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1

Solar variability and climate change: Geomagnetic aa index and global surface temperature  

Microsoft Academic Search

During the past ~120 years, Earth's surface temperature is correlated with both decadal averages and solar cycle minimum values of the geomagnetic aa index. The correlation with aa minimum values suggests the existence of a long-term (low-frequency) component of solar irradiance that underlies the 11-year cyclic component. Extrapolating the aa-temperature correlations to Maunder Minimum geomagnetic conditions implies that solar forcing

E. W. Cliver; V. Boriakoff; J. Feynman

1998-01-01

2

Solar variability and climate change: Geomagnetic aa index and global surface temperature  

NASA Astrophysics Data System (ADS)

During the past ˜120 years, Earth's surface temperature is correlated with both decadal averages and solar cycle minimum values of the geomagnetic aa index. The correlation with aa minimum values suggests the existence of a long-term (low-frequency) component of solar irradiance that underlies the 11-year cyclic component. Extrapolating the aa-temperature correlations to Maunder Minimum geomagnetic conditions implies that solar forcing can account for ˜50% or more of the estimated ˜0.7-1.5°C increase in global surface temperature since the second half of the 17th century. Our analysis is admittedly crude and ignores known contributors to climate change such as warming by anthropogenic greenhouse-gases or cooling by volcanic aerosols. Nevertheless, the general similarity in the time-variation of Earth's surface temperature and the low-frequency or secular component of the aa index over the last ˜120 years supports other studies that indicate a more significant role for solar variability in climate change on decadal and century time-scales than has previously been supposed. The most recent aa data for the current solar minimum suggest that the long-term component of solar forcing will level off or decline during the coming solar cycle.

Cliver, E. W.; Boriakoff, V.; Feynman, J.

3

Update on the correlation between the cosmic-radiation intensity and the geomagnetic aa index  

SciTech Connect

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

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

1985-01-01

4

Long-term biases in geomagnetic K and aa indices  

USGS Publications Warehouse

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

Love, J. J.

2011-01-01

5

Forecasting geomagnetic activities from the Boyle Index  

NASA Astrophysics Data System (ADS)

The Boyle Index (BI), ? =10-4}( {v{2}/{km/sec) + 11.7({(B)/(nT)})sin 3}{(? /2) kV, has been successful in predicting the geomagnetic activity since its inception in October 2003. It is available in near-real-time from http://space.rice.edu/ISTP/wind.html and provides space weather predictions of geomagnetic indices (Kp, Dst and the AE) in real time through neural network algorithms. In addition, it provides free email alerts to its 700+ subscribers whenever the magnetospheric activity levels exceed certain pre-defined thresholds. We are constantly improving our algorithms, in the interest of either including more data or improving the accuracy and lead-time of forecasts. For example, with the inclusion of two more years of data (2008 and 2009) in the training, we have the advantage of modeling one of the deepest solar minimums, which has been exceptionally low in terms of the activity level. Our algorithms have been successful in capturing the effects of ``preconditioning" and the non-linearity in the solar wind parameters (for example, see figure 1). This paper presents our new attempts to include the effects of solar turbulence by incorporating the standard deviations in the solar wind parameters along with the BI, for greater the turbulence the higher the energy input into the magnetosphere as some of the previous studies have shown. Furthermore, we will also present how 3-hour averaged 1-hour sliding window scheme have improved our predictions with lead times of 3 hours or longer. Our predictions from a recent activity, 03 August 2010.

Bala, R.; Reiff, P. H.

2010-12-01

6

Flare index of solar activity and global geomagnetic variability.  

NASA Astrophysics Data System (ADS)

The associations of solar flare index (SFI) and global geomagnetic variability (Ap) with annual mean sunspot number (SSN) during the period 1986 - 96 have been analysed. It is found that the SFI in the northern hemisphere, southern hemisphere and total disk surface of the Sun shows close correspondence with the SSN on long- and short-term basis. An internal association between SSN, SFI and Ap has also been analysed. The authors have found that Ap poorly correlated with SFI and SSN during the aforesaid period.

Dubey, S. C.; Mishra, A. P.

2000-06-01

7

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

NASA Technical Reports Server (NTRS)

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.

Lyatsky, Wladislaw; Khazanov, George V.

2008-01-01

8

INTERPRETATION OF Kp INDEX AND M-REGION GEOMAGNETIC STORMS  

Microsoft Academic Search

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

A. J. Dessler; Fejer J. A

1963-01-01

9

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

10

Annual variation of geomagnetic activity  

NASA Astrophysics Data System (ADS)

The annual variation of geomagnetic activity is studied through the geomagnetic indices aa, Dst and AE, according to different levels of intensity for each of the indices. For thresholds that correspond from moderate to fairly intense storms (i.e., peak aa? 90), the distribution follows the well-known pattern of a seasonal variation, with maxima around the equinoxes and minima near the solstices. Deviations from this behavior are observed when the distribution refers to levels associated with the occurrence of more intense storms. In particular, the annual distribution of days with a geomagnetic index aa greater than about 90, shows the occurrence of a peak in July. The contribution of very intense storms ( aa? 210) to the July peak, seems to be evenly distributed along the 12 solar cycles covered by this index. Furthermore, the indices Dst and AE, although restricted to a much shorter interval of time (they have been recorded only since 1957), seem as well to show the existence of a peak of occurrence for July. The study done for the indices Dst and AE gives some indication for the existence of another peak in November, also for thresholds associated with intense storms. However, due to the lack of longer records for these indices, the real existence of this peak in the geomagnetic activity is questionable. A statistical analysis of the distribution of events according to the levels of intensity of the aa and Dst is also presented. From this analysis it is seen that the number of occurrences of storms above a given level of intensity of those geomagnetic indices, can be approximated by an exponential law. Furthermore, an estimation of the occurrence of storms during a solar cycle as a function of the peak aa (or aa ?) has been also done.

L. Clúa de Gonzalez, Alicia; M. Silbergleit, Virginia; D. Gonzalez, Walter; T. Tsurutani, Bruce

11

Annual variation of geomagnetic activity  

NASA Astrophysics Data System (ADS)

The annual variation of geomagnetic activity is studied through the geomagnetic indices /aa, /Dst and /AE, according to different levels of intensity for each of the indices. For thresholds that correspond from moderate to fairly intense storms (i.e., peak /aa>= 90), the distribution follows the well-known pattern of a seasonal variation, with maxima around the equinoxes and minima near the solstices. Deviations from this behavior are observed when the distribution refers to levels associated with the occurrence of more intense storms. In particular, the annual distribution of days with a geomagnetic index /aa greater than about 90, shows the occurrence of a peak in July. The contribution of very intense storms (/aa>= 210) to the July peak, seems to be evenly distributed along the 12 solar cycles covered by this index. Furthermore, the indices /Dst and /AE, although restricted to a much shorter interval of time (they have been recorded only since 1957), seem as well to show the existence of a peak of occurrence for July. The study done for the indices /Dst and /AE gives some indication for the existence of another peak in November, also for thresholds associated with intense storms. However, due to the lack of longer records for these indices, the real existence of this peak in the geomagnetic activity is questionable. A statistical analysis of the distribution of events according to the levels of intensity of the /aa and /Dst is also presented. From this analysis it is seen that the number of occurrences of storms above a given level of intensity of those geomagnetic indices, can be approximated by an exponential law. Furthermore, an estimation of the occurrence of storms during a solar cycle as a function of the peak /aa (or aa*) has been also done.

Clúa de Gonzalez, A. L.; Silbergleit, V. M.; Gonzalez, W. D.; Tsurutani, B. T.

2001-03-01

12

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

13

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

NASA Astrophysics Data System (ADS)

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

Balasubramanian, Ramkumar

2010-11-01

14

Geomagnetic climatology  

Microsoft Academic Search

An account is given of the NOAA Space Environment Services Center's efforts to forecast the geomagnetic 3-hourly K and daily A indices for locations in Virginia and Alaska, on the basis of 29 years (1957-1985) of K-index climatologies. At the Alaskan, high-geomagnetic latitude station, a strong diurnal variation is seen, with K-index values of 5 or more being present 30

J. A. Joselyn; J. A. Flueck; T. Brown

1988-01-01

15

Review of selected geomagnetic activity indices  

NASA Technical Reports Server (NTRS)

Magnetic activity indexes are reviewed. Classifications of magnetograms from single observatories and the global range of potential associated with the equivalent currents which could have produced the variations monitored at a large array of recording sides are addressed. Principal magnetic activity indexes discussed include: the auroral electrojet index and its associated indexes (AU, AL and AO) useful for auroral zone studies; the Kp, ap, aa and am indexes which are measures of midlatitude geomagnetic activity; and the Dst index of magnetic activity recorded at low latitudes. It is concluded that geomagnetic activity indexes are useful in studies of the interaction between solar activity, the interplanetary magnetic field and solar wind, the magnetosphere, ring current, field aligned currents, and ionospheric currents.

Allen, J. H.; Feynman, J.

1979-01-01

16

Some Fractal Dimension Algorithms and Their Application to Time Series Associated with the Dst a Geomagnetic Index  

NASA Astrophysics Data System (ADS)

ABSTRACT: Chaotic invariants like fractal dimensions are used to characterize non-linear time series. The fractal dimension is an important characteristic of fractals that contains information about their geometrical structure at multiple scales. In this work four fractal dimension estimation algorithms are applied to non-linear time series. The algorithms employed are the Higuchi's algorithm, the Petrosian's algorithm, the Katz's Algorithm and the Box counting method. The analyzed time series are associated with natural phenomena, the Dst a geomagnetic index which monitors the world wide magnetic storm; the Dst index is a global indicator of the state of the Earth's geomagnetic activity. The time series used in this work show a behavior self-similar, which depend on the time scale of measurements. It is also observed that fractal dimensions may not be constant over all time scales.

Cervantes, F.; Gonzalez, J.; Real, C.; Hoyos, L.

2012-12-01

17

Is geomagnetic activity increasing?  

NASA Astrophysics Data System (ADS)

Geomagnetic-activity indices are simple summary metrics of magnetic-field activity derived from data acquired at ground-based observatories. The K index records the maximum variational range of magnetic-field disturbance over 3-hr durations of time at each individual observatory. The global-activity aa index is derived from K values from a pair of observatories, one in the northern hemisphere (Britain) and one in the southern hemisphere (Australia). Since the aa time series extends from 1868 to the present, it is often used for studies of long-term trends. In this study we examine the source K values used for constructing aa, and we compare them with K values from Germany (1890-present). While we identify numerous problems and biases in aa, we also find that it does provide a qualitative measure of long-term change in global-scale geomagnetic activity, which, in addition to showing an 11-year solar-cycle modulation, has generally been increasing over the past 140 years. More definitive conclusions can be drawn from consistent patterns in the (independently measured) K indices from different observatories: (1) The well-known tendency for magnetic storms to occur during the declining phase of a solar cycle was not clearly seen until about 1902, with the commencement of solar cycle 14; or, at least, it was not obviously present in solar cycles 11-13. (2) Since about 1954, with the commencement of solar cycle 19, magnetic quiescence has diminished disproportionately when compared to trends in sunspot number. (3) Extrapolations of past trends in solar and geomagnetic activity levels are unlikely to be useful for making quantitative predictions. (4) No significant correlation exists from 1868-present between geomagnetic activity and Earth’s global surface temperature, nor, indeed, between sunspot number and global surface temperature. These observations have implications for solar physics, geophysics, and for space-weather prediction and hazard mitigation. They also highlight the value of both continuous long-term monitoring and preserving historical data in their original and unaltered numerical form.

Love, J. J.

2010-12-01

18

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

NASA Astrophysics Data System (ADS)

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 S4 and ?? are stored in real time from an array of high-rate scintillation receivers of the Canadian High Arctic Ionospheric Network (CHAIN). Ionospheric phase scintillation was observed at high latitudes during a moderate geomagnetic storm (Dst = -61 nT) that was caused by a moderate solar wind plasma stream compounded with the impact of two coronal mass ejections. The most intense phase scintillation (?? ~ 1 rad) occurred in the cusp and the polar cap where it was co-located with a strong ionospheric convection, an extended tongue of ionisation and dense polar cap patches that were observed with ionosondes and HF radars. At sub-auroral latitudes, a sub-auroral polarisation stream that was observed by mid-latitude radars was associated with weak scintillation (defined arbitrarily as ?? < 0.5 rad). In the auroral zone, moderate scintillation coincided with auroral breakups observed by an all-sky imager, a riometer and a magnetometer in Yellowknife. To overcome the limited geographic coverage by GISTMs other GNSS data sampled at 1 Hz can be used to obtain scintillation proxy indices. In this study, a phase scintillation proxy index (delta phase rate, DPR) is obtained from 1-Hz data from CHAIN and other GPS receivers. The 50-Hz and 1-Hz phase scintillation indices are correlated. The percentage occurrences of ?? > 0.1 rad and DPR > 2 mm s-1, both mapped as a function of magnetic latitude and magnetic local time, are very similar.

Prikryl, P.; Ghoddousi-Fard, R.; Kunduri, B. S. R.; Thomas, E. G.; Coster, A. J.; Jayachandran, P. T.; Spanswick, E.; Danskin, D. W.

2013-05-01

19

Prominent short-, mid-, and long-term periodicities in solar and geomagnetic activity: Wavelet analysis  

NASA Astrophysics Data System (ADS)

Study of periodicities in solar and geomagnetic parameters has been useful in relating solar variability to variations in other phenomena in order to search for the solar cause of, and effects in, the variability observed in near earth space environment. Implementing wavelet analysis on daily, monthly and yearly time resolution data of sunspot number and geomagnetic aa-index, we observed periodicities of 27.8-, 157-, 370-days, and 2.2-, 5.5-, 11-, 22.7-, 38.6-years in the sunspot spot number and 13.8-, 26.6-, 185-days, and 5.3-, 11-, 30-, 46-years in the geomagnetic aa-index. We discuss these periodicities, relation between solar and geomagnetic periodicities and their implications for near-earth space environmental effects. Daily, monthly and yearly solar and geomagnetic data analyzed using wavelet analysis. Several periodicities detected in solar and geomagnetic data. Signature of 38.6-year periodicity observed in sunspot data. Six month (semi-annual) cycle prominently seen in aa-index. The ~30-year periodicity observed in aa-index using daily, monthly and yearly data.

Singh, Y. P.; Badruddin

2014-06-01

20

Geomagnetic climatology  

NASA Astrophysics Data System (ADS)

An account is given of the NOAA Space Environment Services Center's efforts to forecast the geomagnetic 3-hourly K and daily A indices for locations in Virginia and Alaska, on the basis of 29 years (1957-1985) of K-index climatologies. At the Alaskan, high-geomagnetic latitude station, a strong diurnal variation is seen, with K-index values of 5 or more being present 30 percent of the time between 0900 and 1500 UT. A seasonal variation is noted upon filtering of the monthly data. No direct correlation with the sunspot cycle appears to be establishable over this 29-year period.

Joselyn, J. A.; Flueck, J. A.; Brown, T.

1988-12-01

21

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

22

Solar wind density effect on the night-side geomagnetic activity (AL index)  

NASA Astrophysics Data System (ADS)

The role of solar wind density in driving of geomagnetic activity is now again in the focus of attention of magnetospheric scientists. We analyze 20 years of hourly AL and OMNI solar wind data to reveal the basic solar wind flow influence on the magnitude of night-side geomagnetic activity and magnetotail dynamics. In such a data set trigger-related specifics of substorm onsets are averaged out. The more pronounced effects of the solar wind speed and interplanetary magnetic field on AL need to be eliminated before the analysis of the smaller density role. With an iterative method we determine the best formula, accounting for the velocity and magnetic field contribution: E=VBy2/2+Bz2sin(?/2)+?Vsin(?/2). Average AL proved to be not sensitive to density changes, when density was above ˜5cm, and average |AL| dropped by ˜30%, when density decreased from 5 to 1cm.

Petrukovich, A. A.

2006-11-01

23

Schizophrenia and season of birth: relationship to geomagnetic storms.  

PubMed

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

Kay, Ronald W

2004-01-01

24

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

USGS Publications Warehouse

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.

Gannon, J.L.

2012-01-01

25

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

USGS Publications Warehouse

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

Gannon, Jennifer

2012-01-01

26

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

27

Dependence of Energetic Electron Precipitation on the Geomagnetic Index Kp and Electron Energy  

NASA Astrophysics Data System (ADS)

It has long been known that the magnetospheric particles can precipitate into the atmosphere of the Earth. In this paper we examine such precipitation of energetic electrons using the data obtained from low-altitude polar orbiting satellite observations. We analyze the precipitating electron flux data for many periods selected from a total of 84 storm events identified for 2001-2012. The analysis includes the dependence of precipitation on the Kp index and the electron energy, for which we use three energies E1 > 30 keV, E2 > 100 keV, E3 > 300 keV. We find that the precipitation is best correlated with Kp after a time delay of < 3 hours. Most importantly, the correlation with Kp is notably tighter for lower energy than for higher energy in the sense that the lower energy precipitation flux increases more rapidly with Kp than does the higher energy precipitation flux. Based on this we suggest that the Kp index reflects excitation of a wave that is responsible for scattering of preferably lower energy electrons. The role of waves of other types should become increasingly important for higher energy, for which we suggest to rely on other indicators than Kp if one can identify such an indicator.

Park, Mi-Young; Lee, Dae-Young; Shin, Dae-Kyu; Cho, Jung-Hee; Lee, Eun-Hee

2013-12-01

28

Long-term correlation between solar and geomagnetic activity  

NASA Astrophysics Data System (ADS)

A long-term correlation study between solar and geomagnetic activity is reported in this work using annual averages of the aa index and of the sunspot number Rz in the period of 1868-2000. Dst and AE geomagnetic indices and solar wind speed data are used for more recent periods. It is shown that the geomagnetic and solar activity correlation has decreased since the end of the 19th century, and the lag between them has increased. The variations of Rz and aa were in phase in the early period (solar cycles 11-14, around 1868-1910), and became out of phase in later periods (with a lag of 2 years in solar cycle 22, with aa maximum after Rz). Nevertheless, this trend is not monotonic and superposed fluctuations are seen, which does not permit determine if this correlation decrease is part or not of a long period solar activity cycle. The probable cause of the correlation decrease seems to be related to the aa index dual peak structure. The second aa peak seems to have increased relative to the first one. This second peak is more related to the high-speed streams originated from co-rotating structures whereas the first one is related to sunspot (coronal mass ejections) activity. In recent periods, since 1964, it has been observed that aa annual values have higher correlation with the fraction of days per year with daily solar wind speed peaks larger than 500km/s(Fpk) than with Rz. The aa index also shows larger correlation with AE index than with Dst. Thus, it seems that average aa is strongly influenced by AE activity, which is influenced mainly by high speed streams from coronal holes. One can conclude that the decrease in correlation between aa and Rz occurs because the second aa peak has becoming stronger relative to the first one. The cause seems to be that open solar magnetic field structures have increased their activity relative to the closed (sunspot-related) solar magnetic field structures. This implies that the global solar magnetic field could have experienced a differential (between closed and open structures) large-scale variation in the last 130 years.

Echer, E.; Gonzalez, W. D.; Gonzalez, A. L. C.; Prestes, A.; Vieira, L. E. A.; dal Lago, A.; Guarnieri, F. L.; Schuch, N. J.

2004-08-01

29

IMF sector behavior deduced from geomagnetic data  

SciTech Connect

Interplanetary magnetic field (IMF) sector structures, such as 'toward' the sun and 'away' from the sun on each day, have been objectivly estimated from daily and monthly mean values of the horizontal component of the geomagnetic variation field at Godhavn during the period 1926--1970. The agreement between this estimation and actual satellite observations of the sector structures of the interval 1964--1970 is 88, 79, and 58% in summer, equinox, and winter, respectively. A remarkable agreement (more than 95%) is obtained for the summers of 1964, 1969, and 1970. Various types of IMF sector behavior are examined by taking this seasonal factor into consideration. Approximately 27-day recurrences of the same structure are often found, and 5- to 14-day consecutive occurrences of the same sector are frequently noted. Furthermore, the total number of occurrences for each estimated sector in each year shows an apparently good correlation with smoothed sunspot numbers and geomagnetic aa index. After a brief introduction of the production mechanism of sector effects on polar geomagnetic fields the limitations and merits of IMF sector inference from geomagnetic data are emphasized.

Matsushita, S.; Trotter, D.E.

1980-05-01

30

A Direct Relation Between Solar Activity Variability and Geomagnetic Disturbances During The Past 130 Years  

NASA Astrophysics Data System (ADS)

We use a Principal Component (PC) analysis technique to study the long term vari- ability in the frequency domain of the sunspot numbers, often referred to as the Wolf- numbers. The long-term variation of the Wolf-number frequency is compared with the long term variation of the geomagnetic AA-index during the past 130 years. We find a close correlation between the long periodic (20-128 days) variation of the Wolf- number (denoted LFW) and the AA-index. This suggests the LFW can be used as a proxy for global geomagnetic disturbances. Similarly, Lockwood et al (1999) found that the geomagnetic AA-index and the solar magnetic flux is well correlated. There- fore, the LFW is likely to be a useful proxy for the solar magnetic flux, ie periods with enhanced LFW is connected with enhanced solar magnetic flux. An important finding is that the Sun has experienced a substantial change in the sunspot frequence domain during the last 150 years, - the high-frequency component (period 2-4 days) decreas- ing , the low-frequency component (period 20-128 days) increasing. These changes must have an impact on the innermost planets in our solar system, the extent still to be determined. A potential result of the long-term solar magnetic flux variability inferred from the LFW is a modification of the global climate as suggested by Svensmark and Friis-Christensen (1997).

Liszka, L.; Lundin, R.; Lundstedt, H.

31

Geomagnetic Activity Indicates Large Amplitude for Sunspot Cycle 24  

NASA Technical Reports Server (NTRS)

The level of geomagnetic activity near the time of solar activity minimum has been shown to be a reliable indicator for the amplitude of the following solar activity maximum. The geomagnetic activity index aa can be split into two components: one associated with solar flares, prominence eruptions, and coronal mass ejections which follows the solar activity cycle and a second component associated with recurrent high speed solar wind streams which is out of phase with the solar activity cycle. This second component often peaks before solar activity minimum and has been one of the most reliable indicators for the amplitude of the following maximum. The size of the recent maximum in this second component indicates that solar activity cycle 24 will be much higher than average - similar in size to cycles 21 and 22.

Hathaway, D. H.; Wilson, R. M.

2006-01-01

32

A new index for the interplanetary merging electric field and geomagnetic activity: Application of the unified polar cap indices  

NASA Astrophysics Data System (ADS)

The polar cap indices, PCN for the northern polar cap and PCS for the southern polar cap, are derived from analysis of magnetic variations in the polar caps. The indices mainly relate to the transpolar ionospheric electric currents generated by the interaction of the solar wind with the magnetosphere. The present paper discusses the relations between the PCN and PCS indices and the interplanetary merging electric field (MEF) with particular emphasis on the correlation of a combined PC index, PCC, with the MEF. The MEF parameter closely correlates with global disturbances such as magnetic storms that are caused by the impact on the magnetosphere of the enhanced solar wind following eruptive solar activity. The new PCC index resolves the ambiguity implied in having two index series to be proxy for the same merging electric field and to represent global magnetic activity. The paper examines the relations between the new polar cap index and the global magnetic activity level represented by the Dst index. It is shown that the Dst index correlates better with the PCC index than with the PCN and PCS indices or the auroral electrojet indices AU, AL, and AE.

Stauning, Peter

2007-09-01

33

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

NASA Technical Reports Server (NTRS)

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.

Wilson, Robert M.; Hathaway, David H.

2008-01-01

34

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)

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.

Wilson, Robert M.; Hathaway, David H.

2008-06-01

35

Nonlinear and nonstationary influences of geomagnetic activity on the winter North Atlantic Oscillation  

NASA Astrophysics Data System (ADS)

The relationship between the geomagnetic aa index and the winter North Atlantic Oscillation (NAO) has previously been found to be nonstationary, being weakly negative during the early 20th century and significantly positive since the 1970s. The study reported here applies a statistical method called the generalized additive modeling (GAM) to elucidate the underlying physical reasons. We find that the relationship between aa index and the NAO during the Northern Hemispheric winter is generally nonlinear and can be described by a concave shape with a negative relation for small to medium aa and a positive relation for medium to large aa. The nonstationary character of the aa-NAO relationship may be ascribed to two factors. First, it is modulated by the multidecadal variation of solar activity. This solar modulation is indicated by significant change points of the trends of solar indices around the beginning of solar cycle 14, 20, and 22 (i.e., ˜1902/1903, ˜1962/1963, and ˜1995/1996). Coherent changes of the trend in the winter time NAO followed the solar trend changes a few years later. Second, the aa-NAO relationship is dominated by the aa data from the declining phase of even-numbered solar cycles, implying that the 27 day recurrent solar wind streams may be responsible for the observed aa-NAO relationship. It is possible that an increase of long-duration recurrent solar wind streams from high-latitude coronal holes during solar cycles 20 and 22 may partially account for the significant positive aa-NAO relationship during the last 30 years of the 20th century.

Li, Yun; Lu, Hua; Jarvis, Martin J.; Clilverd, Mark A.; Bates, Bryson

2011-08-01

36

Geomagnetic observations  

Microsoft Academic Search

Results are summarized for the following areas of investigation: (1) quiet and disturbed day variation in the low and equatorial latitudes; (2) electromagnetic induction; (3) magnetosphere and solar wind; (4) aeronomy; (5) effects of the interplanetary magnetic field; (6) solar terrestrial relationships; (7) geomagnetic lunar daily variations; and (8) sola eclipse effects on HF radio propagation. Data processing, analysis, and

N. M. Marg

1980-01-01

37

Geomagnetic Workshop  

NASA Astrophysics Data System (ADS)

A workshop on geomagnetism, sponsored by the Geologic Division of the U.S. Geological Survey, was held in the Denver West Office Complex in Golden, Colorado, April 13-15, 1982. There were 90 registered participants from government agencies, academic institutions, and industry.This effort stemmed from the realization that geomagnetism, once a small but coherent discipline, has now expanded into numerous areas of the geosciences, yet those doing research in these specialties seldom make contact outside their area of immediate interest. The impetus for this event came from the members of a committee formed to review the geomagnetic activities within the U.S. Geological Survey. They observed that the level of communication between the various elements of this now diverse discipline was inadequate, not only within their organization but also between federal agencies, academia, and the private sector. While the desire was to cover as much of geomagnetism as possible, it was necessary for a workshop of reasonable size and length to exclude some important areas of the subject: magnetic reversal chronology, studies of the externally produced variations, and most aspects of internal induction. The plan was to give emphasis to some of the newer areas: those which have recently seen a high level of activity and those with increasing activity abroad compared to that in the United States. The purpose was to evaluate the status and problems in selected areas with an eye to those whose emphasis might produce fruitful results in the next decade.

DeNoyer, John; Cain, Joseph C.; Banerjee, Subir; Benton, Edward R.; Blakely, Richard J.; Coe, Rob; Harrison, C. G. A.; Johnston, Malcolm; Regan, Robert D.

38

The presence of large sunspots near the central solar meridian at the times of major geomagnetic storms  

NASA Astrophysics Data System (ADS)

A further study is made of the validity of a technique developed by the authors to identify historical occurrences of intense geomagnetic storms, which is based on finding approximately coincident observations of sunspots and aurorae recorded in East Asian histories. Previously, the validity of this technique was corroborated using scientific observations of aurorae in Japan during the interval 1957-2004 and contemporaneous white-light images of the Sun obtained by the Royal Greenwich Observatory, the Big Bear Solar Observatory, the Debrecen Heliophysical Observatory, and the Solar and Heliospheric Observatory spacecraft. The present investigation utilises a list of major geomagnetic storms in the interval 1868-2008, which is based on the magnitude of the AA* magnetic index, and reconstructed solar images based on the sunspot observations acquired by the Royal Greenwich Observatory during the shorter interval 1874-1976. It is found that a sunspot large enough to be seen with the unaided eye by an "experienced" observer was located reasonably close to the central solar meridian for almost 90% of these major geomagnetic storms. Even an "average" observer would easily achieve a corresponding success rate of 70% and this success rate increases to about 80% if a minority of ambiguous situations are interpreted favourably. The use of information on major geomagnetic storms, rather than modern auroral observations from Japan, provides a less direct corroboration of the technique for identifying historical occurrences of intense geomagnetic storms, if only because major geomagnetic storms do not necessarily produce auroral displays over East Asia. Nevertheless, the present study provides further corroboration of the validity of the original technique for identifying intense geomagnetic storms. This additional corroboration of the original technique is important because early unaided-eye observations of sunspots and aurorae provide the only possible means of identifying individual geomagnetic storms during the greater part of the past two millennia.

Willis, D. M.; Henwood, R.; Stephenson, F. R.

2009-01-01

39

Solar causes of the long-term increase in geomagnetic activity  

NASA Astrophysics Data System (ADS)

We analyze the causes of the century-long increase in geomagnetic activity, quantified by annual means of the aa index, using observations of interplanetary space, galactic cosmic rays, the ionosphere, and the auroral electrojet, made during the last three solar cycles. The effects of changes in ionospheric conductivity, the Earth's dipole tilt, and magnetic moment are shown to be small; only changes in near-Earth interplanetary space make a significant contribution to the long-term increase in activity. We study the effects of the interplanetary medium by applying dimensional analysis to generate the optimum solar wind-magnetosphere energy coupling function, having an unprecedentedly high correlation coefficient of 0.97. Analysis of the terms of the coupling function shows that the largest contributions to the drift in activity over solar cycles 20-22 originate from rises in the average interplanetary magnetic field (IMF) strength, solar wind concentration, and speed; average IMF orientation has grown somewhat less propitious for causing geomagnetic activity. The combination of these factors explains almost all of the 39% rise in aa observed over the last three solar cycles. Whereas the IMF strength varies approximately in phase with sunspot numbers, neither its orientation nor the solar wind density shows any coherent solar cycle variation. The solar wind speed peaks strongly in the declining phase of even-numbered cycles and can be identified as the chief cause of the phase shift between the sunspot numbers and the aa index. The rise in the IMF magnitude, the largest single contributor to the drift in geomagnetic activity, is shown to be caused by a rise in the solar coronal magnetic field, consistent with a rise in the coronal source field, modeled from photospheric observations, and an observed decay in cosmic ray fluxes.

Stamper, R.; Lockwood, M.; Wild, M. N.; Clark, T. D. G.

40

[AA Amyloidosis].  

PubMed

Abstract AA amyloidosis is caused by the tissue deposition of AA protein, which is degraded from serum amyloid A (SAA) mainly produced in an inflammatory state. However, AA amyloidosis is hardly observed in neurol-cerebral diseases. Therefore, in this issue, the role of cytokines and activation of signal transducer and activator of transcription 3 (STAT3) in SAA-inducing mechanism are presented. PMID:24998825

Yoshizaki, Kazuyuki

2014-07-01

41

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

NASA Technical Reports Server (NTRS)

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.

Wilson, Robert M.; Hathaway, David H.

2006-01-01

42

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

NASA Astrophysics Data System (ADS)

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.

Wilson, Robert M.; Hathaway, David H.

2006-12-01

43

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

NASA Technical Reports Server (NTRS)

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

Wilson, Robert M.

