estimates. The multi-method paleointensity approach yielded a reliable estimate for ?60% of the flows sampled - an unusually high success rate for a paleointensity study involving lavas.

  12. Using geomagnetic birefringence to locate sources of impulsive, terrestrial VHF signals detected by satellites on orbit

    Microsoft Academic Search

    Abram R. Jacobson; Xuan-Min Shao

    2001-01-01

    The Earth's ionosphere is magnetized by the geomagnetic field and imposes birefringent modulation on VHF radio signals propagating through the ionosphere. Satellites viewing VHF emissions from terrestrial sources receive ordinary and extraordinary modes successively from each broadband pulse emitted by the source. The birefringent intermode frequency separation can be used to determine the value of fcecosbeta, where fce is the

  13. The geomagnetic dipole moment over the last 7000 years—new results from a global model

    Microsoft Academic Search

    M. Korte; C. G. Constable

    2005-01-01

    Evolution of the geomagnetic field's dipole strength is studied by geomagnetists from global spherical harmonic models and by paleomagnetists using virtual (axial) dipole moments (VDM, VADM). Based on a recently published global model of the past 7000 yr we study whether these three dipole moment descriptions can be considered equivalent, and compare the results to previous global VADM studies and

  14. Geomagnetic dipole moment collapse by convective mixing in the core and Peter Olson2

    E-print Network

    Liu, Lijun

    #12;Geomagnetic dipole moment collapse by convective mixing in the core Lijun Liu1 and Peter Olson2 we determine rates of dipole moment decrease as a function of magnetic Reynolds number following structure on the core-mantle boundary. We find that the maximum rate of dipole moment decrease on century

  15. Se connecter la prospective AA L'adresse de la prospective AA est : https://extra.core-cloud.net/projets/prospectiveAA2014

    E-print Network

    Canet, Léonie

    Se connecter à la prospective AA L'adresse de la prospective AA est : https://extra.core-cloud.net/projets/prospective que vous ayiez à demander l'accès à la prospective. Dans ce cas, voir l'annexe A. 2) Si vous faites la prospective (annexe A). 3) Vous faites partie d'un organisme qui ne propose pas de fournisseur d

  16. Risk Analysis and Forecast Service for Geomagnetically Induced Currents in Europe

    NASA Astrophysics Data System (ADS)

    Wik, Magnus; Pirjola, Risto; Viljanen, Ari; Lundstedt, Henrik

    Geomagnetically induced currents (GIC), occurring during magnetic storms, pose a widespread natural disaster risk to the reliable operation of electric power transmission grids, oil and gas pipelines, telecommunication cables and railway systems. The solar magnetic activity is the cause of GIC. Solar coronal holes can cause recurrent inter-vals of raised geomagnetic activity, and coronal mass ejections (CME) at the Sun, sometimes producing very high speed plasma clouds with enhanced magnetic fields and particle densities, can cause the strongest geomagnetic storms. When the solar wind interacts with the geomag-netic field, energy is transferred to the magnetosphere, driving strong currents in the ionosphere. When these currents change in time a geoelectric field is induced at the surface of the Earth and in the ground. Finally, this field drives GIC in the ground and in any technological conductor systems. The worst consequence of a severe magnetic storm within a power grid is a complete blackout, as happened in the province of Québec, Canada, in March 1989, and in the city of Malmü, Sweden, in October 2003. Gas and oil pipelines are not regarded as vulnerable to the immediate impact of GIC, but the corrosion rate of buried steel pipes can increase due to GIC, which may thus shorten the lifetime of a pipe. European Risk from Geomagnetically Induced Currents (EURISGIC) is an EU project, that, if approved, will produce the first European-wide real-time prototype forecast service of GIC in power systems, based on in-situ solar wind observations and comprehensive simulations of the Earth's magnetosphere. This project focuses on high-voltage power transmission networks, which are probably currently the most susceptible to GIC effects. Geomagnetic storms cover large geographical regions, at times the whole globe. Consequently, power networks are rightly described as being European critical infrastructures whose disruption or destruction could have a significant impact. The project includes six research institutes and one SME, within Europe and US. The Federal Emergency Management Agency (FEMA), the Swedish civil contingencies agency (MSB), and representatives from the European Commission are collaborating with the NOAA National Weather Service and other research institutes on various space weather scenarios -geomagnetic storms with widespread blackouts and disruptions in communications. The aim of this new project is to conduct a risk analysis from GIC on critical infrastructure. Large amounts of natural gas are transported from Russia to Central Europe. Those long pipelines are prone to GIC impacts, which should also be evaluated quantitatively. We will use the EURISGIC project to inform the pipeline community of present European capability in GIC modelling, forecasting and in developing mitigation measures.

