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1

Relations between the solar inertial motion, solar activity and geomagnetic index aa since the year 1844  

NASA Astrophysics Data System (ADS)

The series of geomagnetic index aa and the series of the sunspot numbers W have been processed in the three intervals related to the three different intervals of the solar inertial motion (SIM) due to the giant planets: 1844-1905, 1906-1956 and 1957-2005. In the second interval, the Sun moves along the stable trefoil orbit, where its motion along one motion loop (arc) lasts 10 years. The orbits of the Sun in the first and the third intervals are of disordered type and differ one to other. Power spectra of both the solar and the geomagnetic activity in the central interval show the dominant period of 10.1 year and their patterns are very similar. Dominant period of sunspot numbers (index aa) in the first interval is the period of 11.4 (11.3) years. In the third interval, the period of 10.7 (10.8) years was detected. The spectra for W and aa computed for the first and third interval significantly mutually differ. The best fitted line for the second (trefoil) interval of solar and also of geomagnetic index aa is the straight line, for the first (third) intervals it is polynomial of the second (third) order.

Charvátová, Ivanka; St?eštík, Jaroslav

2

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

3

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

NASA Astrophysics Data System (ADS)

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

Dominic, Obiegbuna; Okeke, Fransisca; Okpala, Kingsley

4

A real time index of geomagnetic background noise for the MAD (Magnetic Anomaly Detection) frequency band  

NASA Astrophysics Data System (ADS)

An index of geomagnetic activity in the upper part of the ultra low frequency (ULF) range (less than 4.55 Hz) has been developed. This index will be referred to as the MA index (magnetic activity index). The MA index is prepared every half hour and is a measure of the strength of the geomagnetic activity in the Pc1-Pc3 pulsation frequency range during that half hour period. Activity in the individual Pc pulsation ranges can also be measured, if desired. The index is calculated from the running average of the full-wave rectified values of the band pass filtered geomagnetic signals and thus it provides a better indication of the magnitude of these band pass filtered magnetic pulsations than does the ap index, for example. Daily variations of the band pass filtered magnetic signals are also better captured by the MA index. To test this system we used analog tape recordings of wide-band geomagnetic signals. The indices for these tapes are presented in the form of plots, together with a comparison with the ap indices of the same time intervals. The MA index shows the daily variation of the geometric signals quite clearly during times when there is strong activity, i.e., when the ap index values are large. Because impulsive signals, such as lightning discharges, tend to be suppressed in the averaging process, the MA index is insensitive to impulsive noise. It is found that the time variation of the MA index is in general markedly different from the variation of the ap index for the same time intervals.

Bernardi, A.; Fraser-Smith, A. C.; Villard, O. G.

1985-02-01

5

Relationship Between the Magnetic Flux of Solar Eruptions and the Ap Index of Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

Solar coronal mass ejections (CMEs) are the main drivers of the most powerful non-recurrent geomagnetic storms. In the extreme-ultraviolet range, CMEs are accompanied by bright post-eruption arcades and dark dimmings. The analysis of events of Solar Cycle 23 (Chertok et al. in Solar Phys. 282, 175, 2013) revealed that the summarized unsigned magnetic flux in the arcades and dimming regions at the photospheric level, ?, is significantly related to the intensity (Dst index) of geomagnetic storms. This provides the basis for the earliest diagnostics of geoefficiency of solar eruptions. In the present article, using the same data set, we find that a noticeable correlation also exists between the eruptive magnetic flux, ?, and another geomagnetic index, Ap. As the magnetic flux increases from some tens to ? 500 (in units of 1020 Mx), the geomagnetic storm intensity measured by the three-hour Ap index increases on average from Ap ? 50 to a formal upper limit of 400 (in units of 2 nT). The established relationship shows that the real value of the Ap index is not limited and during the most severe magnetic storms may significantly exceed 400.

Chertok, I. M.; Abunina, M. A.; Abunin, A. A.; Belov, A. V.; Grechnev, V. V.

2015-02-01

6

A combined solar and geomagnetic index for thermospheric climate  

NASA Astrophysics Data System (ADS)

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

Hunt, Linda A.; Mlynczak, Martin G.

2015-04-01

7

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

8

Comparison of efficiency of artificial neural networks for forecasting the geomagnetic activity index D st  

Microsoft Academic Search

Using artificial neural networks (ANN), we study problems of forecasting the evolution of the geomagnetic D\\u000a st\\u000a index on the basis of parameters of the solar-wind plasma and magnetic field obtained from the OMNI satellite system. Using\\u000a this sample problem, we compare the neural network modifications with error backpropagation, such as classic network and feedback\\u000a network. We analyze the efficiency

N. A. Barkhatov; N. S. Bellustin; A. E. Levitin; S. Y. Sakharov

2000-01-01

9

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

Microsoft Academic Search

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

Wallace H. Campbell

1979-01-01

10

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

11

COURSE COVERAGE REPORTS -Index Spring 1969 COURSE TITLE INSTRUCTOR AA  

E-print Network

CPSC 2600 Introduction to Computation P.N. Daykin x MATH 1000 Introduction to Mathematics F.J. Papp x AA CPSC 2650 Advanced Programming & Data Processing P.N. Daykin x CPSC 2670 Numerical Methods Frank Inference T.K. Wignall x Fall 1970 COURSE TITLE INSTRUCTOR AA CPSC 2600 Introduction to Computation x x #12

Seldin, Jonathan P.

12

Response of the Geomagnetic Activity Index K p to the Interplanetary Magnetic Field  

Microsoft Academic Search

latter half of 1965 have been compared with the 3-hour Kindex. The results are consistent with those obtained by IMP I during three solar rotations in the winter of 1963-1964, indicat- ing a stability in the response of geomagnetic activity during these years near solar activity minimum. On the average an interplanetary magnetic field with a southward component is generally

Kenneth H. Schatten; John M. Wilcox

1967-01-01

13

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

14

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

15

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

16

Geomagnetism during solar cycle 23: Characteristics  

PubMed Central

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

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

2012-01-01

17

Nature author index Aas, P A. Human and bacterial oxidative demethylases repair alky-  

E-print Network

Aas, P A, 421, 859 Al-Abed, Y. See under Wang, H, 421, 384 Alberts, B. Feature: DNA replication, 421, 79 Alt, F W. See under Wong, K-K, 421, 643 Amella, C A. See under Wang, H, 421, 384 Amemiya, S Ruban, A V, 421, 648 Ando, Y. See under Lavrov, A N, 421, 230 Andreesen, J R. See under Bunge, M, 421

Cai, Long

18

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

NASA Technical Reports Server (NTRS)

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

Wilson, Robert M.

1989-01-01

19

Hurricane intensity changes associated with geomagnetic variation  

Microsoft Academic Search

Recently some indications have appeared that several purely meteorological processes in the terrestrial atmosphere are dependent upon magnetosphere variations. To analyse the possible relationship with North Atlantic hurricane intensification, the authors examine geomagnetic data for ten days prior to all hurricanes over the last 50 years (1950–1999). A significant positive correlation between the averaged Kp index of global geomagnetic activity

James B. Elsner; S. P. Kavlakov

2001-01-01

20

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

21

Evaluation of geomagnetic activity in the MAD frequency band (.04 to 0.6 Hz)  

NASA Astrophysics Data System (ADS)

After defining geomagnetic noise as it applies to MAD, the geomagnetic indices currently used by the fleet to predict MAD geomagnetic noise are reviewed to determine their actual applicability. The current indices are determined to be insufficient, methods are proposed for establishing a new MAD index, and a developmental MAD index system was tested. Geomagnetic fluctuations in the .04 to 2.0 Hz frequency band was recorded at Monterey, California, and used for a preliminary test of the proposed MAD index.

Schweiger, J. M.

1982-10-01

22

Geomagnetic Activity On Weekends Vs Working Days Studied By Planetary and Local 3-hourly Indices  

NASA Astrophysics Data System (ADS)

In the 1970s it was found that the geomagnetic field had become more active dur- ing weekends than during working days. Before the 1930s, activity was rather equal throughout the week and no particularly active days could be identified. After the 1930s, however, the weekends had become more active. This so-called "weekend ef- fect" was suggested to be due to power line harmonic radiation (PLHR), i.e. due to electromagnetic waves in VLF range emitted by power lines. The consumption of electric power is different on weekends and weekdays leading to different PLHR in- tensities. This, in turn, could possibly cause the ``weekend effect" in global geomag- netic activity. In the present paper we reanalyze the suggested "weekend effect" in global geomag- netic activity using the 69-year planetary geomagnetic Ap index, the 131-year antipo- dal aa index, as well as the local geomagnetic data of Sodankylä. In particular we focus on the possible dependency of this phenomenon on local time (its diurnal variation) as well as during and around special days of presumably low (industrial) consumption of power like, e.g., Christmas.

Karinen, A.; Mursula, K.; Ulich, Th.; Manninen, J.; Kultima, J.

23

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

24

Toward Constructing Operational Geomagnetic Activity Forecast Model  

NASA Astrophysics Data System (ADS)

Prediction of geomagnetic activity is one of the fundamental issues of space weather forecast. We are developing geomagnetic activity forecasting model based on the solar wind - magnetosphere - ionosphere (SW-M-I) coupling. We are operating daily space weather forecast as Regional Warning Center of Japan in International Space Environment Service (ISES). The key point of our forecasting model is ionosphereic conductivity dependence of the coupling function. We have found that the efficiency of SW-M-I coupling is not constant but has a dependence of ionospheric conductivity within the polar cap. Therefore, operational forecasting model of geomagnetic activity should take into account these variations and dependence. Our model can explain the diurnal and semiannual and solar cycle variations of geomagnetic activity from solar wind parameter and F10.7 index. We also examine the possibility of using inner heliospheric solar wind data such as STEREO data for a few days advance of geomagnetic activity forecast. Based on the comparison between ACE and STEREO data, we have found that the solar wind velocity can be predicted from the STEREO data well, but the Bz component of interplanetary magnetic field (IMF) is difficult to predict rather than the magnitude of IMF. This suggests that the probabilistic approach is needed for the mid-term geomagnetic forecast. We will introduce the future direction of our geomagnetic activity forecasting model in our presentation.

Nagatsuma, T.; Kunitake, M.; Murata, K. T.

2010-12-01

25

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

26

Geomagnetic Temporal Spectrum Catherine Constable 1 GEOMAGNETIC TEMPORAL SPECTRUM  

E-print Network

Geomagnetic Temporal Spectrum Catherine Constable ­1 GEOMAGNETIC TEMPORAL SPECTRUM Catherine Temporal Spectrum Catherine Constable ­2 GEOMAGNETIC TEMPORAL SPECTRUM The geomagnetic field varies in the geomagnetic field are distributed as a function of frequency. This can be done by estimating the spectrum

Constable, Catherine G.

27

Introduction to Geomagnetic Fields  

NASA Astrophysics Data System (ADS)

Geomagnetic fields arise from a variety of electric current sources. The main, dipolar field results from currents in the Earth's outer core. Dynamo currents, driven by motion of the Earth's ionosphere, generate daily surface field variations, and the Sun's activity modifies the Earth's magnetosphere, producing storm currents on a global scale. Using a minimum of mathematics, and without sacrificing the depth of coverage, the author presents the geomagnetic source fields. Details of measurement methods and a thorough review of the societal impact and use of geomagnetic fields complete the main text. The book concludes with appendices that summarise the necessary background mathematics, provide a comprehensive list of geomagnetic information, and detail geomagnetic utility computer programs. With its refreshing presentation, Introduction to Geomagnetic Fields will appeal to graduate students and researchers seeking an understanding of these natural phenomena.

Campbell, Wallace H.

28

Effect of geomagnetic activity on rat resistance to hypoxia.  

PubMed

Resistance to acute hypoxia in rats was evaluated by the life span after elevation to an altitude of 11,500 m at 13.00-21.00 (local time) in different seasons of one year. Geomagnetic activity was evaluated using local K index for Moscow and planetary Kp index. Total 24-h geomagnetic activity had a great impact on the life span of rats. The effects of local and planetary geomagnetic activities coincided in about 70% cases. An increase in geomagnetic activity was responsible for prolongation, decrease (2-3 times more often than prolongation), and phase changes in the life span of rats, which were the most pronounced in the case of medium geomagnetic activity, during the second half of the year (in summer and particularly in autumn), in the middle and end of the day, in rats with low resistance to hypoxia. PMID:12360358

Khachatur'yan, M L; Panchenko, L A

2002-03-01

29

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

30

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

NASA Astrophysics Data System (ADS)

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

Tiwari, Bhupendra Kumar

31

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

32

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 all types of observed precursor effects in CR what can be used for forecasting of great geomagnetic storms and possible mechanisms of these precursor effects origin. REFERENCES: Dorman L.I., et al. "Cosmic-ray forecasting features for big Forbush-decreases". Nuclear Physics B, 49A, 136-144 (1995). L.I.Dorman, et al, "Cosmic ray Forbush-decrease as indicators of space dangerous phenomenon and possible use of cosmic ray data for their pre-diction", Proc. of 26-th Intern. Cosmic Ray Conference, Salt Lake City, 6, 476-479 (1999).

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

33

Prediction of geomagnetic storms from solar wind data using Elman recurrent neural networks  

Microsoft Academic Search

In order to accurately predict geomagnetic storms, we exploit Elman recurrent neural networks to predict the Dst index one hour in advance only from solar wind data. The input parameters are the interplanetary magnetic field z-component Bz (GSM), the solar wind plasma number density n and the solar wind velocity V. The solar wind data and the geomagnetic index Dst

Jian-Guo Wu; Henrik Lundstedt

1996-01-01

34

Geomagnetic activity and diurnal variation of cosmic ray neutron intensity  

Microsoft Academic Search

A study of the geomagnetic relationship of the daily variation of Cosmic ray neutron intensity, corrected for barometric pressure\\u000a variation, at Uppsala, Sulphur Mountain, Climax, Huancayo, Buenos Aires and Mawson has been undertaken. The neutron data of\\u000a the year 1961 are divided into four groups depending upon the value of the daily geomagnetic planetary index, C\\u000a p\\u000a . The results

D. S. R. Murty; Y. Nagabhushanam; K. Ramanuja Rao

1965-01-01

35

Geomagnetic Indices Variations And Human Physiology  

NASA Astrophysics Data System (ADS)

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

Dimitrova, S.

2007-12-01

36

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

37

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

38

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

39

A millennium of geomagnetism  

Microsoft Academic Search

(1) The history of geomagnetism began around the year 1000 with the discovery in China of the magnetic com- pass. 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 electro-

David P. Stern

2002-01-01

40

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

E-print Network

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

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

1998-07-03

41

Foundations of Geomagnetism  

NASA Astrophysics Data System (ADS)

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

Jackson, Andy

42

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.

Sten Odenwald

43

Forecasting Geomagnetic Conditions in near-Earth space  

NASA Astrophysics Data System (ADS)

Geomagnetic conditions in near-Earth space have been a constantly evolving scientific field, especially during the latest years when the dependence of our everyday life on space environment has significantly increased. The scientific community managed to implement centers for the continuous monitoring of the geomagnetic conditions which resulted into short and long term forecasting of the planetary geomagnetic index Ap. In this work, the centers that have been established and are in operational mode in Russia (IZMIRAN), Greece (Athens), Kazakhstan (Almaty) and Bulgaria (Sofia) are presented. The methods that have been used for the forecasting of Ap index are demonstrated and the forecasted results in comparison to the actual Ap measurements are also discussed.

Abunina, M.; Papaioannou, A.; Gerontidou, M.; Paschalis, P.; Abunin, A.; Gaidash, S.; Tsepakina, I.; Malimbayev, A.; Belov, A.; Mavromichalaki, H.; Kryakunova, O.; Velinov, P.

2013-02-01

44

On extreme geomagnetic storms  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

45

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

46

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

47

CHAMP Density Dependence on Geomagnetic Indices  

NASA Astrophysics Data System (ADS)

The STAR accelerometer on the CHAMP satellite has made it possible to accumulate near-continuous records of thermosphere density at approximately 400 km altitude since May 2001. The response of the thermosphere under extremely quiet geomagnetic conditions, as well as for virtually every significant geomagnetic storm and all levels of activity in between, has been recorded during this period. The solar activity has decreased since the beginning of the mission, when the solar cycle was at its peak, to minimum conditions or nearly so at the end of 2006. CHAMP is in a near-polar and quasi-circular orbit, and complete local time sampling is obtained about every 4 months. Therefore, this density dataset offers unique opportunities to study the variability of the thermosphere due to geomagnetic disturbances in relation to solar activity, season, solar local time, and latitude. In the present study, the complete CHAMP density database is analyzed in terms of orbit-to-orbit variability (global response of the thermosphere) as a function of geomagnetic indices, such as ap and sectorial am (index given for 9 latitude-longitude sectors). Density residuals, obtained by de-trending the data using moving averaging windows, are computed to that purpose. The variability is characterized by the large-scale (600 - 5600 km) and medium-scale (160 - 600 km) disturbances, which are isolated by forming the residuals. Secondly, latitude- dependent (i.e., local response) variability is evaluated by binning the densities in pertinent latitude bands (e.g., equatorial, sub-auroral, auroral).

Bruinsma, S. L.; Forbes, J. M.

2007-12-01

48

GEOMAG: A Geomagnetic Field Program  

Microsoft Academic Search

The U.S. Geological Survey (USGS) has made available a new computer service for obtaining model values of the geomagnetic elements, such as declination and total field intensity. The service is part of the on-line information system of the USGS Branch of Global Seismology and Geomagnetism and is based on an interactive program called GEOMAG. The system is accessible with a

Norman W. Pedie

1987-01-01

49

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

50

British Geological Survey: Geomagnetism  

NSDL National Science Digital Library

The British Geological Survey illustrates its work monitoring the earth's magnetic field in the UK at this website. Users can learn about the six observatories located in the Atlantic and the UK. Using the Grid Magnetic Angle Calculator, visitors can determine the angle between the British National grid north and the magnetic north. The website features Mercator projects created with the World Magnetic Model, geomagnetic data for the academic community, space weather services for industry, and more. Students can find tutorials about the Earth's magnetic field, magnetic reversals, and magnetic storms.

51

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.

2014-08-01

52

Geomagnetic activity and wind velocity during the Maunder minimum  

Microsoft Academic Search

Following a given classification of geomag- netic activity, we obtained aa index values for the Maunder minimum (1645-1715). It is found that the recurrent and fluctuating activities were not appreciable and that the shock activity levels were very low. The aa index level was due almost entirely to the quiet days. Calculated average solar-wind velocities were 194.3 km s)1 from

B. Mendoza

1997-01-01

53

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

PubMed

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

Conesa, J

1995-06-01

54

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

Microsoft Academic Search

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

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

2010-01-01

55

Geodetic observations at geomagnetic observatories  

NASA Astrophysics Data System (ADS)

Geodetic observations at geomagnetic observatories are used to orient reference directions in relation to a common coordinate grid. This problem is solved with the use of the measuring tools of global navigation satellite systems (GNSS). The results of experimental GNSS determinations at the St. Petersburg Geomagnetic Observatory, Russia, are presented. Combination of magnetic and GNSS observations is proposed in order to reveal the cause-effect relationships between magnetic field variations and global geodynamic processes.

Kaftan, V. I.; Krasnoperov, R. I.

2015-01-01

56

Study of the Forbush Decreases, Geomagnetic Storms, and Ground-Level Enhancements in Selected Intervals and Their Space Weather Implications  

NASA Astrophysics Data System (ADS)

We analysed geomagnetic storms, ground-level enhancements (GLEs), and Forbush decreases in cosmic-ray intensity that occurred in selected intervals. We used data of ground-based neutron monitors for the cosmic-ray intensity. We used the geomagnetic index Dst as a measure of the geomagnetic storm intensity. Solar observations and interplanetary plasma/field parameters were used to identify the solar cause(s), interplanetary structure(s), and physical mechanism(s) responsible for the geomagnetic storms, the Forbush decreases, and the GLEs of different amplitudes and time profiles; all of them occurring within four selected periods of one month each. The observed differences in cosmic-ray and geomagnetic-activity responses to the same solar sources were used to distinguish the structures and mechanisms responsible for transient cosmic-ray modulation and geomagnetic storms.

Badruddin; Kumar, Anand

2015-03-01

57

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

58

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

NASA Astrophysics Data System (ADS)

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

Dimitrova, Svetla

2008-02-01

59

Croatian Geomagnetic Surveys 2004-2009  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

60

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

61

Association of conductivity and geomagnetic activity in the plasma sheet of geomagnetotail.  

NASA Astrophysics Data System (ADS)

Computes the specific conductivity ? of the plasma sheet for the selected 22 substorm events which occurred in the maximum solar activity year 1978-9 and finds variations with plasma ?-parameter (ratio of plasma pressure to magnetic pressure) and geomagnetic activity indices. The dependence of the correlation coefficient Rm between the planetary index Kp and sunspot number ? on the specific conductivity of the plasma sheet is studied. The effect of storm index Dst on specific conductivity is found. As the Dst level increases, specific conductivity falls and this reveals an anticorrelation between the storm index and the geomagnetic activity in the plasma sheet.

Prince, P. R.; Bindu, S.; Renuka, G.; Sindhu, M. S.; Venugopal, C.

1997-10-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

63

A Geomagnetic Reference Error Model  

NASA Astrophysics Data System (ADS)

The accuracy of geomagnetic field models, such as the International Geomagnetic Reference Field (IGRF) and the World Magnetic Model (WMM), has benefitted tremendously from the ongoing series of satellite magnetic missions. However, what do we mean by accuracy? When comparing a geomagnetic reference model with a magnetic field measurement (for example of an electronic compass), three contributions play a role: (1) The instrument error, which is not subject of this discussion, (2) the error of commission, namely the error of the model coefficients themselves in representing the geomagnetic main field, and (3) the error of omission, comprising contributions to the geomagnetic field which are not represented in the reference model. The latter can further be subdivided into the omission of the crustal field and the omission of the disturbance field. Several factors have a strong influence on these errors: The error of commission primarily depends on the time elapsed since the last update of the reference model. The omission error for the crustal field depends on altitude of the measurement, while the omission error for the disturbance field has a strong latitudinal dependence, peaking under the auroral electrojets. A further complication arises for the uncertainty in magnetic declination, which is directly dependent on the strength of the horizontal field. Here, we present an error model which takes all of these factors into account. This error model will be implemented as an online-calculator, providing the uncertainty of the magnetic elements at the entered location and time.

Maus, S.; Woods, A. J.; Nair, M. C.

2011-12-01

64

Interplanetary origin of multiple-dip geomagnetic storms  

Microsoft Academic Search

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

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

2008-01-01

65

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

66

Solar sources, interplanetary causes and space weather consequences of `multiple-dip' geomagnetic storms  

NASA Astrophysics Data System (ADS)

Study of geomagnetic storms of varying intensity has been useful to understand, (a) the physics of interplanetary plasma and field interaction with the geo-magnetosphere (b) the structure and dynamics of interplanetary structures responsible for them, (c) the physical mechanism playing important role in producing geomagnetic storms, and (d) their space weather consequences. Most of the early studies have been confined to the study of the classical geomagnetic storms with well defined time profile; a sharp decrease in Dst geomagnetic index within a day and slow recovery in about a week time or so. However, with the availability of high resolution solar/interplanetary data, it has now become possible to study the solar sources and interplanetary causes of geomagnetic storms with complex structures; one of them is the so called ‘multiple-dip’ storm. We have identified a number of such events in high resolution geomagnetic data, and analyzed them for understanding their solar and interplanetary causes. In addition, we utilized simultaneous geomagnetic and interplanetary plasma/field data to study the physical phenomena during their development. We also discuss the space weather consequences of such complex events.

Aslam, O. P. M.; Badruddin, B.

67

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

68

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

69

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

NASA Astrophysics Data System (ADS)

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

Kotzé, P. B.

2015-01-01

70

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

71

A quantitative model of geomagnetic activity  

NASA Technical Reports Server (NTRS)

A quantitative model of geomagnetic activity is developed and utilized to investigate the causes of the diurnal, seasonal, and IMF sector variations in the AL index records. This auroral index was chosen for study because of its high sensitivity to the strength of the westward electrojet and, hence, magnetospheric substorm activity. After the introduction of corrections for processes not related to substorms, ability of the function Bs to the 0.85th power x V squared to produce the observed variations in AL was examined. The annual variation of Bs was determined by superposing the contributions to Bs due to the inclination of the magnetic axis (Russell and McPherron, 1973) on an empirical mean distribution of Bz. V was assumed constant. The predicted values of ALc have been compared with observed averages for 9 years of solar cycle 20. The predicted annual variation of ALc for toward and away sectors are in good agreement with observation. While the predicted semi-annual component of ALc is in phase with observation, it is less than half the observed amplitude. The predicted diurnal variation of ALc for June is in satisfactory agreement with observation.

Holzer, R. E.; Slavin, J. A.

1982-01-01

72

Teaching Geomagnetism in High School  

NASA Astrophysics Data System (ADS)

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

Stern, D. P.

2001-05-01

73

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

74

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

E-print Network

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

Zerbo, J. L.

75

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

SciTech Connect

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

Cade, W.B.

1993-06-01

76

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.

77

Future of geomagnetism and paleomagnetism  

NASA Astrophysics Data System (ADS)

After the heady days of the 1960s, when geomagnetism and paleomagnetism provided crucial quantitative evidence for plate tectonics by establishing the geomagnetic polarity timescale, the 1980s may appear to be somewhat tame in the eyes of an average geophysicist. To such a person, the intervening 1970s may well look like a period of “mopping up” after the big event has happened, and it may not be unfair for him or her to ask what significant discoveries in geomagnetism and paleomagnetism (GP) have been made since 1970. The practitioners in this field of research are individuals who carry out their work without a large degree of formal overlap, so it is not surprising that the same question about recent accomplishments has arisen also in the minds of AGU GP Section members. This question came to the forefront especially during the 1984 AGU Fall Meeting, when members spoke strongly (in private conversations) about a perceived decrease in National Science Foundation funding of GP-related research projects.

Banerjee, S. K.; Cain, J. C.; Van der Voo, R.

78

Automatic prediction of solar flares and super geomagnetic storms  

NASA Astrophysics Data System (ADS)

Space weather is the response of our space environment to the constantly changing Sun. As the new technology advances, mankind has become more and more dependent on space system, satellite-based services. A geomagnetic storm, a disturbance in Earth's magnetosphere, may produce many harmful effects on Earth. Solar flares and Coronal Mass Ejections (CMEs) are believed to be the major causes of geomagnetic storms. Thus, establishing a real time forecasting method for them is very important in space weather study. The topics covered in this dissertation are: the relationship between magnetic gradient and magnetic shear of solar active regions; the relationship between solar flare index and magnetic features of solar active regions; based on these relationships a statistical ordinal logistic regression model is developed to predict the probability of solar flare occurrences in the next 24 hours; and finally the relationship between magnetic structures of CME source regions and geomagnetic storms, in particular, the super storms when the D st index decreases below -200 nT is studied and proved to be able to predict those super storms. The results are briefly summarized as follows: (1) There is a significant correlation between magnetic gradient and magnetic shear of active region. Furthermore, compared with magnetic shear, magnetic gradient might be a better proxy to locate where a large flare occurs. It appears to be more accurate in identification of sources of X-class flares than M-class flares; (2) Flare index, defined by weighting the SXR flares, is proved to have positive correlation with three magnetic features of active region; (3) A statistical ordinal logistic regression model is proposed for solar flare prediction. The results are much better than those data published in the NASA/SDAC service, and comparable to the data provided by the NOAA/SEC complicated expert system. To our knowledge, this is the first time that logistic regression model has been applied in solar physics to predict flare occurrences; (4) The magnetic orientation angle [straight theta], determined from a potential field model, is proved to be able to predict the probability of super geomagnetic storms (D= st <=-200nT). The results show that those active regions associated with | [straight theta]| < 90° are more likely to cause a super geomagnetic storm.

Song, Hui

79

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

80

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

NASA Astrophysics Data System (ADS)

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

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

81

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

82

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

83

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

84

Snowstorm at the geomagnetic observatory  

NASA Astrophysics Data System (ADS)

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

?op, R.

2015-01-01

85

Geomagnetic reversals, atmospheric escape and mass extinctions  

NASA Astrophysics Data System (ADS)

It has been known that the geomagnetic reversal rate is closely correlated with the mass extinction rate during the Phanerozoic era. In the past 50 years, many efforts were devoted to building up causal relations between them, but no consensus has been reached. On the other hand, in the last decade, it was realized that global hypoxia could be a dominant driver of mass extinctions. Here we propose that geomagnetic reversal could result in global hypoxia, because oxygen atoms will be seriously ablated by solar wind when Earth's dipole collapses during geomagnetic reversals. Based on the knowledge of atmospheric escape acquired from the research results for Mars and Venus, we have built a model to simulate atmospheric oxygen loss into interplanetary space during geomagnetic reversals. It turns out that, when the geomagnetic dipole collapses, cumulative oxygen loss could significantly contribute to the global hypoxia, which might eventually cause mass extinctions.

Wei, Yong; Pu, Zuyin; Zong, Qiugang; Wan, Weixing; Dubinin, Eduard; Fraenz, Markus

2013-04-01

86

Geomagnetic storm intensity forecast caused by magnetic clouds of solar wind  

NASA Astrophysics Data System (ADS)

Method of short-term forecast intensity of geomagnetic storms, expected by effect Solar wind magnetic clouds in the Earth's magnetosphere is developed. The method is based calculation of the magnetic field clouds distribution, suitable to the Earth, the initial satellite measurements therein components of the interplanetary magnetic field in the solar ecliptic coordinate system. Conclusion about the magnetic storm intensity is expected on the basis of analysis of the dynamics of the reduced magnetic field Bz component clouds and established communication intensity of geomagnetic storms on Dst-index values and Bz component of the interplanetary magnetic field vector.