2014-01-01

44

IMF control of geomagnetic activity  

NASA Technical Reports Server (NTRS)

Recent work on the IMF control of geomagnetic activity is reviewed. The goal is to quantitatively express the temporal relation between the solar wind input and the ionospheric output from the magnetospheric system. Linear prediction filtering was used which treats the magnetosphere as a black box characterized by an impulse response. It is shown that an average impulse response can account for only about 40 percent of the variance in the AL index.

Mcpherron, R. L.; Bargatze, L. F.; Holzer, R. E.; Baker, D. N.; Clauer, C. R.

1988-01-01

45

Prediction of Solar Cycle 24 Using Geomagnetic Precursors: Validation and Update  

NASA Astrophysics Data System (ADS)

In the previous study (Dabas et al. in Solar Phys. 250, 171, 2008), to predict the maximum sunspot number of the current solar cycle 24 based on the geomagnetic activity of the preceding sunspot minimum, the Ap index was used which is available from the last six to seven solar cycles. Since a longer series of the aa index is available for more than the last 10 - 12 cycles, the present study utilizes aa to validate the earlier prediction. Based on the same methodology, the disturbance index (DI), which is the 12-month moving average of the number of disturbed days ( aa?50), is computed at thirteen selected times (called variate blocks 1,2,…,13; each of them in six-month duration) during the declining portion of the ongoing sunspot cycle. Then its correlation with the maximum sunspot number of the following cycle is evaluated. As in the case of Ap, variate block 9, which occurs exactly 48 months after the current cycle maximum, gives the best correlation ( R=0.96) with a minimum standard error of estimation (SEE) of ± 9. As applied to cycle 24, the aa index as precursor yields the maximum sunspot number of about 120±16 (the 90% prediction interval), which is within the 90% prediction interval of the earlier prediction (124±23 using Ap). Furthermore, the same method is applied to an expanded range of cycles 11 - 23, and once again variate block 9 gives the best correlation ( R=0.95) with a minimum SEE of ± 13. The relation yields the modified maximum amplitude for cycle 24 of about 131±20, which is also close to our earlier prediction and is likely to occur at about 43±4 months after its minimum (December 2008), probably in July 2012 (± 4 months).

Dabas, R. S.; Sharma, Kavita

2010-10-01

46

Rating AAs.  

ERIC Educational Resources Information Center

Why alternative investments? In a word: performance. Many higher education endowment and foundation managers are making increasing commitments to alternative investments, or AAs, in order to obtain higher returns and broader diversification for their investment portfolios than public securities instruments can usually provide. Learn how to handle…

Carter, Susan J.

2001-01-01

47

Black box modeling of magnetospheric dynamics to forecast geomagnetic activity  

Microsoft Academic Search

The Kp geomagnetic activity index is an important indicator of geomagnetic disturbances, which mark adverse space weather conditions affecting space missions and causing satellite anomalies. Therefore accurate Kp prediction is essential for warning and alert systems. A black box model, based on a recently developed locally linear neurofuzzy model, is proposed to reconstruct the highly nonlinear and complex dynamics of

Ali Gholipour; Caro Lucas; Babak N. Araabi

2004-01-01

48

Prediction of Solar Cycle 24 Using Geomagnetic Precursors: Validation and Update  

NASA Astrophysics Data System (ADS)

Maximum amplitude of forthcoming solar cycle number 24 is predicted using geomagnetic precursor technique which is based on the correlation of geomagnetic indices (disturbances) prior to the minimum of the sunspot cycle with the magnitude of the ensuing solar cycle maximum. In the previous study Ap index was used as disturbance index which is available from the last 6-7 solar cycle only whereas long series of aa index is available for more than last 10-12 cycles. In the present study, instead of Ap, aa index is used to predict maximum amplitude of solar cycle 24. First, to validate earlier prediction (Dabas et al., 2008, Solar Phys. DOI 10.1007/s11207-008-9200-1), based on cycles 17-23, linear correlations are obtained between 12-month moving averages of the number of disturbed days when aa is greater than or equal to 50, called the disturbance index, DI, at thirteen selected times (called variate blocks 1, 2, . . . each of them in six-month duration) during the declining portion of the ongoing sunspot cycle and the maximum amplitude of the following sunspot cycle. As in the case of Ap, here again, variate block 9, which occurs exactly 48 months after the current cycle maximum or just prior to subsequent cycle minimum, gives the best correlation (0.97) with a minimum standard error of estimation of ±9, and hind casting shows agreement between predicted and observed maximum amplitudes to about 10 percent. As applied to cycle 24, with aa as precursors yields maximum amplitude of about 120±16 (the 90% prediction interval), which is very close to the earlier prediction of 124±23 (the 90% prediction interval) using Ap and hence validating the same. Further, the same method is applied to cycles 11-23 and once again the variate block 9, gives the best correlation (0.95) with a minimum standard error of estimation of ±13. The relation yields modified maximum amplitude for cycle 24 of about 130±20 (the 90% prediction interval) occurring about 44±4 months after its minimum amplitude occurrence (July 2009), probably in February 2013 (±4 months).

Singh Dabas, Raj; Sharma, Kavita; Sarkar, S. K.

49

Introduction to geomagnetism  

SciTech Connect

This book examines a wide range of subjects in geomagnetism. It presents a brief introduction to physical principles of magnetism, and then focuses on the properties of the geomagnetic field as the sum of four interrelated phenomena: the main field, the local or crustal field, the external field, and the induced field. Additional topics, including paleomagnetism and magnetic methods in exploration, and the history of geomagnetism, are also discussed.

Parkinson, W.D.

1983-01-01

50

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.

51

Predicting Solar Cycle 24 Using a Geomagnetic Precursor Pair  

NASA Astrophysics Data System (ADS)

We describe using Ap and F10.7 as a geomagnetic-precursor pair to predict the amplitude of Solar Cycle 24. The precursor is created by using F10.7 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 ? 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 F10.7 shows that F10.7 is higher than the equivalent sunspot number over most of the cycle, implying that the sunspot number underestimates the solar-activity component described by F10.7. 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.

Pesnell, W. Dean

2014-06-01

52

Forecast of recurrent geomagnetic storms  

NASA Astrophysics Data System (ADS)

Long-term forecast of space weather allows in achieving a longer lead time for taking the necessary precautions against disturbances. Hence, there is a need for long-term forecasting of space weather. We studied the possibility for a long-term forecast of recurrent geomagnetic storms. Geomagnetic storms recur with an approximate 27-day period during the declining phase of a solar cycle. These disturbances are caused by the passage of corotating interaction regions, which are formed by interactions between the background slow-speed solar wind and high-speed solar wind streams from a coronal hole. In this study, we report on the performance of 27-day-ahead forecasts of the recurrent geomagnetic disturbances using Kp index. The methods of the forecasts are on the basis of persistence, autoregressive model, and categorical forecast using occurrence probability. The forecasts show better performance during the declining phase of a solar cycle than other phases. The categorical forecast shows the probability of detection (POD) more than 0.5 during the declining phase. Transition of the performance occurs sharply among the declining phases and other phases.

Watari, S.

2011-06-01

53

Two-step development of geomagnetic storms  

Microsoft Academic Search

Using the Dst index, more than 1200 geomagnetic storms, from weak to intense, spanning over three solar cycles have been examined statistically. Interplanetary magnetic field (IMF) and solar wind data have also been used in the study. It is found that for more than 50% of intense magnetic storms, the main phase undergoes a two-step growth in the ring current.

Y. Kamide; N. Yokoyama; W. Gonzalez; B. T. Tsurutani; I. A. Daglis; A. Brekke; S. Masuda

1998-01-01

54

On the causes of geomagnetic activity  

NASA Technical Reports Server (NTRS)

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

Svalgaard, L.

1975-01-01

55

Reconstruction of Geomagnetic activity and near-Earth interplanetary conditions over the past 167 years.  

NASA Astrophysics Data System (ADS)

Records of geomagnetic activity have previously been used to reconstruct the conditions in near-Earth space, such as the interplanetary magnetic field (IMF), solar wind speed (Vsw) and open solar flux (OSF). Reliable geomagnetic activity records exist back until the mid-1800's, and these data provide one of the few means of inferring variations in the conditions in near-Earth space before the advent of the space age. However, there are challenges in using geomagnetic activity records to reconstruct interplanetary conditions. In particular it is necessary to ensure, as best as is possible, the homogeneity and reliability of any geomagnetic indices used. This becomes increasingly difficult further back in history, as both the quality of the data and the number of observing stations decreases. A new geomagnetic activity index, the IDV(1D) index, is presented, which is designed to be as homogeneous in its construction as possible (Lockwood et al. 2013a). This is achieved by only combining data that, by virtue of the locations of the source observatories used, have similar responses to solar wind and IMF variations. IDV(1d) employs many of the principles of the IDV index (Svalgaard and Cliver (2010)), inspired by the u index of Bartels (1932). The index uses interdiurnal variation data from Helsinki for 1845- 1890 and 1893-1896 and from Eskdalemuir from 1911 to the present. The gaps are filled using data from the Potsdam (1891-1892 and 1897-1907) and the nearby Seddin observatories (1908-1910) and intercalibration achieved using the Potsdam-Seddin sequence. The index is compared with independent, early data from European-sector stations, as well as the composite u index and the IDV index. Agreement is found to be extremely good in most cases. IDV(1D) does not suffer from the poor homogeneity of the IDV index, and is more highly correlated with the IMF, consequently it yields a more reliable reconstruction (Lockwood et al 2013b). For completeness, we use 4 different combinations of the IDV(1D), IDV, aa and IHV geomagnetic indices to reconstruct the near-Earth IMF, Vsw, and the OSF from 1845 to 2013. Although each of the different indices is constructed using different data and algorithms the results are very similar and consistent for all 4 combinations of parameters. The OSF variation derived is shown to be very similar indeed to that obtained using the method of Lockwood et al. (1999). This reaffirms one of the key findings from Lockwood et al. (1999), that the OSF approximately doubled over the period 1902-1955. Furthermore, this reconstruction shows that the OSF in the minima of solar cycle 23 and rise phase of solar cycle 24 is the lowest in approximately 100 years, being comparable to levels last experienced in solar cycle 14 (1902-1913).

Lockwood, Mike; Nevanlinna, Heikki; Barnard, Luke; Owens, Mat; Harrison, Giles; Rouillard, Alexis; Scott, Chris; Vokhmyanin, Mikhail; Ponyavin, Dmitri; Sokolov, Sergey

2014-05-01

56

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)

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).

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

2014-04-01

57

Prediction of solar and geomagnetic activity data using neural networks  

NASA Astrophysics Data System (ADS)

Accurate predictions of the future behavior of the solar activity cycle have been sought for many years. Several classes of prediction approach have been proposed, with many variations in each class, and have achieved varying degrees of success. However, considerable room for improvement still remains. Artificial neural network models enjoyed a resurgence in popularity as prediction tools during the late 1980s, as a consequence of the discovery of the back propagation of errors learning algorithm. Initial investigations have been carried out into their potential for predicting solar activity (e.g., Koons and Gorney, 1990; Williams, 1991; Macpherson, 1993a, b). In this paper, we investigate in detail the effect different neural network architectures and learning parameters have on the prediction accuracy of various networks trained on smoothed monthly sunspot and solar 10.7-cm flux data. The importance of obtaining the best generalization capability of a neural network is stressed. Prediction of the geomagnetic aa index is also considered. Finally, in order to validate the usefulness of this technique, the results are compared with a variant of the well-established McNish and Lincoln method (McNish and Lincoln, 1949) and are found to be superior in terms of prediction accuracy.

Macpherson, K. P.; Conway, A. J.; Brown, J. C.

1995-11-01

58

Magnetospheric impulse response for many levels of geomagnetic activity  

Microsoft Academic Search

The temporal relationship between the solar wind and magnetospheric activity has been studied using 34 intervals of high time resolution IMP 8 solar wind data and the corresponding AL auroral activity index. The median value of the AL index for each interval were utilized to rank the intervals according to geomagnetic activity level. The linear prediction filtering technique was then

L. F. Bargatze; D. N. Baker; R. L. McPherron; Hones E. W. Jr

1985-01-01

59

Vertical total electron content and geomagnetic perturbations at mid- and sub-auroral southern latitudes during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Several new space geodesy techniques allow us to analyze the behavior of the vertical total electron content (VTEC) with high spatial and temporal resolution. This study is based on the VTEC computed from global positioning system (GPS) satellite signals that are recorded from observatories located at mid- and sub-auroral southern latitudes. The geomagnetic disturbances are analyzed using the Dst and AL geomagnetic indices and geomagnetic field variations which are recorded from an observatory close to one of the GPS stations and from observatories located at equivalent geomagnetic latitudes but in the Northern Hemisphere. The study is focused on two consecutive geomagnetic storms, which happened on October 4 and 5, 2000, characterized by two flips of the interplanetary magnetic field. During this perturbed period, the substorms are evidenced by the AL index and by the field variations recorded by the geomagnetic observatories. We also analyze a substorm effect that occurred during a geomagnetic storm. Variations in f0F2 are currently considered to study the geomagnetic storm effects on the ionosphere. Our results show that at mid- and subauroral southern latitudes the behavior of the VTEC evidences the “dusk” effect (positive ionospheric storm after noon) in a similar way to f0F2 variations. Similar geomagnetic conditions can be inferred from the Dst index for both geomagnetic storms but a quick rise of the VTEC and the dusk effect is only observed on the first stormy day. The positive ionospheric storm is followed by a negative phase that lasts until October 6. The second geomagnetic storm starts when the negative phase of the first ionospheric storm is still deployed and the ionosphere/plasmasphere system conditions do not allow a new positive ionospheric storm. The AL index and the geomagnetic field variations allow us to recognize the expansion phase of the substorm due to the presence of the electromagnetic wedge that couples the magnetosphere and ionosphere at high latitudes. Fluctuations in the VTEC computed from the GPS observatories are in rough agreement with the influence of the upward and downward field-aligned currents of the wedge.

Meza, Amalia; Andrea van Zele, María; Claudio, Brunini; Rosalía Cabassi, Iris

2005-03-01

60

Hydromagnetic Theory of Geomagnetic Storms  

Microsoft Academic Search

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

A. J. Dessler; E. N. Parker

1959-01-01

61

Some solar cycle phenomena related to the geomagnetic activity from 1868 to 1980. II - High velocity wind streams and cyclical behavior of poloidal field  

Microsoft Academic Search

Geomagnetic activity related to the distribution around the sun of the corotating sources of solar wind is discussed. The physical conditions at the solar wind sources, the cyclical behavior of the poloidal field, and the relationships between the indices aa of geomagnetic activity and the solar wind parameters are reviewed. It is shown that, at the peak of its expansion,

P. A. Simon; J.-P. Legrand

1986-01-01

62

On the high correlation between long-term averages of solar wind speed and geomagnetic activity  

Microsoft Academic Search

Six-month and yearly averages of solar wind speed from 1962 to 1975 are shown to be highly correlated with geomagnetic activity as measured by averages of the AP index. On the same time scale the correlation between the southward component of the interplanetary magnetic field and geomagnetic activity is poor. Previous studies with hourly averages give opposite results. The better

N. U. Crooker; J. Feynman; J. T. Gosling

1977-01-01

63

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

NASA Astrophysics Data System (ADS)

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

Voronin, N.; Avakyan, S.

2009-04-01

64

An Introduction to Geomagnetism  

NSDL National Science Digital Library

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.

Odenwald, Sten

65

Geomagnetic Field During a Reversal  

NASA Technical Reports Server (NTRS)

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.

Heirtzler, J. R.

2003-01-01

66

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

NASA Technical Reports Server (NTRS)

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

Lyatsky, W.; Khazanov, G. V.

2007-01-01

67

Geomagnetic effects on the average surface temperature  

NASA Astrophysics Data System (ADS)

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 are investigated. The temperature data used are the monthly SST maps (generated at RAL and available from the related ESRIN/ESA database) that represent the averaged surface temperature with a spatial resolution of 0.5°x0.5° and cover the entire globe. The interplanetary data and the geomagnetic data are from the USA National Space Science Data Center. The time interval considered is 1995-2000. Specifically, possible associations and/or correlations of the average temperature with the interplanetary magnetic field Bz component and with the Kp index are considered and differentiated taking into account separate geographic and geomagnetic planetary regions.

Ballatore, P.

68

Solar generated quasi-biennial geomagnetic variation  

NASA Technical Reports Server (NTRS)

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

Sugiura, M.; Poros, D. J.

1977-01-01

69

Forecasting Geomagnetic Activity Using Kalman Filters  

NASA Astrophysics Data System (ADS)

The coupling of energy from the solar wind to the magnetosphere leads to the geomagnetic activity in the form of storms and substorms and are characterized by indices such as AL, Dst and Kp. The geomagnetic activity has been predicted near-real time using local linear filter models of the system dynamics wherein the time series of the input solar wind and the output magnetospheric response were used to reconstruct the phase space of the system by a time-delay embedding technique. Recently, the radiation belt dynamics have been studied using a adaptive linear state space model [Rigler et al. 2004]. This was achieved by assuming a linear autoregressive equation for the underlying process and an adaptive identification of the model parameters using a Kalman filter approach. We use such a model for predicting the geomagnetic activity. In the case of substorms, the Bargatze et al [1985] data set yields persistence like behaviour when a time resolution of 2.5 minutes was used to test the model for the prediction of the AL index. Unlike the local linear filters, which are driven by the solar wind input without feedback from the observations, the Kalman filter makes use of the observations as and when available to optimally update the model parameters. The update procedure requires the prediction intervals to be long enough so that the forecasts can be used in practice. The time resolution of the data suitable for such forecasting is studied by taking averages over different durations.

Veeramani, T.; Sharma, A.

2006-05-01

70

On the geomagnetic effects of solar wind interplanetary magnetic structures  

Microsoft Academic Search

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

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

2006-01-01

71

SEMIANNUAL VARIATION OF GEOMAGNETIC ACTIVITY  

Microsoft Academic Search

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

C.T. Russell; R. L. McPherron

1973-01-01

72

Geomagnetic Field During a Reversal.  

National Technical Information Service (NTIS)

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 compone...

J. R. Heirtzler

2003-01-01

73

Geomagnetic activity effect on the global ionosphere during the 2007-2009 deep solar minimum  

NASA Astrophysics Data System (ADS)

this paper the significant effect of weaker geomagnetic activity during the 2007-2009 deep solar minimum on ionospheric variability on the shorter-term time scales of several days was highlighted via investigating the response of daily mean global electron content (GEC, the global area integral of total electron content derived from ground-based GPS measurements) to geomagnetic activity index Ap. Based on a case during the deep solar minimum, the effect of the recurrent weaker geomagnetic disturbances on the ionosphere was evident. Statistical analyses indicate that the effect of weaker geomagnetic activity on GEC variations on shorter-term time scales was significant during 2007-2009 even under relatively quiet geomagnetic activity condition; daily mean GEC was positively correlated with geomagnetic activity. However, GEC variations on shorter-term time scales were poorly correlated with geomagnetic activity during the solar cycle descending phase of 2003-2005 except under strong geomagnetic disturbance condition. Statistically, the effects of solar EUV irradiance, geomagnetic activity, and other factors (e.g., meteorological sources) on GEC variations on shorter-term time scales were basically equivalent during the 2007-2009 solar minimum.

Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing

2014-05-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

75

Deterministic chaos in geomagnetic reversals  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

76

Proterozoic Geomagnetic Field Geometry  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

77

Why AA Works  

Microsoft Academic Search

The therapeutic efficacy of AA, though acknowledged, is little understood. An analysis of the addictive experience is conducted to provide explanatory hypotheses for the success of AA. The addictive experience is characterized by intensity of feelings which cannot be rendered symbolically via language. Out of this mode of experiencing emerges three phenomena: (1) an alleration in the sense of the

Ronald E. Hopson; Bethany Beaird-Spiller

1995-01-01

78

Global empirical model of TEC response to geomagnetic activity  

NASA Astrophysics Data System (ADS)

global total electron content (TEC) model response to geomagnetic activity described by the Kp index is built by using the Center for Orbit Determination of Europe (CODE) TEC data for a full 13 years, January 1999 to December 2011. The model describes the most probable spatial distribution and temporal variability of the geomagnetically forced TEC anomalies assuming that these anomalies at a given modified dip latitude depend mainly on the Kp index, local time (LT), and longitude. The geomagnetic anomalies are expressed by the relative deviation of TEC from its 15 day median and are denoted as rTEC. The rTEC response to the geomagnetic activity is presented by a sum of two responses with different time delay constants and different signs of the cross-correlation function. It has been found that the mean dependence of rTEC on Kp index can be expressed by a cubic function. The LT dependence of rTEC is described by Fourier time series which includes the contribution of four diurnal components with periods 24, 12, 8, and 6 h. The rTEC dependence on longitude is presented by Fourier series which includes the contribution of zonal waves with zonal wave numbers up to 6. In order to demonstrate how the model is able to reproduce the rTEC response to geomagnetic activity, three geomagnetic storms at different seasons and solar activity conditions are presented. The model residuals clearly reveal two types of the model deviation from the data: some underestimation of the largest TEC response to the geomagnetic activity and randomly distributed errors which are the data noise or anomalies generated by other sources. The presented TEC model fits to the CODE TEC input data with small negative bias of -0.204, root mean squares error RMSE = 4.592, and standard deviation error STDE = 4.588. The model offers TEC maps which depend on geographic coordinates (5° × 5° in latitude and longitude) and universal time (UT) at given geomagnetic activity and day of the year. It could be used for both science and possible service (nowcasting and short-term prediction); for the latter, a detailed validation of the model at different geophysical conditions has to be performed in order to clarify the model predicting quality.

Mukhtarov, P.; Andonov, B.; Pancheva, D.

2013-10-01

79

High latitude TEC fluctuations and irregularity oval during geomagnetic storms  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

80

The AAS Workforce Survey  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

81

Geomagnetic Reversals during the Phanerozoic.  

PubMed

An antalysis of worldwide paleomagnetic measurements suggests a periodicity of 350 x 10(6) years in the polarity of the geomagnetic field. During the Mesozoic it is predominantly normal, whereas during the Upper Paleozoic it is predominantly reversed. Although geomagnetic reversals occur at different rates throughout the Phanerozoic, there appeaars to be no clear correlation between biological evolutionary rates and reversal frequency. PMID:17735224

McElhinny, M W

1971-04-01

82

Prepraring to Interpret: AA  

NSDL National Science Digital Library

Students will learn about Alcoholics Anonymous and prepare to interpret for a deaf member at a traditional AA meeting. Interpreting for Alcoholics Anonymous (AA) requires that the interpreter have an understanding of the purpose of the meetings, prepares adequately for frozen text and informal register that will be used, and has respect for the organization and its members. It can be a difficult, but rewarding assignment. Preparing to ...

2007-10-03

83

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

NASA Astrophysics Data System (ADS)

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.

Mendoza, Blanca; Sánchez de La Peña, Salvador

2010-08-01

84

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

SciTech Connect

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

Russell, C.T.; Phillips, J.L. (Univ. of California, Los Angeles (United States)); Fedder, J.A. (Naval Research Lab., Washington, DC (United States)); Allen, J.H.; Morris, L. (National Environmental Satellite, Data, and Information Service, Boulder, CO (United States)); Craig, R.A. (NASA Ames Research Center, Moffett Field, CA (United States))

1987-10-01

85

a Millennium of Geomagnetism  

NASA Astrophysics Data System (ADS)

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

Stern, David P.

2002-11-01

86

Cross-correlation of solar activity with seismicity and geomagnetic disturbances in Vrancea (Romania) source zone  

NASA Astrophysics Data System (ADS)

The paper brings together, in the same frame, the solar activity, the seismicity and the geomagnetic field behavior. Using statistical approaches, we try to find a degree of correlation between the three phenomena. On one part, the solar activity influences the geomagnetic field, giving rise to two types of variations: regular and irregular variations. Daily, seasonal and cyclic 11 years period are regular magnetic field variations and arise from current systems caused by regular and periodic solar radiation changes. These regular variations are composed with the irregular variations due to the irregular activity of the Sun. The magnetic activity indices (Ak, Kp, ap and so on) are designed to describe variation in the geomagnetic field caused by the irregular current systems produced by the multiple interactions between the solar wind, the magnetosphere and by the ionosphere itself. The sunspot number has its reflection in the regular 11 years cycle of the geomagnetic activity and the irregular solar currents (ap index) have the reflection in the irregular variations of the geomagnetic activity and is currently used for the identification of magnetic storms. Both are influencing the geomagnetic activity and records. Tectonic activity, on the other part, sometimes has its own signature on the geomagnetic field. The data used in this paper are obtained from the seismicity of Vrancea source zone (Romplus catalogue), the geomagnetic field recorded by the Romanian geomagnetic observatories (Muntele Rosu and Surlari NIEP and INTERMAGNET) and the global magnetic activity indices obtained from NOAA. The time span of more than 15 years of recordings is covering more than one solar cycle, giving us the opportunity to study the correlation during low and high solar activity periods. A special designed software is used for this study. It allows the visualization and analyzing long time intervals of records as seismicity, geomagnetic field and solar activity parameters.

Moldovan, Iren Adelina; Emilian Toader, Victorin; Otilia Placinta, Anica; Petruta Constantin, Angela; Popescu, Emilia

2013-04-01

87

Statistical Properties of Geomagnetic Activity Indices and Solar Wind Parameters  

NASA Astrophysics Data System (ADS)

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

Kim, Jung-Hee; Chang, Heon-Young

2014-06-01

88

Geomagnetic activity indicators for geomagnetically induced current studies in South Africa  

Microsoft Academic Search

Intense geomagnetic activity is known to give rise to large geomagnetically induced currents (GICs) in power transmission grids. Recordings of geomagnetic activity provide an efficient and economical way for power transmission system operators to assess GIC risks in retrospective studies. This study investigates local geomagnetic indicators (i.e., hourly peak value, hourly range indicator and hourly standard deviation) in order to

Chigomezyo M. Ngwira; Lee-Anne McKinnell; Pierre J. Cilliers

2011-01-01

89

AAS Career Services  

NASA Astrophysics Data System (ADS)

The American Astronomical Society provides substantial programs in the area of Career Services.Motivated by the Society's mission to enhance and share humanity's understanding of the Universe, the AAS provides a central resource for advertising positions, interviewing opportunities at its annual winter meeting and information, workshops and networks to enable astronomers to find employment.The programs of the Society in this area are overseen by an active committee on employment and the AAS Council itself.Additional resources that help characterize the field, its growth and facts about employment such as salaries and type of jobs available are regularly summarized and reported on by the American Institute of Physics.

Marvel, Kevin B.

2012-08-01

90

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

NASA Astrophysics Data System (ADS)

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

Wilson, Robert M.; Hathaway, David H.

2008-02-01

91

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

NASA Technical Reports Server (NTRS)

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

Wilson, Robert M.; Hathaway, David H.

2008-01-01

92

Relationship of Long-Term Solar Activity and Geomagnetic Activity  

NASA Astrophysics Data System (ADS)

Solar acitivity influences geomagnetic activity both in short-term and long-term. The short term effect due to daily solar activity, while long term effect due to about 11-year and 22-year cycles of solar activity. Results of Weighted Wavelet Z-Transform (WWZ) analysis on both of Kp index and sunspot number data yield dominant periods of approx. 11-years and approx. 24-years. But there is an other four-year period of the Kp index. Further studies are required to show whether it is affected by solar activity or not. The strongest effect of solar activity on geomagnetic activity comes from 11-year and 22-year sunspot cycles. This can be seen from correlation coefficient of Kp index and sunspot number as large as 0.8 and 0.7 for average move 11-year and 22-years, respectively. The other result that geomagnetic activity follow solar activity with a time lag of two to three years.

Musafar, K. La Ode Muh; Sinambela, Wilson; Cahyono, Waluyo

2000-04-01

93

Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr - Part 3: Improved representation of solar cycle 11  

NASA Astrophysics Data System (ADS)

Svalgaard (2014) has recently pointed out that the calibration of the Helsinki magnetic observatory's H component variometer was probably in error in published data for the years 1866-1874.5 and that this makes the interdiurnal variation index based on daily means, IDV(1d), (Lockwood et al., 2013a), and the interplanetary magnetic field strength derived from it (Lockwood et al., 2013b), too low around the peak of solar cycle 11. We use data from the modern Nurmijarvi station, relatively close to the site of the original Helsinki Observatory, to confirm a 30% underestimation in this interval and hence our results are fully consistent with the correction derived by Svalgaard. We show that the best method for recalibration uses the Helsinki Ak (H) and aa indices and is accurate to ±10%. This makes it preferable to recalibration using either the sunspot number or the diurnal range of geomagnetic activity which we find to be accurate to ±20%. In the case of Helsinki data during cycle 11, the two recalibration methods produce very similar corrections which are here confirmed using newly digitised data from the nearby St Petersburg observatory and also using declination data from Helsinki. However, we show that the IDV index is, compared to later years, too similar to sunspot number before 1872, revealing independence of the two data series has been lost; either because the geomagnetic data used to compile IDV has been corrected using sunspot numbers, or vice versa, or both. We present corrected data sequences for both the IDV(1d) index and the reconstructed IMF (interplanetary magnetic field). We also analyse the relationship between the derived near-Earth IMF and the sunspot number and point out the relevance of the prior history of solar activity, in addition to the contemporaneous value, to estimating any "floor" value of the near-Earth interplanetary field.

Lockwood, M.; Nevanlinna, H.; Vokhmyanin, M.; Ponyavin, D.; Sokolov, S.; Barnard, L.; Owens, M. J.; Harrison, R. G.; Rouillard, A. P.; Scott, C. J.

2014-04-01

94

VARIATIONS OF GEOMAGNETIC ACTIVITY WITH LUNAR PHASE  

Microsoft Academic Search

An analysis of 31 years of Kdata suggests a variation of geomagnetic dis- turbance with lunar phase. A general increase in geomagnetic activity of about 4% begins after full moon and lasts for seven days. A general decrease in geomagnetic activity of about 4% is found for the seven days preceding full moon. A study of randomized data indicates that

Harold L. Stolov; A. G. W. Cameron

1964-01-01

95

On statistical relationship of solar, geomagnetic and human activities.  

PubMed

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

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

2004-01-01

96

The equatorial ionospheric scintillations during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Geomagnetic storms and disturbances are thought to play an important role for initiation of the ionospheric scintillations. Scintillation manifest itself in rapid fluctuation of the phase and intensity of a radio signal that has passed through the Earth's ionosphere, typically on a satellite-to-ground propagation channel. Mechanisms of ionospheric scintillation are better understood than its morphology and serious efforts were made to find the empirical relationships in terms of different geomagnetic indices for their forcasting. Such relationships can help to avoid blackouts and distortions in VLF communication due to ionospheric irregularities. We used the different geomagnetic indices, the ionospheric parameters, and the Bz-component of the interplanetary magnetic field (IMF) to study scintillation activity at the dip latitudes. The relationship between the equatorial ionospheric scintillations and the IMF Bz, Dst, Kp, AU, and AL indices is demonstrated. It is shown that in parallel with much used of Dst- index other indices are also suitable for study of scintillation activity. For example, Kp as planetary index carries information about auroral electrojets also and we can see that no scintillation activity when Kp decreases during positive IMF Bz. This means that the auroral electrojets depicted by the AU, and AL-indices and connected with the field-aligned currents (FAC) are decreased and moved to pole ward. The positive IMF Bz is likely to be the factor that inhibits the equator ward penetration of the high latitude electric field. The negative IMF Bz enhances the auroral electric fields and they can penetrate to the equatorial ionosphere. The examples presented in our study allow us to assume that the southward IMF Bz by the Region 1 FAC can form an additional eastward current system at the equatorial ionosphere. Under these conditions the virtual height h'F rises to high altitudes and when it drops the scintillations can be generated. It may be safely suggested that source of this phenomenon is the solar wind electric field responcible for the auroral and equatorial ionosphere coupling. Other processes such as tides, earthquakes etc. can change the ionospheric height also and may play a role in the generation of the ionospheric scintillations. From a practical point of view, the relationships between the solar wind and the ionospheric parameters can be used for the prediction of scintillations, if one takes into account the time delay between the IMF Bz and the equatorial ionospheric data.