  17. Preparation of fibrin des-AA by thrombin.

    PubMed

    Lougovskoi, E V; Gogolinskaya, G K

    1999-01-01

    The active thrombin is formed in the blood stream when the blood coagulation system is activated. It attacks fibrinogen, splits off two fibrinopeptides A and fibrinogen is transformed into des-AA fibrin which is able to polymerize spontaneously forming protofibrils. At high thrombin concentration the enzyme splits off two fibrinopeptides B and des-AA fibrin units are transformed into des-AABB fibrin. These two forms of fibrin are widely used in the biological experiments. However des-AA fibrin is obtained usually from fibrinogen using the snake poisons (such as reptilase). Des-AA fibrin was obtained also by physiological enzyme thrombin, but that des-AA fibrin samples had the contamination of des-AABB fibrin. At the present paper we have described the method of the des-AA fibrin preparation by thrombin without any contamination of des-AABB fibrin. PMID:10791069

  18. Applying inversion techniques to derive source currents and geoelectric fields for geomagnetically induced current calculations

    NASA Astrophysics Data System (ADS)

    de Villiers, J. S.; Cilliers, P. J.

    2014-10-01

    This research focuses on the inversion of geomagnetic variation field measurement to obtain source currents in the ionosphere. During a geomagnetic disturbance, the ionospheric currents create magnetic field variations that induce geoelectric fields, which drive geomagnetically induced currents (GIC) in power systems. These GIC may disturb the operation of power systems and cause damage to grounded power transformers. The geoelectric fields at any location of interest can be determined from the source currents in the ionosphere through a solution of the forward problem. Line currents running east-west along given surface position are postulated to exist at a certain height above the Earth's surface. This physical arrangement results in the fields on the ground having the magnetic north and down components, and the electric east component. Ionospheric currents are modelled by inverting Fourier integrals (over the wavenumber) of elementary geomagnetic fields using the Levenberg-Marquardt technique. The output parameters of the inversion model are the current strength, height and surface position of the ionospheric current system. A ground conductivity structure with five layers from Quebec, Canada, based on the Layered-Earth model is used to obtain the complex skin depth at a given angular frequency. This paper presents preliminary and inversion results based on these structures and simulated geomagnetic fields. The results show some interesting features in the frequency domain. Model parameters obtained through inversion are within 2% of simulated values. This technique has applications for modelling the currents of electrojets at the equator and auroral regions, as well as currents in the magnetosphere.

  19. Peculiarities of Appearance of Westward Drift on the Earth's Surface and Core Fluid Fluxes Causing Drift of the Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Simonyan, A.