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

2014-11-01

87

History of the geomagnetic field  

USGS Publications Warehouse

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

Doell, R.R.

1969-01-01

88

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

89

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

90

Evidence for geomagnetic jerks in comprehensive models  

NASA Astrophysics Data System (ADS)

The rate of secular variation occasionally undergoes a sudden, sharp change, called a geomagnetic jerk. Such jerks have been detected in geomagnetic time series, centered—over the last four decades—around 1971, 1980, 1991, and 1999; others have been inferred from historical records. The geomagnetic jerks represent a reorganization of the secular variation, implying an internal origin, as established through spherical harmonic and wavelet analysis. However, some characteristics of jerks are not well understood. Here we estimate the occurrence dates for geomagnetic jerks, as they can be detected from a global geomagnetic model. This choice makes the present study novel, for two reasons. First, utilizing the comprehensive modelling approach allows for the use of a secular variation signal free of time-varying external fields and their corresponding induced counterpart, and observatory biases. Second, the model utilizes satellite data when available, in addition to observatory data. Indeed, POGO (1967 to 1971), MAGSAT (1979 to 1980), Ørsted (1999 to present time) and CHAMP (2000 to present time) satellite measurements help to separate the different magnetic sources. In this study the CM4 comprehensive model is used for a global search of geomagnetic jerks and their occurrence dates. Our first result indicates that found geomagnetic jerks might not have been worldwide in occurrence. Moreover, the obtained dates suggest that jerks detected in the CM4 model over the last four decades occurred not simultaneously but at slightly different times around 1971, 1980 and 1991.

Chambodut, A.; Mandea, M.

2005-02-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

92

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

93

On the watch for geomagnetic storms  

USGS Publications Warehouse

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

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

1997-01-01

94

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

95

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.

96

Underwater geomagnetic navigation based on ICP algorithm  

Microsoft Academic Search

The trend of ocean exploitation puts forward higher requirements for automatic vehicles, while navigation module has been the development constraint for underwater robots. NATURE reported that some sea-turtles recur to geomagnetic \\

Yi Lin; Lei Yan; Qingxi Tong

2007-01-01

97

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

98

Geomagnetic main field modeling using magnetohydrodynamic constraints  

NASA Technical Reports Server (NTRS)

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

Estes, R. H.

1985-01-01

99

The International Geomagnetic Reference Field, 2005  

USGS Publications Warehouse

This is a set of five world charts showing the declination, inclination, horizontal intensity, vertical component, and total intensity of the Earth's magnetic field at mean sea level at the beginning of 2005. The charts are based on the International Geomagnetic Reference Field (IGRF) main model for 2005 and secular change model for 2005-2010. The IGRF is referenced to the World Geodetic System 1984 ellipsoid. Additional information about the USGS geomagnetism program is available at: http://geomag.usgs.gov/

Rukstales, Kenneth S.; Love, Jeffrey J.

2007-01-01

100

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.

101

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

102

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

NASA Astrophysics Data System (ADS)

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

Dorman, L. I.

2005-11-01

103

Large-scale lithospheric magnetic anomalies in Europe as revealed by recorded geomagnetic storms at the observatory network  

NASA Astrophysics Data System (ADS)

The magnetic field of the Earth, which extends in space as magnetosphere, is in permanent interaction with the solar electromagnetic, particle and magnetic flux outputs, i.e. the solar radiation, the solar wind, and, respectively, the heliospheric magnetic field. The variable current systems that develop as a result of these interactions create the so-called field of geomagnetic variations which, in turn, induces a response of the Earth's internal magnetic and conductive structures. In this study, the geomagnetic variations at storm timescales (minutes - days) provided by the network of European geomagnetic observatories have been used for modeling the magnetic structure of the European lithosphere. Large-scale magnetic structures in the lithosphere are evidenced by means of a magnetic induction model applied to geomagnetic observatory data recorded during several intense geomagnetic storm intervals (Dst<-200 nT) in the time period 2001-2005. The magnetic induction model assumes that the induced field is a linear combination of the components of the inducing field. As the inducing external source, the magnetic field of the ring current at each observatory location was used, inferred from the Dst geomagnetic index (minute). The lateral distribution of the lithosphere magnetic properties as described by the coefficients of the mentioned linear combination was derived and a comparison with distributions resulted in case of other variable sources (e.g. Sq) is discussed.

Dobrica, Venera; Demetrescu, Crisan

2013-04-01

104

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

105

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

106

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

NASA Astrophysics Data System (ADS)

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

Zenchenko, Tatiana

107

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.

108

Geomagnetic substorm association of plasmoids  

SciTech Connect

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

Moldwin, M.B.; Hughes, W.J. (Boston Univ., MA (United States))

1993-01-01

109

On Geomagnetism and Paleomagnetism I  

NASA Technical Reports Server (NTRS)

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

Voorhies, Coerte V.

2000-01-01

110

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

111

Interhemispheric asymmetry of the amplitudes of Pc3 geomagnetic pulsations  

NASA Astrophysics Data System (ADS)

The interhemispheric asymmetry between the amplitude of geomagnetic pulsations was realised already in the 1960s'. Most of the observers (Yumoto et al., 1988; Saito et al., 1989; Takahashi et al., 1994; Obana et al., 2005) reported that the energy of Pc3 (Pc4) pulsations were found to be significantly larger on the winter hemisphere (i.e. in December on the Northern hemisphere and in June in the Southern hemisphere) when comparing conjugate observations. The authors linked this behaviour to the seasonal conductivity changes of the ionosphere, however, no modelling effort were made to explain the observed behaviour. In the presented paper we make an attempt to model the seasonal asymmetry based on the model of Pilipenko et al (2008). Using data recorded at geomagnetically conjugate stations, Tihany (THY, Hungary) and Hermanus (HER, South Africa) between 2002 and 2007 we present a case where an anomalous seasonal variation can be observed. The observed amplitudes were significantly larger in local summer than in local winter, but only in years near the sunspot maximum. This is exactly the opposite what was found for other station pairs. It was also observed that the range of the seasonal variation of the HER/THY ratio diminishes with the decrease of the solar index F10.7. The phenomenon was first realised by Vero (1965) who linked the anomalous winter attenuation of pulsations to the anomalously high F2 region electron density of the ionosphere. A clear physical interpretation of these results is still missing.

Heilig, B.; Pilipenko, V.; Sutcliffe, P.

2012-04-01

112

A'a' Channel  

USGS Multimedia Gallery

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

113

Interplanetary Origin of Geomagnetic Activity in the Declining Phase of the Solar Cycle  

Microsoft Academic Search

Interplanetary magnetic field (IMF) and plasma data are contpared with ground-based geomagnetic Dsr and AE indices to determine the causes of magnetic storms, substor-(ns, and quiet during the descending phase of the solar cycle. In this paper we focus pJ imarily on 1974 when the AZ index is anomalously high (~ = 283 nT). This year is characterized by the

Bruce T. Tsurutani; Walter D. Gonzalez; Alicia L. C. Gonzalez; Frances Tang; John K. Arballo; Masaki Okada

1995-01-01

114

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

115

Magnetospheric mapping with quantitative geomagnetic field models  

NASA Technical Reports Server (NTRS)

The Mead-Fairfield geomagnetic field models were used to trace field lines between the outer magnetosphere and the earth's surface. The results are presented in terms of ground latitude and local time contours projected to the equatorial plane and into the geomagnetic tail. With these contours various observations can be mapped along field lines between high and low altitudes. Low altitudes observations of the polar cap boundary, the polar cusp, the energetic electron trapping boundary and the sunward convection region are projected to the equatorial plane and compared with the results of the model and with each other. The results provide quantitative support to the earlier suggestions that the trapping boundary is associated with the last closed field line in the sunward hemisphere, the polar cusp is associated with the region of the last closed field line, and the polar cap projects to the geomagnetic tail and has a low latitude boundary corresponding to the last closed field line.

Fairfield, D. H.; Mead, G. D.

1973-01-01

116

Determination of the Croatian geomagnetic observatory location  

NASA Astrophysics Data System (ADS)

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

Verbanac, Giuliana; Vuji?, Eugen

2012-04-01

117

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

118

Short-term periodicities in interplanetary, geomagnetic and solar phenomena during solar cycle 24  

NASA Astrophysics Data System (ADS)

In this paper we study the quasi-periodic variations of sunspot area/number, 10.7 cm solar radio flux, Average Photospheric Magnetic Flux, interplanetary magnetic field ( B z ) and the geomagnetic activity index A p during the ascending phase of the current solar cycle 24. We use both Lomb-Scargle periodogram and wavelet analysis technique and find evidence for a multitude of quasi-periodic oscillations in all the data sets. In high frequency range (10 days to 100 days), both methods yield similar significance periodicities around 20-35 days and 45-60 days in all data sets. In the case of intermediate range, the significant periods were around 100-130 days, 140-170 days and 180-240 days The Morlet wavelet power spectrum shows that all of the above-mentioned periods are intermittent in nature. We find that the well-known "Rieger period" of (150-160 days) and near Rieger periods (130-190 days) were significant in both solar, interplanetary magnetic field and geomagnetic activity data sets during cycle 24. The geomagnetic activity is the result of the solar wind-magnetosphere interaction. Thus the variations in the detected periodicity in variety of solar, interplanetary and geomagnetic indices could be helpful to improve our knowledge of the inter-relationship between various processes in the Sun-Earth-Heliosphere system.

Chowdhury, Partha; Choudhary, D. P.; Gosain, S.; Moon, Y.-J.

2015-03-01

119

Geomagnetism and climate V: general conclusions  

NASA Astrophysics Data System (ADS)

The shielding capacity of the Earth’s geomagnetic field is a prime factor regulating the flux into the atmosphere of galactic cosmic ray (in its turn controlling the 14C and 10Be production). This shielding capacity is controlled both by the Earth’s own geomagnetic field variability and by the Solar Wind variations. The Solar Wind interaction with the magnetosphere also affects the Earth’s rate of rotation (as recorded in the correlation between LOD and Sunspot activity). This opens for three possible lines of Solar Terrestrial interaction. (1) Changes in the total irradiance (known to be very small, however, over a full sun spot cycle). (2) Changes in cosmic ray flux reaching into the Earth’s atmosphere where it has the potential of affecting airglow and cloudiness (especially the cloudiness at a height in the order of 15 km). (3) Changes in the Earth’s rate of rotation affecting the oceanic circulation redistributing ocean-stored heat and water masses. The Spörer, Maunder and Dalton sun spot minima seem all to have led to periods of rotational acceleration pulling Arctic water down the European coasts and displacing the warm Gulf Stream towards Gibraltar. The geomagnetic field as regulator of cosmic ray flux and rotational potential is likely to have played a significant role even over longer time periods. It should be noted, however, the geometry of the Earth’s geomagnetic field cannot have differed very much due to frozen plasma conditions even at excursions and reversals. If the recorded sunspot and geomagnetic cycles are extrapolated into the future they predict a new low (“Little Ice Age”) in the years 2050 2100 (i.e. a scenario very different from that presented by IPCC). Our study of the relation between geomagnetism and climate has shown that geomagnetic field changes have played an important role in modulation Earth’s climate. These changes may originate from internal planetary sources (i.e. the Earth’s own geomagnetic field) as well as from external Solar variability (i.e. heliomagnetic field and Solar Wind forces). This applies, in different ways, for the present, the last 400 years, the last millennium, the last 15,000 years and the last 1 million years. Therefore, it must also be included in estimates and predictions of future changes in climate. The full INTAS team consists of: N.-A. Mörner, H. Nevanlinna, N. Abrahamsen, V. Dergachev, O. Shumilov, O. Raspopov, A. Didenko, O. Pilipenko, Z. Charonova, V. Trubikhin, E. Gooskova, S. Vasiliev, E. Kasatkina, I. Kirtsidele.

Mörner, N.-A.; Nevanlinna, H.; Dergachev, V.; Shumilov, O.; Raspopov, O.; Abrahamsen, N.; Pilipenko, O.; Trubikhin, V.; Gooskova, E.

2003-04-01

120

Local geomagnetic indices and the prediction of auroral power  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

121

A'a' Channel  

USGS Multimedia Gallery

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

122

Planetary distribution of geomagnetic pulsations during a geomagnetic storm at solar minimum  

NASA Astrophysics Data System (ADS)

We investigate the features of the planetary distribution of wave phenomena (geomagnetic pulsations) in the Earth's magnetic shell (the magnetosphere) during a strong geomagnetic storm on December 14-15, 2006, which is untypical of the minimum phase of solar activity. The storm was caused by the approach of the interplanetary magnetic cloud towards the Earth's magnetosphere. The study is based on the analysis of 1-min data of global digital geomagnetic observations at a few latitudinal profiles of the global network of ground-based magnetic stations. The analysis is focused on the Pc5 geomagnetic pulsations, whose frequencies fall in the band of 1.5-7 mHz ( T ˜ 2-10 min), on the fluctuations in the interplanetary magnetic field (IMF) and in the solar wind density in this frequency band. It is shown that during the initial phase of the storm with positive IMF Bz, most intense geomagnetic pulsations were recorded in the dayside polar regions. It was supposed that these pulsations could probably be caused by the injection of the fluctuating streams of solar wind into the Earth's ionosphere in the dayside polar cusp region. The fluctuations arising in the ionospheric electric currents due to this process are recorded as the geomagnetic pulsations by the ground-based magnetometers. Under negative IMF Bz, substorms develop in the nightside magnetosphere, and the enhancement of geomagnetic pulsations was observed in this latitudinal region on the Earth's surface. The generation of these pulsations is probably caused by the fluctuations in the field-aligned magnetospheric electric currents flowing along the geomagnetic field lines from the substorm source region. These geomagnetic pulsations are not related to the fluctuations in the interplanetary medium. During the main phase of the magnetic storm, when fluctuations in the interplanetary medium are almost absent, the most intense geomagnetic pulsations were observed in the dawn sector in the region corresponding to the closed magnetosphere. The generation of these pulsations is likely to be associated with the resonance of the geomagnetic field lines. Thus, it is shown that the Pc5 pulsations observed on the ground during the magnetic storm have a different origin and a different planetary distribution.

Kleimenova, N. G.; Kozyreva, O. V.

2014-01-01

123

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

124

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

NASA Astrophysics Data System (ADS)

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

Masci, Fabrizio

2012-08-01

125

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

126

Geomagnetism and paleomagnetism 1979-1983  

Microsoft Academic Search

My function, in writing these notes, is to bring you up to date in Geomagnetism and Paleomagnetism, in as painless a manner as possible---without tears, as the French language texts for tourists used to promise. In writing this account of progress in the past quadrennium, I must first acknowledge that it is a personal and subjective viewpoint;; another reporter would

M. Fuller

1983-01-01

127

Quantifying extreme behavior in geomagnetic activity  

NASA Astrophysics Data System (ADS)

Understanding the extremes in geomagnetic activity is an important component in understanding just how severe conditions can become in the terrestrial space environment. Extreme activity also has consequences for technological systems. On the ground, extreme geomagnetic behavior has an impact on navigation and position accuracy and the operation of power grids and pipeline networks. We therefore use a number of decades of one-minute mean magnetic data from magnetic observatories in Europe, together with the technique of extreme value statistics, to provide a preliminary exploration of the extremes in magnetic field variations and their one-minute rates of change. These extremes are expressed in terms of the variations that might be observed every 100 and 200 years in the horizontal strength and in the declination of the field. We find that both measured and extrapolated extreme values generally increase with geomagnetic latitude (as might be expected), though there is a marked maximum in estimated extreme levels between about 53 and 62 degrees north. At typical midlatitude European observatories (55-60 degrees geomagnetic latitude), compass variations may reach approximately 3-8 degrees/minute, and horizontal field changes may reach 1000-4000 nT/minute, in one magnetic storm once every 100 years. For storm return periods of 200 years the equivalent figures are 4-11 degrees/minute and 1000-6000 nT/minute.

Thomson, Alan W. P.; Dawson, Ewan B.; Reay, Sarah J.

2011-10-01

128

Geomagnetic induction soundings over the Michigan Basin  

Microsoft Academic Search

Geomagnetic variation sounding and magnetotelluric results from six sites on an east-west long-period profile across the Michigan Basin are presented. A strongly conductive zone on the western flank of the presumed underlying Keweenawan rift system in the Precambrian basement is shown to exist near Cadillac, Michigan. This zone is perhaps similar in character to the Flambeau anomaly exposed at the

C. Flores; R. C. Bailey

1987-01-01

129

Space radiation enhancement linked to geomagnetic disturbances.  

PubMed

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

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

1997-12-01

130

Space radiation enhancement linked to geomagnetic disturbances.  

PubMed

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

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

1998-01-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

132

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

133

Cosmic Rays during Intense Geomagnetic Conditions and their Solar / Interplanetary features  

NASA Astrophysics Data System (ADS)

In this study we discuss the behavior of cosmic rays during the phase of highly intense or ultra intense geomagnetic storms, as shocks driven by energetic coronal mass ejections (CME’s) and other interplanetary (IP) transients are mainly responsible for initiating large and intense geomagnetic storms. Observational results indicate that galactic cosmic rays (CR) coming from deep surface interact with these abnormal solar and IP conditions and suffer modulation effects. In this paper a systematic study has been performed to analyze the CRI variation during super storms i.e. very intense geomagnetic storms with Dst index ? -300 nT. The neutron monitor data of three stations Oulu (Rc = 0.77 GV), Climax (Rc = 2.97 GV) and Huancayo (Rc = 13.01 GV) well distributed over different latitudes and hourly values of IMF parameters derived from satellite observations near Earth IP medium from OMNI Data base is used for the period spanning over solar cycles 20, 21, 22 and 23. It is found that AP and AE indices show rise before the forward turnings of IMF, while the Dst index shows a classic storm time decrease. The analysis indicates that the magnitude of all the responses depends on BZ component of IMF being well correlated with solar maximum and minimum periods. Transient decrease in cosmic ray intensity with slow recovery is observed during the storm phase duration.

Kaushik, Subhash Chandra

134

The study of interplanetary shocks, geomagnetic storms, and substorms with the WINDMI model  

NASA Astrophysics Data System (ADS)

WINDMI is a low dimensional plasma physics-based model of the coupled magnetosphere-ionosphere system. The nonlinear system of ordinary differential equations describes the energy balance between the basic nightside components of the system using the solar wind driving voltage as input. Of the eight dynamical variables determined by the model, the region 1 field aligned current and ring current energy is compared to the westward auroral electrojet AL index and equatorial geomagnetic disturbance storm time Dst index. The WINDMI model is used to analyze the magnetosphere-ionosphere system during major geomagnetic storms and substorms which are community campaign events. Numerical experiments using the WINDMI model are also used to assess the question of how much interplanetary shock events contribute to the geoeffectiveness of solar wind drivers. For two major geomagnetic storm intervals, it is found that the magnetic field compressional jump is important to producing the changes in the AL index. Further, the WINDMI model is implemented to compute model AL and Dst predictions every ten minutes using real-time solar wind data from the ACE satellite as input. Real-Time WINDMI has been capturing substorm and storm activity, as characterized by the AL and Dst indices, reliably since February 2006 and is validated by comparison with ground-based measurements of the indices. Model results are compared for three different candidate input solar wind driving voltage formulas. Modeling of the Dst index is further developed to include the additional physical processes of tail current increases and sudden commencement. A new model, based on WINDMI, is developed using the dayside magnetopause and magnetosphere current systems to model the magnetopause boundary motion and the dayside region 1 field aligned current which is comparable to the auroral upper AU index.

Mays, Mona Leila

2009-11-01

135

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

136

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

137

Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity  

NASA Astrophysics Data System (ADS)

Physical meaning of the equinoctial effect for semi-annual variation in geomagnetic activity is investigated based on the three-hourly am index and solar wind parameters. When the z component of the interplanetary magnetic field (IMF) in geocentric solar magnetospheric (GSM) coordinates is southward, am indices are well correlated with BsVx2, where Bs is the southward component of the IMF and Vx is the solar wind velocity in the sun-earth direction. The am-BsVx2 relationship, however, depends on the range of Vx2: the am in higher ranges of Vx2 tends to be larger than am in lower ranges of Vx2 for the same value of BsVx2 for both equinoctial and solstitial epochs. Using the data sets of the same Vx2 range, it is shown that distribution of points in the am-BsVx2 diagram at the solstitial epochs overlaps with that at the equinoctial epochs and the average am values in each BsVx2 bin in solstitial epochs are closely consistent with those in equinoctial epochs, if Vx2 for each point at solstices are reduced to Vx2sin2 (?) where ? is the geomagnetic colatitude of the sub-solar point. Further, it is shown that monthly averages of the am index in the long period is well correlated with the values of sin2(?) for the middle day of each month. These findings indicate that the factor that contributes to the generation of geomagnetic disturbance is not the velocity of the solar wind, but the component of the solar wind velocity perpendicular to the dipole axis of the geomagnetic field. The magnitude of the perpendicular velocity component varies semi-annually even if the solar wind velocity remains constant, which is considered to be the long-missed key factor causing the equinoctial effect.

Yoshida, A.

2009-05-01

138

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

139

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

140

Geomagnetic variations and solar activity relationship in the South Atlantic Geomagnetic Anomaly -SAMA  

NASA Astrophysics Data System (ADS)

Comparative studies between the ACE satellite's solar wind parameters (speed and density of the solar plasma ) and the geomagnetic variations recorded in the Southern Space Observatory -SSO/CRS/INPE -MCT, São Martinho da Serra, (29,43° S, 53,82° W, 488m a.s.l.), RS, Brazil, a were performed. The three orthogonal geomagnetic field components data were acquired with a fluxgate magnetometer with 0.5Hz acquisition rate. Comparisons between the temporal evolution of the geomagnetic field intensity and the solar wind parameters for different phases of the solar cycle were analyzed. It was possible to identify fast changes in the geomagnetic field which may be correlated with stronger or wicker solar activity with important effects around midday in the local Ionosphere. This fact confirm the existence of relationships between the local geomagnetic variations and the solar activity. The periods of higher solar activity are related to a significant increasing in the flow of electrically charged particles in the atmosphere. As consequence of the physical and chemical phenomena, associated to these particles flow increases, are damages in satellites that orbit this region, as well as the induced electric currents in the Earth surface that causes damages in the electric power systems.

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

141

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

142

Lower mantle superplume growth excites geomagnetic reversals  

NASA Astrophysics Data System (ADS)

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

Amit, Hagay; Olson, Peter

2015-03-01

143

Planetary waves during a moderate geomagnetic storm  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

144

Database for Holocene Geomagnetic Intensity Information  

Microsoft Academic Search

Over the past 40 years, paleomagnetists have continued to compile new data. A large part of these data are now archived in seven independent databases that are maintained by the International Association of Geomagnetism and Aeronomy (IAGA; (http:\\/\\/www.ngdc.noaa.gov\\/seg\\/geomag\\/paleo.shtml). Unfortunately, the IAGA paleointensity database [Perrin and Schnepp, 2004] does not contain data from archeological artifacts, which is a major part of

Fabio Donadini; Kimmo Korhonen; Peter Riisager; Lauri J. Pesonen

2006-01-01

145

KAr ages of the Auckland geomagnetic excursions  

Microsoft Academic Search

K-Ar age determinations were made on two monogenetic volcanoes in the Auckland volcanic field, New Zealand, which have recorded the Auckland geomagnetic excursions. For the Wiri volcano with the north-down intermediate paleomagnetic direction, five samples gave a weighted mean age of 27 ± 5 (1s) ka. For the Hampton Park volcano with the west-up intermediate direction, three samples gave a

Nobutatsu Mochizuki; Hideo Tsunakawa; Hidetoshi Shibuya; Takahiro Tagami; Ayako Ozawa; John Cassidy; I. E. M. Smith

2004-01-01

146

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

147

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

PubMed

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

Conesa, J

1997-10-01

148

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

149

Correlation between geomagnetic indices and cross polar cap potential measurements from SuperDARN  

NASA Astrophysics Data System (ADS)

The cross polar cap potential, or phiPC, is a global measure of the Magnetosphere---Ionosphere system, applicable in studying the coupling between the solar wind and the magnetosphere, magnetic reconnection and magnetospheric convection. phiPC can be determined by the line- of-sight (LOS) Doppler velocity measurements from the Super Dual Auroral Radar Network (SuperDARN) in a time period as small as a minute. Recent additions of radars to this network in the middle latitudes have been shown to improve the underestimation of the phiPC solutions in strong geomagnetic periods. This study aims to update the derivation technique of phiPC with more experimental data from the middle latitude radars and examine the statistical dependence of phiPC on the planetary K-index Kp and the auroral electrojet AE index in the Northern Hemisphere between January 01, 2009 and August 31, 2012. We use more than 89,500 high-quality measurements of phiPC for this investigation. In weak-moderate geomagnetic conditions (Kp ? 4 and AE ? 1000 nT), we found a linear correlation between phi PC and Kp, phiPC = 9.6 Kp+25.9 [kV], while the dependence of phiPC on AE is shown to be non-linear using the same dataset. For stronger geomagnetic disturbances (Kp > 4), a larger coverage of the SuperDARN network is required to justify any possible instrumental saturation of phiPC values in this range. Further, we examine the dependence of the phiPC values on the dipole tilts and discuss possible physical and instrumental saturation in phiPC estimates from SuperDARN using the Kp index in this report.

Nguyen, Dat P.

150

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

NASA Astrophysics Data System (ADS)

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

Gmitrov, Juraj

2007-03-01

151

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.

152

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

154

AAS Job Register  

NSDL National Science Digital Library

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

155

Search for correlation between geomagnetic disturbances and mortality  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

156

Empirical analytic transformations between geographic and corrected geomagnetic coordinates  

NASA Technical Reports Server (NTRS)

Based upon a mathematical model of contours of constant corrected geomagnetic latitude in a polar projection of geographic coordinates, analytic equations are developed for converting geographic coordinates to corrected geomagnetic coordinates and vice versa. The equations were programmed for use on a small computer. This treatment is restricted to the Northern Hemisphere.

Comfort, R. H.

1970-01-01

157

Comparison of TEC response for summer and winter geomagnetic storms  

Microsoft Academic Search

We investigated the response of TEC over Europe to summer and winter geomagnetic storms using observations of European GPS network. The spatial and temporal evolution of TEC during storm was analyzed on base of TEC maps which created with 1 hour interval in latitudinal range of 35° -70° N. Comparison of storm effects was carried out for severe geomagnetic storm

Irk Shagimuratov; Galina Yakimova; Irina Zakharenkova; Andrzej Krankowski

2008-01-01

158

Latitudinal reversal of polarization of the geomagnetic sudden commencement  

Microsoft Academic Search

Latitudinal variation of polarization of geomagnetic sudden commencements (sc) observed at geomagnetic latitude range 63 deg N to 79 deg N is studied by the use of North American IMS magnetometer data from August 1978 to May 1979. Fourteen sc's out of 18 examined show clear polarization reversal between latitudes 64 deg N and 72 deg N. Among these, nine

Tox-mu ARAKI; J. H. Allen

1982-01-01

159

THE PALEOMAGNETISM OF SINGLE SILICATE CRYSTALS: RECORDING GEOMAGNETIC FIELD  

E-print Network

THE PALEOMAGNETISM OF SINGLE SILICATE CRYSTALS: RECORDING GEOMAGNETIC FIELD STRENGTH DURING MIXED of the geomagnetic reversal chronology of the last 160 million years are well established. The relationship between of in situ and laboratory-induced alteration. Here we review an alternative approach. Single plagioclase

Jellinek, Mark

160

Impacts of geomagnetic storms on EHV and UHV power grids  

Microsoft Academic Search

This paper describes the threat of geomagnetic storms created by solar activity to EHV and UHV power grids based on the experience of the past. It is clear from the available data that the higher the voltage of the AC power system, the more vulnerable that system is to a particular geomagnetic storm. Given a description of the time and

W. A. Radasky; J. G. Kappenman

2010-01-01

161

Geomagnetic storm effects on the earth's ozone layer  

Microsoft Academic Search

The study of the response of the terrestrial environment to the different forms of solar activity is a relevant task. Geomagnetic perturbations arise from the solar wind\\/magnetospheric coupling and major magnetic storms are caused by intense, long duration Southward interplanetary magnetic fields. This paper addresses reader's attention on possible effects induced by geomagnetic storms on the Earth's ozone layer by

M. Storini

2001-01-01

162

The use of geomagnetic field models in magnetic surveys  

NASA Technical Reports Server (NTRS)

The importance of global geomagnetic field models for the reduction of magnetic surveys is discussed. It is demonstrated that a numerical model with adequate secular variation correction, provides a suitable representation of the regional field. The limitations of the presently available models are reported, with emphasis on the International Geomagnetic Reference Field.

Regan, R. D.; Gain, J. C.