Biktash, L.

97

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

PubMed

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

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

2001-01-01

98

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

NASA Astrophysics Data System (ADS)

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

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

99

On Geomagnetism and Paleomagnetism  

NASA Technical Reports Server (NTRS)

A statistical description of Earth's broad scale, core-source magnetic field has been developed and tested. The description features an expected, or mean, spatial magnetic power spectrum that is neither "flat" nor "while" at any depth, but is akin to spectra advanced by Stevenson and McLeod. This multipole spectrum describes the magnetic energy range; it is not steep enough for Gubbins' magnetic dissipation range. Natural variations of core multipole powers about their mean values are to be expected over geologic time and are described via trial probability distribution functions that neither require nor prohibit magnetic isotropy. The description is thus applicable to core-source dipole and low degree non-dipole fields despite axial dipole anisotropy. The description is combined with main field models of modem satellite and surface geomagnetic measurements to make testable predictions of: (1) the radius of Earth's core, (2) mean paleomagnetic field intensity, and (3) the mean rates and durations of both dipole power excursions and durable axial dipole reversals. The predicted core radius is 0.7% above the 3480 km seismologic value. The predicted root mean square paleointensity (35.6 mu T) and mean Virtual Axial Dipole Moment (about 6.2 lx 1022 Am(exp 2)) are within the range of various mean paleointensity estimates. The predicted mean rate of dipole power excursions, as defined by an absolute dipole moment <20% of the 1980 value, is 9.04/Myr and 14% less than obtained by analysis of a 4 Myr paleointensity record. The predicted mean rate of durable axial dipole reversals (2.26/Myr) is 2.3% more than established by the polarity time-scale for the past 84 Myr. The predicted mean duration of axial dipole reversals (5533 yr) is indistinguishable from an observational value. The accuracy of these predictions demonstrates the power and utility of the description, which is thought to merit further development and testing. It is suggested that strong stable stratification of Earth's uppermost outer core leads to a geologically long interval of no dipole reversals and a very nearly axisymmetric field outside the core. Statistical descriptions of other planetary magnetic fields are outlined.

Voorhies, Coerte V.

1998-01-01

100

A study of solar and interplanetary parameters of CMEs causing major geomagnetic storms during SC 23  

NASA Astrophysics Data System (ADS)

In this paper we analyse 25 Earth-directed and strongly geoeffective interplanetary coronal mass ejections (ICMEs) which occurred during solar cycle 23, using data provided by instruments on SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and geomagnetic stations. We also examine the in situ parameters, the energy transfer into magnetosphere, and the geomagnetic indexes. We compare observed travel times with those calculated by observed speeds projected into the plane of the sky and de-projected by a simple model. The best fit was found with the projected speeds. No correlation was found between the importance of a flare and the geomagnetic Dst (disturbance storm time) index. By comparing the in situ parameters with the Dst index we find a strong connection between some of these parameters (such as Bz, Bs · V and the energy transfer into the magnetosphere) with the strength of the geomagnetic storm. No correlation was found with proton density and plasma temperature. A superposed epoch analysis revealed a strong dependence of the Dst index on the southward component of interplanetary magnetic field, Bz, and to the Akasofu coupling function, which evaluates the energy transfer between the ICME and the magnetosphere. The analysis also showed that the geomagnetic field at higher latitudes is disturbed before the field around the Earth's equator.

Oprea, C.; Mierla, M.; Be?liu-Ionescu, D.; Stere, O.; Mari? Muntean, G.

2013-08-01

101

What is a geomagnetic storm?  

Microsoft Academic Search

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

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

1994-01-01

102

Mechanism for geomagnetic polarity reversals  

Microsoft Academic Search

It is shown here that the present fall in the dipole moment of the geomagnetic field is directly related to the intensification and southward comovement of patches of flux occurring beneath southern Africa and South America whose signs are opposite to that expected for a dipole field. It is suggested that the fall occasionally leads to polarity reversal. The almost

David Gubbins

1987-01-01

103

SPORADIC E AND GEOMAGNETIC ACTIVITY  

Microsoft Academic Search

In review, Whitehead [1970] recently pointed out that there is evidence of changes in midlatitude sporadic E during periods of increased geomagnetic activity. The nature of these changes appears to depend on latitude with a reversal in the effect about the Sq current focus. This note suggests a sporadic-E mechanism that is consistent with this reversal and yet not in

R. L. Closs

1971-01-01

104

Weather reacting to geomagnetic storms  

Microsoft Academic Search

In the first 15 years of the Space Age satellite position measurements derived from visual and photographic observations helped to determine the decay rate of satellites, by means of which the first models of the upper-atmosphere have been calculated. Our group concentrated on the study of the geomagnetic effect and collected several ten thousand observations from Europe and from Asia

E. Illés-Almár

2004-01-01

105

On the decadal to multi-decadal evolution and correlations of geomagnetic indices in relation to variations in solar activity  

NASA Astrophysics Data System (ADS)

Magnetic indices measure magnetic activity occurring over periods of time from minutes to hours, as recorded at geomagnetic observatories. They address in principle specific features of geomagnetic activity, with an origin in Earth's ionosphere or magnetosphere. In the present study, we use daily indices, which can be arranged in two classes: roughly speaking, some reflect properties of magnetic field disturbances integrated over one day (1st family or A-type), whereas others reflect the maximal values of these disturbances (ranges) for that day (2nd family or B type). We analyze correlations between the evolutions of classical (daily) indices aa, Ap (B-type) and Dst and recently introduced absolute 3-day slopes ? (A-type) at decadal time scales. Pairs of indices (aa and Ap on one hand, Dst and ? on the other hand) display decade-long periods of high correlation interrupted by shorter periods of reduced correlation and even anti-correlation. Decadal variations of mutual correlation between A and B-type indices are governed by solar cycle evolution. Loss of correlation between geomagnetic indices coincides with loss of correlation between geomagnetic indices and solar activity. In the past half-century, such sharp losses have occurred in the declining phases and minima of solar cycles 20 and 23. Differences between these two solar cycles in terms of correlation properties of geomagnetic indices will be briefly discussed.

Le Mouel, J.; Blanter, E.; Shnirman, M.; Courtillot, V.

2011-12-01

106

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

NASA Astrophysics Data System (ADS)

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

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

107

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)

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.

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

2002-05-01

108

Simulated geomagnetic reversals and preferred virtual geomagnetic pole paths  

Microsoft Academic Search

The question of whether virtual geomagnetic poles (VGPs) recorded during reversals and excursions show a longitudinal preference is a controversial one amongst palaeomagnetists. One possible mechanism for such VGP clustering is the heterogeneity of heat flux at the core-mantle boundary (CMB). We use 3-D convection-driven numerical dynamo models with imposed non-uniform CMB heat flow that show stochastic reversals of the

C. Kutzner; U. R. Christensen

2004-01-01

109

Worldwide Geomagnetic Data Collection and Management  

NASA Astrophysics Data System (ADS)

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

Mandea, Mioara; Papitashvili, Vladimir

2009-11-01

110

Ice ages and geomagnetic reversals  

NASA Technical Reports Server (NTRS)

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.

Wu, Patrick

1992-01-01

111

Geomagnetic activity at sector boundaries.  

NASA Technical Reports Server (NTRS)

The relation between the rise in geomagnetic activity at sector boundaries and the south-pointing component of the interplanetary field is investigated. It is shown that, in 1968, an increase in the average southward component occurred when the sector boundary was crossed. This increase can account for the initial increase in magnetic activity. However, the southward component rapidly fell to its preboundary levels, while geomagnetic activity remained elevated for at least a day. This observation suggests that either the magnetosphere took of the order of a day to relax or energy continued to be fed into the magnetosphere at an enhanced rate during the postboundary period. A possible cause of the increase in southward fields at sector boundaries is discussed.

Hirshberg, J.; Colburn, D. S.

1973-01-01

112

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

NASA Astrophysics Data System (ADS)

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

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

113

Geomagnetic Field Frequently Asked Questions  

NSDL National Science Digital Library

At this site the question and answer format is used to provide information about the Earth's magnetic field. Frequently asked questions are linked to detailed answers. Along with standard questions about the magnetic poles and how a compass works, there are sections about geomagnetic models, Space Weather Scales and magnetic field reversals. Links lead to a site to download the latest model as well as sites for more detailed information.

114

A study of geomagnetic storms  

NASA Technical Reports Server (NTRS)

Twenty-one geomagnetic storm events during 1966 and 1970 were studied by using simultaneous interplanetary magnetic field and plasma parameters. Explorer 33 and 35 field and plasma data were analyzed on large-scale (hourly) and small-scale (3 min.) during the time interval coincident with initial phase of the geomagnetic storms. The solar-ecliptic Bz component turns southward at the end of the initial phase, thus triggering the main phase decrease in Dst geomagnetic field. When the Bz is already negative, its value becomes further negative. The By component also shows large fluctuations along with Bz. When there are no clear changes in the Bz component, the By shows abrupt changes at the main phase onet. On the small-scale behavior of the magnetic field and electric field (E=-VxB) studied in details for the three events, it is found that the field fluctuations in By, Bz and Ey and Ez are present in the initial phase. These fluctuations become larger just before the main phase of the storm begins. In the largescale behavior field remains quiet because the small scale variations are averaged out.

Patel, V. L.

1975-01-01

115

Geomagnetic Excursions in Alaskan Loess  

NASA Astrophysics Data System (ADS)

Palaeomagnetic and mineral magnetic investigations indicate that Alaskan loess is an excellent geomagnetic recorder. Most samples possess a strong, stable primary remanence, with MAD values typically being about 2 degrees. Hysteresis loops and IRM acquisition curves suggest that the NRM is carried by magnetite. Our earlier studies indicate that the Bruhnes-Matuyama boundary and the Kamikatsura excursion are convincingly recorded at Gold Hill (near Fairbanks, Alaska). Higher up in the section, two directional perturbations occur that may correlate to the Laschamp and Skalamaelifell excursions, and a third that is chronologically poorly constrained. At Halfway House (35 km west of Fairbanks), a directional perturbation occurs 4-5 m above the Old Crow Tephra (a regional chronostratigraphic marker dated at 124+/-10ka). Corresponding VGPs fall in North Africa, close to published results from lavas in Iceland. We suggest that this feature represents the Skalamaelifell excursion (recently dated at 94.1+/-7.8 ka). This is supported by the occurrence at Halfway House of a newly-dated, 106+/-10ka, tephra just below the geomagnetic perturbation. These promising preliminary results indicate that more detailed, closely-spaced, sampling might help elucidate the field behaviour at times of geomagnetic instability during the Brunhes chron.

Evans, M. E.; Jensen, B. J.; Kravchinsky, V. A.; Froese, D. G.

2012-04-01

116

Restoration project of geomagnetic survey in Latvia  

NASA Astrophysics Data System (ADS)

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.

Burlakovs, J.; Lembere, I.

2003-04-01

117

The Geomagnetic Field During a Reversal  

NASA Technical Reports Server (NTRS)

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.

Heirtzler, James R.

2003-01-01

118

Annual fractions of high speed streams from principal component analysis of local geomagnetic activity  

NASA Astrophysics Data System (ADS)

We study the spatial distribution of geomagnetic activity in 1966-2009 with local geomagnetic activity indices at 27 magnetic observatories. Using the principal component analysis method we find that more than 97% of the variance in annually averaged geomagnetic activity can be described by the two first principal components. The first component describes the evolution of the global geomagnetic activity, and has excellent correlation with, e.g., the Kp/Ap index. The second component describes the leading pattern by which the spatial distribution of geomagnetic activity deviates from the global average. We show that the second component is highly correlated with the relative (annual) fraction of high-speed streams (HSS) in solar wind. The spatial distribution of the second mode has a high maximum at auroral latitudes, a local minimum at subauroral latitudes and a low maximum at mid-latitudes. We show that this distribution is related to the difference in the average location and intensity between CME and HSS-related substorms. These results demonstrate that the local indices of geomagnetic activity over a spatially extended network can provide useful, quantitative information about the solar wind that is lost when using only global indices.

Holappa, Lauri; Mursula, Kalevi; Asikainen, Timo; Richardson, Ian G.

2014-05-01

119

Geomagnetic activity during the rising phase of solar cycle 24  

NASA Astrophysics Data System (ADS)

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

Richardson, Ian G.

2013-03-01

120

Sparkling Geomagnetic Field: Involving Schools in Geomagnetic Research  

NASA Astrophysics Data System (ADS)

Solar activity will be reaching a maximum in 2013/2014 as the sun reaches the end of its cycle, bringing with it an opportunity to study in greater detail the effect of solar wind or "space weather" on our planet's magnetic field. Heightened solar activity leads to a larger amount of clouds of energetic particles bombarding the Earth. Although the Earth's magnetic field shields us from most of these particles, the field becomes distorted and compacted by the solar wind, which leads to magnetic storms that we detect from the surface. These storms cause aurorae at higher latitudes and can lead to widespread disruption of communication and navigation equipment all over the Earth when sufficiently strong. This project, "Sparkling Geomagnetic Field," is a part of Austria's Sparkling Science programme, which aims to involve schools in active scientific research to encourage interest in science from a young age. Researchers from the Central Institute for Meteorology and Geodynamics (ZAMG) in Vienna have worked hand-in-hand with three schools across Austria to set up regional geomagnetic stations consisting of state-of-the-art scalar and vector magnetometers to monitor the effects of the solar wind on the geomagnetic field. The students have been an active part of the research team from the beginning, first searching for a suitable location to set up the stations as well as later overseeing the continued running of the equipment and analysing the data output. Through this project the students will gain experience in contemporary scientific methods: data processing and analysis, field work, as well as equipment setup and upkeep. A total of three stations have been established with schools in Innsbruck, Tamsweg and Graz at roughly equal distances across Austria to run alongside the already active station in the Conrad Observatory near Vienna. Data acquisition runs through a data logger and software developed to deliver data in near realtime. This network allows for evaluation of both the spatial and temporal development of magnetic storms across the longitudes. Currently the stations are running in a test phase as the last system wrinkles are ironed out. The geomagnetic network will be running and delivering continuous data by spring 2014.

Bailey, Rachel; Leonhardt, Roman; Leichter, Barbara

2014-05-01

121

Statistical properties of geomagnetic measurements as a potential forecast tool for strong perturbations  

Microsoft Academic Search

We have localized the main magnetic disturbances for the period 1998-2002 in the Dst index from the World Data Centre for Geomagnetism, Kyoto, Japan. Two kinds of time intervals previous to them were studied through a methodology recently introduced in the literature. Records used for this study are from the low-latitude Vassouras Magnetic Observatory, Brazil. A correlation between statistical properties

Andrés R. R. Papa; Lilian P. Sosman

2008-01-01

122

Statistical properties of geomagnetic measurements as a potential forecast tool for strong perturbations  

Microsoft Academic Search

We have localized the main magnetic disturbances for the period 1998–2002 in the Dst index from the World Data Centre for Geomagnetism, Kyoto, Japan. Two kinds of time intervals previous to them were studied through a methodology recently introduced in the literature. Records used for this study are from the low-latitude Vassouras Magnetic Observatory, Brazil. A correlation between statistical properties

Andrés R. R. Papa; Lilian P. Sosman

2008-01-01

123

On the limitations of geomagnetic measures of interplanetary magnetic polarity  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

124

Predicting ground electric field due to geomagnetic disturbances  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

125

Geomagnetic activity effects on plasma sheet energy conversion  

NASA Astrophysics Data System (ADS)

In this article we use three years (2001, 2002, and 2004) of Cluster plasma sheet data to investigate what happens to localized energy conversion regions (ECRs) in the plasma sheet during times of high magnetospheric activity. By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have studied the influence on Concentrated Load Regions (CLRs) and Concentrated Generator Regions (CGRs) from variations in the geomagnetic disturbance level as expressed by the Kp, the AE, and the Dst indices. We find that the ECR occurrence frequency increases during higher magnetospheric activities, and that the ECRs become stronger. This is true both for CLRs and for CGRs, and the localized energy conversion therefore concerns energy conversion in both directions between the particles and the fields in the plasma sheet. A higher geomagnetic activity hence increases the general level of energy conversion in the plasma sheet. Moreover, we have shown that CLRs live longer during magnetically disturbed times, hence converting more electromagnetic energy. The CGR lifetime, on the other hand, seems to be unaffected by the geomagnetic activity level. The evidence for increased energy conversion during geomagnetically disturbed times is most clear for Kp and for AE, but there are also some indications that energy conversion increases during large negative Dst. This is consistent with the plasma sheet magnetically mapping to the auroral zone, and therefore being more tightly coupled to auroral activities and variations in the AE and Kp indices, than to variations in the ring current region as described by the Dst index.

Hamrin, M.; Norqvist, P.; Marghitu, O.; Buchert, S.; Klecker, B.; Kistler, L. M.; Dandouras, I.

2010-10-01

126

Solar dynamo and geomagnetic activity  

NASA Astrophysics Data System (ADS)

The correlation between geomagnetic activity and the sunspot number in the 11-year solar cycle exhibits long-term variations due to the varying time lag between the sunspot-related and non-sunspot related geomagnetic activity, and the varying relative amplitude of the respective geomagnetic activity peaks. As the sunspot-related and non-sunspot related geomagnetic activity peaks are caused by different solar agents, related to the solar toroidal and poloidal fields, respectively, we use their variations to derive the parameters of the solar dynamo transforming the poloidal field into toroidal field and back. We find that in the last 12 cycles the solar surface meridional circulation varied between 5 and 20 m/s (averaged over latitude and over the sunspot cycle), the deep circulation varied between 2.5 and 5.5 m/s, and the diffusivity in the whole of the convection zone was ˜108 m2/s. In the last 12 cycles solar dynamo has been operating in moderately diffusion dominated regime in the bulk of the convection zone. This means that a part of the poloidal field generated at the surface is advected by the meridional circulation all the way to the poles, down to the tachocline and equatorward to sunspot latitudes, while another part is diffused directly to the tachocline at midlatitudes, “short-circuiting” the meridional circulation. The sunspot maximum is the superposition of the two surges of toroidal field generated by these two parts of the poloidal field, which is the explanation of the double peaks and the Gnevyshev gap in sunspot maximum. Near the tachocline, dynamo has been operating in diffusion dominated regime in which diffusion is more important than advection, so with increasing speed of the deep circulation the time for diffusive decay of the poloidal field decreases, and more toroidal field is generated leading to a higher sunspot maximum. During the Maunder minimum the dynamo was operating in advection dominated regime near the tachocline, with the transition from diffusion dominated to advection dominated regime caused by a sharp drop in the surface meridional circulation which is in general the most important factor modulating the amplitude of the sunspot cycle.

Georgieva, Katya; Kirov, Boian

2011-02-01

127

Electric utility industry experience with geomagnetic disturbances  

SciTech Connect

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

Barnes, P.R.; Rizy, D.T.; McConnell, B.W. (Oak Ridge National Lab., TN (United States)); Taylor, E.R. Jr. (ABB Power Systems, Inc., Pittsburgh, PA (United States)); Tesche, F.M.

1991-09-01

128

Electric utility industry experience with geomagnetic disturbances  

SciTech Connect

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

Barnes, P.R.; Rizy, D.T.; McConnell, B.W. [Oak Ridge National Lab., TN (United States); Taylor, E.R. Jr. [ABB Power Systems, Inc., Pittsburgh, PA (United States); Tesche, F.M.

1991-09-01

129

Power lines and the geomagnetic field  

Microsoft Academic Search

The metric of prime interest in power line epidemiological studies has been AC magnetic intensity. To consider also possible geomagnetic involvement, the orientation of a long straight power line is examined relative to a uniform geomagnetic field (GMF) with dip angle α. An expression is derived for the component of the total GMF that is parallel, at an elevation β,

Abraham R. Liboff; Bruce R. McLeod

1995-01-01

130

The distinction between geomagnetic excursions and reversals  

Microsoft Academic Search

Two recent studies of the geomagnetic field in the last 1 Myr have found 14 excursions, large changes in direction lasting 5-10 kyr each, six of which are established as global phenomena by correlation between different sites. The older picture of the geomagnetic field enjoying long periods of stable polarity may not therefore be correct; instead, the field appears to

David Gubbins

1999-01-01

131

Transitional field configurations and geomagnetic reversal  

Microsoft Academic Search

Two axisymmetric, or zonal, nondipole field configurations, one predominantly octupolar and the other predominantly quadrupolar, are described. The two configurations have been considered as possible intermediate states of the geomagnetic field during reversals. It is shown that the two configurations would effect the transitional virtual geomagnetic pole behavior in different ways. If reversal records from both northern latitudes and southern

K. A. Hoffman; M. Fuller

1978-01-01

132

Revision of International Geomagnetic Reference Field released  

NASA Astrophysics Data System (ADS)

A 1995 revision of the International Geomagnetic Reference Field (IGRF) was adopted by the International Association of Geomagnetism and Aeronomy (IAGA) during the XXI General Assembly of the International Union of Geodesy and Geophysics held in Boulder, Colo., in July 1995.

IAGA Division V, Working Group 8,

133

Localized analysis of polar geomagnetic jerks  

NASA Astrophysics Data System (ADS)

A new method is introduced to find the relatively sudden temporal changes or jerks of the geomagnetic field over the polar regions. Geomagnetic jerk events during the 20th century have mostly been identified from direct measurements at mid-latitude geomagnetic observatories. Recently, however, global magnetic spherical harmonic models like CM4 and CHAOS have been found effective in identifying the Antarctic events of 1969, 1978, 1985, 1991 and 2003 that were followed by jerks in the Arctic region with time delays of one to three years. The present study extends these events into earlier decades from 1900 to 1985 using the global harmonic model gufm1 with localized spherical coefficients or Slepian functions for the polar regions. Power spectral minima for the localized coefficients correlate with and thus help identify the abrupt changes in geomagnetic secular acceleration models. The time delay between the Antarctic and Arctic geomagnetic jerks was also confirmed.

Kim, Hyung Rae; von Frese, Ralph R. B.

2013-02-01

134

North-south asymmetry in emission intensities of geomagnetic conjugate auroras  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

135

Spectral Analysis of Geomagnetic Activity Indices and Solar Wind Parameters  

NASA Astrophysics Data System (ADS)

Solar variability is widely known to affect the interplanetary space and in turn the Earth¡¯s electromagnetical environment on the basis of common periodicities in the solar and geomagnetic activity indices. The goal of this study is twofold. Firstly, we attempt to associate modes by comparing a temporal behavior of the power of geomagnetic activity parameters since it is barely sufficient searching for common peaks with a similar periodicity in order to causally correlate geomagnetic activity parameters. As a result of the wavelet transform analysis we are able to obtain information on the temporal behavior of the power in the velocity of the solar wind, the number density of protons in the solar wind, the AE index, the Dst index, the interplanetary magnetic field, B and its three components of the GSM coordinate system, BX, BY, BZ. Secondly, we also attempt to search for any signatures of influence on the space environment near the Earth by inner planets orbiting around the Sun. Our main findings are as follows: (1) Parameters we have investigated show periodicities of ~ 27 days, ~ 13.5 days, ~ 9 days. (2) The peaks in the power spectrum of BZ appear to be split due to an unknown agent. (3) For some modes powers are not present all the time and intervals showing high powers do not always coincide. (4) Noticeable peaks do not emerge at those frequencies corresponding to the synodic and/or sidereal periods of Mercury and Venus, which leads us to conclude that the Earth¡¯s space environment is not subject to the shadow of the inner planets as suggested earlier.

Kim, Jung-Hee; Chang, Heon-Young

2014-06-01

136

Ionospheric effects caused by the series of geomagnetic storms of September 9-14, 2005  

NASA Astrophysics Data System (ADS)

This study presents the ionospheric effects caused by the series of geomagnetic storms of September 9-14, 2005. The behavior of different ionospheric parameters over the Yakutsk, Irkutsk, Millstone Hill and Arecibo stations during the considered period have been numerically calculated, using a global self-consistent model of the thermosphere, ionosphere, and protonosphere (GSM TIP) developed at WD IZMI-RAN. The model calculations of disturbances of the ionospheric parameters during storms qualitatively agree with the experimental data at these midlatitude stations. We suggest that the causes of the quantitative differences between the model calculations and the observational data were the use of the 3-hour Kp index of geomagnetic activity and the dipole approximation of geomagnetic field in GSM TIP, with additional contributions from the effects of solar flares which are not considered in GSM TIP.

Klimenko, M. V.; Klimenko, V. V.; Ratovsky, K. G.; Goncharenko, L. P.

2011-06-01

137

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

NASA Astrophysics Data System (ADS)

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.

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

2012-05-01

138

An empirical model of ground-level geomagnetic perturbations  

NASA Astrophysics Data System (ADS)

A new empirical model for predicting ground-level geomagnetic perturbations has been developed. This model is based on global measurements of the magnetic field at multiple stations in the Northern Hemisphere collected over an 8 year period, along with the simultaneous measurements of the interplanetary magnetic field (IMF). Variations in ionospheric conductivity are implicitly contained in the measurements used in the model's construction, including the solar F10.7 index. Provided with the IMF, solar wind velocity, dipole tilt angle (for season), and F10.7 index, this model computes all three vector components of the magnetic perturbations at specified locations. The model results are consistent with the corresponding maps of the ionospheric electric potential. Interestingly, maps of the vertical component have patterns that resemble maps of the overhead, ionospheric field-aligned currents. Comparisons of model calculations with measurements at different locations show very good results, particularly at low frequencies. There are random variations at higher frequencies that are not reproduced well with the model, but they tend to occur in proportion to the predicted levels. This model could be useful for providing regional forecasts of geomagnetic activity with an approximately 1 h lead time.

Weimer, D. R.

2013-03-01

139

Kinematic reversal schemes for the geomagnetic dipole.  

NASA Technical Reports Server (NTRS)

Fluctuations in the distribution of cyclonic convective cells, in the earth's core, can reverse the sign of the geomagnetic field. Two kinematic reversal schemes are discussed. In the first scheme, a field maintained by cyclones concentrated at low latitude is reversed by a burst of cyclones at high latitude. Conversely, in the second scheme, a field maintained predominantly by cyclones in high latitudes is reversed by a fluctuation consisting of a burst of cyclonic convection at low latitude. The precise fluid motions which produce the geomagnetic field are not known. However, it appears that, whatever the details are, a fluctuation in the distribution of cyclonic cells over latitude can cause a geomagnetic reversal.

Levy, E. H.

1972-01-01

140

Geomagnetic activity: Dependence on solar wind parameters  

NASA Technical Reports Server (NTRS)

Current ideas about the interaction between the solar wind and the earth's magnetosphere are reviewed. The solar wind dynamic pressure as well as the influx of interplanetary magnetic field lines are both important for the generation of geomagnetic activity. The influence of the geometry of the situation as well as the variability of the interplanetary magnetic field are both found to be important factors. Semi-annual and universal time variations are discussed as well as the 22-year cycle in geomagnetic activity. All three are found to be explainable by the varying geometry of the interaction. Long term changes in geomagnetic activity are examined.

Svalgaard, L.

1977-01-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2001-08-01

142

Minimax confidence intervals in geomagnetism  

NASA Technical Reports Server (NTRS)

The present paper uses theory of Donoho (1989) to find lower bounds on the lengths of optimally short fixed-length confidence intervals (minimax confidence intervals) for Gauss coefficients of the field of degree 1-12 using the heat flow constraint. The bounds on optimal minimax intervals are about 40 percent shorter than Backus' intervals: no procedure for producing fixed-length confidence intervals, linear or nonlinear, can give intervals shorter than about 60 percent the length of Backus' in this problem. While both methods rigorously account for the fact that core field models are infinite-dimensional, the application of the techniques to the geomagnetic problem involves approximations and counterfactual assumptions about the data errors, and so these results are likely to be extremely optimistic estimates of the actual uncertainty in Gauss coefficients.

Stark, Philip B.

1992-01-01

143

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

NASA Astrophysics Data System (ADS)

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.

Klimenko, Maxim; Klimenko, Vladimir

144

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.

145

How the geomagnetic field vector reverses polarity  

USGS Publications Warehouse

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.

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

1985-01-01

146

Nuclear Georeactor Generation of Earth's Geomagnetic Field  

Microsoft Academic Search

The purpose of this communication is to suggest that the mechanism for generating the geomagnetic field and the energy source for powering it are one and the same, a nuclear georeactor at the center of the Earth. Toward this end, I: i) Present evidence that the nuclear georeactor fission-product sub-shell is fluid; ii)Suggest that the geomagnetic field is generated within

J. Marvin Herndon

2007-01-01

147

Nuclear Georeactor Generation of Earth's Geomagnetic Field  

Microsoft Academic Search

The purpose of this communication is to suggest that the mechanism for\\u000agenerating the geomagnetic field and the energy source for powering it are one\\u000aand the same, a nuclear georeactor at the center of the Earth. Toward this end,\\u000aI: i) Present evidence that the nuclear georeactor fission-product sub-shell is\\u000afluid; ii)Suggest that the geomagnetic field is generated within

J. Marvin Herndon

2007-01-01

148

Analysis of the geomagnetic induction tensor  

Microsoft Academic Search

The geomagnetic induction tensor is a means of summarizing the response of the earth at a given observing site to a geomagnetic variation ource sfield. In this paper the characteristics of the tensor elements are examined, both generally and for the special cases of one-dimensional and two-dimensional geologic structure. The first-order model is taken of uniform source fields originating external

F. E. M. Lilley

1974-01-01

149

Ergodicity of the recent geomagnetic field  

NASA Astrophysics Data System (ADS)

The geomagnetic field is a fundamental property of our planet: its study would allow us to understand those processes of Earth's interior, which act in its outer core and produce the main field. Knowledge of whether the field is ergodic, i.e. whether time averages correspond to phase space averages, is an important question since, if this were true, it would point out a strong spatio-temporal coupling amongst the components of the dynamical system behind the present geomagnetic field generation. Another consequence would be that many computations, usually undertaken with many difficulties in the phase space, can be made in the conventional time domain. We analyse the temporal behaviour of the deviation between predictive and definitive geomagnetic global models for successive intervals from 1965 to 2010, finding a similar exponential growth with time. Also going back in time (at around 1600 and 1900 by using the GUFM1 model) confirms the same findings. This result corroborates previous chaotic analyses made in a reconstructed phase space from geomagnetic observatory time series, confirming the chaotic character of the recent geomagnetic field with no reliable prediction after around 6 years from definitive values, and disclosing the potentiality of estimating important entropic quantities of the field by time averages. Although more tests will be necessary, some of our analyses confirm the efforts to improve the representation of the geomagnetic field with more detailed secular variation and acceleration.