    2009-04-01

    Investigation of core originated variations of the recent geomagnetic field, provided by regular observation data on the worldwide net of magnetic observatories shows that decade variations might be envisaged as a result of superposition of jerks stochastically appearing in different regions of the Earth's surface at different time. Quantitative estimation of all the jerks observed on the globe throughout the 20th century, promotes construction of jerk based every-year spatial models of core originated geomagnetic field and its secular variations through time expansion of central spherical model IGRF1980, constructed by use of homogeneous vector data of magnetic satellite MAGSAT. Obtained JBM_SV and JBMF allow study of year- by-year dynamics of the main structural specificities of core originated geomagnetic field. Both processes of slow diffusion and advection of the field by core fluid fluxes have been detected in result. It has been revealed also that diffusion is caused mainly by slow dissipation of dipole field. While in the non-dipole field dynamics the processes of regional feature swelling/decay and drifting are exposed. Drift strictly toward to the west is revealed only in the restricted region of the Earth's surface figuring the known Brazil geomagnetic anomaly. However global feature drift of geomagnetic morphological structures is observed in narrow band along the geomagnetic axis and is directed to north-west and south-east in the northern and southern hemispheres correspondingly. Reflection of the global drift was found in the slow variations of integral geomagnetic characteristic when geomagnetic center angular coordinates temporal series were investigated. Correlation between the global geomagnetic variations caused by drift of core field, and variations of orientation of the Earth's daily rotation axis is shown up. Despite of some specificities depicted in variations of these parameters, which evidently are caused by complicated character of interaction between geomagnetic field and axial rotation, variations correlation is quite distinct for being ignored. Steady north-west drift of geographical pole corresponds well to the drift of geomagnetic integral characteristic during the whole 100-year period under investigation. Such a correspondence evidently might be caused by influence of Coriolis forces on the orientation of geomagnetic dipole and drift caused variations with characteristic times over than 100-years. Hence it is reasonable to conclude that between the spatial structure of global geomagnetic disturbances reflected in drift of geomagnetic center, and the variations of orientation of the vector of daily rotation velocity there is cause-and-effect relation, the mechanism of which can be magnetostrophic balance of forces, functioning in conditions of the Earth's liquid core. Study of the structure of quasi-stationary movement system on the liquid core surface through its decomposition into the rotational and divergent components, and its dynamics shows that leading role in motions system carry divergent character movements. Foci of rotational movements arise between the foci of divergent character motions evidently due to the Coriolis forces. Their permanent manifestation in the Atlantic region between African and Latin American plates could cause observed westward drift of geomagnetic field. Core surface motions structural-dynamic pattern at the whole resembles the scenario of rising from deeper layers plums, which reaching the surface stochastically at different regions, reorganize quasi-stationary system of surface motions, established from one kinematic jerk to another. Correspondingly jerks in the geomagnetic field appear due to advection of geomagnetic field by fluid fluxes.

  20. Longitudinal Section AA; Lower Chord Plan Powerscourt Bridge, Spanning ...

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

    Longitudinal Section A-A; Lower Chord Plan - Powerscourt Bridge, Spanning Chateauguay River, First Concession Road, Elgin/Hichinbrooke, Huntingdon County, Quebec, Canada, Chateaugay, Franklin County, NY

  1. Index des mots-cls Keywords index

    E-print Network

    Boyer, Edmond

    Index des mots-clés Keywords index A Abies, 823 Abies alba, 265 acacia, 93 Acacia cyanophylla Lindl. grandis, 445 E. tereticornis, 445 early fire, 185 earlywood, 511 ecology, 823 ecophysiology, 823 grandis, 675 F Fagus sylvatica L., 761 fertility, 233 fiber, property, 491 fibre biometry, 283 finite

  2. Experimental immunologically mediated aplastic anemia (AA) in mice: cyclosporin A fails to protect against AA

    SciTech Connect

    Knospe, W.H.; Steinberg, D.; Gratwohl, A.; Speck, B.

    1984-07-01

    Immunologically mediated aplastic anemia (AA) in mice was induced by the i.v. injection of 10(7) lymph node cells (LNC) from H-2k identical but Mls mismatched CBA/J donor mice into previously irradiated (600 rad total body gamma) C3H/HeJ mice. Cyclosporin A (CsA), 25 mg/kg, was administered subcutaneously from day -1 to day 30. Control mice included C3H/HeJ mice which received 600 rad alone, C3H/HeJ mice which received 600 rad plus CsA as above, and C3H/HeJ mice which received 600 rad total body irradiation followed by 10(7) LNC from CBA/J donors. CsA failed to prevent lethal AA. These results suggest that the pathogenetic mechanisms operating in immunologically mediated AA differ from the mechanisms operating in rodents transplanted with allogeneically mismatched marrow or spleen cells which develop graft-versus-host disease. The results are consistent with a non-T cell-dependent mechanism causing the AA.

  3. Impact resistance of AA6005 panels

    NASA Astrophysics Data System (ADS)

    Clausen, A. H.; Borvik, T.; Hopperstad, O. S.; Langseth, M.

    2003-09-01

    The interest regarding use of extruded aluminium panels as lightweight protective structures is cmrently increasing. Even so, there are few experimental and computational investigations considering such structures. This paper presents some perforation tests on AA6005-T6 aluminium panels impacted by ogival-nose steel projectiles, where special emphasis was paid to the determination of the ballistic limit. Moreover, a material test programme including high strain rate tests using a split-Hopkinson tension bar was carried out in order to calibrate the Johnson-Cook constitutive model. Results from numerical analyses with LS-DYNA are finally included.