1974-01-01

163

The Geomagnetic Field in Space, Ring Currents, and Auroral Isochasms  

Microsoft Academic Search

Using a 48-coefficient spherical harmonic expansion of the geomagnetic field for 1955.0, the results of an analysis due to Finch and Leaton, it is shown that geomagnetic field lines appear to interlink the northern and southern auroral zones. Theoretical average auroral isochasms are also estimated using an integral invariant for particle motion along the lines of force and between the

E. H. VESTINE

1967-01-01

164

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

165

Geomagnetic Polarity Epochs: Sierra Nevada Data, 3  

Microsoft Academic Search

Available palcomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85 ñ 0.15 million years; Matuyama reversed polarity epoch, 0.85 ñ 0.15 to 2.4 ñ 0.1 million years; Gauss normal polarity epoch, 2.4 ñ 0.1 to 3.35 ñ 0.1

Richard R. Doell; G. Brent Dalrymple; Allan Cox

1966-01-01

166

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

167

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

168

Solar and Interplanetary Disturbances Causing Moderate Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

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

Pratap Yadav, Mahendra; Kumar, Santosh

2003-07-01

169

Classification of space-weather complexes based on solar source type, characteristics of plasma flow, and geomagnetic perturbation induced by it  

NASA Astrophysics Data System (ADS)

The space-weather complexes including characteristics of solar streams (parameters of the solar wind, components of the interplanetary magnetic-field vector) and temporal quantitative estimates of their geomagnetic effects ( Dst index) are classified. Comparative and neural-network methods for this classification are developed. As a result of numerical neural-network experiments, types of solar streams responsible for generation of geomagnetic perturbations with different intensities are established. It is confirmed that, on the basis of the selected space weather complexes, it is possible to refine the influence of these streams on the electromagnetic state of the magnetic sphere and, hence, improve the accuracy of predictions of this state.

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

2014-03-01

170

Forecasts of solar and geomagnetic activity  

NASA Technical Reports Server (NTRS)

Forecasts of solar and geomagnetic activity are critical since these quantities are such important inputs to the thermospheric density models. At this time in the history of solar science there is no way to make such a forecast from first principles. Physical theory applied to the Sun is developing rapidly, but is still primitive. Techniques used for forecasting depend upon the observations over about 130 years, which is only twelve solar cycles. It has been noted that even-numbered cycles systematically tend to be smaller than the odd-numbered ones by about 20 percent. Another observation is that for the last 12 cycle pairs, an even-numbered sunspot cycle looks rather like the next odd-numbered cycle, but with the top cut off. These observations are examples of approximate periodicities that forecasters try to use to achieve some insight into the nature of an upcoming cycle. Another new and useful forecasting aid is a correlation that has been noted between geomagnetic indices and the size of the next solar cycle. Some best estimates are given concerning both activities.

Joselyn, Joann

1987-01-01

171

Solar Wind Charge Exchange During Geomagnetic Storms  

NASA Technical Reports Server (NTRS)

On March 31st. 2001, a coronal mass ejection pushed the subsolar magnetopause to the vicinity of geosynchronous orbit at 6.6 RE. The NASA/GSFC Community Coordinated Modeling Center (CCMe) employed a global magnetohydrodynamic (MHD) model to simulate the solar wind-magnetosphere interaction during the peak of this geomagnetic storm. Robertson et aL then modeled the expected 50ft X-ray emission due to solar wind charge exchange with geocoronal neutrals in the dayside cusp and magnetosheath. The locations of the bow shock, magnetopause and cusps were clearly evident in their simulations. Another geomagnetic storm took place on July 14, 2000 (Bastille Day). We again modeled X-ray emission due to solar wind charge exchange, but this time as observed from a moving spacecraft. This paper discusses the impact of spacecraft location on observed X-ray emission and the degree to which the locations of the bow shock and magnetopause can be detected in images.

Robertson, Ina P.; Cravens, Thomas E.; Sibeck, David G.; Collier, Michael R.; Kuntz, K. D.

2012-01-01

172

Geomagnetic excursions reflect an aborted polarity state  

NASA Astrophysics Data System (ADS)

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

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

2008-10-01

173

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

174

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

SciTech Connect

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. [Big Bear Solar Observatory, Big Bear City, CA 92314 (United States); Gopalswamy, N. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ozguc, A. [Kandilli Observatory and Earthquake Research Institute, Bogazici University, 34684 Istanbul (Turkey); Rozelot, J. P. [Nice University, OCA-Fizeau Dpt. Av. Copernic, 06130 Grasse (France)

2011-01-20

175

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.

176

Computer Programming AAS  

NSDL National Science Digital Library

This one-page PDF document from the Jefferson Community and Technical College in Kentucky presents the course options and requirements for obtaining an AAS (Associate in Applied Science) degree in computer programming. General education, technical core, management, networking, and computer programming courses at the beginning, intermediate, and advanced levels are listed. This document would be helpful for anyone interested in procuring an entry-level computer programming position, or for information technology instructors at the high school and college levels engaged in curriculum development.

177

Autonomous Airborne Geomagnetic Surveying and Target Identification  

E-print Network

C Confidence measure of particle filter D No detection event ei N Ã? 1 vector of zeros with 1 in ith index tgt Target uav Agent (UAV) Superscript [k] Agent (UAV) number index Research Assistant, Dept, Inc., with permission. #12;[m] Particle number index tgt Target frame of reference uav Agent (UAV

Lum, Christopher

178

Autonomous Airborne Geomagnetic Surveying and Target Identification  

E-print Network

C Confidence measure of particle filter D No detection event ei N Ã? 1 vector of zeros with 1 in ith index tgt Target uav Agent (UAV) Superscript [k] Agent (UAV) number index Research Assistant, Dept #12;[m] Particle number index tgt Target frame of reference uav Agent (UAV) frame of reference True

Washington at Seattle, University of

179

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

NASA Astrophysics Data System (ADS)

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

Nosikov, Igor; Klimenko, Maxim; Klimenko, Vladimir

180

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

181

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. PMID:16275503

Jozsa, R.; Halberg, F.; Cornélissen, 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.; Hüther, G.; Pöggeler, 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

182

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

PubMed

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

Jozsa, R; Halberg, F; Cornélissen, 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; Hüther, G; Pöggeler, B; Tarquini, R; Perfetto, F; Salti, R; Olah, A; Csokas, N; Delmore, P; Otsuka, K; Bakken, E E; Allen, J; Amory-Mazaudin, C

2005-10-01

183

Solar wind turbulence as a driver of geomagnetic activity  

NASA Astrophysics Data System (ADS)

We carried out simultaneous analyses of interplanetary and geomagnetic datasets for the period of (solar Maunder) least (2009) and maximum (2002) solar activity to determine the nature of solar wind turbulence on geomagnetic activity using AE, ASY-D, and ASY-H indices. We determined the role played by Alfvénic fluctuations in the solar wind so as to find out the nature of the turbulence. Our analyses showed that solar wind turbulence play a role in geomagnetic processes at high latitudes during periods of low and high solar activity but does not have any effect at mid-low latitudes.

Ugwu, Ernest Benjamin Ikechukwu; Okeke, Francisca Nneka; Ugonabo, Obiageli Josephine

2015-04-01

184

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

185

Protection against lightning at a geomagnetic observatory  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

186

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

187

CME Link to the Geomagnetic Storms  

NASA Technical Reports Server (NTRS)

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

Gopalswamy, Nat

2009-01-01

188

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

189

Geomagnetism and paleomagnetism 1979-1983  

NASA Astrophysics Data System (ADS)

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

Fuller, M.

190

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

191

Geoelectric Fields and Geomagnetically Induced Currents in the United Kingdom   

E-print Network

This thesis investigates geo-electric fields in the United Kingdom with particular regard to Geomagnetically Induced Currents (GIC) in the Scottish Power electricity transmission network (SPTN). The joint spectral characteristics of Scottish Power...

McKay, Allan John

192

Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations  

NASA Technical Reports Server (NTRS)

With the use of a prediction technique 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 geomagnetic field.

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

1971-01-01

193

Human physiological reaction to geomagnetic disturbances of solar origin  

NASA Astrophysics Data System (ADS)

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

Dimitrova, Sv.; Stoilova, I.

2002-12-01

194

A model of geomagnetic secular variation for 1980-1983  

USGS Publications Warehouse

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

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

1987-01-01

195

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

196

Behaviour of geomagnetic variations across the western ukraine  

Microsoft Academic Search

Since 1967, the staff of the Geophysical Institute of the Ukrainian Academy of Sciences and of affiliated organization in Lvov have been making observations of the geomagnetic field components across the territories of the Ukrainian Carpathians and the Volyno-Podolian plate. The field equipment IZMIRAN-4 and MEVS orientated in the geomagnetic co-ordinate system were used in recording the time variations of

I. M. Logvinov; S. N. Kulik; T. K. Burakhovich; A. I. Bilinskij; F. I. Sedova

1991-01-01

197

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

198

Tsunami effects on the Z component of the geomagnetic field  

E-print Network

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

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

2011-01-01

199

Study of Proton cutoffs during geomagnetically disturbed times  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

200

The response of GPS TEC to the sequence of September 2011 geomagnetic storms  

NASA Astrophysics Data System (ADS)

The behavior of total electron content (TEC) over European region was analyzed for the sequence of geomagnetic storms in September 2011. Three geomagnetic storms with similar magnitude and different time of occurrence took place during 3 week period. The sudden beginning of the first storm took place at 14 UT on September 09, 2011. Dst index was sharply changed from 0 to 17 nT and drop to -63 nT. The second storm occurred on September 17, 2011 at the moment of 9 UT, the Dst index changed from 30 nT to -58 nT. The third event began on September 26, 2011 at 16 UT, minimal Dst index was equal to -103 nT in 11 hours after beginning. GPS TEC estimates were calculated with using data of European GNSS network. The spatial-temporal dynamics of TEC was analyzed on the base of constructed regional TEC maps and diurnal TEC variations over selected GNSS stations spaced along meridian of 20°E between latitudes of 70°-30°N. The ionosphere's response for September 9-10, 2011 geomagnetic storm was mainly negative; the average TEC depression was about 30% at daytime over European mid-latitude stations. The short positive splash in TEC variations was observed at evening September 9 in several hours after the storm's beginning. The distinguishing feature of September 17 storm was the strong positive effect which occurred on day-time over Europe region. The enhancement of TEC reached the factor of 1.7-2.0. Maximal effect was observed at high latitudes and slowly decreased to low latitudes. The duration of positive ionospheric effect was about 4-5 h. At high latitude stations of Kiruna (Sweden) TEC reached 30 TECU in compare with undisturbed level of 13-15 TECU. The maximal TEC enhancement was rather short-term and continued only 1.0-1.5 hour. The surge of TEC enhancement was moved from north to south, the delay between Kiruna and Noto (Sicilia) stations was 120-150 min. The ionospheric storm occurred on September 27, 2011 was the strongest one in the considered period. The ionospheric depression (up to 60%) corresponds to the main phase of storm with minimal value of Dst index equal to -103 nT. The development of the negative ionospheric storm had classical character. In this report we discuss the physical process in ionosphere and magnetosphere accompanied considered events and effects.

Shagimuratov, I.; Krankowski, A.; Cherniak, Iu.; Zakharenkova, I.; Yakimova, G.; Koltunenko, L.

2012-04-01

201

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

202

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

203

Periodic substorm activity in the geomagnetic tail  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

204

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

205

Geomagnetic lunar and solar daily variations during the last 100 years  

NASA Astrophysics Data System (ADS)

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

Yamazaki, Y.; Kosch, M. J.

2014-08-01

206

Intensity of the geomagnetic field in Europe for the last 3 ka: Influence of data quality on geomagnetic field modeling  

NASA Astrophysics Data System (ADS)

of the main challenges of paleomagnetic research is to obtain high-resolution geomagnetic field intensity reconstructions. For the last millennia, these reconstructions are mostly based on archeomagnetic data. However, the quality of the intensity data available in the databases is very variable, and the high scatter observed in the records clearly suggests that some of them might not be reliable. In this work we investigate how the geomagnetic field intensity reconstructions and, hence, our present knowledge of the geomagnetic field in the past, are affected by the quality of the data selected for modeling the Earth's magnetic field. For this purpose we rank the European archeointensity data in four quality categories following widely accepted paleomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens retained to calculate the mean intensities. Four geomagnetic field regional models have been implemented by applying the revised spherical cap harmonic analysis to these four groups of input data. Geomagnetic field models strongly depend on the used data set. The model built using all the available data (without any preselection) appears to be the less accurate, indicating some internal inconsistencies of the data set. In addition, some features of this model are clearly dominated by the less reliable archeointensity data, suggesting that such features might not reflect real variations of the past geomagnetic field. On the contrary, the regional model built on selected high-quality intensity data shows a very consistent intensity pattern at the European scale, confirming that the main intensity changes observed in Europe in the recent history of the geomagnetic field occurred at the continental scale.

Pavón-Carrasco, Francisco Javier; Gómez-Paccard, Miriam; Hervé, Gwenaël.; Osete, María. Luisa; Chauvin, Annick

2014-06-01

207

Study of Proton cutoffs during geomagnetically disturbed times  

NASA Astrophysics Data System (ADS)

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

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

208

Simulations of the Geomagnetic Field Disturbances Caused by the Tunguska Event 1908  

NASA Astrophysics Data System (ADS)

The phenomena explaining the main features of geomagnetic perturbations caused by the Tunguska explosion: location, start time, and signs of disturbances of the geomagnetic field have been simulated. Azimuth of trajectory of the bolide has been defined.

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

2012-03-01

209

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

210

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

211

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

212

ULF geomagnetic anomaly preceding large earthquakes  

NASA Astrophysics Data System (ADS)

baselineskip 3.3mm This report is the summary of observational facts associated with earthquake related ULF geomagnetic emissions during 5 years project of RIKEN IFREQ and NASDA - UEC group (1997.4 - 2002.3). The aim of this project is to estimate probability of ULF phenomena associated with large earthquakes and also a reliability of possible short-term earthquake prediction and monitoring of crustal activities using the ULF effects. The 5-year project has terminated in March, 2002, but we would like to do continuous observation and analyze data at possible stations. The remarkable findings at the present stage are as follows: [1] Practical basis for the regular ground ULF monitoring system has been established in Japan. It consists of Kanto-Tokai network composed by sensitive sensors (torsion and search coil type magnetometers type) with high sampling rate and stations with a fluxgate type magnetometer. The network we have installed over the Kanto-Tokai region has base lines of 5km, tens km, and 100km. [2] ULF magnetic data associated with earthquakes have been analyzed. Convincing results on the existence of preceding ULF magnetic anomaly have been obtained for Kagoshima earthquakes, Iwate earthquake, Izu earthquake swarm, Biak earthquake, and earthquakes observed at Matsushiro station. (1) Enhancement of polarization (intensity ratio of vertical and horizontal components) a few weeks preceding the main shock. (2) Tendency of increase of horizontal components just before the earthquake. (3) As for polarization analysis, the detectable distances are about 60 km for the earthquake with M=6 and 100 km for the earthquake with M = 7. [3] Principal component analysis has been adapted to the horizontal component data observed at Izu. Analyzed data have been from three sensors set at 5 km distances. A few days before M>6 earthquakes, anomalous behavior has been detected in the smallest eigenvalue during Izu earthquake swarm in 2000.

Hattori, K.; Gotoh, K.; Takahashi, I.; Kopytenko, Y.; Korepanov, V.; Hayakawa, M.; Yumoto, K.; Isezaki, N.; Nagao, T.; Uyeda, S.

2003-04-01

213

Solstitial and hemispherical asymmetry in the response of geomagnetic field  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

214

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

215

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

216

Using the moon to probe the geomagnetic tail lobe plasma  

NASA Technical Reports Server (NTRS)

We have detected the presence of plasma in the lobes of the geomagnetic tail from observations of magnetic induction in the moon forced by time variations of the earth's magnetotail lobe field. The magnitude of the moon's tangential electromagnetic transfer function when the moon is in the lobes of the geomagnetic tail is less than that when the moon is in the solar wind or geomagnetic tail plasma sheet. The tangential transfer function when the moon is in the magnetotail lobes decreases at frequencies above about 8 mHz due to finite wavelength effects. This shows that the waves in the magnetotail lobes which drive the lunar magnetic induction must have speeds far less than the speed of light and wavelengths comparable to the size of the moon.

Schubert, G.; Sonett, C. P.; Smith, B. F.; Colburn, D. S.; Schwartz, K.

1975-01-01

217

An experimental study of the biological effects of geomagnetic disturbances: The impact of a typical geomagnetic storm and its constituents on plants and animals  

NASA Astrophysics Data System (ADS)

Naturally occurring geomagnetic storms have been shown to correlate with changes in organisms' biological processes. Changes in the geomagnetic field during a geomagnetic storm are complex and contain both slow changes of the geomagnetic field with frequencies of up to 0.001 Hz, and various geomagnetic pulsations observed in general to be within the range of 0.001-5 Hz. Little is known about what frequency constituent of geomagnetic storms has the strongest effect on living organisms. This paper uses an experimental approach to demonstrate that organisms from different taxa principally respond to slow changes of the geomagnetic field corresponding with the main phase and the initial period of the recovery phase of a geomagnetic storm. Pc1 type pulsations, which are commonly regarded as biologically effective elements of geomagnetic disturbances, did not affect controlled parameters in our experiments. This paper may serve as a starting point for a thorough inquiry into the influence of slow fluctuations of the geomagnetic field on organisms.

Krylov, Viacheslav V.; Zotov, Oleg D.; Klain, Boris I.; Ushakova, Natalia V.; Kantserova, Nadezhda P.; Znobisheva, Anna V.; Izyumov, Yuri G.; Kuz'mina, Victoria V.; Morozov, Alexey A.; Lysenko, Liudmila A.; Nemova, Nina N.; Osipova, Elena A.

2014-04-01

218

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

219

Further Investigations of a Variation of Geomagnetic Activity with Lunar Phase  

Microsoft Academic Search

The previously studied variation of geomagnetic activity with lunar phase indicates a g,eneral decrease in geomagnetic activity of about 4% for several days before full moon and an increase of about 4% for several days after full moon. Substantial evidence is presented indicating that the observed variation of geomagnetic activity with lunar phase requires lunar latitudes at full moon within

I-IAROLD L. STOLOV

1965-01-01

220

Safety and arming method for Fuzes based on geomagnetic field signal  

Microsoft Academic Search

Based on analyzing the method of geomagnetism turns-counting and the mathematical model for testing distance, tow kinds of information are put forward as the second environment prompting of the redundant safety, one is the geomagnetism field information when the projectile exiting the muzzle, and the second is the spin signal of the projectile in the geomagnetic field. “Threshold level +

Huang Xuegong; Liu Zongyao

2010-01-01

221

Robust geomagnetic aided inertial navigation of underwater vehicles using the ICP algorithm  

Microsoft Academic Search

In this paper an algorithm is presented for positioning based on inertial navigation aided by using geomagnetic field intensity. The idea is based on matching noisy samples of geomagnetic intensities by the magnetometers and a priori geomagnetic map. The traditional Iterative Closest Point (ICP) algorithm is then applied in combination with the Inertial Navigation System (INS) to update its cumulative

Muhammad Ejaz; J. Iqbal; N. Ahsan; Akhtar Nawaz

2009-01-01

222

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

223

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

224

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

USGS Publications Warehouse

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

Campbell, W.H.

1996-01-01

225

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

NASA Astrophysics Data System (ADS)

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

Kuznetsova, Tamara

226

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

227

World-wide Changes in the Geomagnetic Field  

Microsoft Academic Search

It is found that world-wide changes in the geomagnetic field are not limited to sse or si and are frequently observed. Not only an increase but also a decrease in horizontal intensity occurs on a world-wide scale. The form of the change varies, depending both on local time and on latitude. The distribution of the magnitude, and the mode of

A. Nishida; J. A. Jacobs

1962-01-01

228

Interaction of Solar Plasma Streams with the Outer Geomagnetic Field  

Microsoft Academic Search

The general nature of the magnetic field surrounding the earth is discussed using various measurements made by space probes since 1958. It is shown that the outer geomag- netic field consists of two regions: a standing shock layer and the geomagnetic cavity. The pattern of these regions in the equatorial plane is shown in a frame fixed relative to the

Tatsuzo Obayashi

1964-01-01

229

Geomagnetic perturbations on stratospheric circulation in late winter and spring  

Microsoft Academic Search

This study investigates if the descent of odd nitrogen, generated in the thermosphere and the upper mesosphere by energetic particle precipitation (EPP-NO x ), has a detectable impact on stratospheric wind and temperature in late winter and spring presumably through the loss of ozone and reduction of absorption of solar UV. In both hemispheres, similar downward propagating geomagnetic signals in

Hua Lu; Mark A. Clilverd; Annika Seppälä; Lon L. Hood

2008-01-01

230

Geomagnetic perturbations on stratospheric circulation in late winter and spring  

Microsoft Academic Search

This study investigates if the descent of odd nitrogen, generated in the thermosphere and the upper mesosphere by energetic particle precipitation (EPP-NOx), has a detectable impact on stratospheric wind and temperature in late winter and spring presumably through the loss of ozone and reduction of absorption of solar UV. In both hemispheres, similar downward propagating geomagnetic signals in the extratropical

Hua Lu; Mark A. Clilverd; Annika Seppälä; Lon L. Hood

2008-01-01

231

Surface electric fields for North America during historical geomagnetic storms  

USGS Publications Warehouse

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, Nichole; Gannon, Jennifer L.

2013-01-01

232

Nonlinear and Multifractal Approaches of the Geomagnetic Field  

E-print Network

Non­linear and Multifractal Approaches of the Geomagnetic Field L. Hongre a b , P. Sailhac a b , M Physique du Globe de Paris, 4 place Jussieu 75252, Paris, France. Recent non­linear dynamics techniques. The non­linear and multifractal analyses were finally applied to the hourly mean values of the magnetic

Sailhac, Pascal

233

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

234

(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

235

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

236

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

237

PEGASO . Polar Explorer for Geomagnetic And other Scientific Observation  

Microsoft Academic Search

PEGASO (Polar Explorer for Geomagnetic And other Scientific Observation) program has been created to conduct small experiments in as many disciplines on-board of small stratospheric balloons. PEGASO uses the very low expensive pathfinder balloons. Stratospheric pathfinders are small balloons commonly used to explore the atmospheric circumpolar upper winds and to predict the trajectory for big LDBs (Long Duration Balloons). Installing

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

2008-01-01

238

High-voltage power grid disturbances during geomagnetic storms  

Microsoft Academic Search

The very strong geomagnetic storm on 13 March 1989 caused extensive disruptions of high-voltage power circuits especially in the Province of Quebec, Canada, but also to a lesser degree in Scandinavia. Similar events have occurred earlier, among others, during the great storms of 13 - 14 July 1982 and 8 - 9 February 1986. Some of the high-voltage power grid

Peter Stauning

2002-01-01

239

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

240

Possible helio-geomagnetic activity influence on cardiological cases  

Microsoft Academic Search

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

Christos Katsavrias

2010-01-01

241

Laschamp and Mono Lake geomagnetic excursions recorded in New Zealand  

Microsoft Academic Search

Eight basaltic lavas from the Auckland volcanic field, New Zealand, record three distinct sets of excursional geomagnetic field directions and low paleointensities, however the timing and therefore paleomagnetic significance of these records have been poorly understood. Radiocarbon, K–Ar, and thermoluminescence dating constrain these lavas to have erupted during the last 75 ka, a period during which as many as three excursions

William S. Cassata; Brad S. Singer; John Cassidy

2008-01-01

242

Geomagnetic excursion captured by multiple volcanoes in a monogenetic field  

Microsoft Academic Search

Five monogenetic volcanoes within the Quaternary Auckland volcanic field are shown to have recorded a virtually identical but anomalous paleomagnetic direction (mean inclination and declination of 61.7° and 351.0°, respectively), consistent with the capture of a geomagnetic excursion. Based on documented rates of change of paleomagnetic field direction during excursions this implies that the volcanoes may have all formed within

John Cassidy

2006-01-01

243

Laschamp and Mono Lake geomagnetic excursions recorded in New Zealand  

Microsoft Academic Search

Eight basaltic lavas from the Auckland volcanic field, New Zealand, record three distinct sets of excursional geomagnetic field directions and low paleointensities, however the timing and therefore paleomagnetic significance of these records have been poorly understood. Radiocarbon, K Ar, and thermoluminescence dating constrain these lavas to have erupted during the last 75 ka, a period during which as many as

William S. Cassata; Brad S. Singer; John Cassidy

2008-01-01

244

Laschamp and Mono Lake Geomagnetic Excursions Recorded in New Zealand  

Microsoft Academic Search

Eight basaltic lavas from the Auckland Volcanic Field, New Zealand, record three distinct sets of excursional geomagnetic field directions with low paleointensities, however the timing and therefore paleomagnetic significance of these records have been poorly understood. Radiocarbon, K-Ar, and thermoluminescence dating constrain these lavas to have erupted during the last 75 ka, a period during which at least three excursions

W. Cassata; B. S. Singer; J. Cassidy

2007-01-01

245

The Physics of Geomagnetic-Field Transduction in Animals  

Microsoft Academic Search

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

Michael Winklhofer

2009-01-01

246

Methodology for simulation of geomagnetically induced currents in power systems  

NASA Astrophysics Data System (ADS)

To assess the geomagnetic hazard to power systems it is useful to be able to simulate the geomagnetically induced currents (GIC) that are produced during major geomagnetic disturbances. This paper examines the methodology used in power system analysis and shows how it can be applied to modelling GIC. Electric fields in the area of the power network are used to determine the voltage sources or equivalent current sources in the transmission lines. The power network can be described by a mesh impedance matrix which is combined with the voltage sources to calculate the GIC in each loop. Alternatively the power network can be described by a nodal admittance matrix which is combined with the sum of current sources into each node to calculate the nodal voltages which are then used to calculate the GIC in the transmission lines and GIC flowing to ground at each substation. Practical calculations can be made by superposition of results calculated separately for northward and eastward electric fields. This can be done using magnetic data from a single observatory to calculate an electric field that is a uniform approximation of the field over the area of the power system. It is also shown how the superposition of results can be extended to use data from two observatories: approximating the electric field by a linear variation between the two observatory locations. These calculations provide an efficient method for simulating the GIC that would be produced by historically significant geomagnetic storm events.

Boteler, David

2014-07-01

247

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

248

Geomagnetic control of polar mesosphere summer echoes , P. Homann1  

E-print Network

of Tromsù, The Auroral Observatory, N-9037 Tromsù, Norway Received: 26 May 1999 / Revised: 17 August 1999 in dependence on geomagnetic K indices derived at the Auroral Observa- tory Tromsù (69.66°N, 18.94°E). During. Key words: Ionosphere (auroral ionosphere) ± Magnetospheric physics (energetic particles

Boyer, Edmond

249

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

250

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

251

Altitude Dependence of Neutral Density Geomagnetic Storm Response  

NASA Astrophysics Data System (ADS)

New formulations for satellite neutral density response to geomagnetic activity developed for the Jacchia-Bowman 2008 empirical model were based on data at GRACE altitudes and are applicable for large geomagnetic storms (ap>75). Storm response from the Jacchia-Bowman 2008 and NRLMSIS empirical models are tested at low satellite altitudes using a unique historic set of accelerometer neutral density data from satellites flown in 1982-1983 with perigee altitudes near 170 km. These data are particularly important for evaluating the capability of modern empirical and first principles models to predict satellite drag affecting reentry. The model validations are compared with those of selected CHAMP and GRACE data, 2002-2005, for similar conditions of geomagnetic activity, solar flux, local time and day of year to validate the altitude dependence of geomagnetic heating. Results are interpreted in the framework of General Circulation Models. To further understand thermospheric responses to solar wind energy deposition, we estimate the energy input required to produce these neutral density enhancements.

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

2010-12-01

252

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

253

Simulations of the equatorial thermosphere anomaly: Geomagnetic activity modulation  

NASA Astrophysics Data System (ADS)

The modulation of geomagnetic activity on the equatorial thermosphere anomaly (ETA) in thermospheric temperature under the high solar activity condition is investigated using the Thermosphere Ionosphere Electrodynamics General Circulation Model simulations. The model simulations during the geomagnetically disturbed interval, when the north-south component of the interplanetary magnetic field (Bz) oscillates between southward and northward directions, are analyzed and also compared with those under the quiet time condition. Our results show that ionospheric electron densities increase greatly in the equatorial ionization anomaly (EIA) crest region and decrease around the magnetic equator during the storm time, resulting from the enhanced eastward electric fields. The impact of both the direct heat deposition at high latitudes and the modulation of the storm time enhanced EIA crests on the ETA are subsequently studied. The increased plasma densities over the EIA crest region enhance the field-aligned ion drag that accelerates the poleward meridional winds and consequently their associated adiabatic cooling effect. This process alone produces a deeper temperature trough over the magnetic equator as a result of the enhanced divergence of meridional winds. Moreover, the enhanced plasma-neutral collisional heating at higher latitudes associated with the ionospheric positive storm effect causes a weak increase of the ETA crests. On the other hand, strong changes of the neutral temperature are mainly confined to higher latitudes. Nevertheless, the changes of the ETA purely due to the increased plasma density are overwhelmed by those associated with the storm time heat deposition, which is the major cause of an overall elevated temperature in both the ETA crests and trough during the geomagnetically active period. Associated with the enhanced neutral temperature at high latitudes due to the heat deposition, the ETA crest-trough differences become larger under the minor geomagnetic activity condition than under the quiet time condition. However, when geomagnetic activity is further elevated, the ETA crests tend to be masked by high temperatures at middle and high latitudes.

Lei, Jiuhou; Wang, Wenbin; Thayer, Jeffrey P.; Luan, Xiaoli; Dou, Xiankang; Burns, Alan G.; Solomon, Stanley C.