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

2011-06-01

150

Geomagnetic disturbance effects on power systems  

SciTech Connect

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.

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

151

Dependence of Geomagnetic Storms on Their Associated Halo CME Parameters  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

152

The Dynamics of Geomagnetic Storms and Substorms with the WINDMI model  

NASA Astrophysics Data System (ADS)

We discuss a low order physics model of the nightside magnetosphere called WINDMI. The model uses solar wind and IMF measurements from the ACE spacecraft as input into a system of 8 nonlinear ordinary differential equations. The state variables of the differential equations represent the energy stored in the geomagnetic tail, central plasma sheet, ring current and field aligned currents. The output from the model is the geomagnetic westward auroral electrojet (AL) index, and the Dst index. We will show how the model has been used to analyze the dynamics of geomagnetic storms and substorms. We present results from the model that show the geomagnetic tail current contribution to the Dst index, during the recovery period after a large geomagnetic storm. Next, three classes of magnetospheric substorms are studied with the model, isolated substorms, storm time substorms, and periodic substorms. We analyze the model predictions to obtain the statistical average of the energy content in the earth's ring current, central plasma sheet and geotail lobes. We use a database of events during the last and current solar maximum period to constrain the WINDMI model parameters in order to identify the geotail lobe energy, plasma sheet electric field and plasma sheet pressure that results in the triggering of the different types of substorms. The relative timing between the electric field, magnetic field and plasma sheet pressure during the triggering or the onset of substorm are presented. We compare the intermediate state variables of the WINDMI model against satellite measurements. We find that for certain fixed states, the response of the magnetosphere depends on the level of solar wind forcing. We also present the differences in magnetospheric plasma conditions between periodic substorms and isolated substorm events, during southward IMF conditions.

Spencer, E. A.; Patra, S.; Horton, W.

2012-12-01

153

Relationship Between Human Physiological Parameters And Geomagnetic Variations Of Solar Origin  

NASA Astrophysics Data System (ADS)

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

Dimitrova, S.

154

Measurement of geomagnetic cutoff rigidities and particle fluxes below geomagnetic cutoff near Palestine, Texas  

Microsoft Academic Search

A high-statistics magnetic spectrometer measurement of the geomagnetic ; cutoff rigidity and related effects at Palestine, Texas is reported. The ; effective cutoffs observed are in agreement with computer-calculated cutoffs. ; Measured spectra of albedo and atmospheric secondary particles that come below ; geomagnetic cutoff are also reported. (auth);

C. R. Pennypacker; G. F. Smoot; A. Buffington; R. A. Muller; L. H. Smith

1973-01-01

155

Measurement of geomagnetic cutoff rigidities and particle fluxes below geomagnetic cutoff near Palestine, Texas.  

NASA Technical Reports Server (NTRS)

We report a high-statistics magnetic spectrometer measurement of the geomagnetic cutoff rigidity and related effects at Palestine, Texas. The effective cutoffs we observe are in agreement with computer-calculated cutoffs. We also report measured spectra of albedo and atmospheric secondary particles that come below geomagnetic cutoff.

Pennypacker, C. R.; Smoot, G. F.; Buffington, A.; Muller, R. A.; Smith, L. H.

1973-01-01

156

Geomagnetic Field Modeling with DMSP  

NASA Astrophysics Data System (ADS)

The Defense Meteorological Satellite Program (DMSP) launches and maintains a network of satellites to monitor the meteorological, oceanographic, and solar-terrestrial physics environments. In the past decade, geomagnetic field modelers have focused much attention on magnetic measurements from missions such as CHAMP, Oersted and SAC-C. With the completion of the CHAMP mission in 2010, there have been limited satellite-based vector and scalar magnetic field measurements available for main field modeling. In this study, we investigate the feasibility of using the Special Sensor Magnetometer (SSM) instrument onboard DMSP for main field modeling. These vector field measurements are calibrated to compute instrument timing shifts, scale factors, offsets, and non-orthogonalities in the fluxgate magnetometer cores. Euler angles are then computed to determine the orientation of the vector magnetometer with respect to a local coordinate system. We fit a degree 12 main field model to the dataset and compare with similar models such as the World Magnetic Model (WMM) and IGRF. Initial results indicate that the DMSP dataset will be a valuable source for main field modeling for the years between CHAMP and the upcoming Swarm mission.

Alken, P.; Redmon, R. J.; Rich, F. J.; Maus, S.; Luhr, H.

2013-12-01

157

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

NASA Astrophysics Data System (ADS)

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

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

2001-08-01

158

Relationship between human physiological parameters and geomagnetic variations of solar origin  

NASA Astrophysics Data System (ADS)

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

Dimitrova, S.

159

Some results of geomagnetic storm events observed at the Brazilian Southern Space Observatory  

NASA Astrophysics Data System (ADS)

Space weather can be defined as the study of solar and interplanetary sources of geomagnetic storms. Coronal mass ejections (CMEs) are large plasma eruptions released from the Sun and they are one of the main solar-interplanetary structures causing the geomagnetic disturbances on Earth. Such events, also named (geomagnetic storms) are caused when there are changes in the plasma and magnetic field in the space that surrounds the Earth's magnetosphere. CME passages are known to be an important origin of such changes. The damage caused by geomagnetic storms are several, including loss of data from satellite, signal scintillation, interference on radar, telecommunications cable disruption, electricity grid disturbance and black-out electrical power. They are also responsible for the appearance of auroras. It is known that quantity of cosmic rays observed in each direction on Earth's surface is approximately unchanged on the time when there are no transient solar-interplanetary events. During disturbed periods, CME may shield cosmic rays, allowing terrestrial detectors to identify some signatures on the same period. Sometimes, these signatures can be identified prior to the occurence of the disturbance using a cosmic ray network around the Earth. With this purpose, a prototype detector of high-energy cosmic rays > 50 GeV, muons, was installed in the Brazilian Southern Space Observatory - SSO/CRS/CIE/INPE - MCT in 2001. It was composed of 2 layers of 4 detectors (2x2x2) with temporal resolution of one hour. The detector was upgraded in 2005 to 56 detectors (2x4x7) and temporal resolution of one minute. The expansion enabled a decrease of error from 0.16% to 0.06% in the counting of muons. The purpose of this paper is to discuss the expansion and to present results of the study of some geomagnetic storm events combining geomagnetic Dst index data, muon count rate data and data from the ACE satellite.

Kemmerich, Níkolas; Dal Lago, Alisson; Schuch, Nelson Jorge; Braga, Carlos Roberto; Deives Kummer, Fabricio; Vinicius Dias Silveira, Marcos; Munakata, Kazuoki; da Silva, Marlos; Martins da Silva, Samuel

160

Ionospheric reflection of the magnetic activity described by the index ?  

Microsoft Academic Search

Differences in the external part of the vertical geomagnetic component point to the existence of local inhomogeneities in the magnetosphere or the ionosphere. Usually used magnetic indices are not sufficient to express the state of ionosphere, the common used global Kp index derived in the three-hour interval does not indicate much more rapidly changes appearing in ionosphere. Magnetic index ?

Beata Dziak-Jankowska; Iwona Stanislawska; Tomasz Ernst; ?ukasz Tomasik

2011-01-01

161

A realistic treatment of geomagnetic Cherenkov radiation from cosmic ray air showers  

NASA Astrophysics Data System (ADS)

We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from three-dimensional Monte Carlo simulations of air showers in a realistic geo-magnetic field. We discuss the importance of a correct treatment of the index of refraction in air, given by the law of Gladstone and Dale, which affects the pulses enormously for certain configurations, compared to a simplified treatment using a constant index. We predict in particular a geomagnetic Cherenkov radiation, which provides strong signals at high frequencies (GHz), for certain geometries together with "normal radiation" from the shower maximum, leading to a double peak structure in the frequency spectrum. We also provide some information about the numerical procedures referred to as EVA 1.0.

Werner, Klaus; de Vries, Krijn D.; Scholten, Olaf

2012-09-01

162

Solar Active Regions Characteristics at Microwaves and Their Association to Geomagnetic Disturbances  

NASA Astrophysics Data System (ADS)

We present the solar active region microwave emission (S component) intensity and polarization degree variations observed with high sensitivity (0.5 sfu) for the period 1998 - 2000, during the rising phase of the 23th solar cycle. The data were obtained by the patrol Solar Radio Polarimeter operating at 7 GHz at Itapetinga Radio Observatory, Atibaia/Brazil. We discuss the correlation between the intensity and polarization degree variations at 7 GHz in association to the flare production in optical and X ray spectral range, and as a function of their intensity. The microwave S component behaviour is also compared to geomagnetic DST index. Interesting correlations between microwave intensity and polarization degree, flare production and geomagnetic DST index are suggested.

Correia, E.; Kaufmann, P.; de Souza, R. V.

2001-05-01

163

Search for worldwide solar eclipse perturbations of geomagnetic activity 1906-1976 - Lunar modulation of Ci revisited  

Microsoft Academic Search

A survey of the geomagnetic Ci index for the years 1906-1976 (164 eclipses) was performed by using a modified version of the t test for the difference of two means to define eclipse departure probability (P sub d). Eclipse epoch Ci changes are shown to satisfy a simple probabilistic model composed of two events: one due to eclipse E and

David D. Meisel; A. F. Blazejewski

1979-01-01

164

Ergodic property of the recent geomagnetic field  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

165

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)

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.

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

166

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

Microsoft Academic Search

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

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

1967-01-01

167

Interplanetary Magnetic Sector Polarity from Polar Geomagnetic Field Observations.  

National Technical Information Service (NTIS)

It has recently been reported that the interplanetary magnetic sector polarity has an influence on the diurnal variation of the polar geomagnetic field. An investigation to infer the interplanetary magnetic sector polarity from the geomagnetic observation...

J. M. Wilcox W. Gonzalez E. Friis-Christensen K. Lassen D. S. Colburn

1971-01-01

168

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

169

Quantifying Power Grid Risk from Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

170

An introduction to quiet daily geomagnetic fields  

USGS Publications Warehouse

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

Campbell, W. H.

1989-01-01

171

Scaling laws from geomagnetic time series  

USGS Publications Warehouse

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.

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

1998-01-01

172

Toward a possible next geomagnetic critical transition?  

NASA Astrophysics Data System (ADS)

The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering the characteristics of the recent geomagnetic field, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards that are really global. The South Atlantic Anomaly (SAA) is a great depression of the geomagnetic field strength at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterized by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power law or logarithmic functions in reverse time, also decorated by log-periodic oscillations, whose final singularity (a critical point tc) reveals a great change in the near future (2034±3 yr), when the SAA area reaches almost a hemisphere. An interesting aspect that has recently been found is the possible direct connection between the SAA and the global mean sea level (GSL). That the GSL is somehow connected with SAA is also confirmed by the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033±11 yr) agrees, within the estimated errors, with the value found for the SAA. From this result, we point out the intriguing conjecture that tc would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

Qamili, Enkelejda; De Santis, Angelo; Wu, Lixin

2014-05-01

173

Toward a possible next geomagnetic transition?  

NASA Astrophysics Data System (ADS)

The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering that: (a) in the last 83 million yr the typical average time between one reversal and the next (the so-called chron) is around 400 000 yr, (b) the last reversal occurred around 780 000 yr ago, (c) more excursions (rapid changes in polarity) can occur within the same chron and (d) the geomagnetic field dipole is currently decreasing, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards that are really global. The South Atlantic Anomaly (SAA) is a great depression of the geomagnetic field strength at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterized by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power law or logarithmic functions in reverse time, also decorated by log-periodic oscillations, whose final singularity (a critical point tc) reveals a great change in the near future (2034 ± 3 yr), when the SAA area reaches almost a hemisphere. An interesting aspect that has recently been found is the possible direct connection between the SAA and the global mean sea level (GSL). That the GSL is somehow connected with SAA is also confirmed by the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033 ± 11 yr) agrees, within the estimated errors, with the value found for the SAA. From this result, we point out the intriguing conjecture that tc would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

De Santis, A.; Qamili, E.; Wu, L.

2013-12-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

175

Impact of Solar wind parameters on Geomagnetic Parameter at 1 AU  

NASA Astrophysics Data System (ADS)

Magnitude of geomagnetic effects largely depends upon the configuration and strength of potentially geo-effective solar/interplanetary features. In the present study the identification of 200 geomagnetic storms associated with disturbance storm time (Dst) decrease of less than -50 nT have been made, which are observed during 1996-2009. The study is made statistically between the Dst strength (used as an indicator of the geomagnetic activity) and the value obtained by solar wind plasma parameters and IMF B as well as its components By and Bz. We have used the hourly values of Dst index and the wind measurements taken by various satellites. We observed that IMF B is highly geo-effective during the main phase of magnetic storms, as well as at the time IP Shock. The correlation between Dst and wind velocity is higher, as compared with IMF southwards components Bz and ion density. It has been verified that geomagnetic storm intensity is correlated well with the total magnetic field strength of IMF better than with its southward component at time of IP shock and instant of Dst minimum.

Rathore, B. S.; Kaushik, S. C.; Gupta, D. C.

2012-12-01

176

A simple statistical model for geomagnetic reversals  

NASA Technical Reports Server (NTRS)

The diversity of paleomagnetic records of geomagnetic reversals now available indicate that the field configuration during transitions cannot be adequately described by simple zonal or standing field models. A new model described here is based on statistical properties inferred from the present field and is capable of simulating field transitions like those observed. Some insight is obtained into what one can hope to learn from paleomagnetic records. In particular, it is crucial that the effects of smoothing in the remanence acquisition process be separated from true geomagnetic field behavior. This might enable us to determine the time constants associated with the dominant field configuration during a reversal.

Constable, Catherine

1990-01-01

177

First geomagnetic measurements in the Antarctic region  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

178

Large Geomagnetic Storms: Introduction to Special Section  

NASA Technical Reports Server (NTRS)

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

Gopalswamy, N.

2010-01-01

179

ULF geomagnetic pulsations in the southern polar cap: Simultaneous measurements near the cusp and the geomagnetic pole  

Microsoft Academic Search

During November 2003, a 1-week test campaign of ULF geomagnetic field measurements was conducted at the new Italian\\/French base of Concordia (Dome C, Antarctic plateau), close to the geomagnetic pole, at a corrected geomagnetic latitude of ?89°S. An analysis of these measurements is presented, together with a comparison with simultaneous measurements conducted at the Italian “Mario Zucchelli” base, at Terra

M. De Lauretis; P. Francia; M. Vellante; A. Piancatelli; U. Villante; D. Di Memmo

2005-01-01

180

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

Microsoft Academic Search

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

H. Toh; Y. Hamano; M. Ichiki

2006-01-01

181

Outcomes of AA for Special Populations  

Microsoft Academic Search

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

Christine Timko

182

S-transform view of geomagnetically induced currents during geomagnetic superstorms  

NASA Astrophysics Data System (ADS)

Novel time-frequency analysis method S-transform capable of handling noisy non-stationary signals is applied to study the properties of geomagnetically induced current GIC fluctuations in the Finnish natural gas pipeline during geomagnetic superstorms New local time- and storm phase-dependent S-transform spectral properties of auroral region GIC fluctuations during geomagnetic superstorms are reported More specifically the S-transform spectra have two distinct regions containing the most of the spectral power that persisted from storm to storm main phase-related wide-band fluctuations driven possibly by substorm-type ionospheric activity centered around local midnight and recovery phase-related narrow-band fluctuations associated with Pc5 range geomagnetic pulsations in the local morning region Based on this observed stability a new S-transform-based statistical approach using for example an ensemble of different S-transform responses for known storms is proposed for GIC prediction

Pulkkinen, A.; Kataoka, R.

183

S-transform analysis of geomagnetically induced currents during intense geomagnetic storms  

NASA Astrophysics Data System (ADS)

Novel time-frequency analysis method (S-transform) capable of handling noisy nonstationary signals is applied to study the properties of geomagnetically induced current (GIC) fluctuations in the Finnish natural gas pipeline during intense geomagnetic storms. New local time- and storm phase-dependent S-transform spectral properties of auroral region GIC fluctuations during the geomagnetic storms are reported. More specifically, the S-transform spectra have two distinct regions containing the most of the spectral power that persisted from storm to storm: main phase-related wide-band fluctuations driven possibly by substorm-type ionospheric activity centered around local midnight and recovery phase-related narrow-band fluctuations associated with Pc5 range geomagnetic pulsations in the local morning region. Based on this observed stability, a new S- transform-based statistical approach using, for example, an ensemble of different S-transform responses for known storms is proposed for GIC prediction.

Kataoka, R.; Pulkkinen, A.

2006-12-01

184

Results of Geomagnetic Observations at the Hurbanovo Geomagnetic Observatory in 1985.  

National Technical Information Service (NTIS)

The absolute observations were made at regular intervals of 7 days, activity of the geomagnetic field permitting. Some observations with the proton magnetometer, however, were made more frequently, i.e., twice a week. Declination, horizontal component, ve...

1986-01-01

185

Geomagnetic signatures during the intense geomagnetic storms of 29 October and 20 November 2003  

Microsoft Academic Search

Solar cycle 23 in its declining phase witnessed the most pronounced space weather events during October–November 2003. A series of powerful solar flares and associated geoeffective Coronal Mass Ejections (CMEs) travelling at ?2000km\\/s drove shock fronts that impacted the Earth's magnetic field consecutively on 29 and 30 October, resulting in intense geomagnetic disturbances during 29–31 October. Another intense geomagnetic storm

S. Alex; S. Mukherjee; G. S. Lakhina

2006-01-01

186

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

SciTech Connect

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

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

1985-01-01

187

Geomagnetic storms link to the mortality rate in the Smolyan region for the period 1988--2009  

NASA Astrophysics Data System (ADS)

We present correlations and trends of 10 parameters of annual mortality rate (1 to common mortality rate, 5 to cardiovascular reasons and 4 to "accidental" reasons (car accidents, suicides, infections)) with respect to 6 parameters of annual solar and geomagnetic activity (Wolf index, number of geomagnetic storms, duration of the storms, amplitude of the storms). During the period of observation, characterized by a 3-4-fold decrease of the mean geomagnetic activity (in terms of the number and the duration of the storms) and with a strong variations of the amplitude of the storms (about an almost constant mean values for the period), there is a 1.3-fold decrease in the urban population, a 1.5-fold increase of the common mortality rate, a 1.8-fold increase of the cardiovascular mortality rate and a 1.1-fold decrease of the "accidental" mortality rates. During the years 2003-2005 we observe about 2-fold temporary increase in the storm amplitudes. During the years 2007-2008, characterized by extremely low geomagnetic activity, we observe a surprising temporary increase of the common and the cardiovascular mortality rates 1.1 and 1.3-fold, respectively (Figures 1-4). We point out 3 main results. (1) The available data shows notable increase in the mortality rates while there is generally a decrease of the solar or geomagnetic activity during the studied period (Figures 5-9). We explain this anti-correlation with the domination of the increasing mortality rates as an effect of the advance in the mean age of the population (due to immigration of young people and decrease of new-borns), hiding an eventual display of the solar and geomagnetic influence on the mortality rates. Using this data we can not reveal influence of the long-time (10-20 years) change of the average solar and geomagnetic activity on the mortality rate. (2) Excluding the unusual years 2007 and 2008, we establish that with respect to the years with low geomagnetic activity (1993, 1995, 1996, 1999), in the years with high geomagnetic activity (2000, 2001, 2003-2005) the common and the cardiovascular mortality rates increase by at least 20% and at least 30%, respectively (Figures 10-13). (3) The time delay of the maximum of the common and the cardiovascular mortality rates in 2007-2008, about 3 years after the sharp maximum of the strong storms in 2003-2005, lead to suggestion that the influence of the storms on the mortality rates may manifest clearly itself some years later. Generally, our data shows that the geomagnetic storms increase notable the common and the cardiovascular mortality rates.

Simeonova, Siyka G. 1; Georgieva, Radostina C. 2; Dimitrova, Boryana H. 2; Slavcheva, Radka G. 2; Kerimova, Bojena P. 2; Georgiev, Tsvetan B. 34

188

CISLUNAR GEOMAGNETIC TAIL GRADIENT IN 1967  

Microsoft Academic Search

In this letter, the geomagnetic tail field gradient during the summers of 1966 and 1967 is examined for secular change. We use data from Ames magnetometers on Explorers 33 and 35. The 1967 data are compared with the earlier published 1966. Explorer 33 results [Mihalo. v et al., 1968]. Secular change of the tail field magnitude gradient is not found

J. D. Mihalov; C. P. Sonett

1968-01-01

189

F2-region response to geomagnetic disturbances  

Microsoft Academic Search

The F2-region response to a geomagnetic storm usually called a ionospheric storm is a rather complicated event. It consists of the so-called positive an negative phases, which have very complicated spatial and temporal behavior. During the recent decade there was significant progress in understanding this behavior. The principal features of the positive and negative phase distribution and variations have been

A. D. Danilov

2001-01-01

190

Geomagnetically induced current effects on transformers  

Microsoft Academic Search

Geomagnetically induced currents (GICs) can cause saturation of the magnetic circuit of transformers in a power system. This saturation can increase the MVAr absorption of the transformers, leading to voltage-control problems, generating significant harmonic currents, and cause heating of the internal components of the transformer itself, leading to gas relay alarm\\/operation as well as possible damage. This paper sets out

Philip R. Price

2002-01-01

191

Power lines and the geomagnetic field.  

PubMed

The metric of prime interest in power line epidemiological studies has been AC magnetic intensity. To consider also possible geomagnetic involvement, the orientation of a long straight power line is examined relative to a uniform geomagnetic field (GMF) with dip angle alpha. An expression is derived for the component of the total GMF that is parallel, at an elevation beta, to the circuital magnetic field that surrounds the line. This component is a function of the angles alpha and beta, the total geomagnetic intensity BT, and the angle theta between the axis of the power line and magnetic north. Plotting these geomagnetic parameters for known leukemia residences allows one to test for possible ion cyclotron resonance or other GMF interactions. This approach, in principle, is an easy addition to existing or planned studies, because residential access is not required to obtain local values for alpha, beta, theta, and BT. We recommend including these parameters in the design of epidemiological studies examining power line fields and childhood leukemia. PMID:7488255

Liboff, A R; McLeod, B R

1995-01-01

192

Atmospheric Helium and Geomagnetic Field Reversals.  

National Technical Information Service (NTIS)

The problem of the earth's helium budget is examined in the light of recent work on the interaction of the solar wind with nonmagnetic planets. It is proposed that the dominant mode of helium (4He) loss is ion pumping by the solar wind during geomagnetic ...

J. W. Kern W. R. Sheldon

1972-01-01

193

Statistical Structure of Geomagnetic Field Reversals  

Microsoft Academic Search

Geomagnetic polarity intervals determined from the analysis of the marine magnetic field have been subjected to statistical analysis. The major finding is that the statis'ical structure undergoes a discontinuous change around 50 million years ago. The polarity intervals from 0 to 48 m.y. form a stationary sequence and are governed by gamma distribution, but the intervals are not independent. The

P. S. Naidu

1971-01-01

194

Power lines and the geomagnetic field  

SciTech Connect

The metric of prime interest in power line epidemiological studies has been AC magnetic intensity. To consider also possible geomagnetic involvement, the orientation of a long straight power line is examined relative to a uniform geomagnetic field (GMF) with dip angle {alpha}. An expression is derived for the component of the total GMF that is parallel, at an elevation {beta}, to the circular magnetic field that surrounds the line. This component is a function of the angles {alpha} and {beta}, the total geomagnetic intensity B{sub T}, and the angle {theta} between the axis of the power line and magnetic north. Plotting these geomagnetic parameters for known leukemia residences allows one to test for possible ion cyclotron resonance or other GMF interactions. This approach, in principle, is an easy addition to existing or planned studies, because residential access is not required to obtain local values for {alpha}, {beta}, {theta}, and B{sub T}. The authors recommend including these parameters in the design of epidemiological studies examining power line fields and childhood leukemia.

Liboff, A.R. [Oakland Univ., Rochester, MI (United States). Dept. of Physics; McLeod, B.R. [Montana State Univ., Bozeman, MT (United States). Dept. of Electrical Engineering

1995-09-01

195

CONFIGURATION AND RECONNECTION OF THE GEOMAGNETIC TAIL  

Microsoft Academic Search

A description of certain aspects of the geomagnetic tail is made using data from the Ames magnetometer on the Explorer 33 satellite. The general shape corresponds with eaxlier findings of Ness and co-workers. The tail is found regular to distances greater than 82 R. The field values for Kp _ 2-]- vary from a low of about 4 gammas to

J. D. Mihalov; D. S. Colburn; R. G. Currie; C. P. Sonett

1968-01-01

196

Helio-geomagnetic influence in cardiological cases  

NASA Astrophysics Data System (ADS)

The effects of the energetic phenomena of the Sun, flares and coronal mass ejections (CMEs) on the Earth's ionosphere-magnetosphere, through the solar wind, are the sources of the geomagnetic disturbances and storms collectively known as Space Weather. The research on the influence of Space Weather on biological and physiological systems is open. In this work we study the Space Weather impact on Acute Coronary Syndromes (ACS) distinguishing between ST-segment elevation acute coronary syndromes (STE-ACS) and non-ST-segment elevation acute coronary syndromes (NSTE-ACS) cases. We compare detailed patient records from the 2nd Cardiologic Department of the General Hospital of Nicaea (Piraeus, Greece) with characteristics of geomagnetic storms (DST), solar wind speed and statistics of flares and CMEs which cover the entire solar cycle 23 (1997-2007). Our results indicate a relationship of ACS to helio-geomagnetic activity as the maximum of the ACS cases follows closely the maximum of the solar cycle. Furthermore, within very active periods, the ratio NSTE-ACS to STE-ACS, which is almost constant during periods of low to medium activity, changes favouring the NSTE-ACS. Most of the ACS cases exhibit a high degree of association with the recovery phase of the geomagnetic storms; a smaller, yet significant, part was found associated with periods of fast solar wind without a storm.

Katsavrias, Ch.; Preka-Papadema, P.; Moussas, X.; Apostolou, Th.; Theodoropoulou, A.; Papadima, Th.

2013-01-01

197

Geomagnetic activity indicators for geomagnetically induced current studies in South Africa  

NASA Astrophysics Data System (ADS)

Intense geomagnetic activity is known to give rise to large geomagnetically induced currents (GICs) in power transmission grids. Recordings of geomagnetic activity provide an efficient and economical way for power transmission system operators to assess GIC risks in retrospective studies. This study investigates local geomagnetic indicators (i.e., hourly peak value, hourly range indicator and hourly standard deviation) in order to determine their usefulness for understanding the drivers of GICs in the South African power network. Results show that the GICs have a higher correlation with the geomagnetic indicators derived from the East-West component of the horizontal geomagnetic field, than the indicators derived from the North-South component of the horizontal field. This directional dependence corresponds very well with the North-South orientation of the power lines feeding the power transformers at the South African Grassridge electrical substation GIC site. It therefore follows that, the geoelectric field driving the GICs at Grassridge is North-South oriented. Further, it is shown that the hourly range indicator has a higher correlation with the GICs than the hourly standard deviation for this particular network configuration.

Ngwira, Chigomezyo M.; McKinnell, Lee-Anne; Cilliers, Pierre J.

2011-08-01

198

Recent Investigations on AA Doradus  

NASA Astrophysics Data System (ADS)

AA Dor is an eclipsing, post common-envelope binary with an sdOB-type primary and an unseen low-mass secondary, believed to be a brown dwarf. Eleven years ago, a NLTE spectral analysis of the primary showed a discrepancy with the surface gravity that was derived by radial-velocity and light-curve analysis that could not be explained. Since then, emission lines of the secondary were identified in optical spectra and its orbital-velocity amplitude was measured. Thus, the masses of both components are known, however, within relatively large error ranges. The secondary's mass was found to be around the stellar hydrogen-burning mass limit and, thus, it may be a brown dwarf or a late M-type dwarf. In addition, a precise determination of the primary's rotational velocity showed recently, that it rotates at about 65% of bound rotation—much slower than previously assumed. A new spectral analysis by means of metal-line blanketed, state-of-the-art, non-LTE model atmospheres solves the so-called gravity problem in AA Dor—our result for the surface gravity is, within the error limits, in agreement with the value from light-curve analysis. We present details of our recent investigations on AA Dor.

Rauch, T.

2012-03-01

199

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

200

A New Empirical Model For Geomagnetic Perturbations  

NASA Astrophysics Data System (ADS)

Prior methods for calculating geomagnetic perturbations as a function of the solar wind/interplanetary magnetic field (IMF) are often based on simulation or empirical calculations of the electric fields and currents in the ionosphere. The geomagnetic perturbations at ground level are calculated from the ionospheric parameters without having a complete knowledge of the ionospheric conductance as well as the effects of induced, underground currents. A new empirical model for geomagnetic predictions is under development, based on global measurements of the ground level geomagnetic field, along with the simultaneous measurements of the IMF. This model uses measurements from over 100 stations in the Northern hemisphere, presently from a four-year interval. This new model will be able to more accurately reproduce the geomagnetic fluctuations for a given set of IMF conditions, since it bypasses the need for ionospheric models and also implicitly includes conductivity variations. Comparisons of IMF-derived model “predictions” with measurements at different locations show very good results, even for stations location near the South pole. Variations on long temporal scales have very good agreement, particularly in the polar cap. Within the auroral zone there are often higher frequency variations from the prediction level, due to the storage and release substorm cycle, as well as the random motions of the aurora. Due to their chaotic nature, the most rapid variations may never be predictable other than by an estimation of probabilities, much like present day forecasts of atmospheric thunderstorms. The latitude-MLT maps of the Northward and Eastward components of the magnetic perturbations that are produced from this model as a function of the IMF are very consistent with the corresponding maps of the ionospheric electric potentials. Interestingly, the maps of the Vertical component very much resemble the maps of ionospheric field-aligned currents.

Weimer, D. R.; Clauer, C. R.

2009-12-01

201

Geomagnetic field evolution during the Laschamp excursion  

NASA Astrophysics Data System (ADS)

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.

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

2009-02-01

202

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

NASA Astrophysics Data System (ADS)

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

Lemperger, István; Menvielle, Menvielle; Wesztergom, Viktor; Bencze, Pál; Szendr?i, Judit; Novák, Attila; Kis, Árpád; Szalai, Sándor

2014-05-01

203

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

PubMed

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

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

2002-05-01

204

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

NASA Astrophysics Data System (ADS)

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

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

205

Ionospheric Behaviors Over Korea Peninsula During the Super Geomagnetic Storm Using GPS Measurements  

NASA Astrophysics Data System (ADS)

The super-geomagnetic storms called 2003 Halloween event globally occurred during the period of 29 through 31 which are the following days when the solar flares of X18 class exploded on 28 October 2003. The S4 index from GPS signal strength and the peak electron density (NmF2) from GPS tomography method are analyzed according to the date. The occurrences of the cycle slip and scintillation in the GPS signals are 1,094 and 1,387 on 28 and 29 October, respectively and these values are higher than 604 and 897 on 30 and 31 October. These mean the ionospheric disturbances are not always generated by the period of geomagnetic storm. Therefore, GPS S4 index is useful to monitor the ionospheric disturbances. Behaviors of ionospheric electron density estimated from GPS tomography method are analyzed with the date. At UT = 18 hr, the maximum NmF2 is shown on 28 October. It agrees with NmF2 variation measured from Anyang ionosonde, and the GPS signal are better condition on 30 and 31 October than 28 October. In conclusion, GPS signal condition is relation with geomagnetic activities, and depend upon the variation of the electron density. We will study the long-term data to examine the relationship between the GPS signal quality and the electron density as the further works.