  4. Atlas of Vega: 3850 -- 6860 \\AA

    E-print Network

    Kim, Hyun-Sook; Valyavin, G; Lee, Byeong-Cheol; Shimansky, V; Galazutdinov, G A

    2009-01-01

    We present a high resolving power ($\\lambda$ / $\\Delta\\lambda$ = 90,000) and high signal-to-noise ratio ($\\sim$700) spectral atlas of Vega covering the 3850 -- 6860 \\AA wavelength range. The atlas is a result of averaging of spectra recorded with the aid of the echelle spectrograph BOES fed by the 1.8-m telescope at Bohyunsan observatory (Korea). The atlas is provided only in machine-readable form (electronic data file) and will be available in the SIMBAD database upon publication.

  5. Statistics of isolated and complex geomagnetic storms based on the APEV database for cycle 23 of solar activity

    NASA Astrophysics Data System (ADS)

    Veselovsky, I. S.; Lukashenko, A. T.

    2013-09-01

    The development of geomagnetic storms is mainly controlled by external heliospheric factors, which in turn depend on the conditions on the Sun. Magnetospheric disturbances can be isolated, repeated, multiple, or turbulent, depending on these conditions. Most geomagnetic storms develop complexly and are characterized by the existence of one or several side extrema before or after the main one. This is mainly related to the superposition of individual disturbances that follow immediately one after another from the Sun into the heliosphere or to the internal structure and dynamics of disturbances in the corona. The geomagnetic storms from the APEV extensive database for cycle 23 of solar activity, which were combined into 227 events, were analyzed in order to reveal the statistics based on single and multiple magnetospheric disturbances. The results are presented as histograms, graphs, tables, and empirical formulas for the total number of intensifications in all events and depending on different geomagnetic storm development phases, amplitude, and duration.

  6. A time-compressed simulated geomagnetic storm influences the nest-exiting flight angles of the stingless bee Tetragonisca angustula.

    PubMed

    Esquivel, D M S; Corrêa, A A C; Vaillant, O S; de Melo, V Bandeira; Gouvêa, G S; Ferreira, C G; Ferreira, T A; Wajnberg, E

    2014-03-01

    Insects have been used as models for understanding animal orientation. It is well accepted that social insects such as honeybees and ants use different natural cues in their orientation mechanism. A magnetic sensitivity was suggested for the stingless bee Schwarziana quadripunctata, based on the observation of a surprising effect of a geomagnetic storm on the nest-exiting flight angles. Stimulated by this result, in this paper, the effects of a time-compressed simulated geomagnetic storm (TC-SGS) on the nest-exiting flight angles of another stingless bee, Tetragonisca angustula, are presented. Under an applied SGS, either on the horizontal or vertical component of the geomagnetic field, both nest-exiting flight angles, dip and azimuth, are statistically different from those under geomagnetic conditions. The angular dependence of ferromagnetic resonance (FMR) spectra of whole stingless bees shows the presence of organized magnetic nanoparticles in their bodies, which indicates this material as a possible magnetic detector. PMID:24463619

  7. Sporadic and recurrent geomagnetic disturbances in 1859–1860 according to the archived data from the Russian network of stations

    Microsoft Academic Search

    I. S. Veselovsky; K. Mursula; N. G. Ptitsyna; M. I. Tyasto; O. S. Yakovchouk

    2009-01-01

    Based on an analysis of the available archived data from the Russian network of geomagnetic stations, it has been indicated\\u000a that the known event of August–September 1859 was the first and the greatest event in the series of the recurrent geomagnetic\\u000a storms. Similar series were repeatedly observed in the next years. These series are caused by the processes on the

  8. Continuous record of geomagnetic field intensity between 4.7 and 2.7 Ma from downhole measurements

    Microsoft Academic Search

    J. Thibal; J.-P. Pozzi; V. Barthès; G. Dubuisson

    1995-01-01

    A continuous record of the geomagnetic field intensity from 4.7 to 2.7 Ma has been obtained, together with a precise magnetostratigraphy, from downhole magnetic measurements at Site 884 of ODP Leg 145 in the North Pacific. The record confirms the saw-tooth pattern of geomagnetic field intensity proposed by Valet et Meynadier [10]. Reversals are characterized by a steep intensity decrease

  9. Unstable Angina Treatment in Various Periods of Geomagnetic Activity

    NASA Astrophysics Data System (ADS)

    Parshina, S. S.; Tokayeva, L. K.; Afanasiyeva, T. N.; Samsonov, S. N.; Petrova, V. D.; Dolgova, E. M.; Manykina, V. I.; Vodolagina, E. S.