2014-08-01

254

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

Microsoft Academic Search

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

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

2009-01-01

255

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

PubMed

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

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

2015-04-01

256

Seasonal dependence of magnetic field variations from subauroral latitude to the magnetic equator during geomagnetic sudden commencements  

NASA Astrophysics Data System (ADS)

Seasonal dependence of diurnal variation of the main impulse (MI) of geomagnetic sudden commencements (SCs) has been investigated using the long-tern geomagnetic field data with high time resolution of 1 sec within a period from 1996 to 2008 provided from the NSWM [Kikuchi et al., 2008] and CPMN [Yumoto and the CPMN group, 2001] chains and the WDC for Geomagnetism, Kyoto. In the present analysis, we used the geomagnetic field data obtained from the 10 stations. In this study, we defined an SC phenomenon as a rapid increase of the SYM-H value with more than 5 nT and time variation in the SYM-H index. Then, we identified 3163 events of SCs in a period from January 1996 to 2008, which has no Pi 2 signature around 10 minutes at the SC onset. Moreover, the SC amplitude obtained at the above 10 stations has been normalized by that in the SYM-H index with latitude correction in order to minimize the different contribution of the rapid change in solar wind dynamic pressure. As a result, in sub-auroral (ZYK) and middle latitudes (MMB) tends to be larger in summer than in winter in all the magnetic local time. The peak-to-peak amplitude in the daytime sector strongly depends on solar zenith angle. These result imply that ionospheric currents (ICs) and field-aligned currents (FACs) generated during the MI phase of SC are enhanced due to the increase of ionospheric conductivity in summer. This feature suggests that SC current system is the voltage generator. On the other hand, the sesonal variation of SC amplitude in both the low latitude and magnetic equator showed quite a different signature from that in the sub-auroral and middle latitudes. The remarkable feature is that the equatorial enhancement of SC amplitude due to an intensification of the Pedersen currents via the Cowling effect tends to become smaller in summer, compared with that in winter. This tendency suggests that ionospheric conductivity does not depend on only the solar zenith angle. One of the implications of the equatorial seasonal dependence is that the ionospheric conductivity in the low latitude and at the magnetic equator modifies the variation of ionospheric structure around the E-region due to neutral drag of the ionospheric plasma along the magnetic field line via interaction between the meridional neutral wind and ionospheric E-region plasmas. Therefore, in order to verify the existence of the neutral wind and its seasonal dependence, we will need to analyze the thermospheric wind data obtained from the MF and meteor radars provided from the IUGONET database.

Shinbori, A.; Tsuji, Y.; Kikuchi, T.; Araki, T.; Ikeda, A.; Uozumi, T.; Solovyev, S. I.; Shevtsov, B.; Otadoy, R. S.; Utada, H.; Nagatsuma, T.; Hayashi, H.; Tsuda, T.; Yumoto, K.; Iugonet Project Team

2010-12-01

257

Preliminary Analysis on the Interplanetary Cause of Geomagnetically Induced Current and Its Effect on Power Systems  

NASA Astrophysics Data System (ADS)

Using the detected events of geomagnetically induced current (GIC) in the Ling'ao nuclear power plant from 2004 to 2005, and focusing on the interplanetary cause of GIC and its effect on power systems, we have analyzed the corresponding solar driving sources and interplanetary solar wind structures, and performed spectral analysis on the most intense GIC event by means of wavelet transform. The results of this study show that: (1) Most GIC events were driven mainly by the halo coronal mass ejections, the interplanetary cause of GIC events includes the shock sheath, magnetic cloud, and multiplex interplanetary solar wind structure. (2) Based on the strongest GIC event on 2001 November 9, we find that the fluctuation of GIC in the earlier stage was related to the magnetic cloud boundary layer, and the variation of GIC intensity in the later stage was caused by magnetic cloud itself. (3) Compared to the frequency of the power system (50 Hz), the GIC can be equivalent to a quasi direct current. The energy of the GIC is embodied in the two time intervals in the wavelet power spectrum: the first interval is shown as an impulsive type and with a weaker intensity, and the second one is stronger. Regarding to the cumulative time of the transformer temperature rise caused by GIC, the second interval has a longer duration than the first one. Hence, during the second interval, it is more harmful to the power systems and devices. (4) With a correlation analysis, the correlations of the SYM-H index and dBx/dt with the GIC are significantly stronger than those of other geomagnetic indices with the GIC.

Kai-rang, WANG; Lian-guang, LIU; Yan, LI

2015-01-01

258

An empirical probability density distribution of planetary ionosphere storms with geomagnetic precursors  

NASA Astrophysics Data System (ADS)

The probability of occurrence of the positive and negative planetary ionosphere storms is evaluated using the W index maps produced from Global Ionospheric Maps of Total Electron Content, GIM-TEC, provided by Jet Propulsion Laboratory, and transformed from geographic coordinates to magnetic coordinates frame. The auroral electrojet AE index and the equatorial disturbance storm time Dst index are investigated as precursors of the global ionosphere storm. The superposed epoch analysis is performed for 77 intense storms (Dst?-100 nT) and 227 moderate storms (-100index and Dst index. It is found that AE index better suits to serve as a precursor of the ionosphere storm than Dst index with onset of the average auroral AE storm occurring 6 h before the equatorial Dst storm onset for intense storms and 3 h in advance of moderate Dst storm. The similar space zones advancement of the ionosphere storm is observed with W index (pW+ and pW-) depicting maximum localized in the polar magnetic zone and minimum at magnetic equator. An empirical relation for pW+ and pW- with AE storm precursor is derived which enables the probability of occurrence of the ionosphere storm to be predicted with leading time of 1-2 h for the positive ionosphere storm and 9-10 h for the negative ionosphere storm. The ionosphere storm probability model is validated using data for 2 intense and 20 moderate geomagnetic storms occurred during 2013. Results are discussed in the paper. This study is supported by the joint grant of TUBITAK 112E568 and RFBR 13-02-91370-CT_a.

Gulyaeva, Tamara; Stanislawska, Iwona; Arikan, Feza; Arikan, Orhan

259

Orbit of 1976 AA. [asteroid  

NASA Technical Reports Server (NTRS)

The orbit of Asteroid 1976 AA is described, with attention given to calculations of its period and its distance from earth, both of which could be accurately and quickly determined by measuring the minor planet's position over wide ranges of hour angle on one to three nights. The geometry of the asteroid's orbit is compared to that of earth's orbit, and the periodicity of the minor planet's approaches to earth is projected. The motion of 1976 AA over an interval of seven centuries into both past and future is also studied; the possibility of its libration with respect to earth or to Venus is examined. Some data on closest approaches of the asteroid to Mars and Venus, as well as to earth, are given.

Marsden, B. G.; Williams, J. G.

1977-01-01

260

-Dispersed AA7075 Alloy Composites  

NASA Astrophysics Data System (ADS)

TiO2-dispersed AA7075 alloy composites were produced by mechanical milling followed by hot uniaxial compaction and sintering. The effects of volume fraction and dispersoid size on precipitation kinetics, densification, and hardness of the composites were studied in detail. While the sinterability of the composites decreases with increasing volume fraction of the particulate reinforcement (dispersoid), the same increases with decreasing particle size of the reinforcement. Microstructural analysis using X-ray diffraction and scanning electron microscopy shows an improvement in the distribution of reinforcement with decreasing particle size. The hardness of the composites increases with increasing volume fraction and decreasing TiO2 particle size. Further, the reinforced composites do not show age hardenability unlike unreinforced AA7075 alloy. Microstructural analysis reveals the formation of MgTiO3 and ZnO near the TiO2-AA7075 interface, which suppresses the formation of Guinier-Preston (GP) zone resulting in no age hardenability of the composites.

Karunanithi, R.; Ghosh, K. S.; Bera, Supriya

2014-08-01

261

Dynamic Modeling of Solar Energetic Particle Cutoffs During Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

We investigate numerically the relationship between time variations in the geomagnetic cutoff and prompt trapping of Solar Energetic Particles inside the pre-storm cutoff, which form new radiation belt populations distinct from the CRAND-produced inner zone. This is done for several CME-shock initiated geomagnetic storms including the 14 July 2000, 24 Nov 2001, and 21-23 April 2002 storms. Following Smart and Shea [2000], Solar Energetic Particle (SEP) access is determined by computing the reverse particle trajectories. Magnetospheric fields are obtained from the Lyon-Feder-Mobarry (LFM) global MHD model, which is driven by measured solar wind parameters at the sunward boundary. We find well-defined surfaces of constant cutoff that exhibit dynamic behavior in response to solar wind conditions. The results suggest that an enhanced solar wind dynamic pressure plays a direct role in the observed ion injections. Additional mechanisms for SEP access and trapping are considered, including the the role of ULF waves.

Kress, B. T.; Hudson, M. K.; Perry, K. L.

2003-12-01

262

Observation of Ground Level Muons at Two Geomagnetic Locations  

NASA Astrophysics Data System (ADS)

Two extensive measurements of ground level muons were performed with the NMSU-WIZARD/CAPRICE magnet spectrometer at Lynn Lake, Manitoba, Canada and Fort Sumner, New Mexico, USA, in July 1994 and spring 1997, respectively. The spectrometer was equipped with a superconducting magnet, a time-of-flight system, an electromagnetic calorimeter and a Ring Imaging Cherenkov (RICH) detector. Two different versions of the RICH were used: one with a solid NaF radiator in 1994 and one with a gaseous C4 F10 radiator in 1997. Both the muon spectrum and the + to , ratio are presented in the momentum range from 200 MeV/c to 120 GeV/c for the two different geomagnetic locations. The spectra are compared with previous experimental results. The data show latitude dependent geomagnetic effects.

Kremer, Jens

263

Inferring interplanetary magnetic field polarities from geomagnetic variations  

NASA Astrophysics Data System (ADS)

In this paper, we propose a modified procedure to infer the interplanetary magnetic field (IMF) polarities from geomagnetic observations. It allows to identify the polarity back to 1905. As previous techniques it is based on the well-known Svalgaard-Mansurov effect. We have improved the quality and accuracy of polarity inference compared with the previous results of Svalgaard (1975) and Vennerstroem et al. (2001) by adding new geomagnetic stations and extracting carefully diurnal curve. The data demonstrates an excess of one of the two IMF sectors within equinoxes (Rosenberg-Coleman rule) evidencing polar field reversals at least for the last eight solar cycles. We also found a predominance of the two-sector structure in late of descending phase of solar cycle 16.

Vokhmyanin, M. V.; Ponyavin, D. I.

2012-06-01

264

Laboratory Astrophysics Division of The AAS (LAD)  

NASA Astrophysics Data System (ADS)

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.

2012-10-01

265

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

266

Geomagnetic Paleointensity Recorded In The Khonako-3 Section, Tajikistan  

Microsoft Academic Search

The geomagnetic intensity recorded in the Khonako-3 loess section (j=38î.02'N, l=70î.03'E), Tajikistan was studied in the upper 18 m of the section including a buried soil complex (BSC-1). Analysis of the inferred curves Js(T), Jrs(T), Jr(H) and Jn(T) showed magnetite to be the main magnetization carrier in the loesses and BSC-1 com- plex. Nearly linear dependences ARM(K) and Jrs(K) indicate

G. Pospelova; O. Pilipenko; S. Laukhin

2002-01-01

267

Space Weather Monitoring for ISS Geomagnetic Storm Studies  

NASA Technical Reports Server (NTRS)

The International Space Station (ISS) space environments community utilizes near real time space weather data to support a variety of ISS engineering and science activities. The team has operated the Floating Potential Measurement Unit (FPMU) suite of plasma instruments (two Langmuir probes, a floating potential probe, and a plasma impedance probe) on ISS since 2006 to obtain in-situ measurements of plasma density and temperature along the ISS orbit and variations in ISS frame potential due to electrostatic current collection from the plasma environment (spacecraft charging) and inductive (vxB) effects from the vehicle motion across the Earth s magnetic field. An ongoing effort is to use FPMU for measuring the ionospheric response to geomagnetic storms at ISS altitudes and investigate auroral charging of the vehicle as it passes through regions of precipitating auroral electrons. This work is challenged by restrictions on FPMU operations that limit observation time to less than about a third of a year. As a result, FPMU campaigns ranging in length from a few days to a few weeks are typically scheduled weeks in advance for ISS engineering and payload science activities. In order to capture geomagnetic storm data under these terms, we monitor near real time space weather data from NASA, NOAA, and ESA sources to determine solar wind disturbance arrival times at Earth likely to be geoeffective (including coronal mass ejections and high speed streams associated with coronal holes) and activate the FPMU ahead of the storm onset. Using this technique we have successfully captured FPMU data during a number of geomagnetic storm periods including periods with ISS auroral charging. This presentation will describe the strategies and challenges in capturing FPMU data during geomagnetic storms, the near real time space weather resources utilized for monitoring the space weather environment, and provide examples of auroral charging data obtained during storm operations.

Minow, Joseph I.; Parker, Neergaard

2013-01-01

268

Correlation of Occurrence of Whistlers with Geomagnetic Activities  

Microsoft Academic Search

IN order to study the correlation of geomagnetic activities with the frequency of occurrences of whistlers, I have investigated the I.G.Y. and I.G.C. data for 2 years, that is, July 1, 1957-June 30, 1959, at the stations Toyokawa (geogr. co-ord. 34° 50' N., 137° 22' E. ; geomag. co-ord. 24.5°, 203.5°) and Wakkanai (geogr. co-ord. 45° 22' N., 141° 41'

Atsushi Kimpara

1960-01-01

269

Types and Characteristics of Data for Geomagnetic Field Modeling  

NASA Technical Reports Server (NTRS)

Given here is material submitted at a symposium convened on Friday, August 23, 1991, at the General Assembly of the International Union of Geodesy and Geophysics (IUGG) held in Vienna, Austria. Models of the geomagnetic field are only as good as the data upon which they are based, and depend upon correct understanding of data characteristics such as accuracy, correlations, systematic errors, and general statistical properties. This symposium was intended to expose and illuminate these data characteristics.

Langel, R. A. (editor); Baldwin, R. T. (editor)

1992-01-01

270

Impact of geomagnetic excursions on atmospheric chemistry and dynamics  

NASA Astrophysics Data System (ADS)

Geomagnetic excursions, i.e. short periods in time with much weaker geomagnetic fields and substantial changes in the position of the geomagnetic pole, occurred repeatedly in the Earth's history, e.g. the Laschamp event about 41 kyr ago. Although the next such excursion is certain to come, little is known about the timing and possible consequences for the state of the atmosphere and the ecosystems. Here we use the global chemistry climate model SOCOL-MPIOM to simulate the effects of geomagnetic excursions on atmospheric ionization, chemistry and dynamics. Our simulations show significantly increased concentrations of nitrogen oxides (NOx) in the entire stratosphere, especially over Antarctica (+15%), due to enhanced ionization by galactic cosmic rays. Hydrogen oxides (HOx) are also produced in greater amounts (up to +40%) in the tropical and subtropical lower stratosphere, while their destruction by reactions with enhanced NOx prevails over the poles and in high altitudes (by -5%). Stratospheric ozone concentrations decrease globally above 20 km by 1-2% and at the northern hemispheric tropopause by up to 5% owing to the accelerated NOx-induced destruction. A 5% increase is found in the southern lower stratosphere and troposphere. In response to these changes in ozone and the concomitant changes in atmospheric heating rates, the Arctic vortex intensifies in boreal winter, while the Antarctic vortex weakens in austral winter and spring. Surface wind anomalies show significant intensification of the southern westerlies at their poleward edge during austral winter and a pronounced northward shift in spring. Major impacts on the global climate seem unlikely.

Suter, I.; Zech, R.; Anet, J. G.; Peter, T.

2014-06-01

271

Wavelet analysis of relative geomagnetic paleointensity at ODP Site 983  

Microsoft Academic Search

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

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

2000-01-01

272

The geomagnetically trapped radiation environment: A radiological point of view  

NASA Technical Reports Server (NTRS)

The regions of naturally occurring, geomagnetically trapped radiation are briefly reviewed in terms of physical parameters such as; particle types, fluxes, spectrums, and spatial distributions. The major emphasis is placed upon a description of this environment in terms of the radiobiologically relevant parameters of absorbed dose and dose-rate and a discussion of the radiological implications in terms of the possible impact on space vehicle design and mission planning.

Holly, F. E.

1972-01-01

273

Analysis of the 3-7 October 2000 and 15-24 April 2002 geomagnetic storms with an optimized nonlinear dynamical model  

NASA Astrophysics Data System (ADS)

A computationally optimized low dimensional nonlinear dynamical model of the magnetosphere-ionosphere system called WINDMI is used to analyze two large geomagnetic storm events 3-7 October 2000 and 15-24 April 2002 These two important storms share common features such as the passage of magnetic clouds shock events from coronal mass ejections triggered substorms and intervals of sawtooth oscillations Sawtooth oscillations resemble periodic substorms but occur in association with strong or building ring current populations and have injection regions that are unusually close to Earth and unusually wide in magnetic local times The April 2002 event includes one of the best examples of sawtooth events ever observed On 18 April 2002 sawtooth oscillations were clearly visible when solar wind conditions IMF Bz density pressure were relatively steady with a slowly varying Dst In this study WINDMI is used to model the 3-7 October 2000 and 15-24 April 2002 geomagnetic activity WINDMI results are evaluated focusing on the sawtooth intervals and the overall prediction of the westward auroral electrojet AL index and Dst index The input to the model is the dynamo driving voltage derived from the fluctuating solar wind plasma and the interplanetary magnetic field measured by the ACE satellite The output of the model is a field aligned current proportional to the AL index and the energy stored in the ring current which is proportional to the Dst index The model parameters are optimized using a genetic algorithm GA to obtain solutions that simultaneously have least mean

Horton, W.; Spencer, E.; Mays, L.; Doxas, I.; Kozyra, J.

274

Evidence that pigeons orient to geomagnetic intensity during homing.  

PubMed

The influence of the Earth's magnetic field on locomotory orientation has been studied in many taxa but is best understood for homing pigeons (Columba livia). Effects of experimentally induced and naturally occurring perturbations in the geomagnetic field suggest that pigeons are sensitive to changes in geomagnetic parameters. However, whether pigeons use the Earth's magnetic field for position determination remains unknown. Here we report an apparent orientation to the intensity gradient of the geomagnetic field observed in pigeons homing from sites in and around a magnetic anomaly. From flight trajectories recorded by GPS-based tracking devices, we noted that many pigeons released at unfamiliar sites initially flew, in some cases up to several kilometres, in directions parallel and/or perpendicular to the bearing of the local intensity field. This behaviour occurred irrespective of the homeward direction and significantly more often than what was expected by random chance. Our study describes a novel behaviour which provides strong evidence that pigeons when homing detect and respond to spatial variation in the Earth's magnetic field--information of potential use for navigation. PMID:17301015

Dennis, Todd E; Rayner, Matt J; Walker, Michael M

2007-05-01

275

Recent developments in the global geomagnetic observatory network  

NASA Astrophysics Data System (ADS)

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

Chulliat, A.

2011-12-01

276

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. PMID:23297205

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

2013-01-01

277

Evidence that pigeons orient to geomagnetic intensity during homing  

PubMed Central

The influence of the Earth's magnetic field on locomotory orientation has been studied in many taxa but is best understood for homing pigeons (Columba livia). Effects of experimentally induced and naturally occurring perturbations in the geomagnetic field suggest that pigeons are sensitive to changes in geomagnetic parameters. However, whether pigeons use the Earth's magnetic field for position determination remains unknown. Here we report an apparent orientation to the intensity gradient of the geomagnetic field observed in pigeons homing from sites in and around a magnetic anomaly. From flight trajectories recorded by GPS-based tracking devices, we noted that many pigeons released at unfamiliar sites initially flew, in some cases up to several kilometres, in directions parallel and/or perpendicular to the bearing of the local intensity field. This behaviour occurred irrespective of the homeward direction and significantly more often than what was expected by random chance. Our study describes a novel behaviour which provides strong evidence that pigeons when homing detect and respond to spatial variation in the Earth's magnetic field—information of potential use for navigation. PMID:17301015

Dennis, Todd E; Rayner, Matt J; Walker, Michael M

2007-01-01

278

Geomagnetic field variability during the Cretaceous Normal Superchron  

NASA Astrophysics Data System (ADS)

Prolonged periods of stable polarity in the Earth's magnetic field are termed superchrons. The most recent of these intervals, the Cretaceous Normal Superchron, lasted from approximately 121 to 83 million years ago and is most commonly observed in the lack of a prominent stripe pattern in the sea-surface magnetic anomaly above the oceanic crust formed during this period. The exact behaviour of the geomagnetic field during this interval, however, remains unclear, as palaeomagnetic data from igneous and sedimentary sections yield conflicting results. Here we report a deep-tow magnetic profile from the Central Atlantic Ocean, African flank, spanning the entire Cretaceous Normal Superchron. We suggest that this profile, along with widely distributed sea-surface magnetic anomaly data, records the rising variability of the dipolar geomagnetic field at the beginning of the interval, which culminates in a highly fluctuating field between 110 and 100 million years ago. We interpret the subdued magnetic signal in the last 9 million years of the superchron as the return to a more stable geomagnetic field. This variability allows us to define two internal time markers valuable for plate reconstructions. Based on the degree of variability observed, we conclude that geodynamo models that call for low field variability may provide an oversimplified view of superchrons.

Granot, Roi; Dyment, Jérôme; Gallet, Yves

2012-03-01

279

Variations of solar, interplanetary, and geomagnetic parameters with solar magnetic multipole fields during Solar Cycles 21-24  

NASA Astrophysics Data System (ADS)

In this study we compare the temporal variations of the solar, interplanetary, and geomagnetic (SIG) parameters with that of open solar magnetic flux from 1976 to 2012 (from Solar Cycle 21 to the early phase of Cycle 24) for a purpose of identifying their possible relationships. By the open flux, we mean the average magnetic field over the source surface (2.5 solar radii) times the source area as defined by the potential field source surface (PFSS) model of the Wilcox Solar Observatory (WSO). In our result, most SIG parameters except the solar wind dynamic pressure show rather poor correlations with the open solar magnetic field. Good correlations are recovered when the contributions from individual multipole components are counted separately. As expected, solar activity indices such as sunspot number, total solar irradiance, 10.7 cm radio flux, and solar flare occurrence are highly correlated with the flux of magnetic quadrupole component. The dynamic pressure of solar wind is strongly correlated with the dipole flux, which is in anti-phase with Solar Cycle (SC). The geomagnetic activity represented by the Ap index is correlated with higher order multipole components, which show relatively a slow time variation with SC. We also found that the unusually low geomagnetic activity during SC 23 is accompanied by the weak open solar fields compared with those in other SCs. It is argued that such dependences of the SIG parameters on the individual multipole components of the open solar magnetic flux may clarify why some SIG parameters vary in phase with SC and others show seemingly delayed responses to SC variation.

Kim, Bogyeong; Lee, Jeongwoo; Yi, Yu; Oh, Suyeon

2015-01-01

280

Doppler effects in the high-latitude ionospere during observations geomagnetic pulsations  

Microsoft Academic Search

In this paper the interrelation between geomagnetic pulsations and variations in frequency Doppler shift fd of the ionosphere-reflected radio signal is under investigation. The experiment on simultaneous recording of fd variations and geomagnetic pulsations was organised at high latitude station in Norilsk (geomagnetic latitude and longitude 64.2°N, 160.4° E, L=5.3) during Febrary–April of 1995–98. Thirty cases of simultaneous recording of

Yu. V. Lipko; A. Yu. Pashinin; R. A. Rakhmatulin

2002-01-01

281

The geomagnetic field - An explanation for the microturbulence in coaxial gun plasmas  

NASA Technical Reports Server (NTRS)

The complexity introduced by the geomagnetic field in several regions of a coaxial gun plasma device is described. It is shown that the annihilation of the swept-up geomagnetic flux, trapped within the highly compressed turbulent plasma, provides an explanation for varied performance and experimental results. The results indicate that the device should be aligned along the direction of the local geomagnetic field or enclosed in a mu-metal shield.

Mather, J. W.; Ahluwalia, H. S.

1988-01-01

282

The Development of a Dynamic Geomagnetic Cutoff Rigidity Model for the International Space Station  

NASA Technical Reports Server (NTRS)

We have developed a computer model of geomagnetic vertical cutoffs applicable to the orbit of the International Space Station. This model accounts for the change in geomagnetic cutoff rigidity as a function of geomagnetic activity level. This model was delivered to NASA Johnson Space Center in July 1999 and tested on the Space Radiation Analysis Group DEC-Alpha computer system to ensure that it will properly interface with other software currently used at NASA JSC. The software was designed for ease of being upgraded as other improved models of geomagnetic cutoff as a function of magnetic activity are developed.

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

1999-01-01

283

Geomagnetic storms prediction from InterMagnetic Observatories data using the Multilayer Perceptron neural network  

NASA Astrophysics Data System (ADS)

In this paper, a tentative of geomagnetic storms prediction is implanted by analyzing the International Real-Time Magnetic Observatory Network data using the Artificial Neural Network (ANN). The implanted method is based on the prediction of future horizontal geomagnetic field component using a Multilayer Perceptron (MLP) neural network model. The input is the time and the output is the X and Y magnetic field components. Application to geomagnetic data of Mai 2002 shows that the implanted ANN model can greatly help the geomagnetic storms prediction.

Ouadfeul, S.; Aliouane, L.; Tourtchine, V.

2013-09-01

284

Immigration Index  

NSDL National Science Digital Library

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

285

Marine Magnetic Anomalies, Oceanic Crust Magnetization, and Geomagnetic Time Variations  

NASA Astrophysics Data System (ADS)

Since the classic paper of Vine and Matthews (Nature, 1963), marine magnetic anomalies are commonly used to date the ocean floor through comparison with the geomagnetic polarity time scale and proper identification of reversal sequences. As a consequence, the classical model of rectangular prisms bearing a normal / reversed magnetization has been dominant in the literature for more than 40 years. Although the model explains major characteristics of the sea-surface magnetic anomalies, it is contradicted by (1) recent advances on the geophysical and petrologic structure of the slow-spreading oceanic crust, and (2) the observation of short-term geomagnetic time variations, both of which are more complex than assumed in the classical model. Marine magnetic anomalies may also provide information on the magnetization of the oceanic crust as well as short-term temporal fluctuations of the geomagnetic field. The "anomalous skewness", a residual phase once the anomalies have been reduced to the pole, has been interpreted either in terms of geomagnetic field variations or crustal structure. The spreading-rate dependence of anomalous skewness rules out the geomagnetic hypothesis and supports a spreading-rate dependent magnetic structure of the oceanic crust, with a basaltic layer accounting for most of the anomalies at fast spreading rates and an increasing contribution of the deeper layers with decreasing spreading rate. The slow cooling of the lower crust and uppermost mantle and serpentinization, a low temperature alteration process which produces magnetite, are the likely cause of this contribution, also required to account for satellite magnetic anomalies over oceanic areas. Moreover, the "hook shape" of some sea-surface anomalies favors a time lag in the magnetization acquisition processes between upper and lower magnetic layers: extrusive basalt acquires a thermoremanent magnetization as soon as emplaced, whereas the underlying peridotite and olivine gabbro cool slowly and pass through serpentinization to bear a significant magnetization. Our analysis of the amplitude of Anomaly 25 shows a sharp threshold at the spreading rate of 30 km/Ma, which corresponds to the transition between oceanic lithosphere built at axial domes and axial valleys. The twice lower amplitudes are in agreement with a much disrupted and altered basaltic layer at slow rates and a significant contribution from the deeper layers. Oceanic lithosphere created at fast and slow spreading rates therefore exhibits contrasted magnetic structures. High resolution magnetic anomaly measurements carried out with deep tows and submersibles show that the magmatic (fast spreading and parts of the slow spreading) crust is a good recorder of short-term geomagnetic time variations, such as short polarity intervals, excursions, or paleointensity variations. Surface and deep-sea magnetic anomalies therefore help to confirm or infirm geomagnetic findings obtained by other means. Many excursions and paleointensity variations within Brunhes and Matuyama periods are confirmed, but the "saw tooth pattern" inferred from sediment cores - a possible candidate to explain the anomalous skewness - is not, which suggests a bias in the sedimentary approach.

Dyment, J.; Arkani-Hamed, J.

2005-12-01

286

DIVISION CATEGORY DESCRIPTION ITEM DESCRIPTION AA Advertise Advertising for courses  

E-print Network

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

Rainforth, Emma C.

287

Page 1 AA May 7, 2008 Francis Everitt  

E-print Network

, then there is no hope for it." -- A. Einstein ( ) ( ) -+×= R R vR 23232 3 2 3 RRc GI Rc GM · Basic formula: · Oblateness correction: * Dan Wilkins (Physics), John Breakwell (AA) Leonard Schiff Quartz block Gyro 1 Gyro 2) - Cannon (AA) FE (Physics), Dan DeBra, Dick Van Patten ( AA) John Lipa (Physics), John Nikirk (AA) Joint AA

Prinz, Friedrich B.

288

Analysis of the October 3-7 2000 and April 15-24 2002 Geomagnetic Storms with the WINDMI model  

NASA Astrophysics Data System (ADS)

A computationally optimized model of the magnetosphere-ionosphere system called WINDMI is used to analyze two large geomagnetic storm events, Oct 3-7 2000 and Apr 15-24 2002. These two storms share common features such as the passage of a magnetic cloud, shock events and the occurrence of periodic substorms. The input into the model is a driving voltage derived from the solar wind dynamic pressure and the interplanetary magnetic field measured by the ACE satellite. Two key outputs of the model are (1) the nightside field aligned region 1 current that closes in the auroral ionosphere giving the AL index from the westward electroject and (2) the total energy in the ring current plasma driven by the plasma sheet with losses from the charge exchange of the fast ions which is then converted to the ground based Dst signal through the Dessler-Parker-Schopke relationship. The model parameters are optimized using a genetic algorithm to search for solutions that simultaneously have least mean square fit to the AL and Dst indices and also possess substorms of period 2-4 hours. Good results have been obtained for both geomagnetic storm periods.

Spencer, E. A.; Horton, W. C.; Doxas, I.; Kozyra, J. U.