Chung, Jong-Kyun; Choi, Byung-Kyu; Baek, Jungho; Jee, Geonhwa; Cho, Jungho

2009-12-01

206

Relations of the energetic proton fluxes in the central plasma sheet with solar wind and geomagnetic activities  

NASA Astrophysics Data System (ADS)

this paper, using 9 years of Cluster data, we statistically investigate the relations of central plasma sheet energetic proton fluxes, ~30 keV to 380 keV, with the solar wind parameters and geomagnetic indexes. The energetic proton fluxes increase with increasing solar wind dynamical pressure and solar wind speed. The energetic proton fluxes are more correlated with solar wind dynamical pressure than with solar wind speed. During northward interplanetary magnetic field (IMF) Bz, energetic proton fluxes are independent of northward IMF Bz, while during southward IMF Bz, energetic proton fluxes are highly correlated with southward IMF Bz and increase with increasing |IMF Bz|. The response time of energetic proton flux to southward IMF Bz is between 40 and 100 min. The energetic proton fluxes are correlated with plasma sheet ion temperature. The energetic proton fluxes increase with increasing indexes of Kp, AE, and |Dst|. Among the three geomagnetic indexes, the central plasma sheet energetic proton fluxes are most correlated with Kp index with the largest correlation coefficient being 0.82. The energetic proton fluxes are large during positive Dst index, suggesting that the sharp increase of solar wind dynamical pressure can enhance the plasma sheet energetic proton fluxes. The enhanced plasma sheet energetic proton fluxes may be important for geomagnetic storms and substorms since they can possibly directly become the source of ring current and substorm-injected energetic particles without the need of additional acceleration process in the inner magnetosphere.

Cao, Jinbin; Duan, Aiying; Reme, Henri; Dandouras, Iannis

2013-11-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2001-09-01

208

Forbush Decreases Associated with Western Solar Sources and Geomagnetic Storms: A Study on Precursors  

NASA Astrophysics Data System (ADS)

As suggested in many studies the pre-increases or pre-decreases of the cosmic ray intensity (known as precursors), which usually precede a Forbush decrease, could serve as a useful tool for studying space weather effects. The events in this study were chosen based on two criteria. Firstly, the heliolongitude of the solar flare associated with each cosmic ray intensity decrease was in the 50° -70°W sector and, secondly, the values of the geomagnetic activity index, Kp max, were ? 5. Twenty five events were selected from 1967 to 2006. We have used data on solar flares, solar wind speed, geomagnetic indices ( Kp and Dst), and interplanetary magnetic field in our detailed analysis. The asymptotic longitudinal cosmic ray distribution diagrams were plotted using the "Ring of Stations" method for all the events. The results reveal clear signs of precursors in 60 % of selected events.

Papailiou, M.; Mavromichalaki, H.; Abunina, M.; Belov, A.; Eroshenko, E.; Yanke, V.; Kryakunova, O.

2013-04-01

209

On the high correlation between long-term averages of solar wind speed and geomagnetic activity  

NASA Technical Reports Server (NTRS)

Six-month and yearly averages of solar-wind speed from 1962 to 1975 are shown to be highly correlated with geomagnetic activity as measured by averages of the Ap index. On the same time scale the correlation between the southward component of the interplanetary magnetic field and geomagnetic activity is poor. Previous studies with hourly averages gave opposite results. The better correlation with the southward component on an hourly time scale is explained by its large variation compared with the relatively constant solar-wind speed. However, on a yearly time scale the magnitude of the variations in both parameters are about the same. This problem can be solved by invoking an energy transfer mechanism which is proportional to the first power of the southward component and a higher power of the solar-wind speed.

Crooker, N. U.; Feynman, J.; Gosling, J. T.

1977-01-01

210

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

211

Laboratory Astrophysics Division of the AAS (LAD)  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

212

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

NASA Astrophysics Data System (ADS)

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.

Sharma, A. K.; et al.

2006-11-01

213

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

NASA Astrophysics Data System (ADS)

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

Pietrella, M.

2014-07-01

214

Improvements in short-term forecasting of geomagnetic activity  

NASA Astrophysics Data System (ADS)

We have improved our space weather forecasting algorithms to now predict Dst and AE in addition to Kp for up to 6 h of forecast times. These predictions can be accessed in real time at http://mms.rice.edu/realtime/forecast.html. In addition, in the event of an ongoing or imminent activity, e-mail "alerts" based on key discriminator levels have been going out to our subscribers since October 2003. The neural network-based algorithms utilize ACE data to generate full 1, 3, and 6 h ahead predictions of these indices from the Boyle index, an empirical approximation that estimates the Earth's polar cap potential using solar wind parameters. Our models yield correlation coefficients of over 0.88, 0.86, and 0.83 for 1 h predictions of Kp, Dst, and AE, respectively, and 0.86, 0.84, and 0.80 when predicting the same but 3 h ahead. Our 6 h ahead predictions, however, have slightly higher uncertainties. Furthermore, the paper also tests other solar wind functions—the Newell driver, the Borovsky control function, and adding solar wind pressure term to the Boyle index—for their ability to predict geomagnetic activity.

Bala, Ramkumar; Reiff, Patricia

2012-06-01

215

Real-Time WINDMI Predictions of Geomagnetic Storms and Substorms  

NASA Astrophysics Data System (ADS)

The performance of the Real-Time WINDMI model is surveyed for its predictions of storm/substorm events from February 2006 to present time. Three solar wind-magnetosphere dynamo voltage Vsw(t) coupling functions are used: the standard Rectified coupling function, a function due to Siscoe, and a recent function due to Newell. Real-Time WINDMI is a low dimensional, plasma physics-based, nonlinear dynamical model of the coupled solar wind- magnetosphere-ionosphere system. The realtime model at CCMC/GSFC downloads ACE data to predict AL and Dst values approximately one hour before geomagnetic substorm and storm events; subsequently, every ten minutes ground based measurements compiled by WDC Kyoto are compared with model predictions(http://orion.ph.utexas.edu/~windmi/realtime/). Model AL and Dst predictions are validated using the average relative variance (ARV),correlation coefficient (COR), and root mean squared error (RMSE). Model AL predictions correlate at least one standard deviation better with the AL index data than a direct correlation between the input coupling functions and the AL index. The earlier 2006-2008 data analysis showed that the best prediction performance for the Dst came from using the Rectified input. The work is supported by NSF grant AGS 0964692.

Horton, W.; Mays, M. L.; Spencer, E. A.

2010-12-01

216

Geomagnetic modeling by optimal recursive filtering  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

217

NOAA Plans for Geomagnetic Storm Observations  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

218

Precipitation Behavior of AA2618  

NASA Astrophysics Data System (ADS)

The precipitation behavior of AA2618 was studied by a multitude of characterization techniques: microhardness testing, lattice parameter measurement through X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and atom probe field ion microscopy (APFIM). The matrix lattice parameter increased during the first 20 hours of natural aging, due to the formation of Cu clusters and decreased over the next 24 hours, due to the formation of Mg-rich clusters. Prior natural aging weakened subsequent artificial aging hardening at 180 °C, 200 °C, and 230 °C, due to the cluster reversion that delayed the precipitation of strengthening phases. The matrix lattice parameter exhibited erratic changes during artificial aging that corresponded to the formation and partial dissolution of Guinier Preston Bagaryatsky (GPB) zones, the transformation of GPB zones to GPB2 zones, and the precipitation of S'. The structural changes during the artificial aging of AA2618 occur in this sequence: supersaturated solid solution ? clusters + GPB ? GPB + GPB2 ? GPB2 + S' ? S'+ S ? S.

Lu, H.; Kadolkar, P.; Nakazawa, K.; Ando, T.; Blue, C. A.

2007-10-01

219

Visualization of geomagnetic field for education and outreach  

NASA Astrophysics Data System (ADS)

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.

Hatakeyama, T.

2010-12-01

220

Domino model for geomagnetic field reversals.  

PubMed

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

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

2013-01-01

221

AI techniques in geomagnetic storm forecasting  

NASA Astrophysics Data System (ADS)

This review deals with how geomagnetic storms can be predicted with the use of Artificial Intelligence (AI) techniques. Today many different Al techniques have been developed, such as symbolic systems (expert and fuzzy systems) and connectionism systems (neural networks). Even integrations of AI techniques exist, so called Intelligent Hybrid Systems (IHS). These systems are capable of learning the mathematical functions underlying the operation of non-linear dynamic systems and also to explain the knowledge they have learned. Very few such powerful systems exist at present. Two such examples are the Magnetospheric Specification Forecast Model of Rice University and the Lund Space Weather Model of Lund University. Various attempts to predict geomagnetic storms on long to short-term are reviewed in this article. Predictions of a month to days ahead most often use solar data as input. The first SOHO data are now available. Due to the high temporal and spatial resolution new solar physics have been revealed. These SOHO data might lead to a breakthrough in these predictions. Predictions hours ahead and shorter rely on real-time solar wind data. WIND gives us real-time data for only part of the day. However, with the launch of the ACE spacecraft in 1997, real-time data during 24 hours will be available. That might lead to the second breakthrough for predictions of geomagnetic storms.

Lundstedt, Henrik

222

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

223

S-transform view of geomagnetically induced currents during geomagnetic superstorms  

NASA Astrophysics Data System (ADS)

A novel time-frequency analysis method (S-transform) capable of handling noisy non-stationary signals is applied to study the properties of geomagnetically induced current (GIC) fluctuations in the Finnish natural gas pipeline. New local time- and storm phase-dependent S-transform spectral properties of auroral region GIC fluctuations during geomagnetic superstorms are reported. More specifically, the S-transform spectra have two distinct regions containing the most of the spectral power that persisted from storm to storm: main phase-related wide-band fluctuations driven possibly by a substorm-type ionospheric activity centered around the local midnight and recovery phase-related narrow-band fluctuations associated with Pc5 range geomagnetic pulsations in the local morning region. Based on this observed ``stability'', a new S-transform-based statistical approach using, for example, an ensemble of different S-transform responses for known storms is proposed for GIC prediction.

Pulkkinen, Antti; Kataoka, Ryuho

2006-06-01

224

Disturbances in the US electric grid associated with geomagnetic activity  

NASA Astrophysics Data System (ADS)

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

Schrijver, Carolus J.; Mitchell, Sarah D.

2013-05-01

225

Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations  

NASA Technical Reports Server (NTRS)

In order to infer the interplanetary sector polarity from polar geomagnetic field diurnal variations, measurements were carried out at Godhavn and Thule (Denmark) Geomagnetic Observatories. The inferred interplanetary sector polarity was compared with the polarity observed at the same time by Explorer 33 and 35 magnetometers. It is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar cap geomagnetic fields.

Friis-Christensen, E.; Lassen, K.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

1971-01-01

226

Latitude-Dependent Characteristics of Long-Period Geomagnetic Micropulsations  

Microsoft Academic Search

In summer 1969 a line of 7 magnetic stations was set up in western Canada between the geomagnetic latitudes of 59 ø and 77øN and within 2 ø of 302øE corrected geomagnetic longitude. This paper concerns the analysis of the horizontal components of quasi-monochromatic, geomagnetic micropulsations recorded at these stations over 3 days. Both the amplitude spectra and the sense

J. C. Samson; J. A. Jacobs; G. Rostoker

1971-01-01

227

AAS Statistics and the 60% Cohort  

NASA Astrophysics Data System (ADS)

I will present the latest statistics available describing the gender of the AAS membership including an update on the so-called 60% cohort (that group of AAS members from the ages of 18 to 25 who are 60% women and 40% men). The AAS membership has changed significantly in the past 30 years from an overall female membership percentage of about 10% to a level around 30% today. This trend is accelerating and indicates the ongoing inclusion of women in the physical sciences, especially astronomy. By the year 2030, the AAS membership should reach gender parity if the present trend continues.

Marvel, K. B.

2004-05-01

228

CIRA Solar Irradiances and Solar/Geomagnetic Indices  

NASA Astrophysics Data System (ADS)

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

Tobiska, W. Kent

229

Geomagnetic field models incorporating physical constraints on the secular variation  

NASA Technical Reports Server (NTRS)

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

Constable, Catherine; Parker, Robert L.

1993-01-01

230

Indexing Images.  

ERIC Educational Resources Information Center

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

Rasmussen, Edie M.

1997-01-01

231

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

NASA Astrophysics Data System (ADS)

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

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

232

Enhancement of solar wind low-energy energetic particles as precursor of geomagnetic disturbance in operational geomagnetic forecast  

NASA Astrophysics Data System (ADS)

A study of the relationship between solar wind low-energy energetic particles using data from the Electron, Proton, and Alpha Monitor (EPAM) onboard the Advanced Compositional Explorer spacecraft (ACE) and geomagnetic activity using data from Canadian magnetic observatories in Canada's polar cap, auroral zone, and subauroral zone was carried out for a period spanning 1997-2005. Full halo coronal mass ejections (CMEs) were used to gauge the initial particle enhancements and the subsequent geomagnetic activity. It was found that maximum geomagnetic activity is related to maximum particle enhancements in a non-linear fashion. Quadratic fit of the data results in expressions that can be easily used in an operational space weather setting to forecast geomagnetic disturbance quantitatively. A superposed epoch analysis shows increase in particle flux level starts hours before geomagnetic activity attains its peak, affirming the precursory nature of EPAM particles for the impending geomagnetic impact of CME. This can supplement the decision process in formulating geomagnetic warning after the launch of CME from the Sun but before the arrival of shock at Earth. The empirical relationships between solar wind low-energy energetic particles and geomagnetic activity revealed in this statistical study can be easily codified, and thus utilized in operational space weather forecast to appraise the geoeffectiveness of the CME and to provide a quantitative forecast for maximum geomagnetic activity in Canada's polar cap, auroral zone, and subauroral zone after the occurrence of a CME.

Lam, H.-L.

2009-05-01

233

Correlation as a global measure of geomagnetic activity: Phase boundaries and a precedent line of nodes  

NASA Astrophysics Data System (ADS)

This work considers the global correlation of geomagnetic activity as a way to evaluate magnetotail disturbances, such as the substorm. Impulsive magnetotail disturbances are generally associated with geomagnetic pulsations, which can be coherent over wide ranges of latitude and longitude, and which display distinctive phase reversals collocated with power maxima. Analyzing a disturbance period chosen for its breadth in local time, we find that pulsations can be detected from the coherence that they generate within a magnetometer array, and identify an extended line of nodes across which the phase reversals occur. Phase reversals consistent with the same line of nodes persist for five hours, beginning clearly in a 0.7 mHz pulsation one and a half hours before the disturbance, and persisting in a 5.8 mHz pulsation three and one half hours after the initial disturbance. Under the hypothesis that the line of nodes maps to a source in the central plasma sheet (CPS), we note that the persistence of this extended source of disturbances suggests memory in the CPS. We define a quantitative “coherence index” that characterizes geomagnetic activity according to the degree of global coherence that it generates, and observe that a narrowly peaked coherence signal leads a much broader peak in power. We relate these results to models of the magnetosphere based in critical phenomena.

Cosgrove, Russell; Sanchez, Ennio

2012-06-01

234

Correlation as a global measure of geomagnetic activity: Phase boundaries and a precedent line of nodes  

NASA Astrophysics Data System (ADS)

We will describe our recent paper, which considers the global correlation of geomagnetic activity as a way to evaluate magnetotail disturbances, such as the substorm. Impulsive magnetotail disturbances are generally associated with geomagnetic pulsations, which can be coherent over wide ranges of latitude and longitude, and which display distinctive phase reversals collocated with power maxima. Analyzing a disturbance period chosen for its breadth in local time, we find that pulsations can be detected from the coherence that they generate within a magnetometer array, and identify an extended line of nodes across which the phase reversals occur. Phase reversals consistent with the same line of nodes persist for five hours, beginning clearly in a 0.7 mHz pulsation one and a half hours before the disturbance, and persisting in a 5.8 mHz pulsation three and one half hours after the initial disturbance. Under the hypothesis that the line of nodes maps to a source in the central plasma sheet (CPS), we note that the persistence of this extended source of disturbances suggests memory in the CPS. We define a quantitative "coherence index" that characterizes geomagnetic activity according to the degree of global coherence that it generates, and observe that a narrowly peaked coherence signal leads a much broader peak in power. We relate these results to models of the magnetosphere based in critical phenomena.

Cosgrove, R. B.; Sanchez, E. R.

2012-12-01

235

Precursors of Forbush decreases connected to western solar sources and geomagnetic storms  

NASA Astrophysics Data System (ADS)

It is suggested in many studies that the pre-increases or pre-decreases of the cosmic ray intensity (known as precursors) which usually precede a Forbush decrease could serve as a useful tool for studying space weather effects. The events under consideration in this particular investigation were chosen based on two criteria. Firstly, the heliolongitude of the solar flare associated with each cosmic ray intensity decrease was in the 50°-70°W sector and secondly, the values of geomagnetic activity index (Kpmax) were >= 5. As a result only Forbush decreases connected to western solar flares and accompanied by a geomagnetic storm were selected. In total 25 events were gathered for the time period from 1967 to 2006. For the detailed analysis of the aforementioned cosmic ray intensity decreases data on solar flares, solar wind speed, geomagnetic indices (Kp and Dst) and interplanetary magnetic field were used. The asymptotic longitudinal cosmic ray distribution diagrams for all events were plotted using the "Ring of Stations" method. The results revealed clear signs of precursors in 60% of selected events.

Papailiou, M.; Mavromichalaki, H.; Abunina, M.; Belov, A.; Eroshenko, E.; Yanke, V.

2013-02-01

236

Statistical analyses of influence of solar and geomagnetic activities on car accident events.  

PubMed

Statistical analyses of the influence of Solar and geomagnetic activity, sector structure of the interplanetary magnetic field and galactic cosmic ray Forbush effects on car accident events in Poland for the period of 1990-1999 have been carried out. Using auto-correlation, cross-correlation, spectral analyses and superposition epochs methods it has been shown that there are separate periods when car accident events have direct correlation with Ap index of the geomagnetic activity, sector structure of the interplanetary magnetic field and Forbush decreases of galactic cosmic rays. Nevertheless, the single-valued direct correlation is not possible to reveal for the whole period of 1990-1999. Periodicity of 7 days and its second harmonic (3.5 days) has been reliably revealed in the car accident events data in Poland for the each year of the period 1990-1999. It is shown that the maximum car accident events take place in Poland on Friday and practically does not depend on the level of solar and geomagnetic activities. PMID:11803971

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

2001-01-01

237

Processing Electronic Abstracts for AAS Meetings  

Microsoft Academic Search

The AAS has accepted abstracts for its last three meetings via electronic mail. On balance, this experiment has been well-received by the community (over 80% of the abstracts for this meeting were taken via email), even though the AAS only accepts electronic abstracts prepared with a specific template. Despite an enhanced number of submissions close to the deadline, abstract processing

H. Dalterio

1993-01-01

238

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

NASA Astrophysics Data System (ADS)

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 plasma to relativistic levels by as yet unknown excitation mechanisms. By exploiting data from the Advanced Composition Explorer (ACE) spacecraft in conjunction with space- and ground-based measurements of geospace over the last solar cycle, a database of geomagnetic storms has been compiled and analysed. Here we present some statistical findings from a superposed epoch analysis of 143 events identified from the global SYM-H index. We find that the duration of the main phase of storms decreases for increasing storm size, as defined by the maximum negative excursion of SYM-H, contrary to the results of previous studies. We also discuss a comparison of CME and CIR driven storms in terms of storm size, phase duration and evolution, and the associated solar wind-magnetosphere coupling. Initial work has successfully identified characteristic radar backscatter observed by the Super Dual Auoral Radar Network (SuperDARN) and, in particular, the new lower-latitude StormDARN radar network during these storm-time conditions. Here we present early findings of a superposed epoch analysis of auroral imagery from the IMAGE spacecraft and ionospheric convection maps from the SuperDARN radar network. This work further illustrates the storm-time coupling between the solar wind and magnetosphere, and develops the relationship between auroral oval radius and the evolution of the storm-time SYM-H index first reported by Milan et al., (2009). Once completed, this will be the most complete superposed epoch analyses of storms to date, combining multiple datasets and analysis techniques. This will enable us to gain a better understanding of complex storm time processes such as the energisation of ring current plasmas.

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

2010-12-01

239

Results of geomagnetic observations at the Hurbanovo Geomagnetic Observatory in 1985  

NASA Astrophysics Data System (ADS)

The absolute observations were made at regular intervals of 7 days, activity of the geomagnetic field permitting. Some observations with the proton magnetometer, however, were made more frequently, i.e., twice a week. Declination, horizontal component, vertical component, and total field measurements were taken.

240

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

NASA Astrophysics Data System (ADS)

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

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

241

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

PubMed Central

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 increased AA attendance, the practice of prescribed AA activities, and self-reported AA usefulness. It appears that a sense of belongingness predicts subsequent engagement in the AA social network that, in turn, is predictive of increased abstinence.

RICE, SAMARA LLOYD; TONIGAN, J. SCOTT

2014-01-01

242

Geographical localisation of the geomagnetic secular variation  

NASA Astrophysics Data System (ADS)

Directly observed changes in Earth's magnetic field occur most prominently at low latitudes beneath the Atlantic hemisphere, while the Pacific is comparatively quiet. This striking hemispheric asymmetry in geomagnetic secular variation is a consequence of the geographical localisation of intense, westward moving, magnetic flux patches at the core surface. Despite its successes in explaining the main morphological properties of Earth's magnetic field, self-consistent numerical modelling of the geodynamo has so far failed to reproduce this field variation pattern. Furthermore its magnetohydrodynamic origin, an essential pre-requisite for predicting the field evolution over the future decades, has been unclear. In this presentation we report on results obtained with numerical dynamos where we modify the treatment of mechanical boundary conditions, and impose heterogeneous thermochemical boundary control from either, or both, the inner-core boundary and the core-mantle boundary. In addition to presenting an Earth-like magnetic field morphology, these new numerical models also reproduce the morphology and localization of geomagnetic secular variation. In our models, the conservation of the angular momentum in the coupled inner-core / outer core / mantle system (the inner core and the mantle being held together by gravitational coupling) creates a westward columnar gyre circling around the inner core, which localises the secular variation in a narrow latitudinal band. An additional heterogeneous thermochemical boundary control distorts this gyre (the strongest distortion being obtained with inner core heterogeneous control) and localises the field changes in a hemispherical longitudinal sector. The two effects combine to recreate the observed localisation of geomagnetic secular variation in both longitude and latitude as a reult of a westward, columnar, eccentric gyre that penetrates throughout the outer core in a manner reminiscent of recent flow inversions. We also characterise the azimuthal drift of magnetic field structures using a Radon transform method, and find overall agreement between the model and geomagnetic data previously processed in the same way. Our results suggest that conservation of angular momentum and heterogeneous thermochemical boundary control in the coupled inner core / outer core / mantle system are central to understanding how Earth's magnetic field currently evolves.

Aubert, Julien; Finlay, Christopher; Fournier, Alexandre

2013-04-01

243

3D forecast of major geomagnetic storms  

NASA Astrophysics Data System (ADS)

A 3D analysis of coronal mass ejection events leading to major geomagnetic storms in solar cycle 24 has been carried out with help of STEREO and SOHO multipoint observations. The results from the CME modeling through application of the GCS and CAT methods were used as inner boundary conditions for the ENLIL simulations. Comparison of multipoint in situ CME measurements with the ENLIL results provides information on the 3D accuracy of the space weather forecasts and implications for future mission plannings near L5 or sub L1 orbits.

Bosman, Eckhard; Odstrcil, Dusan; Hesemann, Jonas; Milward, George; Venzmer, Malte; Volpes, Laura; Bothmer, Volker; Viereck, Rodney

2013-04-01

244

Geomagnetically Induced Currents: Progress and Issues  

NASA Astrophysics Data System (ADS)

Geomagnetically induced currents (GIC) are a hazard to conducting networks such as high-voltage power and pipeline grids. GIC have been known for decades to affect power systems at higher latitudes (e.g. Europe and North America), although more recently GIC have also been found to affect power networks at middle and lower latitudes. Mitigating the effects of GIC remains an issue for the power and pipeline industries and for governments concerned with the societal and economic implications. To understand, e.g. to model and predict, GIC in conducting grids needs expertise drawn from electrical engineering, geophysics and space weather science - a truly multi-disciplinary undertaking. In terms of geophysics and space physics, issues such as Earth structure (e.g. 3D versus 1D mantle and lithospheric conductivity structure), ocean/continent conductivity contrasts, ionospheric current systems and their variability and Sun-Earth magnetic interactions are all relevant. The start of solar cycle 24 provides an opportune time to consider the status of GIC research and to assess what new studies are required in geophysical modelling and in hazard analysis. What do we need to improve on to better specify/predict GIC flowing in power grids, from ‘up-stream' observations of coronal mass ejections through to geomagnetic field measurements made during magnetic storms? In this invited review we will consider aspects of a) Measurement: how do we measure GIC in grids; b) Analysis: how do measured GIC relate to geophysical and space physics data; c) Modelling: what methods exist for modelling GIC, again in relation to other data, and how accurate are models; and d) Prediction: how predictable are GIC and what are the implications for, e.g., the power industry and national governments. We will review the more recent developments in GIC and related geomagnetism and space weather science. We will outline what issues are widely believed to now be understood and what issues remain to be addressed. Throughout, the relationship between GIC studies and geomagnetism science in general will be stressed. Issues around providing GIC-related services to industry will also be mentioned and a proposed study of GIC in the pan-European high-voltage power grid will be described.

Thomson, Alan

2010-05-01

245

The solar drivers of geomagnetic disturbances during solar minimum  

Microsoft Academic Search

Recurrent high speed solar wind from coronal holes still existed around the solar minimum. Their effect on geomagnetic disturbances seems to be weak during this period. High speed solar wind sometimes overlapped with disturbances in association with coronal mass ejections (CMEs). However, a large number of geomagnetic disturbances (Dst<=-50nT) were associated with CMEs even around the solar minimum of the

Shinichi Watari; Takashi Watanabe

1998-01-01

246

The solar drivers of geomagnetic disturbances during solar minimum  

Microsoft Academic Search

Recurrent high speed solar wind from coronal holes still existed around the solar minimum. Their effect on geomagnetic disturbances seems to be weak during this period. High speed solar wind sometimes overlapped with disturbances in association with coronal mass ejections (CMEs). However, a large number of geomagnetic disturbances (Dst ? ?50 nT) were associated with CMEs even around the solar

Shinichi Watari; Takashi Watanabe

1998-01-01

247

European Project to Improve Models of Geomagnetically Induced Currents  

Microsoft Academic Search

Geomagnetically induced currents (GICs) from solar storms pose a risk to the operation of power transmission grids in Europe and across the globe. The European Risk from Geomagnetically Induced Currents (EURISGIC) project, which began in March 2011 and is supported by the Seventh Framework Programme of the European Union, seeks to mitigate this natural hazard by developing European capabilities for

Ari Viljanen

2011-01-01

248

Precursors of geomagnetic storms observed by the muon detector network  

Microsoft Academic Search

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

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

249

Automatic indexing  

SciTech Connect

Automatic indexing has been a critical technology as more full-text data becomes available online. The paper discusses issues for automatic indexing of different types of full-text and also presents a survey of much of the current research into new techniques for automatic indexing.

Harman, D.

1992-09-01

250

An association between geomagnetic activity and dream bizarreness.  

PubMed

Daily disturbances of the earth's magnetic field produce variations in geomagnetic activity (GMA) that are reportedly associated with widespread effects on human health and behaviour. Some of these effects could be mediated by an established influence of GMA on the secretion of melatonin. There is evidence from unrelated research that melatonin influences dream bizarreness, and it is hypothesised here that there is an association between GMA and dream bizarreness. Also reported is a preliminary test of this hypothesis, a case study in which the dreams recorded over 6.5 years by a young adult male were analysed. Reports of dreams from the second of two consecutive days of either low or high GMA (K index sum < or =6 or > or = 28) were self-rated for bizarreness on a 1-5 scale. Dreams from low GMA periods (n=69, median bizarreness=4) were found to be significantly more bizarre than dreams from high GMA periods (n=85, median bizarreness=3; p=0.006), supporting the hypothesised association between GMA and dream bizarreness. Studies with larger samples are needed to verify this association, and to determine the extent to which melatonin may be involved. Establishing that there is an association between GMA and dream bizarreness would have relevance for neurophysiological theories of dreaming, and for models of psychotic symptoms resembling bizarre dream events. PMID:19303220

Lipnicki, Darren M

2009-07-01

251

Geomagnetically induced currents in the New Zealand power network  

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

252

Continental scale modelling of geomagnetically induced currents  

NASA Astrophysics Data System (ADS)

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

Viljanen, Ari; Pirjola, Risto; Wik, Magnus; Ádám, Antal; Prácser, Ernö; Sakharov, Yaroslav; Katkalov, Juri

2012-09-01

253

Cosmic rays, geomagnetic field and climate changes  

NASA Astrophysics Data System (ADS)

The possibility of a connection between cosmic radiation and climate has intrigued scientists for the past several decades. The recent studies of Friis -Christensen and Svensmark has shown an observed variation of 3-4% of the global cloud cover between 1980 and 1995 that appeared to be directly correlated with the change in galactic cosmic radiation flux over the solar cycle. However, in studies of this type, not only the solar cycle modulation of cosmic radiation must be considered, but also the changes in the cosmic radiation impinging at the top of the atmosphere as a result of the long term evolution of the geomagnetic field. We present preliminary results of an on-going study of geomagnetic cutoff rigidities over a 400-year interval. These results show (1) the change in cutoff rigidity is sufficient large so that the change in cosmic radiation flux impacting the earth is approximately equal to the relative change in flux over a solar cycle, and (2) the changes in cutoff rigidity are non- uniform over the globe with both significant increases and decreases at mid-latitude locations.

Shea, M.; Smart, D.

254

Atmospheric helium and geomagnetic field reversals.  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

255

Nonrandom geomagnetic reversal times and geodynamo evolution  

NASA Astrophysics Data System (ADS)

Sherman's ?-test applied to the Geomagnetic Polarity Time Scale (GPTS) reveals that geomagnetic reversals in the Phanerozoic deviate substantially from random times. For 954 Phanerozoic reversals, ? exceeds the value expected for uniformly distributed random times by many standard deviations, due to three constant polarity superchrons and clustering of reversals in the Cenozoic C-sequence. Reversals are nearly periodic in several portions of the Mesozoic M-sequence, and during these times ? falls below random by several standard deviations, according to some chronologies. Polarity reversals in a convection-driven numerical dynamo with fixed control parameters have an overall ?-value that is slightly lower than uniformly random due to weak periodicity, whereas in a numerical dynamo with time-variable control parameters the combination of superchrons and reversal clusters dominates, yielding a large ?-value that is comparable to the GPTS. Sherman's test applied to shorter Phanerozoic reversal sequences reveals two geodynamo time scales: hundreds of millions of years represented by superchrons and reversal clusters that we attribute to time-dependent core-mantle thermal interaction, plus unexplained variations lasting tens of millions of years characterized by alternation between random and nearly periodic reversals.