    In 145 patients with unstable angina (UA) there was analized an efficiency of a drug therapy at different types of heliogeophysical activity (HA) during the 23th solar cycle. 83 patients were examined at the period of a lower HA (Kp-index 16,19±0,18), and 62 patients - at the period of a higher HA (Kp-index 17,25±0,21, p<0,05). Baseline severity of patients' condition with UA at the moment of hospitalization at the studied periods did not differ, but the effectiveness of the therapy depended on the period of HA. At the period of a higher HA antianginal effect was stronger than at the lower period of HA (2,27±0,16 points and 1,75±0,12 points, p<0,05), and the need in nitroglycerin on the background of a drug therapy disappeared for 5-7 days quicker than at the period of a lower HA. Maximal hypotensive effect at a higher HA was achieved quicker - on the 3rd day of the treatment, and at a lower HA - only up to hospital discharge (p<0,05). Blood viscosity did not normalize in both of the studied periods, but in small vessels there was noted a decrease of a BV (p<0,05). So, at a higher HA the effectiveness of a drug therapy in patients with UA is higher than at the period of a lower HA.

  10. Indexing Valid Time Intervals

    Microsoft Academic Search

    Tolga Bozkaya Meral Ozsoyoglu

    1998-01-01

    To support temporal operators and to increase the efficiency of temporal queries,indexing based on temporal attributes is required. We consider the problem of indexing thetemporal dimension in valid time databases. We assume that the temporal information of dataobjects are represented as valid time intervals that have to be managed dynamically by anefficient index structure. Unlike the time intervals in transaction

  11. Dow Jones Internet Indexes

    NSDL National Science Digital Library

    Dow Jones Indexes has created the Dow Jones Internet Index (DJII) to bring "an ordered perspective" to "the seeming chaos of Internet stocks." The new index includes companies that generate a minimum of 50 percent of their revenues from the Internet. Complete documentation of DJII components, data, historical values, and news are provided on-site.

  12. Machine-Aided Indexing.

    ERIC Educational Resources Information Center

    Jacobs, Charles R.

    Progress is reported at the 1,000,000 word level on the development of a partial syntatic analysis technique for indexing text. A new indexing subroutine for hyphens is provided. New grammars written and programmed for Machine Aided Indexing (MAI) are discussed. (ED 069 290 is a related document) (Author)

  13. Oligomerization of Cry11Aa from Bacillus thuringiensis Has an Important Role in Toxicity against Aedes aegypti?

    PubMed Central

    Muñoz-Garay, Carlos; Rodríguez-Almazán, Claudia; Aguilar, Jose N.; Portugal, Leivi; Gómez, Isabel; Saab-Rincon, Gloria; Soberón, Mario; Bravo, Alejandra

    2009-01-01

    Cry11Aa and Cyt1Aa of Bacillus thuringiensis are active against mosquitoes and show synergism. Cyt1Aa functions as a membrane receptor inducing Cry11Aa oligomerization. Here we characterized Cry11Aa helix ?-3 mutants impaired in oligomerization and toxicity against Aedes aegypti, indicating that oligomerization of Cry11Aa is important for toxin action. Cyt1Aa did not recover the insecticidal activity of Cry11Aa mutants. PMID:19820153

  14. Spring-fall asymmetry of substorm strength, geomagnetic activity and solar wind: Implications for semiannual variation and solar hemispheric asymmetry

    USGS Publications Warehouse

    Mursula, K.; Tanskanen, E.; Love, J.J.

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993-2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation, with equinoctial maxima alternating between Spring in solar cycle 22 and Fall in cycle 23. The largest annual variations were found in 1994 and 2003, in the declining phase of the two cycles when high-speed streams dominate the solar wind. A similar, large annual variation is found in the solar wind driver of substorms and geomagnetic activity, which implies that the annual variation of substorm strength, substorm efficiency and geomagnetic activity is not due to ionospheric conditions but to a hemispherically asymmetric distribution of solar wind which varies from one cycle to another. Our results imply that the overall semiannual variation in global geomagnetic activity has been seriously overestimated, and is largely an artifact of the dominant annual variation with maxima alternating between Spring and Fall. The results also suggest an intimate connection between the asymmetry of solar magnetic fields and some of the largest geomagnetic disturbances, offering interesting new pathways for forecasting disturbances with a longer lead time to the future. Copyright ?? 2011 by the American Geophysical Union.