2005-12-01

289

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

PubMed

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. PMID:25089071

Rice, Samara Lloyd; Tonigan, J Scott

2012-01-01

290

An analysis of the solar wind parameters responsible for the main phase of the super geomagnetic storm on March 31, 2001  

NASA Astrophysics Data System (ADS)

In this paper, the solar wind parameters responsible for the main phase of the super geomagnetic storm occurred on March 31, 2001 is analyzed taking into account the delayed geomagnetic effect of solar wind at the L1 point and using the SYM-H index. The solar wind responsible for the main phase is split into two periods. The solar wind parameters in the two periods contributed differently to the main phase. A comparative study of solar wind parameters in the two periods shows the evidence that the solar wind density defines energy transfer to the magnetosphere. Analysis is also made to understand a range of key factors that may define the development of the storm's main phase, including the time integral of the southward component of interplanetary magnetic field (IMF) or the solar wind electric field, and a solar wind energy coupling function established by Akasofu (1981). Additionally, the paper discusses the assumption that a strong southward IMF and high inclination to the ecliptic plane would contribute to the occurrence of a super geomagnetic storm, and assesses the rationality behind an empirical formula relating the Dst peak value to solar wind parameters established by Wang Y M et al.(2003). The paper is concluded with a summary of the key solar wind parameters that may define the development of a storm's main phase.

Le, G.; Zheng, L.

2012-12-01

291

Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies  

NASA Technical Reports Server (NTRS)

Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The central polar cap (greater than approx. 80 magnetic latitude) antisunward wind speed is found to be a strong function of both solar and geomagnetic activity. The polar cap temperatures show variations in both solar and geomagnetic activity, with temperatures near 800 K for low K(sub p) and F(sub 10.7) and greater than about 2000 K for high K(sub p) and F(sub 10.7). The observed temperatures are significantly greater than those predicted by the mass spectrometer/incoherent scatter model for high activity conditions. Theoretical analysis based on the NCAR TIGCM indicates that the antisunward upper thermospheric winds, driven by upstream ion drag, basically 'coast' across the polar cap. The relatively small changes in wind velocity and direction within the polar cap are induced by a combination of forcing terms of commensurate magnitude, including the nonlinear advection term, the Coriolis term, and the pressure gradient force term. The polar cap thennospheric thermal balance is dominated by horizontal advection, and adiabatic and thermal conduction terms.

Killeen, T. L.; Won, Y.-I.; Niciejewski, R. J.; Burns, A. G.

1995-01-01

292

MoSST DAS: The First Working Geomagnetic Data Assimilation System  

NASA Technical Reports Server (NTRS)

The Earth possesses an internal magnetic field (geomagnetic field) generated by convection in the outer core (geodynamo). Previous efforts have been focused along two distinct paths: (1) numerical geodynamo modeling to understand the origin of the geomagnetic field, and the mechanisms of geomagnetic secular variations (SV); and (2) geomagnetic field modeling to map the spatial/temporal variations of the field from geomagnetic data, and to derive core properties, e.g. inversion of core flow near the core-mantle boundary (CMB). Geomagnetic data assimilation is a new approach emerged over the past 5 years: surface observations are assimilated with geodynamo models for better understanding of the core dynamical state, and accurately prediction of SV. In collaboration with several geomagnetic research groups, we have developed the first working geomagnetic data assimilation system, Modular, Scalable, Self-consistent, and Three-dimensional (MoSST) DAS, that includes the MoSST numerical dynamo model; 7000 years of geomagnetic field maps from several field models utilizing satellite and ground observatory data, historical magnetic records and archeo/paleo magnetic data; and an ensemble based optimal interpolation (01) assimilation algorithm. With this system, we have demonstrated clearly that the assimilated core dynamical state is substantially different from those of pure geodynamo simulations. Ensemble assimilation runs also show the convergence of the assimilated solutions inside the core, suggesting that the simulation state is pulled closer to the truth via data assimilation. The forecasts from this system are also very accurate: the 5-year forecast of the geomagnetic field agrees very well with the observations; and the 5-year secular variation forecast is more accurate than the IGRF SV forecast models in the past. Using geomagnetic records up to 2009, we have made an SV forecast for the period from 2010-2015, and is a candidate SV model for IGRF-11.

Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

2011-01-01

293

Long-term variation in the upper atmosphere as seen in the geomagnetic solar quiet (Sq) daily variation  

NASA Astrophysics Data System (ADS)

It has been well-known that geomagnetic solar quiet (Sq) daily variation is produced by the global ionospheric currents flowing in the E-region, which are generated by dynamo process via interaction between the neutral wind and ionospheric plasma in a region of the lower thermosphere and ionosphere. Then, to investigate the Sq amplitude is essential for understanding the long-term variations in the ionospheric conductivity and neutral wind of the lower thermosphere and ionosphere. Recently, Elias et al. [2010] reported that the Sq amplitude tends to increase by 5.4-9.9 % in the middle latitudes in a period of 1961-2001. They mentioned that the long-term variation of ionospheric conductivity associated with geomagnetic secular variation mainly determines the Sq trend, but that the rest component is due to ionospheric conductivity enhancement associated with cooling effect in the thermosphere due to increasing greenhouse gas. In the present study, we clarify the characteristics of the long-term variation in the Sq amplitude using the long-term observation data of geomagnetic field and neutral wind. In the present analysis, we used the F10.7 solar flux as a good indicator of the variation in the solar irradiance in the EUV and UV range as well as geomagnetic field data with time resolution of 1 hour observed at 184 geomagnetic stations. The definition of the Sq amplitude is the difference of the H-component between the maximum and minimum every day when the Kp index is less than 4. As a result, the long-term variation in the Sq amplitude at all the geomagnetic stations shows a strong correlation with the solar F10.7 flux which depends on 11-year solar activity. The relationship between the Sq amplitude and F10.7 flux was not linear but nonlinear. This nonlinearity could be interpreted as the decrease of production rate of electrons and ions in the ionosphere for the strong EUV and UV fluxes as already reported by Balan et al. [1993]. In order to minimize the solar activity dependence on the Sq amplitude, we calculated second orders of fitting curve between the F10.7 flux and Sq amplitude during 1950-2011, and examined the residual Sq amplitude defined as the deviation from the fitting curve. The residual Sq amplitude clearly shows increase and decrease trends with the periods of 20 years. Then, it seems that the trends in the residual Sq and Sqp fields are related to the long-term variation in the ionospheric conductivities associated with the secular variation of the ambient magnetic field and the upper atmosphere (for example, plasma and neutral densities). In order to verify qualitatively the above signatures, we need to investigate the long-term variation in the ionospheric conductivities using a calculation tool developed by the IUGONET project.

Shinbori, A.; Koyama, Y.; Yatagai, A. I.; Nose, M.; Hori, T.; Otsuka, Y.

2012-12-01

294

Elgin Community College AAS Degree *Criminal Justice  

E-print Network

Elgin Community College AAS Degree *Criminal Justice Bachelor of Science in Applied Management (3) SOCI 381 Criminology (met by Elgin CRJ 230) (3) SOCI 383 The Criminal Justice System (met credits must be completed through NIU. #12;Elgin Community College AAS Degree *Criminal Justice Academic

Kostic, Milivoje M.

295

Elgin Community College AAS *Criminal Justice  

E-print Network

Elgin Community College AAS Degree *Criminal Justice Bachelor of Science in Applied Management Administration 3 SOCI 381 Criminology (met by Elgin CRJ 230) 3 SOCI 383 The Criminal Justice System (met by Elgin credits must be completed through NIU. #12;Elgin Community College AAS Degree *Criminal Justice Academic

Kostic, Milivoje M.

296

Geodynamo model and error parameter estimation using geomagnetic data assimilation  

NASA Astrophysics Data System (ADS)

We have developed a new geomagnetic data assimilation approach which uses the minimum variance' estimate for the analysis state, and which models both the forecast (or model output) and observation errors using an empirical approach and parameter tuning. This system is used in a series of assimilation experiments using Gauss coefficients (hereafter referred to as observational data) from the GUFM1 and CM4 field models for the years 1590-1990. We show that this assimilation system could be used to improve our knowledge of model parameters, model errors and the dynamical consistency of observation errors, by comparing forecasts of the magnetic field with the observations every 20 yr. Statistics of differences between observation and forecast (O - F) are used to determine how forecast accuracy depends on the Rayleigh number, forecast error correlation length scale and an observation error scale factor. Experiments have been carried out which demonstrate that a Rayleigh number of 30 times the critical Rayleigh number produces better geomagnetic forecasts than lower values, with an Ekman number of E = 1.25 × 10-6, which produces a modified magnetic Reynolds number within the parameter domain with an `Earth like' geodynamo. The optimal forecast error correlation length scale is found to be around 90 per cent of the thickness of the outer core, indicating a significant bias in the forecasts. Geomagnetic forecasts are also found to be highly sensitive to estimates of modelled observation errors: Errors that are too small do not lead to the gradual reduction in forecast error with time that is generally expected in a data assimilation system while observation errors that are too large lead to model divergence. Finally, we show that assimilation of L ? 3 (or large scale) gauss coefficients can help to improve forecasts of the L > 5 (smaller scale) coefficients, and that these improvements are the result of corrections to the velocity field in the geodynamo model.

Tangborn, Andrew; Kuang, Weijia

2015-01-01

297

An overset grid method for global geomagnetic induction  

NASA Astrophysics Data System (ADS)

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

Weiss, Chester J.

2014-07-01

298

Paleomagnetic recording fidelity and understanding geomagnetic field behavior (Invited)  

NASA Astrophysics Data System (ADS)

Analysis of geomagnetic field behavior from sedimentary archives depends crucially on the fidelity with which geomagnetic signals are recorded. Recent developments emphasize the fact that we do not yet have an adequate understanding of sedimentary remanence acquisition. For example, biogenic magnetite, which has ideal single domain magnetic behavior, is now known to be a common, and often dominant, component of the magnetic mineral assemblage of ancient sediments. If biogenic magnetite is produced in the water column or within the bioturbated upper layer of the sediment column, these particles could contribute to a conventionally envisaged depositional remanent magnetization or to a post-depositional remanent magnetization. In contrast, if magnetotactic bacteria live within the sediment below the surface mixed layer, they could contribute to a biogeochemical remanent magnetization when they die. In this case, paleomagnetic signals recorded by detrital and biogenic magnetite particles will be offset. Such depth offsets will complicate interpretation of paleomagnetic data and need to be better understood. Both scenarios have been documented, although it remains an open question as to how commonly the biogeochemical remanent magnetization mechanism occurs in nature. Now that biogenic magnetite is more widely recognized as an important carrier of sedimentary magnetizations, it is important to test routinely for the possible presence of biogeochemical remanent magnetizations. Regardless, even if there is no depth offset between paleomagnetic signals carried by detrital and biogenic particles, they will have different grain size distributions and will potentially respond differently to a magnetizing field, which will complicate recording of relative paleointensity signals. We illustrate these issues with examples from pelagic marine carbonates from the Southern Ocean and Pleistocene clays from the South China Sea. Our results underline the importance of improving our understanding of magnetization acquisition when using sediments to obtain detailed records of geomagnetic field behavior.

Roberts, A. P.; Heslop, D.; Ouyang, T.; Chang, L.

2013-12-01

299

Laschamp and Mono Lake Geomagnetic Excursions Recorded in New Zealand  

NASA Astrophysics Data System (ADS)

Eight basaltic lavas from the Auckland Volcanic Field, New Zealand, record three distinct sets of excursional geomagnetic field directions with low paleointensities, however the timing and therefore paleomagnetic significance of these records have been poorly understood. Radiocarbon, K-Ar, and thermoluminescence dating constrain these lavas to have erupted during the last 75 ka, a period during which at least three excursions are recorded in the northern hemisphere. Thirty-four 40Ar/39Ar incremental heating experiments conducted on groundmass from seven of these excursional lavas indicate that they erupted during at least two periods, at 39.1 ± 4.1 and 30.1 ± 4.4 ka, coincident with 40Ar/39Ar and astrochronologic ages determined for the Laschamp and Mono Lake excursions, respectively*. Experiments on lavas associated with a third cluster of virtual geomagnetic poles (VGPs) are complicated by a low concentration of radiogenic argon in the presence of excess argon, yielding discordant age spectra and an imprecise age of 27.7 ± 7.9 ka. VGP clusters from the lavas that we correlate with the Laschamp and Mono Lake excursions fall close to the broad looping VGP pathways obtained from high resolution sediment records of these two excursions. Our findings imply that these excursions, previously identified unequivocally only in the northern hemisphere, were globally synchronized. This supports the hypothesis that during short-lived excursions the geomagnetic field, although weakened, remains largely dipolar. *ages relative to 1.194 Ma ACs and 28.34 Ma TCs standards, reported with 2 ? analytical uncertainties.

Cassata, W.; Singer, B. S.; Cassidy, J.

2007-12-01

300

Geomagnetic Cutoff Rigidity Computer Program: Theory, Software Description and Example  

NASA Technical Reports Server (NTRS)

The access of charged particles to the earth from space through the geomagnetic field has been of interest since the discovery of the cosmic radiation. The early cosmic ray measurements found that cosmic ray intensity was ordered by the magnetic latitude and the concept of cutoff rigidity was developed. The pioneering work of Stoermer resulted in the theory of particle motion in the geomagnetic field, but the fundamental mathematical equations developed have 'no solution in closed form'. This difficulty has forced researchers to use the 'brute force' technique of numerical integration of individual trajectories to ascertain the behavior of trajectory families or groups. This requires that many of the trajectories must be traced in order to determine what energy (or rigidity) a charged particle must have to penetrate the magnetic field and arrive at a specified position. It turned out the cutoff rigidity was not a simple quantity but had many unanticipated complexities that required many hundreds if not thousands of individual trajectory calculations to solve. The accurate calculation of particle trajectories in the earth's magnetic field is a fundamental problem that limited the efficient utilization of cosmic ray measurements during the early years of cosmic ray research. As the power of computers has improved over the decades, the numerical integration procedure has grown more tractable, and magnetic field models of increasing accuracy and complexity have been utilized. This report is documentation of a general FORTRAN computer program to trace the trajectory of a charged particle of a specified rigidity from a specified position and direction through a model of the geomagnetic field.

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

2001-01-01

301

Reconstructing Holocene geomagnetic field variation: new methods, models and implications  

NASA Astrophysics Data System (ADS)

Reconstructions of the Holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long-term solar-terrestrial relationships and as relative dating tools for geological and archaeological archives. Here, we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts, igneous rocks and sediment records. A new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data. To reduce the influence of a few individual records all sedimentary data are resampled in 50-yr bins, which also means that more weight is given to archaeomagnetic data during the inversion. The sedimentary declination data are treated as relative values and adjusted iteratively based on prior information. Finally, an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties, often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model. As a result of the data adjustments, power has been shifted from quadrupole and octupole to higher degrees compared with previous Holocene geomagnetic field models. We find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr. The new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder, possibly originating from the equator.

Nilsson, Andreas; Holme, Richard; Korte, Monika; Suttie, Neil; Hill, Mimi

2014-07-01

302

Study of Intense Geomagnetic Storms and Their Possible Effects on Society  

Microsoft Academic Search

Intense geomagnetic storms form an important component of Space Weather, We have analyzed some intense geomagnetic storms with Dst < -100 nT that occurred during 1998 -2001. We made use of the ground magnetic data from the Alibag (Geog. 1 8 ° 37' N, 72° 52' E, Geomag. 10° N, 145° 9) and high latitude station, Maitri, Antarctica (Geog. 70°

G. S. LAKHINA; G. JADHAV; S. ALEX; AJAY DHAR; Navi Mumbai

303

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

Microsoft Academic Search

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

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

2008-01-01

304

Hurricane intensity changes associated with geomagnetic variation James B. Elsner1  

E-print Network

geomagnetic data for ten days prior to all hurricanes over the last 50 years (1950± 1999). A signi) it is suggested that such a relationship will exist only for a speci®c type of North Atlantic hurricane that formsHurricane intensity changes associated with geomagnetic variation James B. Elsner1 * and S. P

Elsner, James B.

305

Measurements of geomagnetically induced current in a power grid in Hokkaido, Japan  

Microsoft Academic Search

There have been numerous reports showing that space weather affects power grids through a geomagnetically induced current (GIC). Generally, power grids consist of power lines connected to transformers, of which neutral points are directly grounded. The GIC flows into those transformers through the neutral points if geomagnetic variations cause a ground level potential. These currents can damage power grids, especially

S. Watari; M. Kunitake; K. Kitamura; T. Hori; T. Kikuchi; K. Shiokawa; N. Nishitani; R. Kataoka; Y. Kamide; T. Aso; Y. Watanabe; Y. Tsuneta

2009-01-01

306

Geomagnetically induced currents in the Finnish 400 kV power transmission system  

Microsoft Academic Search

Faraday's law of induction implies that an electric field is connected with a time variation of the geomagnetic field. The electric field drives electric currents in conductors according to Ohm's law. The induced currents and voltages are usually sources of inconvenience to technical systems such as power transmission grids and pipelines. In an a.c. power system, a geomagnetically induced current

Risto Pirjola

1989-01-01

307

The Role of Geomagnetic Cues in Green Turtle Open Sea Navigation  

Microsoft Academic Search

BackgroundLaboratory and field experiments have provided evidence that sea turtles use geomagnetic cues to navigate in the open sea. For instance, green turtles (Chelonia mydas) displaced 100 km away from their nesting site were impaired in returning home when carrying a strong magnet glued on the head. However, the actual role of geomagnetic cues remains unclear, since magnetically treated green

Simon Benhamou; Joël Sudre; Jérome Bourjea; Stéphane Ciccione; Angelo De Santis; Paolo Luschi

2011-01-01

308

Effect of Local and Global Geomagnetic Activity on Human Cardiovascular Homeostasis  

Microsoft Academic Search

The authors investigated the effects of local and planetary geomagnetic activity on human physiology. They collected data in Sofia, Bulgaria, from a group of 86 volunteers during the periods of the autumnal and vernal equinoxes. They used the factors local\\/planetary geomagnetic activity, day of measurement, gender, and medication use to apply a four-factor multiple analysis of variance. They also used

Svetla Dimitrova; Irina Stoilova; Toni Yanev; Ilia Cholakov

2004-01-01

309

Seasonal Birth Rate Variations in the Gauquelin Professions provide further evidence of Geomagnetic Influences  

Microsoft Academic Search

Evidence of a Semiannual variation in birth frequencies was briefly reported in an earlier publication. Such variations are well-established features of the occurrence of geomagnetic storms and have been explained in terms of the geometry of the earth's magnetic field in relation to that of the Interplanetary Magnetic Field (IMF) emanating from the sun. A subtle detail of the geomagnetic

GRAHAM DOUGLAS

310

Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic  

Microsoft Academic Search

Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous\\/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and

S. C. Cande; D. V. Kent

1995-01-01

311

Rib index.  

PubMed

This article analyzes the double rib contour sign (DRCS) and the rib index (RI). The analyzed topics are 1. the history of presentations - publication of DRCS-RI, 2. the study source origin: school screening for idiopathic scoliosis (IS), 3. what the DRCS and the RI are- Description, 4. the quantification of the DRCS - RI, 5. a reliability study for RI 6. how much the rib index is affected by the distance between the radiation source and the irradiated individual, 7. the implications on IS aetiology, 8. the applications of Rib index for a. documentation of the deformity, b. assessment of physiotherapy, c. assessment of brace treatment and d. pre- and post-operative assessment; assessment of the rib-cage deformity correction on the transverse plane, 9. the use of RI and implications for screening policies 10. the reference of the RI method in spinal textbooks and finally 11. the citations in Google Scholar. PMID:25635184

Grivas, Theodoros B

2014-01-01

312

Quiet geomagnetic field representation for all days and latitudes  

USGS Publications Warehouse

Describes a technique for obtaining the quiet-time geomagnetic field variation expected for all days of the year and distribution of latitudes from a limited set of selected quiet days within a year at a discrete set of locations. A data set of observatories near 75??E longitude was used as illustration. The method relies upon spatial smoothing of the decomposed spectral components. An evaluation of the fidelity of the resulting model shows correlation coefficients usually above 0.9 at the lower latitudes and near 0.7 at the higher latitudes with variations identified as dependent upon season and field element. -from Authors

Campbell, W.H.; Schiffmacher, E.R.; Arora, B.R.

1992-01-01

313

Geomagnetic polarity epochs: new data from Olduvai Gorge, Tanganyika  

USGS Publications Warehouse

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

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

1967-01-01

314

The clustering of polarity reversals of the geomagnetic field  

E-print Network

Often in nature the temporal distribution of inhomogeneous stochastic point processes can be modeled as a realization of renewal Poisson processes with a variable rate. Here we investigate one of the classical examples, namely the temporal distribution of polarity reversals of the geomagnetic field. In spite of the commonly used underlying hypothesis, we show that this process strongly departs from a Poisson statistics, the origin of this failure stemming from the presence of temporal clustering. We find that a Levy statistics is able to reproduce paleomagnetic data, thus suggesting the presence of long-range correlations in the underlying dynamo process.

V. Carbone; L. Sorriso-Valvo; A. Vecchio; F. Lepreti; P. Veltri; P. Harabaglia; I. Guerra

2006-03-10

315

Animal behaviour: geomagnetic map used in sea-turtle navigation.  

PubMed

Migratory animals capable of navigating to a specific destination, and of compensating for an artificial displacement into unfamiliar territory, are thought to have a compass for maintaining their direction of travel and a map sense that enables them to know their location relative to their destination. Compasses are based on environmental cues such as the stars, the Sun, skylight polarization and magnetism, but little is known about the sensory mechanism responsible for the map sense. Here we show that the green sea-turtle (Chelonia mydas) has a map that is at least partly based on geomagnetic cues. PMID:15118716

Lohmann, Kenneth J; Lohmann, Catherine M F; Ehrhart, Llewellyn M; Bagley, Dean A; Swing, Timothy

2004-04-29

316

Electro Acceleration in a Geomagnetic Field Line Resonance  

SciTech Connect

A hybrid MHD kinetic electron model in dipolar coordinates is used to sim- ulate the upward current region of a geomagnetic Field Line Resonance (FLR) system for a realistic ambient electron temperatures of a keV. It is found that mirror force e ects result in potential drops su#14;cient to accelerate electrons to energies in excess of a keV in support of eld aligned currents on the or- der of 0.5 #22;µA/m2. The wave energy dissipated in this acceleration would com- pletely damp an undriven FLR with an equatorial width of 0.5 RE within two resonance cycles.

Peter Damiano and J.R. Johnson

2012-08-17

317

IAGA Geomagnetic Data Analysis format - Analysis_IAGA  

NASA Astrophysics Data System (ADS)

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

-Emilian Toader, Victorin; Marmureanu, Alexandru

2013-04-01

318

Nighttime ionosphere thermosphere coupling observed during an intense geomagnetic storm  

NASA Astrophysics Data System (ADS)

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

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

319

Analysis of the 3-7 October 2000 and 15-24 April 2002 geomagnetic storms with an optimized nonlinear dynamical model  

NASA Astrophysics Data System (ADS)

A computationally optimized low-dimensional nonlinear dynamical model of the magnetosphere-ionosphere system called WINDMI is used to analyze two large geomagnetic storm events, 3-7 October 2000 and 15-24 April 2002. These two important storms share common features such as the passage of magnetic clouds, shock events from coronal mass ejections, triggered substorms, and intervals of sawtooth oscillations. The sawtooth oscillations resemble periodic substorms but occur in association with strong or building ring current populations and have injection regions that are unusually close to the Earth and unusually wide in magnetic local times (Henderson et al., 2006; Borovsky et al., 2007). The April 2002 event includes one of the best examples of sawtooth events ever observed. On 18 April 2002, sawtooth oscillations were clearly visible when solar wind conditions (IMF Bz, density, pressure) were relatively steady with a slowly varying Dst. In this study, WINDMI is used to model the 3-7 October 2000 and 15-24 April 2002 geomagnetic activity. WINDMI results are evaluated focusing on the sawtooth intervals and the overall prediction of the westward auroral electrojet (AL) index and Dst index. The input to the model is the dynamo driving voltage derived from the fluctuating solar wind plasma and the interplanetary magnetic field measured by the ACE satellite. The output of the model is a field-aligned current proportional to the AL index and the energy stored in the ring current which is proportional to the Dst index. The model parameters are optimized using a genetic algorithm (GA) to obtain solutions that simultaneously have least mean square fit to the AL and Dst indices and also exhibit substorms of period 2-4 hours. The GA optimization results show that the model is able to predict the Dst index reliably and captures the timing and periodicity of the sawtooth signatures in the AL index reasonably well for both storm events.

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

2007-04-01

320

Seasonal dependence of magnetic field variations from subauroral latitude to the magnetic equator during geomagnetic sudden commencements  

Microsoft Academic Search

Seasonal dependence of diurnal variation of the main impulse (MI) of geomagnetic sudden commencements (SCs) has been investigated using the long-tern geomagnetic field data with high time resolution of 1 sec within a period from 1996 to 2008 provided from the NSWM [Kikuchi et al., 2008] and CPMN [Yumoto and the CPMN group, 2001] chains and the WDC for Geomagnetism,

A. Shinbori; Y. Tsuji; T. Kikuchi; T. Araki; A. Ikeda; T. Uozumi; S. I. Solovyev; B. Shevtsov; R. S. Otadoy; H. Utada; T. Nagatsuma; H. Hayashi; T. Tsuda; K. Yumoto

2010-01-01

321

Low frequency geomagnetic field fluctuations at different high latitude stations during october 29-31, 2003  

NASA Astrophysics Data System (ADS)

We study the low frequency geomagnetic field fluctuations detected at high latitude in the period October 29-31, 2003, which is characterized by the Earth arrival of solar wind CMEs which produced major geomagnetic storms; these solar wind structures are characterized by high plasma speed and long-duration intervals with northward interplanetary magnetic field. We analyze geomagnetic field data recorded at the three antarctic stations Terra Nova Bay, Scott Base and Dumont DUrville, located at the same corrected geomagnetic latitude (about 80S) but at different magnetic local time (MLT=UT-8, MLT=UT-7 and MLT=UT-13, respectively). The analysis is extended also to the canadian station Cambridge Bay, which has the same magnetic local time and almost opposite corrected geomagnetic latitude as Terra Nova Bay.

Lepidi, S.; Cafarella, L.; Palangio, P.; Santarelli, L.

322

Low Frequency Geomagnetic Field Fluctuations at Different High Latitude Stations During October 29-31, 2003  

NASA Astrophysics Data System (ADS)

In this work we present a study of the low frequency geomagnetic field fluctuations detected at high latitude in the period October 29-31, 2003; this period is characterized by the Earth's arrival of solar wind CMEs, which on one hand produced major geomagnetic storms, on the other hand were characterized by long-duration intervals with northward interplanetary magnetic field and high solar wind speed. We analyze geomagnetic field data recorded at the three antarctic stations Terra Nova Bay, Scott Base and Dumont D'Urville, located at the same geomagnetic latitude (about 80S) but at different magnetic local time (about MLT=UT-8, MLT=UT-7 and MLT=UT-13, respectively). The analysis is extended also to the canadian station Cambridge Bay, which has the same magnetic local time and almost opposite corrected geomagnetic latitude as Terra Nova Bay.

Lepidi, S.; Cafarella, L.; Palangio, P.; Santarelli, L.

2004-05-01

323

Magnetic polarity fractions in magnetotactic bacterial populations near the geomagnetic equator  

PubMed Central

The relative numbers of North-seeking and South-seeking polarity types in natural populations of magnetotactic bacteria were determined at sites on the coast of Brazil. These sites were South of the geomagnetic equator and had upward geomagnetic inclinations of 1-12°. For upward inclinations >6°, South-seeking cells predominated over North-seeking cells by more than a factor of 10. For upward inclinations <6°, the fraction of North-seeking cells in the population increased with decreasing geomagnetic inclination, approaching 0.5 at the geomagnetic equator. We present a simple statistical model of a stochastic process that qualitatively accounts for the dynamics of the two polarity types in a magnetotactic bacterial population as a function of the geomagnetic field inclination. PMID:19431763

de Araujo, F. F. Torres; Germano, F. A.; Gonçalves, L. L.; Pires, M. A.; Frankel, R. B.

1990-01-01

324

Quantitative maps of geomagnetic perturbation vectors during substorm onset and recovery  

NASA Astrophysics Data System (ADS)

We have produced the first series of spherical harmonic, numerical maps of the time-dependent surface perturbations in the Earth's magnetic field following the onset of substorms. Data from 124 ground magnetometer stations in the Northern Hemisphere at geomagnetic latitudes above 33° were used. Ground station data averaged over 5 min intervals covering 8 years (1998-2005) were used to construct pseudo auroral upper, auroral lower, and auroral electrojet (AU*, AL*, and AE*) indices. These indices were used to generate a list of substorms that extended from 1998 to 2005, through a combination of automated processing and visual checks. Events were sorted by interplanetary magnetic field (IMF) orientation (at the Advanced Composition Explorer (ACE) satellite), dipole tilt angle, and substorm magnitude. Within each category, the events were aligned on substorm onset. A spherical cap harmonic analysis was used to obtain a least error fit of the substorm disturbance patterns at 5 min intervals up to 90 min after onset. The fits obtained at onset time were subtracted from all subsequent fits, for each group of substorm events. Maps of the three vector components of the averaged magnetic perturbations were constructed to show the effects of substorm currents. These maps are produced for several specific ranges of values for the peak |AL*| index, IMF orientation, and dipole tilt angle. We demonstrate an influence of the dipole tilt angle on the response to substorms. Our results indicate that there are downward currents poleward and upward currents just equatorward of the peak in the substorms' westward electrojet.

Pothier, N. M.; Weimer, D. R.; Moore, W. B.