Olson, Peter; Hinnov, Linda A.; Driscoll, Peter E.

2014-02-01

256

The science of geomagnetically induced currents  

NASA Astrophysics Data System (ADS)

Geomagnetically induced currents (GIC) phenomenon impacting long conductor systems on the ground can be considered as the end link of chain of complex physical processes comprising the Sun-Earth system. In this paper I briefly review the current status of our understanding of the physics of GIC and novel applications enabled by the new understanding. More specifically, I will demonstrate how we can follow the chain of physical processes from the solar corona down to the upper mantle of the Earth and to GIC. Further, I will show how state-of-the-art models enable predictive modeling of the entire chain of complex processes. The potential for severe societal consequences has been driving recent increasing interest in extreme GIC events. I will show how we have addressed the issue by generating 100-year GIC event scenarios. These scenarios are of substantial power grid industry interest and have been fed directly into further engineering analyses. I will review the results of our of 100-year geomagnetically induced current scenarios work and discuss some of the future directions in the field.

Pulkkinen, A.

2012-12-01

257

Survey data for geomagnetic field modelling  

NASA Technical Reports Server (NTRS)

The survey data discussed here are based on observations made relatively recently at points on land. A special subset of land survey data consists of those made at specially designated sites known as repeat stations. This class of data will be discussed in another part of this document (Barton, 1991b), so only the briefest of references will be made to repeat stations here. This discussion of 'ordinary' land survey data begins with a description of the spatial and temporal distributions of available survey data based on observations made since 1900. (The reason for this rather arbitrary choice of cut-off date is that this was the value used in the production of the computer file of magnetic survey data (land, sea, air, satellite, rocket) that is the primary source of data for geomagnetic main-field modeling). This is followed by a description of the various types of error to which these survey data are, or may be, subject and a discussion of the likely effects of such errors on field models produced from the data. Finally, there is a short section on the availability of geomagnetic survey data, which also describes how the data files are maintained.

Barraclough, D. R.; Macmillan, S.

1992-01-01

258

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

NASA Astrophysics Data System (ADS)

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.

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

2011-01-01

259

Towed Ocean Bottom Magnetometer to measure geomagnetic vector based on AMR sensor and SINS  

Microsoft Academic Search

The measurement of ocean bottom geomagnetic vector can provide geomagnetic vector diagram which reveals more detail of orebody distribution for ocean geologists. Former high-precision geomagnetic sensors meet difficulties when measuring geomagnetic vector and applying in ocean bottom. 3 component fluxgate magnetometer should improve its sensitivity and reliability. This paper described a new Ocean Bottom Magnetometer in towed operation to measure

Xueting Zhang; Jingbiao Liu; Ying Chen; Denv Huang

2008-01-01

260

Cutoff latitudes of solar protons during geomagnetic storms observed by NOAA/POES multi-satellites  

NASA Astrophysics Data System (ADS)

Solar energetic particles are injected into the Earth s magnetosphere but do not reach the inner magnetosphere connected to the low-latitudes by the field lines based on the well-known St o rmer theorem Geomagnetic cutoff rigidity and cutoff latitudes of energetic particles have been investigated in the past studies and are reported to be controlled by the geomagnetic activities Obayashi 1961 Fl u ckiger et al 1990 Leske et al 2001 Smart and Shea 2001 2005 Birch et al 2005 etc The polar orbiting NOAA POES satellites N15 N16 N17 and newly N18 have observed particles in a wide range of local time at altitudes of about 850 km The onboard radiation monitors detect solar energetic protons 16 - 500 MeV We have analyzed the combined data from the three or four satellites with time resolution of 1 5 hours which is near the orbital period of about 100 min in order to investigate local time dependences The observations show that the cutoff latitudes L -values of solar protons change accompanying with the phases of geomagnetic storms with local time dependence In particular during the big November 2004 storms with the minimum Dst of -380 nT the cutoff latitude in the nightside sector was about 5 degrees lower than those in the dayside sector The cutoff L -values averaged for all local time regions were correlated with variation of the Kp index better than the Dst index This fact indicates that the cutoff latitudes of 16 MeV protons are due to the magnetospheric structure affected by magnetospheric

Asai, K. T.; Nagatsuma, T.; Shimazu, H.; Hori, T.; Kitamura, K.; Miyoshi, Y.

261

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

SciTech Connect

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

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

1986-09-26

262

A new versatile method for modelling geomagnetic induction in pipelines  

NASA Astrophysics Data System (ADS)

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.

Boteler, D. H.

2013-04-01

263

Is motivation influenced by geomagnetic activity?  

PubMed

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

Starbuck, S; Cornélissen, G; Halberg, F

2002-01-01

264

Stress corrosion cracking susceptibility of friction stir welded AA7075–AA6056 dissimilar joint  

Microsoft Academic Search

Two aluminium alloys, AA7075 and AA6056, were friction stir welded, with the AA7075 alloy placed on the advancing side of the welding tool. Microstructural observations revealed the development of a recrystallised fine-grained weld nugget, with two different grain sizes, resulting from the two different base materials. Slow strain rate tensile (SSRT) tests in air have shown that the weld nugget

P. Bala Srinivasan; W. Dietzel; R. Zettler; J. F. dos Santos; V. Sivan

2005-01-01

265

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

PubMed Central

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

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

2008-01-01

266

Search for correlation between geomagnetic disturbances and mortality  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

267

Magnetospheric propagation of very long radio waves in geomagnetic waveguides  

NASA Astrophysics Data System (ADS)

The conditions of the propagation of VLF waves along geomagnetic waveguides in the earth magnetosphere are investigated theoretically, and the results are compared with satellite data. It is shown that VLF signals emitted from the earth surface are captured by geomagnetic waveguides at heights of approximately 500-2000 km above the earth surface when charged particle concentration in the waveguide exceeds that in the ambient plasma by at least 10 percent. A criterion for the capture of VLF signals by a geomagnetic waveguide is formulated. The results obtained are consistent with satellite measurements of VLF signals from ground transmitters.

Aksenov, V. I.; Moshkov, A. V.

268

Geomagnetic ground survey in Slovakia for the 2007.5 epoch  

Microsoft Academic Search

New geomagnetic ground survey was carried out in years 2006-2008. The survey was accomplished under fair geomagnetic-activity conditions during the minimum phase of a solar activity cycle No. 23. The measurements of the geomagnetic field were reduced to the 2007.5 epoch using magnetograms of the Hurbanovo Geomagnetic Obser- vatory. The distribution of the geomagnetic field over the territory of Slovakia

Peter DOLINSK ´; Fridrich VALACH

2009-01-01

269

Geomagnetic Effect Caused by 1908 Tunguska Event  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

270

Initial geomagnetic field model from MAGSAT  

NASA Technical Reports Server (NTRS)

Magsat data from magnetically quiet days were used to derive a thirteenth degree and order spherical harmonic geomagnetic field model, MGST(3/80). The model utilized both scalar and vector data and fit that data with standard deviations of 8, 52, 55 and 97 nT for the scalar magnitude, B sub r, B sub theta and B sub phi respectively. When compared with earlier models, the Earth's dipole moment continues to decrease at a rate of about 26 nT/year. Evaluation of earlier models with Magsat data shows that the scalar field at the Magsat epoch is best predicted by the POGO(2/72) model but that the AWC/75 and IGS/75 are better for predicting vector fields.

Langel, R. A.; Estes, R. H.; Mead, G. D.; Fabiano, E. B.; Lancaster, E. R.

1980-01-01

271

Plate Tectonic controls geomagnetic reversal frequency  

NASA Astrophysics Data System (ADS)

The discovery of the reversals of Earth's magnetic field and the description of plate tectonics are two of the main breakthroughs in geophysics in the 20th century. We claim that these two phenomena are correlated and that plate tectonics controls long-term changes in geomagnetic reversals frequency. More precisely, we show that geological periods characterized by an asymmetrical distribution of the continents with respect to the equator generate periods of high reversal frequency. We infer that the distribution and symmetry of mantle structures driving continental motions at the surface influence the equatorial symmetry of the flow within the core and thus changes the coupling between the dipolar and quadrupolar modes which controls the occurrence of reversals.

Petrelis, Francois; Besse, Jean; Valet, Jean-Pierre

2014-05-01

272

Protection against lightning on the geomagnetic observatory  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

273

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

NASA Astrophysics Data System (ADS)

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 (41°06´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.

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

2006-06-01

274

Was the Ancient Geomagnetic Field Dipolar?  

NASA Astrophysics Data System (ADS)

One of the most useful assumptions in paleomagnetism is that the time-averaged geomagnetic field is closely approximated by a geocentric axial dipole (GAD). This has been found to be true for at least the last 5 million years with the largest non-GAD contribution to the spherical harmonic expansion generally being of the order of 5%. For the more ancient past, it is difficult to test the GAD (or any other field) hypothesis owing to plate motions, rock deformation and accumulating problems of overprinting. Although most paleomagnetic studies make the implicit assumption of a GAD field, several recent studies have called the essential GAD nature of the ancient field into question and have suggested large (up to 20%) contributions of the axial octupolar term to the geocentric axial dipole in the spherical harmonic expansion even in the Cenozoic. In this paper, we develop a new statistical model for the geomagnetic field to diagnose directional dispersion resulting from sedimentary inclination error, a widespread process that plausibly explains many of the observed discrepancies from the GAD field hypothesis. We also present a methodology to correct the resulting persistent shallow bias. Application of this technique to one of the few published studies from the Cenozoic of Asia with adequate data shows that the reported discrepancies from a GAD field in this region are most probably due to sedimentary inclination error rather than a non-GAD field geometry or undetected crustal shortening. Although non-GAD fields cannot in general be strongly rejected (actually, only GAD is a well posed and testable, i.e., refutable, hypothesis), the principle of least astonishment requires us to consider plausible geological mechanisms such as sedimentary inclination error as the cause of persistent shallow bias prior to the very ``expensive" option of throwing out the GAD hypothesis.

Tauxe, L.; Kent, D. V.

2003-12-01

275

Historical records of the geomagnetic field  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

276

Angiotensin II type 1-Receptor Autoantibody (AT1-AA) -mediated pregnancy hypertension  

PubMed Central

Preeclampsia is the leading cause of maternal and fetal morbidity and mortality during pregnancy. Overall, 5–10% of all pregnancies worldwide develop preeclampsia. Women that developed preeclampsia and their children have an increased risk to suffer from cardiovascular diseases later in life. Autoantibodies can cause compilcations in pregnancy. In preeclampsia, agonistic autoantibodies against the angiotensin II type 1 receptor (AT1-AA) are described. They induce NADPH oxidase and the MAPK/ERK pathway leading to NF-?B and tissue factor activation. AT1-AA are detectable in animal models of preeclampsia and are responsible for elevation of soluble fms-related tyrosine kinase-1 (sFlt1) and soluble Endoglin (sEng), oxidative stress and endothelin-1, all of which are enhanced in preeclamptic women. AT1-AA can be detected in pregnancies with abnormal uterine perfusion and increased resistance index as well as in patients with systemic sclerosis and renal allograft rejection.

Herse, Florian; LaMarca, Babbette

2013-01-01

277

Statistical relations among substorm occurrence, geomagnetic pulsations and particle precipitation pulsations as seen at Indian Antarctic station Maitri  

NASA Astrophysics Data System (ADS)

Substorms at the auroral latitudes trigger a peculiar dynamics where a sharp depression in the AL index is observed along with an abrupt absorption in the cosmic noise due to ionospheric disturbances caused by high electron precipitation. However, such abrupt absorption may not always be seen during a substorm. Maitri (70°45' S, 11°45'E, geographic; 66°S, 53°21E, geomagnetic) is considered to be located at sub-auroral latitude and behaves as an auroral station during disturbed period. India has recently installed an Imaging Riometer at this sub auroral location. Using the data of cosmic noise intensity from Imaging riometer and the simultaneous magnetic field variation from digital flux gate magnetometer (DFM), a statistical study was performed in corroboration with the prevailing interplanetary conditions. Pi2 geomagnetic pulsations often accompanied by pulsations in particle precipitation flux have been thoroughly analyzed. Diurnal and seasonal patterns of such events were also statistically examined.

Behera, Jayanta Kumar; Singh, Anand Kumar; Pathan, B. M.; Sinha, Ashwini Kumar; Rawat, Rahul

2012-07-01

278

Dependence of low-latitude thermospheric wind on geomagnetic disturbance  

NASA Astrophysics Data System (ADS)

A statistical study has been made on variations in horizontal neutral wind velocity in the thermosphere at altitudes of ~250 km observed as Doppler shifts in 630 nm wavelength night airglow taken by the Fabry-Perot Interferometer (FPI) at Shigaraki (34.8N, 136.1E). The goal of the present study is to examine characteristics of the low-latitude thermospheric wind during geomagnetically active periods and address its role in evolving disturbance dynamo. For this purpose, unlike most of the past studies examining correlations with the Kp index, the present study focuses on correlations with the AE index which directly reflect the Joule heating in the polar region. On the basis of the long-term (2000-2009) FPI data with the filter for 630 nm, we firstly construct the quiet-time model of large-scale thermospheric wind above Shigaraki by sorting the data with very low AE activities by local time, season, and solar activity and then averaging them for each condition. Subtracting the quiet-time averages from the observed wind velocities, we conduct superposed epoch analyses on evolution of the residual wind velocity associated with auroral electrojet activities by referring to the AE index. As a result, the thermospheric wind velocity starts shifting westward and slightly southward 1-2 hours after AE rises from the quiet to high (~several hundreds of nT or greater) level. In particular, the westward shift of low latitude thermospheric wind becomes larger with increasing intensity and duration of AE activity. These changes of wind velocity with AE activities are basically consistent with the scenario of disturbance dynamo that the Joule heating caused by enhanced auroral electrojets in the polar region generates an additional, large-scale equatorward wind and the equatorward wind changes its direction to the west as it comes over to the low-mid. latitude region where the interaction of the westward neutral wind with ionospheric plasma drives a dynamo for an eastward current in the night-time equatorial ionosphere. Our detailed statistics also reveal that the westward shift is more evident in the post-midnight sector than pre-midnight and this local time asymmetry becomes clearer during summer. These spatial structures may be formed by mechanical interactions between the disturbance wind component and the global background wind primarily driven by the thermal tide caused by the Sun.

Hori, T.; Otsuka, Y.; Shiokawa, K.; Shinbori, A.

2013-12-01

279

AaIT: from neurotoxin to insecticide.  

PubMed

AaIT is a single chain neurotoxic polypeptide derived from the venom of the Buthid scorpion Androctonus australis Hector, composed of 70 amino acids cross-linked by four disulfide bridges. Its strict selectivity for insects has been documented by toxicity, electrophysiological and ligand receptor binding assays. These last have shown that various insect neuronal membranes possess a single class of non-interacting AaIT binding sites of high affinity (K(D) = 1-3(n)M) and low capacity (0.5-2.0 pmol/mg prot.). The fast excitatory paralysis induced by AaIT is a result of a presynaptic effect, namely the induction of a repetitive firing in the terminal branches of the insect's motor nerves resulting in a massive and uncoordinated stimulation of the respective skeletal muscles. The neuronal repetitive activity is attributed to an exclusive and specific perturbation of sodium conductance as a consequence of toxin binding to external loops of the insect voltage-dependent sodium channel and modification of its gating mechanism. From a strictly agrotechnical point of view AaIT involvement in plant protection has taken the following two complementary forms: firstly, as a factor for the genetic engineering of insect infective baculoviruses resulting in potent and selective bio-insecticides. The efficacy of the AaIT-expressing, recombinant baculovirus is attributed mainly to its ability to continuously provide and translocate the gene of the expressed toxin to the insect central nervous system; secondly, based on the pharmacological flexibility of the voltage-gated sodium channel, as a device for insecticide resistance management. Channel mutations conferring resistance to a given class of insecticidal agents (such as the KDR phenomenon) may greatly increase susceptibility to the AaIT expressing bioinsecticides. Thus the AaIT is a pharmacological tool for the study of insect neuronal excitability and chemical ecology and the development of new approaches to insect control. PMID:11086217

Zlotkin, E; Fishman, Y; Elazar, M

2000-01-01

280

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

NASA Astrophysics Data System (ADS)

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

Mertens, Christopher; Bilitza, Dieter; Xu, Xiaojing

2012-07-01

281

Solar activity and geomagnetic storms: The first 40 years  

SciTech Connect

This article is the first of a series of three that traces the evolution of present understanding of the relationship between solar and geomagnetic activity from the mid-19tb century to the present era.

Cliver, E.W.

1994-12-06

282

Geomagnetic Reversals and Crustal Spreading Rates during the Miocene.  

National Technical Information Service (NTIS)

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 ...

R. J. Blakely

1973-01-01

283

The disturbed geomagnetic field at European observatories. Sources and significance  

NASA Astrophysics Data System (ADS)

The disturbed geomagnetic field recorded at Earth's surface is given by the effects of electric current systems in the magnetosphere and ionosphere, as a result of the interaction of geomagnetic field with the solar wind and the interplanetary magnetic field. In this paper the geomagnetic disturbance recorded at European observatories has been investigated as regards its sources, for the time interval August 1-10, 2010, in which a moderate storm (Dstmin= -70 nT) occurred (August 3-4). The disturbance has been evidenced against the solar quiet daily variation, for each of the 29 observatories with minute data in the mentioned time interval. Data have been downloaded from the INTERMAGNET web page. The contribution of the magnetospheric ring current and of the auroral electrojet to the observed disturbance field in the X, Z, and D geomagnetic elements is discussed and the corresponding geographical distribution is presented.

Greculeasa, Razvan; Dobrica, Venera; Demetrescu, Crisan

2014-05-01

284

Transfer of the solar wind electromagnetic energy to magnetosphere during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Mutual orientation of interplanetary and terrestrial magnetic fields is important in reconnection model. However, reconnection rate is not less important parameter in the process. The rate depends on power of electromagnetic flux coming to regions of subsolar dayside magnetopause, cusp and polar caps where the reconnection is possible. Vector of Poyting P=[ExB] (where E, B is electric and magnetic fields in the solar wind) describing density of electromagnetic flux is used as a parameter in our study of geomagnetic storms. We use two independent components of the P vector: Pp and Pe describing value of the P flux coming to polar cap and to dayside magnetopause (Kuznetsova et al, 2006). Theorem of Poyting shows that supply of energy for a dissipation to be realized inside a volume is connected with external flux of Poyting vector. If a vector of P is directed to a some region, then a current described by dissipative term (E,J)¿0 should exist in the region (where expression in parenthesis is scalar product; J is vector of current density). And vice versa, if a vector of P is directed away from a some region, then a current with characteristics of dynamo (E,J)¡0 should exist. Based on our analysis of geomagnetic storms we show that direction of P to day-side magnetopause is necessary condition for a geomagnetic storm to develop. Dst-index during main phase follows by Pe-component without delay determined by 1-hour averages of the solar wind data measured at the Earth orbit for period 1964-2005. When the P vector is directed away from day-side magnetopause, recovery phase begins. The result points to the fact that the energy rate coming to magnetosphere during the storms nearly equals to dissipation rate into magnetosphere (energy storage is not essential). In addition, variation of Bz component in GSM c.s. is shifted to 1 hour before variation Dst-index (based on the same 1-hour averages). At last we analyze the highly anomalous magnetic storm occurred on 21-22 January 2005 (minimum Dst= -105 nT). The storm main phase developed during northward magnetic field and after the IMF was northward during 7 hours. Based on our analysis we suggest a possible mechanism for the storm main phase: reconnection of geomagnetic field with northward and azimuthal IMF in cusps and polar regions of both hemispheres (that leads to intensive convection between hemispheres). Power of the solar wind supplied to the magnetosphere during the anomalous storm is 5 101 2W att.

Kuznetsova, Tamara; Laptukhov, Alexej; Petrov, Valery

285

Geomagnetic Variations of Near-polar Regions and Human Health  

NASA Astrophysics Data System (ADS)

In polar region geomagnetic variations play active role to non-linear tectonic processes. This analysis is based on spatial-time spectral representation of geomagnetic variation and wave migration transformation. Many perturbations in electromagnetic fields may because by external factors (e.g. magnetic storms, ionosphere anomalies and other phenomena related to solar activity) "trigging" tectonic processes but having no direct relation to the processes of their preparation. Geophysical processes are responsible for perturbations in Earth's rotation and orientation on wide range of time-scale, from less than a day of millions of years. The geological structure of some sites of Earth's crust promotes occurrence of wave guides a number of geophysical fields (acoustic, seismic, electromagnetic), usually of transportation of acoustic, seismic, electromagnetic energy in Earth's crust are coincide spatially. During last 250 mln years Arctic Segment has been developing as an autonomous region with circumpolar zonality of geomagnetic fields, and mass - and-energy transfer in its bowlers as well as shitting of lithospheric plates and expansion of ocean are caused by rotation forces under of expanding planet. The dynamic structure of the geomagnetic variations may be characteriz ed by the variations of the order-chaos state. The order manifest itself in the rhythmic change of the medium state. Analysis of amplitude and phase of geomagnetic variations can be information on ecological state of regions. Geomagnetic variations is intrincically a multiscale process in time and space. One of the most important features of geomagnetic variations is multicyclic character, whish predetermined both extent and character of geomagnetic show, and specific features. Recently, there are collected many facts, show dependence between the processes in the Earth's biosphere, the elements of it, gelio- geo- physical and meteorological factors. The recent experimental data gives us opportunity to conclude, that geomagnetic and geoelectric fields produced the biological effect, that is correlated with solar activity variations. The result of many years investigation of geomagnetic variations on near-polar territory, the authors found the facts of sharp increasing of intensity of the short wave' variations near the points of fault crossing. Analysis of character of geomagnetic variations can give information on the alleged effects of electromagnetic fields on human health. Spectral analysis shows rhythms with periods of 98, 105, 125, 130, 145, 160, 170, 180, 200, 235, 250, 270, 330, 395 sec. The rhythms with period of 98 -180 sec. coincide with rhythms of human cardiovascular activity. This concurrence entail occurrence of a magnetic resonance.

Tchistova, Z. B.; Kutinov, Y. G.

286

Geomagnetic variation anomalies in north-western Italy  

Microsoft Academic Search

A preliminary geomagnetic variation data analysis has been made in the Piedmont-Ligurian area in north-western Italy. Data were collected by means of two instruments: an Askania portable variograph and a LaCour fixed station operated in the Roburent geomagnetic observatory. The portable variograph has been moved to several locations in north-western Italy. Parkinson vectors were drawn for 8, 20 and 60

Emanuele Bozzo; Antonio Meloni

1989-01-01

287

Historically Large Geomagnetic Storms and Potential Electric Power Grid Impacts  

Microsoft Academic Search

While recent work has been done to examine the possible Dst Intensity of historically large geomagnetic storms, the impacts caused to modern day electric power grids from these storms occurs due to rapid rate-of-change of regional geomagnetic fields which in most cases are driven by large ionospheric electrojet current intensifications. These temporally and spatially dynamic disturbance morphologies are not well-characterized

J. G. Kappenman

2004-01-01

288

The Geomagnetic Field and Radiation in Near-Earth Orbits  

NASA Technical Reports Server (NTRS)

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.

Heirtzler, J. R.

1999-01-01

289

Atmospheric temperature responses to solar irradiance and geomagnetic activity  

Microsoft Academic Search

The relative effects of solar irradiance and geomagnetic activity on the atmospheric temperature anomalies (Ta) are examined from the monthly to interdecadal timescales. Geomagnetic Ap (Ap) signals are found primarily in the stratosphere, while the solar F10.7-cm radio flux (Fs) signals are found in both the stratosphere and troposphere. In the troposphere, 0.1–0.4 K increases in Ta are associated with

Hua Lu; Martin J. Jarvis; Hans-F. Graf; Peter C. Young; Richard B. Horne

2007-01-01

290

Effect of Ageing on Mechanical Properties of AA 6060 and AA 6063.  

National Technical Information Service (NTIS)

The influence of various natural and artificial aging conditions after extrusion have been investigated on AA 6060 and AA 6063 aluminum alloys with regard to the Mg2Si particle development during these treatments and their effect on hardness, strength and...

Z. Stanislaw

1995-01-01

291

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

NASA Astrophysics Data System (ADS)

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

Malandraki, Olga

2013-04-01

292

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

NASA Astrophysics Data System (ADS)

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.

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

293

Are migrating raptors guided by a geomagnetic compass?  

USGS Publications Warehouse

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

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

2006-01-01

294

The solar wind at the turn of the century  

Microsoft Academic Search

Comparisons of geomagnetic activity and sunspot number over the past hundred years are studied with particular reference to the pattern of the minima from cycle to cycle. Values are given for the solar-cycle variations of yearly averages of sunspot number and aa index of geomagnetic activity for those cycles where the yearly mean aa index increases nearly linearly in time,

J. Feynman; N. U. Crooker

1978-01-01

295

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

Microsoft Academic Search

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

Samara Lloyd Rice; J. Scott Tonigan

2011-01-01

296

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

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

Singer, B. S.

2013-12-01

297

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

PubMed

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

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

2013-01-01

298

Influence of solar flux variations and geomagnetic activity on the atomic oxygendiurnal emissions in the high atmosphere of the Earth  

NASA Astrophysics Data System (ADS)

A statistical analysis over 5 years of WINDII measurements of the 630.0 nm dayglow and of the thermospheric layer of the 557.7 nm dayglow is performed. The behaviour of the volume emission rate (VER) of those oxygen emissions is presented, as a function of the main geophysical parameters that characterize them : the solar zenith angle (SZA), the solar activity, and the geomagnetic activity.The influence of the solar activity is quantified using two different proxies : the f10.7 decimetric index and the MgII index. A better representativity of the MgII index was found when describing the relations between the oxygen emissions and the solar EUV activity, showed by better correlations between the VER and MgII than between the VER and the f10.7 proxy.The influence of the geomagnetic activity is also quantified.Together with this statistical study, we show that our 1-D fluid/kinetic model (TRANSCAR) is able to appropriately reproduce the WINDII measurements all along the satellite orbit, even if small dissimilarities are noticed and discussed in terms of ability of the f10.7 index to represent the solar EUV thermosphere input.

Culot, F.; Lathuillère, C.; Lilensten, J.; Witasse, O.

299

Discrete Scale Invariance in Geomagnetic Data  

NASA Astrophysics Data System (ADS)

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.

Jonkers, A.

2005-12-01

300

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

ERIC Educational Resources Information Center

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…

PFEFFER, J. ALAN

301

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

302

The influence of geomagnetic and solar variabilities on lower thermosphere density  

NASA Astrophysics Data System (ADS)

Atmospheric density measurements near 200 km from the Satellite Electrostatic Triaxial Accelerometer (SETA) experiment are analyzed for geomagnetic and solar flux variability effects. Data from the SETA experiment, onboard two satellites, are available for the periods of May to November 1982, and July 1983 to March 1984. The data utilized the span /+/-79.5° latitude, and are available for both day (1030 LT) and night (2230 LT). Annual and semiannual density variations are removed and regression analyses are performed on the residuals using a series of lagged 3 h Kp indices to determine and remove geomagnetic fluctuations. Densities are found to increase by as much as 134% in response to an increase in the Kp index from 1 to 6. Monthly curves are generated for the Kp regression coefficients to delineate seasonal-latitudinal and day//night dependences, which reflect the effects of mean meridional advection of disturbances from high to low latitudes. Further analyses are performed comparing measured densities with MSISE-90 predictions. Results show that the model is able to capture many of the prominent features, but does not fully predict the level of variability for the individual disturbance periods analyzed. After the geomagnetic effects are removed, the residual densities are interpreted in terms of solar flux variability. The daily-averaged SETA density residuals are strongly correlated with long-term solar flux variability, and exhibit a much greater dependence on the 27-day solar rotation period than MSISE-90 predictions. Variations in residual density of the order of 10-20% occur in association with day-to-day and 27-day solar flux variations. The MSIS model does not accurately predict the magnitude of these short-term density variations in response to solar activity.

Rhoden, E. A.; Forbes, J. M.; Marcos, F. A.

2000-07-01

303

Results of geomagnetic observations in Central Africa by Portuguese explorers during 1877 1885  

NASA Astrophysics Data System (ADS)

In this short contribution, geomagnetic measurements in Central Africa made by Capelo and Ivens - two Portuguese explorers - during the years 1877 and 1885 are provided. We show the scarce number of geomagnetic observation in Africa compiled until now. These Portuguese explorers performed a considerable amount of measurements of geomagnetic declination (44 measurements), inclination (50) and horizontal component (50) of the geomagnetic field. We compared the results attained by these keen observers with those derived from the global geomagnetic model by Jackson et al. [Jackson, A., Jonkers, A.,Walker, M., 2000. Four centuries of geomagnetic secular variation from historical records. Philos. Trans. R. Soc. Lond. 358, 957-990].

Vaquero, José M.; Trigo, Ricardo M.

2006-08-01

304

Major Geomagnetic Storms in Solar Cycle 24  

NASA Astrophysics Data System (ADS)

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 7 August 2013). 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 few 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. The characteristics of such challenging, not-so-fast yet geoeffective CME events (such as their coronal signatures and interactions with surrounding solar wind structure(s), etc) will be examined in detail, with the goal of extracting common and telltale features, if any, of these CMEs that distinguish them from CMEs in a similar category.

Zheng, Y.

2013-12-01

305

The Livingston Island Geomagnetic and Ionospheric Observatory  

NASA Astrophysics Data System (ADS)

The Ebre Observatory Institute manages a geophysical observatory installed at the Spanish Antarctic Station (SAS) Juan Carlos I. It was set up in 1995 and it has been updated yearly by our team throughout several projects carried out since then. Nowadays, it hosts a magnetic station providing 1-second data of the 3 components (X, Y, Z) and the total force (F) during the entire year, and an ionospheric station providing vertical and oblique data during austral summer. This observatory has provided long data series of high scientific value from this remote region of the Earth. They have been used to improve the knowledge of the climate and weather behavior of the geomagnetic field and ionosphere in the area, and to model and expand the capacity of data transmission. This contribution aims to present a brief review of the instruments installed at SAS, the research results obtained from their data, and the developing activities under the current project. Finally, future perspectives are outlined with regard to adapting our geophysical observatory to the evolving needs of observatory practice.

Altadill, David; Marsal, Santiago; Blanch, Estefania; Miquel Torta, J.; Quintana-Seguí, Pere; Germán Solé, J.; Cid, Òscar; José Curto, Juan; Ibáñez, Miguel; Segarra, Antoni; Lluís Pijoan, Joan; Juan, Juan Miguel

2014-05-01

306

Equatorial airglow and the ionospheric geomagnetic anomaly.  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

307

The geomagnetic dynamo - Elementary energetics and thermodynamics  

NASA Astrophysics Data System (ADS)

The basic energetics and thermodynamics of dynamo models of the geomagnetic field are examined in a general nonmathematical review. The properties of the earth core are summarized; the powers needed to drive the dynamo and account for the observable field, an unobserved 10-nT toroidal field, or a 50-nT field are estimated as 200 MW, 10 GW, and 250 GW, respectively; the impossibility of obtaining such powers from rotation (and precession) is demonstrated; and thermal and gravitational sources are considered in detail. Consideration is given to the release of up to 10 TW of heat by K-40 decay (assuming K is concentrated in the core), heat release of up to 2 TW by cooling of the core over 4 Gyr, and the release of about 600 GW of gravitational potential energy through compositional convection from the freezing out at the surface of the inner core (moving mass toward the center). The latter mechanism is considered the most plausible at present.