  15. Spring-fall asymmetry of substorm strength, geomagnetic activity and solar wind: Implications for semiannual variation and solar hemispheric asymmetry

    USGS Publications Warehouse

    Marsula, K.; Tanskanen, E.; Love, J.J.

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993–2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation, with equinoctial maxima alternating between Spring in solar cycle 22 and Fall in cycle 23. The largest annual variations were found in 1994 and 2003, in the declining phase of the two cycles when high-speed streams dominate the solar wind. A similar, large annual variation is found in the solar wind driver of substorms and geomagnetic activity, which implies that the annual variation of substorm strength, substorm efficiency and geomagnetic activity is not due to ionospheric conditions but to a hemispherically asymmetric distribution of solar wind which varies from one cycle to another. Our results imply that the overall semiannual variation in global geomagnetic activity has been seriously overestimated, and is largely an artifact of the dominant annual variation with maxima alternating between Spring and Fall. The results also suggest an intimate connection between the asymmetry of solar magnetic fields and some of the largest geomagnetic disturbances, offering interesting new pathways for forecasting disturbances with a longer lead time to the future.

  16. Long range pre-seismic geomagnetic effect related to M9 Great Tohoku earthquake on 11 March 2011

    NASA Astrophysics Data System (ADS)

    Stanica, Dragos-Armand; Stanica, Dumitru; Vladimirescu, Nicoleta

    2014-05-01

    It is supposed that prior to a large earthquake its foci may send through the Earth crust long-range effect of strain-related to transient signals, sometimes strong, but more often very weak and fleeting. Passing through the crust, these signals give rise to geomagnetic variations which are propagated over a wide range of frequencies. Consequently, in this paper, we retrospectively analyzed the geomagnetic data collected at three observatories placed in Japan (Memambetsu, Kakioka) and Romania (Provita de Sus), to confirm same pre-seismic anomalous geomagnetic effect related to the M9 Great Tohoku earthquake occurred on March 11, 2011.The daily mean distributions of the geomagnetic parameter Bzn = Bz/Bperp (where: Bz is vertical component of the geomagnetic field; Bperp is geomagnetic component perpendicular to the strike orientation) and its standard deviation (SD) are performed in the frequency range (0.001Hz to 0.016Hz), by using the FFT band-pass filter analysis. After analyzing the pre-seismic anomalous values obtained at Memambetsu, Kakioka and Provita de Sus observatories, applying a standardized random variable equation, a pre-seismic peak greater than 2.5SD related to the M9 Tohoku earthquake was identified on 5-6 February 2011. The lead time is 32 days before the M9 Tohoku earthquake occurrence. The final conclusion is that the area of precursor detection, under favorable conditions, could be extended to considerable distances from the epicenter of large earthquake.

  17. Idiopathic systemic AA-amyloidosis in a skunk (Mephitis mephitis).

    PubMed

    Elhensheri, Mohamed; Linke, Reinhold P; Blankenburg, Anja; Beineke, Andreas

    2012-03-01

    This report describes a case of systemic amyloidosis in a captive striped skunk. At necropsy, bilateral alopecia, as well as reno-, hepato-, and splenomegaly were present. Congo red staining and immunohistochemistry revealed depositions of AA-amyloid in different organs. The lack of a predisposing disease is suggestive of idiopathic systemic AA-amyloidosis. PMID:22448530

  18. Roadmap: Radiologic Imaging Sciences -Computed Tomography (with AAS Radiologic Technology) -

    E-print Network

    Sheridan, Scott

    Roadmap: Radiologic Imaging Sciences - Computed Tomography (with AAS Radiologic Technology) - Bachelor of Radiologic and Imaging Sciences Technology [RE-BRIT-RIS-CTRT] Regional College Catalog Year Hours] Note: Students must have earned an AAS degree in Radiologic Technology (69-71 semester credits

  19. Roadmap: Radiologic Imaging Sciences -Computed Tomography (with AAS Radiologic Technology) -

    E-print Network

    Sheridan, Scott

    Roadmap: Radiologic Imaging Sciences - Computed Tomography (with AAS Radiologic Technology) - Bachelor of Radiologic and Imaging Sciences Technology [RE-BRIT-RIS-CTRT] Regional College Catalog Year Hours] Note: Students must have earned an AAS degree in Radiologic Technology (42 semester credits