2015-02-01

325

A correlative comparison of the ring current and auroral electrojects usig geomagnetic indices  

NASA Technical Reports Server (NTRS)

From a study of the 21 largest geomagnetic storms during solar cycle 21, a strong correlation is established between the ring current index Dst and the time-weighted accumulation of the 1-hour auroral electrojets indices, AE and AL. The time-weighted accumulation corresponds to convolution of the auroral electrojet indices with an exponential weighting function with an e-folding time of 9.4 hours. The weighted indices AE(sub w) and AL(sub w) have correltation coefficients against Dst ranging between 0.8 and 0.95 for 20 of the 21 storms. Correlation over the entire solar cycle 21 database is also strong but not as strong as for an individual storm. A set of simple Dst prediction functions provide a first approximation of the inferred dependence, but the specific functional relationship of Dst (AL(sub w)) or Dst (AL(sub w)) varies from one storm to the next in a systematic way. This variation reveals a missing parametric dependence in the transfer function. However, our results indicate that auroral electroject indices are potentially useful for predicting storm time enhancements of ring current intensity with a few hours lead time.

Cade, W. B., III; Sojka, J. J.; Zhu, L.

1995-01-01

326

International comparisons to establish the traceability in the global network of geomagnetic observatories to SI units  

NASA Astrophysics Data System (ADS)

The international comparisons in the field of earth-level dc magnetic flux density measurements with the participation of six National Metrology Institutes (NMIs) and four geomagnetic observatories (GMOs) have been carried out in 2013 and 2014 under the auspices of the Regional Metrology Organization Asia Pacific Metrology Programme (APMP). The obtained expanded uncertainty (k = 2) of the weighted mean value of correction values does not exceed 0.1 nT in the range of 20 ?T to 100 ?T, which was one of the main aims of this comparison. VNIIM (D I Mendeleyev Institute for Metrology) was the pilot laboratory for this comparison registered in the Key Comparison Data Base (KCDB) under index APMP.EM-S14. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Shifrin, V. Ya; Khorev, V. N.; Rasson, J.; Park, Po Gyu

2014-01-01

327

High-resolution empirical geomagnetic field model TS07D: Investigating run-on-request and forecasting modes of operation  

NASA Astrophysics Data System (ADS)

The dramatic increase of the geomagnetic field data volume available due to many recent missions, including GOES, Polar, Geotail, Cluster, and THEMIS, required at some point the appropriate qualitative transition in the empirical modeling tools. Classical empirical models, such as T96 and T02, used few custom-tailored modules to represent major magnetospheric current systems and simple data binning or loading-unloading inputs for their fitting with data and the subsequent applications. They have been replaced by more systematic expansions of the equatorial and field-aligned current contributions as well as by the advanced data-mining algorithms searching for events with the global activity parameters, such as the Sym-H index, similar to those at the time of interest, as is done in the model TS07D (Tsyganenko and Sitnov, 2007; Sitnov et al., 2008). The necessity to mine and fit data dynamically, with the individual subset of the database being used to reproduce the geomagnetic field pattern at every new moment in time, requires the corresponding transition in the use of the new empirical geomagnetic field models. It becomes more similar to runs-on-request offered by the Community Coordinated Modeling Center for many first principles MHD and kinetic codes. To provide this mode of operation for the TS07D model a new web-based modeling tool has been created and tested at the JHU/APL (http://geomag_field.jhuapl.edu/model/), and we discuss the first results of its performance testing and validation, including in-sample and out-of-sample modeling of a number of CME- and CIR-driven magnetic storms. We also report on the first tests of the forecasting version of the TS07D model, where the magnetospheric part of the macro-parameters involved in the data-binning process (Sym-H index and its trend parameter) are replaced by their solar wind-based analogs obtained using the Burton-McPherron-Russell approach.

Stephens, G. K.; Sitnov, M. I.; Ukhorskiy, A. Y.; Vandegriff, J. D.; Tsyganenko, N. A.

2010-12-01

328

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/

329

Experimental determination of geomagnetically trapped energetic heavy ion fluxes  

NASA Technical Reports Server (NTRS)

The observed spatial, directional and spectral characteristics of geomagnetically trapped heavy ions are reviewed. It is found that ions heavier than protons are significantly abundant in the earth's radiation belts, not only at low (ring-current) energies, but also at multi-MeV energies. Observations both at the geomagnetic equator and at low altitudes on the corresponding L-shell show the important roles played by the heavy ions. The heavy ion-to-proton flux ratio can exceed unity when compared at equal total ion energy. This is particularly the case at several MeV energies and in the outer radiation zone. In contrast, comparisons at equal energy per nucleon generally favor protons. The trapped fluxes of helium ions, of carbon, nitrogen and oxygen (CNO) ions, and of ions heavier than fluorine all exhibit high degrees of pitch angle anisotropy. Many of the observed radiation belt particle distribution characteristics are in agreement with first-order (quiet time) theoretical predictions, although some of the finer details await further research.

Spjeldvik, W. N.; Fritz, T. A.

1983-01-01

330

K-Ar ages of the Auckland geomagnetic excursions  

NASA Astrophysics Data System (ADS)

K-Ar age determinations were made on two monogenetic volcanoes in the Auckland volcanic field, New Zealand, which have recorded the Auckland geomagnetic excursions. For the Wiri volcano with the north-down intermediate paleomagnetic direction, five samples gave a weighted mean age of 27 ± 5 (1?) ka. For the Hampton Park volcano with the west-up intermediate direction, three samples gave a weighted mean of 55 ± 5 (1?) ka. Since these two K-Ar ages are distinguished at 2? level, it is inferred that at least two geomagnetic excursions can be recognized in Auckland. The age of the Hampton Park is barely distinguished from the established age range of the Laschamp excursion (39-45 ka) at 2? level. The age of the Wiri coincides with the age of c. 30 ka in which excursions have been found from sedimentary and volcanic records. The reported excursions from volcanic rocks show a VGP cluster in the central to northern Pacific region which is distinct from the VGP paths or clusters during polarity reversals.

Mochizuki, Nobutatsu; Tsunakawa, Hideo; Shibuya, Hidetoshi; Tagami, Takahiro; Ozawa, Ayako; Cassidy, John; Smith, Ian E. M.

2004-02-01

331

Global ionospheric dynamics and electrodynamics during geomagnetic storms (Invited)  

NASA Astrophysics Data System (ADS)

Globally distributed total electron content (TEC) data has become an important tool for exploring the consequences of storm-time electrodynamics. Magnetosphere-ionosphere coupling during the main phase is responsible for the largest ionospheric effects observed during geomagnetic storms, mediated by global scale electrodynamics. Recent research using case studies reveals a complex picture of M-I coupling and its relationship to interplanetary drivers such as the solar wind electric field. Periods of direct coupling exist where the solar wind electric field is strongly correlated with prompt penetration electric fields, observed as enhanced vertical plasma drifts or an enhanced electrojet in the daytime equatorial ionosphere. Periods of decoupling between low latitude electric fields and the solar wind electric field are also observed, but the factors distinguishing these two types of response have not been clearly identified. Recent studies during superstorms suggest a role for the transverse (y-component) of the interplanetary magnetic field, which affects magnetospheric current systems and therefore may affect M-I coupling, with significant ionospheric consequences. Observations of the global ionospheric response to a range of geomagnetic storm intensities are presented. Scientific understanding of the different factors that affect electrodynamic aspects of M-I coupling are discussed.

Mannucci, A. J.; Tsurutani, B.; Verkhoglyadova, O. P.; Komjathy, A.; Butala, M. D.

2013-12-01

332

Comparison of Dst Forecast Models for Intense Geomagnetic Storms  

NASA Technical Reports Server (NTRS)

We have compared six disturbance storm time (Dst) forecast models using 63 intense geomagnetic storms (Dst <=100 nT) that occurred from 1998 to 2006. For comparison, we estimated linear correlation coefficients and RMS errors between the observed Dst data and the predicted Dst during the geomagnetic storm period as well as the difference of the value of minimum Dst (Delta Dst(sub min)) and the difference in the absolute value of Dst minimum time (Delta t(sub Dst)) between the observed and the predicted. As a result, we found that the model by Temerin and Li gives the best prediction for all parameters when all 63 events are considered. The model gives the average values: the linear correlation coefficient of 0.94, the RMS error of 14.8 nT, the Delta Dst(sub min) of 7.7 nT, and the absolute value of Delta t(sub Dst) of 1.5 hour. For further comparison, we classified the storm events into two groups according to the magnitude of Dst. We found that the model of Temerin and Lee is better than the other models for the events having 100 <= Dst < 200 nT, and three recent models (the model of Wang et al., the model of Temerin and Li, and the model of Boynton et al.) are better than the other three models for the events having Dst <= 200 nT.

Ji, Eun-Young; Moon, Y.-J.; Gopalswamy, N.; Lee, D.-H.

2012-01-01

333

Ionospheric Effects Observed by Radio Tomography during Severe Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

334

The Equatorial Scintillations and Space Weather Effects on its Generation during Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transiono-spheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different mag-netospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintil-lations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of elec-tron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind -magnetosphere -ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scin-tillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere cur-rents and the solar wind. Taking into account the time delay between the solar wind and the ionosphere phenomena, the relationship between the solar wind and the ionosphere parameters can be used for predicting of scintillations.

Biktash, Lilia

335

Education Index  

NSDL National Science Digital Library

The Education Index Web site provides a guide to "the most useful education-related sites on the Web." The links can be browsed by subject such as astronomy, chemistry, geology, and physics (among many others), or by lifestage, from prenatal and infant all the way to college and continuing education. Although the sites described do not have a date of review or rating system, users should still find the resource worthwhile.

336

Scintillation Monitoring Using Asymmetry Index  

NASA Astrophysics Data System (ADS)

Variation in electron density can have significant effect on GNSS signals in terms of propagation delay. Ionospheric scintillation can be caused by rapid change of such delay, specifically, when they last for a longer period of time. Ionospheric irregularities that account for scintillation may vary significantly in spatial range and drift with the background plasma at speeds of 45 to 130 m/sec. These patchy irregularities may occur several times during night, e.g. in equatorial region, with the patches move through the ray paths of the GNSS satellite signals. These irregularities are often characterized as either ‘large scale’ (which can be as large as several hundred km in East-West direction and many times that in the North-South direction) or ‘small scale’ (which can be as small as 1m). These small scale irregularities are regarded as the main cause of scintillation [1,2]. In normal solar activity conditions, the mid-latitude ionosphere is not much disturbed. However, during severe magnetic storms, the aurora oval extends towards the equator and the equator anomaly region may stretched towards poles extending the scintillation phenomena more typically associated with those regions into mid-latitudes. In such stormy conditions, the predicted TEC may deviate largely from the true value of the TEC both at low and mid-latitudes due to which GNSS applications may be strongly degraded. This work is an attempt to analyze ionospheric scintillation (S4 index) using ionospheric asymmetry index [3]. The asymmetry index is based on trans-ionospheric propagation between GPS and LEO satellites in a radio occultation (RO) scenario, using background ionospheric data provided by MIDAS [4]. We attempted to simulate one of the recent geomagnetic storms (NOAA scale G4) occurred over low/mid-latitudes. The storm started on 26 September 2011 at UT 18:00 and lasted until early hours of 27 September 2011. The scintillation data for the storm was taken from an ionospheric station in Cairo, Egypt (lat= 29.8641 °, long= 31.3172 °). It was observed that the level of asymmetry was significantly increased during the main phase of the geomagnetic storm. This was due to the changes in ionization, which in turn produced large gradients along occulted ray path in the ionosphere. A very good correlation was found between the evaluated ionospheric asymmetry index and the S4 scintillation index. Additionally, the correlation between evaluated ionospheric asymmetry and errors related to the RO inversion products such as peak electron density (delta NmF2) and Vertical TEC (delta VTEC) estimates also showed promising results. This work is carried out under the framework of the TRANSMIT project (Training Research and Applications Network to Support the Mitigation of Ionospheric Threats - www.transmit-ionosphere.net). [1]Basu Sa. and Basu Su., (1981), ‘Equatorial Scintillation - A Review’, Journal of Atmospheric and Solar-Terrestrial Physics, 43, p. 473. [2]Davies K., (1990), ‘Ionospheric Radio’, IEEE Electromagnetic Waves Series 31, Peter Peregrinus Ltd. [3]Spencer, P., Mitchell, C.N., (2007) ‘Imaging of fast moving electron-density structures in the polar cap’, Annals of Geophysics, vol. 50, no. 3, pp. 427-434. [4]Shaikh, M.M., Notarpietro, R., Nava, B., (2013) ‘The Impact of Spherical Symmetry Assumption on Radio Occultation Data Inversion in the Ionosphere: An Assessment Study’, Advances in Space Research, doi: http://dx.doi.org/10.1016/j.asr.2013.10.025.

Shaikh, Muhammad Mubasshir; Mahrous, Ayman; Abdallah, Amr; Notarpietro, Riccardo

337

Online calculators for geomagnetic models at the National Geophysical Data Center  

NASA Astrophysics Data System (ADS)

NOAA’s National Geophysical Data Center at Boulder provides online calculators for geomagnetic field models. These models provide current and past values of the geomagnetic field on regional and global spatial scales. These calculators are popular among scientists, engineers and the general public across the world as a resource to compute geomagnetic field elements. We regularly update both the web interfaces and the underlying geomagnetic models. We have four different calculators to compute geomagnetic fields for different user applications. The declination calculators optionally use our World Magnetic Model (WMM) or the International Geomagnetic Reference Field (IGRF) to provide geomagnetic declination as well as its annual rate of change for the chosen location. All seven magnetic field components for a single day or for a range of years from 1900-present can obtained using our Magnetic Field Calculator IGRFWMM. Users can also compute magnetic field values (current and past) over an area using the IGRFGrid calculator. The USHistoric calculator uses a US declination model to compute the declination for the conterminous US from 1750 - present (data permitting). All calculators allow the user to enter the location either as a Zip Code or by specifying the geographic latitude and longitude.

Ford, J. P.; Nair, M.; Maus, S.; McLean, S. J.

2009-12-01

338

Effect of geomagnetic disturbances on physiological parameters: An investigation on aviators  

NASA Astrophysics Data System (ADS)

Over the last years the potential effect that the geomagnetic activity may have on human physiological parameters (such as heart rate, arterial diastolic and systolic pressure) is being widely investigated with irrefutable results. As it is suggested, human health can be affected by solar activity and related geophysical changes. In this study a group of 4018 Slovak aviators was examined from January 1, 1994 to December 31, 2002, covering periods with high solar and geomagnetic activity. Specifically, medical data of mean values of arterial diastolic and systolic blood pressure, which were registered during the medical examinations of the Slovak aviators, were related to daily variations of Dst and Ap geomagnetic indices. All subjects were men (from 18 to 60 years old) in good health. Statistical significance levels (p-values) of the effect of geomagnetic activity on the aforementioned parameters up to three days before and three days after the geomagnetic event were established using the statistical method ANalysis Of VAriance (ANOVA). Statistical analysis of the arterial blood pressure variations for different levels of geomagnetic activity revealed that geomagnetic changes are connected to variations of the human physiological parameters.

Papailiou, M.; Mavromichalaki, H.; Kudela, K.; Stetiarova, J.; Dimitrova, S.

2011-11-01

339

Geomagnetic Field Reversals and Life on the Earth in Phanerozoic Time  

NASA Astrophysics Data System (ADS)

Global paleomagnetic and biostratigraphic data are generalized. As a result it is found out that the direct connection between geomagnetic reversals, biozones and maxima of mass extinction of a biota is absent. At the same time it is noted close to a synchronous total picture of consistent changes of biozones and geomagnetic polarity. It is explained by the general source - the Earth's diurnal rotation. The reversal polarity of a geomagnetic field prevailed during the Phanerozoic that is agreed with the Earth's counterclockwise rotation. Change of polarity of a field, most likely, is connected with acceleration or deceleration of rotation speed of the internal core relative to the Earth's mantle. Lack of direct interrelation between changes in the biosphere and geomagnetic field indicate a lack of influence of a field on life evolution on Earth. It follows also from the fact that life on Earth developed from primitive unicellular forms to mammals and the man and diversity of biota was grew against a close condition of a geomagnetic field during ~2,5 billion years and irrespective of numerous geomagnetic reversals. Main conclusion: evolutionary development of life on Earth doesn't depend both on large changes of a geomagnetic field, and on the extreme catastrophic events conducting to mass extinction of a biota.

Pechersky, D. M.

2014-10-01

340

Methods of analysis of geomagnetic field variations and cosmic ray data  

NASA Astrophysics Data System (ADS)

In the present paper, we propose a wavelet-based method of describing variations in the Earth's magnetic field, such as the horizontal component of the geomagnetic field, in addition to methods for evaluating changes in the energy characteristics of the field and for isolating the periods of increased geomagnetic activity. Based on a combination of multiresolution wavelet decompositions with neural networks, we propose a method of approximation of the cosmic ray time course and the allocation of anomalous variations (Forbush effects) that occur during periods of high solar activity. During the realization of the method, an algorithm was created for selecting the level of the wavelet decomposition and adaptive construction of the neural network. By using the proposed methods, we performed a joint analysis of the geomagnetic field and cosmic rays during periods of strong magnetic storms. The strongest geomagnetic field perturbations were observed in periods of abnormal changes in cosmic ray level. Assessment of the intensity of geomagnetic disturbances on the eve of and during magnetic storm development allowed us to highlight local increases in intensity of the geomagnetic field occurring at different frequency ranges prior to the development of the storm's main phase. Implementation of the proposed method with theoretical tools in combination with other methods will improve the estimation accuracy of the geomagnetic field state during space weather forecasting.

Mandrikova, Oksana V.; Solovev, Igor S.; Zalyaev, Timur L.

2014-12-01

341

Comparing the accuracy of BMKG geomagnetic maps with those of IGRF over the Indonesian region  

NASA Astrophysics Data System (ADS)

In compliance with the resolutions of IAGA (International Association of Geomagnetism and Aeronomy), every five years, BMKG or Meteorology, Climatology and Geophysics Agency of Indonesia builds geomagnetic field maps based on actual measurements in about fifty ground stations. Using data collected from satellites and from observatories around the world, IAGA also builds a global model of geomagnetic field termed IGRF (International Geomagnetic Reference Field). In this study, we compare the accuracy of BMKG maps with that of IGRF to evaluate the continuation of BMKG geomagnetic mapping program. The comparison, based on 1985-2010 data, was conducted by spatial analyses using collocated cokriging and kridging with external drift to map the observation data. The results show that BMKG maps differ from IGRF maps. For example, BMKG total intensity maps show changes of anomaly of -300 nT in 1985-1990 to -20 nT in 1995-2000 and to 200 nT in 2005-2010. The inaccuracy of IGRF maps over Indonesia are due to the scarcity of geomagnetic stations used by IGRF in the region and to the complexity of Indonesian geology. In conclusion, the existing BMKG geomagnetic mapping program is satisfactory. However, the quality of declination maps might be improved by adding several new ground stations.

Syirojudin, Muhamad; Bijaksana, Satria

2013-09-01

342

High-resolution geomagnetic field modeling and forecasting  

NASA Astrophysics Data System (ADS)

We use geomagnetic observatory data, survey data and satellite data from the CHAMP, Oersted, MAGSAT, DE-2 and POGO missions to derive two time-dependent spherical harmonic models of Earth's magnetic field at the core-mantle boundary: one for the years 1957-2009 and the other for the years 2001-2009 (in order to investigate the limits of core field resolution with the most recent, highly accurate data). We pay particular attention to observatory and satellite data analysis and to spatial and temporal data distributions in order to separate external and internal fields. Our approach is to produce models with varying spatial roughness and to examine them with respect to correlations with known structures of core and crustal fields. The final models are consistent with other main field models in their general structure, but show differences predominantly in places where main field features are known to be complex (e.g. the South Atlantic Anomaly). Thus, the models reveal a more detailed spatial and temporal structure of the magnetic field at the core-mantle boundary. Such high-resolution models can be used to infer small-scale core surface flows and core dynamics. We use the 1957-2009 geomagnetic field model to derive time-dependent core flow models and produce hindcasts of the Earth's main magnetic field. The goal of this study is to explore whether we can accurately forecast changes in geomagnetic secular variation by advecting core-surface flows forward in time and accounting for torsional oscillations. We compare hindcasts produced over different time intervals and computed from steady and time-varying core flow models, and also consider differently parametrized core flows (such as steady flow, steadily accelerated flow and steadily accelerated flow with torsional oscillations). We find that the steadily accelerated flow plus torsional oscillations is able to accurately reproduce changes in the Earth's magnetic field for short-term (5 years) and medium-term (13 years) hindcasts and over time intervals characterized by both slower and faster secular variation. We also find that hindcasts are strongly dependent on the accuracy of the core flow models, and that hindcasts can be improved by properly accounting for non-steady flow acceleration in addition to torsional oscillations.

Soukhovitskaya, Veronika

2010-12-01

343

A short-term ionospheric forecasting empirical regional model (IFERM) to predict the critical frequency of the F2 layer during moderate, disturbed, and very disturbed geomagnetic conditions over the European area  

NASA Astrophysics Data System (ADS)

A short-term ionospheric forecasting empirical regional model (IFERM) has been developed to predict the state of the critical frequency of the F2 layer (foF2) under different geomagnetic conditions. IFERM is based on 13 short term ionospheric forecasting empirical local models (IFELM) developed to predict foF2 at 13 ionospheric observatories scattered around the European area. The forecasting procedures were developed by taking into account, hourly measurements of foF2, hourly quiet-time reference values of foF2 (foF2QT), and the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap, (ap(?)), for each observatory. Under the assumption that the ionospheric disturbance index ln(foF2/foF2QT) is correlated to the integrated geomagnetic disturbance index ap(?), a set of statistically significant regression coefficients were established for each observatory, over 12 months, over 24 h, and under 3 different ranges of geomagnetic activity. This data was then used as input to compute short-term ionospheric forecasting of foF2 at the 13 local stations under consideration. The empirical storm-time ionospheric correction model (STORM) was used to predict foF2 in two different ways: scaling both the hourly median prediction provided by IRI (STORM_foF2MED,IRI model), and the foF2QT values (STORM_foF2QT model) from each local station. The comparison between the performance of STORM_foF2MED,IRI, STORM_foF2QT, IFELM, and the foF2QT values, was made on the basis of root mean square deviation (r.m.s.) for a large number of periods characterized by moderate, disturbed, and very disturbed geomagnetic activity. The results showed that the 13 IFELM perform much better than STORM_foF2,sub>MED,IRI and STORM_foF2QT especially in the eastern part of the European area during the summer months (May, June, July, and August) and equinoctial months (March, April, September, and October) under disturbed and very disturbed geomagnetic conditions, respectively. The performance of IFELM is also very good in the western and central part of the Europe during the summer months under disturbed geomagnetic conditions. STORM_foF2MED,IRI performs particularly well in central Europe during the equinoctial months under moderate geomagnetic conditions and during the summer months under very disturbed geomagnetic conditions. The forecasting maps generated by IFERM on the basis of the results provided by the 13 IFELM, show very large areas located at middle-high and high latitudes where the foF2 predictions quite faithfully match the foF2 measurements, and consequently IFERM can be used for generating short-term forecasting maps of foF2 (up to 3 h ahead) over the European area.

Pietrella, M.

2012-02-01

344

An experimental evaluation of autonomous underwater vehicle localization on geomagnetic map  

NASA Astrophysics Data System (ADS)

This letter reports an experimental evaluation of a three-axis magnetometer into an inertial navigation system (INS) for underwater localization. The magnetometer measurements of geomagnetic field are compared with map values to provide position updates to the INS. The concept of such navigation system is not new but lacks test verification and actual application. We examine the capabilities of the integrated navigation by using a localization algorithm based on the interval knowledge of geomagnetic field values. The underwater experimental result indicates that the use of geomagnetic values significantly reduces the growth of position errors of an INS.

Wu, Zhitian; Hu, Xiaoping; Wu, Meiping; Mu, Hua; Cao, Juliang; Zhang, Kaidong; Tuo, Zhouhui

2013-09-01

345

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

PubMed

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

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

2014-01-01

346

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

USGS Publications Warehouse

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

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

1986-01-01

347

Some properties of trans-equatorial ion whistlers observed by Isis satellites during geomagnetic storms  

NASA Technical Reports Server (NTRS)

Several ion whistlers were observed by the polar orbiting satellites, Isis, during geomagnetic storms associated with large solar flares in 1982. It seems that the proton density ratio to the total ions deduced from the crossover frequency of the transequatorial ion whistlers observed at geomagnetic low latitudes during the main phase of the geomagnetic storm on July 14, 1982 was lower than the usual density ratio. An anomalous pattern seen on the time-compressed dynamic spectra of the ion whistlers on September 6, 1982 may suggest the existence of effects by the component He(3+) in a quite small amount.

Watanabe, S.; Ondoh, T.

1986-01-01

348

On the shape of the Geomagnetic Tail at Lunar distances: Preliminary Resuts from Artemis Observations  

NASA Astrophysics Data System (ADS)

Geomagnetic tail is one of the least investigated regions of the magnetosphere behind the Earth owing to the limited number of spacecraft and observations. It is the region where the geomagnetic dipole field lines of the Earth are organized by the solar wind stretching. The characteristics of the geomagnetic tail and its response to IMF were studied by the missions, ISEE-3, IMP-8, Wind, Geotail, visited geomagnetic tail at different distances. The structure of the geomagnetic tail is controlled by the IMF orientation and its own internal dynamics. Geomagnetic tail has different regions where the plasma and magnetic field characteristics are largely depend on the IMF orientation. These characteristics show differences at different tail distances. For example it is determined that the tail twists as result of the reconnection with IMF By and this twist is higher as one move away from the Earth toward the distant tail. Like a windsock, it is expected that the IMF control will increase toward the distant tail. Twisting also displaces the north and south lobes on the dawn and dusk sides. Tail length and the shape are also different for different IMF orientations. Flattening of the geomagnetic tail cross-section occurs during the strong IMF Bys. It becomes an ellipse in the yz plane as the IMF By stress causes the tail to be flattened on the top and bottom. Models estimate that the geomagnetic tail length can be 165 Re while Pioneer spacecraft detected geomagnetic tail as long as 100 Re. These findings are based on the very limited data from brief geomagnetic tail encounters of the spacecraft. Since August 2011, with the repositioning of the two of THEMIS spacecraft pair, ARTEMIS is giving a new opportunity to study the geomagnetic tail at the lunar distances, 60 Re. Using these observations, we will investigate the geomagnetic field shape and its IMF dependence at 60 Re. Based on the magnetopause locations at 60 Re, we will study the shape of the tail on the xy-plane. Available analytical models and the numerical model results will be tested and used to find the best model at lunar distances. In this study, we will present our preliminary results and compare our findings with those from the earlier studies in the literature.

Gencturk Akay, Iklim; Kaymaz, Zerefsan; Sibeck, David G.

2013-04-01

349

Geophysical variables and behavior: XXI. Geomagnetic variation as possible enhancement stimuli for UFO reports preceding earthtremors.  

PubMed

The contribution of geomagnetic variation to the occurrence of UFORs (reports of UFOs) within the New Madrid States during the 6-mo. increments before increases in the numbers of IV-V or less intensity earthquakes within the central USA was determined. Although statistically significant zero-order correlations existed between measures of earthquakes, UFORs and geomagnetic variability, the association between the latter two deteriorated markedly when their shared variance with earthquakes was held constant. These outcomes are compatible with the hypothesis that geomagnetic variability (or phenomena associated with it) may enhance UFORs but only if tectonic stress and strain are increasing within the region. PMID:3982943

Persinger, M A

1985-02-01

350

The geomagnetic jerk of 1969 and the DGRFs  

USGS Publications Warehouse

Cubic spline fits to the DGRF/IGRF series indicate agreement with other analyses showing the 1969-1970 magnetic jerk in the h ??12 and g ??02 secular change coefficients, and agreement that the h ??11 term showed no sharp change. The variation of the g ??01 term is out of phase with other analyses indicating a likely error in its representation in the 1965-1975 interval. We recommend that future derivations of the 'definitive' geomagnetic reference models take into consideration the times of impulses or jerks so as to not be bound to a standard 5 year interval, and otherwise to make more considered analyses before adopting sets of coefficients. ?? 1987.

Thompson, D.; Cain, J.C.

1987-01-01

351

Geomagnetically trapped light isotopes observed with the detector NINA  

NASA Astrophysics Data System (ADS)

The detector New Instrument for Nuclear Analysis (NINA) aboard the satellite Resurs-01-N4 detected hydrogen and helium isotopes geomagnetically trapped, while crossing the South Atlantic Anomaly. Deuterium and tritium at L shell < 1.2 were unambiguously recognized. The 3He and 4He power law spectra, reconstructed at L shell = 1.2 and B < 0.22 G, have indices equal to 2.30 +/- 0.08 in the energy range 12-50 MeV nucleon-1 and 3.4 +/- 0.2 in 10-30 MeV nucleon-1, respectively. The measured 3He/4He ratio and the reconstructed deuterium profile as a function of L shell bring one to the conclusion that the main source of radiation belt light isotopes at Resurs altitudes (~800 km) and for energy greater than 10 MeV nucleon-1 is the interaction of trapped protons with residual atmospheric helium.

Bakaldin, A.; Galper, A.; Koldashov, S.; Korotkov, M.; Leonov, A.; Mikhailov, V.; Murashov, A.; Voronov, S.; Bidoli, V.; Casolino, M.; De Pascale, M.; Furano, G.; Iannucci, A.; Morselli, A.; Picozza, P.; Sparvoli, R.; Boezio, M.; Bonvicini, V.; Cirami, R.; Vacchi, A.; Zampa, N.; Ambriola, M.; Bellotti, R.; Cafagna, F.; Ciacio, F.; Circella, M.; De Marzo, C.; Adriani, O.; Papini, P.; Spillantini, P.; Straulino, S.; Vannuccini, E.; Ricci, M.; Castellini, G.