Lowes, F. J.

1984-12-01

308

Geomagnetic main field modeling with DMSP  

NASA Astrophysics Data System (ADS)

The Defense Meteorological Satellite Program (DMSP) launches and maintains a network of satellites to monitor the meteorological, oceanographic, and solar-terrestrial physics environments. In the past decade, geomagnetic field modelers have focused much attention on magnetic measurements from missions such as CHAMP, Ørsted, and SAC-C. With the completion of the CHAMP mission in 2010, there has been a multiyear gap in satellite-based vector magnetic field measurements available for main field modeling. In this study, we calibrate the special sensor magnetometer instrument on board DMSP to create a data set suitable for main field modeling. These vector field measurements are calibrated to compute instrument timing shifts, scale factors, offsets, and nonorthogonality angles of the fluxgate magnetometer cores. Euler angles are then computed to determine the orientation of the vector magnetometer with respect to a local coordinate system. We fit a degree 15 main field model to the data set and compare with the World Magnetic Model and Ørsted scalar measurements. We call this model DMSP-MAG-1, and its coefficients and software are available for download at http://geomag.org/models/dmsp.html. Our results indicate that the DMSP data set will be a valuable source for main field modeling for the years between CHAMP and the recently launched Swarm mission.

Alken, P.; Maus, S.; Lühr, H.; Redmon, R. J.; Rich, F.; Bowman, B.; O'Malley, S. M.

2014-05-01

309

The Effectiveness of the AAS REU Program  

Microsoft Academic Search

In an attempt to address the particular needs of astronomy faculty and undergraduate students, in 1991 the Education Office of the American Astronomical Society approached the National Science Foundation with a unique proposal for funding through the Research Experiences for Undergraduates program. The goals of the AAS program were to \\

M. K. Hemenway; P. B. Boyce; R. W. Milkey

1996-01-01

310

The AAS Visiting Professor Programs: Three Anniversaries  

Microsoft Academic Search

The AAS Program of Visiting Professors was started in 1958 with three astronomers as lecturers. They were Paul Merrill (Mt. Wilson and Palomar Observatories), Seth Nicholson (Mt. Wilson and Palomar Observatories) and Harlow Shapley (Harvard College Observatory). The program was run by a Committee on Visiting Professors from 1958 through 1963. The program was funded by grants from the National

A. G. Davis Philip

2003-01-01

311

Photoinduced changes in the optical properties of obliquely deposited aAs 2S 3 thin films  

Microsoft Academic Search

The photoinduced changes in the optical properties of obliquely deposited a-As2S3 thin films are followed. It is established that the increase of the refractive index and absorption coefficient as a result of illumination is highest in the sample prepared at 70° vapour incidence angle. In addition, the refractive index dispersion has been analyzed according to the Wemple–Didomenico single oscillator model

J Dikova; P Sharlandjiev; P Gushterova; Tz Babeva

2002-01-01

312

Geochemistry Index  

NSDL National Science Digital Library

This site is the index of a book used in a geochemistry course taught by W. M. White at Cornell University. There are 15 chapters and a table of contents available. All of the chapters are large PDF files and take some time to download. Figures and exercises accompany the text.

White, William M.; Department Of Earth And Atmospheric Sciences, Cornell U.

313

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

Microsoft Academic Search

The corrosion performance of laser-melted AA 2014-T6 and AA 2024-T351 alloys, using a 2kW CW CO2 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

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

2005-01-01

314

The effect of homogenisation treatment on cold deformations of AA 2014 and AA 6063 alloys  

Microsoft Academic Search

The effect of homogenisation treatment conditions on cold deformations of aluminium alloys AA 2014 and AA 6063 was studied by the torsion test. These aluminium alloys were homogenised at 320, 370, 420 and 470°C for 8h. The torsion tests were performed on as-cast and homogenised alloys at the room temperature and strain rate of 2×10?2s?1. The hardness were measured the

Y. Totik; R. Sadeler; I. Kaymaz; M. Gavgali

2004-01-01

315

Work-hardening stages of AA1070 and AA6060 after severe plastic deformation  

Microsoft Academic Search

Based on the concept of work-hardening for fcc metals, the commercially pure aluminum AA1070 (soft annealed) and the aluminum\\u000a alloy AA6060 (peak-aged) were investigated. Equal-channel angular pressing (ECAP) was used to introduce very high strains\\u000a and an ultrafine-grained microstructure. Compression tests were performed in a wide range of strain rates between 10?4 and 103 s?1 subsequently. The results show that strain

Matthias Hockauf; Lothar W. Meyer

2010-01-01

316

Microstructural characterization of dissimilar friction stir welds between AA2219 and AA5083  

Microsoft Academic Search

Fusion welding of dissimilar aluminum alloys is very challenging. In the present work, Al-Cu alloy AA2219-T87 was friction\\u000a stir welded to Al-Mg alloy AA5083-H321. Weld microstructures, hardness, and tensile properties were evaluated in as-welded\\u000a condition. Microstructural studies revealed that the nugget region was primarily composed of alloy 2219, which was placed\\u000a on the advancing side. No significant mixing of the

J. J. S. Dilip; M. Koilraj; V. Sundareswaran; G. D. Janaki Ram; S. R. Koteswara Rao

2010-01-01

317

Some Geomagnetic and Ionospheric Effects in Antarctica Prior to Storm Sudden Commencements.  

National Technical Information Service (NTIS)

Ionospheric height changes, blackout conditions, and geomagnetic activity for Antarctica in the relatively quiet times (geomagnetically) before storm sudden commencements are investigated. The principal results give evidence for 24-hourly periodicities in...

G. G. Bowman

1966-01-01

318

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

Federal Register 2010, 2011, 2012, 2013

...by geomagnetic disturbances. The conference will explore the risks and impacts from geomagnetically induced currents to transformers and other equipment on the Bulk-Power System, as well as, options for addressing or mitigating the...

2012-04-13

319

77 FR 24952 - Staff Technical Conference on Geomagnetic Disturbances to the Bulk-Power System; Technical...  

Federal Register 2010, 2011, 2012, 2013

...by geomagnetic disturbances. The conference will explore the risks and impacts from geomagnetically induced currents to transformers and other equipment on the Bulk-Power System, as well as, options for addressing or mitigating the...

2012-04-26

320

Recursive Analysis of the Geomagnetic Vector Field Calculo Recursivo Do Vetor Campo Geomagnetico.  

National Technical Information Service (NTIS)

A computer program to evaluate the geomagnetic field components in geographic reference systems by using the Gauss model of order and degree 10 and with the International Geomagnetic Reference Field Coefficients 1980 is presented. The algorithm is recursi...

R. V. D. F. Lopes V. Carrara H. K. Kuga V. M. Demedeiros

1983-01-01

321

Kristian Birkeland's pioneering investigations of geomagnetic disturbances  

NASA Astrophysics Data System (ADS)

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.

Egeland, A.; Burke, W. J.

2010-04-01

322

Airport geomagnetic surveys in the United States  

USGS Publications Warehouse

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

Berarducci, A.

2006-01-01

323

Dynamical similarity of geomagnetic field reversals.  

PubMed

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

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

2012-10-01

324

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/

1986-01-01

325

Synergistic activity between Bacillus thuringiensis Cry6Aa and Cry55Aa toxins against Meloidogyne incognita.  

PubMed

Plant-parasitic nematodes are the most destructive group of plant pathogens worldwide and are extremely challenging to control. Some Bacillus thuringiensis crystal proteins are highly toxic to the plant-parasitic nematode Meloidogyne incognita. In this study, the nematicidal crystal proteins Cry6Aa, Cry5Ba and Cry55Aa were tested against M. incognita to select the best toxin combination for its management. The results showed that a combination of Cry6Aa and Cry55Aa showed significant synergistic toxicity against M. incognita, and the highest synergistic effect (five times the expected toxicity of the two toxins calculated from their separate toxicities) was observed when they were combined in a 1:1 ratio. Furthermore, ligand blot analyses of the interaction between total proteins of M. incognita and the three toxins showed many different signal bands, indicating that there is a range of host proteins with which the toxins can interact. One explanation of the observed synergism is that the toxins damage the host in diverse ways, and they may thus act cooperatively and thereby show greater toxicity in combination. Our discovery provides an effective strategy for controlling M. incognita by using a combination of Cry6Aa and Cry55Aa. PMID:21923640

Peng, Donghai; Chai, Lujun; Wang, Fenshan; Zhang, Fengjuan; Ruan, Lifang; Sun, Ming

2011-11-01

326

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

NASA Astrophysics Data System (ADS)

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.

Tobiska, W. Kent

327

Solar coronal holes as sources of recurrent geomagnetic disturbances  

NASA Technical Reports Server (NTRS)

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

Neupert, W. M.; Pizzo, V.

1974-01-01

328

Midlatitude cooling caused by geomagnetic field minimum during polarity reversal  

PubMed Central

The climatic effects of cloud formation induced by galactic cosmic rays (CRs) has recently become a topic of much discussion. The CR–cloud connection suggests that variations in geomagnetic field intensity could change climate through modulation of CR flux. This hypothesis, however, is not well-tested using robust geological evidence. Here we present paleoclimate and paleoenvironment records of five interglacial periods that include two geomagnetic polarity reversals. Marine oxygen isotope stages 19 and 31 contain both anomalous cooling intervals during the sea-level highstands and the Matuyama–Brunhes and Lower Jaramillo reversals, respectively. This contrasts strongly with the typical interglacial climate that has the temperature maximum at the sea-level peak. The cooling occurred when the field intensity dropped to <40% of its present value, for which we estimate >40% increase in CR flux. The climate warmed rapidly when field intensity recovered. We suggest that geomagnetic field intensity can influence global climate through the modulation of CR flux.

Kitaba, Ikuko; Hyodo, Masayuki; Katoh, Shigehiro; Dettman, David L.; Sato, Hiroshi

2013-01-01

329

The geomagnetic elements in Denmark 1928-1980  

NASA Astrophysics Data System (ADS)

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

Hansen, H. A.

330

Report of geomagnetic pulsation indices for space weather applications  

USGS Publications Warehouse

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.

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

2013-01-01

331

Geomagnetic observations on tristan da cunha, south atlantic ocean  

USGS Publications Warehouse

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).

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

2009-01-01

332

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

NASA Technical Reports Server (NTRS)

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.

Hardy, D. A.

1974-01-01

333

The irregular variations of the external geomagnetic field from Intermagnet data  

NASA Astrophysics Data System (ADS)

The INTERMAGNET program publishes each year a CD-ROM containing homogeneous series from a number of magnetic observatories (76 in 1999). These series are definitive one-minute values of the three components of the geomagnetic field. We transform these series using a simple nonlinear analysis tool able to characterize the activity of a signal, and we obtain a remarkably simple activity field, whose space and time variables separate over a large part of the Earth. The time function is almost identical for all observatories, and might be interpreted as an activity index. The "almost stationary" field geometry exhibits a dipole-like structure everywhere except in high latitudes.

Bellanger, E.; Anad, F.; Jean-Mouël, L. L.; Mandea, M.

2003-04-01

334

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

NASA Astrophysics Data System (ADS)

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.

Jacobsen, Knut Stanley; Schäfer, Sebastian

2012-08-01

335

A.A. and Counseling: Conflict or Opportunity?  

ERIC Educational Resources Information Center

The greatest focus in alcoholism treatment research today is matching client to treatment. Consistent with this research direction, this paper describes a survey completed by members of Alcoholic Anonymous (AA) regarding their assessment of AA as a treatment. It looks at the self-reported behaviors of AA members and compares these actions with…

Benson, Robert K.

336

Micropulsacoes Geomagneticas Em Santa Maria-RS (Geomagnetic Micropulsations at Santa Maria).  

National Technical Information Service (NTIS)

This work presents a study on geomagnetic micropulsations at low latitudes (less than 35 deg), using data obtained at the Santa Maria Geomagnetic Station RS, Brazil. This station is located at geomagnetic coordinates 19, 1 deg S, 15, 6 deg L; L equals 1, ...

A. Zanandrea

1994-01-01

337

Morphology in the total electron content under geomagnetic disturbed conditions: results from global ionosphere maps  

Microsoft Academic Search

Using 8-year global ionosphere maps (GIMs) of TEC products from the Jet Propulsion Laboratory (JPL), we make a statistical study on the morphology of the global ionospheric behaviors with respect to the geomagnetic disturbances. Results show that the behaviors of TEC during geomagnetic storm present clear seasonal and local time variations under geomagnetic control in a similar way as those

Zhao Biqiang; Wan Weixing; Liu Libo; Mao Tian

2007-01-01

338

Multistation measurements of Pc5 geomagnetic power amplitudes at high latitudes  

Microsoft Academic Search

Geomagnetic data from four Antarctic stations, located at -80 corrected geomagnetic (CGM) latitude, have been analyzed. The magnetic local time (MLT) occurrence distributions and seasonal dependence of geomagnetic power levels in the Pc5 frequency band are studied. It is found that the pulsation power can be significantly influenced by the MLT location of the station at the specific UT time

Paola Ballatore; Louis J. Lanzerotti; Carol G. Maclennan

1998-01-01

339

Studies of ULF Power at Pc4 and Pc5 Frequencies at the Highest Geomagnetic Latitudes  

Microsoft Academic Search

Two Automatic Geomagnetic Observatory stations, AGOs P5 and P6, were purposely established on opposite sides of the nominal geomagnetic dipole on the Antarctic polar cap in order to compare magnetospheric phenomena during local day and local night conditions over relatively small spatial scales deep in the geomagnetic polar regions. While simulataneous data from all AGOs are often not available due

M. Waldstein; L. J. Lanzerotti; C. G. Maclennan

2002-01-01

340

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

NASA Astrophysics Data System (ADS)

High-resolution records of beryllium (10Be) production and relative paleointensity have been obtained across the Matuyama-Brunhes (M-B) reversal from the equatorial Indian Ocean (Maldives area). Both magnetic and geochemical analyses were performed from the same discrete samples to avoid any artificial depth offset. The authigenic 10Be concentrations were normalized with respect to 9Be in order to correct for potential environmental effects, while the relative paleointensity was derived from the remanent magnetization intensity after accounting for changes in magnetic concentration within the sediment. The relative paleointensity and the 10Be/9Be records are both characterized by large deviations, which culminate in the middle of the reversal. In contrast to most previous studies, and despite relative high deposition rate (4.7 cm/ka), we observed a perfect synchronism between the 10Be/9Be peak, the lowest value of relative paleointensity and the switch in direction, which indicates that bioturbation and post-depositional processes did not affect the magnetic record. This leaves no ambiguity for the stratigraphic position of the reversal located within Marine Isotopic Stage 19 as revealed by the planktonic ?18O record from the same core. The magnetic data depict a two-phase process with a precursory event preceding the rapid polarity switch, while only the second phase is present in the 10Be record, similarly to other low latitude records from the Indonesian area. Using an orbitally-tuned age model, we obtain an age of 772 ka±5 ka for the middle of the transition, while the precursory event occurred almost 20 ka before. We believe that the bimodal distribution emerging from the compilations of the ages of the M-B reversal results from the succession of these two events. Microtektites from the Australasian impact were found at 0.6 m below the transition (790 ka±5 ka B.P.) and confirm that this large event occurred 12 ka prior to the polarity transition. The distribution of tektite abundance was used to deconvolve the 10Be/9Be signal. The results confirm that the beryllium changes are concentrated during the transitional period, thus likely in presence of a multipolar geomagnetic field (or in the vicinity of a geomagnetic pole) that favored the penetration of cosmic rays and consequently increased the 10Be production. The absence of 10Be during the precursor indicates that the present site and the Indonesian ones were far away from a geomagnetic pole and that interlatitudinal atmospheric mixing was limited. The geomagnetic pole positions above the Indonesian sites during the precursor would thus be incompatible with the corresponding inclined dipolar field during this period, and suggest the dominance of low-degree harmonics.

Valet, Jean-Pierre; Bassinot, Franck; Bouilloux, Alexandra; Bourlès, Didier; Nomade, Sébastien; Guillou, Valéry; Lopes, Fernand; Thouveny, Nicolas; Dewilde, Fabien

2014-07-01

341

GEOMAGNETIC REVERSALS DRIVEN BY ABRUPT SEA LEVEL CHANGES  

SciTech Connect

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.

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

1986-10-01

342

Secular Variations of the Geomagnetic Field in Europe  

NASA Astrophysics Data System (ADS)

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.

Sas-Uhrynowski, A.; Welker, E.

2009-09-01

343

Composition signatures in ion injections and its dependence on geomagnetic conditions  

NASA Astrophysics Data System (ADS)

Ion composition in substorm injections are investigated in detail by using data obtained from the magnetospheric ion composition spectrometer (MICS) on board the Combined Release and Radiation Effects Satellite (CRRES). A total of 398 injection events are identified from 4 February to 10 October, 1991. It is found that the flux enhancements of O+ ions in the "with-oxygen" injections (O+ ions occupy more than 20% of the total energy density) are attributed to the flux intensifications of high-energy (E/q ? 100 keV/e) ions. In contrast, the flux of H+ and He++ ions in the "without-oxygen" injections (O+ ions are less than 20% total energy density) are enhanced by the intensification of lower energy H+ and He++ (around 50 keV/e) ions. Statistical results also demonstrate that the abundance of O+ ions in an injection strongly depends on the geomagnetic activity. Without-oxygen events take place most probably in relatively weak geomagnetic activity conditions (Dst index is around -50 nT and Kp is around 4). The averaged fractional energy density of O+ ions increases roughly linearly with Kp index. All injections are found to be rich of oxygen ions during the strong magnetic storms (Dst < -100 nT). The present study indicates that the ionospheric oxygen ions are energized more readily during the storm conditions. When the near-Earth reconnection occurs and expands from the central plasma sheet to the plasma sheet boundary layer or even to the lobe region, much more ionosphere origin O+ ions could participate and be energized in the magnetospheric dynamic process. This leads to a with-oxygen injection in the inner magnetosphere. As to the without-oxygen injection, it seems that only preexisting oxygen ions in the near-Earth plasma sheet are accelerated and become a part of the injected ions, thus a rather low abundance of O+ ions can be observed.

Fu, S. Y.; Zong, Q. G.; Fritz, T. A.; Pu, Z. Y.; Wilken, B.

2002-10-01

344

Neural net forecasting for geomagnetic activity  

Microsoft Academic Search

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.

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

1993-01-01

345

The effect of RRA on the strength and SCC resistance on AA7050 and AA7150 aluminium alloys  

Microsoft Academic Search

The effect of retrogression and re-aging (RRA) on the strength and stress corrosion cracking (SCC) performance was evaluated in AA7050 and AA7150 aluminum alloys. Samples from extruded profiles, at their original condition (T77511 for AA7150 and T76511 for AA7050), were solution heat treated and aged at 120°C for 1440min (T6 condition). After that, retrogression was performed at 200°C for times

A OLIVEIRAJR; M. C de Barros; K. R Cardoso; D. N Travessa

2004-01-01

346

Data Behind the Figures in AAS Journals  

NASA Astrophysics Data System (ADS)

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.

Biemesderfer, Chris

2013-01-01

347

Introducing the AAS Astronomy Ambassadors Program  

NASA Astrophysics Data System (ADS)

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.

Gurton, S.; Fienberg, R. T.; Fraknoi, A.; Prather, E. E.

2013-04-01

348

AAS Services on the World Wide Web  

NASA Astrophysics Data System (ADS)

The AAS initiated its WWW service in mid-1993 and since that time these have expanded dramatically, both in usage and in content. The content has expanded in response to member interest and now includes a wide range of information regarding Society governance, membership, and activities, e.g. meetings. Each of the Society's Divisions also provides information through the WWW and the AAS homepage provides links to these. The AAS pages also includes pointers to other sites of interest in astronomy and related areas such as education and public policy. The versatility provided by WWW services has been so attractive that other means of electronic access to the Society's information have declined in usage, almost to the vanishing point. In this presentation we will describe the services currently provided and offer the usage statistics to show the growth of popularity of this form over the last couple of years. We will also indicate some of the future possibilities for using WWW services to further supplement the Societies general purpose publications. We will also suggest some opportunities for providing two-way communication with the membership through the features of the WWW, especially those offered by new security features.

Johnson, J. M.; Kovalsky, D.

1995-12-01

349

A statistical analysis of low frequency geomagnetic field pulsations at two Antarctic geomagnetic observatories in the polar cap region  

NASA Astrophysics Data System (ADS)

The aim of this study is to investigate the characteristics of low frequency (˜0.5-5 mHz) geomagnetic field fluctuations as recorded at two Antarctic stations within the polar cap: the Italian observatory Mario Zucchelli Station (TNB) and the French-Italian observatory Dome C (DMC) in order to investigate the spatial extension and propagation characteristics of the phenomena observed at very high latitude. The stations have approximately the same geographic latitude, but a very different corrected geomagnetic latitude, being DMC close to the geomagnetic pole and TNB closer to the auroral oval. Our study focused on power spectra, coherence and phase difference between low frequency fluctuations analyzing the horizontal H component measured during the entire year 2006. The fluctuation power behavior during the day can be explained according to the positions of the stations with respect to the polar cap; indeed in the dayside sector it is higher in the cusp region, while in the nightside sector it is higher close to the geomagnetic pole. Furthermore the study of coherent fluctuations, focusing on their phase difference, indicated that the propagation direction within the cap is variable during the day: in the dayside and nightside regions it is from the auroral oval toward the geomagnetic pole, while in the magnetic local morning and afternoon sectors it is from the geomagnetic pole toward the dawn-dusk meridian. Finally the analysis of two individual pulsation events, consisting of short duration wave packets, is shown; it confirms the statistical considerations on the propagation direction and allows to estimate the wave number and apparent phase velocity, whose values are of the order of 3-4 and 30-15 km/s, respectively.

Pietrolungo, M.; Lepidi, S.; Cafarella, L.; Di Mauro, D.

2013-09-01

350

Mandated AA attendance for recidivist drinking drivers: policy issues.  

PubMed

Mandates for recidivist drinking drivers to attend AA meetings raise concerns about whether AA referral practices could have an adverse impact on both alcohol problems and traffic safety, whether routine and unregulated referrals to AA may prove detrimental to AA as an organization, and over ethical issues and possible loss of civil liberties. Similar issues arise in criminal justice and other agencies' handling of a variety of situations beyond the DUI arena. As a result institutions mandating involvement in mutual aid programs such as AA, and a variety of treatment settings, should adopt cautious referral practices, support rigorous research and create and evaluate targeted programs and integrated services. PMID:9374010

Speiglman, R

1997-09-01

351

High cycle fatigue of AA6082 and AA6063 aluminum extrusions  

NASA Astrophysics Data System (ADS)

The high cycle fatigue behavior of hollow extruded AA6082 and AA6063 aluminum extrusions has been studied. Hollow extruded aluminum profiles can be processed into intricate shapes, and may be suitable replacements for fatigue critical automotive applications requiring reduced weight. There are several features inherent in hollow aluminum extrusions, such as seam welds, charge welds, microstructural variations and die lines. The effects of such extrusion variables on high cycle fatigue properties were studied by taking specimens from an actual car bumper extrusion. It appears that extrusion die lines create large anisotropy differences in fatigue properties, while welds themselves have little effect on fatigue lives. Removal of die lines greatly increased fatigue properties of AA6082 specimens taken transverse to the extrusion direction. Without die lines, anisotropy in fatigue properties between AA6082 specimens taken longitudinal and transverse to the extrusion direction, was significantly reduced, and properties associated with the orientation of the microstructure appears to be isotropic. A fibrous microstructure for AA6082 specimens showed great improvements in fatigue behavior. The effects of elevated temperatures and exposure of specimens to NaCl solutions was also studied. Exposure to the salt solution greatly reduced the fatigue lives of specimens, while elevated temperatures showed more moderate reductions in fatigue lives.

Nanninga, Nicholas E.

352

Neural net forecasting for geomagnetic activity  

NASA Technical Reports Server (NTRS)

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).

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

1993-01-01

353

Predicting the Size of Sunspot Cycle 24 on the Basis of Single- and Bi-Variate Geomagnetic Precursor Methods  

NASA Technical Reports Server (NTRS)

Examined are single- and bi-variate geomagnetic precursors for predicting the maximum amplitude (RM) of a sunspot cycle several years in advance. The best single-variate fit is one based on the average of the ap index 36 mo prior to cycle minimum occurrence (E(Rm)), having a coefficient of correlation (r) equal to 0.97 and a standard error of estimate (se) equal to 9.3. Presuming cycle 24 not to be a statistical outlier and its minimum in March 2008, the fit suggests cycle 24 s RM to be about 69 +/- 20 (the 90% prediction interval). The weighted mean prediction of 11 statistically important single-variate fits is 116 +/- 34. The best bi-variate fit is one based on the maximum and minimum values of the 12-mma of the ap index; i.e., APM# and APm*, where # means the value post-E(RM) for the preceding cycle and * means the value in the vicinity of cycle minimum, having r = 0.98 and se = 8.2. It predicts cycle 24 s RM to be about 92 +/- 27. The weighted mean prediction of 22 statistically important bi-variate fits is 112 32. Thus, cycle 24's RM is expected to lie somewhere within the range of about 82 to 144. Also examined are the late-cycle 23 behaviors of geomagnetic indices and solar wind velocity in comparison to the mean behaviors of cycles 2023 and the geomagnetic indices of cycle 14 (RM = 64.2), the weakest sunspot cycle of the modern era.

Wilson, Robert M.; Hathaway, David H.

2009-01-01

354

Possible mechanisms relating asteroid impacts to extinctions and geomagnetic reversals  

Microsoft Academic Search

Mechanical processes occurring between the crust and the interior of the Earth, which overcome the difficulty in relating sources of the geomagnetic field dipolar component and shallow asteroid impact effects, and which help to explain some points about the causes of the Earth's magnetic field and its reversals, are discussed.

D. J. R. Nordemann

1982-01-01

355

The Equatorial Airglow and the Ionospheric Geomagnetic Anomaly.  

National Technical Information Service (NTIS)

OGO D observations of OI (6300A) emissions reveal a global pattern in the equatorial airglow undetected from the ground-based observations. The post sunset emission rate of OI is generally asymmetrical with respect to the geomagnetic equator and shows no ...

S. Chandra E. I. Reed B. E. Troy J. E. Blamont

1972-01-01

356

Wavelet Statistical Analysis of Low-Latitude Geomagnetic Measurements  

Microsoft Academic Search

Following previous works by our group (Papa et al., JASTP, 2006), where we analyzed a series of records acquired at the Vassouras National Geomagnetic Observatory in Brazil for the month of October 2000, we introduced a wavelet analysis for the same type of data and for other periods. It is well known that wavelets allow a more detailed study in

A. R. Papa; A. F. Akel

2009-01-01

357

Evidence for a Geomagnetic Wake at 500 Earth Radii  

Microsoft Academic Search

A comparison of the Explorer 35 solar wind plasma data with the data obtained by Pioneer 8 during a pass through the tail region at a geocentric distance of 500 Rr suggests the presence of a geomagnetic wake. The wake was characterized by a reduced density or increased temperature or both and by an almost unmodified flow speed as compared

G. L. Siscoe; F. L. Scarf; D. S. Intriligator; J. H. Wolfe; J. H. Binsack; H. S. Bridge; V. M. Vasyliunas

1970-01-01

358

Particle acceleration from reconnection in the geomagnetic tail  

SciTech Connect

Acceleration of charged particles in the near geomagnetic tail, associated with a dynamic magnetic reconnection process, was investigated by a combined effort of data analysis, using Los Alamos data from geosynchronous orbit, MHD modeling of the dynamic evolution of the magnetotail, and test particle tracing in the electric and magnetic fields obtained from the MHD simulation.

Birn, J.; Borovsky, J.E.; Thomsen, M.F.; McComas, D.J.; Reeves, G.D.; Belian, R.D. [Los Alamos National Lab., NM (United States); Hesse, M. [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center; Schindler, K. [Ruhr-Univ., Bochum (Germany)

1997-08-01

359

Eects of geomagnetic storms on the ionosphere and atmosphere  

Microsoft Academic Search

A geomagnetic storm is a complex process: its various features act at dierent heights. In the F2 layer the midlatitude eect is basically an ionospheric response to storm-induced changes in the neutral atmosphere, which are primarily a consequence of a strong Joule heating in the auroral thermosphere. At lower heights the role of ionization and photochemical processes increases due to

A. D. Danilov; J. Lastovicka

2001-01-01

360

Construction of the Normal Geomagnetic Field by Means of Computation.  

National Technical Information Service (NTIS)

In the practice of both Soviet and other foreign geophysicists, two types of normal geomagnetic fields are necessary for the separation of one or another class of anomaly. These two types are the field of the uniformly magnetized sphere (TO), and the fiel...

B. D. Vints V. I. Pochtarev

1967-01-01

361

Antarctic F2 Region Disturbances Associated with Geomagnetic Storms.  

National Technical Information Service (NTIS)

Variations of the electron density in the Antarctic F2 region associated with individual geomagnetic storms are analyzed and the cause is studied. Analysis is done on the basis of winter data when the solar radiation responsible for the production of ioni...

T. Sato

1964-01-01

362

Interplanetary field and plasma during initial phase of geomagnetic storms  

NASA Technical Reports Server (NTRS)

Twenty-three geomagnetic storm events during 1966 to 1970 were studied by using simultaneous interplanetary magnetic field and plasma parameters. Explorer 33 and 35 field and plasma data were analyzed on large-scale (hourly) and small-scale (3 min.) during the time interval coincident with the initial phase of the geomagnetic storms. The solar-ecliptic Bz component turns southward at the end of the initial phase, thus triggering the main phase decrease in Dst geomagnetic field. The By component also shows large fluctuations along with Bz. When there are no clear changes in the Bz component, the By shows abrupt changes at the main phase onset. On the small-scale, behavior of the magnetic field and electric field were studied in detail for the three events; it is found that the field fluctuations in By, Bz and Ey and Ez are present in the initial phase. In the large-scale, the behavior field remains quiet because the small-scale variations are averaged out. It appears that large as well as small time scale fluctuations in the interplanetary field and plasma help to alter the internal electromagnetic state of the magnetosphere so that a ring current could causing a geomagnetic storm decrease.

Patel, V. L.; Wiskerchen, M. J.