  20. Analysis of geomagnetic data and cosmic ray variations in periods of magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Mandrikova, Oksana; Zalyaev, Timur; Solovev, Igor; Shevtsov, Boris

    indent=0.63cm In the present paper we have suggested a model of the geomagnetic field variation, which allows us to present the characteristic variation of the field and local perturbations formed in periods of increased geomagnetic activity. The model is based on wavelets and has the following form: [ f(t)= sum_n c_{j,n} phi_{j,n} + sum_{(j_{dist},n)in I_1} d_{j_{dist},n}Psi_{j_{dist},n}(t) + sum_{(j_{dist},n)in I_2} d_{j_{dist},n}Psi_{j_{dist},n}(t) + e(t) ] where component sum_n c_{j,n} phi_{j,n} presents the characteristic variation; component \\sum_{(j_{dist},n)in I_1} d_{j_{dist},n}Psi_{j_{dist},n}(t) presents weak geomagnetic perturbations; component \\sum_{(j_{dist},n)in I_2} d_{j_{dist},n}Psi_{j_{dist},n}(t) presents strong geomagnetic perturbations; j is the scale; I_1, I_2 are the sets of indices; e(t) is the noise; Psi_j = \\{Psi_{j,n}\\}_{n in Z} is the wavelet basis; phi_j = \\{phi_{j,n}\\}_{n in Z} is the scaling function; c_{j,n}=< f, phi_{j,n} > ,d_{j,n}=< f, Psi_{j,n} >. Using the proposed model we have developed a technique of identifying the characteristic variation of the geomagnetic field (in periods of quiet magnetosphere) and components presenting different conditions of the field in periods of perturbations. The technique can be used for various data registration stations and is useful for studying the dynamics of electric current systems in the magnetosphere, the interaction between such systems, and their spatial and temporal distribution. We have also created special rules for estimating the storminess degree of the geomagnetic field. The suggested theoretical tools allow us to determine time points when geomagnetic perturbations arise and to obtain quantitative estimates of the storminess degree. Furthermore, it is also possible to implement these rules in the automatic mode. The theoretical tools mentioned above are also aimed at developing and improving mathematical tools for estimating and monitoring the condition of the geomagnetic field and predicting strong magnetic storms. Using the combination of the wavelet transform and neural networks, we have developed a technique of approximating the time variation of cosmic-ray data. This technique allows us to perform detailed analysis of geomagnetic data and detect anomalies in periods of high solar activity. Approximations of large-scale time variation components of cosmic-ray data have been obtained in the following form: [ c_{j,n+1}(t)=\\varphi^3_m Biggl (sum_i omega^3_{mi}\\varphi^2_i biggl (sum_l omega^2_{il}\\varphi^1_lBigl(sum_n omega^1_{ln}c_{j,n}(t)Bigr )biggr ) Biggr ) ] where c_{j,n}=< y, phi_{j,n} > ;phi_{j,n}=2(j/2) phi(2(j(t)-n)) is the scaling function, omega(1_{ln}) are the weights of the neurons of the network input layer l,omega(2_{il}) are the weights of the neurons of the network hidden layer i, omega(3_{mi}) are the weights of the neurons of the network output layer m, varphi(1_l(z)=varphi^2_i(z)=(2)/(1+exp(-2z))-1) ,varphi(3_m(z)) =a*z+b. Coefficients c_{j,n} are the result of transforming of the original function y to the space with the scale j. Analysis of long geomagnetic data from the Paratunka observatory (Kamchatka region, Russia) provided quantitative estimates of the storminess degree of the geomagnetic field before and during magnetic storms. Furthermore, we have managed to identify local weak increases of the field perturbations prior to the main phase of storms. The intensity of field perturbations rises on average 2.5 days before the onset of a storm. Abnormal time periods connected with increased solar activity have been detected in the flow of cosmic rays. Comparison of the results with the geomagnetic data has shown that the anomalies in the cosmic ray variations occur in periods of strong geomagnetic perturbations. The tools and techniques suggested in the present work, together with other methods of data -analysis will help forecast space weather, estimate more accurately the condition of the Earth’s magnetic field, and identify periods when the intensity of cosmic rays rises significantl