2002-08-01

352

Observations of geomagnetically trapped light isotopes by NINA  

NASA Astrophysics Data System (ADS)

The detector NINA aboard the satellite Resurs-01N4 detected hydrogen and helium isotopes geomagnetically trapped, while crossing the South Atlantic Anomaly. Deuterium and tritium at L-shell<1.2 were unambiguously recognized. The 3 He and 4 He power-law spectra, reconstructed at L-shell=1.2 and B<0.22 G, have indices equal to 2.30±0.08 in the energy range 12-50 MeV/n, and 3.4±0.2 in 10-40 MeV/n respectively. The measured 3 He/4 He ratio bring to the conclusion that the main source of radiation belt light isotopes is the interaction of trapped protons with residual atmospheric helium.

Bakaldin, A.; Galper, A.; Koldashov, S.; Korotkov, M.; Leonov, A.; Mikhailov, V.; Murashov, A.; Voronov, S.; Bidoli, V.; Casolino, M.; De Pascale, M.; Furano, G.; Iannucci, A.; Morselli, A.; Picozza, P.; Sparvoli, R.; Boezio, M.; Bonvicini, V.; Cirami, R.; Vacci, A.; Zampa, N.; Ambriola, M.; Bellotti, R.; sCafagna, F.; Ciacio, F.; Circella, M.; De Marzo, C.; Adriani, O.; Papini, P.; Spillantini, P.; Straulino, S.; Vannuccini, E.; Bartalucci, S.; Ricci, M.; Castellini, G.; Wizard-NINA Collaboration

2001-08-01

353

Geomagnetic excursion captured by multiple volcanoes in a monogenetic field  

NASA Astrophysics Data System (ADS)

Five monogenetic volcanoes within the Quaternary Auckland volcanic field are shown to have recorded a virtually identical but anomalous paleomagnetic direction (mean inclination and declination of 61.7° and 351.0°, respectively), consistent with the capture of a geomagnetic excursion. Based on documented rates of change of paleomagnetic field direction during excursions this implies that the volcanoes may have all formed within a period of only 50-100 years or less. These temporally linked volcanoes are widespread throughout the field and appear not to be structurally related. However, the general paradigm for the reawakening of monogenetic fields is that only a single new volcano or group of closely spaced vents is created, typically at intervals of several hundred years or more. Therefore, the results presented show that for any monogenetic field the impact of renewed eruptive activity may be significantly under-estimated, especially for potentially affected population centres and the siting of sensitive facilities.

Cassidy, John

2006-11-01

354

Ionospheric Features Diagnosed by Radio Tomography during Strong Geomagnetic Disturbances  

NASA Astrophysics Data System (ADS)

During the periods of geomagnetic storms, the ionosphere has a particularly complicated and rapidly changing structure. Each storm is marked by its own set of specific manifestations, which reflect rearrangement of the dynamical pattern of the ionosphere and strong perturbations in its parameters. The complexity and global scale of the ionospheric processes that occur during the storms call for the nonlocal methods for diagnosing the spatiotemporal structure of the ionospheric disturbances. Here, we present the results of studying the ionospheric structure by the methods of low orbital radio tomography (RT). The ionospheric radio tomography is rapidly developing during the last two decades. Due to the sufficiently high satellite velocity (~7.9 km/s) and, correspondingly, quite fast (compared to the characteristic times of the ionospheric processes) passage of the satellite through the ionospheric region under study, the radio tomographic approach is suitable for making nearly instantaneous (covering an interval of 5-10 min) 2D snapshots of the ionosphere in the altitude-latitude plane. The vertical and horizontal resolution of RT is 30-40 km and 20-30 km, respectively. We consider the ionospheric manifestations of strong geomagnetic storms (1991-2012) in different regions worldwide including the European part of Russia and North America. We note that during the geomagnetic disturbances, the ionosondes frequently show unstable operation. In contrast to the ionosondes that use HF radio waves, the RT methods are suitable for imaging the ionosphere even during severe solar and geophysical disturbances. During the periods of strong perturbations, RT detected various wavelike structures, travelling ionospheric disturbances, and different manifestations of acoustic gravity waves in the ionosphere. Using the RT methods, the wave effects of particle precipitation were analyzed, and plasma flows were estimated. Radio tomographic imaging of the ionosphere during severe disturbances reveals multiextremal spotty patterns with steep wall-like gradients in electron density in the north. Thin enhancements of electron concentration that are elongated by hundreds of kilometers along the magnetic field lines and attain dozens of kilometers in the transversal direction are identified. The complexly structured ionospheric trough with a tilted polar wall shifted towards the equator is revealed. Many RT reconstructions show the ionospheric trough to split. For example, the RT imaging of the storm of March 24-28, 1991 indicates that the ionospheric structures that are normally typical of the subauroral and auroral ionosphere (the troughs and anomalous ionization in the F-region) reached middle latitudes at that time. During the strongest geomagnetic storm on October 30-31, 2003, the ionosphere over the European part of Russia was marked by anomalously high electron concentration; the distribution of electron density in the region of increased ionization was extremely complicated in space and highly variable in time. We are grateful to the North-West Research Associates (NWRA) for providing the experimental data on relative TEC measured at the RT system in Alaska. The work was supported by the Russian Foundation for Basic Research (grants 11-05-01157 and 13-05-01122).

Andreeva, Elena S.; Kunitsyn, Vyacheslav E.; Tereshchenko, Evgeniy D.; Kozharin, Maksim A.; Nazarenko, Marina O.

2013-04-01

355

Separation of the geomagnetic variation of cosmic rays  

NASA Astrophysics Data System (ADS)

The contributions of geomagnetic variations and complex variations in cosmic ray intensities to measured variations in the neutron component of cosmic ray flux are separated by a study of normalized neutron intensities recorded at three stations with different cut-off rigidities. The correlation between Dst variations and temporal variations in normalized intensity differences is calculated for stations with rigidities of 0.0, 4.0 and 13 GV during the large magnetic storm (300 nT) of March 5-13, 1970. Results show the increase in cosmic ray intensities observed during the storm to be due to a decrease in cosmic ray cut-off rigidities. The maximum Dst decrease of 280 nT is found to lead to a 3.2 percent variation in the intensity difference between Dallas and Churchill stations, and a 4.2 percent variation in the difference between Chacataya and Churchill, in agreement with theoretical calculations.

Zhumabaev, B. T.; Kozin, I. D.

356

Database of ion temperature maps during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Ion temperatures as a function of the x and y axes in the geocentric solar magnetospheric (GSM) coordinate system and time are available for 76 geomagnetic storms that occurred during the period July 2008 to December 2013 on CDAWeb. The method for mapping energetic neutral atom data from the Two Wide-angle Imaging Spectrometers (TWINS) mission to the GSM equatorial plane and subsequent ion temperature calculation are described here. The ion temperatures are a measure of the average thermal energy of the bulk ion population in the 1-40 keV energy range. These temperatures are useful for studies of ion dynamics, for placing in situ measurements in a global context, and for establishing boundary conditions for models of the inner magnetosphere and the plasma sheet.

Keesee, Amy M.; Scime, Earl E.

2015-02-01

357

Comparison of methods for modelling geomagnetically induced currents  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

358

2013 Geomagnetic Storm Observations in the Arctic and Antarctic  

NASA Astrophysics Data System (ADS)

During recent 2013 geomagnetic storms, several tongue of ionization (TOI) events have been observed with polar maps of total electron content (TEC) derived from the global network of GNSS receivers. The TOI plasma originates from plasma that has been transported from the mid-latitudes by a feature known as storm enhanced density (SED). The SED plasma separates from the base of the enhanced mid-latitude ionosphere in the afternoon-dusk sector, and forms a plume that carries the plasma westward to the noon-time cusp. The TOI, as observed by GNSS, extends through the dayside cusp, across the polar cap to the night side, in both hemispheres. The TOI is a source of ionospheric irregularities and its distribution across the high latitude ionosphere is controlled by plasma convection. Here, TOI observations are shown using GNSS TEC polar plots overlaid onto SuperDARN HF radar observations of the high-latitude convection pattern. The locations where HF scatter is observed in the presence of TOI plumes are examined. In addition, we overlay observations of scintillation collected by specially equipped GNSS receivers. We explore the similarities between TOI events observed simultaneously in the two hemispheres and examine the time history of the gradients and irregularities. Finally, we report on cases where the position of the SED base stays fixed in latitude and longitude as the earth rotates. This observation is shown below in Figure 1 and holds true in both hemispheres. We correlate these observations to changes in the IMF geomagnetic field. Illustration of fixed position of SED base in March 17, 2013 storm in Northern and Southern Hemispheres.

Coster, A. J.; Thomas, E. G.; Baker, J. B.; Ruohoniemi, J.; Erickson, P. J.; Foster, J. C.

2013-12-01

359

Laschamp and Mono Lake geomagnetic excursions recorded in New Zealand  

NASA Astrophysics Data System (ADS)

Eight basaltic lavas from the Auckland volcanic field, New Zealand, record three distinct sets of excursional geomagnetic field directions and low paleointensities, however the timing and therefore paleomagnetic significance of these records have been poorly understood. Radiocarbon, K-Ar, and thermoluminescence dating constrain these lavas to have erupted during the last 75 ka, a period during which as many as three excursions have been recorded differentially at several northern and fewer southern hemisphere sites. Forty 40Ar/ 39Ar incremental heating experiments conducted on groundmass from seven of these excursional lavas indicate that they erupted during at least two periods, at 39.1 ± 4.1 and 31.6 ± 1.8 ka, coincident with 40Ar/ 39Ar, astrochronologic, and 14C ages determined for the Laschamp and Mono Lake excursions, respectively. Samples from a lava flow associated with a third cluster of virtual geomagnetic poles (VGPs) are complicated by low concentrations of radiogenic argon in the presence of excess argon, and thus yield discordant age spectra and an imprecise age of 26.6 ± 8.1 ka. Our findings indicate that the Laschamp and Mono Lake excursions, until recently identified unequivocally and isotopically dated only in the Northern Hemisphere, were globally synchronized at 40 ± 1 and 32 ± 1 ka. However, the VGPs of lavas that record the Laschamp excursion in New Zealand and France are inconsistent with a simple clockwise looping geometry inferred from VGP paths obtained in eight marine sediment cores spanning the Laschamp excursion. We suggest that the differences in VGPs recorded at the various sites are significant and may point to non-axial dipole components and lower mantle control on transitional fields during short-lived excursions.

Cassata, William S.; Singer, Brad S.; Cassidy, John

2008-04-01

360

Relation of reverse geomagnetic polarity to biological evolution  

NASA Astrophysics Data System (ADS)

We have studied the connection between a number of insect and terrestrial tetrapods families and the duration of periods with normal and reverse polarities from Cenozoic period 84 Mya towards the Neogene 23-0 Mya It was found that the duration of periods of normal and reverse polarities decreased from Paleogene to Neogene In concordance with the rate of changes of the magnetic polarity the number of living families are increasing Following each revitalization the dipole field strength is fluctuating This means that the geomagnetic cut-off should be also fluctuating during changes of polarity from a minimum theoretically zero to maximum as for actual dipole field strength in the equatorial regions where vertical cosmic ray cut-off is about 13-17 GeV In the present time the influence of the Earth s dipole magnetic field configuration results in a better protection against high energetic particles near the equator than in the polar areas which leads to lower dose of irradiation in equatorial than in polar regions Hence when the geomagnetic cut-off is low the exposure to cosmic rays of living systems is high The more often the polarity changes the more often living systems should be exposed to high intensity of cosmic rays and consequently the rate of biological evolution should be higher This is that we can see in Neogene Our experiments carried out during a great solar events when the solar particle fluxes increase in 10 5 in near-earth space and when secondary cosmic rays near Earth s surface also increase revealed the

Belisheva, N. K.; Biernat, H. K.; Lammer, H.; Getselev, I. V.

361

Nighttime thermospheric-ionospheric coupling during geomagnetic storms  

NASA Astrophysics Data System (ADS)

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

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

362

Information on the Motions within the Earth's Core and on the Geomagnetic Field prior to Geomagnetic Data Inversion  

NASA Astrophysics Data System (ADS)

The classical procedure to calculate fluid motions at the Earth's core surface, evolving over the last 102 years, does not take adequately into account our uncertainties on the geomagnetic field and its temporal variations. Indeed, these calculations are usually achieved using unjustifiably regularized magnetic field models, which forgo rapid time variations and were the only ones available until recently. The usual hypotheses on the kinetic energy spectrum, that are made prior to core flow inversions, amount to heavily penalizing small-scale core flows. They appear also strikingly unrealistic, in the light of a recent estimation of the Earth's core magnetic energy. We adopt a different approach and base our discussion of the ratio between the kinetic and magnetic energy densities - as a function of the harmonic degree - on physical considerations. For the largest length-scales, this ratio of energy densities probably does not exceed 10-3. We argue that it increases with the wavenumber up to a value of the order of 1 for the length-scale at which inertial and magnetic waves have similar periods. We find this description well supported by the results of some numerical investigations of the geodynamo equations. We thus deduce information on the kinetic energy spectrum that we can use as prior knowledge before calculating core flows. We can then rely on a newly calculated magnetic field model for the epoch 1900-2010 to determine quasi-geostrophic core flows as consistently as presently possible. Applying an ensemble technique, we are able to deal with the uncertainties on the magnetic field. We discuss to what extent the calculated flow models depend on the a priori information on the magnetic field time variability. Our choice of priors takes into account the recent discovery of rapid changes of the largest scales of the magnetic field in models derived from satellite data and the occurrence of geomagnetic jerks. Finally, we consider that such a discussion of the prior information on the magnetic and velocity fields is a prerequisite before renewed geomagnetic data assimilation attempts.

Jault, D.; Gillet, N.; Schaeffer, N.

2011-12-01

363

The Automatic Predictability of Super Geomagnetic Storm from Halo CMEs Associated with Large Solar Flares  

E-print Network

on real-time solar observations. A severe geomagnetic storm may produce many harmful effects on the Earth Wang Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102 U

364

Forecasts of geomagnetic activity by Ottawa Magnetic Observatory: Their reliabilty and application  

NASA Technical Reports Server (NTRS)

A 27 day forecast of geomagnetic activity based on the forecasts from two locations is presented. To evaluate the reliability of the forecasts, the predicted activity was compared with the actual geomagnetic activity at five geomagnetic observatories located in different magnetic zones: Ottawa (57.0N, 351.5E); Meanook (61.8N, 301.0E); Fort Churchill (68.8N, 322.5E); Cambridge Bay (76.7N, 294.0E); and Resolute Bay (83.1N, 287.7E). Results indicate that the percentage of correct predictions varies with the geomagnetic latitude of the observatory used for comparison. The percentage is on the average highest for lower latitude stations and lowest for the northern stations. The number of incorrect predictions ranges from 4.7% for Ottawa to 8.4% for Churchill.

Hruska, J.

1979-01-01

365

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

366

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

NASA Astrophysics Data System (ADS)

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

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

1992-12-01

367

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

USGS Publications Warehouse

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

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

1997-01-01

368

Geomagnetic observatory GAN Jakub Velimsky K. Chandra Shakar Rao Lars W. Pedersen Ahmed Muslim  

E-print Network

Geomagnetic observatory GAN Jakub Vel´imsk´y K. Chandra Shakar Rao Lars W. Pedersen Ahmed Muslim Arora K. Chandra Shakar Rao Gan Meteorological Office, Dept. of Meteorology Muslim Ahmed With support

Cerveny, Vlastislav

369

Computational Investigation of Hardness Evolution During Friction-Stir Welding of AA5083 and AA2139  

E-print Network

and strain-hardened/stabilized Al-Mg-Mn alloy) and AA2139 (a precipitation hardened quaternary Al-Cu-Mg-Ag alloy). Both of these alloys are currently being used in military-vehicle hull structural and armor systems. In the case of non-age-hardenable AA5083, the dominant microstruc- ture-evolution processes

Grujicic, Mica

370

Transform (60833005, 60573091), 863 2007AA01Z1552009AA011904  

E-print Network

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

371

Specification of > 2 MeV electron flux as a function of local time and geomagnetic activity at geosynchronous orbit  

NASA Astrophysics Data System (ADS)

An algorithm has been developed for specifying > 2 MeV electron flux everywhere along geosynchronous orbit for use in operational products. The statistics of integrated electron fluxes from four GOESs for more than a solar cycle clearly indicate that the local time variation can be represented by a Gaussian distribution as a function of geomagnetic Kp index, which empirically determines the center and the half width of the Gaussian distribution. Using the most current estimated 3 h Kp value as an input, the prediction scheme requires the most recent electron flux measurements from available GOES(s) to determine the maximum and minimum for a Gaussian fit and to provide estimated electron fluxes at geosynchronous orbit with the time resolution of the instrument. In balancing between sufficient data for statistics and the change of geomagnetic configuration, the optimal length of data accumulation time for nowcasting is 6 h when one or two satellites are available. The prediction efficiency (PE) is independent of local time and solar cycle. We found that the PE values are greater than 0.5 when Kp < 5 and independent of Kp at low and moderate values; however, PE decreases dramatically with increasing Kp when Kp ? 5. Although the PE varies from year to year and with the choice of the test satellite, our finding resulted in a PE > 0.6 in 67.6% of the cases and PE > 0.8 more than 23.5% of the time based on our analysis from four GOESs between 1998 and 2009. Moreover, skill scores from our newly developed algorithm are ~90% of the time better than those resulting from a simpler algorithm based on a table provided by O'Brien (2009), indicating a dramatic improvement in predictive capability.

Su, Yi-Jiun; Quinn, Jack M.; Johnston, W. Robert; McCollough, James P.; Starks, Michael J.

2014-07-01

372

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

373

DISENTANGLING GEOMAGNETIC AND PRECIPITATION SIGNALS IN AN 80KYR CHINESE LOESS RECORD OF 10Be  

Microsoft Academic Search

The cosmogenic radionuclide 10Be is produced by cosmic-ray spallation in Earth's atmosphere. Its production rate is regulated by the geomagnetic field intensity, so that its accumulation rate in aeolian sediments can, in principle, be used to derive high-resolution records of geomagnetic field changes. However, 10Be atmospheric fallout rate also varies locally depending on rainfall rate. The accumulation rate of 10Be

Weijian Zhou; Alfred Priller; J Warren Beck; Wu Zhengkun; Chen Maobai; An Zhisheng; Walter Kutschera; Xian Feng; Yu Huagui; Liu Lin

374

A negative test of orbital control of geomagnetic reversals and excursions  

Microsoft Academic Search

A ~41 Kyr periodic component has been reported in some sedimentary paleointensity records, allowing speculation that there may be some component of orbital control of geomagnetic field generation such as by obliquity modulation. However, no discernable tendency is found for astronomically-dated geomagnetic reversals in the Plio-Pleistocene (0 to 5.3 Ma) or excursions in the Brunhes (0 to 0.78 Ma) to

Dennis V. Kent; Julie Carlut

2001-01-01

375

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

Microsoft Academic Search

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

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

1976-01-01

376

The changing world of geomagnetism: A brief history relating to magnetic observatories  

NASA Astrophysics Data System (ADS)

The developments that relate to magnetic observatories are reviewed. Use of geomagnetism in navigation and mining is recounted. Separation of internal effects of geomagnetic fields from the external was studied. Automation of the observatories with help of digital computers is outlined. The Hermanus which is one member of a family of about 200 magnetic observatories in the world is discussed. The term and history of the magnetic observatory are outlined.

Svendsen, K. L.

1982-11-01

377

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

378

Moderate Geomagnetic Storms: Interplanetary Origins and Coupling Functions (ISEE3 Data)  

NASA Technical Reports Server (NTRS)

Geomagnetic storms are related to the ring current intensification, which is driven by energy injection primarily during energetic solar wind-magnetosphere coupling due to reconnection at the magnetopause. This work identified the interplanetary origins of moderate geomagnetic storms (-100nT is less or equal to Dst(sub peak) is less than or equal to -50 nT) and analyzed the coupling processes during the storm main phase at solar maximum (1978-1979).

Mendes, Odim, Jr.; Gonzalez, W. D.; Gonzalez, A. L. C.; Pinto, O., Jr.; Tsurutani, B. T.

1996-01-01

379

Plasmaspheric dynamics resulting from the Hallowe'en 2003 geomagnetic storms  

Microsoft Academic Search

Cross-phase-derived plasma mass density trends during the Hallowe'en 2003 geomagnetic storms are presented for 38° $\\\\lesssim$ magnetic latitude $\\\\lesssim$ 63° (1.61 ? L ? 5.10), using data from the SAMNET (Subauroral Magnetometer Network), BGS (British Geological Survey), and SEGMA (South European Geomagnetic Array), ground-based magnetometer arrays in Europe. At all latitudes monitored, a rapid increase of total mass density is

Z. C. Kale; I. R. Mann; C. L. Waters; M. Vellante; T. L. Zhang; F. Honary

2009-01-01

380

ong-term trends of foE and geomagnetic activity variations  

NASA Astrophysics Data System (ADS)

A relationship between foE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the foF2 trends it is possible to speak about the geomagnetic control of the foE long-term trends as well. Periods of increasing geomagnetic activity correspond to negative foE trends, while these trends are positive for the decreasing phase of geomagnetic activity. This natural relationship breaks down around 1970 (on some stations later) when pronounced positive foE trends have appeared on most of the stations considered. The dependence of foE trends on geomagnetic activity can be related with nitric oxide variations at the E-layer heights. The positive foE trends that appeared after the break down effect may also be explained by the [NO] decrease which is not related to geomagnetic activity variations. But negative trends or irregular foE variations on some stations for the same time period require some different mechanism. Chemical pollution of the lower thermosphere due to the anthropogenic activity may be responsible for such abnormal foE behavior after the end of the 1960s.

Mikhailov, A. V.; de La Morena, B. A.

2003-03-01

381

Reduction of the field-aligned potential drop in the polar cap during large geomagnetic storms  

NASA Astrophysics Data System (ADS)

We have studied photoelectron flows and the inferred field-aligned potential drop in the polar cap during 5 large geomagnetic storms that occurred in the periods when the photoelectron observations in the polar cap were available near the apogee of the FAST satellite (~4000 km) at solar maximum, and the footprint of the satellite paths in the polar cap was under sunlit conditions most of the time. In contrast to the ~20 V potential drop during geomagnetically quiet periods at solar maximum identified by Kitamura et al. [JGR, 2012], the field-aligned potential drop frequently became smaller than ~5 V during the main and early recovery phases of the large geomagnetic storms. Because the potential acts to inhibit photoelectron escape, this result indicates that the corresponding acceleration of ions by the field-aligned potential drop in the polar cap and the lobe region is smaller during the main and early recovery phases of large geomagnetic storms compared to during geomagnetically quiet periods. Under small field-aligned current conditions, the number flux of outflowing ions should be nearly equal to the net escaping electron number flux. Since ions with large flux originating from the cusp/cleft ionosphere convect into the polar cap during geomagnetic storms [e.g., Kitamura et al., JGR, 2010], the net escaping electron number flux should increase to balance the enhanced ion outflows. The magnitude of the field-aligned potential drop would be reduced to let a larger fraction of photoelectrons escape.

Kitamura, N.; Seki, K.; Nishimura, Y.; Hori, T.; Terada, N.; Ono, T.; Strangeway, R. J.

2013-12-01

382

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

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, K.; Fuller, M.; Alerstam, T.; Hake, M.; Kjellen, N.; Strandberg, R.

2006-01-01

383

Geomagnetic control of the spectrum of traveling ionospheric disturbances based on data from a global GPS network  

E-print Network

In this paper an attempt is made to verify the hypothesis on the role of geomagnetic disturbances as a factor determining the intensity of traveling ionospheric disturbances (TIDs). To improve the statistical validity of the data, we have used the based on the new GLOBDET technology method involving a global spatial averaging of disturbance spectra of the total electron content (TEC). To characterize the TID intensity quantitatively, we suggest that a new global index of the degree of disturbance should be used, which is equal to the mean value of the rms variations in TEC within the selected range of spectral periods (of 20-60 min in the present case). It was found that power spectra of daytime TEC variations in the range of 20-60 min periods under quiet conditions have a power-law form, with the slope index k = -2.5. With an increase of the level of magnetic disturbance, there is an increase in total intensity of TIDs, with a concurrent kink of the spectrum caused by an increase in oscillation intensity in ...

Afraimovich, E L; Lesyuta, O S; Ushakov, I I; Yakovets, A F

2000-01-01

384

A method to predict electric field spectra from empirically modeled geomagnetic ULF activity  

NASA Astrophysics Data System (ADS)

A model for prediction of the Earth background electromagnetic field spectra in the ULF range (1 mHz to 10 Hz) is developed. The possibility to model the hourly integrated magnetic wave power spectra with two different mathematical models, a power law or a fourth?order polynomial, is investigated. Spectral properties of 3 months of ground magnetic data show that the temporal evolution of the power law parameters can be modeled based on the hourly planetary magnetic activity, the Kp index. Furthermore, the parameters of the polynomial model are related to the magnetic wave power in two spectral bands within the Pc3 and Pc1 pulsation bands. Empirical models of the magnetic wave power in these bands are developed based on the diurnal variation and the correlation with solar wind velocity of geomagnetic pulsations. Comparison with observations shows that the power law model represents the spectra well for low frequencies. However, the polynomial model based on solar wind velocity provides a better representation for the bulk of the ULF domain with mean errors between 2 and 7 dB, increasing with decreasing frequency. The modeled magnetic wave spectrum and knowledge of the underlying electrical conductivity profile can be used to predict the induced ground electric field spectra. An apparent electric conductivity profile was found via model?based inversion, and the predicted electric wave power is compared to observations from an electrode systems offshore of the test site. The mean error between the observed and predicted electric field amplitudes is 2-7 dB and is consistently lower than the 95% central range of the data set.

Rosenqvist, L.

2013-08-01

385

Pitch angle distributions of electrons at dipolarization sites during geomagnetic activity: THEMIS observations  

NASA Astrophysics Data System (ADS)

Changes in pitch angle distributions of electrons with energies from a few eV to 1 MeV at dipolarization sites in Earth's magnetotail are investigated statistically to determine the extent to which adiabatic acceleration may contribute to these changes. Forty-two dipolarization events from 2008 and 2009 observed by Time History of Events and Macroscale Interactions during Substorms probes covering the inner plasma sheet from 8 RE to 12 RE during geomagnetic activity identified by the AL index are analyzed. The number of observed events with cigar-type distributions (peaks at 0° and 180°) decreases sharply below 1 keV after dipolarization because in many of these events, electron distributions became more isotropized. From above 1 keV to a few tens of keV, however, the observed number of cigar-type events increases after dipolarization and the number of isotropic events decreases. These changes can be related to the ineffectiveness of Fermi acceleration below 1 keV (at those energies, dipolarization time becomes comparable to electron bounce time). Model-calculated pitch angle distributions after dipolarization with the effect of betatron and Fermi acceleration tested indicate that these adiabatic acceleration mechanisms can explain the observed patterns of event number changes over a large range of energies for cigar events and isotropic events. Other factors still need to be considered to assess the observed increase in cigar events around 2 keV. Indeed, preferential directional increase/loss of electron fluxes, which may contribute to the formation of cigar events, was observed. Nonadiabatic processes to accelerate electrons in a parallel direction may also be important for future study.

Wang, Kaiti; Lin, Ching-Huei; Wang, Lu-Yin; Hada, Tohru; Nishimura, Yukitoshi; Turner, Drew L.; Angelopoulos, Vassilis

2014-12-01

386

Relevance vector machines as a tool for forecasting geomagnetic storms during years 1996-2007  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the use of relevance vector machine (RVM) as a learning tool in order to generate 1-h (one hour) ahead forecasts for geomagnetic storms driven by the interaction of the solar wind with the Earth's magnetosphere during the years 1996-2007. This epoch included solar cycle 23 with storms that were both ICME (interplanetary coronal mass ejection) and CIR (corotating interaction region) driven. Merged plasma and magnetic field measurements of the solar wind from the Advanced Composition Explorer (ACE) and WIND satellites located upstream of the Earth's magnetosphere at 1-h cadence were used as inputs to the model. The magnetospheric response to the solar wind driving measured by the disturbance storm time or the Dst index (measured in nT) was used as the output to be forecasted. The model was first tested on previously reported storms in Wu and Lundstedt (1997) and it gave a linear correlation coefficient, ?, of above 90% and prediction efficiency (PE) above 80%. During 1996-2007, several storms (within each year) were chosen as test cases to analyze the forecasting robustness of the model. The top three forecasts per year were analyzed to assess the generalization ability of the model. These included storms with varying intensities ranging from weak (-53.01 nT) to strong (-422.02 nT) and durations (119-445 h). The top RVM forecast in a given year had ? above 85% (87.00-96.85%), PE > 73 % (73.59-93.59%), and a root mean square error (RMSE) ranging from 9.31 to 33.45 nT. A qualitative comparison is made with model forecasts previously reported by Ji et al. (2012). We found that the robustness of the model with regards to fast learning and generating forecasts within acceptable error bounds makes it a very good proposition as a prediction tool (given the solar wind parameters) for space weather monitoring.

Andriyas, T.; Andriyas, S.