1975-01-01

363

CIRA Solar Irradiances and Solar\\/Geomagnetic Indices  

Microsoft Academic Search

Solar and geomagnetic inputs are required for use in empirical thermospheric density models. The constituent species in the thermosphere absorb spectrally resolved solar irradiances from soft X-ray (XUV) to Far Ultraviolet (FUV) wavelengths which deposit their energy at varying optical depths. In the high latitude regions, Joule heating and particle precipitation contribute secondary heating, which can be transported to lower

W. Kent Tobiska

2008-01-01

364

Response of the thermosphere and ionosphere to geomagnetic storms  

Microsoft Academic Search

Four numerical simulations have been performed, at equinox, using a coupled thermosphere-ionosphere model, to illustrate the response of the upper atmosphere to geomagnetic storms. The storms are characterized by an increase in magnetospheric energy input at high latitude for a 12-hour period; each storm commences at a different universal time (UT). The initial response at high latitude is that Joule

T. J. Fuller-Rowell; M. V. Codrescu; R. J. Moffett; S. Quegan

1994-01-01

365

Surface electric fields for North America during historical geomagnetic storms  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

366

First results from the first Croatian geomagnetic observatory  

NASA Astrophysics Data System (ADS)

The first Croatian geomagnetic observatory was established in the area of the Nature Park Lonjsko Polje, after a century of sporadic efforts originating from the proposals of Andrija Mohorovicic. The location was chosen after exhaustive surveys of possible sites. It is located far enough from sources of civilization noise, and was found to be an area without magnetic anomalies and with a low field gradient. The construction of the observatory buildings was completed in the autumn of 2011. The furnishing and installation of instruments and test measurements were completed by the beginning of summer 2012, ever since we have continuous recordings of the geomagnetic elements. In the beginning of December 2012 the fluxgate magnetometer LEMI-035 (H,D,Z orientation) has been installed under the framework of the PLASMON project in cooperation with the Tihany Observatory (Hungary). Permanent data of high quality from our observatory will contribute to the monitoring of the Earth's magnetic field on the regional and global levels, thus enabling further development of geomagnetism in Croatia through collaboration with scientists from the other countries, participation in the international projects, eventual membership in the International Real-time Magnetic Observatory Network (INTERMAGNET), etc. The field elements for the epoch 2012,75 and the baselines are presented together with highlights of some recorded geomagnetic events so far. Furthermore, the comparison between the variation data recorded by the dIdD and the fluxgate LEMI-035 magnetometer is presented.

Mandic, Igor; Herak, Davorka; Heilig, Balazs

2013-04-01

367

Geomagnetically Induced Currents in European High-Voltage Power Systems  

Microsoft Academic Search

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

Risto J. Pirjola; David H. Boteler

2006-01-01

368

Shape of the Geomagnetic Field Solar Wind Boundary  

Microsoft Academic Search

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

Gilbert D. Mead; David B. Beard

1964-01-01

369

Cosmic rays flux and geomagnetic field variations at midlatitudes  

NASA Astrophysics Data System (ADS)

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.

Morozova, Anna; Ribeiro, Paulo; Tragaldabas collaboration Team

2014-05-01

370

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

371

Study on underwater navigation system based on geomagnetic match technique  

Microsoft Academic Search

Underwater vehicle navigation technique is one of the important issues to the development and application of the long-range underwater vehicle technology. In order to meet the concealment of underwater navigation, we present a kind of independent underwater navigation system based on geomagnetic match technique in this paper. Firstly, we introduce the composition of the system, the work principles and functions

Jianhu Zhao; Shengping Wang; Aixue Wang

2009-01-01

372

Solar Radio Bursts, Proton Events and Geomagnetic Activity.  

National Technical Information Service (NTIS)

The relationships between type II, type IV, microwave bursts and geomagnetic activity have been studied using data from various observatories compiled in the Solar-Geophysical Data over the period 1968-1982. It is found that type II bursts follow the tren...

S. S. Degaonkar

1984-01-01

373

The 1870 space weather event: Geomagnetic and auroral records  

Microsoft Academic Search

The great solar storm that took place on 24–25 October 1870 is not well known and has been almost absent from previous studies. In this work, a large amount of information that was registered at the time is compiled and analyzed, including early geomagnetic data and several comprehensive descriptions of the auroras observed during these two nights. These descriptions reveal

J. M. Vaquero; M. A. Valente; R. M. Trigo; P. Ribeiro; M. C. Gallego

2008-01-01

374

New insights on geomagnetic storms from observations and modeling  

SciTech Connect

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.

Jordanova, Vania K [Los Alamos National Laboratory

2009-01-01

375

Evidence suggesting extremely rapid field variation during a geomagnetic reversal  

Microsoft Academic Search

Large, systematic variations in direction of high-temperature remanence as a function of vertical position occur in a basalt flow from the Miocene volcanic sequence at Steens Mountain, Oregon, that has provided a detailed record of geomagnetic reversal. These may have been caused by an impulsive change in the transitional field as the flow cooled during the reversal. If this is

Robert S. Coe; Michel Prevot

1989-01-01

376

A link between geomagnetic reversals and events and glaciations  

Microsoft Academic Search

The apparent duration of geomagnetic polarity events in Arctic Ocean sediments is much longer than in sediments from lower latitudes. In fact, while the remanence of Brunhes age sediment cores from the Yermak Plateau at 82°N is fully reversed for ? 30% of their lengths [1], the events often evade detection in many other continuously deposited sediments. For example, the

Horst-Ulrich Worm

1997-01-01

377

Statistical Tools for the Analysis of Geomagnetic Reversal Sequences  

Microsoft Academic Search

Previous investigations of geomagnetic reversal sequences have shown that a nonstationary gamma distribution provides a good description of the intervals between reversals. The general problems of parameter estimation and testing for differences between the statistical properties of reverse and normal polarity sequences are considered. A likelihood method is suggested to overcome the problems of nonstationarity and the consequent dependence of

P. L. McFadden

1984-01-01

378

ENERGETIC ELECTRON FLUXES IN THE TAI OF THE GEOMAGNETIC FIELD  

Microsoft Academic Search

Fluxes of energetic electrons up to 107 cm - sec -x above 45 key frequently appear in the tail of the geomagnetic tail out to distances of 31.5 earth radii. They characteristically occur as isolated patches, not directly attached to other particle distributions around the earth. It is shown that these particles are usually injected into regions of space at

K. A. Anderson

1965-01-01

379

An inversion of geomagnetic deep sounding data using simulated annealing  

Microsoft Academic Search

A maiden attempt on the use of the global optimization technique of Simulated Annealing (S.A.) inversion to model the conductivity structure derived from the geomagnetic deep sounding data of NW India is reported here. The location of the proposed model is now in agreement with the theory, since the conductive bodies are centered exactly below the center of the response

S. N. Prasad

1999-01-01

380

Influence of the geomagnetic activity on the human functional systems  

Microsoft Academic Search

Changes in the normal functioning of the central nervous system, vegetative nervous system, cardiovascular system and cognitive performance may be enhanced by significant variations of the geomagnetic field (GMF) elements. Human physiological, psychophysiological and psychical processes and sensory abilities may be substantially influenced by these changes. The interest in revealing the correlation between the variations of the GMF and the

Irina Stoilova; Thomas Zdravev

381

Trapped anomalous cosmic rays near the geomagnetic cutoff  

Microsoft Academic Search

Observations made with the mass spectrometer telescope (MAST) instrument aboard the SAMPEX spacecraft have previously been used to map the belt of geomagnetically trapped anomalous cosmic rays at L  2. Here we use the heavy ion large telescope (HILT) instrument to extend these observations to lower energies, closer to the peak of the interplanetary spectrum at 1 AU, for

M. D. Looper; J. B. Blake; B. Klecker; D. Hovestadt

1996-01-01

382

Secular-invariant relationships among internal geomagnetic field coefficients  

Microsoft Academic Search

Some features of the secular variation of the geomagnetic field are examined. Contours encircling constant magnetic flux (third adiabatic invariant), corresponding to a shell of field lines in secular motion, reveal a general westward drift that is longitude and latitude dependent (with minima in the north Pacific and south Atlantic areas). Some invariant relationships appear among the field coefficients in

J. G. Roederer

1974-01-01

383

Evidence for current sheet acceleration in the geomagnetic tail  

Microsoft Academic Search

The existence of the current sheet and the dawn to dusk electric field in the geomagnetic tail implies there is particle energization in the tail current sheet of the order 2--10% of the total solar wind energy incident upon the dayside magnetopause. In this paper we determine that ion acceleration in a current sheet with a small magnetic field across

L. R. Lyons; T. W. Speiser

1982-01-01

384

Possible helio-geomagnetic activity influence on cardiological cases  

NASA Astrophysics Data System (ADS)

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.

Katsavrias, Christos

385

Observations of geomagnetically induced currents in the Australian power network  

NASA Astrophysics Data System (ADS)

such as pipelines and power networks at low-middle latitude regions have historically been considered relatively immune to geomagnetically induced currents (GICs). Over the past decade there have been an increasing number of investigations into the impact of GICs in long grounded conductors at these latitudes. The Australian region power network spans thousands of kilometers from low to middle latitudes. The approaching maximum of solar cycle 24 and recent findings of studies into power networks located at similar latitudes have stimulated the Australian power industry to better understand this phenomenon in their region. As a result, a pilot study to compare space weather activity with in situ GIC monitors at strategic locations within the power network was initiated. This paper provides some results from the first of these operational GIC monitors during a modest geomagnetic storm, showing the first observational evidence of space weather well correlated with GICs measured in the Australian power network. Transformer neutral currents show a high degree of similarity with the geoelectric field derived from the closest available geomagnetic observatory. Current maxima of 4-5 amperes were observed in association with geoelectric field values of ~0.06-0.07 volts per kilometer. This paper also discusses the GIC measurements obtained during this storm in terms of the space weather drivers and the considerably larger geoelectric field values anticipated during larger geomagnetic storms.

Marshall, R. A.; Gorniak, H.; van der Walt, T.; Waters, C. L.; Sciffer, M. D.; Miller, M.; Dalzell, M.; Daly, T.; Pouferis, G.; Hesse, G.; Wilkinson, P.

2013-01-01

386

Geomagnetic induction effects in ground-based systems  

Microsoft Academic Search

Plasma physics processes, whose ultimate origin is the Sun, exist in the Earth's magnetosphere and ionosphere and can produce effects which are detrimental to the operation of technological systems associated with long conductors deployed on the Earth's surface. Geomagnetic fluctuations produced by such plasma processes can cause disturbances and disruptions in cable communication systems, electrical power distribution systems, and long

L. J. Lanzerotti

1983-01-01

387

On the Possibilities of Predicting Geomagnetic Secular Variation with Geodynamo Modeling  

NASA Technical Reports Server (NTRS)

We use our MoSST core dynamics model and geomagnetic field at the core-mantle boundary (CMB) continued downward from surface observations to investigate possibilities of geomagnetic data assimilation, so that model results and current geomagnetic observations can be used to predict geomagnetic secular variation in future. As the first attempt, we apply data insertion technique to examine evolution of the model solution that is modified by geomagnetic input. Our study demonstrate that, with a single data insertion, large-scale poloidal magnetic field obtained from subsequent numerical simulation evolves similarly to the observed geomagnetic variation, regardless of the initial choice of the model solution (so long it is a well developed numerical solution). The model solution diverges on the time scales on the order of 60 years, similar to the time scales of the torsional oscillations in the Earth's core. Our numerical test shows that geomagnetic data assimilation is promising with our MoSST model.

Kuang, Wei-Jia; Tangborn, Andrew; Sabaka, Terrance

2004-01-01

388

Geomagnetic Storms and Acute Myocardial Infarctions Morbidity in Middle Latitudes  

NASA Astrophysics Data System (ADS)

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.

Dimitrova, S.; Babayev, E. S.; Mustafa, F. R.; Stoilova, I.; Taseva, T.; Georgieva, K.

2009-12-01

389

Physical Meaning of the Equinoctial Effect for Seasonal Variation of Geomagnetic Activity  

NASA Astrophysics Data System (ADS)

The general tendency for magnetic disturbances to be more stormy at equinoxes than at solstices has been recognised for more than 150 years. To explain the seasonal variation three principal hypotheses have been proposed; the axial hypothesis (Cortie, 1912), the equinoctial hypothesis (Bartels, 1932; McIntosh, 1959), and the Russell and McPherron (RM) hypothesis (Russell and McPherron, 1973). The RM hypothesis, which is based on the recognition that the magnetic field in the solar equatorial plane tends to have the largest southward component in geocentric solar magnetospheric (GSM) coordinates in early April and October, has been largely accepted for many years. However, recent studies have confirmed that the RM effect accounts for only a subordinate proportion of the seasonal variation of geomagnetic activity, and that the larger part of the phenomenon is attributable to the equinoctial effect in which the angle between the solar wind flow and the dipole axis of the Earth plays an essential role (Cliver, Kamide and Ling, 2000; Cliver, Kamide, Ling and Yokoyama, 2001; O'Brien and McPherron, 2002). In this paper physical meaning of the equinoctial effect is investigated based on the data of three-hourly am index and solar wind parameters acquired by the ACE satellite. The am indices are well correlated with BsVxVx, where Bs is the southward component of the interplanetary magnetic field (IMF) and Vx is the solar wind velocity in the sun-earth direction. It is found, however, that the am - BsVxVx relation depends on the range of VxVx: The am in higher ranges of VxVx tends to be larger than am in lower ranges of VxVx for both equinoctial and solstitial epochs for the same value of BsVxVx. Using the data sets of the same VxVx range, it is shown that distribution of points in the am - BsVxVx diagram at the solstitial epochs overlaps with that at the equinoctial epochs and the average am values in each BsVxVx bin in solstitial epochs are almost equal to those in equinoctial epochs, if VxVx for each point at solstices are reduced to VxVx sin (c) where c is the geomagnetic colatitude of the sub-solar point. This finding indicates that the emergence of the geomagnetic disturbance is regulated by the component of the solar wind velocity perpendicular to the dipole axis of the geomagnetic field. The magnitude of the perpendicular velocity component varies seasonally even if the solar wind velocity remains constant. This appears to be the long-missed key factor causing the equinoctial effect. It is interesting to note that both the RM and equinoctial effects are related to seasonal changes in the efficiency of solar wind - magnetosphere coupling caused by changes in the geometric configuration between the sun and the geomagnetic dipole field, one in relation to Bs of the IMF, and the other in relation to the component of solar wind velocity perpendicular to the dipole axis.

Yoshida, A.

2008-12-01

390

Real-time Neural Network predictions of geomagnetic activity indices  

NASA Astrophysics Data System (ADS)

The Boyle potential or the Boyle Index (BI), ? (kV)=10-4 (V/(km/s))2 + 11.7 (B/nT) sin3(?/2), is an empirically-derived formula that can characterize the Earth's polar cap potential, which is readily derivable in real time using the solar wind data from ACE (Advanced Composition Explorer). The BI has a simplistic form that utilizes a non-magnetic "viscous" and a magnetic "merging" component to characterize the magnetospheric behavior in response to the solar wind. We have investigated its correlation with two of conventional geomagnetic activity indices in Kp and the AE index. We have shown that the logarithms of both 3-hr and 1-hr averages of the BI correlate well with the subsequent Kp: Kp = 8.93 log10(BI) - 12.55 along with 1-hr BI correlating with the subsequent log10(AE): log10(AE) = 1.78 log10(BI) - 3.6. We have developed a new set of algorithms based on Artificial Neural Networks (ANNs) suitable for short term space weather forecasts with an enhanced lead-time and better accuracy in predicting Kp and AE over some leading models; the algorithms omit the time history of its targets to utilize only the solar wind data. Inputs to our ANN models benefit from the BI and its proven record as a forecasting parameter since its initiation in October, 2003. We have also performed time-sensitivity tests using cross-correlation analysis to demonstrate that our models are as efficient as those that incorporates the time history of the target indices in their inputs. Our algorithms can predict the upcoming full 3-hr Kp, purely from the solar wind data and achieve a linear correlation coefficient of 0.840, which means that it predicts the upcoming Kp value on average to within 1.3 step, which is approximately the resolution of the real-time Kp estimate. Our success in predicting Kp during a recent unexpected event (22 July ’09) is shown in the figure. Also, when predicting an equivalent "one hour Kp'', the correlation coefficient is 0.86, meaning on average a prediction within 0.99 step. Our model is also successful in predicting AE in its original 1-hr cadence format to achieve a linear correlation of 0.83. Our real-time AE prediction model is currently being developed. However, live results of the BI plot and Kp prediction can be obtained from http://space.rice.edu/ISTP/wind.htmlspacalrt system will receive email alerts whenever the value of the predicted Kp reaches 6 or higher, or when the 10-minute BI exceeds 200 kV.

Bala, R.; Reiff, P. H.

2009-12-01

391

Geomagnetic field intensity and inclination records from the Hawaiian long basaltic cores: geomagnetic implications  

NASA Astrophysics Data System (ADS)

In the long basaltic cores drilled in the Big Island of Hawaii, the sub-horizontal orientation of the flows and their regular accumulation with time, which makes the continuity in time almost comparable with sediments, provides an excellent opportunity to obtain a detailed record of the absolute intensity and inclination of the geomagnetic field from a sequence of lava flows. Here, we report new paleointensity (Thellier and Thellier) and inclination determinations obtained from the analysis of 370 samples from 130 flows in the subaerial part of HSDP2. These new results are combined with previous results obtained from the other long basaltic cores in Hawaii (HSDP1, SOH4 and SOH1) all selected using a set of stringent paleointensity selection criteria (PICRIT-03). In a first step the Sharp and Renne age model was used for correlation of the records. In a second step correlation was refined using some characteristic features of the paleomagnetic records themselves (HSDP 1 and HSDP 2 in particular), which led to a slight modification of the Sharp and Renne age model. The age model was further improved by correlation with the sedimentary SINT-800 record. The results are consistent between these independent records, over the different time intervals where they overlap. This allows construction of the first accurate lava record of absolute intensity and inclination at Hawaii which overlap for almost 75% of this time interval these different records overlap, the results are very consistent and allow to construct an accurate lava record of absolute geomagnetic field intensity and inclination at Hawaii for the last 420 kyr based on at least two independent records over almost. The VADM undergoes large oscillations between about 3 and 16 10^22 A.m*2 with an average values of about 8 10^22 A m^2. When the values corresponding to recognized excursional periods are omitted, the inclination is on the average 29.6°, i.e. about 6° shallower than the GAD value. These results will be compared with the prediction of dynamo solutions based on lower mantle seismic tomography of Davies et al.(2008)

Laj, C. E.; Kissel, C.; Davies, C.; Gubbins, D.

2009-12-01

392

Enhancement of solar wind low-energy energetic particles as precursor of geomagnetic disturbance in operational geomagnetic forecast  

Microsoft Academic Search

A study of the relationship between solar wind low-energy energetic particles using data from the Electron, Proton, and Alpha Monitor (EPAM) onboard the Advanced Compositional Explorer spacecraft (ACE) and geomagnetic activity using data from Canadian magnetic observatories in Canada's polar cap, auroral zone, and subauroral zone was carried out for a period spanning 1997-2005. Full halo coronal mass ejections (CMEs)

H.-L. Lam

2009-01-01

393

Cytochrome aa3 from Nitrosomonas europaea.  

PubMed

Cytochrome c oxidase has been purified from the ammonia oxidizing chemoautotroph Nitrosomonas europaea by ion-exchange chromatography in the presence of Triton X-100. The enzyme has absorption maxima at 420 and 592 nm in the resting state and at 444 and 598 nm in the dithionite-reduced form; optical extinction coefficient (598 nm minus 640 nm) = 21.9 cm-1 nM-1. The enzyme has approximately 11 nmol of heme a and approximately 11 nmol of copper per mg of protein (Lowry procedure). There appear to be three subunits (approximate molecular weights 50,800, 38,400, and 35,500), two heme groups (a and a3), and two copper atoms per minimal unit. The EPR spectra of the resting and partially reduced enzyme are remarkably similar to the corresponding spectra of the mitochondrial cytochrome aa3-type oxidase. Although the enzyme had been previously classified as "cytochrome a1" on the basis of its ferrous alpha absorption maximum (598 nm), its metal content and EPR spectral properties clearly show that it is better classified as a cytochrome aa3. Neither the data reported here nor a review of the literature supports the existence of cytochrome a1 as an entity discrete from cytochrome aa3. The purified enzyme is reduced rapidly by ferrous horse heart cytochrome c or cytochrome c-554 from N. europaea, but not with cytochrome c-552 from N. europaea. The identity of the natural electron donor is as yet unestablished. With horse heart cytochrome c as electron donor, the purified enzyme could account for a significant portion of the terminal oxidase activity in vivo. PMID:3023381

Dispirito, A A; Lipscomb, J D; Hooper, A B

1986-12-25

394

AAS Special Session: Policy Making in Astronomy  

NASA Astrophysics Data System (ADS)

The professional astronomical community today is more diverse than at any time in its history. Individuals participating in creative research programs can be found in a wide range of positions. This type of diversity, which mixes research, education, and service (e.g. contract) work, represents the strength of contemporary astronomy. While recognizing the unavoidable reductions in funding and restructuring of organizations like NASA, it is imperative that the significance of the current diversity be considered during these processes. Creative ideas are one of the cornerstones of quality research, and they can originate anywhere. Consequently, it is essential that adequate research resources remain available for free and open competition by all astronomers. Our goal in this session is to bring together officials from the AAS, NASA, and the NSF to discuss how the policy and decision making process operates and whether it should be changed to better serve the general needs of the professional astronomical community. Examples of the issues we believe are important include: In establishing new policy, how can the needs of the average research astronomer be better addressed? How could input from such astronomers be provided to those who craft NASA/NSF policy? How can/should the AAS serve as an interface between policy/decision making bodies and its membership? Should the AAS membership become more actively/effectively involved in the decision making process and, if so, how? More information on this session and related issues can be found at the Association of Research Astronomers Home Page: http://www.phy.vill.edu/astro/faculty/ara/ara_home.htm

Cardelli, J. A.; Massa, D.

1995-12-01

395

Impact resistance of AA6005 panels  

NASA Astrophysics Data System (ADS)

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.

Clausen, A. H.; Borvik, T.; Hopperstad, O. S.; Langseth, M.

2003-09-01

396

Abnormal scintigraphic evolution in AA hepatic amyloidosis  

SciTech Connect

A patient with AA amyloidosis secondary to ankylosing spondylitis showed intense liver uptake of Tc-99m MDP on bone imaging. The biopsy showed hepatic amyloid deposition. A repeat bone scan with Tc-99m MDP 1 year later was negative, although the clinical signs and liver function tests of the patient had not changed. A mechanism might exist, other than the affinity of amyloid to calcium, which would explain the extraosseous uptake of pyrophosphates and diphosphonates in organs and soft tissues affected by systemic amyloidosis.

Lomena, F.; Rosello, R.; Pons, F.; Grau, M.; Garcia, A.; Catafau, A.; Setoain, J.

1988-03-01

397

Characterization of AA size lithium rechargeable cells  

Microsoft Academic Search

Testing of AA size rechargeable cells for underwater vehicle and other naval applications is complete for AT&T's lithium\\/niobium triselenide (Li\\/NbSe3) and Moli Energy's lithium\\/molybdenum disulfide (Li\\/MoS2) and in progress on Moli Energy's lithium\\/manganese dioxide (Li\\/MnO2) and W. R. Grace's lithium\\/titanium disulfide (Li\\/TiS2). Cell cycling was performed at various discharge rates, temperatures, and depths of discharge. At 25 C and 1

T. C. Murphy; D. M. Cason-Smith; S. D. James; P. H. Smith

1990-01-01

398

Characterization of AA size lithium rechargeable cells  

Microsoft Academic Search

Testing of AA size rechargeable cells for underwater vehicle and other naval applications is complete for AT&T's lithium\\/niobium triselenide (Li\\/NbSe3) and Moli Energy's lithium\\/molybdenum disulfide (Li\\/MoS2) and is in progress on Moli Energy's lithium\\/manganese dioxide (Li\\/MnO2) and W.R. Grace's lithium\\/titanium disulfide (Li\\/TiS2). Cell cycling was performed at various discharge rates, temperatures, and depths of discharge. At 25°C and 1 mA\\/cm2

T. C. Murphy; D. M. Cason-Smith; S. D. James; P. H. Smith

1990-01-01

399

Experimental immunologically mediated aplastic anemia (AA) in mice: cyclosporin A fails to protect against AA  

SciTech Connect

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.

Knospe, W.H.; Steinberg, D.; Gratwohl, A.; Speck, B.

1984-07-01

400

Tree-stem diameter fluctuates with the lunar tides and perhaps with geomagnetic activity.  

PubMed

Our initial objective has been to examine the suggestion of Zürcher et al. (Nature 392:665–666, 1998) that the naturally occurring variations in stem diameter of two experimental trees of Picea alba were related to near simultaneous variations in the lunisolar tidal acceleration. The relationship was positive: Lunar peaks were roughly synchronous with stem diameter peaks. To extend the investigation of this putative relationship, additional data on stem diameter variations from six other tree species were gathered from published literature. Sixteen sets of data were analysed retrospectively using graphical representations as well as cosinor analysis, statistical cross-correlation and cross-spectral analysis, together with estimated values of the lunisolar tidal acceleration corresponding to the sites, dates and times of collection of the biological data. Positive relationships were revealed between the daily variations of stem diameter and the variations of the lunisolar tidal acceleration. Although this relationship could be mediated by a 24.8-h lunar rhythm, the presence of a solar rhythm of 24.0 h could not be ruled out. Studies of transpiration in two of the observed trees indicated that although this variable was not linked to stem diameter variation, it might also be subject to lunisolar gravitational regulation. In three cases, the geomagnetic Thule index showed a weak but reciprocal relationship with stem diameter variation, as well as a positive relationship with the lunisolar tidal force. In conclusion, it seems that lunar gravity alone could influence stem diameter variation and that, under certain circumstances, additional regulation may come from the geomagnetic flux. PMID:20393759

Barlow, Peter W; Mikulecký, Miroslav; St?eštík, Jaroslav

2010-11-01

401

AA online: the enactment of supportive Computer Mediated Communication  

Microsoft Academic Search

This study compared self?presentation and other?orientation behaviors and interaction patterns in three types of online AA groups (i.e., asynchronous discussions, formal synchronous AA meetings, and informal chats) to the behaviors and interaction patterns in other computer mediated support groups and computer mediated nonsupport (interest) groups. Results showed AA groups differed somewhat from other support groups and support groups differed from

C. Arthur VanLear; Megan Sheehan; Lesley A. Withers; Robert A. Walker

2005-01-01

402

The un-uniform observatories location effect in the Dst index  

NASA Astrophysics Data System (ADS)

The Dst index is a major planetary magnetic activity index proposed by Sugiura in 1964, which is designed to depict the temporal development of the magnetic storm and the intensity of the ring current system flowing in the equatorial plane of the magnetosphere at 3 to 8 Earth radii. It is an hourly index derived from the average value of the horizontal component of the geomagnetic field at four low latitudinal observatories (namely, HER, HON, KAK and SJG). For a long time, the Dst index is greatly doubted. Researchers have pointed out that a great proportion of the Dst index is originated from the Substorm Wedge current system, the Cross-tail current and the Partial ring current system [Turner et al., 2000; Liemohn et al., 2001; Ohtani et al., 2001; Rostoker, 2000; Friedrich et al., 1999; Maltsev, 2003; Huang, 2004; Hakkinen et al., 2002]. The ring current system and its disturbed storm-time field (Dst field) take on an enhanced dawn-dusk asymmetry during disturbed time. Therefore, the influence of the non-uniform location of four observatories of the Dst index will enhance. The purpose of this paper is to study the influence of the observatories' location on the Dst index. The hourly data of the horizontal component of the geomagnetic field in the observatories in geomagnetic latitude between 45°S and -45°N is used, to derive the local-time distribution model of the Dst field by the method of Nature Orthogonal Component and Cubic Polynomial Fitting. Results suggest that the maximum difference to the LT-model with four Dst index stations is about 5% lowness on 16UTmp, 3% highness on 05UTmp, and the minimum difference is around 11UTmp (UTmp corresponds to the universal time of the minimum of the Dst index). It proves some certain extent efficiency afforded by adding observatories in the SYM index.

Wu, Y.

2012-12-01

403

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)

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.

Voorhies, Coerte V.

1993-01-01

404

European Project to Improve Models of Geomagnetically Induced Currents  

NASA Astrophysics Data System (ADS)

Geomagnetically induced currents (GICs) from solar storms pose a risk to the operation of power transmission grids in Europe and across the globe. The European Risk from Geomagnetically Induced Currents (EURISGIC) project, which began in March 2011 and is supported by the Seventh Framework Programme of the European Union, seeks to mitigate this natural hazard by developing European capabilities for GIC forecasting and warning. Recent well-recognized GIC events were the province-wide blackout in Quebec, Canada, in March 1989 and the blackout in the city of Malmö, in southern Sweden, during the Halloween storm of October 2003. The progressive integration of interconnected and geographically wide power transmission grids is obviously increasing the GIC risk. Hence, there is a need for greater scientific understanding of phenomena in the solar-terrestrial environment that lead to GICs and for the development of systems that facilitate GIC modeling, forecasting, and mitigation.

Viljanen, Ari

2011-07-01

405

A new regard about Surlari National Geomagnetic Observatory  

NASA Astrophysics Data System (ADS)

Geomagnetic field study in Romanian stations has started with irregular measurements in late XIXth century. In 1943, the foundation of Surlari National Geomagnetic Observatory (SNGO) marks the beginning of a new era in the systematic study of geomagnetic field by a continuous registration of its variations and by carrying out standard absolute measurements in a fundamental station. The location of the observatory meets the highest exigencies, being situated in physical-geological conditions of a uniform local field, at a reasonably long distance from human activities. Its laboratories observe strict conditions of non-magnetism, ensuring the possibility of absolute standard measurements (national magnetic standards) for all the units in the country, civil or military, which are endowed with equipment based on geomagnetic metrology. These basic conditions have allowed the observatory to become by developing its initial preoccupations a centre of complex geomagnetic research, constantly involved in national and international issues, promoting new themes in our country and bringing significant contributions. During the last two decades, infrastructure and equipment used in monitoring geomagnetic field at European and planetary level have experienced a remarkable development. New registering techniques have allowed a complete to automate of data acquisition, and sampling step and their precision increased by two classes of size. Systems of transmitting these data in real time to world collecting centres have resulted in the possibility of approaching globalize studies, suitable for following some phenomena at planetary scale. At the same time, a significant development in the procedures of processing primary data has been registered, based on standardized programmes. The new stage of this fundamental research, largely applicable in various fields, is also marked by the simultaneous observation of space-time distribution of terrestrial electromagnetic field by means of stations set on satellites circling on orbits around the Earth. In Romania, fundamental research in this field have developed within a special unit SNGO, which has followed ever since its foundation two main objectives: a permanent observation of planetary magnetic field within a world net of observatories, and rendering evident some local disturbances connected, through electromagnetic induction, to the geological structure of our country's territory. Since 1998, Romanian researchers have been allowed to take part in the largest international scientific cooperation programme in the field INTERMAGNET. Last year in SNGO was made modernize of infrastructure, techniques, apparatus and informatics system suitable for acquisition, procession and interpretation of data for a continuous and systematic study of Earth electromagnetic field. After geomagnetic field and telluric field analysis of external components (daily, semi-daily, continuous and non-continuous pulsations, disturbances magnetic storms, seismic-electric signals, etc), as well as of internal components correlated with geodynamic activity and events with natural risk. Correlative phenomenological interpretation of the results obtained by SNGO with the ones obtained by other geomagnetic observatories in the INTERMAGNET network, as well as to the possibility of separating causes at local, regional and planetary scale.

Asimopolos, Laurentiu; Asimopolos, Natalia-Silvia; Pestina, Agata-Monica