2015-04-01

387

Seismo-magnetic multi-point ULF studies before the 2009 L'Aquila earthquake using the South European GeoMagnetic Array  

NASA Astrophysics Data System (ADS)

A strong earthquake (Ml=5.8, Mw=6.3) hit L'Aquila (Central Italy, Abruzzo region, LT=UT+1) on April 6, 2009, 01:32 UT, causing more than 300 deaths. We present a seismo-magnetic analysis of local ULF measurements for the time period one year before the main stroke. As part of the South European GeoMagnetic Array (SEGMA) the evaluated station L'Aquila in closest distance to the epicentre of the main seismic event is ~ 6 km. We consider three further SEGMA stations: Castello Tesino, Ranchio (both Italy) and Nagycenk (Hungary) for comparison and the Kp geomagnetic index to distinguish local- , global- and geomagnetic effects. Further local seismic activities are respected. The instrumentation consists of fluxgate magnetometers with a sampling frequency of 1 Hz. Concerning signal processing the standardized polarization method was applied based on the ratio between the vertical and horizontal power spectral density. A frequency band from 10-100 mHz focused on 10-15 mHz was used during the nighttime period from 22.00 - 02.00 UT. The polarization analysis was introduced and applied for previous seismic events by Hayakawa et al., GRL, 23, 241, 1996.; Molchanov et al., GRL, 19, 1495, 1992.; Prattes et al., NHESS, 2008. A sophisticated method was performed by Ida, et al, NHESS, 2008. With these calculations we expect clearer precursor signatures and they could contribute to EQ forecast. The results are explained using a simple source magnetic dipole model near the EQ focus. The results obtained are explained by the attenuation in the electrical conductive lithosphere.

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

2010-05-01

388

Geomagnetic Paleointensity Recorded In The Khonako-3 Section, Tajikistan  

NASA Astrophysics Data System (ADS)

The geomagnetic intensity recorded in the Khonako-3 loess section (j=38î.02'N, l=70î.03'E), Tajikistan was studied in the upper 18 m of the section including a buried soil complex (BSC-1). Analysis of the inferred curves Js(T), Jrs(T), Jr(H) and Jn(T) showed magnetite to be the main magnetization carrier in the loesses and BSC-1 com- plex. Nearly linear dependences ARM(K) and Jrs(K) indicate along-section invariabil- ity of the average magnetic grain size, which validated the use of the ratio Rnst=Jnt/Jrst for estimating the relative value of Han. The along-section correlation coefficient be- tween the Rnst and Qnt was found to be r = 0.77, i.e. equally reliable estimates of Han can be obtained from both Rnst and Qnt values. Paleomagnetic study of the Khonako- 3 rocks showed that all rocks under study record normal-polarity primary remanence varying in the field direction. A VGP variation at a 8-m depth where low Han values were obtained is similar in the pole wander path to the Mono excursion. The presence of the BSC-1 complex is evidence of variations in the sedimentation rate. The determi- nation of periods of secular variations in Han in various section intervals [Pospelova et al., 1998] showed that these periods as determined from the loess sequence and BSC-1 complex differ by a factor of 1.1. Extension of the BSC-1 interval by 1.1 times brought the section to a uniform sedimentation rate. The field paleointensity recon- struction from data of the resulting section showed that the paleointensity versus time curve correlates with a similar world data curve on a significant level (r = 0.6) in a 35- to 23-kyr interval. Assuming that the Khonako-3 section deposited in a 35-23-kyr interval, the spectra of angular characteristics of the field and Han recorded in the section agree well with the SV spectrum obtained from data of the Yangiyul section and with archaeomagnetic data. Then, the BSC-1 interval of the Khonako-3 section deposited 34 to 32 kyr in the Denekamp deglaciation period; the N. Shackleton time scale analog of the latter is oxygen isotope stage 3.1. Comparison of the Han variation curve as recorded in the Khonako-3 section with the geomagnetic intensity curve con- strained by world data over the last 130 kyr showed that these curves are uncorrelated (r =-0,076).

Pospelova, G.; Pilipenko, O.; Laukhin, S.

389

Long-term variation in the upper atmosphere as seen in the amplitude of the geomagnetic solar quiet daily variation  

NASA Astrophysics Data System (ADS)

It has been well-known that geomagnetic solar quiet (Sq) daily variation is produced by global ionospheric currents flowing in the E-region from middle latitudes to the magnetic equator. These currents are generated by a dynamo process via interaction between the neutral wind and ionospheric plasma in a region of the thermosphere and ionosphere. From the Ohm's equation, the ionospheric currents strongly depend on the ionospheric conductivity, polarization electric field and neutral wind. Then, to investigate the Sq amplitude is essential for understanding the long-term variations in the ionospheric conductivity and neutral wind of the thermosphere and ionosphere. Elias et al. [2010] found that the Sq amplitude tends to increase by 5.4-9.9 % in the middle latitudes from 1961 to 2001. They mentioned that the long-term variation of ionospheric conductivity associated with geomagnetic secular variation mainly determines the Sq trend, but that the rest component is ionospheric conductivity enhancement associated with cooling effects in the thermosphere due to increasing the greenhouse gases. In this talk, we clarify the characteristics of the long-term variation in the Sq amplitude using the long-term observation data of geomagnetic field and neutral wind. These observation data have been provided by the IUGONET (Inter-university Upper atmosphere Global Observation NETwork) project. In the present analysis, we used the F10.7 flux as an indicator of the variation in the solar irradiance in the EUV and UV range, geomagnetic field data with time resolution of 1 hour. The definition of the Sq amplitude is the difference of the H-component between the maximum and minimum per day when the Kp index is less than 4. As a result, the Sq amplitude at all the stations strongly depends on 11-year solar activity, and tends to enhance more during the high activities (19- and 22- solar cycles) than during the low activity (20-solar cycle). The Fourier spectra of the F10.7 flux and Sq amplitude at Guam (13.59N, 144.87E) showed that the common peaks appear at the periods of 5.5, 7,5 and 10.5 years with the coherence of more than 0.9 while the spectrum peaks around 0.5 and 1.0 year appear only in the Sq amplitude. The former peak of the Sq amplitude is due to the solar activity while the latter is a cause of the upper atmosphere variation. In order to minimize the solar activity dependence of the Sq amplitude, we calculated the residual Sq amplitude using a second degree polynomial curve between the F10.7 and Sq amplitude during 1957-2010, and examined the residual Sq field defined as the deviation from the fitting curve. The residual Sq amplitude showed a clear tendency to increase and decrease during the periods of 1957-1992 and 1993-2010, respectively. It should be noted that the residual Sq amplitude around 2010 is almost the same level as that around 1970. In order to verify qualitatively the above signatures, we need to investigate the long-term variation in the ionospheric conductivities calculated with the IRI-2007 and MSIS-00 models.

Shinbori, A.; Koyama, Y.; Hayashi, H.; Nose, M.; Hori, T.; Otsuka, Y.; Tsuda, T.

2011-12-01

390

Trapping boundary and field-line motion during geomagnetic storms.  

NASA Technical Reports Server (NTRS)

Observation that the high-latitude trapping boundary for 20-keV electrons and 100-keV protons became very thin in the early morning hours during two intense substorms. The gradients were too steep to be maintained by drifting particles, so they must have been produced locally over the nightside of the earth. The flux gradient is seen to move at speeds in excess of 100 km/sec. Plasma appears to move away from the tail and around the earth at these high speeds during the sudden expansion phases of the substorms. The rapid plasma motion requires the presence of fluctuating electric fields that sometimes exceed 50 to 100 mV/m at a geomagnetic latitude of 30 deg on the L = 5 field line. These observations fit best into a model that contains two field-aligned sheet currents. The high electric fields that accompany the rapid plasma flow can produce nonadiabatic acceleration of 0.1- to 1-MeV electrons and protons.

Kaufmann, R. L.; Horng, J.-T.; Konradi, A.

1972-01-01

391

Dispersion of meteor trails in the geomagnetic field  

NASA Astrophysics Data System (ADS)

A meteor trail is modeled by a long column of weakly ionized plasma, whose dispersion is controlled by the geomagnetic field and the requirement to maintain effective space charge neutrality. First we consider scattering of a radar signal from an underdense trail and derive an expression for the amplitude of the backscattered signal as a function of time. Then, starting from the basic momentum balance equations for electrons and ions in a partially ionized plasma, we require divergences of ion and electron fluxes to be equal, plus assume equality of the flux components along the magnetic field direction. The analysis is really applicable to a whole range of plasma problems, although we focus upon meteor trails for now. It is found that charged particle densities satisfy a diffusion equation and we obtain an expression for the ambipolar diffusion tensor and expressions for the ambipolar electric field, valid for arbitrary relative orientations of the magnetic field and meteor trail axis. Results are somewhat different from previous analyses in the meteor literature.

Robson, R. E.

2001-02-01

392

Using statistical correlation to compare geomagnetic data sets  

NASA Astrophysics Data System (ADS)

The major features of data curves are often matched, to a first order, by bump and wiggle matching to arrive at an offset between data sets. This poster describes a simple statistical correlation program that has proved useful during this stage by determining the optimal correlation between geomagnetic curves using a variety of fixed and floating windows. Its utility is suggested by the fact that it is simple to run, yet generates meaningful data comparisons, often when data noise precludes the obvious matching of curve features. Data sets can be scaled, smoothed, normalised and standardised, before all possible correlations are carried out between selected overlapping portions of each curve. Best-fit offset curves can then be displayed graphically. The program was used to cross-correlate directional and palaeointensity data from Holocene lake sediments (Stanton et al., submitted) and Holocene lava flows. Some example curve matches are shown, including some that illustrate the potential of this technique when examining particularly sparse data sets. Stanton, T., Snowball, I., Zillén, L. and Wastegård, S., submitted. Detecting potential errors in varve chronology and 14C ages using palaeosecular variation curves, lead pollution history and statistical correlation. Quaternary Geochronology.

Stanton, T.

2009-04-01

393

Wavelet Statistical Analysis of Low-Latitude Geomagnetic Measurements  

NASA Astrophysics Data System (ADS)

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 several senses: the time window for analysis can be drastically reduced if compared to other traditional methods (Fourier, for example) and at the same time allow an almost continuous accompaniment of both amplitude and frequency of signals as time goes by. This advantage brings some possibilities for potentially useful forecasting methods of the type also advanced by our group in previous works (see for example, Papa and Sosman, JASTP, 2008). However, the simultaneous statistical analysis of both time series (in our case amplitude and frequency) is a challenging matter and is in this sense that we have found what we consider our main goal. Some possible trends for future works are advanced.

Papa, A. R.; Akel, A. F.

2009-05-01

394

On the average configuration of the geomagnetic tail  

NASA Technical Reports Server (NTRS)

Over 3000 hours of IMP-6 magnetic field data obtained between 20 and 33 R sub E in the geomagnetic tail have been used in a statistical study of the tail configuration. A distribution of 2.5 minute averages of B sub Z as a function of position across the tail reveals that more flux crosses the equatorial plane near the dawn and dusk flanks than near midnight. The tail field projected in the solar magnetospheric equatorial plane deviates from the X axis due to flaring and solar wind aberration by an angle alpha = -0.9 y sub SM - 1.7 where Y sub SM is in earth radii and alpha is in degrees. After removing these effects the Y component of the tail field is found to depend on interplanetary sector structure. During an away sector the B sub Y component of the tail field is on average 0.5 gamma greater than that during a toward sector, a result that is true in both tail lobes and is independent of location across the tail.

Fairfield, D. H.

1978-01-01

395

Engineered plasma interactions for geomagnetic propulsion of ultra small satellites  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

396

A nonlinear dynamical analogue model of geomagnetic activity  

NASA Technical Reports Server (NTRS)

Consideration is given to the solar wind-magnetosphere interaction within the framework of deterministic nonlinear dynamics. An earlier dripping faucet analog model of the low-dimensional solar wind-magnetosphere system is reviewed, and a plasma physical counterpart to that model is constructed. A Faraday loop in the magnetotail is considered, and the relationship of electric potentials on the loop to changes in the magnetic flux threading the loop is developed. This approach leads to a model of geomagnetic activity which is similar to the earlier mechanical model but described in terms of the geometry and plasma contents of the magnetotail. The model is characterized as an elementary time-dependent global convection model. The convection evolves within a magnetotail shape that varies in a prescribed manner in response to the dynamical evolution of the convection. The result is a nonlinear model capable of exhibiting a transition from regular to chaotic loading and unloading. The model's behavior under steady loading and also some elementary forms of time-dependent loading is discussed.

Klimas, A. J.; Baker, D. N.; Roberts, D. A.; Fairfield, D. H.; Buechner, J.

1992-01-01

397

A power spectrum for the geomagnetic dipole moment  

NASA Astrophysics Data System (ADS)

We use stochastic models for fluctuations in the dipole moment to derive a geomagnetic power spectrum. The theoretical spectrum is represented as a function of frequency f in the general form Af-n with smooth transitions between changes in the exponent n. A flat spectrum (n = 0) at low frequencies changes to n = 2 at intermediate frequencies. We attribute the transition frequency to the decay time of dipole fluctuations. Accounting for correlated noise in the stochastic model introduces another transition from n = 2 to 4, where the transition frequency is set by the correlation time of the noise. Numerical geodynamo models suggest that the correlation time is less than the convective overturn time and may be related to the lifetime of helical eddies. Applying these results to paleomagnetic estimates of the power spectrum yields a correlation time of 100 to 200 yrs. Evidence for a transition between n = 0 and n = 2 in paleomagnetic power spectra is interpreted as a constraint on the electrical conductivity of the core. Additional correlation times in the noise model are expected to produce a transition to n = 6, possibly associated with diffusion of the dipole field through a magnetic boundary layer at the top of the core.

Buffett, Bruce; Matsui, Hiroaki

2015-02-01

398

THE DISCOVERY OF GEOMAGNETICALLY TRAPPED COSMIC-RAY ANTIPROTONS  

SciTech Connect

The existence of a significant flux of antiprotons confined to Earth's magnetosphere has been considered in several theoretical works. These antiparticles are produced in nuclear interactions of energetic cosmic rays with the terrestrial atmosphere and accumulate in the geomagnetic field at altitudes of several hundred kilometers. A contribution from the decay of albedo antineutrons has been hypothesized in analogy to proton production by neutron decay, which constitutes the main source of trapped protons at energies above some tens of MeV. This Letter reports the discovery of an antiproton radiation belt around the Earth. The trapped antiproton energy spectrum in the South Atlantic Anomaly (SAA) region has been measured by the PAMELA experiment for the kinetic energy range 60-750 MeV. A measurement of the atmospheric sub-cutoff antiproton spectrum outside the radiation belts is also reported. PAMELA data show that the magnetospheric antiproton flux in the SAA exceeds the cosmic-ray antiproton flux by three orders of magnitude at the present solar minimum, and exceeds the sub-cutoff antiproton flux outside radiation belts by four orders of magnitude, constituting the most abundant source of antiprotons near the Earth.

Adriani, O. [Department of Physics, University of Florence, I-50019 Sesto Fiorentino, Florence (Italy); Barbarino, G. C. [Department of Physics, University of Naples 'Federico II', I-80126 Naples (Italy); Bazilevskaya, G. A. [Lebedev Physical Institute, RU-119991, Moscow (Russian Federation); Bellotti, R.; Bruno, A.; Cafagna, F. [Department of Physics, University of Bari, I-70126 Bari (Italy); Boezio, M.; Bonvicini, V. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bogomolov, E. A. [Ioffe Physical Technical Institute, RU-194021 St. Petersburg (Russian Federation); Bongi, M.; Bottai, S. [INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Borisov, S.; Casolino, M.; De Pascale, M. P.; De Santis, C. [INFN, Sezione di Rome 'Tor Vergata', I-00133 Rome (Italy); Campana, D.; Carbone, R.; Consiglio, L. [INFN, Sezione di Naples, I-80126 Naples (Italy); Carlson, P. [KTH, Department of Physics, and the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden); Castellini, G., E-mail: alessandro.bruno@ba.infn.it [IFAC, I-50019 Sesto Fiorentino, Florence (Italy)

2011-08-20

399

Study of mass density enhancements at high geomagnetic latitudes  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

400

Geomagnetic secular variations and volcanic pulses in the Siberian traps  

NASA Astrophysics Data System (ADS)

We have studied three volcanic sections of the Siberian traps dated between 251.7 +-0.4 Ma and 251.1 +- 0.3 Ma (Kamo et al., 2003), close to the Permian-Triassic boundary and presently exposed along the valleys of Kotuy and Maymecha rivers (at the northeastern margin of the volcanic field of the Siberian traps). These sections correspond to different time levels and include 24, 43 and 42 flows of basalts and alkaline basalt compositions. We apply the procedure used in Chenet et al. (2008, 2009) based on the analysis of the secular variation fossilized by lava flows to estimate the eruptive sequence of the three sections. It appears that each section can be divided into volcanic pulses and individual flows. The volcanic pulses contain several lava flows which have not recorded the secular variations, suggesting an emplacement in less than ~100 years or less. Moreover, we have compared observed VGP (virtual geomagnetic poles) scatter with this one predicted from statistical model TK03 (Tauxe and Kent, 2004), based on Late Cenozoic data, and made the conclusion about compatibility of our data and this model.

Pavlov, Vladimir; Fluteau, Frederic; Veselovsky, Roman; Fetisova, Anna

2010-05-01

401

Electron precipitation response to geomagnetic pulsations: Riometer revelation  

NASA Astrophysics Data System (ADS)

Electron precipitation modulations by geomagnetic pulsation have been observed in cosmic noise absorption (CNA) as early as 1965 by widebeam riometers (Barcus and Rosenberg, 1965). The first observation of pulsation with high m-number was reported by Kikuchi et al.(1988) em-ploying a scanning narrow-beam riometer to investigate the spatial structure in one dimension with a high resolution. However, the advances in high spatial resolution imaging riometers has provided the ability to observe pulsating cosmic noise absorption with azimuthal wave numbers as high as 380 as well as providing the capability of mapping their structures. These waves are commonly observed during the morning and early afternoon and exhibit eastward propagation. In this presentation a complete generating mechanism for these high m-number waves is dis-cussed as a five step process, beginning with the solar wind as a source for the excitation of dayside magnetospheric cavity modes, mode conversion, energisation of drift-bounce protons by Landau damping, followed by inverse Landau damping as a driving mechanism for the high m number secondary waves that ultimately modulate the electron precipitation. This modulation is observed as pulsations in cosmic noise absorption.

Honary, Farideh; Kavanagh, Andrew

402

Attitude dynamics and control of spacecraft using geomagnetic Lorentz force  

NASA Astrophysics Data System (ADS)

Attitude stabilization of a charged rigid spacecraft in Low Earth Orbit using torques due to Lorentz force in pitch and roll directions is considered. A spacecraft that generates an electrostatic charge on its surface in the Earth's magnetic field will be subject to perturbations from the Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft's orientation. We assume that the spacecraft is moving in the Earth's magnetic field in an elliptical orbit under the effects of gravitational, geomagnetic and Lorentz torques. The magnetic field of the Earth is modeled as a non-tilted dipole. A model incorporating all Lorentz torques as a function of orbital elements has been developed on the basis of electric and magnetic fields. The stability of the spacecraft orientation is investigated both analytically and numerically. The existence and stability of equilibrium positions is investigated for different values of the charge to mass ratio (?*). Stable orbits are identified for various values of ?*. The main parameters for stabilization of the spacecraft are ?* and the difference between the components of the moment of inertia for the spacecraft.

Abdel-Aziz, Yehia A.; Shoaib, Muhammad

2015-01-01

403

Extended study of extreme geoelectric field event scenarios for geomagnetically induced current application  

NASA Astrophysics Data System (ADS)

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

Ngwira, C. M.; Pulkkinen, A.; Wilder, F. D.; Crowley, G.

2012-12-01

404

Proceedings of the XIIIth IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition, and Processing  

USGS Publications Warehouse

The thirteenth biennial International Association of Geomagnetism and Aeronomy (IAGA) Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing was held in the United States for the first time on June 9-18, 2008. Hosted by the U.S. Geological Survey's (USGS) Geomagnetism Program, the workshop's measurement session was held at the Boulder Observatory and the scientific session was held on the campus of the Colorado School of Mines in Golden, Colorado. More than 100 participants came from 36 countries and 6 continents. Preparation for the workshop began when the USGS Geomagnetism Program agreed, at the close of the twelfth workshop in Belsk Poland in 2006, to host the next workshop. Working under the leadership of Alan Berarducci, who served as the chairman of the local organizing committee, and Tim White, who served as co-chairman, preparations began in 2007. The Boulder Observatory was extensively renovated and additional observation piers were installed. Meeting space on the Colorado School of Mines campus was arranged, and considerable planning was devoted to managing the many large and small issues that accompany an international meeting. Without the devoted efforts of both Alan and Tim, other Geomagnetism Program staff, and our partners at the Colorado School of Mines, the workshop simply would not have occurred. We express our thanks to Jill McCarthy, the USGS Central Region Geologic Hazards Team Chief Scientist; Carol A. Finn, the Group Leader of the USGS Geomagnetism Program; the USGS International Office; and Melody Francisco of the Office of Special Programs and Continuing Education of the Colorado School of Mines. We also thank the student employees that the Geomagnetism Program has had over the years and leading up to the time of the workshop. For preparation of the proceedings, thanks go to Eddie and Tim. And, finally, we thank our sponsors, the USGS, IAGA, and the Colorado School of Mines.

Love, Jeffrey J.

2009-01-01

405

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

406

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

NASA Astrophysics Data System (ADS)

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

Rollison, Eric; Moura, John; Lauby, Mark

2011-08-01

407

Features of Men with Anabolic-Androgenic Steroid Dependence: A Comparison With Nondependent AAS Users and With AAS Nonusers  

PubMed Central

Background Anabolic-androgenic steroid (AAS) dependence has been a recognized syndrome for some 20 years, but remains poorly understood. Methods We evaluated three groups of experienced male weightlifters: 1) men reporting no history of AAS use (N = 72); 2) nondependent AAS users reporting no history of AAS dependence (N = 42); and 3) men meeting adapted DSM-IV criteria for current or past AAS dependence (N = 20). We assessed demographic indices, lifetime history of psychiatric disorders by the Structured Clinical Interview for DSM-IV, variables related to AAS use, and results from drug tests of urine and hair. Results Nondependent AAS users showed no significant differences from AAS nonusers on any variable assessed. Dependent AAS users, however, differed substantially from both other groups on many measures. Notably, they reported a more frequent history of conduct disorder than nondependent AAS users (odds ratio [95% CI]: 8.0 [1.7, 38.0]) or AAS nonusers (13.1 [2.8, 60.4]) and a much higher lifetime prevalence of opioid abuse and dependence than either comparison group (odds ratios 6.3 [1.2, 34.5] and 18.6 [3.0, 116.8], respectively). Conclusions Men with AAS dependence, unlike nondependent AAS users or AAS nonusers, showed a distinctive pattern of comorbid psychopathology, overlapping with that of individuals with other forms of substance dependence. AAS dependence showed a particularly strong association with opioid dependence – an observation that recalls recent animal data suggesting similarities in AAS and opioid brain reward mechanisms. Individuals with AAS dependence and individuals with “classical” substance dependence may possibly harbor similar underlying biological and neuropsychological vulnerabilities. PMID:19339124

Kanayama, Gen; Hudson, James I.; Pope, Harrison G.

2009-01-01

408

AA Data Company Above the Limit Inc.  

E-print Network

Instruments Toro Company Toyota Union Pacific Railroad Unisys Verizon Walt Disney Imagineering XeroxRegional Companies AA Data Company Above the Limit Inc. Acorn Technology Adamson Analytical Labo Portland Ce- ment Company Campbell Concrete of California Centrum Labs Cadence Design Systems Cryoquip

409

Common vnmr commands aa--abort acquisition  

E-print Network

Common vnmr commands aa--abort acquisition ai--absolute intensity mode aph--automatic phase correction at--acquisition time (sec) axis--scale units: axis='h' or axis='p' bc--baseline correction bs--plot scale pw--pulse width pwd--present working directory ra--resume acquisition (stopped by sa) rl

Stoltz, Brian M.

410

DDEE LLAA TTEERRRREE AA LL''AALLIIMMEENNTT  

E-print Network

1 DDEE LLAA TTEERRRREE AA LL''AALLIIMMEENNTT :: EETTAATT DDEESS LLIIEEUUXX DDEESS de Lascaux : http://www.droit-aliments-terre.eu/). Les recherches menant aux présents résultats ont aujourdhui avec une urgence nouvelle eu égard aux multiples défis auxquels ils doivent faire face. Limage qui

Boyer, Edmond

411

Indexing Consistency and Quality.  

ERIC Educational Resources Information Center

A measure of indexing consistency is developed based on the concept of 'fuzzy sets'. It assigns a higher consistency value if indexers agree on the more important terms than if they agree on less important terms. Measures of the quality of an indexer's work and exhaustivity of indexing are also proposed. Experimental data on indexing consistency…

Zunde, Pranas; Dexter, Margaret E.

412

Natural History and Outcome in Systemic AA Amyloidosis  

Microsoft Academic Search

BACKGROUND Deposition of amyloid fibrils derived from circulating acute-phase reactant serum amy- loid A protein (SAA) causes systemic AA amyloidosis, a serious complication of many chronic inflammatory disorders. Little is known about the natural history of AA amy- loidosis or its response to treatment. METHODS We evaluated clinical features, organ function, and survival among 374 patients with AA amyloidosis who

Helen J. Lachmann; Hugh J. B. Goodman; Janet A. Gilbertson; J. Ruth Gallimore; Caroline A. Sabin; Julian D. Gillmore; Philip N. Hawkins

2007-01-01

413

AAS-DDA, Philadelphia April 28-May 1 2014  

E-print Network

AAS-DDA, Philadelphia April 28-May 1 2014 A few points on the dynamical evolution of the young solar system Renu Malhotra The University of Arizona #12;AAS-DDA, Philadelphia April 28-May 1 2014 A few - planetesimal-driven migration Renu Malhotra The University of Arizona #12;AAS-DDA, Philadelphia April 28-May 1

Malhotra, Renu

414

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.

415

Nomadic Communications AA 2010/11 Vehicular Ad Hoc Networks  

E-print Network

Communications' AA10-11 A digression on Fatalities (EU 2005) Main Causes and driving errors: 95% of all road, Sept. 9, 2007 Renato Lo Cigno `Nomadic Communications' AA10-11 A digression on Fatalities (EU 2005) #12Nomadic Communications AA 2010/11 Vehicular Ad Hoc Networks 90% of this material is reproduced

Lo Cigno, Renato Antonio

416

Nomadic Communications AA 2009/10 Vehicular Ad Hoc Networks  

E-print Network

Communications' AA07-08 A digression on Fatalities (EU 2005) Main Causes and driving errors: 95% of all road, Sept. 9, 2007 Renato Lo Cigno `Nomadic Communications' AA07-08 A digression on Fatalities (EU 2005) #12Nomadic Communications AA 2009/10 Vehicular Ad Hoc Networks 90% of this material is reproduced

Lo Cigno, Renato Antonio

417

Nomadic Communications AA 2010/11 Vehicular Ad Hoc Networks  

E-print Network

Nomadic Communications AA 2010/11 Vehicular Ad Hoc Networks 90% of this material is reproduced at ACM MobiCom/MobiHoc 2007, Montreal, Canada, Sept. 9, 2007 Renato Lo Cigno `Nomadic Communications' AA, Sept. 9, 2007 Renato Lo Cigno `Nomadic Communications' AA10-11 Agenda 1. Applications and recent

Lo Cigno, Renato Antonio

418

Nomadic Communications AA 2009/10 Vehicular Ad Hoc Networks  

E-print Network

Nomadic Communications AA 2009/10 Vehicular Ad Hoc Networks 90% of this material is reproduced at ACM MobiCom/MobiHoc 2007, Montreal, Canada, Sept. 9, 2007 Renato Lo Cigno `Nomadic Communications' AA, Sept. 9, 2007 Renato Lo Cigno `Nomadic Communications' AA07-08 Agenda 1. Applications and recent

Lo Cigno, Renato Antonio

419

Index des mots-cls Keywords index  

E-print Network

Index des mots-clés Keywords index A Abies, 823 Abies alba, 265 acacia, 93 Acacia cyanophylla Lindl., 335 Acacia mearnsii De Wild., 833 acclimation, 19 AFLP, 627 AFLP, SSR, EST markers, 637 Agrobacterium

Boyer, Edmond

420

Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes  

NASA Astrophysics Data System (ADS)

Large-scale TEC perturbations/enhancements observed during the day sectors of major storm periods, 12-13 February 2000, 23 September 1999, 29 October 2003, and 21 November 2003, were studied using a high resolution GPS network over Japan. TEC enhancements described in the present study have large magnitudes (?25×1016 electrons/m2) compared to the quiet-time values and long periods (?120 min). The sequential manner of development and the propagation of these perturbations show that they are initiated at the northern region and propagate towards the southern region of Japan, with velocities >350 m/s. On 12 February 2000, remarkably high values of TEC and background content are observed at the southern region, compared to the north, because of the poleward expansion of the equatorial anomaly crest, which is characterized by strong latitudinal gradients near 35° N (26° N geomagnetically). When the TEC enhancements, initiating at the north, propagate through the region 39-34° N (30-25° N geomagnetically), they undergo transitions characterized by a severe decrease in amplitude of TEC enhancements. This may be due to their interaction with the higher background content of the expanded anomaly crest. However, at the low-latitude region, below 34° N, an increase in TEC is manifested as an enhanced ionization pattern (EIP). This could be due to the prompt penetration of the eastward electric field, which is evident from high values of the southward Interplanetary Magnetic Field component (IMF Bz) and AE index. The TEC perturbations observed on the other storm days also exhibit similar transitions, characterized by a decreasing magnitude of the perturbation component, at the region around 39-34° N. In addition to this, on